植物-土壤系统中氯硝柳胺迁移转化特征

为了解鄱阳湖流域施用氯硝柳胺灭螺可能对区域生态环境产生的影响,对氯硝柳胺在鄱阳湖植物-土壤系统中的迁移转化特性进行了盆栽实验研究。研究结果表明:氯硝柳胺在苔草、藜蒿根际土壤和空白土壤中降解符合一级动力学方程,半衰期分别为14.6、18.3、21.7 d;在植物-土壤系统中,植物根系会促进氯硝柳胺在土壤中迁移转化,转化的主要中间产物有2,5-二羟基苯甲酸,2-氯-4-硝基苯胺,2-氯-4-硝基苯酚,5-氯水杨酸等;苔草和藜蒿根际土壤中氯硝柳胺残留量与微生物数量均呈显著负相关(P0.05),其中,细菌在苔草根际土壤降解氯硝柳胺过程中起主导作用,而藜蒿根际土壤中起主导作用的微生物为放线菌;不同的时间,氯硝柳胺在苔草和黎蒿中的残留量及中间产物浓度不同;黎蒿地上、地下部分的最大残留浓度分别为2.47、0.99 mg·kg~(-1),均出现在盆栽的第10 d;苔草地上、地下部分的最大残留浓度分别为1.7、1.0 mg·kg~(-1),均出现在盆栽的第6 d。氯硝柳胺及其降解的中间产物在植物中残留时间较长,施药期间食用可食植物会存在一定的风险。

The migration and transformation characteristic of niclosamide in plant-soil system

Approximate 200 tons of niclosamide was directly added to Poyang Lake basin for snail control each year. Its degradation depends entirely on the natural environment, and it can influence the regional ecological environment. This study evaluated the migration and transformation properties of niclosamide in Poyang Lake plant-soil system by pot plant experiment. The results showed that the degradation of niclosamide in rhizosphere soil followed the first order kinetics equation, and the estimated half-lives were 14.6, 18.3, 21.7 d, respectively in Carex, Artemisia selengensis and blank soil. Plant roots could promote the degradation of niclosamide and niclosamide degraded to form a series of aromatic intermediates. The niclosamide residues in the rhizosphere soil had significant negative correlation (P<0.05) with microbial population. Moreover, it was bacteria in Carex rhizosphere soil and actinomycetes in Artemisia selengensis rhizosphere soil lead the key role in process of niclosamide degradation. Niclosamide residues and intermediate concentration in Carex and Artemisia selengensis were various along with time. The largest residual concentration of niclosamide was 2.47 mg·kg^-1 in Artemisia selengensis aerial part after cultivating 10 d, and it was 0.99 mg·kg^-1 in Artemisia selengensis root part after cultivating 10 d. The largest residual concentrations of niclosamide in Carex aerial and root part were 1.7 and 1.0 mg·kg^-1 respectively, and both appeared after cultivating 6 d. Our research indicated that niclosamide and intermediate products remained long in plants, which had some risk for edible plants.