通过野外试验采集稻田田面水和稻田排水径流的水样,研究了胶体磷流失贡献和流失规律。根据实际天气情况,选择1次典型暴雨事件（48 mm/h）和8次不同强度（8,9,19,23,23,32,36,49 mm/h）的降雨事件采集样品。结果表明:（1）田面水和稻田排水中磷素流失形式以颗粒磷为主。在过1μm滤膜的总磷中,胶体磷的流失贡献为21%～73%,超过真溶解磷的流失贡献。（2）降雨后田面水中胶体磷的贡献范围为9%～44%,稻田排水中胶体磷流失贡献范围为10%～16%,金属氧化物胶体、有机质胶体以及金属氧化物—有机质胶体浓度与胶体磷流失贡献呈正向相关性,田面水中皮尔森相关系数分别为0.544,0.635,0.781（p＜0.05）,稻田排水中分别为0.734,0.350,0.747（p＜0.05）,三者结合磷为径流中胶体磷的重要赋存形态。（3）施肥通过影响电导率和离子强度来削减胶体磷的流失贡献,而降雨强度则通过影响pH来增加胶体磷的流失贡献,降雨强度与稻田排水胶体磷流失浓度的线性回归系数R~2=0.75,但两者对田面水和稻田排水中胶体磷流失贡献的影响程度不同。

The reuse of water in agriculture has become more common in water management worldwide. However, there is very limited information about nutrient retention in water reclamation management. In this study, an improved low impact development (LID) practice was constructed to investigate the synergistic effects of three substrates amendment on nitrogen (N) and phosphorus (P) retention under two irrigation modules: spray and drip irrigation. The orthogonal combination of the three substrates was controlled during four leaching events, with polyacrylamide (PAM), peat soil, and straw biochar application rates of 1, 2, and 4 g kg(-1); 5, 10, and 20 g kg(-1); and 10, 20, and 40 g kg(-1), respectively. Results showed that the optimum treatments for N and P were 2 g kg(-1) of PAM; 2 g kg(-1 )of PAM, 10 g kg(-1) of peat soil, and 40 g kg(-1) of straw biochar, respectively. The highest amounts of N and P retention under spray and drip irrigation were 83.12 mg N kg(-1) and 50.09 mg N.kg(-1), and 11.88 mg P.kg(-1) and 7.47 mg P.kg(-1), respectively. The analysis of variance indicated that PAM, biochar, and peat soil affected the retention of leachate, N, and P differently. PAM application could not only improve the water, N, P retention capacity of soil, but also significantly increase the content of > 2 mm water-stable soil aggregate (WSA) (p < 0.05), and there is an advisable linear relation between N, P retention and the content of > 2 mm WSA (R-2 = 0.79, 0.67, respectively). Overall, this study concludes that a combined application of PAM and biochar could reduce P loss and increase the > 2 mm WSA under leaching condition.

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. 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. 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). 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.

Currently, environmental pollution by heavy metals is a global problem. Therefore, it is crucial to develop effective detection techniques to determine the levels of heavy metal contamination in various mediums. Voltammetry is a highly sensitive electrochemical method used for the in situ detection of heavy metal ions. This study investigates the current trends related to electrode modification, developments in materials, and optimization of the experimental parameters. We discuss the sensing performance of four kinds of nanomaterials capable of inorganic modification (metal nanoparticles, metal oxides, carbonaceous nanomaterials, and their nanocomposites). The impact of several important factors, such as the deposition potential and time, buffer solution types, and pH on the sensitivity, reproducibility, stability, and anti-interference ability of the detection process, especially with regard to the co-detection of several heavy metal ions, was reviewed. We noted that in addition to the application of voltammetry to water-related issues, it is suitable for rapid and simple identification and analyses of heavy metals in polluted soil and other mediums. Thus, it is important to conduct additional research on the application of voltammetry to this area.

Colloidal phosphorus (P-coll) in soil solutions and subsurface drainage has attracted increasing attention as an additional mobile form of P. A column study was conducted to investigate the effect of biogas slurry (BS) on P(coll )leaching in paddy topsoil (0-20 cm) at rate of 0; 225 m(3) ha(-1) (55 kg N ha(-1), 17 kg P ha(-1)); 673 m(3) ha(-1) (165 kg N ha(-1), 52 kg P ha(-1)); 1350 m 3 ha(-1) (330 kg N ha(-1), 104 kg P ha(-1)) of BS. The colloids particles were separated by microfiltration and ultra-centrifugation processes. Dissolved phosphorus (DP) in leachate ranged from 0.04 to 0.09 mg P L(-1 )and contributed between 56 and 76% to the total P leaching. P-coll in leachate ranged from 0.002 to 0.03 mg P L--(1) in leachate and contributed between 3 and 26% to TP leaching. Results clearly showed that BS increased P-coll leaching at medium (673 m(3) ha(-1): 165 kg N ha(-1), 52 kg P ha(-1)) and high application rate of BS (1350 m(3) ha(-1): 330 kg N ha(-1), 104 kg P ha(-1)). In contrast, the smallest tested BS application of 225 m(3) ha(-1) (55 kg N ha(-1), 17 kg P ha(-1)) did not affect P-coll concentrations in leachates. Significant positive correlations was found between P(coll )and colloidal aluminum (Al-coll), colloidal calcium (Ca-coll), total organic carbon (TOCcoll), and with pH, indicating that Al/Ca minerals - organic matter may play a major role as carriers for P-coll leaching and these processes were pH-dependent. This study confirms that high level of BS application could result in the mobilization of P-coll from paddy topsoil by leaching.