25 g·L^(-1)五氟磺草胺可分散油悬浮剂对水生无脊椎动物的毒性效应及生态风险评估

Toxicity and Ecological Risk Assessment of 25 g·L^(-1)Penoxsulam OD on Aquatic Invertebrates

五氟磺草胺是当前我国稻田用量较大的一种除草剂。为明确其施用后对水生生物的毒性和环境风险,寻找较适合南方稻区农药生态毒理学检测的指示生物,为稻田环境风险评价提供更可靠的科学依据,本研究选取了25 g·L^(-1)五氟磺草胺可分散油悬浮剂为受试农药,比较其对模式生物大型溞和南方常见物种发头裸腹溞的急性活动抑制试验和繁殖试验结果。急性活动抑制试验结果表明,25 g·L^(-1)五氟磺草胺可分散油悬浮剂对大型溞、发头裸腹溞的48 h-EC_(50)(95%置信限)分别为0.81 mg a.i.·L^(-1)(0.54~1.18 mg a.i.·L^(-1))、0.52 mg a.i.·L^(-1)(0.33~0.85 mg a.i.·L^(-1)),其毒性均为高毒;繁殖试验结果表明,25 g·L^(-1)五氟磺草胺可分散油悬浮剂对大型溞的21 d无可观察效应浓度(NOEC)为1.22×10^(-3)mg a.i.·L^(-1);对发头裸腹溞的14 d无可观察效应浓度(NOEC)为7.66×10^(-4)mg a.i.·L^(-1);采用TOP-RICE暴露模型进行初级评估发现,25 g·L^(-1)五氟磺草胺可分散油悬浮剂对大型溞的急性风险可接受,但对发头裸腹溞的急性、无脊椎动物(慢性)风险不可接受;进一步采用物种敏感性分布(SSD)法进行高级评估,发现五氟磺草胺对无脊椎动物的急性风险可接受,但对无脊椎动物的慢性风险不可接受。本研究结果表明,五氟磺草胺对南方溞种发头裸腹溞有潜在生态风险,建议该除草剂在稻田使用中,应重视其对水生无脊椎动物的风险,不可盲目加大用量;同时基于物种分布和风险考虑,建议采用更敏感的发头裸腹溞作为南方稻田农药生态毒理学检测的指示生物。

Currently,penoxsulam is a herbicide that widely applied in paddy fields in China.The aim of this study was to clarify the toxicity and risk of penoxsulam to aquatic organisms,and find the most suitable indicator organisms for evaluating pesticide environmental risk in southern rice areas,which will provide more reliable scientific basis for environmental risk assessment of rice field.In this study,the oil dispersion(OD)of 25 g·^(-1)penoxsulam was selected as the tested pesticide to compare its acute activity inhibition and reproduction influence on D.magna and M.irrasa.The results of acute activity inhibition test showed that 25 g·L^(-1)penoxsulam OD had high acute toxicity against D.magna and M.irrasa,their 48 h-EC_(50) were 0.81 mg a.i.·L^(-1)with 0.54~1.18 mg a.i.·L^(-1)of 95%confidence limit,and 0.52 mg a.i.·L^(-1)with 0.33~0.85 mg a.i.·L^(-1)of 95%confidence limit,respectively.The results of the reproduction test showed that the 21 d no observed effect concentration(NOEC)of 25 g·L^(-1)penoxsulam OD for D.magna was 1.22×10^(-3)mg a.i.·L^(-1),while the 14 d-NOEC for M.irrasa was 7.66×10^(-4)mg a.i.·L^(-1).The primary risk of 25 g·L^(-1)penoxsulam OD obtained by junior assessment of TOP-RICE exposure model was acceptable for D.magna in acute risk,but not for M.irrasa in acute risk,and not for invertebrate in chronic risk.Further using advanced assessment of species sensitivity distribution(SSD)analysis,it is found that it was acceptable for invertebrate in acute risk,but not for invertebrate in chronic risk.This study demonstrates that penoxsulam had a potential ecological risk to M.irrasa.It is suggested that the application of penoxsulam in the paddy field should be paid more attention to,and the dosage cannot be increased blindly.Based on considerations about species distribution and risk,M.irrasa can be used as a pesticide indicator organism for ecotoxicology study in paddy fields.