西南岩溶地区农业湿地有机氯农药分布及其多水塘-人工湿地净化研究

The distribution characteristics of organochlorine pestcides (OCPs) residues in agricultural wetland in karst area of Southwest China and the mechanisms of multipond-artificial wetland in OCPs treatment will be investigated in this project. Based on the detection of concentration level and component of OCPs residues in the paddy filed, canal, ponds, and reservoir along the horizontal direction in agricultural wetland, and the detection of concentration level and component of OCPs in different vertical layer of the soil, sediment, surface water, groundwater and plants, the distribution characteristics and source identification of OCPs in agricultural wetland system will be studied then. In addition, the risk level of OCPs in agricultural wetland system will be analyzed. Furthermore, the movement rule and machanism of OCPs in agricultural wetland will be investigated. Several ponds with water relation will be selected to establish a multipond system, and an artificial wetland will be built at the bottom of the multipond to constitute the multipond-artificial wetland system which can make the water flow circularly flow between the multipond system and artificial wetland. And the substrate and plant will be screened in the artificial wetland. The multipond-artificial wetland system is operated and debugged according to the distribution characteristics of OCPs and the influence factors on the movement rule of OCPs. The operating parameter of multipond-artificial wetland system is determined based on the evulation of the OCPs Treatment. And the mechanisms of multipond-artificial wetland system in OCPs treatment will be illustrated through the analysis of the change of OCPs concentration level in sediment and water flow in multipond. And the resultes can provide the scientific evidence for the risk assessment and control measure of OCPs in agricultural wetland in karst area of Southwest China, and it is extraordinary significant to the eco-environment protection and the drinking water security.

系统研究西南岩溶地区农业湿地系统水平方向上田间―渠系―水塘―水库有机氯农药(OCPs)含量和组分的差异，以及农业湿地内土壤、底泥、地表水、地下水、植物等垂向方向OCPs含量和组分的不同，评估OCPs的风险水平，阐明OCPs的污染特征和分布规律，描述农业湿地系统OCPs运移规律及机理。开展野外原位OCPs净化试验，选择有水力联系的自然水塘建立多水塘系统，在多水塘末端构建人工湿地，筛选对OCPs高吸附率的人工湿地基质和植物。针对农业湿地系统OCPs污染特征和运移的影响因素，运行和调试多水塘―人工湿地耦合系统，评价其对OCPs的去除效果，优选耦合系统运行的特征参数。通过农业湿地系统底泥、水流等OCPs浓度变化和耦合系统运行分析，阐明多水塘―人工湿地耦合系统对OCPs的净化机理。研究成果可为西南岩溶地区农业湿地系统OCPs风险评估、修复治理提供科学依据，对于生态保护、饮用水安全等具有重要意义。

有机氯农药（OCPs）是农业面源污染中的一类高风险污染物，对环境生态系统和人类健康可构成严重威胁，是一类社会公认的环境优先控制的持久性有机污染物。本项目研究了桂林青狮潭区域农业湿地中不同介质的OCPs浓度水平、组成、时空变化和生态风险水平，从水平和垂直两个方向探讨农业湿地系统OCPs的分布和运移规律；以筛选的湿地基质和植物构建人工湿地系统，通过静态和动态实验探讨了典型OCPs在人工湿地系统的净化过程及其机理。项目首先确定和优化了水体、底泥和植物等介质中OCPs的检测方法，方法的加标回收率为68.73%～110.26%，RSD为0.3%～19.6%。农业湿地各介质中共检出15种OCPs，水体、土壤（底泥）和植物中∑OCPs分别为73.40～313.62ng/L、27.26～319.59ng/g、12.90～72.20ng/g，其中HCHs和DDTs分别占23.90%～84.29%和23.90%～79.03%，是该地区农业湿地系统OCPs的主要组分，特征组分比例表明HCHs和DDTs均源自历史残留。研究区域不同水体中OCPs浓度分布呈现为池塘>西湖>溪流>东湖，在垂直方向上表现为下层水>上层水>中层水，在时间上呈现为丰水期>春汛期>平水期>枯水期；土壤和沉积物中OCPs分布表现为稻田土壤>池塘底泥>水库沉积物，垂直方向分布呈现为上层>中层>下层，时间上呈现为春汛期≥平水期>丰水期>枯水期；植物中∑OCPs表现为根部>茎部>叶部，不同采样点土壤和植物中OCPs变化规律一致。OCPs随地表径流在农业湿地水平方向上沿田间―渠系―水塘―水库迁移，垂向迁移极为缓慢、层次分布明显；丰、枯水期和冬、夏季节介质中∑OCPs有明显区别，表明水分运动和温度变化均影响了农业湿地介质中OCPs的分布和运移。基于风险评估值（ERL和ERM）和CA模型的生态风险评价发现沉积物和水中残留的OCPs存在中等偏高的生态风险。静态和动态实验结果表明，以菖蒲和土壤构建的人工湿地对β-HCH的净化能力明显高于单独的湿地植物和基质作用，而基质的吸附作用远大于植物；随着处理水力负荷增大，人工湿地的净化效率呈微弱上升趋势。本研究初步揭示西南岩溶地区农业湿地系统OCPs的运移规律及其影响因素以及净化过程，为OCPs风险评估、修复治理提供了科学依据。