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Colloidal phosphorus (P), defined as P associated with particles within the size range from 1 to 1000 nm, is an often-neglected yet significant component of waterborne P, posing global water quality concerns. This comprehensive review elucidates the various sources and concentrations of colloidal P across diverse water environments, highlighting its prominence in agricultural wastewater, with mean concentrations of 122.6 μg/L (n = 437), compared to groundwater (52.3 μg/L, n = 26), surface freshwater (22.3 μg/L, n = 246), and seawater (5.4 μg/L, n = 36). Correlations between physicochemical water parameters, elemental composition and colloidal P concentrations are obtained, and the dominant subfractions and chemical species of colloidal P in water are identified. Notably from chemical speciation, colloidal organic P exhibits dominance in surface freshwater with higher abundance relative to colloidal inorganic P. Meanwhile, statistical analyses on physical fractions of colloidal P indicate that fine subfractions prevail in agricultural wastewater. Accordingly, this review investigates potential transformation mechanisms of colloidal P due to physical and chemical behaviors such as aggregation, desorption, and photodegradation, influenced by factors such as pH, salinity, coexisting elements and UV irradiation. Drawing on these insights, we propose eco-friendly mitigation strategies, including constructed wetlands or ecological drainage ditches and UV irradiation, aimed at treating water (especially agricultural wastewater) with elevated colloidal P levels. This review not only enhances our understanding of the occurrence and transformations of colloidal P, but also offers practical guidance for its effective environmental management. [ABSTRACT FROM AUTHOR]

The widespread environmental contamination resulting from the misuse of tetracycline antibiotics (TCs) has garnered significant attention and study by scholars. Photocatalytic technology is one of the environmentally friendly advanced oxidation processes (AOPs) that can effectively solve the problem of residue of TCs in the water environment. This study involved the synthesis of the heterogeneous magnetic photocatalytic material of CoFe2O4/NaBiO3 via the solvothermal method, and it was characterized using different characterization techniques. Then, the photocatalytic system under visible light (Vis) was coupled with peroxymonosulfate (PMS) to explore the performance and mechanism of degradation of tetracycline hydrochloride (TCH) in the wastewater. The characterization results revealed that CoFe2O4/NaBiO3 effectively alleviated the agglomeration phenomenon of CoFe2O4 particles, increased the specific surface area, effectively narrowed the band gap, expanded the visible light absorption spectrum, and inhibited recombination of photogenerated electron–hole pairs. In the Vis+CoFe2O4/NaBiO3+PMS system, CoFe2O4/NaBiO3 effectively activated PMS to produce hydroxyl radicals (·OH) and sulfate radicals (SO4−). Under the conditions of a TCH concentration of 10 mg/L−1, a catalyst concentration of 1 g/L−1 and a PMS concentration of 100 mg/L−1, the degradation efficiency of TCH reached 94% after 100 min illumination. The degradation of TCH was enhanced with the increase in the CoFe2O4/NaBiO3 and PMS dosage. The solution pH and organic matter had a significant impact on TCH degradation. Notably, the TCH degradation efficiency decreased inversely with increasing values of these parameters. The quenching experiments indicated that the free radicals contributing to the Vis+CoFe2O4/NaBiO3+PMS system were ·OH followed by SO4−, hole (h+), and the superoxide radical (O2−). The main mechanism of PMS was based on the cycle of Co3+ and Co2+, as well as Fe3+ and Fe2+. The cyclic tests and characterization by XRD and FT-IR revealed that CoFe2O4/NaBiO3 had good degradation stability. The experimental findings can serve as a reference for the complete removal of antibiotics from wastewater. [ABSTRACT FROM AUTHOR]

Purpose: Sheep manure-derived biochar (SMB) is applied to enhance soil productivity, but its impacts on soil phosphorus (P) species distribution have not been thoroughly investigated. This research aimed to explore the effects of SMB amended soil on phosphatase activities, nutrients, P species distribution, and the underlying mechanisms in agricultural soil. Materials and methods: The soils (collected from rice and tea cultivation) were incubated for a period of 92 days receiving different rates of biochars 0% (CK), 2% (T1) and 4% (T2) respectively. The SMB was manufactured at 500°C, and P species were tested via 31P NMR spectroscopy. Acid phosphomonoesterase (ACP) activities, CEC, NH4+–N, pH, NO3‾–N, Olsen‒ P and alkaline phosphomonoesterase (ALP) were determined. Results and discussion: The findings suggested that the SMB addition enhanced the pH, NO3‾–N, Olsen‒ P, CEC, NH4+–N contents in both paddy and tea soils. Furthermore, compared with CK (control), application of SMB at T2 reduced the ACP activities by 85.9 and 74.8%, but promoted the ALP activities by 89.1 and 70.6% for paddy and tea soils, respectively. The findings showed that major forms of P were orthophosphate and orthophosphate monoesters. Conclusions: The SMB application increased soil inorganic P, P availability and ALP activities as a result of increasing of P availability by decomposition of organic P. Our research showed that the SMB application is an alternative nutrient for plants instead of chemical fertilizers. Nevertheless, care should be taken with the long-term SMB application, consequently excessive nutrient utilization has the potential to induce eutrophication in aquatic environments. [ABSTRACT FROM AUTHOR]

Emergent plants have been remarkably effective in reducing phosphorus (P) discharge from ecological ditches; however, the treatment and recycling of these residues is a great challenge. In this study, magnetic biochars (MBs, i.e., MB-A, MB-C, and MB-T) were fabricated from three emergent plant residues (Acorus calamus L., Canna indica L., and Thalia dealbata Fraser, respectively) and modified with Fe(II)/Fe(III). Scanning electron microscopy-energy dispersive spectroscopy and X-ray diffraction spectra confirmed the successful loading of Fe3O4 and FeO(OH) onto the surfaces of the MBs. Batch adsorption experiments showed that MBs exhibited a higher P adsorption capacity than that of the raw biochars. Within the range of 0.8–43.0 mg L−1 in solution, the adsorption capacities of P by MB-A, MB-C, and MB-T were 304.6–5658.8, 314.9–6845.6, and 292.8–5590.0 mg kg−1, with adsorption efficiencies of 95.2–32.9%, 98.4–39.8%, and 91.5–32.5%, respectively. The primary mechanisms that caused P to adsorb onto the MBs were inner-sphere complexation and electrostatic attraction. Low pH conditions were more beneficial for the P adsorption of the MBs, while co-existing anions had a negative impact with the following order: HCO3− > SO42− > Cl−≈NO3−. The P-31 nuclear magnetic resonance results further demonstrated that the main adsorbed P species on the MBs was orthophosphate, followed by orthophosphate monoesters and DNA. Overall, MBs offer a resource utilization strategy for emergent plant residues and P-laden MBs are promising alternative P fertilizers. Highlights: Emergent plant biochar modified with Fe(II)/Fe(III) enhanced P adsorption capacity. Canna indica residue-derived MB exhibited the best P adsorption efficiency. MBs promoted P adsorption mainly via inner-sphere complexation and electrostatic attraction. P species adsorbed by MBs were mainly orthophosphate followed by orthophosphate monoesters and DNA. [ABSTRACT FROM AUTHOR]

Traditional treatment methods for tumors are inefficient and have severe side effects. At present, new therapeutic methods such as phototherapy, chemodynamic therapy, and gasodynamic therapy have been innovatively developed. High concentrations of hydrogen sulfide (H2S) gas exhibit cancer-suppressive effects. Herein, a Prussian blue-loaded tetra-sulfide modified dendritic mesoporous organosilica (PB@DMOS) was rationally constructed with glutathione (GSH)-triggered/photothermal-enhanced H2S signaling molecule release properties for gas therapy. The as-synthesized nanoplatform confined PB nanoparticles in the mesoporous structure of organosilica silica due to electrostatic adsorption. In the case of a GSH overexpressed tumor microenvironment, H2S gas was controllably released. And the temperature increases due to the photothermal effects of PB nanoparticles, further enhancing H2S release. At the same time, PB nanoparticles with excellent hydrogen peroxide catalytic performance also amplified the efficiency of tumor therapy. Thus, a collective nanoplatform with gas therapy/photothermal therapy/catalytic therapy functionalities shows potential promise in terms of efficient tumor therapy. [ABSTRACT FROM AUTHOR]

Drying and rewetting (DRW) events cause the release of colloidal phosphorus (Pcoll, 1–1000 nm) in leachate, and biochar is considered an effective inhibitor; however, the microbial mechanism remains elusive. In this study, three successive DRW cycles were performed on the soil columns to assess the effect of biochar addition on Pcoll content and its possible associates, including phosphatase-producing microbial populations (phoD- and phoC-harboring microbial communities) and alkaline/acid phosphatase (ALP/ACP) activities. Results showed that the biochar addition significantly decreased the Pcoll by 15.5–32.1% during three DRW cycles. The structural equation model (SEM) confirmed that biochar addition increased phoD- and phoC-harboring microbial communities and ALP/ACP activities, which reduces the release of Pcoll into leachate. In addition, the manure biochar was more effective than the straw biochar in promoting competition and cooperation in the co-occurrence network (2–5% nodes increased on average), and the key taxa Proteobacteria and Cyanobacteria were identified as the dominant species of potential ALP/ACP activities and Pcoll content. Our findings provide a novel understanding of biochar reducing Pcoll loss from the phosphatase perspective by regulating the phoD- and phoC-harboring communities during DRW events. Highlights: Biochar reduced Pcoll by 15.5–32.1% in leachate during DRW cycles. Pcoll decreased with increasing phoD- and phoC-harboring microbial communities. Proteobacteria and Cyanobacteria were the key taxa driving Pcoll content. [ABSTRACT FROM AUTHOR]

Combined application of biochar and organic fertilizer improves soil structure and crop yield but may lead to increased loss of phosphorus (P). To reduce the P loss risk in this case, rice straw biochar (BC) and sheep manure (SM) were modified using polyacrylamide (PAM). The effects of using organic amendments (BC, SM, and PAM-modified organic mixtures) and no amendments (CK) on soil total and colloidal P leaching loss from paddy soils were evaluated through soil column leaching experiments. The soil leachate volume was increased by 8.91% with BC treatment and reduced by 15.3% with SM treatment. The total P leaching loss (973.9 μg kg−1) from the BC-treated soil was higher than that from other treatments (541.4–963.5 μg kg−1). However, there was much more colloidal P loss (480.0 μg kg−1) from SM treatment. The optimal conditions for the preparation of BC and SM modified using polyacrylamide (PSB) for reducing P leaching loss were SM/BC = 4:1, 1% PAM, and 100 °C. Molybdate-unreactive P accounts for 58.61–86.89% of the colloidal P in the soil leachate with organic amendments. PSB reduced colloidal P loss (particularly in 10–220 nm range) by ~ 50% compared with BC and SM treatments. The colloidal P concentration in the leaching solutions was significantly correlated with TOC and susceptible to Fe and Al concentrations. Using PAM-modified mixture instead of manure and biochar as a soil amendment can effectively control P leaching from fields. [ABSTRACT FROM AUTHOR]

Single‐atom nanozymes (SAzymes) can effectively mimic the metal active centers of natural enzymes at the atomic level owing to their atomically dispersed active sites, thereby maximizing atom utilization efficiency and density of active sites. Hence, SAzymes can be considered the most promising candidates to replace natural enzymes. Herein, a PEGylated mesoporous Mn‐based single‐atom nanozyme (PmMn/SAE) employing a coordination‐assisted polymerization pyrolysis strategy that uses polydopamine for photothermal‐augmented nanocatalytic therapy is designed. PmMn/SAE exhibits excellent multiple enzymatic performance, including catalase‐like, oxidase‐like, and peroxidase (POD)‐like performance, due to the atomically dispersed Mn active species. As a result, PmMn/SAE not only catalyzes the decomposition of endogenous H2O2 to generate O2 for relieving hypoxia inside the tumor but also transfers electrons to O2 to produce superoxide radicals to kill tumor cells. Meanwhile, PmMn/SAE is able to trigger Fenton‐like reactions to generate highly toxic hydroxyl radicals to induce cancer cell apoptosis. The POD‐like catalytic mechanism of mMn/SAE is revealed using experimental results and density functional theory. Furthermor, PmMn/SAE shows good photothermal conversion efficiency (η = 22.1%) in the second near‐infrared region (1064 nm). Both the in vitro and in vivo experimental results indicate that PmMn/SAE can effectively kill cancer cells through photothermal‐enhanced catalytic therapy. [ABSTRACT FROM AUTHOR]

Aberrant expression of genes contributes to the chemoresistance of colorectal cancer (CRC) treatment. This study aimed to identify genes associated with the chemoresistance of oxaliplatin-based chemotherapy in CRC patients and to construct a signature. Oxaliplatin resistance-related genes were screened by analyzing the gene profiles of cell lines and tissue samples that underwent oxaliplatin-based treatment. Oxaliplatin resistance-related genes were used to establish a signature. The association of the signature had clinical significance, so the prognostic value of the signature was analyzed. Independent cohorts and CRC cell lines were used to validate the value of the gene signature and the oxaliplatin-resistant genes. There were 64 oxaliplatin resistance-related genes identified after overlapping the genes from the dataset of oxaliplatin-treated CRC cells and the dataset of patients treated with oxaliplatin-based chemotherapy. A gene signature based on five oxaliplatin resistance-related genes was established. This gene signature effectively predicted the prognosis of CRC patients who underwent chemotherapy. No significant associations were found between the gene mutations and survival of the patients; however, two genes were associated with microsatellite instability status. Two external independent cohorts and CRC cell line experiments validated the prognostic values of the signature and expression of the genes after oxaliplatin treatment. In conclusion, the oxaliplatin resistance-related gene signature involving five genes was a novel biomarker for the prediction of the chemotherapy response and prognosis of CRC patients who underwent oxaliplatin-based chemotherapy. [ABSTRACT FROM AUTHOR]

Nutrient fertilization plays a major role in improving crop productivity and maintaining soil fertility. In the last few decades, the productivity of current agricultural practices highly depends on the use of chemical fertilizers. Major drawback of traditional fertilizers is their low crop nutrient use efficiency and high loss into water. Nanomaterial in agriculture is a multipurpose tool for increasing growth, development, and yield of plants. Nanotechnology facilitates the amplifying of agriculture production by reducing relevant losses and improving the input efficiency. Nanotechnology has emerged as an attractive field of research and has various agriculture applications, especially the use of nano-agrochemicals to increase nutrient use efficiency and agricultural yield. Nanofertilizers are more effective as compared to chemical fertilizers due to their cost-efficient, eco-friendly, non-toxic, and more stable in nature. Overall, this chapter focuses on synthesis of nanofertilizers through physical, chemical, and biological methods. This chapter will also explore the use of nano-enabled fertilizers to enhance the nutrient use efficiency for sustainable crop production, and global food safety. [ABSTRACT FROM AUTHOR]

Phosphorus (P) is limiting nutrient in many soils, and P availability may often depend on iron (Fe) speciation. Colloidal iron phosphate (FePO4coll) is potentially present in soils, and we tested the hypothesis that phytate exudation by Pteris vittata might dissolve FePO4coll by growing the plant in nutrient solution to which FePO4coll was added. The omission of P and Fe increased phytate exudation by P. vittata from 434 to 2136 mg kg−1 as the FePO4coll concentration increased from 0 to 300 mM. The total P in P. vittata tissue increased from 2880 to 8280 mg kg−1, and the corresponding increases in the trichloroacetic acid (TCA) extractable P fractions were inorganic P (860–5100 mg kg−1), soluble organic P (250–870 mg kg−1), and insoluble organic P (160–2030 mg kg−1). That is, FePO4-solubilizing activity was positive correlated with TP, TCA P fractions in P. vittata, TP in growth media, and root exudates. This study shows that phytate exudation dissolved FePO4coll due to the chelation effect of phytic acid on Fe; however, the wider question of whether phytic acid excretion was prompted by deprivation of P, Fe, or both remains to be answered. [ABSTRACT FROM AUTHOR]

The Yangtze River Delta region is an important commodity grain production area in China, but has been suffering from agricultural non-point source pollution issues in recent years. This study puts forward a suggestion on promoting the construction of zero-direct discharge (ZDD) engineering for agricultural wastewater from paddy fields in the region. This suggestion is based on the field investigation, policy analysis, engineering design, and economical evaluation, which clarifies the policy adaptability and the construction importance of the ZDD engineering. At the same time, this suggestion shows the basic principles, design requirements, mode selections, investment cost, and expected ecological economic benefits of the ZDD engineering. It is expected to provide decision support for China to mitigate the non-point source pollution and enhance agricultural green development. [ABSTRACT FROM AUTHOR]

Anthropogenic activities, such as mining, influence soil bacterial community composition and microbial distributions. In the current study, the patterns in microbial distribution and the environmental drivers shaping the soil bacterial community composition in the alpine mining area of the Tianshan Mountain region, China, were investigated, and the bacterial communities were analyzed using 16S rDNA pyrosequencing. The environmental factors and their relationships with the microbial community composition, structure, and diversity were also assessed. The soil organic carbon (SOC) concentration increased along the elevation gradient, with the highest concentration in the mining area, which increased microbial abundance and species richness. Some metals, like Ca, Cu, Pb, and Zn, accumulated significantly in the tailing area and were negatively correlated with the microbial community structure. Proteobacteria, Acidobacteria, Actinobacteria, and Verrucomicrobia were the dominant phyla; these dominant phyla were more abundant in the areas without mining than in the areas with mining at the same altitude. The relative abundance of Proteobacteria and Verrucomicrobia significantly increased along the elevation gradient, while that of Actinobacteria in the mining camp area was more than twice those in the other areas due to higher soil pH. Soil biomass was the highest in the valley. Collectively, these results elucidate the influence of anthropogenic mining activities on soil microbial communities in alpine mining soils and provide a basis for the future management of heavy metal-contaminated areas using the indigenous dominant bacterial phyla. [ABSTRACT FROM AUTHOR]

Purpose: The present study aimed to assess the synergistic effects of superabsorbent polyacrylamide hydrogel (SPH) and gypsum on colloidal phosphorus (CP) release from different farmlands (i.e. tea, vegetable, and paddy soils). Materials and methods: A laboratory experiment was carried out to examine the effects of SPH at different rates of 0.00, 0.01, 0.05, and 0.1% (w/w) and gypsum at the rates of 0 and 0.005% (w/w) on CP released from different farmland soils. For this purpose, CP, colloidal molybdate–reactive P (MRPc), and colloidal molybdenum–unreactive P (MUPc) were measured in soil solutions. Results and discussion: The results revealed that the release of CP, MRPc, and MUPc ranged respectively from 5.20 to 56.65, 1.62 to 39.09, and 0.33 to 37.10% of total P (TP) in soil solutions across three farmland soils. Besides, the soils treated with SPH and gypsum (0.1%) mitigated CP release respectively by 51.75%, 62.64%, 24.13%, and 62.74% for tea, vegetable, silt loam paddy, and loam paddy soils. However, the MRPc release dropped respectively by 40.22%, 41.04%, 38.55%, and 63.70% in tea, vegetable, silt loam paddy, and loam paddy soils, and similar trends were observed in MUPc, namely, 43.72%, 49.37%, 35.71%, and 56.17% respectively in tea, vegetable, silt loam paddy, and loam paddy soils. The results indicated that gypsum could make a binding in the carboxyl group of polyacrylamide (PAM)/SPH and anion CP because of decreased CP release. Conclusions: The major form of P was CP, and co-application of PAM/SPH and gypsum could be a promising management approach to moderate CP release from agricultural soils. [ABSTRACT FROM AUTHOR]

Purpose: Nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) has been widely proposed to reduce nitrogen (N) loss and improve N availability in paddy soil. However, little knowledge exists regarding the optimum dose of DMPP required for inhibiting nitrification in different soil types. Materials and methods: In undisturbed soil columns under greenhouse conditions, dynamics of ammonium (NH4+–N) and nitrate (NO3−–N) in floodwater and leachate, and ammonia (NH3) volatilization were studied in two paddy soils (hydragic and gleyed), amended with urea-N at 180 N kg/ha with DMPP applied at 0, 0.45, 0.675, and 0.90 kg/ha (0.25%, 0.375%, and 0.5% of urea-N, respectively). The source of DMPP was Entec® 46 (46% urea-N and DMPP at 0.5% of urea-N) that was mixed with pure urea (fertilizer mixture). Results and discussion: DMPP application rates and soil types significantly influenced NH4+–N and NO3−–N concentrations in floodwater and leachate; however, DMPP application rates did not significantly impact NH4+–N concentrations in floodwater. Results indicate that concentrations of both NH4+– N and NO3−–N in leachate and floodwater were peaked between 10 and 20 days after fertilizer application. Increased DMPP application rates increased floodwater and leachate NH4+–N concentrations, while significantly decreasing NO3−–N concentrations in floodwater and leachate, with largest decrease seen in the 0.90-kg/ha DMPP treatment. NH3 emissions were observed after fertilizer was applied and decreased gradually, with no significant differences in response to the DMPP amount. The total N losses via leaching and NH3 emission were significantly decreased at treatments of 0.675 kg/ha and 0.90 kg/ha DMPP, and positively correlated with sand fraction in soil. Compared with the gleyed paddy soil, higher total N loss was observed in the hydragic paddy soil, which was related to the higher sand fraction of the hydragic paddy soil and the better behavior of DMPP in this soil type. Conclusions: Considering economic factors, mineral N concentrations in floodwater and leachate, together with N losses via leaching and volatilization, application of 0.675 kg/ha DMPP could significantly inhibit nitrification in the hydragic paddy soil while application of 0.90 kg/ha DMPP was shown to be the best choice to inhibit nitrification in the gleyed paddy soil. [ABSTRACT FROM AUTHOR]

Nutrient losses from Mississippi watersheds degrade downstream water bodies. As forested floodplains intercept agricultural drainage waters, a limiting nutrient like phosphorus (P) could potentially be sequestered in forest soils, reducing P loss to the Gulf of Mexico. Thus far, the role of temperate deciduous floodplain soils for P has not been extensively investigated in the Midwestern United States. The objective of this study was to investigate the buffering capacity of P in floodplain soils using soil biochemical chemical assays, 31P nuclear magnetic resonance spectroscopy (NMR) and P K-edge X-ray absorption near edge structure spectroscopy (XANES). Phosphorus reaction dynamics were compared between floodplains and surrounding upland soils in east-central Illinois, USA. Total organic P was significantly greater in the floodplain (277.27 ± 159.51 mg kg−1) than that in the upland (113.04 ± 74.88 mg kg−1), illustrating its buffering capacity. Notably, microbial biomass P (averaged 13.08 mg kg−1) was greater in the floodplain than that in the upland. The results of 31P NMR analysis showed the presence of organic P (e.g., orthophosphate monoesters) and orthophosphate. The P K-edge XANES analysis shows that these inorganic and organic P species are predominantly adsorbed in calcite and precipitated as calcium phosphate in floodplain soils. These findings suggest that temperate deciduous floodplain soils have a great potential to immobilize agricultural P in the Upper Mississippi watershed. [ABSTRACT FROM AUTHOR]

Background: Nutrient balance in rice paddy fields can change under different tillage management practices; however, the extent of the change may differ for various rice varieties. A field experiment was conducted over 2 successive years to clarify the effects of no-till and rice varieties on the apparent balance of nitrogen (N) and phosphorus (P). Four treatments: no-till/japonica rice (NTJ), no-till/glutinous rice (NTG), conventional tillage/japonica rice (CTJ), and conventional tillage/glutinous rice (CTG) with three replicates of each were established to test the hypothesis that no-till and japonica rice can improve the apparent balance of nutrients. Results: The tillage method and rice variety had interactive effects on the apparent balance of N and P. After the 2-year experiment, total N and P pools in the 20 cm surface soil layer were highest under the NTJ treatment (4757.0 kg N ha−1, 2428.5 kg P ha−1) and lowest under the CTG treatments (4726.3 kg N ha−1, 2412.0 kg P ha−1). Under no-till conditions, japonica rice had higher grain yield but lower straw biomass than that of glutinous rice. NTG treatment significantly increased the N and P content in rice grains and straw. The environmental losses of N and P in the rice fields mainly occurred during the rice season. Based on nutrient balance estimation, N losses in the NTJ, NTG, and CTJ treatments were reduced by 15.03 kg N ha−1, 11.55 kg N ha−1, 6.72 kg N ha−1, respectively, as compared with that of the CTG treatment. The corresponding P losses were reduced by 8.02 kg P ha−1, 7.84 kg P ha−1, and 3.96 kg P ha−1. In terms of economic benefits, NTJ also resulted in the highest actual income (2724.25 US dollars) and the highest ratio of production investment (6.40). Conclusion: No-till was more likely to maintain soil N and P nutrients than conventional tillage, and this advantage was most significant when planting japonica rice. In addition, no-till was conducive to N and P uptake by rice, but only japonica rice exhibited increased grain yield. Consequently, the NTJ treatment was recommended to improve the N and P balance. [ABSTRACT FROM AUTHOR]

Background: Colloid-facilitated phosphorus (P) transport is recognized as an important pathway for the loss of soil P in agricultural systems; however, information regarding soil aggregate-associated colloidal P (Pcoll) is lacking. To elucidate the effects of aggregate size on the potential loss of Pcoll in agricultural systems, soils (0–20 cm depth) from six land-use types were sampled in the Zhejiang Province in the Yangtze River Delta region, China. The aggregate size fractions (2–8 mm, 0.26–2 mm, 0.053–0.26 mm and < 0.053 mm) were separated using the wet sieving method. Colloidal P and other soil parameters in aggregates were analyzed. Results: Our study demonstrated that 0.26–2 mm small macroaggregates had the highest total P (TP) content. In acidic soils, the highest Pcoll content was observed in the 0.26- to 2-mm-sized aggregates, while the lowest was reported in the < 0.053 mm (silt + clay)-sized particles, the opposite of that revealed in alkaline and neutral soils. Paddy soils contained less Pcoll than other land-use types. The proportion of Pcoll in total dissolved P (TDP) was dominated by < 0.053 mm (silt + clay)-sized particles. Aggregate size strongly influenced the loss potential of Pcoll in paddy soils, where Pcoll contributed up to 83% TDP in the silt + clay-sized particles. The Pcoll content was positively correlated with TP, Al, Fe, and the mean weight diameter. Aggregate-associated total carbon (TC), total nitrogen (TN), C/P, and C/N had significant negative effects on the contribution of Pcoll to potential soil P loss. The Pcoll content of the aggregates was controlled by the aggregate-associated TP and Al content, as well as the soil pH value. The potential loss of Pcoll from aggregates was controlled by its organic matter content. Conclusion: We concluded that management practices that increase soil aggregate stability or its organic carbon content will limit Pcoll loss in agricultural systems. [ABSTRACT FROM AUTHOR]

Background: Rice paddy wetlands may serve as a nutrient source or sink in agricultural ecosystems. However, the pattern of nutrient loss on a watershed scale is not clear. A year-round on-site observation study based on 6-h intervals was conducted. Rainfall, temperature, runoff nutrient concentrations, and adjacent stream water samples were automatically monitored to uncover the temporal changes in the runoff losses of the predominant nutrient proxies (total N and total P) from a typical rice-planting area (120 ha) in the Yangtze river delta region of China. Results: A high total N concentration in the rice-planting area was observed during the rice-planting season; however, significant fluctuation in the total P was evident throughout the year. The Δtotal N (drainage minus stream) parameter showed negative values with a mean of −0.25 mg L−1, while Δtotal P showed positive values with a mean of 0.06 mg L−1. The annual average N and P runoff from paddy field were 11.6 kg ha−1 and 1.5 kg ha−1, respectively. The window phases for the total N loss were mainly concentrated in the rice-growing season. However, the window phase for the total P loss was more dispersive throughout the year. No apparent relationships were found between rainfall and N and P concentrations by self-organizing map analysis. Conclusions: The high-resolution monitoring, in this study, suggested that nutrient loss loading rather than nutrient concentration was strongly related to surface runoff Therefore, fertilization before high-intensity rainfall should be avoided to mitigate the nutrient runoff losses and maintain the rice wetland eco-function. [ABSTRACT FROM AUTHOR]

Purpose: Laboratory incubation experiments using 15N stable isotope labeling and acetylene suppression techniques were conducted to compare the autotrophic nitrification and heterotrophic nitrification rates with the addition of swine manure (SW) and swine-manure-derived biochar (SWB) in two paddy soils. Materials and methods: SW and SWB were applied at four N-based amendment levels, namely control (0 mg N kg−1), low (1.1 mg N kg−1), medium (2.2 mg N kg−1), and high (4.4 mg N kg−1). Twenty-five milliliters of C2H2 gas were injected into each storage bottle to inhibit autotrophic nitrification in soil. At the end of the preincubation period, 160 mg kg−1 15N-glycine were added to each storage bottle to stimulate heterotrophic nitrification in soil. Results and discussion: Results showed that SW increased the NH4+-N content by 3.5 to 17.5 mg kg−1 in both soils, while SWB decreased it by 0.1 to 4.7 mg kg−1 compared to control group, regardless of whether autotrophic nitrification was inhibited. Both SW and SWB enhanced NO3−-N accumulation in the two soils compared to control group when autotrophic nitrification was not inhibited; however, NO3−-N concentration in the soil with SWB was up to 24% lower than that with the same level of SW addition. NH3 volatilization rates were elevated at all the SW and SWB amendment levels, although only SW led to higher N2O emission rates. Compared with SW, high level of SWB significantly decreased N2O emissions by 78 to 84% in the loam and clay loam soils. The increase in NH3 volatilization, soil NO3−-N accumulation, and autotrophic nitrification rate were greater with SW than with SWB. Higher rates of soil heterotrophic nitrification were observed in SWB-amended soils than in SW-amended soils with a high (4.4 mg N kg−1) amendment level. Conclusions: Our results suggest that SWB is less likely to increase NO3−-N accumulation in soil and contributes more to the lower soil autotrophic nitrification rate compared with SW. Although SWB can promote heterotrophic nitrification, it generally inhibits the autotrophic nitrification process and slows the increment pace of the gross nitrification in paddy soils. [ABSTRACT FROM AUTHOR]

Purpose: Biogas slurry (BS) is used for soil productivity amendment, but its effect on soil phosphorus (P) form distribution has not been thoroughly examined. The objective of this study was to determine the effect of BS on soil nutrients, phosphomonoesterase activities, and P species distribution. Materials and methods: A 91-day incubation study was carried out for a silt soil which was amended with BS at a rate equivalent to 120 kg N ha−1 and 38 kg P ha−1 and 240 kg N ha−1 and 76 kg P ha−1. The soil with no BS addition was used as control. Solution P-31 nuclear magnetic resonance (31P-NMR) spectroscopy was used to characterize soil P species. Acid phosphomonoesterase (ACP) and alkaline phosphomonoesterase (ALP) activities, pH, cation exchange capacity (CEC), NH4+–N, NO3−–N, and Olsen P were also evaluated. Results and discussion: The results indicated that the application of BS increased pH, CEC, NH4+–N, NO3−–N, and Olsen P contents. Moreover, the addition of BS inhibited ACP activity, but it increased ALP activity. A significant positive correlation was found between ALP and orthophosphates, suggesting ALP activity may play important roles in the release of orthophosphates. The P composition was dominated by inorganic orthophosphate (59.9–76.2% extracted P) and orthophosphate monoesters (23.8–38% extracted P), with smaller concentration of pyrophosphates (1.2–3.6% extracted P), and orthophosphate diesters (less than 1.5% of the extracted P). Conclusions: The P was mainly in the form of inorganic orthophosphates and organic monoesters. The present study shows that BS can be a substitute solution for the supply of essentials nutrients for plants. However, care would be entirely taken with long-term application of BS, since extreme nutrients addition may cause eutrophication of water bodies. [ABSTRACT FROM AUTHOR]

Irrigation and fertilization management are important for controlling agricultural soil salinity and increasing productivity in extremely arid regions. The objective of this research was to evaluate the effects of long‐term drip irrigation and organic fertilizer application on soil salinity, fruit quality and yield of jujube [Ziziphus ziziphus (L.) Karst]. We established a 7‐yr field experiment in a desert‐oasis area in Northwest China. Six treatments were performed: CK (conventional irrigation, no fertilizer), CIMF (conventional irrigation, mineral fertilizer), CIOF (conventional irrigation, organic fertilizer), DI (drip irrigation, no fertilizer), DIMF (drip irrigation, mineral fertilizer), and DIOF (drip irrigation, organic fertilizer). The results showed that soil organic carbon (SOC) concentration in soil treated with organic fertilizer increased gradually over years. Treatment DIOF favored the accumulation of SOC with the highest content and stock after 7 yr. Lower salt content in root zone was found in DIOF after 7 yr. The yield of DIOF increased annually and reached an equilibrium level after the fourth year (14.88 to 16.69 Mg ha−1). Total carbohydrate and vitamin C (Vc) of DIOF of fruit were all significantly higher than CIOF and DIMF. The boosted regression tree showed that SOC content had the highest relative contribution rate to jujube yield. Path analysis identified the most important factor affecting SOC in the drip‐fertigation system was the input of organic fertilizer, with path coefficient 0.65. Long‐term combination of drip irrigation and organic fertilizer application would be an effective strategy maintaining productivity and improve fruit quality in extremely arid areas. [ABSTRACT FROM AUTHOR]

Colloidal phosphorus (CP) as an additional route of P mobilization in soil solution has gained much attention. A batch experiment was conducted to investigate the effect of sheep manure-derived biochar (SMB) on CP release from various land uses (paddy, vegetable, tea, and citrus) at a rate of 0% as a control treatment (CK), 1% as a low (L) level, 2% as a middle (M) level, and 4% as a high (H) level of SMB application. The CP and MRPcoll in the solution increased from 30.58 to 88.97% and from 2.45 to 55.54% of total P (TP), respectively. The SMB enhanced CP release in all the soils and all the treatments (except CK and L levels in tea soil; CK, L, and M levels in vegetable soil; and L and M levels in citrus soil). Multiple linear regression revealed a significant correlation between CP and MRPcoll and between colloidal iron, aluminum, calcium, and total organic carbon (Fecoll, Alcoll, Cacoll, and TOCcoll) and pH, which may play an important role as CP carriers that could depend on the pH. This study suggests that the application of SMB in the soil at an appropriate rate of 1 and 2% for tea and vegetable soils, respectively, could be beneficial to avoid the risk of CP release in water bodies. [ABSTRACT FROM AUTHOR]

Converting swine manure to biochar is an effective way to recycle valuable nutrients, but there are few reports on its feasibility as a phosphorus (P) source. The objective of this study was to clarify the unique nature, including P speciation, of manure biochar products under various pyrolysis temperatures. We used solution 31P nuclear magnetic resonance and P K-edge X-ray adsorption near-edge spectroscopy (P XANES) to characterize P species in swine manure biochar. For every 100 °C increment starting from 300 °C, the P content in manure biochar increased by 2.16 to 3.37 g kg−1. However, above 400 °C, organic P species did not appear anymore, and only inorganic P, including orthophosphate and pyrophosphate, existed. P K-edge XANES spectra further showed all biochar samples had higher percentages of Ca3 (PO4)2 and NaP2O7, and lower percentages of FePO4, AlPO4, and inositol hexaphosphate compared to manure. Interestingly, percentages of Ca3(PO4)2, FePO4, and AlPO4 in MB400 (indicating manure pyrolysed at 400 °C) were comparable with those in MB700 while the percentage of NaP2O7 was higher in MB400. Phosphorus release from MB400 maintained a relatively high level at 0.33 g kg−1 during the whole 300-h observation period. These results suggest that with a suitable pyrolysis temperature, it was feasible for manure biochar to be a P source alternative.ᅟ [ABSTRACT FROM AUTHOR]

Arsenic (As) and lead (Pb) commonly co-exist with high concentrations in paddy soil mainly due to human activities in south of China. This study investigates the effect of ferrous sulfate (FeSO4) amendment and water management on rice growth and arsenic (As) and lead (Pb) accumulation in rice plants. A paddy soil co-contaminated with As and Pb was chosen for the pot experiment with three FeSO4 levels (0, 0.25, and 1%, on a dry weight basis) and two water managements (flooded, non-flooded). The concentrations of As and Pb in iron plaques and rice plants were determined. Application of FeSO4 and non-flooded conditions significantly accelerated the growth of rice plants. With the addition of FeSO4, iron plaques were significantly promoted and most of the As and Pb were sequestered in the iron plaques. The addition of 0.25% FeSO4 and non-flooded conditions did not significantly change the accumulation of As and Pb in rice grains. The practice also significantly decreased the translocation factor (TF) of As and Pb from roots to above-ground parts which might have been aided by the reduction of As and Pb availability in soil, the preventing effect of rice roots, and the formation of more reduced glutathione (GSH). Flooded conditions decreased the Pb concentration in rice plants, but increased As accumulation. Moreover, rice grew thin and weak and even died under flooded conditions. Overall, an appropriate FeSO4 dose and non-flooded conditions might be feasible for rice cultivation, especially addressing the As issue in the co-contaminated soil. However, further detailed studies to decrease the accumulation of Pb in edible parts and the field application in As and Pb co-contaminated soil are recommended. [ABSTRACT FROM AUTHOR]

The effect of no-tillage (NT) on rice yield and nitrogen (N) behavior often varies considerably from individual studies. A meta-analysis was performed to assess quantitatively the effect of NT on rice yield and N uptake by rice, N use efficiency (NUE, i.e., fertilizer N recovery efficiency), and nutrient runoff losses. We obtained data from 74 rice-field experiments reported during the last three decades (1983-2013). Results showed the NT system brought a reduction of 3.8 % in the rice yield compared with conventional tillage (CT). Soil pH of 6.5-7.5 was favorable for the improvement of rice yield with the NT system, while a significant negative NT effect on rice yield was observed in sandy soils ( p < 0.05). N rate, ranging from 120 to 180 kg N ha, for at least 3 years was necessary for NT to enable rice yield comparable with that of CT. Furthermore, the observations indicated NT reduced N uptake and NUE of the rice by 5.4 and 16.9 %, while increased the N and P exports via runoff by 15.4 and 40.1 % compared with CT, respectively. Seedling cast transplantation, N rate within the range 120-180 kg N ha, and employing NT for longer than 3 years should be encouraged to compromise between productivity and environmental effects of NT implementation in rice fields. [ABSTRACT FROM AUTHOR]

No tillage (NT) can be used as a management tool to alleviate the negative effects of agricultural practices on the environment by reducing the runoff volume and nutrient exports. The main objective of this research was to quantify the effect of NT on nitrogen (N) and phosphorus (P) exports across a rice-planted watershed using the soil and water assessment tool (SWAT) model. Results show that total N and P runoff exports from rice fields across the watershed ranged from 7.2 to 22.8 kg N/ha and 0.56 to 6.80 kg P/ha, respectively, over five rice-growing seasons under conventional tillage (CT) practice. The adoption of NT reduced the runoff volume, and the total N and total P exports by 25.9, 8.5, and 7.8 %, respectively, compared with the total exports under CT practice in the same study area. Rice yields were reduced by 0.7-1.9 % within the first 4 years after the adoption of NT, but began to rise in the fifth year. These results suggest that a long-term period of NT practice is necessary to reduce N and P exports without comprising the rice yield on rice-planted watersheds. In addition, the benefits of implementing NT practice alone were limited, and other practices, such as water and nutrient management, should be combined with NT practice. [ABSTRACT FROM AUTHOR]

Profound understanding of behaviors of organic matter from sources to multistage rivers assists watershed management for improving water quality of river networks in rural areas. Ninety-one water samples were collected from the three orders of receiving rivers in a typical combined polluted subcatchment (diffuse agricultural pollutants and domestic sewage) located in China. Then, the fluorescent dissolved organic matter (FDOM) information for these samples was determined by the excitation-emission matrix coupled with parallel factor analysis (EEM-PARAFAC). Consequently, two typical humic-like (C1 and C2) and other two protein-like (C3 and C4) components were separated. Their fluorescence peaks were located at λ = 255(360)/455, <250(320)/395, 275/335, and <250/305 nm, which resembled the traditional peaks of A + C, A + M, T, and B, respectively. In addition, C1 and C2 accounted for the dominant contributions to FDOM (>60 %). Principal component analysis (PCA) further demonstrated that, except for the autochthonous produced C4, the allochthonous components (C1 and C2) had the same terrestrial origins, but C3 might possess the separate anthropogenic and biological sources. Moreover, the spatial heterogeneity of contamination levels was noticeable in multistage rivers, and the allochthonous FDOM was gradually homogenized along the migration directions. Interestingly, the average content of the first three PARAFAC components in secondary tributaries and source pollutants had significantly higher levels than that in subsequent receiving rivers, thus suggesting that the supervision and remediation for secondary tributaries would play a prominent role in watershed management works. [ABSTRACT FROM AUTHOR]

Purpose: Colloid-facilitated migration of phosphorus (P) is a widely accepted phenomenon in surface and subsurface environment. Release and migration of colloidal P (P) in agricultural fields are closely related to P fertilization regimes. In this study, a site-specific experiment with rice/oilseed rape rotation was conducted to determine the export potential of P from the field and literatures reporting the impact of P fertilization regimes on release and migration of P in other agricultural fields were compared. Materials and methods: In this 2-year field experiment, four P fertilization regimes (no fertilizer control, inorganic P fertilizer of low and high rates, and swine manure treatment) with three replicates were conducted. Floodwater and runoff samples were collected in flooding season and the 100-cm-depth soil samples were collected after both crops' harvest seasons. Colloidal particles were separated by microfiltration and ultracentrifugation processes and determined gravimetrically. The P value was calculated as the difference between the concentration of total P in non-ultracentrifuged and ultracentrifuged samples. The same method was applied for the colloidal mineral elements (Fe and Al) and organic carbon. Results and discussion: Total P concentration in paddy floodwater significantly increased after fertilization but decreased quickly in the following days, maintaining at 6.0 mg m. In soil extracts, concentration of P was low but stable, which ranged from 6 to 22 % of total P after oilseed rape season and from 7 to 18 % after rice season. In runoff samples, there were positive correlations between P, colloidal Fe (Fe), colloidal Al (Al), and colloidal TOC (TOC); the majority of P forms was molybdate reactive P. In both crops' seasons, the amount of colloids increased with soil depth. Content of soil P was low and occupied 0.1-2 % of total P. The literature review showed that P in soil solution, runoff, and leachate ranged from 1.4 to 94 % of total P. Conclusions: These results suggested that although the concentrations of P were not high, they widely distributed in paddy floodwater, runoff, and soil profile. Fertilization regimes and planting systems had a significant influence on the contents of P. Moreover, the P binding with Fe/Al minerals and organic carbon might be an alternative route of P loss in paddy field. [ABSTRACT FROM AUTHOR]

Swine manure application could affect soil legacy P and related transformation. Soil samples were taken for two rice seasons to uncover the responses of soil P fractions and phosphomonoesterase activities in a middle-term swine manure-applied rice field. The field experiment treatments included three swine manure organic amendment rates (26 [low], 39 [middle], and 52 kg P ha [high]) and two controls (no fertilizer and 26 kg P ha superphosphate). On seasonal average, the relative sizes of labile (HO-P, NaHCO-P, and NaHCO-P), moderately labile (NaOH-P and NaOH-P), and stable (HCl-P and residual-P) P pools were in 1: 3.1: 3.6 and 1: 2.3: 3.7 ratios in 2011 and 2012, respectively. According to P fractions (except for residual-P) and phosphomonoesterase activities, treatments could be ranked as M > M > M > P > CK over the whole rice growth stages, but the difference between the 39 and 52 kg P ha manure rates was not significant. Most of P fractions showed the highest content at rice seedling stage for all treatments while phosphomonoesterase activities reached their maximums at rice tillering stage for all treatments. Moreover, repeated swine manure did not affect most of P fractions (except for NaOH-P) and phosphomonoesterase activities under the plow layer due to the mature plow pans. Our results suggest that the swine manure application should be kept at about 39 kg P ha to decrease potential environmental risks and to maintain soil legacy P in the paddy soil. [ABSTRACT FROM AUTHOR]

One of the primary challenges of our time is to feed a growing and more demanding world population with reduced external inputs and minimal environmental impacts, all under more variable and extreme climate conditions in the future. Conservation agriculture represents a set of three crop management principles that has received strong international support to help address this challenge, with recent conservation agriculture efforts focusing on smallholder farming systems in sub-Saharan Africa and South Asia. However, conservation agriculture is highly debated, with respect to both its effects on crop yields and its applicability in different farming contexts. Here we conduct a global meta-analysis using 5,463 paired yield observations from 610 studies to compare no-till, the original and central concept of conservation agriculture, with conventional tillage practices across 48 crops and 63 countries. Overall, our results show that no-till reduces yields, yet this response is variable and under certain conditions no-till can produce equivalent or greater yields than conventional tillage. Importantly, when no-till is combined with the other two conservation agriculture principles of residue retention and crop rotation, its negative impacts are minimized. Moreover, no-till in combination with the other two principles significantly increases rainfed crop productivity in dry climates, suggesting that it may become an important climate-change adaptation strategy for ever-drier regions of the world. However, any expansion of conservation agriculture should be done with caution in these areas, as implementation of the other two principles is often challenging in resource-poor and vulnerable smallholder farming systems, thereby increasing the likelihood of yield losses rather than gains. Although farming systems are multifunctional, and environmental and socio-economic factors need to be considered, our analysis indicates that the potential contribution of no-till to the sustainable intensification of agriculture is more limited than often assumed. [ABSTRACT FROM AUTHOR]

Phosphorus (P) in wetlands is mainly bound to sediment in various species, which is essential to predict water column P levels. The purpose of this work is to understand the influences of sediment properties and vegetation types on P speciation. Sediments under four vegetation types in the tidal flat and offshore sandbar in Hangzhou Bay of China were collected seasonally. The rank order of P species in sediment based on concentration was exchangeable P (Exch-P) < iron/aluminum-bound P (Fe/Al-P) < organic P (Org-P) < calcium-bound P (Ca-P). Sediment total phosphorus (TP) and Fe/Al-P concentrations were lower in offshore sandbar than those of tidal flat, reflecting effects of anthropogenic contamination in the latter. Sediment particle size distribution strongly affected P speciation, as indicated by a significant correlation between them. Total phosphorus and Org-P concentrations in vegetated sediments were higher than those of bare mudflat. Additionally, there was a significant negative correlation between Ca-P and Org-P, and Fe/Al-P, indicating the presence of vegetation which may result in P speciation by converting Ca-P to soluble and active P and higher Org-P. Overall, sediment particle size distribution is the most fundamental physical property that affects P speciation, and vegetation types are important factors that influence Org-P concentration. [ABSTRACT FROM AUTHOR]

Water and nitrogen availability plays an important role in the biogeochemical cycles of essential elements, such as carbon (C), nitrogen (N) and phosphorus (P), in agricultural ecosystems. In this study, we investigated the seasonal changes of C, N and P concentrations, accumulation, partitioning, and C:N:P stoichiometric ratios in different plant tissues (root, stem-leaf, and panicle) of late-season rice under two irrigation regimes (continuous flooding, CF; alternate wetting and drying, AWD) and four N managements (control, N0; conventional urea at 240 kg N ha−1, UREA; controlled-release bulk blending fertilizer at 240 kg N ha−1, BBF; polymer-coated urea at 240 kg N ha−1, PCU). We found that water and N treatments had remarkable effects on the measured parameters in different plant tissues after transplanting, but the water and N interactions had insignificant effects. Tissue C:N, N:P and C:P ratios ranged from 14.6 to 52.1, 3.1 to 7.8, and 76.9 to 254.3 over the rice growing seasons, respectively. The root and stem-leaf C:N:P and panicle C:N ratios showed overall uptrends with a peak at harvest whereas the panicle N:P and C:P ratios decreased from filling to harvest. The AWD treatment did not affect the concentrations and accumulation of tissue C and N, but greatly decreased those of P, resulting in enhanced N:P and C:P ratios. N fertilization significantly increased tissue N concentration, slightly enhanced tissue P concentration, but did not affect tissue C concentration, leading to a significant increase in tissue N:P ratio but a decrease in C:N and C:P ratios. Our results suggested that the growth of rice in the Taihu Lake region was co-limited by N and P. These findings broadened our understanding of the responses of plant C:N:P stoichiometry to simultaneous water and N managements in subtropical high-yielding rice systems. [ABSTRACT FROM AUTHOR]

Nutrient load into the ocean can be retained during the process of plant uptake and sedimentation in marshes along the bay zone. Seasonal variations of biomass and nutrient concentration in three dominated plant assemblages and associated sediments were monitored in this study area to determine effects of salt marsh on nutrient retention. Results showed that plant aboveground biomass displayed a unimodal curve with nutrient concentration generally decreased from spring to winter. Belowground biomass was relatively low during the rapid growth period with nutrient concentration tending to decrease and then increase during this period. Plant total nitrogen (TN) pools are higher than total phosphorus (TP) pools, and both pools showed significant seasonal variations. Water purification coefficients (WPC) of nutrients by plant assimilation were 34.4/17.3, 19.3/24.0, and 5.14/6.04 t/(m year) (TN/TP) for Phragmites australis, Spartina alterniflora, and Scirpus mariqueter, respectively. Overall, these results suggest that higher annual plant biomass and nutrient assimilation contribute to greater nutrient retention capacity and accumulation in sediments, thereby enabling reduced eutrophication in transitional waters. [ABSTRACT FROM AUTHOR]

The environmental risk of aquatic phosphorus (P) critically depends on its mobility and bioavailability, both of which are greatly affected by the size distribution and composition of P. The size distribution (particulate, colloidal and truly dissolved phase) of P, composed of molybdate reactive P (MRP) and molybdate unreactive P (MUP), was determined at twenty-three typical sections of the East Tiao River, China in the plum rain season. Results indicated particulate P was dominant followed by the truly dissolved P, while colloidal P was quantitatively the lowest in the whole river. From upstream to downstream, particulate P sharply increased, along with a slight decrease of truly dissolved P. However, colloidal P remained at a relatively stable level in the whole river, ranging from below detection limit to 0.025 mg L−1, 0 to 13.4% of total P (TP). Furthermore, colloidal MRP exhibited a rising trend downriver as compared to upriver, with the notable transfer of MRP from the truly dissolved phase to particulate and colloidal phases. Particle concentration effect for colloids, observed in the study of MRP distribution, further corroborated the role of colloids in MRP solid/liquid partitioning. These observations, in this large-scale field investigation, fitted the “colloidal pumping” hypothesis. It may be concluded that colloids act as the intermediate and buffer in the dynamically balanced transfer of P from truly dissolved phase to large particulate phase, having a significant role in size distribution of P. [ABSTRACT FROM AUTHOR]

Glyphosate, which has been widely reported to be a toxic pollutant, is often present at trace amounts in the environment. In this study, a novel copper-aluminum metal hydroxide doped graphene nanoprobe (labeled as CuAl–LDH/Gr NC) was first developed to construct a non-enzymatic electrochemical sensor for detection trace glyphosate. The characterization results showed that the synthesized CuAl–LDH had a high-crystallinity flowered structure, abundant metallic bands and an intercalated functional group. After mixed with Gr, the nanocomposites provided a larger surface area and better conductivity. The as-prepared CuAl–LDH/Gr NC dramatically improved the enrichment capability for glyphosate to realize the stripping voltammetry detection. The logarithmic linear detection range of the sensor was found to be 2.96 × 10−9–1.18 × 10−6 mol L−1 with the detection limit of 1 × 10−9 mol L−1 with excellent repeatability, good stability and anti-interference ability. Further, the sensor achieved satisfactory recovery rates in spiked surface water, ranging from 97.64% to 108.08%, demonstrating great accuracy and practicality. [ABSTRACT FROM AUTHOR]

High content of organic matter in the downstream of watersheds underscored the severity of non-point source (NPS) pollution. The major objectives of this study were to characterize and quantify dissolved organic matter (DOM) in watersheds affected by NPS pollution, and to apply self-organizing map (SOM) and parallel factor analysis (PARAFAC) to assess fluorescence properties as proxy indicators for NPS pollution and labor-intensive routine water quality indicators. Water from upstreams and downstreams was sampled to measure dissolved organic carbon (DOC) concentrations and excitation-emission matrix (EEM). Five fluorescence components were modeled with PARAFAC. The regression analysis between PARAFAC intensities (Fmax) and raw EEM measurements indicated that several raw fluorescence measurements at target excitation-emission wavelength region could provide similar DOM information to massive EEM measurements combined with PARAFAC. Regression analysis between DOC concentration and raw EEM measurements suggested that some regions in raw EEM could be used as surrogates for labor-intensive routine indicators. SOM can be used to visualize the occurrence of pollution. Relationship between DOC concentration and PARAFAC components analyzed with SOM suggested that PARAFAC component 2 might be the major part of bulk DOC and could be recognized as a proxy indicator to predict the DOC concentration. [ABSTRACT FROM AUTHOR]