荆州市郊主要农产品中铅来源的同位素示踪研究

Isotopic tracing of pollutant lead sources in main farm produces from suburb Jingzhou

对荆州市郊的农产品（稻米和蔬菜）、水和扬尘样品进行了Ph含量和Ph同位素组成研究。Ph含量分析结果表明，农产品样品具有较大的Ph含量变化范围（8-3469ng／2），虽然其平均值较高（260ng／g），但可食用的粮食和蔬菜未发生普遍的Ph超标现象，仅个别类蔬菜存在一定程度的Ph污染，且受污染的大部分Ph均富集于不可食用的根部或叶部。Ph同位素组成分析结果表明，所有农产品样品的206Pb／。204Pb、207Pb／204Pb和208Pb／204Pb比值较接近，其平均值分别为18280±0079、15630±0020和38451±0084。水和扬尘样品的Ph同位素比值变化范围较大208Pb／（206Pb＋207Pb）_206Pb／207Pb相关关系图显示扬尘位于土壤残渣相与汽车尾气和染料之间，农产品和水则位于由土壤、汽车尾气和染料与煤三者构成的三角形内部，表明扬尘Ph主要来自土壤、汽车尾气和染料，农产品中的Ph来源较为复杂：土壤、汽车尾气和染料、煤、扬尘与水均有贡献，但前三者是最根本的源区。为防止农产品今后逐渐发生Ph超标现象，需将工业ph的排放与污染作为重中之重进行防范。综合对比分析农产品不同部位的Ph含量与Ph同位素比值，结果表明在进行农产品Ph来源同位素示踪研究中可直接采集Ph含量较高的非食用部位，以获得高精度的Ph同位素比值数据。

Analyses on lead content and isotopic composition were carried out on farm produces （rice and vegetable）, water and dust in suburb Jingzhou, Hubei Province, China. The lead contents in farm produce samples vary significantly, ranging from 8 to 3469 ng/g Although the average lead content is high （260 ng/g）, the contents of the edible foodstuff and vegetables have not prevalently exceeded the corresponding standards. Only several vegetable samples show lead pollution, but the pollutant lead mainly reside in the inedible root or leaf. Lead isotopic compositions show 206pb/204Pb, 207pb/204Pb and 206Pb/204Pb ratios of all farm produce samples are close to each other with averages of 18.280±0.079, 15.630±0.020 and 38.451±0.084, respectively. While the water and dust have more variable lead isotopic ratios with 206pb/204Pb, 20Tpb/204Pb and 205Pb/204Pb average ratios of 18.38200.182, 15.65200.037 and 38.628±0.152, respectively. In a 205Pb/（206pb＋20Tpb） w＇. 206pb/207Tpb diagram, dust samples lie between soil residues and automobile exhausts and dyestuff, farm produces and water scatter along a triangle composed of the soil, automobile exhaust and dyestuff and the coal. This distribution suggests the dust lead mainly results from the soil, automobile exhaust and dyestuff, the water lead mainly from the soil, automobile exhaust and dyestuff and the coal. Compared with the dust and water, the lead sources of farm produces are more complex with the contribution of soil, automobile exhaust and dyestuff, dust, water and coal, while as a whole, the farm produce lead directly or indirectly derives from the soil, automobile exhaust and dyestuff and the coal which are the essential lead sources. To prevent the gradual lead pollution on farm produce, it＇s the most important to keep away the emission and pollution of the industrial lead. The contrastive analysis of lead contents and isotopic ratios of different parts of the farm produce suggests we can sample the inedible part containing high lead content to obtain high-precision lead isotopic ratios to trace lead sources of farm produces.