水稻用药策略风险评估与安全性分析

Evaluation of pesticide application strategy in rice and risk assessment

[目的]本文旨在对水稻全生育期使用的农药进行膳食暴露风险评估和土壤生态环境影响分析,以评估农药使用策略的合理性。[方法]对江苏省、江西省单季稻-双季稻种植区的农药使用情况及其在稻米和土壤的残留情况进行长期调查,对减施农药示范区和常规施药对照区的稻米和不同生育期(分蘖期、抽穗期和收获期)的稻田土壤进行残留监测,采用膳食暴露评估模型和生态相对风险模型(EcoRR)对急、慢性膳食暴露风险和生态环境风险进行评估。[结果]水稻上常规使用的51种农药,有4种在收获的稻米中检出,其中吡蚜酮和己唑醇具有较高的检出率,分别为93.00%和28.75%,毒死蜱和戊唑醇检出率为14.29%和7.14%。急、慢性膳食暴露风险评估表明:稻米中残留的吡蚜酮、己唑醇、毒死蜱和戊唑醇对不同年龄人群的食用安全风险较低,减施农药仍可进一步降低膳食暴露风险。对水稻不同生育期土壤中农药残留的调查表明,有13种农药在土壤中检出,其中三环唑、己唑醇和丙环唑检出率为100%,这与其较长的半衰期、使用频率以及在前茬作物的使用有关。生态风险评估表明:减施农药能够降低稻田生态环境风险,其中穗期减少吡蚜酮的施用量对稻田生态风险的降低效果最为显著,部分地区可由中等风险转变为低风险或无风险级别。生态风险贡献率分析表明:吡蚜酮的风险贡献率最高,在水稻分蘖期、抽穗期、收获期分别为54.16%~83.68%、19.07%~84.39%和0.00%~82.32%;其次是分蘖期丙草胺、抽穗期苯醚甲环唑和收获期丙环唑的使用,风险贡献率分别为0.00%~71.50%、0.00%~68.95%和1.12%~62.24%,亦是影响稻田生态风险的关键药剂。[结论]减少关键农药品种在水稻不同生长时期的使用,可以显著降低其生态环境风险,特别是吡蚜酮、苯醚甲环唑、丙环唑和丙草胺的合理使用,是调控稻田生态环境安全的关键。

[Objectives]This paper aimed to evaluate the validity of pesticides application strategy in rice,and analyse the risk of dietary exposure and ecological impact.[Methods]This study implemented long-term investigation on usage and residual details of pesticides using for pest control in single-season and double-season rice of Jiangsu and Jiangxi provinces.Investigation of pesticides residues in rice and soil had been conducted in the period of tillering,heading and harvesting stage,and the results had been compared between the pesticide reduction strategies adopted area and the regular integrated pest management(IPM)adopted area.Acute and chronic dietary exposed risk and ecological impact risks had been evaluated by using the dietary exposure risk assessment model and the ecology relative risk model(EcoRR).[Results]The results revealed that,4 of total 51 pesticides used in rice for pest control,had been found in the harvest brown rice.Pymetrozine and hexaconazole were the most frequently found pesticides in all rice samples with the frequency up to 93.00%and 28.75%,followed by 14.29%and 7.14%for chlorpyrifos and pentazolidol,respectively.However,the risk assessment of acute and chronic toxicity that may be caused by these 4 pesticides through dietary exposure,was finalized to be negligible for all populations divided by age.Adopting pesticide reduction strategies could further low the risk of dietary exposure.As for the soil sampled from the period of tillering,heading,and harvesting stages of rice,13 different kinds of pesticides were found,tricyclazole,hexaconazole and propiconazole with 100%detection rates in particular.It could be explained by the long half-life periods of these pesticides and the remains of previous residue.The ecological risk assessment showed that the reduction use of pesticides could decrease the ecological risks significantly,even down to low level from medium level risk.It was found that the most effective effort of reducing the ecological impact was to decrease the use of pymetrozine,as this pesticide played a key role to the contribution of ecological risks in the period of tillering,heading,and harvesting(54.16%-83.68%,19.07%-84.39%,and 0.00%-82.32%respectively).Secondly,the use of pretilachlor at tillering stage,difenoconazole at the heading stage and propiconazole at the harvest stage was considered to be alternative key elements for the cause of ecological risk,with contributions of the risk ratios of 0.00%-71.50%,0.00%-68.95%and 1.12%-62.24%,respectively.[Conclusions]Reducing the use of specific pesticides in the particular growth period of rice could reduce ecological impact and dietary exposure significantly.Pymetrozine plays a key role for ecological impact,followed by difenoconazole,propiconazole and pretilachlor,which should be used appropriately.