添加给水厂残泥对稻田土壤中毒死蜱环境赋存及厌氧降解的影响
Effect of drinking water treatment residuals on speciation and anaerobic degradation of chlorpyrifos in paddy soil
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摘要: 给水厂残泥(WTR)是给水厂混凝过程产生的安全废弃物,是一种高效低廉的毒死蜱吸附材料。为评估将WTR作为吸附材料添加于土壤中缓解毒死蜱危害的可行性,探究了添加WTR对稻田土壤中毒死蜱环境赋存、厌氧降解及其代谢产物TCP形成的影响。实验结果表明:毒死蜱首要厌氧降解途径是快速水解为TCP,添加WTR显著降低了土壤中毒死蜱与TCP的生物有效性(P<0.05)。72 d厌氧培养时间内,未添加WTR土壤中高达79%的毒死蜱主要以生物可利用态存在;在WTR添加土壤中,72%~95%的毒死蜱以稳定的残渣态存在,但毒死蜱在土壤中的降解速度因此减慢,TCP生成量随之减少。在未添加WTR土壤中,92%以上的TCP以水溶态为主,添加WTR可有效减少其水溶态所占比例,WTR添加量为10%时,其水溶态含量降至47%。随着WTR添加量增加,毒死蜱与TCP由土壤向上覆水迁移的量显著减少(P<0.05)。未添加WTR的土壤水溶液体系上覆水中毒死蜱和TCP浓度分别高达537 μg·L-1和1 750 μg·L-1,添加2%WTR可使其最高浓度分别降低50%。在厌氧滞水的稻田土壤中,WTR主要金属元素(Fe、Al和Mn)稳定性强,二次污染风险较低。综合以上研究结果,WTR适于作为土壤添加物应用于毒死蜱与TCP污染控制。Abstract: Chlorpyrifos can be effectively adsorbed by drinking water treatment residuals (WTR), the ubiquitous and non-hazardous by-products of potable water production. To assess the feasibility of WTR amendment for attenuation of chlorpyrifos and its major metabolite TCP pollution, the effect of WTR amendment on the speciation and anaerobic degradation of chlorpyrifos in paddy soil, as well as the TCP formation, was examined in the present study using the incubation test. Results showed that hydrolysis was the major pathway of chlorpyrifos anaerobic degradation and TCP was the major hydrolysis product in the soil-aquatic environment. The bioavailability of chlorpyrifos and TCP was considerably reduced by WTR amendment (P<0.05), resulting in a reduced chlorpyrifos degradation rate and a decreased quantity of TCP formed in chlorpyrifos-contaminated soils. During the anaerobic incubation period, up to 79% of the total chlorpyrifos existed as the bioavailable form in non-amended soil, while 72% to 95% of the total chlorpyrifos existed as the stable residule form in WTR-amended (2% to 10%, mass fraction) soil. Water-extractable fraction was the major form of TCP in soil, and amending 10% (mass fraction) WTR could effectively reduced the water-extractable fraction of TCP from 92% to 47%. The WTR amendment also significantly reduced the quantity of chlorpyrifos and TCP migrating from soil into overlying water (P<0.05). In the non-amended soil-water environment, the concentrations of chlorpyrifos and TCP reached up to 537 μg·L-1and 1 750 μg·L-1, respectively. Following 2% WTR amendment, both the concentration was reduced by 50%. The major metals within WTR (Fe, Al and Mn) was stable without low release risk in the anaerobic-flooded soil environment. Results obtained in the present study indicate a great deal of potential for the beneficial reuse of WTR as soil amendments for chlorpyrifos and TCP pollution control.
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Key words:
- drinking water treatment residual /
- paddy soil /
- chlorpyrifos /
- anaerobic degradation
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