环草隆与重金属复合污染对黄瓜及小麦的毒性效应评估

为探究草坪除草剂与重金属复合污染对高等植物的生态毒性效应,以小麦与黄瓜为敏感受试植物,采用滤纸发芽试验法,研究了典型草坪除草剂环草隆与4种重金属(Cu/Zn/Pb/Cd)单一及复合污染条件下,对2种植物种子萌发与幼苗生长的毒性效应并进行评估。在此基础上采用评估因子法外推环草隆在土壤中的预测无效应浓度(PNECsoil)。结果表明,2种植物的根长及小麦的芽长对环草隆与重金属非常敏感(P<0.01),且存在明显的剂量-效应关系。黄瓜根长对环草隆最敏感,根长半抑制浓度(RI50)为0.281 mg·L-1。小麦根长对Cu、Pb、Cd比黄瓜根长更敏感。环草隆与重金属复合污染时,黄瓜根长表现得最为敏感,可作为敏感生物标记物。环草隆与重金属复合污染对小麦及黄瓜根长抑制具有协同作用,并且随着重金属浓度的增大,黄瓜和小麦根生长对环草隆的敏感性增加。环草隆与重金属复合污染对小麦芽长的联合效应主要与重金属种类及其暴露浓度有关。以黄瓜的根伸长抑制率为急性毒性终点,利用外推法计算得环草隆在土壤中的PNECsoil为1.90μg·kg~(-1),远远低于环草隆田间推荐使用量1.5~9 mg·kg~(-1)。与重金属复合污染时,环草隆的PNECsoil明显降低,导致其生态风险提高。上述研究结果能够为草坪除草剂环草隆与重金属复合污染的生态风险评价提供数据支持。

Joint Toxicity Assessment of Siduron and Heavy Metals on Cucumber and Wheat Seed Germination and Seedling Growth

In order to reveal the joint toxicity of typical lawn herbicide siduron and heavy metals on terrestrial plants,wheat and cucumber were exposed to single and combined treatment of siduron and four heavy metals.The germination rates,biomass and the elongation of root and shoot of tested plants were detected.The predicted no effect concentration (PNECsoil) for siduron in soil was calculated using assessment factors.Results showed that siduron and heavy metals had significant single and joint effects on root elongation of both plants and shoot elongation of wheat (P＜0.01).Apparent does-effect relationships were demonstrated.Cucumber was more sensitive to siduron than wheat.RI50 of cucumber in root elongation was 0.281 mg·L-1.Wheat was more sensitive to Cu,Cd,Pb than cucumber.When we combined siduron and those four heavy metals,cucumber root elongation was the most sensitive parameter,which thus could be selected as biomarker.Siduron and those four heavy metals had a synergieffects on the inhibition of wheat and cucumber root elongation.Compared to single treatment of siduron,root elongation of both plants were more sensitive to siduron with the addition of heavy metals.Joint toxicity of siduron and those four heavy metals to wheat shoot depended more on individual heavy metal and exposing concentration.PNEC of siduron in the soil (PNECsoil) derived from the acute toxicity data of cucumber root elongation inhibition using equilibrium partitioning was about 1.90 μg· kg-1,which was far below the recommended application dose of 1.5-9 mg·kg-1 siduron in field.When combined with heavy metals,the PNECsoil of siduron significantly decreased,which may lead to increased ecological risk.Results presented in this study can provide basic data for ecological risk assessment of combined pollution of siduron and heavy metals.