抗生素解离形态对其植物富集及人体暴露的影响

Influence of Ionization Forms of Antibiotics on Plant Accumulation and Human Exposure

抗生素通过畜禽有机肥、灌溉用水等途径进入土壤,被植物吸收后会进入食物链,可能引起人体的被动暴露。研究植物对抗生素的富集规律可以为评价人体健康风险提供参考。很多抗生素属于可解离有机物,在不同pH下会呈现出不同的解离形态,这导致其植物吸收富集机制非常复杂。目前,关于植物对不同形态抗生素吸收的研究还比较缺失。本研究选取磺胺嘧啶(SDZ)、磺胺甲恶唑(SMX)、甲氧苄啶(TRM)、氯霉素(CAP)、克拉霉素(CLA)和恩诺沙星(ENR)作为目标抗生素,分别在pH 6.5和pH 5~9条件下进行了水培暴露实验,研究了抗生素在小麦和生菜中的富集规律。结果表明,50μg·L^(-1)抗生素暴露下,6种抗生素在小麦和生菜根部的富集大致表现为ENR>TRM>CAP>CLA>SMX>SDZ。在生菜对抗生素的根部吸收中,随着pH升高,SDZ和SMX的吸收呈显著下降趋势,而其他4种抗生素随着pH变化吸收差异不显著。通过分析抗生素形态与其吸收的关系发现,SDZ、SMX和CLA在生菜中的富集与其中性形态比例成正相关关系,R 2分别为0.931、0.926和0.751,表明中性形态对其植物吸收具有比较重要的贡献。在本研究暴露水平下,生菜可食用部分中目标抗生素的人体每日预估摄入量(EDI)均低于每日允许摄入量(ADI);但是,在pH 5~9之间同种抗生素的EDI存在16倍的差异,抗生素通过植物富集可能产生的人体健康风险仍需进一步研究。

Antibiotics enter the soil through livestock and poultry organic fertilizer,irrigation water and other ways.After absorbed by plants,antibiotics will enter the food chain,and may cause passive exposure of human body.Study about the accumulation of antibiotics in plants can provide references for evaluation of human health risks.Many antibiotics belong to ionizable organic compounds,and they exist as different ionization forms at different pH values,which leads to a very complicated mechanism of absorption and accumulation by plants.At present,the research on the effect of ionization forms on absorption of antibiotics by plants is still lacking.In this study,sulfadiazine(SDZ),sulfamethoxazole(SMX),trimethoprim(TRM),chloramphenicol(CAP),clarithromycin(CLA)and enrofloxacin(ENR)were selected as target antibiotics,and the hydroponic exposure experiments were carried out under pH 6.5 and pH 5~9 for wheat and lettuce respectively to study the accumulation rules of antibiotics.The results showed that the enrichment of six antibiotics in wheat and lettuce roots under the exposure of 50μg·L^(-1)antibiotics was roughly as follows:ENR>TRM>CAP>CLA>SMX>SDZ.In the root absorption of antibiotics by lettuce,with the increase of pH,the absorption of SDZ and SMX showed a significant downward trend,while the absorption of other four antibiotics had no significant difference with the change of pH.By the analysis of the relationship between antibiotic forms and their absorption,it was found that the accumulation of SDZ,SMX and CLA in lettuce was positively correlated with the proportion of its neutral forms,with R 2 of 0.931,0.926 and 0.751,respectively,which indicated that the neutral forms had an important contribution to its plant absorption.Under the exposure level of this study,the estimated daily intake(EDI)of target antibiotics in edible part of lettuce is lower than the acceptable daily intake(ADI),however,there is a 16-fold difference in EDI of the same antibiotic among pH 5~9,and the possible human health risks caused by the accumulation of antibiotics by plants still need further study.