区域大气沉降对土壤-作物系统镉铅循环过程的影响及其机制

At present, many researches have been focused on the sources and formation mechanism of heavy metals in soils and crops. Despite public concerns, quantitative knowledge of heavy metals in agricultural soils from different sources especially from different anthropogenic sources remains scarce. Concerning heavy metals in crops, soil is generally recognized as the major source. Heavy metals in soils and crops from atmospheric deposition are often neglected. In this project, we plan to take the Yangtze River watershed of Nanjing in the Yangtze River Delta region of China as a case study area. Taking the soil-crop-atmospheric system as a comprehensive and dynamic system to study the cyclic process and mechanism of Cd and Pb in the whole agroecosystem. A combination of systematic sampling and analysing of different environmental medium over time, spatial and geostatistical analysis, field micro-plot experiment, Cd and Pb stable isotopic tracer technique, and model simulation will be used to elucidate the effects of atmospheric deposition on cyclic process and mechanism of Cd and Pb in regional soil-crop system. Through this study, the enrichment characteristic, spatial-temporal evolution, sources, environmental input fluxes of Cd and Pb in regional soil-crop system will be illuminated as well. In addition, contribution rates of heavy metals in crops from the soils and atmospheric deposition will also be quantified. Furthermore, the forecast and early warning of Cd and Pb accumulated trend in regional soil-crop system over a long period will also be simulated based on IDMM (Intermediate Dynamic Model for Metals) model. This work will provide baseline information to develop effective policies and standards to control and reduce heavy metal inputs and long-term accumulation in agricultural soils as well as to provide the theoretical basis and technical support for safe agricultural production and sustainable agricultural production and management.

目前，关于土壤和作物中重金属来源及其形成机制的研究较多，而针对大气沉降对土壤-作物系统重金属富集的影响缺乏足够重视。本项目拟以长江经济带的南京沿江流域土壤-作物-大气系统Cd和Pb为研究对象，将土壤-作物-大气系统作为一个整体，从农田生态系统Cd和Pb多介质循环过程的动态观点出发，通过区域不同时段多介质采样与分析、空间和地统计分析、大田微区试验、稳定同位素示踪、模型模拟等技术手段，在区域尺度和田间自然条件下系统研究大气沉降对土壤-作物系统Cd和Pb循环过程的影响及其机制，阐明区域Cd和Pb多介质富集的时空演变规律、来源及环境输入通量，揭示大气沉降对土壤-作物系统Cd和Pb富集的影响及其贡献，并对区域土壤Cd和Pb长期累积趋势进行预测预警。研究成果对区域农田重金属污染防控及农业安全生产具有重要现实指导意义，同时对指导区域农田重金属污染评价、风险预警及农田环境质量综合管理具有重要参考价值。

近年来，强烈人为活动，如工业生产、快速城镇化、高强度农业利用、矿山开采与冶炼等已经导致我国部分区域农田土壤重金属污染，局部甚至出现土壤重金属异常现象，严重威胁区域土壤环境质量和农产品安全。目前，关于土壤和作物中重金属来源及其形成机制的研究较多，对于作物中重金属的来源，一直倾向于认为土壤是其最主要的来源，而针对大气沉降对土壤-作物系统重金属富集的影响缺乏足够重视。本项目以长江下游沿江地区等典型强烈人为活动区域土壤-作物-大气系统Cd和Pb等重金属为研究对象，将土壤-作物-大气系统作为一个整体，通过典型区域多介质调查采样与分析、空间和地统计分析、大田微区试验、稳定同位素示踪、模型模拟等技术手段，在区域尺度和田间自然条件下研究大气沉降对土壤-作物系统Cd和Pb等重金属循环过程的影响及其机制。通过项目研究，明确了长江经济带农田土壤Cd和Pb等重金属的空间分布及其主要影响因素，阐明了长江下游沿江地区等典型区域农田土壤Cd和Pb等重金属多介质富集特征、时空演变规律、来源及环境输入通量，揭示了大气沉降对区域土壤-作物系统Cd和Pb等重金属富集的影响及其相对贡献，并对典型区域农田土壤重金属长期累积趋势进行了模拟与预测。依托本项目研究，在国内外重要学术期刊发表论文20篇，其中SCI期刊论文12篇、EI期刊论文2篇，中文核心期刊论文6篇，授权发明专利1项、实用新型专利1项、软件著作权3项，培养研究生5名。项目研究成果可为区域农田土壤重金属溯源研究提供重要技术手段，为我国区域农田重金属污染防控及风险环境管理提供重要理论依据。