稳定铅同位素研究典型城市景观条件下大气-土壤系统中重金属的扩散交换

Trace metal contamination in air and soil of urban environments has potential adverse effect to human health. In this proposal, atmospheric particulate, atmospheric deposition (dry and wet), soil dust and soil samples will be collected from typical urban areas with different land uses. In addition, resuspended soil dust and soil particulates will be collected by using a resuspension chamber in the laboratory. The aims of the planned study are to investigate the contribution of atmospheric deposition and vehicle emissions on trace metal loadings to urban soils and the potential of resuspended soil dust to atmospheric particulates using stable lead isotopes as a tracer. The project will also address the effects of typical urban landscapes on atmospheric deposition of metal contaminants, and resuspension of metal containing particles from soils. The proposed project will study the health effects of heavy metals in soil dust using their different chemical fractions and bioaccessibility. The results of the planned research project will provide new insights for better understanding of trace metal geochemical cycling and environmental fate in typical urban environments and the generated data will facilitate more objective assessment of health risk of trace metal pollution in air and soil systems.

城市大气和土壤环境重金属污染与城市居民身体健康休戚相关，是一个需要持续研究的热点问题。本项目采用铅同位素示踪手段，通过野外实地大气颗粒物、大气干湿沉降、土壤灰尘及土壤等样品的采集以及室内土壤颗粒可悬浮性实验，研究城市大气污染物的沉降对土壤重金属积累的影响以及土壤颗粒的再悬浮对大气颗粒物重金属的贡献；通过对比不同城市景观条件下研究结果的差异，分析典型城市景观（交通和工业分布、建筑分布、绿化）对大气重金属沉降以及土壤重金属再悬浮的影响；同时，通过分析不同来源、不同粒径的土壤灰尘及土壤重金属的化学赋存形态以及生物有效性，评估其潜在的环境危害和健康风险。本项目的研究结果将为更深入地了解重金属在城市环境中的迁移规律以及更合理地评价城市重金属污染的健康风险提供新的理论依据。

本项目采用铅同位素示踪手段，通过野外实地大气降尘及土壤等样品的采集以及室内土壤颗粒可悬浮性实验，研究城市大气污染物的沉降对土壤重金属积累的影响以及土壤颗粒的再悬浮对大气颗粒物重金属的贡献，结果显示城市土壤灰尘比土壤更能敏感的记录大气重金属的沉降，可作为评估城市环境重金属污染及其健康风险有效指标；土壤颗粒的再悬浮实验表明，土壤与道路灰尘中PM2.5和PM10产率分别为0.1和0.8mg/g。对不同区域与来源的土壤灰尘铅的生物有效性研究显示，降尘铅在人体胃液中的有效性为17.6 - 76.1%，而在小肠系统中有效性则降为1.2 - 21.8%并于钙含量显著相关，表明钙能显著影响小肠对铅的吸收；基于人体有效性的儿童对铅的暴露评估表明，工业区由灰尘摄入铅占了总摄入量的85%，而城区灰尘摄入铅占总摄入量的41%。同时，本项目对城市典型人为污染源铅同位素特征进行系统研究，建立了中国人为污染源铅同位素组成数据库，为示踪中国铅的迁移与全球循环提供了理论依据。