环草隆与镉复合污染对城市绿地重金属污染土壤有机氮矿化量、基础呼吸和土壤酶活性的影响

Combined Effects of Siduron and Cadmium on Organic Nitrogen Mineralization,Basal Respiration and Enzyme Activities in Heavy Metal Polluted Urban Soil

环草隆是北方城市应用较为广泛的一种草坪除草剂,重金属镉是土壤中常见的重要污染物,二者在土壤生态系统中存在联合暴露的潜在风险。为了准确评价城市绿地土壤重金属和农药复合污染的生态风险,选择不同重金属污染程度的土壤为研究对象,在室内模拟条件下,探讨了环草隆与镉复合污染对土壤有机氮矿化量、基础呼吸及土壤酶活性的影响。研究发现：环草隆与镉复合污染对各试验指标的影响均达到极显著水平（P〈0.01）;与镉复合污染能明显改变环草隆的微生物毒性效应,并且Cd对环草隆毒性效应的影响与二者浓度配比有很大关系,Cd浓度由1 mg·kg-1升高到10 mg·kg-1,环草隆浓度与样点G土壤有机氮矿化量变化率的线性关系由正相关变为负相关;复合污染下,根据剂量-效应关系计算的EC50值27.6~848mg·kg-1,远远高于环草隆草坪建议施用量（3.33 mg·kg-1）;土壤中环草隆与镉复合污染的联合毒性效应受土壤理化性质及重金属含量影响较大,另外,二者复合效应也会随污染物浓度及试验指标的不同而不同。以上研究结果能够为城市土壤重金属和除草剂复合污染生态风险评价提供基础数据和技术方法。

In northern cities, siduron is widely used in lawn management, and soil contamination of heavy metal like Cd commonly exists in urban green land. Thus, combined exposure of siduron and Cd is very likely in the ur-ban green land soil ecosystem. In this research, three urban soils polluted by different level of heavy metals （marked as N,D,G） were selected to evaluate the ecological risk of combined pollution of heavy metals and herbi- cide. Combined effects of siduron and Cd on soil organic nitrogen mineralization, basal respiration and soil enzyme activities were studied. It was suggested that： the single and combined effects of siduron and Cd on experimental indexes were markedly significant （P〈0.01）. Presence of Cd obviously changed the toxic effect of siduron on mi- croorganisms and the effect of Cd was dependent on concentration of siduron and Cd. When Cd concentrations in- creased from 1 mg.kg＂ tol0 mg.kg＂1, the linear relationship between siduron concentrations and the change rate of organic nitrogen mineralization in soil G changed from positively to negatively. Under combined pollution, the val- ues of EC50（27.6 - 848 rag. kg-1） obtained based on the dose- effect relationship were well above the suggested dos- age of siduron （3.33 mg.kg＇l）. The combined effects of siduron and Cd on these selected indexes were greatly in- fluenced by soil physical and chemical properties and heavy metal contents. In addition, the combined effects both varied with their concentrations and experimental indexes. The above results can provide basic data and technical methods for the ecological risk assessment of combined pollution of heavy metals and herbicide in urban soil.