拟除虫菊酯在城市地表灰尘-降雨径流系统中的迁移过程研究

Pyrethroids (Pys) insecticides are the major contributor to the toxicity for benthic organisms in urban waterways, and an important factor of the threat of aquatic environment. The former studies mainly used simulation experiment to investigate the transport behaviors on the earth surface. In urban environmental system, the urban surface dust is the main carrier of Pys, while the rainfall runoff is the primary dynamic factor for its transport. In this project, by field sampling and analysis methods, the transport process of Pys in the urban surface dust-rainfall runoff system will be studied. The accumulation characters of Pys in the dust, as well as the influencing factors (mineral compositions, particle size and physico-chemistry properties of dust, human activities, and ambient environment), will be explored. Moreover, under the interaction of rainfall, the partition characteristics of Pys among various matrices and the constraint mechanisms (wet deposition, runoff transport of suspended particles, and flush effect of the rainfall) will be investigated with emphases. The spatial and temporal distribution of Pys and its coupling mechanism with various environmental mediums in the urban environment will be illustrated. The obtained results will be of great importance for the profound understanding of the transportation mechanism and environmental fate of Pys in the urban ecosystem, and providing the scientific basis for the controlling and management of the non-point source pollution of Pys in the urban ecosystem.

拟除虫菊酯（Pys）类农药是导致城市水环境中底栖动物毒性的主要贡献者，成为威胁水生生态环境的重要因素。已有研究主要通过模拟实验研究Pys在城市地表的迁移行为。在城市环境系统中，地表灰尘是Pys的主要载体，降雨径流是Pys在城市地表迁移的主要动力因素。本项目拟采用野外采样分析的研究方法，考察Pys在城市地表灰尘-降雨径流系统中的时空分布与迁移过程，重点探讨Pys在城市地表灰尘的累积过程特征及其影响因素（地表灰尘的矿物组成、粒级与物理化学性质、人为活动及周边环境等），探究在降雨径流作用下，Pys在地表环境各介质中的分配特征及其制约机制（湿沉降、悬浮颗粒物径流迁移、降雨冲刷效应等），阐明Pys在城市环境的时空分布特征及其与多环境介质的耦合机制，深刻理解和掌握Pys在城市生态系统中的迁移机制与环境归宿，为Pys城市非点源污染控制与治理提供科学依据。

本项目采集广州城市地表灰尘、降雨地表径流、河流水体与表层沉积物样品，分析SPs在多种城市环境介质中的赋存与分配特征，探讨广州城市环境中拟除虫菊酯的来源与归趋，评价SPs对城市水环境的生态风险。广州城市路面灰尘与降雨径流中广泛检出拟除虫菊酯类农药，表明拟除虫菊酯类农药在城市环境中大量使用并能在地表灰尘累积，在降雨条件下附着于颗粒物上随着路面降雨径流迁移至城市水体。在广州城市河流水体和表层沉积物中也普遍检出8种拟除虫菊酯，主要是以氯氰菊酯和氯菊酯为主。水体和沉积物中拟除虫菊酯总浓度在丰水期显著高于枯水期，拟除虫菊酯浓度的空间分布主要受土地利用类型的影响，住宅区附近水体和沉积物中拟除虫菊酯浓度最高，这表明拟除虫菊酯在家庭蚊虫控制中的大量使用。拟除虫菊酯倾向于吸附在颗粒物上，路面降雨径流是拟除虫菊酯迁移至城市水环境的重要途径。近十年来，广州地区表层沉积物中拟除虫菊酯浓度呈现上升趋势，表明城市环境中拟除虫菊酯类农药（以氯氰菊酯和氯菊酯为主）的使用量也在逐年增加，并且拟除虫菊酯污染与城市化水平（如城市人口数和绿化面积）呈显著正相关性。此外，应用毒性单位和风险熵评价水体和沉积物中拟除虫菊酯（单个农药和混合物）对3种营养水平（藻类，水蚤和鱼类）的生态风险。尽管沉积物中拟除虫菊酯对3种营养水平（藻类，水蚤和鱼类）没有急性毒性，但毒性单位显示水蚤是水体中受拟除虫菊酯影响最敏感的物种，几个采样点水体中拟除虫菊酯对水蚤具有急性毒性。生态风险评估（风险熵）指出，水体和沉积物中拟除虫菊酯对三种营养水平（藻类，水蚤和鱼类）具有高风险，特别是水蚤和鱼类。