杀虫剂三唑磷在室内淡水微宇宙中的生态效应

Ecological Effects of Insecticide Triazophos in Indoor Microcosms

作为一种中等毒性的有机磷杀虫剂,三唑磷在稻区的使用十分普遍。为弄清其对淡水生态系统的影响,选择5组浓度(0、0.35、1.75、17.5、52.5μg·L^(-1)),在以藻类作为营养源的室内微宇宙系统内进行研究,采用多变量分析软件CANOCO 5对数据进行分析。非限制性排序和多重比较的结果表明,给药后0~6 d,三唑磷对于浮游动物群落的最高无作用浓度(NOEC_(community))和最低有效浓度(LOEC_(community))分别为17.5μg·L^(-1)和52.5μg·L^(-1)。给药后第9天,最高浓度组(52.5μg·L^(-1))的群落结构开始恢复,此刻三唑磷在水中的实测浓度平均值为4.35μg·L^(-1)。对于单个物种种群密度做差异显著性分析和多重比较,结果显示浮游动物当中受影响最大的是绿色湖湾介Strandesia viridis。给药30 d后,该物种在52.5μg·L^(-1)处理组的种群密度明显下降,历时57 d的试验结束时,种群密度仍未恢复到对照水平。对于藻类,非限制性排序和多重比较的结果显示三唑磷在群落层次的影响未达到能够明显区分NOEC_(community)和LOEC_(community)的程度。在单物种层面,在给药后9~12 d,三唑磷对单细胞的羊角月牙藻Selenastrum capricornutum种群有刺激作用。其NOECspecies和LOECspecies分别为1.75μg·L^(-1)和17.5μg·L^(-1)。没有迹象表明三唑磷的引入能够明显改变水体pH、电导、浊度和水体C循环状况。结合暴露评估软件GNEEC(Version 2.0)输出的环境浓度(峰值为2.44μg·L^(-1)),本研究结果显示三唑磷在正常使用剂量下有可能对稻田周边浮游动物群落的内部结构造成扰动,但是它不会对整个系统造成不可恢复的影响。

As a type of organophosphorus compound with moderate toxicity,triazophos is widely used in areas of rice production. To clarify the impact of the insecticide on freshwater ecosystems,five concentrations（0,0. 35,1.75,17. 5,and 52. 5 μg·L^-1） of the insecticide were tested in a set of algal-dominated indoor aquatic microcosms.The data were analyzed by CANOCO 5,a type of software for multivariate data analysis. Results of the unconstrained ordination and the followed multiple comparisons indicated that the highest no-effective concentration and the lowest effective concentration with respect to the eigenvectors of zooplankton communities（ i. e. NOECcommunity and LOECcommunity） was 17. 5 μg·L^-1and 52. 5 μg·L^-1,respectively,from 0 to 6 d. The communities being exposedto the highest concentration（ i. e. 52. 5 μg·L^-1） recovered at 9 d,and the average value of the actual concentrations at the date was found to be 4. 35 μg·L^-1. Results of the multiple comparisons with respect to population densities of single-species indicated that the species that was mostly affected was Strandesia viridis. In group of 52. 5 μg·L^-1,the populations began to shrink at 30 d and they did not recover at the end of the 57 d exposure. For algae,results of the unconstrained ordination and the followed multiple comparisons showed that the impact of triazophos at community level was not so obvious as to identify the value of NOECcommunityand LOECcommunity. The insecticide was found to induce the population of unicellular species Selenastrum capricornutum from 9 - 12 d,with NOEC speciesand LOEC speciesbeing 1. 75 μg·L^-1and 17. 5 μg·L^-1,respectively. There was no evidence that the insecticide altered p H,conductivity,turbidity,and carbon cycle of the dilutions. To take the environmental concentrations that was estimated from GNEEC（Version 2. 0）,which show the peak value of 2. 44 μg·L^-1,into consideration,results of the study suggest that the triazophos may disturb the intrinsic structure of zooplankton communities close to paddy fields even it was applied at recommended rates,but the insecticide was unlikely to cause unrecoverable damage to the systems.