城市大气重金属干湿沉降对土壤-蔬菜系统的污染效应

Dry and wet deposition of heavy metals in urban areas has a major impact on vegetable quality and the health risk of local residents. We choose Shanghai city as the representative of the study area and the elements Pb, Hg, Cd, Cr, As, Zn and Cu as the main study objects. By comprehensively employing systimatic field investigation, settling chamber-potted vegetable simulation, Pb isotope labeling technology and in situ dynamic testing of vegetable exposed to atmospheric deposition, we mainly study the contributions of two exposure pathways of dry and wet deposition, foliar dust and root absorption pathways, to the total amount of heavy metals in vegetables; reveal the contributions of bioavailable heavy metals, as well as the migration and transformation behavior and their mechanisms of settled heavy metals in soil; build the contribution model of atmospheric deposition to heavy metals accumulated in vegetables based on bioavailability; verify the validity of this model and the simple binary Pb isotope model in estimating the contributions of accumulated heavy metals in vegetables through the two pathways; discuss the effects of atmospheric deposition on edible vegetables in field planting conditions; and clarify the human health risk of heavy metals through ingestion of vegetables. Based on these efforts, we aim to improve the development of biogeochemical theory of heavy metals in the gas-soil-organism interface.

城市大气重金属干湿沉降对市郊蔬菜质量安全和当地居民身体健康有重要影响。本研究选取上海市作为代表区域，以Pb、Hg、Cd、Cr、As、Zn和Cu等为主要研究对象，通过大田试验区系统调查、沉降室降水/降尘-盆栽蔬菜模拟试验、Pb同位素标记示踪技术和蔬菜累积大田微区暴露试验的综合运用，系统研究城市大气降水降尘通过叶面降尘和根系吸收途径对蔬菜累积重金属的贡献，揭示生物可利用态重金属的贡献率以及干湿沉降重金属在土壤中的迁移转化行为与机制，基于重金属的生物有效性构建蔬菜累积重金属的大气沉降来源贡献模型，验证这一模型和简单二元Pb同位素模型在估算蔬菜重金属来源贡献方面的有效性，探讨大田种植条件下蔬菜可食部分重金属的大气沉降来源贡献及其影响因素，阐明通过摄食蔬菜途径带来的重金属人体健康风险，以期进一步丰富气-土-生界面重金属生物地球化学循环理论。

城市大气重金属干湿沉降对市郊蔬菜质量安全和当地居民身体健康有重要影响。本研究选取上海市作为代表区域，以Pb、Hg、Cd、Cr、As、Zn和Cu为主要研究对象，通过大田试验区系统调查、沉降室降水/降尘和盆栽蔬菜模拟试验、Pb同位素标记示踪技术和蔬菜累积大田微区暴露试验的综合运用，系统研究了上海市郊工业区附近菜地土壤、灰尘和蔬菜中重金属的污染特征及其健康风险，分析了大气干湿沉降中重金属的沉降通量变化及其对蔬菜累积重金属的影响，探讨了干湿沉降重金属对土壤-蔬菜系统的污染效应，构建了蔬菜重金属来源贡献模型，阐明了上海市郊土壤-蔬菜系统中重金属来源及其贡献。研究结果发现，在城市工业区如钢铁厂、热电厂和固体垃圾焚烧厂附近，土壤、灰尘和蔬菜中往往会积累相对较高的重金属，对人体的潜在健康风险已经存在。Cu、Zn和Cd主要通过根系吸收途径在蔬菜体内发生富集，Pb、Hg尤其是Pb可通过叶片吸收途径进入蔬菜体内。大气干湿沉降重金属可以通过叶片吸收途径进入蔬菜体内，但大多数干湿沉降重金属通过沉降到土壤中后再被蔬菜吸收。相关研究不仅丰富了气-土-生重金属生物地球化学循环理论，而且为我国城市食品安全防范和预警提供了科学依据。