典型灌区稻田多氯联苯残留特征及生态风险评估

PCBs residues characteristics and ecological risk assessment in paddy fields of typical small watershed

以南方典型小灌区的两块稻田为试验小区,采用GC-ECD对其田间水体和土壤中EPA优控14种多氯联苯(PCBs)进行了检测和定量分析。结果表明,14种PCBs同系物有不同程度检出,优势残留物主要以3氯和5氯取代PCBs为主,水和土壤占PCBs总量的88.24%、90.13%。水中∑PCBs质量浓度为24.09～310.34ng·L-1,其中地表水均值为245.84ng·L-1,地下水均值为96.46ng·L-1;土壤中∑PCBs质量分数为10.01～54.63ng·g-1,均值为33.92ng·g-1。稻田地表水中的PCBs质量浓度远高于地下水,垂向迁移明显但速度较慢;稻田地表及地下水中PCBs质量浓度有随时间衰减的趋势,可能与水稻的生育周期有关;淹灌处理稻田PCBs质量分数高于节水灌溉。研究区毒性当量TEQ在2.65×10-2～7.54×10-2pg·g-1之间,生态风险处于中等水平。地表及地下水均遭到污染,再加上PCBs具有生态累积效应,危害不容忽视。

14 kinds of PCBs were determined in the paddy field＇s water and soil of Dragon Bridge, Nanjing, P. R. China, whieh was a typical small watershed irrigated area. The results showed that： 14 congeners of PCBs were detected at different residue levels, the dominant components of PCBs were tri-, tetra-, and penta-chlorinated PCB congeners, accounting for 88.24%, 90.13% of total PCBs. The concentration range of PCBs in the water of paddy field was 24.09-310.34 ng.L^-1, their mean content in surface water was 245.84 ng.L^-1 and that in groundwater was 96.46 ng.L^-1. The concentration range of PCBs in sediment was 10.01-54.63 ng·g^-1, and their mean value was 33.92 ng.g^-1. The content of PCBs in surface water was much higher than that in groundwater, the trend of vertical migration in the paddy field was very obvious but the migration velocity of that was a bit slow. The risk assessment on PCBs in the soil was completed by using TEQ method. The range of ∑TEQ was 2.65× 10^2-7.54 ×10^-2 pg.g^-1, the ecological risk of research area was at a medium level in China. Surface water and groundwater were all contaminated. The potential hazards should not be ignored for their accumulative effect in the environment.