大气沉降对烟叶重金属含量的影响及铅同位素示踪

为探究大气沉降对烟叶中重金属含量的影响，于2015年6~9月以黄淮烟区某地的一般农区、公路两侧和工厂（水泥厂）周边等不同类型农区为研究对象，分析大气重金属沉降通量、表层土壤和烟叶重金属含量及其相关性，并利用Pb同位素示踪探讨了烟叶Pb的重要来源。结果表明:不同类型农区土壤重金属含量和大气重金属沉降通量存在差异，工厂周边大气As、Pb沉降通量分别为7.19 μg·m2·d-1和40.10 μg·m2·d-1，高于一般农区和公路两侧。公路两侧中部叶Pb含量为1.27 mg·kg-1，高于一般农区和工厂周边，而工厂周边上部叶Cr、As、Pb含量分别为0.66 mg·kg-1、0.29 mg·kg-1和2.37 mg·kg-1，高于一般农区和公路两侧。下部叶Cr、Pb含量与其大气沉降通量呈极显著正相关；上部叶Cr含量与表层土壤Cr含量呈极显著正相关，As含量与其沉降通量和表层土壤含量均呈显著正相关。同位素分析结果表明，一般农区的下部叶和上部叶、公路两侧的上部叶和工厂周边的中部叶207Pb/206Pb比值与大气降尘中207Pb/206Pb比值相对接近，与土壤207Pb/206Pb比值则差异相对较大，也显示受大气沉降影响的特征。大气沉降是黄淮烟区烟叶重金属尤其是铅的重要来源之一。 

Effects of atmospheric deposition on heavy metal contents in flue-cured tobacco leaves,and lead isotope tracing

In order to investigate the effects of atmospheric deposition on heavy metal content in flue-cured tobacco leaves, different types of tobacco planting areas in Huanghuai region including countryside, roadside and industrial (cement factory) surroundings were chosen as material from June to September in 2015, and Pb isotope was used to trace Pb element in atmospheric deposition, topsoil and tobacco leaves. Results showed that: 1) Heavy metals contents in atmospheric deposition of different types of tobacco-planting areas in Huanghuai Plain were different. Contents of As and Pb in industrial surroundings were 7.19 μg·m2·d-1 and 40.10 μg·m2·d-1, respectively, much higher than those in countryside and roadside areas. 2) Pb content in cutter leaves of roadside was higher than that of countryside and industrial surrounding areas. Contents of Cr, As and Pb in upper leaves of industrial surroundings were 0.66 mg·kg-1, 0.29 mg·kg-1 and 2.37 mg·kg-1, respectively, much higher than those in countryside and roadside areas. 3) Contents of Cr, Pb in bottom leaves were highly positively correlated with contents of corresponding heavy metal elements in atmospheric deposition. In upper leaves, the concentration of Cr was highly positively correlated with its concentration in soil, while As content was positively correlated with its concentration in atmospheric deposition and soil. The ratio of 207Pb/206Pb in bottom leaves and upper leaves of countryside, upper leaves of roadside, cutter leaves of industrial surroundings was close to that in atmospheric deposition, while the ratio of 207Pb/206Pb in topsoil showed different characteristics. Therefore, atmospheric deposition is one important source of heavy metals, especially lead in tobacco leaves of Huanghuai tobacco growing areas.