Zhao Yuanyuan, Wendling Laura A, Wang Changhui, Pei Yuansheng
The Key Laboratory of Water and Sediment Sciences, Ministry of Education, School of Environment, Beijing Normal University, Beijing 100875, China.
School of Agriculture and Food Sciences, University of Queensland, St Lucia, Queensland 4072, Australia.
J Environ Sci (China). 2015 Aug 1;34:133-42. doi: 10.1016/j.jes.2015.01.030. Epub 2015 Jun 5.
Fe/Al drinking water treatment residuals (WTRs), ubiquitous and non-hazardous by-products of drinking water purification, are cost-effective adsorbents for glyphosate. Given that repeated glyphosate applications could significantly decrease glyphosate retention by soils and that the adsorbed glyphosate is potentially mobile, high sorption capacity and stability of glyphosate in agricultural soils are needed to prevent pollution of water by glyphosate. Therefore, we investigated the feasibility of reusing Fe/Al WTR as a soil amendment to enhance the retention capacity of glyphosate in two agricultural soils. The results of batch experiments showed that the Fe/Al WTR amendment significantly enhanced the glyphosate sorption capacity of both soils (p<0.001). Up to 30% of the previously adsorbed glyphosate desorbed from the non-amended soils, and the Fe/Al WTR amendment effectively decreased the proportion of glyphosate desorbed. Fractionation analyses further demonstrated that glyphosate adsorbed to non-amended soils was primarily retained in the readily labile fraction (NaHCO3-glyphosate). The WTR amendment significantly increased the relative proportion of the moderately labile fraction (HCl-glyphosate) and concomitantly reduced that of the NaHCO3-glyphosate, hence reducing the potential for the release of soil-adsorbed glyphosate into the aqueous phase. Furthermore, Fe/Al WTR amendment minimized the inhibitory effect of increasing solution pH on glyphosate sorption by soils and mitigated the effects of increasing solution ionic strength. The present results indicate that Fe/Al WTR is suitable for use as a soil amendment to prevent glyphosate pollution of aquatic ecosystems by enhancing the glyphosate retention capacity in soils.
铁/铝饮用水处理残余物（WTRs）是饮用水净化过程中普遍存在且无害的副产物，是草甘膦的经济高效吸附剂。鉴于草甘膦的反复施用会显著降低土壤对草甘膦的吸附能力，且吸附的草甘膦具有潜在的移动性，因此需要提高草甘膦在农业土壤中的吸附容量和稳定性，以防止草甘膦污染水体。因此，我们研究了将铁/铝WTRs作为土壤改良剂重复利用，以提高两种农业土壤对草甘膦吸附能力的可行性。批量实验结果表明，铁/铝WTRs改良剂显著提高了两种土壤对草甘膦的吸附能力（p<0.001）。在未改良的土壤中，高达30%先前吸附的草甘膦会解吸，而铁/铝WTRs改良剂有效降低了解吸的草甘膦比例。分级分析进一步表明，吸附在未改良土壤上的草甘膦主要保留在易分解部分（NaHCO₃-草甘膦）。WTRs改良剂显著增加了中度稳定部分（HCl-草甘膦）的相对比例，同时降低了NaHCO₃-草甘膦的比例，从而降低了土壤吸附的草甘膦释放到水相中的可能性。此外，铁/铝WTRs改良剂将溶液pH值升高对土壤草甘膦吸附的抑制作用降至最低，并减轻了溶液离子强度增加的影响。目前的结果表明，铁/铝WTRs适合用作土壤改良剂，通过提高土壤对草甘膦的吸附能力来防止草甘膦对水生生态系统的污染。
