Search

Copyright of Journal of Ecology & Rural Environment is the property of Journal of Ecology & Rural Environment Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Agricultural activities contribute significantly to the pollution of groundwater through the incomplete absorption of nitrogen (N) and phosphorus (P). Understanding the vertical migration patterns of N and P in soil solution is crucial for controlling groundwater quality. This study is based on monitoring data of soil solution nitrogen and phosphorus at different depths (30 cm, 60 cm, 100 cm) in the Huixian Wetland Experimental Area in the Li River Basin from March to December 2021. The vertical distribution patterns of nitrogen and phosphorus in soil solution in the study area are elucidated from three aspects: seasonal variations, karst types, and land use. The results indicate that the following: (1) NO3−-N is the predominant form of nitrogen, generally decreasing with increasing soil depth, while NH4+-N concentrations show slight increases and TP concentrations remain relatively stable. Overall, NO3−-N and TN concentrations tend to accumulate at 30 cm and 60 cm depths during both irrigation and non-irrigation seasons, with no distinct distribution patterns observed for NH4+-N and TP. (2) During the irrigation season, the migration distance of NO3−-N in non-karst landforms is mainly at 60 cm, while in peak forest plains, it is mainly at 100 cm, with no clear trend observed in NO3−-N concentrations in peak cluster depressions. In non-irrigation seasons, the distribution of NO3−-N content in non-karst landforms and peak cluster depressions is mainly 30 cm > 60 cm > 100 cm. The downward migration distance of NH4+-N generally follows the order of peak cluster depressions > peak forest plains > non-karst landforms. (3) During the irrigation season, NO3−-N concentrations in paddy fields remain relatively high at 100 cm, while in drylands, NO3−-N concentrations generally follow the pattern of 30 cm > 60 cm > 100 cm but may exhibit anomalous increases or decreases at 60 cm and 100 cm depths during heavy rainfall. [ABSTRACT FROM AUTHOR]

Three ecological restoration systems vegetated with Vallisneria natans, containing ceramisite (VC), bio-carrier and ceramisite (BVC) or Fe/C filler, bio-carrier and ceramisite (FBVC) as functional substrates were constructed for black and odorous water restoration. The average ammonia nitrogen (NH4+ -N) conversion rate of FBVC (90.51 %) was similar to that of BVC (88.49 %) and significantly higher than that of VC (53.35 %). However, the average total nitrogen (TN) removal rate of FBVC (84.93 %) was much higher than that of BVC (73.02 %) and VC (52.06 %). Additionally, the average COD removal efficiencies for VC, BVC and FBVC were 52.54 %, 71.84 % and 80.59 %, respectively; while they were 69.72 %, 74.79 % and 97.38 % for total phosphorus (TP). Highthroughput sequencing revealed that the richness and diversity of autotrophic denitrifying bacteria, such as Pseudomonas, Pseudoxanthomonas, Arenimonas and Hydrogenophaga increased significantly in FBVC, while the plant growth-promoting bacterium Rhodobacter was dominant. Overall, this study demonstrated that a Vallisneria natans based ecological restoration system coupled with Fe/C internal electrolysis (Fe/C-IE) effectively improved the quality of black and odorous water. In addition, the mechanism of nitrogen, phosphorus and carbon removal was proposed. [ABSTRACT FROM AUTHOR]

[Objective] This study aimed to investigate the effects of different tillage patterns and biochar addition on soil nitrogen and phosphorus transformation and maize growth and development in farmland in the black soil area. [Methods] Through a field experiment, two tillage treatments (deep tillage and shallow tillage) and five biochar addition treatments (0, 3, 6, 9, and 12 t/hm2) were set up to investigate the combined effects of different tillage patterns and biochar addition on soil nitrogen and phosphorus fractions, enzyme activities, and physiological characteristics of maize. [Results] (1) Deep tillage and shallow tillage in combination with biochar addition could effectively improve soil structure, increase the geometric mean diameter of agglomerates, and reduce the percentage of damage. The deep tillage treatment was more effective than the shallow tillage treatment. (2) The addition of biochar improved soil nitrogen-phosphorus fractions, urease activity, and alkaline phosphatase activity, and the effect of applying biochar at the rate of 9 t/hm2 was the best, which was more pronounced in the deep tillage treatment. (3) The application of biochar up to 9 t/hm2 under deep tillage treatment increased the total nitrogen and phosphorus contents and glutamine synthetase activity of leaves and decreased the acid phosphatase activity. (4) The yield of corn under deep tillage condition with the addition of 9 t/hm2 of biochar was as high as 17.37 t/hm2, which was increased by 28.9% compared with that of 0 of biochar. [Conclusion] The deep-tillage treatment and addition of 9 t/hm2 biochar provided a reference for the nutrient environment and crop growth in agricultural fields in the black soil area.

This study takes Guanshan River Basin, a typical inflow river of the Danjiangkou Reservoir, as the research area, and the nonpoint source (NPS) pollution characteristics of nitrogen and phosphorus from 2013 to 2018 were evaluated by establishing a Soil and Water Assessment Tool (SWAT) model. The pollution characteristics of heavy metals were also evaluated by combining the SWAT and simple output coefficient method. The results show that the pollutant load in Guanshan River Basin contributes significantly to the Danjiangkou Reservoir. Temporally, pollutant loads were primarily concentrated in the flood season, which had a significant positive correlation with precipitation, water yield, and sediments in the abundant period. Among them, sediments were the most important driving factor, followed by water yield. Spatially, pollutant loads were mainly concentrated downstream of the basin, where cultivated land is widespread. In this regard, it is suggested that the input of chemical fertilizers, pesticides, and livestock manure in cultivated land should be controlled and soil erosion downstream of the basin should be prevented to mitigate nitrogen, phosphorus, and heavy metal pollution. This research offers a basis for the formulation and implementation of watershed management for the Danjiangkou Reservoir. HIGHLIGHTS Based on the Soil and Water Assessment Tool model, the nonpoint source (NPS) pollution features and sources of nitrogen, phosphorus, and heavy metals were analyzed and discussed.; The NPS pollution is mainly concentrated in the flood season, and sediment is the most important driving factor, followed by water yield.; The input of fertilizers and pesticides into cultivated land should be controlled, and soil erosion should be prevented in the study's high-load area.;

Copyright of Journal of Ecology & Rural Environment is the property of Journal of Ecology & Rural Environment Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Global climate change is expected to have a significant impact on ecosystems worldwide, especially for alpine meadows which are considered as one of the most vulnerable components. However, the effects of global warming on the plant nitrogen–phosphorus stoichiometry and resorption in alpine meadows remain unclear. Therefore, to investigate the plant nitrogen–phosphorus stoichiometry and resorption in alpine meadows on the Qinghai-Tibet Plateau, we conducted an artificial warming study using open-top chambers (OTCs) over the 3 years of warming period. We selected three dominant species, four height types of OTCs (0.4, 0.6, 0.8 and 1 m) and four warming methods (year-round warming, winter warming, summer–autumn–winter warming and spring–summer–autumn warming in the experiment) in this experiment. In our study, soil temperature significantly increased with increasing the height of OCTs under the different warming methods. Kobresia pygmaea presented an increase in nitrogen (N) limitation and Kobresia humilis presented an increase in phosphorus (P) limitation with increasing temperature, while Potentilla saundersiana was insensitive to temperature changes in terms of nitrogen and phosphorus limitations. Both nitrogen resorption efficiency:phosphorus resorption efficiency and N:P trends in response to rising temperatures were in the same direction. The differential responses of the chemical stoichiometry of the three species to warming were observed, reflecting that the responses of nitrogen and phosphorus limitations to warming are multifaceted, and the grassland ecosystems may exhibit a certain degree of self-regulatory capability. Our results show that using chemical dosage indicators of a single dominant species to represent the nitrogen and phosphorus limitations of the entire ecosystem is inaccurate, and using N:P to reflect the nutritional limitations might have been somewhat misjudged in the context of global warming. [ABSTRACT FROM AUTHOR]

In the context of ever-increasing water demand and pressures on natural resources, efficient water management is becoming a major priority for contemporary society. Since nitrogen and phosphorus, as essential nutrients, play a crucial role in the dynamics of aquatic ecosystems, but excessive concentrations can cause eutrophication of receptors, they need to be eliminated as completely as possible while respecting the principles of a sustainable economy, efficiency, and quality. In this study, the efficiency of optimizing the technological process of wastewater treatment by dosing FeCl3 40% solution to reduce nitrogen and phosphorus concentrations in treated water was investigated. The results obtained revealed that the use of this type of flocculant resulted in an increase in the efficiency of the removal process of total N by an average of 35.57 mg/L and total P by an average of 3.89 mg/L. Also, the results, which are interpreted by mathematical modeling, show that the optimal use of FeCl3 40% solution leads to a significant reduction in pollutants, well below the maximum permitted values (according to Romanian regulations, the maximum value for total phosphorus is 2 mg/L and total nitrogen is 15 mg/L for localities with a population between 10,000 and 100,000 inhabitants). This technical approach not only improves the quality of treated water but also contributes to minimizing the impact on aquatic ecosystems and promotes the principles of circular economy in water resource management. By optimizing the dosage of FeCl3 40% solution in the treatment process, the efficiency of the coagulation and flocculation processes is maximized, thus providing a viable and sustainable solution for reducing the environmental impact of nitrogen and phosphorus and promoting responsible and sustainable water resource management. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Soil & Water Conservation (1009-2242) is the property of Institute of Soil & Water Conservation and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The surface soil of Xiashan Reservoir Basin was taken as the research object, and the leaching situation of total nitrogen (TN), total phosphorus (TP) and ammonia nitrogen (NH-N) under different leaching amounts was simulated by indoor soil column leaching method, and the release amount of nitrogen and phosphorus was predicted. The results showed that the TN, TP and NH3-N contents of cultivated land in this region were higher than those of forest land under different land use modes, but there was no significant difference. The leaching concentration of TN, TP and NH3-N showed significant positive correlation with the total amount in the soil. The concentration of TN in leaching solution decreased gradually with the increase of leaching amount, which indicated that the adsorption capacity of soil for TN was poor, and it was easy to lose with rainfall infiltration.TP and NH3-N did not change significantly with the increase of leaching amount, and their leaching intensity was lower than TN. Under the condition of a certain leaching amount, the leaching concentration of nitrogen and phosphorus was exponentially correlated with the volume of leaching solution. The leaching function of surface soil nutrients in Xiashan Reservoir Basin could be obtained by fitting the leaching concentration of nitrogen and phosphorus with the increase of leaching amount: C=C0eKV. The average annual release concentrations of TN, TP and NH3-N at the sampling points were simulated and calculated by the deterministic mathematical model to be 23.00,4.33 and 4.49 mg/L, respectively. The comprehensive nutritional status index of TN and TP annual release concentrations exceeded the standard for severe eutrophication in water body, which may lead to nitrogen and phosphorus enrichment in water through processes such as runoff. [ABSTRACT FROM AUTHOR]

Small mountainous rivers are characterized by large instantaneous fluxes and susceptible to extreme weather events, which can rapidly transport materials into the sea and have a significant impact on the ecological environment of estuaries and bays. In order to investigate the seasonal characteristics of nutrients in small mountainous rivers in the subtropical monsoon region and the output pattern to the sea during heavy precipitation, surveys on the mountainous rivers were carried out in Baixi watershed in August 2020 (wet season), March 2021 (dry season) and June 2021 (Meiyu period). The results showed that the dissolved inorganic nitrogen (DIN) of the rivers has an average concentration of 752 µg L−1 in the wet season and 1472 µg L−1 in the dry season. The concentrations of dissolved inorganic phosphorus (DIP) in wet season and dry season were 63 µg L−1 and 51 µg L−1, respectively. Influenced by the changes of land use in sub-watersheds, DIN concentrations in the mainstream increased from 701 µg L−1 in the upper reaches to 1284 µg L−1 in the middle reaches. Two rainstorms during the Meiyu period in the watershed caused the pulse runoff in the river. The maximum daily runoff reached 70 times that before rains. The maximum daily fluxes of DIN and DIP were 109 and 247 times that before rains, respectively. In view that the watershed experienced several rainstorms in the wet season, the river, with pulse runoff, carries a large amount of nutrients into the sea in a short time, which will have a significant impact on the environment of Sanmen bay and its adjacent sea. [ABSTRACT FROM AUTHOR]

Excessive nitrogen and phosphorus (N/P) input is the important reason for lake eutrophication, a widespread environmental problem that harms freshwater ecosystems worldwide. Land use land cover changes (LULCCs) strongly affect the migration and transformation process on land of N/P. Aiming to improve the accuracy of N/P estimation and deeply understand the spatiotemporal impact of LULCCs on N/P distribution, this study proposed an optimized framework, InVEST-UM, by integrating an unmixing algorithm with the conventional InVEST model. A comprehensive and intuitive index LPI (LULCCs purification capacity index) is developed for the impact assessment and spatialization. Validation shows a strong correlation (0.94) between the LPI and eutrophication degree of Dianshan Lake. This suggests the LPI effectively captures the spatiotemporal influence of LULCCs on lake eutrophication. Based on the sub-pixel results of N/P estimation, dramatic changes of LPI with an average rate of 46.182% were explored. There is a strong positive correlation (0.91) between vegetation area and LULCCs purification capacity for N/P. Conversely, negative relationships are found between LULCCs purification capacity with bare lands (−0.86), and artificial surfaces (−0.75). Changes in the water bodies have weak influence (−0.33) on LULCCs purification capacity. The increase in vegetation area can not only enhance the lake purification capacity, but also help maintain low ecological sensitivity. By employing this comprehensive framework, this study provides valuable insights into the long-term dynamics of LULCCs changes and their implications for lake ecosystems, and could support the protection and land use planning for the sustainability and ecological balance of the lake.

In this paper, a new type of slow-release algae control agent was prepared by using modified fly ash and cement as the base material and PS (potassium persulfate), an inorganic substance that dissolves algae by destroying their cellular structure, as the active component, and compounding the three in a certain proportion, and the finished product was obtained after 14 days of maintenance. The rate of release is primarily influenced by temperature, particle size, and load, while pH has minimal impact. Specifically, as the temperature increases from 4 °C to 40 °C, the rate of slow release increases from 0.74 mg/g/d to 1.35 mg/g/d. When particle size increased from 3 mm to 5 mm, the slow-release rate decreased from 1.06 mg/g/d to 0.70 mg/g/d. When the load increased from 10 mg/g to 30 mg/g, the slow-release rate also increased from 0.60 mg/g/d to 2.10 mg/g/d. In the algal inhibition experiment, the composite material was selected with a dose of 20 g/L, a loading capacity of 15 mg/g, and a particle size of 3 mm. After 14 days, algae removal rates, ammonia nitrogen, total phosphorus, and COD were found to be 96.55 %, 56.14 %, 78.2 %, and 86.81 %, respectively. The microstructure, elemental composition, and distribution of functional groups in the materials were analyzed using SEM, EDS, and FTIR. The algal suppressor was evenly distributed throughout the substrate surface. Additionally, there was a decrease in metal elements and an increase in hydroxyl groups. The experimental data show that the material is a slow-release algal inhibitor with good performance and practical application value.

Nitrogen (N) and phosphorus (P) play crucial roles in tea planting, but information on how the long-term excessive application of chemical N fertilizer affected N and P in subtropical tea plantations remains limited. In this study, soil and leaf samples were collected along a chronosequence of tea plantations (0-, 5-, 10-, 18- and 23-year-old plantations) with excessive N input but no P application to investigate the effects of planting age on N and P availability. Diverse soil N forms and P fractions, and the concentrations of leaf N and P were measured. The results showed that (1) N O 3 − -N and dissolved organic nitrogen (DON) concentrations in both topsoil and subsoil, and the N concentration of mature leaf showed significant upward trends with tea plantation age; (2) the concentrations of available phosphorus (AP), NaHCO3-Pi in labile P pool, NaOH-Pi and D.HCl-Pi in moderately labile P pool in both layers of soil and that the P concentration of mature leaf also increased with age; (3) the N concentration of mature leaves had closely significant logarithmic relations with N O 3 − -N concentration, while the TP (total P) concentration of mature leaves had significant positive correlations with AP; and (4) the ratio of N/P in tea leaves indicated a slightly P limitation in tea plantations. We concluded that the N O 3 − -N concentration, instead of TN (total N) of N H 4 + -N, would be a good indicator to reflect N availability for tea trees, and the increasing of N O 3 − -N concentration in soil has a diminishing promoting effect on the TN concentration of mature leaves. The long-term application of chemical N fertilizer had not lead to serious P limitation in subtropical tea plantations. Generally, our study could contribute to improving our understanding of N and P availability and optimizing fertilization management in subtropical tea plantations. [ABSTRACT FROM AUTHOR]

To investigate the actual effect of the bio-ecological combined treatment technology of rural domestic sewage, a combined process of regulating pond, biofilter, submersible constructed wetlands and ecological purification pond was built to monitor the water quality before and after sewage treatment. Seasonal characteristics of the removal rates were analyzed and the pollutant treatment characteristics of each unit were studied. The results show that their average removal rates of COD, TN, NH3 -N and TP are 87. 57%, 72. 18%, 80. 98% and 74. 54% respectively in summer, 77. 46%, 57. 52%, 64. 48% and 67. 03% in winter. There are significant seasonal differences in sewage treatment results in Guilin. The biofilter in the combined system has the largest contribution to COD and NH3 -N, while the constructed wetland has the largest contribution to the removal of TN and TP. Oxidation pond shows strong low-temperature stability in treatment of pollutants. The combined system shows a good performance on rural domestic sewage treatment in Guilin. Different from Guilin, the seasonal fluctuation of TN removal effect is large in Taihu Lake area affected by temperature and regional sewage discharge. Further promotion of the combined system should consider regional differences. [ABSTRACT FROM AUTHOR]

Simple Summary: In this study, we ask whether the invasive Datura stramonium bring about effects on native plants in three different habitats, including farmland, wasteland and roadside. Studying the invaded and uninvaded areas in these habitats, we found that the invasion of D. stramonium brought about corresponding effects on the functional traits of native plants and the stoichiometric characteristics of soil carbon, nitrogen and phosphorus. These findings imply that invasion by D. stramonium has a great effect on the local ecosystem, and it has a high ability to capture resources. D. stramonium can improve its own competitiveness by enhancing invasiveness by changing the functional traits of native plants and the stoichiometric characteristics of soil C, N and P, which may be the reason for its invasive success. Datura stramonium is an invasive herb of the family Solanaceae from Mexico and has been invading seriously in China. The effects of invasive plants on the functional traits of native plants and the stoichiometric characteristics of soil carbon, nitrogen and phosphorus in different habitats were explored by taking the invasive plant D. stramonium and coexisting native plants as the research object. The species, quantity and height of plants in sample plots in farmland, wasteland and roadside habitats were investigated and the specific leaf area (SLA), leaf carbon content (C), nitrogen content (N), carbon-to-nitrogen ratio (C:N), construction cost (CCmass) and stoichiometric characteristics of soil carbon (C), nitrogen (N) and phosphorus (P) were analyzed. The results showed that compared with the noninvaded area, the species and quantity of native plants decreased in the invaded area, and SLA and leaf N showed a decreasing trend. The plant height of native plants in the invaded area of the farmland and wasteland decreased by 23.19% and 15.26%, respectively, while the height of native plants along the roadside increased by 95.91%. The leaf C:N ratio of native plants in the invaded area along the roadside significantly increased by 54.07%. The plant height and leaf N of D. stramonium in the three habitats were higher than those of the native plants. The soil N in the invaded area of the three habitats increased, with the soil N in the farmland increasing by 21.05%, in the wasteland increasing by 9.82% and along the roadside significantly increasing by 46.85%. The soil carbon-to-phosphorus ratio (C:P) in the three habitats showed an increasing trend. The soil C:P ratio in the farmland increased by 62.45%, in the wasteland it increased by 11.91% and along the roadside it significantly increased by 71.14%. These results showed that invasion by D. stramonium has a great effect on the local ecosystem, and it has a high ability to capture resources. D. stramonium can improve its own competitiveness by enhancing invasiveness by changing the functional traits of native plants and the stoichiometric characteristics of soil C, N and P, which may be the reason for its invasive success. [ABSTRACT FROM AUTHOR]

This review paper describes different control applications for the A2/O process in sewage wastewater treatment plants. The contents elucidate the research carried out in the literature related to the design of different types of controllers for controlling different variables such as dissolved oxygen, nitrate, total suspended solids, ammonia, etc. that are responsible for the simultaneous removal of both nitrogen and phosphorus. A comprehensive analysis is carried out based on the important factors for the implementation of the control systems with critical discussion and achievements. Control strategies range from simple controllers such as proportional–integral (PI) to the latest (advanced) control approaches such as model-based predictive, fuzzy logic, artificial neural network, and optimal controllers. A distributed control system applied to the A2/O pilot plant is also elucidated. A summary of comparisons between different control systems are assessed and reported in this review. [ABSTRACT FROM AUTHOR]

Straw mulching (SM) is recognized as an effective management practice to alter soil nutrient translocation on the gentle slope arable land. The objective of this work was to evaluate the effects of straw mulching on soil nutrient content and microbial community. The two-year experiment involved six treatments: experiment slopes (3, 6, and 9°, 20 m long) and mulching (i.e. only maize straw (1.65 kg m−2) was mulched, and no mulch). Straw mulching treatments increased the levels of soil available nitrogen (AN), total nitrogen (TN), available phosphorus (AP), and total phosphorus (TP) at three different soil slopes. The AN content for 9° slopes straw mulching (NS) was 69.4% higher than 9° slopes no straw mulching (N), and also enhanced bacterial richness and diversity. The relative abundance of Proteobacteria and Bacteroidetes for NS were 48.3% and 76.7% larger than N treatment, respectively. Ascomycota was higher in 6° slopes straw mulching (55.3%) followed by NS (53.5%). In all, our findings showed that the application of straw mulching was a better approach for the restoration of slopy arable land (especially in arable land with high slope) fertility based on enhancing soil nutrient and microbial community. [ABSTRACT FROM AUTHOR]

Green algae are natural competitors of cyanobacteria, but we still do not know why green algae have a competitive advantage in shallow lakes. In this study, we used qPCR to quantify and monitor green algae and cyanobacteria in Longhu Lake. Our results showed that green algae were dominant in Longhu Lake, accounting for 71.80–80.31%. The temporal and spatial dynamics of green algal blooms were consistent with that of total organic nitrogen (TON), indicating that organic nitrogen may be the key trigger of green algal blooms. Nitrogen and phosphorus were excessive, and the peak of ammonia nitrogen occurred during the blooms, implying that ammonia nitrogen may be one of the important factors stimulating green algal blooms. Spearman correlation analysis and RDA analysis showed that green algae and cyanobacteria were positively correlated with water temperature, TON, and ammonia nitrogen, indicating that they have similar favorable growth conditions in Longhu Lake. Our results indicated that the combined effects of elevated water temperature, excessive nitrogen and phosphorus, non-stratification, and short water retention time could favor the competitive dominance of green algae in Longhu Lake. The findings here improve our understanding of the competition between green algae and cyanobacteria in shallow lakes. HIGHLIGHTS Green algae dominant cyanobacteria in a shallow lake, Longhu Lake.; Excessive TON might be the trigger of green algal blooms.; Excessive -N stimulated the overall outbreak of green algal blooms.; Excessive TN and TP may favor the dominating growth of green algae.; Short water rentention time may favor the dominance of green algae.;

Agricultural activities contribute significantly to the pollution of groundwater through the incomplete absorption of nitrogen (N) and phosphorus (P). Understanding the vertical migration patterns of N and P in soil solution is crucial for controlling groundwater quality. This study is based on monitoring data of soil solution nitrogen and phosphorus at different depths (30 cm, 60 cm, 100 cm) in the Huixian Wetland Experimental Area in the Li River Basin from March to December 2021. The vertical distribution patterns of nitrogen and phosphorus in soil solution in the study area are elucidated from three aspects: seasonal variations, karst types, and land use. The results indicate that the following: (1) NO3−-N is the predominant form of nitrogen, generally decreasing with increasing soil depth, while NH4+-N concentrations show slight increases and TP concentrations remain relatively stable. Overall, NO3−-N and TN concentrations tend to accumulate at 30 cm and 60 cm depths during both irrigation and non-irrigation seasons, with no distinct distribution patterns observed for NH4+-N and TP. (2) During the irrigation season, the migration distance of NO3−-N in non-karst landforms is mainly at 60 cm, while in peak forest plains, it is mainly at 100 cm, with no clear trend observed in NO3−-N concentrations in peak cluster depressions. In non-irrigation seasons, the distribution of NO3−-N content in non-karst landforms and peak cluster depressions is mainly 30 cm > 60 cm > 100 cm. The downward migration distance of NH4+-N generally follows the order of peak cluster depressions > peak forest plains > non-karst landforms. (3) During the irrigation season, NO3−-N concentrations in paddy fields remain relatively high at 100 cm, while in drylands, NO3−-N concentrations generally follow the pattern of 30 cm > 60 cm > 100 cm but may exhibit anomalous increases or decreases at 60 cm and 100 cm depths during heavy rainfall.

In the context of ever-increasing water demand and pressures on natural resources, efficient water management is becoming a major priority for contemporary society. Since nitrogen and phosphorus, as essential nutrients, play a crucial role in the dynamics of aquatic ecosystems, but excessive concentrations can cause eutrophication of receptors, they need to be eliminated as completely as possible while respecting the principles of a sustainable economy, efficiency, and quality. In this study, the efficiency of optimizing the technological process of wastewater treatment by dosing FeCl3 40% solution to reduce nitrogen and phosphorus concentrations in treated water was investigated. The results obtained revealed that the use of this type of flocculant resulted in an increase in the efficiency of the removal process of total N by an average of 35.57 mg/L and total P by an average of 3.89 mg/L. Also, the results, which are interpreted by mathematical modeling, show that the optimal use of FeCl3 40% solution leads to a significant reduction in pollutants, well below the maximum permitted values (according to Romanian regulations, the maximum value for total phosphorus is 2 mg/L and total nitrogen is 15 mg/L for localities with a population between 10,000 and 100,000 inhabitants). This technical approach not only improves the quality of treated water but also contributes to minimizing the impact on aquatic ecosystems and promotes the principles of circular economy in water resource management. By optimizing the dosage of FeCl3 40% solution in the treatment process, the efficiency of the coagulation and flocculation processes is maximized, thus providing a viable and sustainable solution for reducing the environmental impact of nitrogen and phosphorus and promoting responsible and sustainable water resource management.

【Objective】To study the removal effect of different woody plants on pollutants in mariculture wastewater, and to provide reference for the purification of mariculture wastewater by plants.【Method】Terminalia neotaliala Capuron and Buxus sinica were selected for hydroponic pot experiment to study the effects of different salinity (0 ‰, 2.5 ‰, 5 ‰, 7.5 ‰, 10 ‰, 15 ‰, 20 ‰) on the purification of mariculture wastewater.【Result】(1) The removal rates of TN and TP by T. neotaliala Capuron and B. sinica decreased with the increase of salinity, and the removal rate of COD fluctuated with the increase of salinity. The removal efficiency of TN and TP by T. neotaliala Capuron was higher than that of B. sinica. (2) Under different salinity conditions, the two plants had different absorption and removal effects on nitrogen and phosphorus. The accumulation of nitrogen showed the rule of underground > aboveground. The accumulation of phosphorus in T. neotaliala Capuron showed underground > aboveground at low salinity, while the accumulation of phosphorus in B. sinica fluctuated with the increase of salinity. The accumulation of nitrogen and phosphorus in T. neotaliala Capuron was higher than that in B. sinica. When the salinity was 0‰, 2.5‰, 5‰, 7.5‰, 10‰, 15‰, 20‰, the amount of nitrogen and phosphorus taken away by T. neotaliala Capuron absorption was 1.83 mg/g, 2.01 mg/g, 1.78 mg/g, 1.91 mg/g, 1.95 mg/g, 1.35 mg/g and 1.68 mg/ g, respectively. With the increase of salinity, the accumulation of K+ in T. neotaliala Capuron and B. sinica fluctuated greatly, while the accumulation of Na+ showed an increasing trend. When salinity > 2.5 ‰, the accumulation of Na+ showed the rule of aboveground > underground, and the increase of Na+ accumulation reduced the ability of plants to remove nitrogen and phosphorus. (3) pH, ORP, DO and other environmental factors have a certain influence on the removal of pollutants from sewage and the absorption of nitrogen, phosphorus, K+ and Na+ by plants.【Conclusion】The two plants have a certain removal effect on the pollutants of mariculture wastewater, and the purification effect is better than CK. The purification effect of T. neotaliala Capuron on mariculture wastewater is better than that of B. sinica. T. neotaliala Capuron can be preferentially selected for the treatment of mariculture wastewater.

The combination of the anaerobic digestion of waste biomass (e.g., livestock manure, energy crops and organic wastes) and the digestate treatment allows green energy to be obtained (starting from biogas/biomethane) and nutrients to be returned to the soil, satisfying the principles of the circular economy. Digestate has valuable potential as an organic fertilizer and soil amendment, as it can be an important source of nutrients, nitrogen and phosphorus (N and P), essential for crop growth. However, digestate production sometimes exceeds the capacity of nearby lands to use the nutrients. Therefore, the recovery of nutrients from digestate has become an important task for anaerobic digestion plants, to meet current regulations. In this study, a method combining struvite precipitation and ammonia stripping was tested in the laboratory to better understand the nutrient removal/recovery efficiency of the two nutrients. Results indicate that more than 60% of total P was removed as struvite, which can be used in N–P fertilizer, substituting synthetic mineral fertilizers.The recovery of N and P from digestate by struvite crystallization allows the removal of nutrient excess at farm level, reducing the environmental impacts of using slurry/digestate in agriculture. The recovery of struvite allows the production of a fertilizer that can be easily exported from farms, promoting the circular economy.

Small urban and rural rivers usually face heavy metal pollution as a result of urbanization and industrial and agricultural activities. To elucidate the metabolic capacity of microbial communities on nitrogen and phosphorus cycle in river sediments under different heavy metal pollution backgrounds, this study collected samples in situ from two typical rivers, Tiquan River and Mianyuan River, with different heavy metal pollution levels. The microbial community structure and metabolic capacity of nitrogen and phosphorus cycles of sediment microorganisms were analyzed by high-throughput sequencing. The results showed that the major heavy metals in the sediments of the Tiquan River were Zn, Cu, Pb, and Cd with the contents of 103.80, 30.65, 25.95, and 0.44 mg/kg, respectively, while the major heavy metals in the sediments of the Mianyuan River were Cd and Cu with the contents of 0.60 and 27.81 mg/kg, respectively. The dominant bacteria Steroidobacter, Marmoricola, and Bacillus in the sediments of the Tiquan River had positive correlations with Cu, Zn, and Pb while are negatively correlated with Cd. Cd had a positive correlation with Rubrivivax, and Cu had a positive correlation with Gaiella in the sediments of the Mianyuan River. The dominant bacteria in the sediments of the Tiquan River showed strong phosphorus metabolic ability, and the dominant bacteria in the sediments of the Mianyuan River showed strong nitrogen metabolic ability, corresponding to the lower total phosphorus content in the Tiquan River and the higher total nitrogen content in the Mianyuan River. The results of this study showed that resistant bacteria became dominant bacteria due to the stress of heavy metals, and these bacteria showed strong nitrogen and phosphorus metabolic ability. It can provide theoretical support for the pollution prevention and control of small urban and rural rivers and have positive significance for maintaining the healthy development of rivers. [ABSTRACT FROM AUTHOR]

Copyright of China Rural Water & Hydropower is the property of China Rural Water & Hydropower Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Nitrogen (N) and phosphorus (P) play crucial roles in tea planting, but information on how the long-term excessive application of chemical N fertilizer affected N and P in subtropical tea plantations remains limited. In this study, soil and leaf samples were collected along a chronosequence of tea plantations (0-, 5-, 10-, 18- and 23-year-old plantations) with excessive N input but no P application to investigate the effects of planting age on N and P availability. Diverse soil N forms and P fractions, and the concentrations of leaf N and P were measured. The results showed that (1) NO3−-N and dissolved organic nitrogen (DON) concentrations in both topsoil and subsoil, and the N concentration of mature leaf showed significant upward trends with tea plantation age; (2) the concentrations of available phosphorus (AP), NaHCO3-Pi in labile P pool, NaOH-Pi and D.HCl-Pi in moderately labile P pool in both layers of soil and that the P concentration of mature leaf also increased with age; (3) the N concentration of mature leaves had closely significant logarithmic relations with NO3−-N concentration, while the TP (total P) concentration of mature leaves had significant positive correlations with AP; and (4) the ratio of N/P in tea leaves indicated a slightly P limitation in tea plantations. We concluded that the NO3−-N concentration, instead of TN (total N) of NH4+-N, would be a good indicator to reflect N availability for tea trees, and the increasing of NO3−-N concentration in soil has a diminishing promoting effect on the TN concentration of mature leaves. The long-term application of chemical N fertilizer had not lead to serious P limitation in subtropical tea plantations. Generally, our study could contribute to improving our understanding of N and P availability and optimizing fertilization management in subtropical tea plantations.

Considerable time and funding have been committed to tackling nonpoint source (NPS) pollution in agricultural and urban watersheds . Notwithstanding all these efforts, the water quality in many AUWs has not significantly improved. Diffuse nutrient pollution involves the movement of these pollutants between soil and water. Excessive diffuse pollution has been accepted as one of the main causes of failure to attain favorable environmental conditions in freshwater systems. Recently, several technologies and practices have been implemented to manage diffuse pollution, namely: a) source reduction, b) pollutant retention over the movement process; c) nutrient recycling, and d) purification and restoration of the eutrophic water bodies. This paper synthesized the existing knowledge of key methods to tackle diffuse pollution from AUWs. Furthermore, the predominant purification mechanisms and impacting factors are explored, allowing a comprehensive and critical understanding of different control strategies to improve the management of diffuse pollution. Therefore, potential approaches for strengthening the performance of control technologies for diffuse pollution treatment and remediation are discussed. Although adopting source reduction strategies (e.g., the “4R” approach: right rate, right time, right source, and right placement of nutrients) could efficiently decrease surface runoff and pollutant levels, they may not stop runoff from entering nearby streams. Consequently, comprehensive treatment of agricultural runoff still requires extra process retention strategies. Overall, the findings of this paper showed that treatment system design and operational and environmental factors played crucial but variable roles in diffuse pollution treatment. Moreover, the results showed that combining or integrating constructed wetlands with other control technologies could enhance the comprehensive purification of diffuse pollution compared to using a single method. This review proposes a systematic approach for diffuse pollution control based on three components (water, soil and microbiota) and maximizing the regulating services of agroecosystems via land use/cover types. The current review contributes to the documentation of existing research trends. It sheds light on diffuse pollution control approaches in AUWs, and further encourages the development of this vital field.

Ecological concrete (eco-concrete) is a kind of environment-friendly material with porous characteristics. In this study, the eco-concrete was used to remove the total nitrogen (TN), total phosphorus (TP), and total organic carbon (TOC) in marine coastal sediment. The bacterial communities in sediment and on eco-concrete surface were also investigated by using high-throughput sequencing and quantitative PCR of 16S rRNA gene. We found that the mean removal efficiencies of TN, TP, and TOC in treatment group were 8.3%, 8.4%, and 12.3% after 28 days. The bacterial community composition in the treatment group was significantly different from that in the control group on day 28. In addition, the bacterial community composition on eco-concrete surface was slightly different from that in sediment, and the copy numbers of 16S rRNA gene were higher on eco-concrete surface than in sediment. The types of eco-concrete aggregates (gravel, pebble, and zeolite) also had effects on the bacterial community composition and 16S rRNA gene copy numbers. Furthermore, we found the abundant genus Sulfurovum increased significantly on eco-concrete surface in the treatment group after 28 days. Bacteria belonging to this genus were found having denitrification ability and were commonly detected in bioreactors for nitrate removal. Overall, our study expands the application scopes of eco-concrete and suggests that the bacterial communities in eco-concrete can potentially enhance the removal efficiency of nutrients in coastal sediment. [ABSTRACT FROM AUTHOR]

[Objective] To study the removal effect of different woody plants on pollutants in mariculture wastewater, and to provide reference for the purification of mariculture wastewater by plants.[Method] Terminalia neotaliala Capuron and Buxus sinica were selected for hydroponic pot experiment to study the effects of different salinity ( 0 ‰, 2.5 ‰, 5 ‰, 7.5 ‰, 10 ‰, 15 ‰, 20 ‰ ) on the purification of mariculture wastewater. [Result] (1) The removal rates of TN and TP by T. neotaliala Capuron and B. sinica decreased with the increase of salinity, and the removal rate of COD fluctuated with the increase of salinity. The removal efficiency of TN and TP by T. neotaliala Capuron was higher than that of B. sinica. (2) Under different salinity conditions, the two plants had different absorption and removal effects on nitrogen and phosphorus. The accumulation of nitrogen showed the rule of underground > aboveground. The accumulation of phosphorus in T. neotaliala Capuron showed underground > aboveground at low salinity, while the accumulation of phosphorus in B. sinica fluctuated with the increase of salinity. The accumulation of nitrogen and phosphorus in T. neotaliala Capuron was higher than that in B. sinica. When the salinity was 0‰, 2.5‰, 5‰, 7.5‰, 10‰, 15‰, 20‰, the amount of nitrogen and phosphorus taken away by T. neotaliala Capuron absorption was 1.83 mg/g, 2.01 mg/g, 1.78 mg/g, 1.91 mg/g, 1.95 mg/g, 1.35 mg/g and 1.68 mg/ g, respectively. With the increase of salinity, the accumulation of K+ in T. neotaliala Capuron and B. sinica fluctuated greatly, while the accumulation of Na+ showed an increasing trend. When salinity > 2.5 ‰, the accumulation of Na+ showed the rule of aboveground > underground, and the increase of Na+ accumulation reduced the ability of plants to remove nitrogen and phosphorus. (3) pH, ORP, DO and other environmental factors have a certain influence on the removal of pollutants from sewage and the absorption of nitrogen, phosphorus, K+ and Na+ by plants. [Conclusion] The two plants have a certain removal effect on the pollutants of mariculture wastewater, and the purification effect is better than CK. The purification effect of T. neotaliala Capuron on mariculture wastewater is better than that of B. sinica. T. neotaliala Capuron can be preferentially selected for the treatment of mariculture wastewater. [ABSTRACT FROM AUTHOR]

Understanding the seasonal variation characteristics of nitrogen and phosphorus nutrients in the reservoir can effectively prevent water eutrophication, which is very important to ensure that the water quality meets the standard. In order to explore the impact of the development of Shanxi In order to explore the impact of the development of Shanxi water control project on the concentration of nitrogen and phosphorus nutrients in the reservoir water, in this study Zhaoshandu reservoir and Shanxi In this study Zha-oshandu reservoir and Shanxi reservoir was selected as the research objects, the water quality indicators of the reservoir water was investigated in different months from March 2020 to February 2021. The different occurrence forms of N and P and the seasonal variation characteristics of TN/TP was analyzed, and further the principal component analysis (PCA) was The results showed that: (1) the concentration of TN in Zhaoshandu reservoir ranged from 0.67 to 1.24 mg/L, with an average of 0.86 mg/L, the concentration of NH3- N ranged from 0.00 to 0.15 mg/L, with an average of 0.055 mg/L, the The concentration of TN in Shanxi reservoir ranged from 0.50 to 0.67 mg/l, with an average of 0.57 mg/L. The concentration of NH3- N ranged from 0.00 to 0.15 mg/L, with an average of 0.055 mg/L, the concentration of NO- N ranged from 0.45 to 0.84 mg/L, The concentration of NH3- N ranged from 0.030 to 0.095 mg/L, with an average of 0.058 mg/L, and the concentration of NO3- -N ranged from 0.17 to 0.37 mg/L, with an average of 0.29 mg/L. The content of nitrogen of Zha-oshandu reservoir located in the downstream was higher than that of Shanxi reservoir, and the nitrogen The content of nitrogen of Zhaoshandu reservoir located in the downstream was higher than that of Shanxi reservoir, and the nitrogen in Zhaoshandu reservoir was high in spring and low in winter, and Shanxi reservoir was high in winter differently. (2) In Zhaoshandu reservoir, the concentration of TP ranged from 0.02 to 0.05 mg/L, and that in Shanxi reservoir was 0-0.0235 mg/L. Similarly, the content of TP in both reservoirs was (3) During the study period, most of the time of Zhaoshandu reservoir was the suitable period for algae growth, and a few times the water (4) The concentration of nitrogen and phosphorus in Zhaoshandu reservoir and Shanxi reservoir was related to the potential biological toxicity, the concentration of (4) The concentration of nitrogen and phosphorus in Zhaoshandu reservoir and Shanxi reservoir was related to the potential biological toxicity, the concentration of exogenous organic pollutants and the amount of suspended solids of plankton. In addition, the weather and temperature had a certain impact on the concentration of nitrogen and phosphorus in Shanxi reservoir. This study could provide protection suggestions for water pollution prevention and control of Shanxi reservoir according to its water quality characteristics. [ABSTRACT FROM AUTHOR]

【Objective】The study was carried out to reveal the impact of long-term fertilization on the capacities of soil nitrogen (N) and phosphorus (P) activation, and their correlations with pH and soil organic carbon (SOC) in purple paddy soil with different fertility, with a view to providing references for soil fertilization.【Method】Based on a 36-year different fertilization experiment of purple soil, different fertilization treatments including no fertilization (LF), balanced chemical nitrogen (N), phosphorus (P) and potassium (K) fertilizer (MF), and chemical N, P and K fertilizer plus organic fertilizer (HF) were set. Dynamics of soil total and available N and P contents, and nutrient activation rates under different fertility were measured, and relationships between soil pH, SOC and nutrient activation rates were analyzed.【Result】Crop yields under MF and HF were significantly higher than those under LF. The contents of total N and P had no significant changes, available N content efficiently improved, while available P slightly decreased under LF treatment. However, total and available N and P contents significantly increased under MF and HF treatments. There were variation in promotion of N and P content under different fertility paddy soil. For example Under LF, MF, and HF treatments, the annual increase rates of total N contents were 5.5, 14.2, and 17.0 mg/kg, 0.40, 1.05, and 1.32 mg/kg for available N, 0.8, 17.1, and 18.0 mg/kg for total P, and -0.03, 2.05, and 1.85 mg/kg for available P, respectively. Compared with the LF treatment, N activation rates under MF and HF treatments increased from 8.15% to 428.77%. There was no significant linear relationship between N activation rate and pH or SOC. A significant negative correlation was observed between P activation rate and pH, while there was a significant positive linear correlation between P activation rate and SOC. If the annual application amount of N was 240 kg/hm2 and amount of P2O5 was 120 kg/hm2, the purple soil was N-saturated after 13 years and it was P-saturated after 9 years.【Conclusion】In the purple paddy soil regions of Southwest China, balanced fertilization with N, P and K or application of chemical fertilizer with organic fertilizer could promote soil N and P contents and activation rates.

The role of endogenous phytohormones, nitric oxide (NO), and nitrogen (N) starvation on scavenging and remobilization of phosphorous (P) from root cell wall pectin was studied on dual-nutrient stress (DNS) tolerant (HD-2781) and sensitive (C-306) bread wheat genotypes. Plants were grown in hydroponics with low concentrations of N and P, their combined stress, and recovery from stress conditions. Results revealed that P remobilization from roots was higher in HD-2781 under nutrient stress and recovery conditions than C-306. In general, the hydrolysis of pectin and remobilization of P from root cell walls increased under low P, DNS, and recovery treatments but no effect of N was noted. In the roots, endogenous ethylene and auxin concentrations were significantly higher indicating enhanced adaptive response to low P and DNS. However, an enhanced ABA concentration in C-306 was also observed which may have an inhibitory effect on P remobilization from pectin. The cross-talk between ethylene, auxin, and NO stimulated pectin methyl esterase enzyme activity thereby, leading to an increased cell wall P scavenging and its transport to shoot as evident from the upregulation of TaPT8 gene. The low P and DNS treatments also induced ethylene and NO biosynthetic genes, TaACS2 and TaNOS, respectively. Thus, NO, ethylene, and auxin-stimulated PME activity leading to enhanced release of P from the root cell wall pectin independent of N treatment. We provided sufficient evidence that the root cell wall P remobilization is one of the low P adaptive mechanisms in P stress-tolerant wheat genotype. However, the cross-talk between hormones and signalling molecules, and their regulatory mechanism on PME enzyme activity needs to be studied. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Nanchang University (Engineering & Technology) is the property of Nanchang University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Microalgae can survive and proliferate in waste water containing high-concentration nitrogen and phosphate from municipal or agricultural sewage, as well as absorb and assimilate for NH4+-N and PO43--P. The cultivation of microalgae in immobilization has more significant strength than in suspension. The experiment set the same culture environment and imitated artificial sewage of nitrogen and phosphate using ammonium chloride and monopotassium phosphate, thus the growth rate and the removal rate of nitrogen and phosphorus of suspended and immobilized marine microalgae (Chaetoceros muelleri, Chlorella pyrenoidosa, Phaeodactylum tricornutum and Nitzschia closterium) were compared. The results showed that these microalgae could grow in suspended and immobilized cultivation, and had superior removal efficiencies of NH4+-N and PO43--P. The growth rate of these marine microalgae in suspended was better than in immobilized. The growth rates of the two culture methods: Chlorella pyrenoidosa > Nitzschia closterium > Phaeodactylum tricornutum > Chaetoceros muelleri. The removal rates of NH4+-N and PO43--P in suspended were as follows: Nitzschia closterium > Phaeodactylum tricornutum > Chaetoceros muelleri > Chlorella pyrenoidosa; the removal rates of NH4+-N-N and PO43--P in immobilized were as follows: Nitzschia closterium > Phaeodactylum tricornutum > Chlorella pyrenoidosa > Chaetoceros muelleri. Except Chaetoceros muelleri, the removal rates of NH4+-N-N in immobilized including Nitzschia Closterium, Phaeodactylum tricornutum and Chlorella pyrenoidosa were better than those of suspension cultivation. The removal of PO43--P in immobilized had higher efficiencies than in suspended. In summary, the growth rates and removal rates of NH4+-N-N and PO43--P were inferior to in the immobilized culture. Nitzschia Closterium exhibited enormous advantages in growing and removal rates of NH4+-N and PO43--P under immobilization. [ABSTRACT FROM AUTHOR]

Copyright of Environmental Science & Technology (10036504) is the property of Editorial Board of Environmental Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Summary: N-enriched biochar can increase the accumulation of carbon (C), nitrogen (N), phosphorus (P), and biomass in rice plants. On the other hand, the biomass and C, N, and P contents of plant organs are important indicators to reflect plant C, N, and P storages. We established control, 4 t ha−1, and 8 t ha−1 N-enriched biochar treatment plots in a subtropical paddy field in China to investigate the effect of these treatments on C, N, and P storages, ecological stoichiometry in various rice plant organs, and their relationships with edaphic factors. The application of N-enriched biochar increased the biomass and storages of C, N, and P in rice roots, stems, leaves, and grains, mainly at 4 t ha−1. The application of N-enriched biochar decreased the C/N and C/P ratios of rice organs, but increased their N/P ratio. Changes in C/N were mainly due to the changes in storage, while N/P was positively correlated with N storage of stems, leaves, and grains and negatively correlated with P storage in roots. Pearson's correlation analysis revealed that pH was negatively correlated, and soil N content was positively correlated with P storage in various organs of rice. In addition, soil P content and chlorophyll were positively correlated with N storage. In conclusion, we found that the application of N-enriched biochar improved plant N and P storage and stoichiometrical relations among rice organs. [ABSTRACT FROM AUTHOR]

Vegetation in arid desert areas plays an extremely important role in maintaining biodiversity and inhibiting desertification. Quantitative understanding of vegetation response to groundwater is essential to priming drought prevention and mitigation, which is a topic that is attracting considerable attention. However, previous studies have rarely assessed the response of vegetation to groundwater from probabilistic or stoichiometric chemical perspective. To address this question, a highly sensitive copula joint distribution of the response of enhanced vegetation index (EVI) loss to groundwater was constructed and a stoichiometric chemistry indicator of the Nitrogen (N) and Phosphorus (P) concentrations in tree rings was innovatively put forward to verify its sensitivity to groundwater. The results obtained revealed that the correlation of EVI with groundwater was better than that with SPEI and TVDI; Furthermore, the critical groundwater thresholds of the EVI loss rate, described as “beginning”, “reaching the maximum”, and “the slowest” were 3.85 m, 6.18–6.75 m, and 7.89 m, respectively. At the inter-annual scale, by measuring the N and P contents of Populus euphratica tree rings, and constructing response model of element contents to groundwater/rainfall, the key thresholds were determined at 5.20–5.31 m and 60 mm, which challenges the traditional understanding that rainfall does not bring ecological benefits to desert riparian forests. To further promote vegetation restoration, based on the response rule of EVI loss and stoichiometric chemical elements of tree rings to groundwater and the intermediate overflow rotation irrigation method, a more advanced desert riparian forest irrigation mode, named “branch-infiltration-rotation-irrigation”, is here proposed.

Datura stramonium is an invasive herb of the family Solanaceae from Mexico and has been invading seriously in China. The effects of invasive plants on the functional traits of native plants and the stoichiometric characteristics of soil carbon, nitrogen and phosphorus in different habitats were explored by taking the invasive plant D. stramonium and coexisting native plants as the research object. The species, quantity and height of plants in sample plots in farmland, wasteland and roadside habitats were investigated and the specific leaf area (SLA), leaf carbon content (C), nitrogen content (N), carbon-to-nitrogen ratio (C:N), construction cost (CCmass) and stoichiometric characteristics of soil carbon (C), nitrogen (N) and phosphorus (P) were analyzed. The results showed that compared with the noninvaded area, the species and quantity of native plants decreased in the invaded area, and SLA and leaf N showed a decreasing trend. The plant height of native plants in the invaded area of the farmland and wasteland decreased by 23.19% and 15.26%, respectively, while the height of native plants along the roadside increased by 95.91%. The leaf C:N ratio of native plants in the invaded area along the roadside significantly increased by 54.07%. The plant height and leaf N of D. stramonium in the three habitats were higher than those of the native plants. The soil N in the invaded area of the three habitats increased, with the soil N in the farmland increasing by 21.05%, in the wasteland increasing by 9.82% and along the roadside significantly increasing by 46.85%. The soil carbon-to-phosphorus ratio (C:P) in the three habitats showed an increasing trend. The soil C:P ratio in the farmland increased by 62.45%, in the wasteland it increased by 11.91% and along the roadside it significantly increased by 71.14%. These results showed that invasion by D. stramonium has a great effect on the local ecosystem, and it has a high ability to capture resources. D. stramonium can improve its own competitiveness by enhancing invasiveness by changing the functional traits of native plants and the stoichiometric characteristics of soil C, N and P, which may be the reason for its invasive success.

The annual inputs of nitrogen and phosphorus by the Narva river into the Baltic Sea are distributed between Estonia and Russia according to the catchment area shares of 33% and 67%, respectively [...]

In this paper, a new type of particle-modified fly ash composite material was prepared using fly ash as the main raw material, which could immobilize nitrogen and phosphorus pollutants in sediment and control its release into water. Preliminary modification of fly ash was achieved by soaking in NaOH and calcining at high temperature of CaO. The modified fly ash was mixed with four auxiliary materials, namely cement, slag, water glass and quartz sand, and was formed after 14 days of curing. X-ray diffraction (XRD) and scanning electron microscope-energy dispersive spectrometer (SEM-EDS) were used to examine the material microstructure, element composition, crystal mineral changes, and also to further examine the physical indicators and mechanical properties of the material. In the end, we chose to use modified fly ash composite 10% cement to make granular modified fly ash composite materials. Taking the actual polluted river sediment as the research object, a 22-day coverage effect experiment was carried out, and it was finally found that the 2 cm-thick modified fly ash composite material cover layer inhibited the ammonia nitrogen (NH4+-N)、total nitrogen (TN) and total phosphorus (TP) of the sediments at 90.91%, 75.06% and 90.63%, respectively. This confirms that it is a material with good performance and practical application value. HIGHLIGHTS Realized the composite of multiple materials.; The microscopic characterization and crystal phase of the material are analyzed in detail.; Provide mechanical and physical indicators of materials.; Carried out the practical application experiment of sediment pollutant suppression.; It is a granular fly ash material with low cost, small particle size, high strength and good adsorption.;

Nitrogen (N) and phosphorus (P) concentrations are the fundamental factors affecting the nutrient status and productivity of lakes, and extrinsic inputs of N and P primarily cause eutrophication of lakes. In this essay, taking Hongze Lake as the study area, a two-dimensional hydrodynamic and water quality mathematical model of Hongze Lake was constructed, and based on calibration and verification of parameters, numerical simulation was performed on the changes in N and P concentrations in this lake after water transfer. The study results exhibited that before and after project construction, the absolute values of rates of changes in the annual average concentrations of ammonia nitrogen (NH4+-N), total phosphorus (TP), total nitrogen (TN), and permanganate index (CODMn) in Hongze Lake were all lower than 20%, which demonstrates marginal changes in the annual average concentrations. By analyzing the seasonal and spatial distribution characteristics of the concentrations of N, P and other pollutants in the lake area before and after the project operation, it is found that the main reasons that affect the water quality change in the lake area after the project operation are the newly added water transfer volume, water transfer location, and water transfer quality. HIGHLIGHTS In this paper, a hydrodynamic-transport water quality coupling model was constructed.; According to the results of model operation, after operations of the second phase of the eastern route project, the subject is the most serious pollution.; Factors affecting the water quality in the lake can be explained in two aspects.;

Microplastics (MPs) have been proven to be one of the major threats to the wastewater treatment system. However, the impact of MPs on microalgae-based wastewater treatment technology are still unknown. In this study, effects of polyvinyl chloride (PVC), polypropylene (PP), and polyethylene (PE) on the removal of nitrogen and phosphorus from synthetic piggery digestate by microalgae were investigated. Results show that the effect of PVC particle size on the growth of microalgae was significant. The effects of PVC content, PP particle size and content, PET particle size and content on the growth of microalgae were all not significant. The removal of ammonia nitrogen by microalgae was influenced significantly by PVC particle size and content, PP particle size and content, the effects of PET particle size and content on the removal of ammonia nitrogen were all not significant. The effects of particle size and content for three MPs on the removal of total phosphorus were all significant. Microalgae cells were bound together after being adsorbed by MPs, which increased the secretion of extracellular polymers and influenced the removal of ammonia nitrogen and total phosphorus. [ABSTRACT FROM AUTHOR]

The risks posed by algal blooms caused by nitrogen and phosphorus in reclaimed water used in urban water landscapes need to be carefully controlled. In this study, the combined effects of the nitrogen and phosphorus concentrations and the light intensity and temperature on the specific growth rates of algae were determined using Monod, Steele, and Arrhenius models, then an integrated algal growth model was developed. The algae biomass, nitrogen concentration, and phosphorus concentration mass balance equations were used to establish a new control model describing the nitrogen and phosphorus concentration and hydraulic retention time thresholds for algal blooms. The model parameters were determined by fitting the models to data acquired experimentally. Finally, the control model and numerical simulations for six typical algae and mixed algae under standard conditions were used to determine nitrogen/phosphorus concentration and hydraulic retention time thresholds for landscape water to which reclaimed water is supplied (i.e., for a reclaimed water landscape). [ABSTRACT FROM AUTHOR]

A novel phosphorus- and nitrogen-containing flame retardant (APNTHE) was synthesized through the reaction of N, N, N ′, N ′-tetrakis (2-hydroxypropyl) ethylenediamine, phosphoric acid and urea. Then, the APNTHE solution with a concentration of 120 g/L was used for the preparation of flame retardant cotton (FR-cotton). The elemental compositions, surface morphology, thermal stability and combustion behavior of the cotton before and after modification were investigated. Thermogravimetric (TG) analysis showed that the char residue of the treated fabric at 800°C was as high as 35.09% under a nitrogen atmosphere. Flammability tests after different LCs indicated that FR-cotton had durable flame retardancy. Compared to the blank sample, the peak of heat release rate and total heat release of the FR-cotton decreased by 91.89% and 90.53%, respectively. The char residual and TG-Fourier transform infrared spectroscopy analysis illustrated that APNTHE played a flame retardant role both in the gas phase and the condensed phase. All the results demonstrated that APNTHE can be regarded as a prospective flame retardant for cotton. [ABSTRACT FROM AUTHOR]

Copyright of China Rural Water & Hydropower is the property of China Rural Water & Hydropower Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Intercropping of maize (Zea mays L.) and peanut (Arachis hypogaea L.) often results in greater yields than the respective sole crops. However, there is limited knowledge of aboveground and belowground interspecific interactions between maize and peanut in field. A two-year field experiment was conducted to investigate the effects of interspecific interactions on plant growth and grain yield for a peanut/maize intercropping system under different nitrogen (N) and phosphorus (P) levels. The method of root separation was employed to differentiate belowground from aboveground interspecific interactions. We observed that the global interspecific interaction effect on the shoot biomass of the intercropping system decreased with the coexistence period, and belowground interaction contributed more than aboveground interaction to advantages of the intercropping in terms of shoot biomass and grain yield. There was a positive effect from aboveground and belowground interspecific interactions on crop plant growth in the intercropping system, except that aboveground interaction had a negative effect on peanut during the late coexistence period. The advantage of intercropping on grain came mainly from increased maize yield (means 95%) due to aboveground interspecific competition for light and belowground interaction (61%–72% vs. 28%–39% in fertilizer treatments). There was a negative effect on grain yield from aboveground interaction for peanut, but belowground interspecific interaction positively affected peanut grain yield. The supply of N, P, or N + P increased grain yield of intercropped maize and the contribution from aboveground interspecific interaction. Our study suggests that the advantages of peanut/maize intercropping for yield mainly comes from aboveground interspecific competition for maize and belowground interspecific facilitation for peanut, and their respective yield can be enhanced by N and P. These findings are important for managing the intercropping system and optimizing the benefits from using this system.

Yield performance in cereal and legume intercropping is related to nutrient management, however, the yield response of companion crops to nitrogen (N) input is inconclusive and only limited efforts have focused on rationed phosphorous (P) fertilization. In this study, two multi-year field experiments were implemented from 2014–2019 under identical conditions. Two factors in a randomized complete block design were adopted in both experiments. In field experiment 1, the two factors included three planting patterns (mono-cropped wheat (MW), mono-cropped faba bean (MF), and wheat and faba bean intercropping (W//F)) and four N application rates (N0, 0 kg N ha–1; N1, 90 and 45 kg N ha–1 for wheat and faba beans, respectively; N2, 180 and 90 kg N ha–1 for wheat and faba beans, respectively; and N3, 270 and 135 kg N ha–1 for wheat and faba beans, respectively). In field experiment 2, the two factors included three P application rates (P0, 0 kg P2O5 ha–1; P1, 45 kg P2O5 ha–1; and P2, 90 kg P2O5 ha–1) and the same three planting patterns (MW, MF, and W//F). The yield performances of inter- and mono-cropped wheat and faba beans under different N and P application rates were analyzed and the optimal N and P rates for intercropped wheat (IW) and MW were estimated. The results revealed that intercropping favored wheat yield and was adverse to faba bean yield. Wheat yield increased by 18–26%, but faba bean yield decreased by 5–21% in W//F compared to MW and MF, respectively. The stimulated IW yield drove the yield advantage in W//F with an average land equivalent ratio (LER) of 1.12. N and P fertilization benefited IW yield, but reduced intercropped faba bean (IF) yield. Nevertheless, the partial LER of wheat (pLERwheat) decreased with increasing N application rates, and the partial LER of faba bean (pLERfaba bean) decreased with increasing P application rates. Thus, LER decreased as N input increased and tended to decline as P rates increased. IW maintained a similar yield as MW, even under reduced 40–50% N fertilizer and 30–40% P fertilizer conditions. The estimated optimum N application rates for IW and MW were 150 and 168 kg ha–1, respectively, and 63 and 62 kg ha–1 for P2O5, respectively. In conclusion, W//F exhibited yield advantages due to stimulated IW yield, but the intercropping yield benefit decreased as N and P inputs increased. Thus, it was concluded that modulated N and P rates could maximize the economic and ecological functions of intercropping. Based on the results, rates of 150 kg Nha–1 and 60 kg P2O5 ha–1 are recommended for IW production in southwestern China and places with similar conditions.