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Primary production is an important driver of marine carbon storage. Besides the major nutrient elements nitrogen, phosphorus, and silicon, primary production also depends on the availability of nutrient-type metals (e.g., Cu, Fe, Mo) and the absence of toxicologically relevant metals (e.g., Ni, Pb). Especially in coastal oceans, carbon storage and export to the open ocean is highly variable and influenced by anthropogenic eutrophication and pollution. To model future changes in coastal carbon storage processes, a solid baseline of nutrient and metal concentrations is crucial. The North Sea is an important shelf sea, influenced by riverine, atmospheric, Baltic Sea, and North Atlantic inputs. We measured the concentrations of dissolved nutrients (NH 4 + , NO 3 - , PO 4 3- , and SiO 4 4- ) and 26 metals in 337 water samples from various depths within the entire North Sea and Skagerrak. A principal component analysis enabled us to categorize the analytes into three groups according to their predominant behavior: tracers for seawater (e.g., Mo, U, V), recycling (e.g., NO 3 - , PO 4 3- , SiO 4 4- ), and riverine or anthropogenic input (e.g., Ni, Cu, Gd). The results further indicate an increasing P-limitation and increasing anthropogenic gadolinium input into the German Bight., (© 2024. The Author(s).)

Cell components soluble in neutral detergent are a diverse group, both compositionally and nutritionally. The present study aimed to evaluate production responses, behavior (eating, ruminating, and idling), and nitrogen balance of dairy goats fed different ratios of neutral detergent-soluble carbohydrate fractions. Five multiparous Alpine does with mean ± SD initial body mass of 49.5 ± 7.9 kg and 60 days of lactation were randomly assigned in a 5 × 5 Latin square design. The treatments were the ratios of starch (starch associated with soluble sugar [StSS]) to neutral detergent-soluble fiber (NDSF) (StSS:NDSF): 0.89, 1.05, 1.24, 1.73, and 2.92. No effect was observed (P > 0.05) of StSS:NDSF on the intakes of neutral detergent fiber (NDF) and NDSC. However, DM intake showed a quadratic behavior (P = 0.049). The ingestive behavior was affected by StSS:NDSF linearly increased (P = 0.002) the feeding efficiency. The increase in StSS:NDSF caused a linear increase in fecal (P = 0.011), urinary (P < 0.001), and milk nitrogen excretion (P = 0.024). The increase in StSS:NDSF affected (P = 0.048) milk yield and net energy lactation (P = 0.036). In conclusion, dairy goats experience reduced dry matter intake and milk yield when subjected to high-NDSC diets, specifically those above 1.24 StSS:NDSF ratio. Elevated NDSC levels in the diets lead to decreased feeding time, whereas rumination remains unaffected. Nitrogen losses in goats increase linearly with high-NDSC diets, and a significant impact on nitrogen balance., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Soil fertility (SF) is a crucial factor that directly impacts the performance and quality of crop production. To investigate the SF status in agricultural lands of winter wheat in Khuzestan province, 811 samples were collected from the soil surface (0-25 cm). Eleven soil properties, i.e., electrical conductivity (EC), soil organic carbon (SOC), total nitrogen (TN), calcium carbonate equivalent (CCE), available phosphorus (P av ), exchangeable potassium (K ex ), iron (Fe), copper (Cu), zinc (Zn), manganese (Mn), and soil pH, were measured in the samples. The Nutrient Index Value (NIV) was calculated based on wheat nutritional requirements. The results indicated that 100%, 93%, and 74% of the study areas for CCE, pH, and EC fell into the low, moderate, and moderate to high NIV classes, respectively. Also, 25% of the area is classified as low fertility (NIV < 1.67), 75% falls under medium fertility (1.67 < NIV value < 2.33), and none in high fertility (NIV value > 2.33). Assessment of the mean wheat yield (AWY) and its comparison with NIV showed that the highest yield was in the Ramhormoz region (5200 kg.ha -1 ), while the lowest yield was in the Hendijan region (3000 kg.ha -1 ) with the lowest EC rate in the study area. Elevated levels of salinity and CCE in soils had the most negative impact on irrigated WY, while P av , TN, and Mn availability showed significant effects on crop production. Therefore, implementing SF management practices is essential for both quantitative and qualitative improvement in irrigated wheat production in Khuzestan province., (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Forest-savanna transition zones of West Africa are uniquely characterized by forest groves, forest patches, or forest islands, the importance of which for sustainable resource management and their potential for carbon sequestration and nutrient cycling is often underrated. Our study conducted a comparative analysis of the soil organic carbon and nutrient characteristics of the Anogeissus groves in the old Opara forest reserve and their adjoining arable lands. We established 30 sampling frames of 100 m × 100 m plots with 15 frames per land use type. For each sampling frame, six observation points were randomly selected, and composite soil samples were collected at soil depths of 0-20 cm and 20-50 cm per observation point. Our results showed Anogeissus groves and their adjoining arable lands to exist on similar landscapes while the groves have enriched soil morphological characteristics (e.g., soil color), higher soil organic carbon (SOC), and better nutrient characteristics. There were strong positive relationships between SOC, effective cation exchange capacity, total nitrogen, calcium, magnesium and calcium, zinc, electrical conductivity, and copper. The significant soil organic matter accumulation in the groves accounts for the overall improved soil characteristics over the adjoining arable lands. Preserving the groves and similar African ecosystems may be important in climate regulation, resources and biodiversity conservation, and ethnopharmacology for rural communities. Thus, a question arises: should more land be set aside for ecological conservation or for agricultural productivity?, (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

This study evaluated three continuous grazing systems: Brachiaria Brizantha, Clitoria ternatea and naturalized pastures, complemented with commercial concentrate and C. ternatea silage on milk yield, nutrient use and enteric methane (CH 4 ) emissions. Nine multiparous cows of local Zebu breeds, with an average weight of 448 ± 87 kg, were used. The chemical composition of the food was determined. Live weight, milk production, and quality were assessed. Furthermore, serum urea, urea nitrogen, creatinine and glucose in blood were monitored, and nitrogen use efficiency were calculated. Enteric methane (CH 4 ) emissions were estimated using Tier-2 methodology. A 3 × 3 latin square experimental design was applied. The grazing systems of B. brizantha and C. ternatea had the greater live weights of 465.8 and 453.3 kg/cow, although the latter is similar to naturalized pasture. Milk production and quality were not affected by grazing system, with the exception of the non-fat solids, where the C. ternatea system was lower (102.2 g/kg) than the other grazing systems. The crude protein and N intake, and N excretion in feces and urine were lower in naturalized pasture systems (1139.0 g/day). N outputs in milk was high in the C. ternatea system (56.3 g/cow/day). The naturalized pastures systems showed the better feed use efficiency (25.7%) compared to others. Serum urea and blood urea nitrogen were greater in B. brizantha followed by C. ternatea. Enteric CH 4 emissions were indifferent among grazing systems when expressed as a percentage of greenhouse gases (7.1%). In conclusion, the grazing C. ternatea supplemented with commercial concentrate and C. ternatea silage maintains milk production and quality, reduced cow/day emissions (by 2.5%) and lowered energy losses as methane., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Estimating the pollution loads in the Tuhai River is essential for developing a water quality standard scheme. This study utilized the improved output coefficient method to estimate the total pollution loads in the river basin while analyzing the influencing factors based on the STIRPAT (Stochastic Impacts by Regression on Population, Affluence, and Technology) model. Findings indicated that the projected point source pollution loads for total phosphorus (TP), chemical oxygen demand (COD), and ammonia nitrogen (AN) would amount to 3937.22 ton, 335,523.25 ton, and 13,946.92 ton in 2021, respectively. Among these, COD pollution would pose the greatest concern. The primary contributors to the pollution loads were rural scattered life, large-scale livestock and poultry breeding, and surface runoff. Per capita GDP emerged as the most influential factor affecting the pollution loads, followed by cultivated land area, while the urbanization rate demonstrated the least impact., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Microalgae have emerged as potential candidates for biomass production and pollutant removal. However, expensive biomass harvesting, insufficient biomass productivity, and low energy intensity limit the large-scale production of microalgae. To break through these bottlenecks, a novel technology of immobilized microalgae culture coupled with wastewater treatment has received increasing attention in recent years. In this review, the characteristics of two immobilized microalgae culture technologies are first presented and then their mechanisms are discussed in terms of biofilm formation theories, including thermodynamic theory, Derjaguin-Landau-Verwei-Overbeek theory (DLVO) and its extended theory (xDLVO), as well as ionic cross-linking mechanisms in the process of microalgae encapsulated in alginate. The main factors (algal strains, carriers, and culture conditions) affecting the growth of microalgae are also discussed. It is also summarized that immobilized microalgae show considerable potential for nitrogen and phosphorus removal, heavy metal removal, pesticide and antibiotic removal in wastewater treatment. The role of bacteria in the cultivation of microalgae by immobilization techniques and their application in wastewater treatment are clarified. This is economically feasible and technically superior. The problems and challenges faced by immobilized microalgae are finally presented., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Improving the adsorption performance of wetland fillers is of great significance for enhancing pollutant removal in constructed wetlands. Currently, limited by complex preparation processes and high costs, large numbers of high adsorption fillers studied in lab are difficult to be applied in practical engineering. In this study, a newly low-cost and efficient phosphorus removal composite wetland filler (CFB) is prepared by using industrial and agriculture waste (steel slag and oyster shells) and natural ore (volcanic rock) as raw materials. The results show that phosphorus removal efficiency was largely enhanced by synergistic effects of steel slag, oyster shells, and volcanic rock, and it was mainly influenced by the proportion of each component of CFB. Based on the fitting of the classical isothermal equation, the adsorption capacity of CFB is 18.339 mg/g. The adsorption of phosphorus by CFB is endothermic and spontaneous, and there are heterogeneous surfaces and multi-layer adsorption processes, as well as pH value and temperature, are free from the influence on CFB phosphorus removal. During the practical wastewater application experiments, the phosphorus removal rate of the CFB-filled constructed wetland apparatus (CW-A) can reach 94.89% and is free from the influence on the removal of other pollutants (COD, TN, and NH 3 -N) by the system. Overall, the prepared CFB is of excellent decontamination effect, an extremely simple preparation process, low cost, and sound practical engineering application potential, providing new ideas and approaches for enhancing the phosphorus removal capacity and waste resource utilization of constructed wetland systems., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Stormflow runoff is an important non-point source of pollution in drinking water reservoirs. Storm runoff is usually very turbid and contains a high concentration of organic matter, therefore affecting water quality when it enters reservoirs. In order to investigate the impact of storm runoff on spatial-temporal variation and stratification of water quality during this rainstorm event, the inflow process of the storm runoff was studied through a combination of field investigation and simulation using the Delft3D-Flow model. Water samples were collected from Biliuhe Reservoir at four different periods: before storm runoff, storm runoff flood peak period, 1 week after storm runoff, and 5 weeks after storm runoff. The results showed that the input of storm runoff resulted in a significant increase in the nitrogen (N) and phosphorus (P) in the reservoir water, especially in the reservoir entrance. The concentrations of total nitrogen (TN) and total phosphorus (TP) gradually decreased after the flood peak period; however, the average concentrations of TN and TP in the entire reservoir remained higher than those before the storm runoff levels for an extended duration. The storm runoff will greatly contribute to the contamination of water quality in a reservoir, and the water quality cannot be quickly restored by self-purification in the short term. During the flood peak period, under the influence of density current, the electrical conductivity (EC) and turbidity increased significantly in the water depth of 10-15 m, so that the reservoir water had obvious stratification between 10 and 15 m. The form of pollutants in storm runoff was mostly in particle phosphorus. Total particulate phosphorus (TPP) concentration was 0.015 ± 0.011 mg/L, accounting for 44.12% of total phosphorus (TP) concentration in storm runoff flood peak period. The process of a rainstorm caused runoff, which carried high levels of turbidity, particulate phosphorus, and organic matter. The storm runoff disrupts the stratification of the reservoir water. In terms of vertical distribution, the turbidity in the reservoir area increased to 73.75 NTU. Therefore, the occurrence of significant turbidity density flow in the reservoir is frequently accompanied by intense rainfall events. Gaining insights into the impact of storm runoff on the vertical distribution of reservoir turbidity can help managers in selecting an appropriate inlet height to mitigate high turbidity outflow., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Cold regions are particularly vulnerable to climate change. Thus, evaluating the response of water quality evolution to climate change in cold regions is vital for formulating adaptive countermeasures for pollution control under changing climatic conditions. Taking the Songhua River Basin (SRB) in Northeast China as the target area, we designed a water-heat-nitrogen coupled model based on the principle of water and energy transfer and nitrogen cycle processes model (WEP-N) in cold regions. The impact of climate change on pollution load and water quality was analyzed during the freezing, thawing, and non-freeze-thaw periods by taking the sudden change point (1998) of precipitation and runoff evolution in the SRB as the cut-off. The ammonia nitrogen load at Jiamusi station, the outlet control station in the SRB, was decreased by 1502.9 t in the change period (1999-2018) over the base period (1956-1998), with a - 9.2% decrease due to climate change. Compared to the ammonia nitrogen load during the base period, the ammonia nitrogen load decreased by - 171.3, - 506.9, and - 824.8 t during the freezing, thawing, and non-freeze-thaw periods, respectively, while the coefficient of variation showed an increasing trend during three periods, especially during the freezing and thawing periods. However, the water quality changes differed among periods owing to varying runoff during the year. Meanwhile, increasing runoff and decreasing ammonia nitrogen load improved water quality at Jiamusi station during the freezing period. During the thawing and non-freeze-thaw period, the water quality deteriorated due to the decrease in runoff more than the decrease in ammonia nitrogen load. Hence, the impact of climate change on water quality during thawing and non-freeze-thaw periods should be monitored to potentially offset the human influence on pollution control. The difference in the rate of change of the proportion of Class IV water between the two models with or without the soil freeze-thaw mechanism was 15.9%. The result shows that the application of a model that does not consider the freeze-thaw mechanism might slightly exaggerate the impact of climate change on water quality., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Constructed wetlands (CWs) provide a low-cost, effective solution for domestic wastewater treatment in developing nations compared to costly traditional wastewater systems. Biochar which is an organic material created by pyrolysis offers straightforward, affordable methods for treating wastewater and lowering carbon footprint by acting as a substrate in CWs. Batch mode biochar-amended subsurface flow (SSF) CWs planted with Eclipta alba (L) with a hydraulic retention time (HRT) of 3 days were used for the treatment of rural domestic wastewater in the present investigation. Two control CWs, without plants (C1) and with plants (C2), and five different amendments of biochar 5% (B5), 10% (B10), 15% (B15), 20% (B20) and 25% (B25) in ratio with soil were set up to check the treatment efficiency of CWs. Removal efficiency (RE%) of the CWs for parameters namely chemical oxygen demand (COD), biochemical oxygen demand (BOD), phosphate (PO 4 2- ), sulphate (SO 4 2- ), nitrate (NO 3 - ) and total Kjeldhal nitrogen (TKN) was determined using standard methods. Removal efficiency of 93%, 91%, 74% and 77% was observed for BOD, COD, nitrate and sulphate, respectively, in the B25 amendment at HRT 72 h. The highest removal of TKN (67%) was also observed in the B25 amendment at HRT of 72 h. No stable trend for the removal of phosphates was found during the study, and maximum removal was observed at HRT 48 h; afterward, phosphate was slightly inclined with the increasing HRT. The findings of one-way ANOVA using Tukey's test show significant variations (p < 0.05) in the removal efficiencies of pollutants after 72 h between two controls (C1 and C2) and various biochar amendments in CWs, indicating a significant role of the wetland plants and concentration of the biochar as substrate. Biochar shows a positive impact on the removal of organic pollutants and nitrates. Hence, biochar-amended CWs can be a sustainable way of treating rural domestic wastewater., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The historical impacts of eutrophication processes were investigated in six subtropical reservoirs (São Paulo, Brazil) using a paleolimnological approach. We questioned whether the levels of pigment indicators of algal biomass could provide information about trophic increase and whether carotenoid pigments could offer additional insights. The following proxies were employed: organic matter, total phosphorus, total nitrogen, photosynthetic pigments (by high-performance liquid chromatography), sedimentation rates, and geochronology (by 210 Pb technique). Principal component analysis indicated a gradient of eutrophication. In eutrophic reservoirs (e.g., Rio Grande and Salto Grande), levels of lutein and zeaxanthin increased over time, suggesting growth of Chlorophyta and Cyanobacteria. These pigments were significantly associated with algal biomass, reflecting their participation in phytoplankton composition. In mesotrophic reservoirs, Broa and Itupararanga, increases and significative linear correlations (r > 0.70) between pigments and nutrients are mainly linked to agricultural and urban activities. In the oligotrophic reservoir Igaratá, lower pigment and nutrient levels reflected lesser human impact and good water quality. This study underscores eutrophication's complexity across subtropical reservoirs. Photosynthetic pigments associated with specific algal groups were informative, especially when correlated with nutrient data. The trophic increase, notably in the 1990s, may have been influenced by neoliberal policies. Integrated pigment and geochemical analysis offers a more precise understanding of eutrophication changes and their ties to human factors. Such research can aid environmental monitoring and sustainable policy development., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Herbicides are known to affect the soil nitrogen cycle by shaping soil microorganisms. However, it is not clear how herbicides regulate diverse transformation processes of soil nitrogen cycling by altering rhizosphere microorganisms, subsequently influencing the feedback to plant nitrogen metabolism. Here, we investigated how imazethapyr (IM) enantiomers drive plant-soil feedback on nitrogen metabolism by altering the rhizosphere microorganisms. The results indicated that (R)- and (S)-IM significantly changed the composition and structure rhizosphere microbiome with enantioselectivity and functional changes in microbial communities were associated with soil nitrogen circulation. The determination of nitrogen-cycling functional genes further supported the above findings. The results revealed that (R)- and (S)-IM could change the abundance of nitrogen-cycling functional genes by changing specific bacteria abundances, such as Bacteroidetes, Proteobacteria, and Acidobacteria, thus resulting in diverse nitrogen transformation processes. The alternation of nitrogen transformation processes indicated (R)-IM exhibited a more notable tendency to form a nitrogen cycling pattern with lower energy cost and higher nitrogen retention than (S)-IM. Sterilization experiments demonstrated changes in soil nitrogen cycling drive plant nitrogen metabolism and rhizosphere microorganisms are responsible for the above process of plant-soil feedback for nitrogen metabolism. Under IM enantiomer treatments, rhizosphere microorganisms might stimulate glutamate synthesis by promoting NH 4 + uptake and glutamine-glutamate synthesis cycling in roots, thus contributing to positive feedback, with (R)-IM treatments showing more pronounced positive feedback on nitrogen metabolism than (S)-IM treatments. Our results provide theoretical support for determining the mechanism by which IM enantiomers drive plant-soil nitrogen metabolism by changing the rhizosphere microbial communities., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Utilizing engineered wetlands for the cultivation of vegetables can help to overcome the problems of water and food scarcity. These wetlands are primarily designed for wastewater treatment, and their efficiency and effectiveness can be improved by selecting an appropriate substrate. To investigate the potential for nutrient and microbial removal, the Abelmoschus esculentus, Solanum melongena, and Capsicum annuum L. plants were selected to grow in a hybrid constructed wetland (CW) under natural conditions. The removal efficiency of the A. esculentus, S. melongena, and C. annuum L. in the CW system varied between 59.8 to 68.5% for total phosphorous (TP), 40.3 to 53.1% for ammonium (NH 4 + ), and 33.6 to 45.1% for total nitrogen (TN). The influent sample contained multiple pathogenic bacteria, including Alcaligenes faecalis, Staphylococcus aureus, and Escherichia coli, with Capsicum annuum exhibiting a positive association with 7 of the 11 detected species, whereas microbial removal efficiency was notably higher in the S. melongena bed, potentially attributed to temperature variations and plant-facilitated oxygen release rates. While utilizing constructed wetlands for vegetable cultivation holds promising potential to address the disparity between water and food supply and yield various environmental, economic, and social benefits, it is crucial to note that the wastewater source may contain heavy metals, posing a risk of their transmission to humans through the food chain., (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Increases in fluxes of nitrogen (N) and phosphorus (P) in the environment have led to negative impacts affecting drinking water, eutrophication, harmful algal blooms, climate change, and biodiversity loss. Because of the importance, scale, and complexity of these issues, it may be useful to consider methods for prioritizing nutrient research in representative drainage basins within a regional or national context. Two systematic, quantitative approaches were developed to (1) identify basins that geospatial data suggest are most impacted by nutrients and (2) identify basins that have the most variability in factors affecting nutrient sources and transport in order to prioritize basins for studies that seek to understand the key drivers of nutrient impacts. The "impact" approach relied on geospatial variables representing surface-water and groundwater nutrient concentrations, sources of N and P, and potential impacts on receptors (i.e., ecosystems and human health). The "variability" approach relied on geospatial variables representing surface-water nutrient concentrations, factors affecting sources and transport of nutrients, model accuracy, and potential receptor impacts. One hundred and sixty-three drainage basins throughout the contiguous United States were ranked nationally and within 18 hydrologic regions. Nationally, the top-ranked basins from the impact approach were concentrated in the Midwest, while those from the variability approach were dispersed across the nation. Regionally, the top-ranked basin selected by the two approaches differed in 15 of the 18 regions, with top-ranked basins selected by the variability approach having lower minimum concentrations and larger ranges in concentrations than top-ranked basins selected by the impact approach. The highest ranked basins identified using the variability approach may have advantages for exploring how landscape factors affect surface-water quality and how surface-water quality may affect ecosystems. In contrast, the impact approach prioritized basins in terms of human development and nutrient concentrations in both surface water and groundwater, thereby targeting areas where actions to reduce nutrient concentrations could have the largest effect on improving water availability and reducing ecosystem impacts., (© 2024. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

As the main supply source of lakes, the water quality of the rivers entering the lakes directly determines the water safety and sustainable development of the lakes. Human activities are the direct cause of changes in the water quality of rivers entering lakes, and land use intensity is the direct manifestation of human activities on the land surface. Although significant progress has been made in studying the relationship between land use changes and water quality in lakes, there is still a lack of research on exploring the relationship between land use intensity and water quality at multiple scales, especially in comparative studies of different pollution source areas. To address this problem, this study used Pearson's correlation analysis and land use intensity index method to explore the response relationship between river water quality and land use intensity at different spatial and temporal scales and different pollution source areas using three lakes in central Yunnan as examples. The results showed that land use intensity was generally positively correlated with water quality, but the response relationship between land use intensity and different water quality indicators was significantly different at different scales and for different pollution source areas. Compared to non-urban areas, the impact of land use intensity on water quality is more significant in urban areas. Compared to the rainy season, the correlation between CODNa, TP, and NH 3 -N values and land use intensity is stronger during the dry season, while the correlation between COD, TN, and land use intensity is weaker during the dry season. When viewed at different scales, different water quality indicators have different scale effects, but overall, the larger the scale, the stronger the correlation. Therefore, in the work of lake water environmental governance, it is necessary to consider comprehensively from multiple scales and perspectives and adopt measures that are more suitable for regional water pollution prevention and control., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Yangcheng Lake, a typical fishery lake in the middle and lower reaches of the Yangtze River, is threatened by eutrophication. As the main performers of biogeochemical cycles, microorganisms affect the ecological stability of the lake. To study the structural characteristics of the microbial community in Yangcheng Lake and rivers entering Yangcheng Lake and the response relationship with environmental factors, the microbial community was categorized based on the contour of Yangcheng Lake, the major rivers entering Yangcheng Lake, and the pollution sources. The distribution characteristics of seven physicochemical indices were analyzed, including total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), water temperature (WT), pH, dissolved oxygen (DO), and ratio of total nitrogen to total phosphorus (TN/TP). Characterization of microbial community structure based on 16S rRNA high-flux sequencing technology and ANOSIM analysis were used to explore the differences in the relative abundance of microorganisms at each sampling point in the lake and rivers, and redundancy analysis (RDA) was used to analyze the relationship between the microbial community and physicochemical factors. The results showed that the dominant phyla, genera of microorganisms, and the total number of OTUs in the lake and rivers were similar. The dominant phyla included Proteobacteria, Actinobacteria, Bacteroidetes, Cyanobacteria, and Verrucomicrobia; the dominant genera included the hgcI clade, CL500-29 marine group, Microcystis PCC-7914, Chloroplast&#95;norank, Clade III&#95;norank, and Flavobacterium. ANOSIM analyses revealed that the microbial community of Yangcheng Lake exhibited an association with geographical space, while the microbial community in the rivers that was linked to the type of pollution source. Redundancy analysis (RDA) indicated that dissolved oxygen (DO), total nitrogen (TN), and pH were significantly correlated with the dominant phyla in Yangcheng Lake (p < 0.05), while total nitrogen (TN), water temperature(WT), and the ratio of total nitrogen to total phosphorus (TN/TP) were significantly related with the dominant genera in Yangcheng Lake (p < 0.05). Total nitrogen (TN) was also significantly linked to the dominant phyla and genera of the tributaries (p < 0.05). Despite the structural similarities in microbial communities between Yangcheng Lake and its inflowing rivers, environmental factors demonstrated significant associations with these communities, providing crucial data support for pollution prevention and the ecological restoration of Yangcheng Lake., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

In recent years, the total nitrogen concentration in Taihu Lake has decreased significantly. Denitrification, as the main nitrogen removal process, is the key reason for the decrease. Here, the denitrification parameter values in the Environmental Fluid Dynamic Code (EFDC) model were calculated based on isotope-labeled denitrification experiment instead of selecting the recommended values directly. This study further focused on EFDC denitrification parameter derivation with an experimental denitrification rate (D tot ) to reduce simulation errors. According to the EFDC nitrate deposition flux mechanism, the conversion equation between the denitrification rate of the first sediment layer ([Formula: see text]) in EFDC and D tot was successfully derived. The results revealed a linear correlation between [Formula: see text] and (D tot ) 1/2 . The [Formula: see text] values of sampling points ranged from 0.25 to 0.27 m·day -1 , within the range of model parameters. After substituting [Formula: see text] into the Taihu Lake EFDC model, the average percentage bias and determination coefficient of total nitrogen were 16.25% and 0.87, respectively. The average total nitrogen concentration reduction caused by denitrification at water quality calibration points ranged from 0.027 to 0.305 mg·L -1 ., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

In the effort to identify sustainable sludge management options, pilot-scale sludge treatment reed beds (STRBs) were tested and assessed in the Sultanate of Oman in the first integrated experimental study of this nature-based solution in the Middle East region. A total of 18 pilot STRB units were established and monitored for almost 2 years; half were planted with native Phragmites australis reed species, and half served as unplanted control units. Employing a randomized complete block design, the study examined varying sludge loading rates (SLR) of 75, 100, and 125 kg/m 2 /year. Results underscored the effectiveness of STRBs in reducing the sludge volume, with observed reductions reaching 98.0% of the applied sludge volume, particularly prominent in the SLR75 units. During the final resting phase, the STRBs showed slightly higher concentrations of total Kjeldahl nitrogen (TKN) and total phosphorus (TP) compared to the unplanted beds, while maintaining concentrations lower than those of the applied activated sludge. Furthermore, heavy metal concentrations were consistently diminished in the STRBs compared to the unplanted beds, aligning with the established national and international standards for sludge reuse in agricultural contexts. The results of this study provide the first valuable insight into the potential of STRBs as an effective, sustainable, and climatically suitable approach for sludge dewatering. Specifically, an SLR of 100 kg/m 2 /year is proposed as an optimum loading rate for the hot and arid Middle East climate. This study advances our understanding of STRBs as a pivotal component in the realm of arid-region sludge treatment, shedding light on their capacity to facilitate enhanced dewatering, mineralization, and nutrient removal, thereby contributing to the broader discourse on sustainable waste management practices., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The grey water footprint (GWF) is an advanced index linking pollution load and water resources. However, the existing agriculture-related GWF was developed based on hydrological processes, which limits its role in watershed water pollution level (WPL) measurements. The main scope of this study is to calculate GWF and WPL based on runoff, total nitrogen (TN), and total phosphorus (TP) observations in the Hujiashan Watershed of China's Yangtze River Basin. Partial least squares structural equation modeling (PLS-SEM) was utilized to explore the impact pathways of environmental features on GWF and WPL. On this basis, propose measures for the management of this agricultural watershed. The results showed that the TN concentration had a V-shaped trend in 2008-2015, while the TP gradually decreased. The GWF calculations for the TN and TP were compatible with the temporal trends for the concentrations, which were higher in the wet season (0.45 m 3 /m 2 for TN, 0.10 m 3 /m 2 for TP) than in the dry season (0.11 m 3 /m 2 for TN, 0.02 m 3 /m 2 for TP) and increased from upstream to downstream. The WPLs of TN exceeded 2.0 in the midstream and downstream areas, whereas those for TP were inconspicuous. According to PLS-SEM, the GWF is primarily influenced by topographical variables and hydrological features, whereas the WPL is mainly controlled by hydrological features and landscape composition. Fertilizer reduction and efficiency measures should be implemented on farmland and appropriately reducing farming activities on slopes to relieve the GWF and WPL in the watershed., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The current article focuses on the preparation and characterization of garbage enzyme (GE) and explores its applications in treating leachate. GE is prepared from fruit and vegetable wastes and characterized via analysis of metabolites, carbohydrates, proteins, antioxidants, and enzymatic activities. This study extends our understanding of GE by reporting the presence of various metabolites. Moreover, a metagenomic analysis of GE is presented, shedding light on the microbial diversity. Firmicutes emerged as the dominant phylum, surpassing other phyla, including Proteobacteria and Actinobacteria. When exploring the potential for leachate treatment, the results indicate that vegetable GE shows 68% reduction in COD (chemical oxygen demand) and 39% reduction in ammoniacal nitrogen. Similarly, non-citrus GE also showed 64% reduction in COD and a 37% reduction in ammoniacal nitrogen, followed by citrus GE with a 33% reduction in COD and a 34% reduction in ammoniacal nitrogen compared to the control., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Typical sources of nitrate pollution in the fragile ecological environment of karst areas, such as agricultural production activities and domestic sewage, have long attracted serious concern. However, coal development can play an equally significant role in releasing the nitrogen fixed in coal into surface watersheds in the form of nitrate, nitrite, or ammonia, consequently threatening the water quality of surface water systems in mining areas. In this study, a typical karst surface watershed system affected by coal mining activities was selected for an in-depth investigation with the aim of realistically assessing the potential contribution of coal mining to nitrogen pollution. The results reveal increasingly concerning nitrate pollution from August 2020 to November 2021 in the Huatan River watershed under the influence of anthropogenic activities, especially mining development and agricultural production. Given that the nitrogen and oxygen isotope compositions of nitrate do not support the presence of denitrification, the variation in the NO 3 - /Cl - ratio and the relatively stable Cl - concentration may be a reflection of nitrification. Although the leaching of atmospheric precipitation on the strata in the basin promoted the release of nitrogen associated with coal mining, the higher rate of nitrogen cycling in the oligotrophic mine water environment limited the contribution of coal mining to nitrogen pollution in the surface watershed. Specifically, the contribution of coal mining activities to nitrogen pollution in surface karst river is mainly NH 4 + -N, which contributes 10% or less to the nitrate input to the waters of the Huatan River. The findings thus highlight the necessity of further uncovering the geochemical cycling process of nitrogen during the transport of mine water in the coal mining environment., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Currently, there is limited understanding of the structures and variabilities of bacterial communities in oil-contaminated soil within shale gas development. The Changning shale gas well site in Sichuan province was focused, and high-throughput sequencing was used to investigate the structures of bacterial communities and functions of bacteria in soil with different degrees of oil pollution. Furthermore, the influences of the environmental factors including pH, moisture content, organic matter, total nitrogen, total phosphorus, oil, and the biological toxicity of the soil on the structures of bacterial communities were analyzed. The results revealed that Proteobacteria and Firmicutes predominated in the oil-contaminated soil. α-Proteobacteria and γ-Proteobacteria were the main classes under the Proteobacteria phylum. Bacilli was the main class in the Firmicutes phylum. Notably, more bacteria were only found in CN-5 which was the soil near the storage pond for abandoned drilling mud, including Marinobacter, Balneola, Novispirillum, Castellaniella, and Alishewanella. These bacteria exhibited resilience to higher toxicity and demonstrated proficiency in oil degradation. The functions including carbohydrate transport and metabolism, energy metabolism, replication, recombination and repair replication, signal transduction mechanisms, and amino acid transport and metabolism responded differently to varying concentrations of oil. The disparities in bacterial genus composition across samples stemmed from a complex play of pH, moisture content, organic matter, total nitrogen, total phosphorus, oil concentration, and biological toxicity. Notably, bacterial richness correlated positively with moisture content, while bacterial diversity showed a significant positive correlation with pH. Acidobacteria exhibited a significant positive correlation with moisture content. Litorivivens and Luteimonas displayed a significant negative correlation with pH, while Rhizobium exhibited a significant negative correlation with moisture content. Pseudomonas, Proteiniphilum, and Halomonas exhibited positive correlations not only with organic matter but also with oil concentration. Total nitrogen exhibited a significant positive correlation with Taonella and Sideroxydans. On the other hand, total phosphorus showed a significant negative correlation with Sphingomonas. Furthermore, Sphingomonas, Gp6, and Ramlibacter displayed significant negative correlations with biological toxicity. The differential functions exhibited no significant correlation with environmental factors but displayed a significant positive correlation with the Proteobacteria phylum. Aridibacter demonstrated a significant positive correlation with cell motility and cellular processes and signaling. Conversely, Pseudomonas, Proteiniphilum, and Halomonas were negatively correlated with differential functions, particularly in amino acid metabolism, carbohydrate metabolism, and membrane transport. Compared with previous research, more factors were considered in this research when studying structural changes in bacterial communities, such as physicochemical properties and biological toxicity of soil. In addition, the correlations of differential functions of communities with environmental factors, bacterial phyla, and genera were investigated., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

This study outlines the development of an effective pilot-scale simultaneous denitrification and nitrification (SDN) system using intermittent aeration for the removal of carbon and nitrogen from real domestic sewage. Given the limited research in this area, the main objective was to evaluate the overall performance of the SBRIA system on a pilot scale and show its benefits in domestic wastewater treatment. The structured bed reactor with intermittent aeration (SBRIA) notably achieved 57% efficiency in removing total nitrogen without requiring external carbon sources. It also demonstrated impressive removal rates of 56% for total chemical oxygen demand (COD T ) and 82% for biochemical oxygen demand (BOD 5 ), indicating its effectiveness in degrading organic matter. In addition, the SBRIA showed high pH control and managed the consumption of alkalinity without the need for an alkalizer, maintaining consistent mean values of 7.7 ± 0.8 for pH and 166.8 ± 79.8 mg·L -1 for alkalinity. The system also proved resilient against toxic shocks caused by significant variations in influent characteristics. This study offers valuable insights and compelling results into a cost-effective and efficient treatment approach using an innovative technology not previously applied at the pilot scale. Its potential to remediate polluted water is substantial., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Reducing the environmental issues brought on by nutrients especially nitrogen pollution and loss is important. Owing to its unique composition and physico-chemical characteristics, biomass-derived biochar exhibits varying degrees of adsorption and interception for all types of soil nutrients. Thus, a novel way to improve nutrient absorption in the soil is to include biomass derived biochar into it. Various biomass-derived biochar from locally available biobased substances was synthesized through low-cost portable charring kiln. It has been quantified the influence of four biobased substances and three pyrolysis temperature on different morphomineralogical characteristics of biochar for utilizing as low-cost sorbent to manage nutrient adsorption and retention capacity. The morphomineralogical characteristics were principally manipulated by feedstocks rather than pyrolysis temperature. Higher porosity and surface area of biomass-derived biochar illustrated its soil structural modification and nutrient retention capacity along with their utilization for adsorbents. With increase in pyrolysis temperature, the adsorption capacity of biochar for NH 4 + -N and NO 3 - -N was gradually weakened and gradually enhanced respectively. The adsorption process of ammonia nitrogen and nitrate nitrogen conformed to the Langmuir model and the fitted KL value was less than 1 indicating that the adsorption process was uniform monolayer adsorption and the adsorption of biochar was favorable adsorption. With increase in biochar application rate the leaching of NO 3 - -N decreased having higher at 2.5 t ha -1 application rate followed by 5 t ha -1 and lower at 7.5 t ha -1 . In packed soil column, the NH 4 + -N in leachate was maximum in T 7 (18.6), followed by T 4 (17.9), T 13 (17.3) and minimum in T 10 (17.2) at same application rate of manures and biochar. Finally, results also revealed that packed soil column performed better as compared with intact soil column to retain soil nutrient and hence, leaching potential of nutrient was less in packed column than intact soil column. In conclusion, biomass-derived biochar can enhance the amount of nutrient that is absorbed into the soil while decreasing the loss of nutrient from the soil in the form of ammonia and nitrate. To sum up, biomass-derived biochar can increase the adsorption amount of the nitrogen and reduce the loss of ammonia nitrogen and nitrate nitrogen in the soil, thus retaining the nitrogen., (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Wood vinegar (WV) is known to retard the release of ammonium (NH 4 + ) from urea by inhibiting urea hydrolysis. However, the effect of WV on nitrogen leaching in soil is not known, and there are few studies on the effect of WV on microbial activity although WV exhibits antibacterial properties against pathogens in agriculture. Therefore, the purpose of this study was to investigate the effect of WV on controlling nitrogen leaching and soil microbial activity. Soils were treated with urea and WV, and the available inorganic nitrogen concentrations in the soil were compared with those from soils treated with N-(n-butyl)thiophosphoric triamide (NBPT), a commonly used urease inhibitor. The nitrate concentration in the soil was significantly decreased in the WV treatment, although the ammonium concentration was not affected by the WV treatment. Basal soil respiration was significantly increased in the WV and NBPT treatments although the microbial biomass was increased in the urea only treatment. The ammonium nitrogen concentration in the leachate was not significantly different in the WV and urea-treated soil compared to the urea-only treatment. However, the nitrate leaching increased in the soil treated only with urea at 16 days after the treatment although there was no statistically significant difference in the total leached nitrate. Therefore, WV can be used to reduce nitrogen leaching and enhance soil microbial activity., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Due to the slow growth rate of anammox bacteria, enriched sludge is required for the rapid start-up of anammox-based reactors. However, it is still unclear if long-term stored anammox sludge (SAS) is an effective source of inoculum to accelerate reactor start-up. This study explored the reactivation of long-term SAS and developed an efficient protocol to reduce the start-up period of an anammox reactor. Although stored for 13 months, a low level of the specific anammox activity of 28 mg N/g VSS/d was still detected. Experimental Phase 1 involved the direct application of SAS to an upflow sludge bed reactor (USB) operated for 90 d under varying conditions of hydraulic retention time and nitrogen concentrations. In Phase 2, batch runs were executed prior to the continuous operation of the USB reactor. The biomass reactivation in the continuous flow reactor was unsuccessful. However, the SAS was effectively reactivated through a combination of batch runs and continuous flow feed. Within 75 days, the anammox process achieved a stable rate of nitrogen removal of 1.3 g N/L/day and a high nitrogen removal efficiency of 84.1 ± 0.2%. Anammox bacteria (Ca. Brocadia) abundance was 37.8% after reactivation. These overall results indicate that SAS is a feasible seed sludge for faster start-up of high-rate mainstream anammox reactors., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

This study evaluated the treatment efficiency of municipal wastewater from Phetchaburi in Thailand in an alternated 5-day flooding and 2-day drying wetland system with two plants species, namely, Canna indica and Heliconia psittacorum. The efficiencies of biochemical oxygen demand (BOD5) treatment were in the ranges of 90.5% ± 4.8% and 86.9% ± 7.3% for Canna and Heliconia, respectively. Those of chemical oxygen demand (COD) treatment were in the ranges of 75.5% ± 7.9% and 75.3% ± 9.0% for Canna and Heliconia, respectively. Both plants' removal efficiencies of TN, NH4-N, and TP were greater than 40%. Lead and cadmium accumulation in both plants significantly differed between the upper and lower parts of the plants. However, the lead and cadmium accumulation in Heliconia were greater than their accumulation in Canna. Although Canna had a higher nutrient removal efficiency than Heliconia, there are many varieties of Canna in Thailand. These results indicate that the variety of Canna does not affect the nutrient removal efficiency. In conclusion, a wetland system with alternated flooding and drying conditions can be applied in communities where BOD 5 and COD are the dominant wastewater pollution characteristics. Both ornamental plants are suitable absorbents for lead and cadmium, and although the accumulation is lower in Canna than in Heliconia for both heavy metals, the difference was not significant., (© 2023. The Author(s).)

The combined role of ground cover management in controlling soil erosion and nutrient loss from new orchards is still less understood. In this study, four ground cover management practices, orchard with grass cover (OG), orchard with interplant cover (OI), orchard with straw cover (OS), and orchard with bare ground (OB), were designed to identify their impacts on soil erosion and associated carbon-nitrogen-phosphorus loss in new orchards by rainfall simulation tests with rainfall intensities of 60, 90, and 120 mm h -1 and 90 min rainfall duration. The results showed that OS had the lowest surface flow coefficient (6.6%) and highest subsurface flow coefficient (32.5%). The highest soil loss rate occurred in the OB plot (65.4 g m -2  min -1 ), and the lowest soil loss rate occurred in the OS plot (0.5 g m -2  min -1 ). OS plot showed better effectiveness in improving soil erosion. However, the increased infiltration capacity was facilitated in terms of causing non-point source pollution. The C-N-P ratios of surface flow in different cover measures (OB, OI, OG, and OS) were 1.4:1.2:0.9:1, 1.8:1.7:1.2:1, and 2.3:1.9:1.2:1, respectively. The ratios of sediment in different cover measures were 7.3:9:2.3:1, 2:1.5:1.2:1, and 1.2:1:0.8:0.7, respectively. Cover management plots play an active role in reducing nutrient loss in surface flow and sediment, but the increased infiltration in covered management plots is associated with the risk of groundwater contamination in subsurface flow. The C-N-P ratios of subsurface flow in OB and covered managed plots (OI, OG, and OS) were 1:3.3:1.6:2.7, 1:1.5:2.2:2.4 and 1:1.2:1.5:1.3, respectively. Therefore, when managing the phenomenon of soil erosion through ground cover measures, attention should also be focused on the function of cover measures in regulating non-point source pollution underground, such as subsurface flow. This research recommends a combination of cover management measures to further mitigate erosion and the risk of groundwater contamination., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Water treatment for most public pools involves disinfection with active chlorine leading to the formation of disinfection by-products (DBPs). Among them, nitrogen-containing compounds (N-DBPs) having increased toxicity and adverse effects on human health are of the greatest concern. Being the major component of various body washers for swimmers, cocamidopropyl betaine (CAPB) represents a potential and still underestimated anthropogenic precursor of N-DBPs in pool water. The purpose of this study was to investigate CAPB transformation pathways and mechanisms under the aqueous chlorination conditions. High-performance liquid and two-dimensional gas chromatography hyphenated with high-resolution mass spectrometry were used for the search and tentative identification of the primary and final CAPB transformation products. A wide range of DBPs containing up to five chlorine atoms including these in combination with hydroxyl and additional carbonyl groups has been revealed in model chlorination experiments for the first time. The proposed mechanism of their formation involves nucleophilic substitution of the secondary amide hydrogen atom at the first stage with subsequent free radical and electrophilic addition reactions resulting in non-selective introduction of halogen atoms and hydroxyl groups in the alkyl chain. The deep transformation products include short-chain chlorinated hydrocarbons and their oxidation products as well as dimethylcarbamoyl chloride possessing high toxicity and carcinogenic properties. Targeted analysis of real swimming pool water samples confirmed the results of model experiments enabling semi-quantitative determination of CAPB (0.8 µg L -1 ) and 18 primary DBPs, including 10 chlorine-containing compounds with the total concentration of 0.1 µg L -1 . Among them, monochloro (50%) and hydroxydichloro (25%) derivatives predominate. The toxicity and health of the main DBPs has been estimated using QSAR/QSTR approach. Thus, the possibility of formation of new classes of potentially toxic chlorine-containing DBPs associated with the widespread use of detergents and cosmetics was shown., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Glyphosate herbicide is an indispensable material in agricultural production. In order to explore the potential environmental effects of glyphosate application in karst slope farmland, this paper used a variable slope steel tank to simulate the surface microtopography and underground pore structure characteristics of karst slope farmland, and combined with artificial rainfall experiments to explore the migration path of glyphosate in karst slope farmland and the impact of spraying glyphosate on soil nitrogen and phosphorus loss. The results showed that under the condition of heavy rain, glyphosate in karst slope farmland was mainly transported and diffused by surface runoff, supplemented by underground runoff; secondly, in different hydrological paths, glyphosate directly affected the content of nitrogen and phosphorus in runoff, and all showed extremely significant positive correlation (p < 0.001). In addition, rainfall conditions such as rainfall intensity, rainfall duration, and runoff affected the content of nitrogen and phosphorus in runoff to varying degrees. In conclusion, the application of glyphosate significantly increased the content of nitrogen and phosphorus in different runoff and accelerated the loss of nitrogen and phosphorus from soil, which not only led to soil degradation, but also threatened the safety of aquatic ecosystem. Therefore, in the prevention and control of agricultural non-point source pollution, the threat of glyphosate to the surrounding aquatic ecosystem cannot be ignored, especially in karst areas with frequent rainstorms and serious water erosion, long-term monitoring and risk assessment of glyphosate are needed., (© 2023. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Lake Nokoué, a major component of the hydrographic system of the Ouémé delta, is the largest lagoon-estuarine ecosystem in Benin. Recent studies have shown that benthic processes would actively participate in the maintenance of the eutrophication and biogeochemical cycle of this ecosystem. In order to understand the implication of the bottom on the quality of the waters of the lake, a monthly follow-up of ten (10) parameters of quality of the waters of the bottom was undertaken from July 2020 to December 2021 on a network of nineteen (19) stations distributed on the whole lake. Univariate and multivariate analysis techniques were used to assess the spatial and temporal dynamics of these waters. The Kruskal-Wallis test, PCA, correlation analysis and discriminant analysis all showed a very marked influence of the hydrological regime on the concentration of nutrients compared to the influence of anthropogenic activities around the lake and an influence of climatic conditions on internal processes. Indeed, water inflows from the Ouémé watershed are the main contributors of phosphorus in the lake while benthic processes are the most important contributors of nitrogen. Cluster analysis defined three significantly different areas in Lake Nokoué: the channel, the centre of the lake and the river mouth. A single station in each cluster could be used for a spatial assessment of water quality over the entire lake., (© 2023. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Human activities are increasing wildfires and livestock activity in arid ecosystems with potential implications for the spread of invasive grasses. The objective of this study was to test whether fire history and cattle activity alter soil resource gradients, thereby affecting patterns of Bromus rubens L. (red brome) invasion. Six paired burned and unburned transect lines (1-km long) were established in the northeast Mojave Desert along the boundaries of four independent wildfire scars. At 100-m transect increment points, we measured the distance to the two nearest cowpats, and two random points and measured the density, height, biomass, and seed production of red brome, soil moisture and inorganic nitrogen (N). Cattle activity was 29% greater along burned transects compared to unburned transects (P < 0.05). Red brome height, density, and seed production were 11-34% greater along burned transects than unburned transects (P < 0.05). Red brome height, biomass, density, and seed production were twofold to tenfold greater next to cowpats compared to random points (P < 0.05). Soils along burned transects and beneath cowpats had greater soil inorganic N (P < 0.05), which was positively correlated with red brome density, height, biomass, and seed production (R 2  = 0.60-0.85, P < 0.0001). Transgenerational effects were evident as seeds from red brome next to cowpats had 27% higher germination than seeds collected from random points. Positive responses of red brome to increased inorganic N related to fire and cattle activity may contribute fine fuel infill that drives invasive grass-fire cycles in deserts., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The depletion of groundwater resources in the water-stressed regions has led to the overuse of surface water reservoirs. Recharging groundwater by rejuvenating dried surface reservoirs using recycled water is a new sustainable solution. To ensure the prevention of groundwater contamination and associated health risks (as recycled water is used), it is crucial to assess the surface reservoir water quality. The study for the first time suggests the Lake2K model, a one-dimensional mechanistic mass-balance model, to simulate the changes in water quality in a series of man-made surface water reservoirs where recycled water flows under an indirect groundwater recharge scheme (soil aquifer treatment system). The model was developed, calibrated, and validated using field observations to estimate degradation/reaction rate constants for various water quality parameters. The observed average degradation/reaction rate constants for parameters including ammonia-N, nitrate-N, total nitrogen, total organic carbon, and organic phosphorous were 0.043 day -1 , 0.04 day -1 , 0.043 day -1 , 0.055 day -1 , and 0.056 day -1 , respectively, which were found to be relatively high compared to existing literature, indicating a greater degradation of these parameters in warmer climates. The results showed that the water quality improved significantly as the water progressed through the reservoirs, aligning with field observations. Additionally, the simulated seasonal variations revealed that the maximum growth rate of phytoplankton occurred during July, August, and September for each reservoir, while the nutrient pool (nitrate-N and orthophosphates) experienced the greatest depletion during this growth period. These findings shed light on the dynamics of surface water quality in regions facing water scarcity and contribute to the development of sustainable groundwater management strategies., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Herein, a new type of super active nitrogen-doped biochar sheet (SNBC) was prepared by two-step pyrolysis and KOH chemical activation with melamine and cherry kernel powder as precursors of nitrogen and carbon source for removing Hg 2+ from wastewater. The N 2 adsorption/desorption and scanning electron microscope characterization revealed that the resulted SNBC under 600 °C calcination owned huge specific surface area of 2828 m 2 /g and plenty of well-developed micropores, and X-ray photoelectron spectroscopy and Fourier transform-infrared spectroscopy analysis testified the existence of functional groups containing N and O, which could provide adsorption sites for Hg 2+ . The SNBC-600 showed high adsorption capacity for Hg 2+ even at low pH, and interfering cations had little effect on the adsorption. The adsorption process was rapid and dynamic data fit the pseudo-second-order dynamic model well. The maximum adsorption capacity of Hg 2+ on SNBC-600 calculated by Langmuir model was 230 mg/g. After six times of reuse, the adsorption capacity still exceeded 200 mg/g, exhibiting good reusability. The designed microfiltration membrane device base on SNBC-600 could remove low concentration of Hg 2+ effectively from solution. This study provided a simple and environment-friendly method for manufacturing nitrogen-doped biochar sheet, which was of great significance in the practical application of Hg 2+ pollution treatment., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The predicting groundwater nitrate pollution risk, especially in terms of changes in fertilizing, has not been fully investigated so far. In particular, there is no comprehensive method to assess this risk in areas of different land use type, and not only in agricultural areas. The aim of this study was to develop a novel multicriteria methodology for groundwater nitrate pollution risk assessment, which meets these issues. A further aim was to determine how much this risk would change if the amount of organic and synthetic fertilization was reduced. An assumption was that groundwater pollution risk is a combination of the potential adverse impacts of land use, fertilization, and intrinsic groundwater vulnerability to pollution. The impact of fertilization was holistically evaluated by balancing nitrogen from spatially differentiated the size of the breeding, species of livestock, manure and synthetic fertilizers input, and spatially differentiated topsoil, with nitrogen uptake by different crops. The nitrate concentration in the leachate was used as a measure of the impact of fertilization. This concentration was compared to the natural baseline nitrate concentration in groundwater. Three fertilization scenarios for groundwater pollution risk assessment in two study areas were discussed. Under typical agricultural, climatic, soil, and geological conditions in Europe for the current total fertilization level of 95-120 kg N ha -1 groundwater nitrate pollution risk is low and moderate, but for fertilization of 150-180 kg N ha -1 , a reduction in the total fertilization (synthetic and manure) by 40 to 50% may be required to achieve low risk of degradation of natural groundwater quality. Predictive simulations of groundwater nitrate pollution risk confirmed that reducing synthetic and organic fertilization has an effect, especially in areas with intensive fertilization. This method may allow for a holistic and scenario-based assessment of groundwater pollution risk and may help decision-makers introduce solutions to manage this risk under conditions of climate change, preservation of groundwater quality, and food security., (© 2023. The Author(s).)

In this pilot-scale study, simultaneous partial nitrification, anammox, and denitrification (SNAD) process was achieved successfully in a moving bed biofilm reactor (MBBR) for treating anaerobic digester liquor of swine wastewater. After 95 days of operation, when the total nitrogen loading rate of SNAD-MBBR process was 1.09 kg TN/m 3 /day, the total nitrogen removal rate could reach 0.87 kg TN/m 3 /day, and the removal efficiencies of ammonium and total nitrogen were 92.0% and 79.7%, respectively. The optimum pH and temperature for SNAD-MBBR process were 8.5 and 35 °C, respectively, and the optimum dissolved oxygen for SNAD1 and SNAD2 were 0.30 and 0.07 mg/L, respectively. The 16S rRNA sequencing suggested that Candidatus Kuenenia, Candidatus Brocadia, Nitrosomonas, and Denitratisoma were the dominant nitrogen removal bacteria. Some of the co-existing bacteria (Truepera, Limnobacter, and Anaerolineaceae uncultured) promoted ammonium oxidation and guaranteed the growth of the anammox bacteria under adverse environmental conditions. Overall, this study demonstrated that the SNAD-MBBR process would be an energy-saving and cost-effective method for the removal of nitrogen from swine wastewater and provided important process parameters for stable operation of the full-scale SNAD process., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

A lab-scale granular sludge sequencing batch reactor (G-SBR) system was operated using synthetic wastewater. The total nitrogen removal efficiency of 85% was obtained together with the achievement of complete total phosphorus removal with average granule diameter of 400 µm. Dual-step nitrification and denitrification model with fixed biofilm thickness was used for performance analysis. The denitrification mode only contributed to TN removal with 25% which can be calculated with process stoichiometry. The remaining nitrogen removal could be explained by simulating simultaneous nitrification and denitrification which was responsible for 75% denitrification during aerobic period. In addition, low NO 3 - concentration at the beginning of the fill period provided advantage for securing a prolonged anaerobic period for enhanced biological phosphorus removal (EBPR). The model parameters of boundary layer thickness (z BL  = 50 µm) and half-saturation of O 2 for nitrite-oxidizing bacteria (K O2,NOB  = 0.5 gO 2 /m 3 ) were tuned to fit NO 2 and NO 3 profiles in SBR cycle., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Global riverine nitrogen (N) and phosphorus (P) transport models offer important insights into basin nutrient cycling. However, appropriate model selection for a given research objective remains ambiguous. This study conducted a meta-analysis to evaluate the performance and applicability of three prevalent global riverine nutrient transport models: Global NEWS, IMAGE-GNM, and WorldQual. According to performance criteria (satisfactory: R 2 > 0.50 and NSE > 0.50), the Global NEWS model performs satisfactorily in simulating dissolved organic nitrogen (DON; n = 101, R 2 = 0.58, NSE = 0.57) and dissolved organic phosphorus loads (DOP; n = 80, R 2 = 0.59, NSE = 0.59). The model falls short in simulating dissolved inorganic nitrogen (DIN; n = 644, R 2 = 0.56, NSE = - 0.80) and dissolved inorganic phosphorus loads (DIP; n = 450, R 2 = 0.33, NSE = - 0.12). The IMAGE-GNM model shows satisfactory accuracies in simulating riverine total nitrogen (TN; n = 831, R 2 = 0.56, NSE = 0.53) and total phosphorus (TP; n = 902, R 2 = 0.59, NSE = 0.48) concentrations, particularly in European basins. The WorldQual model presented unsatisfactory performance in simulating riverine TN (n = 11, R 2 = 0.76, NSE = 0.34) and TP (n = 13, R 2 = 0.71, NSE = - 0.25) concentrations. Using a two-segment linear model, we recommend the Global NEWS model for basins larger than 2.2 × 10 4 km 2 for DIN and 3.2 × 10 4 km 2 for DIP. The IMAGE-GNM model is best suited for basins with long-term datasets and high latitudes (TN > 21 years and > 53.8 °N; TP > 22 years and > 54.5 °N). For model improvements, both the Global NEWS and WorldQual models could benefit from enhanced in-stream nutrient retention/release modules. The Global NEWS model could be further improved with a better chemical weathering module. For the IMAGE-GNM model, refining the soil erosion module is warranted to enhance model performance. Addressing legacy nutrient effects is crucial for all three models. This study provides valuable guidance for selecting and improving nutrient transport models based on specific research needs., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

This study analyses particulate organic carbon (POC) and particulate nitrogen (PN) export from Indian monsoonal rivers to the north Indian Ocean. Indian monsoonal rivers export approximately 1.2 Tg yr -1 (1Tg = 10 12  g) of POC and 0.14 Tg yr -1 of PN, with about two-thirds entering the Bay of Bengal (0.8 and 0.1 Tg yr -1 , respectively) and the remaining reaches to the Arabian Sea (0.4 and 0.04 Tg yr -1 , respectively). Remarkably, just four rivers from northwest India's black soil-dominated regions contribute about half of the total POC and PN exports (0.64 and 0.06 Tg yr -1 , respectively). This is due to substantial erosion in these catchments, resulting in suspended matter concentrations averaging 596 ± 252 mg L -1 , significantly higher than catchments dominated by red sandy, red loamy and alluvial soils (54 ± 56 mg l -1 ). In contrast, rivers originating from catchments with heavy precipitation, a tropical wet climate, red loamy soils (with peaty and marshy characteristics), rich tropical wet evergreen and moist deciduous forests, and higher soil organic carbon content yield more POC and PN (1704 ± 383 kgC km -2  yr -1 and 261 ± 56 kgN km -2  yr -1 , respectively) than the other rivers of India (951 ± 508 kgC km -2  yr -1 and 120 ± 57 kgN km -2  yr -1 , respectively). These findings stress that the export flux and yield of POC and PN from the Indian monsoonal rivers are primarily influenced by the interplay of hydrological, lithological, environmental, and climatic conditions within the catchment, rather than river size. Moreover, this study highlights the significant impact of incorporating POC data from medium-sized rivers worldwide, as it reveals that yield is independent of river size. This calls for a re-evaluation of global POC export fluxes, taking into account hydrological, lithological, environmental, and climatic factors., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Microbial communities play an important role in water quality regulation and biogeochemical cycling in freshwater ecosystems. However, there has been a lack of research on the seasonal variation of sediment microorganisms in the sediments of small river basins in typical semi-arid region. In this study, high-throughput DNA sequencing was used to investigate the fungal community and its influencing factors in the sediment of the Dali River in the dry and wet seasons. The results showed that there were obvious seasonal differences in fungal alpha diversity. The diversity and richness of fungi in the dry season were greater than that in the wet season, but the evenness of fungi in the dry season was lower than that in the wet season. In addition, Ascomycota and Basidiomycota were the most important phyla in the Dali River fungal community, but their distributions showed clear seasonal differences. In the dry season, the relative abundance of Ascomycota and Basidiomycota were 12.34-46.42% and 17.59-27.20%, respectively. In the wet season, the relative abundances of these two phyla were 24.33-36.56% and 5.75-12.26%, respectively. PICRUSt2 was used to predict the metabolic function of fungal community in the sediment, and it was found that at the first level, the proportion of biosynthesis in the dry season was higher than that in the wet season. The ecological network structure showed that the fungal community in the wet season was more complex and stable than that in the dry season. The characteristic fungi in the dry season sediment were chytrid fungi in the family Rhizophydiaceae and the order Rhizophydiales, whereas those in the wet season sediment were in the orders Eurotiales and Saccharomycetales. Canonical correspondence analysis (CCA) showed that the physicochemical properties of water and sediment together explained a greater proportion of the dry-season fungal community changes than of the wet-season changes. In the dry season, temperature and ammonia nitrogen in the water were the main factors affecting the change of fungal community, whereas in the wet season, total nitrogen concentration of the water, electrical conductivity, total organic carbon and available phosphorus of the sediment, pH, and temperature were the main factors affecting the changes in fungal community composition. The results of this study enhanced our understanding of microbial communities in semi-arid river ecosystems, and highlight the importance of the management and protection in river ecosystems., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Reservoir cascade systems have attracted the attention of scientists worldwide. The present study investigates the cascade of five reservoirs (R1, R2, R3, R4, and R5) along a 192-km water channel system located in the state of Ceará, in the Brazilian semiarid region. This cascade system was implemented in 2012 to promote water availability and security to the capital of Ceará and the strategic industry and port complex of the region. However, these reservoirs have faced a progressive degradation of water quality, which has resulted in intense eutrophication and high-water treatment costs. The study evaluates the dynamics of water quality from 2013 to 2021 along this reservoir cascade (from R1 to R5). The results revealed that water quality did not improve along the cascade system, differently from previous studies on reservoirs interconnected by natural rivers. This was attributed to the low water residence time and low capacity of pollutant removal along the man-made water channel system, as well as to the high internal phosphorus loads of the reservoirs. Multiple regression models involving the explanatory variables of total phosphorus, total nitrogen, chlorophyll-a, cyanobacteria, transparency, rainfall, and volume from upstream reservoirs were obtained to determine total phosphorus concentration in downstream reservoirs, considering different combinations of reservoir pairs in the cascade and different time delays. A clear trend of R 2 decline with the distance between the upstream and downstream reservoirs was observed. For example, the R 2 values for the correlations adjusted between R1 and R2 (48 km), R1 and R3 (172 km), R1 and R4 (178 km), and R1 and R5 (192 km) were 0.66, 0.32, 0.22, and 0.12, respectively. On the other hand, the adoption of time delays of the order of the cumulative residence times of the reservoirs promoted a significant improvement in the R 2 values. For instance, the best correlation adjusted between R1 and R5 improved from R 2  = 0.12 to 0.69 by considering a time delay of 21 months. This suggests that previous data from upstream reservoirs can be used to predict current and future total phosphorus concentration in downstream reservoirs. The results from this study are important to better understand the spatiotemporal dynamics of water quality in reservoir cascade systems and thus improve water resources management, especially in drylands., (© 2023. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Understanding the spatial expansion process of salt marshes and quantifying the factors driving this expansion are crucial for the management and restoration of coastal wetlands. In this study, we aimed to illustrate the expansion process of Scirpus mariqueter using drone remote sensing and quantify its relationship with habitat quality. Our hypothesis was that landscape metrics could serve as valuable indicators for prioritizing habitat restoration efforts along the coast. We utilized drone remote sensing and adopted the simple Greenness Index to reflect the growth status of S. mariqueter. Using this index, we computed the standard deviation ellipse and growth center. To evaluate habitat quality, we developed a method based on our previous research and other relevant reports. We then conducted a quantitative analysis of the expansion process of S. mariqueter in areas with varying habitat quality. We found that S. mariqueter's optimal elevation was 3.7 m, with a range of 2.5 to 4.3 m. The threshold value for soil total nitrogen was 0.3 g/kg, and the tolerance threshold for soil salinity was 2500 ppm. These three factors, elevation, soil total nitrogen, and soil salinity, collectively influenced habitat quality, with weights of 0.68, 0.23, and 0.09, respectively, as determined through geodetector analysis. During the summer, we observed a dominance of dispersal in S. mariqueter, with the species primarily spreading to areas with increased habitat quality. Patch shapes tended to be compact and regular in this season. In contrast, during the autumn, a dominance of decline was observed, with S. mariqueter mainly distributing to areas exhibiting decreased habitat quality. Patch shapes tended to be complex and irregular in the autumn season. Eventually micro-geomorphic modification and patch shape filling methods based on UAV observations are proposed to aid wetland restoration. These findings are of utmost importance for the restoration of coastal wetlands and the enhancement of ecosystem resilience., (© 2023. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Changes in soil quality as a result of climate change and grazing regimens have become an important issue for rangeland sustainability. Although there has been much research on the impacts of overgrazing on soil in highland rangelands, Turkey, there has been little on the effects of light grazing on the soils. This study aimed to examine select soil parameters in the lightly grazed (LGR) and ungrazed rangelands (UGR) to evaluate the sustainability of the rangeland soils under the light grazing. Soil penetration resistance (SPR) was measured at depths of 0-10, 10-20, and 20-30 cm. Soil samples were taken from the points where SPR measurements were made, and soil texture, soil bulk density (SBD), soil organic matter (SOM), soil organic carbon (SOC), and soil total nitrogen (TN) were determined. According to this study's findings, SOM, SOC, TN, SPR, and SBD levels were higher in LGR sites than in UGR sites. Although SPR was higher in the grazing site, it was discovered that this excess was smaller than the critical penetration resistance values. Because SPR is lower than the necessary resistance value for root development and SOM, SOC, and TN values are high, light grazing can be considered a sustainable approach. However, soil measurements should be conducted periodically to support sustainable rangeland management due to climate change., (© 2023. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

A proper understanding of soil parameters under different production systems of the world is necessary for efficient soil management. We, therefore, carried out the present study to assess the status of some selected soil properties (soil pH and electrical conductivity (EC)), phyto-available nutrients (available nitrogen (AN), available potassium (AK), exchangeable calcium (Ex. Ca), exchangeable magnesium (Ex. Mg), available sulfur (AS), and soil organic carbon (SOC) pools (SOC, total organic carbon (TOC), very labile C, labile C, less labile C, and non-labile C) and to establish relationships among the measured soil parameters at different depths of Vertisols of India under various land uses. A total of 150 composite soil samples (from 25 plots including nine from agricultural land, nine from horticultural land, three from forest land, and four from grassland) were collected from 6 soil depths viz, 0-10, 10-20, 20-40, 40-60, 60-80, and 80-100 cm under agriculture, horticulture, forest, and grassland land uses present in Central India and analyzed. The values of soil pH, EC, AN, AK, Ex. Ca, Ex. Mg, and AS in various soil depths under different land uses varied widely. The values of SOC (0.19 to 1.00%), TOC (0.58 to 2.42%), very labile C (0.14 to 0.83%), labile C (0.05 to 0.25%), less labile C (0.05 to 0.26%) and non-labile C (0.23 to 1.42%) in various soil depths under different land uses also varied significantly. Forest and grassland land uses had higher levels of SOC, TOC, very labile, and non-labile C content in all the soil depths in comparison to SOC, TOC, very labile, and non-labile C content in different soil depths under agriculture and horticulture land use. The levels of SOC, TOC, very labile, and non-labile C content under all the land uses decreased with increasing soil depths. SOC was positively and significantly correlated with AN, AK, AS, and estimated SOC pools in surface soil layers. Principal component analysis (PCA) of soil parameters in different soil depths resulted in 5 principal components (PCs) with > 1 eigenvalue and accounting for > 75% variability. This information could be used for managing SOC status and phyto-available nutrients in Vertisols under different land uses., (© 2023. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Sediment is an important carrier of evidence about environmental evolution which receives huge volumes of organic material originated from both anthropogenic and natural sources. In this study, based on sedimentary chronology, the vertical trends of particle size distribution, total organic carbon (TOC), total nitrogen (TN), and their stable isotopes (δ 13 C, δ 15 N) in the sediment core of the nuclear power sea in southwest Daya Bay were analyzed, and the distribution characteristics and contribution ratios of different sources of organic matter in the sedimentary environment over the past 70 years were resolved using a Bayesian mixing model (MixSIAR). TOC, TN, δ 13 C, and δ 15 N ranged from 0.89 to 1.56%, 0.09 to 0.2%, - 22.3 to - 20.6‰, and 4.38 to 6.51‰, respectively. The organic matter in the sediment is controlled by a mixture of terrestrial input and marine autochthonous, the proportion of organic matter from terrestrial sources increases, while that from marine sources decreases in the sediment core, which persists from 1960 to 2000, yet organic matter from marine sources still dominates. The first signs of increased primary productivity occurred in 1960, and it was primarily due to agricultural activity. After the 1980s, the rapid increase in population around Daya Bay, the construction of nuclear power plants, the rise of aquaculture, and the quick expansion of industrial bases were all major factors that changed the ecological environment of Daya Bay., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Small streams are essential parts of water ecosystems, such as rivers, lakes, and reservoirs, performing vital functions in the attenuation of nutrient pollution. As eutrophication becomes an increasingly severe problem in waters, it is necessary to investigate how to improve nutrient retention potential in streams. In this study, the effect of artificial manipulation was examined on transient storage and nutrient uptake in streams by setting up the stepping stone structures of flying-geese pattern (SG) and the combination mode of SG and bilaterally staggered spur dikes (SG+SD) in the channel. The tracer experiments were performed to confirm the effectiveness of SG and SG+SD in two headwater streams, which are tributaries of the Chaohu Lake basin. Additionally, the transient storage and nutrient uptake potential were assessed by the OTIS (one-dimensional transport with inflow and storage) model and the nutrient spiraling theory. Compared with the control, the implementation of SG in the Banqiao River increased the retention of ammonium (NH 4 + ) and phosphate (PO 4 3 ). Furthermore, the transient storage capacity and nutrient uptake potential in the Ershibu River were strengthened with the addition of bilaterally staggered spur dikes based on SG. These results highlight the importance of manipulating the geomorphology of the streambed to enhance the nutrient retention potential in streams., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Wetlands are known to experience fluctuations in water levels and receive exogenous nitrogen inputs that affect various organisms, including soil microorganisms. To study the impact of these factors on microbial diversity, we collected intact soil columns from a Phragmites australis-dominated site in the Qixing River National Nature Reserve in Northeast China. In a laboratory experiment, we simulated water level fluctuations and exogenous nitrogen inputs to the soil columns and examined the associated changes in the relative abundance of 51 bacterial genera involved in nitrogen cycling processes. Our findings revealed that different bacterial genera exhibited varying relative abundances across treatments. Specifically, Massilia showed the highest total relative abundance at the genus level, while Planctomyces had the second highest, and Campylobacter had the lowest abundance. The DESeq2 model, based on negative binomial distribution, revealed that the tags of bacterial genera were significantly correlated with soil depth, but not with water levels or nitrogen concentrations. However, the addition of a 30 mg/L nitrate solution caused a decrease in the relative abundances of bacterial genera with decreasing water levels, while a 60 mg/L concentration of nitrogen resulted in a decrease and then an increase in the relative abundances of bacterial genera with decreasing water levels. Our study provides valuable insights into the response of nitrogen-cycling bacteria to changes in different environmental conditions., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Agricultural nonpoint source (NPS) pollution loss is closely related to hydrological processes. Understanding the differences in NPS pollution load loss under hydrological processes is useful for the management and prevention of NPS pollution. In this paper, hydrological and water quality data from 2016 to 2018 and monitoring data of physical and chemical indicators in 1347 field soil samples in the Shaying River Basin (SYRB) were used to analyze spatiotemporal variations in NPS pollution using the Soil and Water Assessment Tool and multifactor analysis of variance. The intensities and differences in NPS pollution losses for different soil types and land use patterns were evaluated under different hydrological zones. The annual rainfall in the SYRB decreased gradually from 1136.50 to 404.04 mm, showing a significant zoning. Areas with high loss intensities were mainly distributed in areas with steep slopes and in the 800-1000 mm rainfall zone. Cultivated land had the largest loss of NPS pollution, followed by forest land and rural residential land. Fluvo-aquic soil had the largest loss of NPS pollution, followed by cinnamon soil and lime concretion black soil. A nonlinear regression model was established for rainfall and the NPS pollution loss intensity and had a correlation coefficient of 0.60-0.99 at a 95% confidence level. Slope and rainfall were the main factors influencing the nitrogen and phosphorus losses. In the 800-1000 mm rainfall zone, the soil background nitrogen and phosphorus load was also a major factor influencing the nitrogen and phosphorus loss intensities., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Drainage water quality is a crucial factor reflecting the regime of agricultural non-point source pollution in irrigation districts and is closely related to land use, soil texture, cropping pattern, fertilization, and irrigation and drainage conditions. However, the response of drainage water quality to various natural and anthropogenic factors needs further exploration in irrigation districts affected by shallow groundwater table. Spatiotemporal patterns of chemical oxygen demand (COD), total phosphorus (TP), total nitrogen (TN), and ammonium nitrogen (NH 4 -N) were monitored and analyzed in ten agricultural drainage ditches in the arid region of China from 2011 to 2019. Spatially, water pollution in agricultural drainage ditches with small water quantity can be significantly exacerbated by urban sewage, whereas a large amount of agricultural drainage can effectively dilute the pollution of urban sewage. Severe soil salinization in the cropland increases the risk of water pollution due to easier losses of soil nutrient and organic matter. Soil salinization is a key factor in the crop distribution pattern based on the crop salt tolerance, and the maize/wheat field with a higher fertilizer application rate generally results in poorer drainage water quality. Temporally, for the agricultural drainage ditches, the monthly and annual COD, TP, TN, and NH 4 -N concentrations fluctuate inversely with drainage water quantity and are positively correlated with fertilizer application, among which the monthly COD concentration in drainage water has larger variation in severe salinized areas. There exist critical annual and monthly drainage amounts, above which the probabilities of higher concentrations of COD, TP, TN, and NH 4 -N reduce greatly., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)