水培蕹菜使用吡唑醚菌酯的水生生态系统风险评估

为研究水培蕹菜使用吡唑醚菌酯对水生生物的潜在影响，在水培蕹菜白锈病发病初期，喷施25%吡唑醚菌酯悬浮剂和9%吡唑醚菌酯微囊悬浮剂，测定水培蕹菜和水体中的吡唑醚菌酯残留量，并结合毒理学数据评估其对水生生态系统的暴露风险。结果表明：吡唑醚菌酯在水培蕹菜和水中降解较快。悬浮剂和微囊悬浮剂在植株中的消解半衰期分别为2.9 d和3.9 d，微囊悬浮剂较悬浮剂在植株上的持效期更长。两种剂型在水中的消散半衰期都小于2 d，微囊悬浮剂在水中的有效浓度小于悬浮剂。基于暴露浓度峰值和时间加权平均浓度进行风险评估，悬浮剂对水生脊椎动物和无脊椎动物的急性和慢性风险商值，及其对初级生产者的慢性风险商值均大于1；微囊悬浮剂对每一类水生生物的风险商值都小于悬浮剂，但其对水生生物的急性暴露风险同样不可接受（风险商值仍大于1），慢性风险商值仅在基于时间加权平均浓度计算时小于1。研究表明，吡唑醚菌酯在水培蕹菜上使用对水生生态系统的风险不容忽视，应重点关注鱼和无脊椎动物的暴露风险。建议在水生蔬菜生产中谨慎使用吡唑醚菌酯，同时修订吡唑醚菌酯在水生蔬菜上的限量标准。

Risk assessment of aquatic ecosystem using pyraclostrobin in water spinach(Ipomoea aquatic Forsk) cultured in aquatic environment

In order to study the potential effects of pyraclostrobin exposure on the aquatic ecosystem, 25% pyraclostrobin suspension concentrate(SC)and 9% pyraclostrobin microcapsule suspension(CS)were sprayed on water spinach(Ipomoea aquatic Forsk)cultured in aquatic environments, at the initial stage of white rust. Residues of pyraclostrobin in the plant and water were detected, and the risk assessment of pyraclostrobin in aquatic ecosystem was conducted in combination with toxicological data. The dissipation of pyraclostrobin both in the water spinach and water were rapid. The half-lives of 25% pyraclostrobin SC and 9% pyraclostrobin CS in the plant were 2.9 d and 3.9 d, respectively. Compared with the SC formulation, the CS formulation had a longer effective period in the plant system. In water, both the formulations had very short half-lives of less than 2 days. The effective concentration of the CS formulation in water was less than that of the SC formulation. Based on the maximum environmental concentration and time-weighted mean concentration(TWM), the risk assessment results revealed that 25% pyraclostrobin SC posed unacceptable acute and chronic risks to vertebrates and invertebrates, as well as unacceptable chronic risks to primary producers. While the risk quotient(RQ)of 9% pyraclostrobin CS for each group of aquatic organisms was relatively less than that of 25% pyraclostrobin SC, its acute risks to vertebrates and invertebrates were still unacceptable, and the chronic RQ was less than 1 only in the TWM scenario. Our results indicated that the risk posed to aquatic ecosystems by pyraclostrobin products used on water spinach grown in water could not be ignored. Fish and invertebrates were the sensitive aquatic organisms of concern. Hence, some suggestions were put forward, such as avoiding using pyraclostrobin on aquatic vegetables, and revising proposed maximum residue limits for pyraclostrobin in aquatic vegetables.