【作者】 占茉莉；

【导师】 姚卫蓉；

【作者基本信息】 江南大学 ， 营养与食品卫生学， 2008， 硕士

【摘要】 基于铅同位素比值在地球化学过程中一般不受所在系统的温度、压力、pH、Eh和生物等作用而发生分馏,只与源区初始铅含量及形成时间有关这一特征,铅同位素指纹特征被广泛用做示踪环境铅污染的来源。为了研究铅同位素技术对追溯高暴露地区的农产品铅污染的来源和途径的可行性,研究不同铅污染源对农产品的贡献率,本研究利用了可调多接收热电离子质谱仪(MAT-261)分析浙江西湖龙井茶及其生长环境的土壤、大气降尘、冶炼矿石、工业燃煤铅同位素丰度值,利用ICP-MS和ICP-AES检测样品中的Pb、Cd、Cr、Fe、Mn的含量,并分析汽车尾气、土壤、加工过程对茶叶铅含量影响,研究茶叶铅同位素丰度值与种植土壤、工业燃煤、冶炼矿石等同位素之间的关系,借鉴化学质量平衡受体模型的基本理论,建立铅污染源对茶叶铅贡献率的数学模型。结果表明:不同铅污染来源铅同位素丰度值存在差异,并具有各自指纹特征;加工过程对西湖龙井影响不显著。距居民区的距离越近,茶叶铅含量越高。土壤铅含量与茶叶铅含量相关性不显著。老叶铅含量显著高于嫩叶铅含量。不同产地龙井茶206Pb/207Pb和208Pb/207Pb值差异不明显。西湖龙井茶铅同位素丰度值位于汽车尾气铅与工业燃煤铅同位素丰度值的交汇处,与大气降尘铅同位素特征值重合较多,远离土壤及工业冶金的铅同位素特征值。说明西湖龙井茶叶铅来源于汽车尾气和燃煤排放,主要污染途径为大气降尘,而不是土壤。说明利用铅同位素技术对茶叶中铅的污染源进行追溯是可行的方法。利用化学质量平衡受体模型理论可以推算污染源的贡献率。同时本文探索性的研究茶叶的产地溯源,目的是研究利用近红外光谱分析技术判别茶叶产地来源的可行性。在中国名茶主产区浙江省采集龙井绿茶样品28份,粉碎,过筛,平衡水分。利用近红外光谱分析技术,对茶叶样品的近红外光谱进行主成分分析、聚类分析。结果表明,浙江省龙井绿茶近红外原始光谱谱图差异较大,而不同产地龙井绿茶原始光谱间差异不甚明显。对原始光谱数学处理后对其进行主成份分析,发现在主成分空间内第一主成分得分绝大部分为正,继而对不同产地的样品进行主成分分析,西湖龙井有比较明显的主成分特征,区别于浙江龙井;西湖龙井主成份空间分布的离散度大于浙江各市县龙井的变异。对龙井绿茶样品进行聚类分析,得出相同产地的绿茶样品可聚为一类。初步研究结果表明:近红外光谱可以区分浙江的龙井绿茶,而且还可以准确的、快速的判别“西湖龙井”与“浙江龙井”。因此,应用近红外光谱分析技术可准确、快速、低廉地追溯茶叶的产地。更多还原

【Abstract】 Lead isotope for environmental pollution tracing has been intensively applied mainly based on the geochemical characteristics. Also, the geochemical action of Pb was not controlled by temperature, pressure, pH and Eh values, even the biological effect. And Pb isotope fractionation could not happen. In order to investigate the feasibility of isotope technique in trace back the sources and the way of lead pollution of agricultural products in high exposure area, and the contribution rate of various lead pollution sources. We made some explorative research on the lead isotope ratios of Xihu Longjing Tea, soil, atmospheric dust, ore and industrial firing coal in Zhejiang province by MS detection(MAT-261); and the contents of Pb, Cd, Cr, Fe, Mn in tea and soil samples by ICP-MS and ICP-AES detection. Analyze of Influencing Factors on lead content of tea leaf. Investigate the relationship of the tea, soil, industrial firing coal, ores, with lead isotope ratios. And build a contribution rate model of lead pollution source to lead contamination in tea, using the chemical mass balance theory as reference.The results showed that lead isotope ratios of pollution sources were differences and had their respective characteristic. While the ratios of 206Pb/207Pb and 208Pb/207Pb of tea was insignificant in different producing area. Processing had little effect on it. The closer to the downtown, the higher content of Lead presented in tea leaf. The lead content of tea did not correlate significantly with that of soil. And growing leaf were higher than tender leaf. The lead isotope ratios of Xihu LongjingTea located in a overlay area consisting of atmospheric dust, automobile exhaust and industrial coal. Especially the ratios of atmospheric dust were quite the same. It showed that the most important source of tea lead pollution were vehicle tail gas and coal-fired emissions. The pollution way of tea was atmospheric dust not soil. At last we draw the conclusion by the practical study: the method based on lead isotope ratio to trace back the lead pollution in this paper was feasible. The application of chemical mass balance model method for pollution source identification and apportionment in tea was acceptable.Besides, the study on determination of the geographical origin of tea based on FT-IR spectroscopy analysis and pattern recognition Technique aimed to investigate the feasibility of tracing the geographical origin of tea with FT-IR spectroscopy. 28 dried Longjing tea samples from main tea-producing areas of Zhejiang province in China were crushed and sieved.Based on NIR spectroscopy of the pre-processing tea, samples were subjected to principal component analysis (PCA), cluster analysis (CA) ,discriminate analysis (DA). The results showed that obvious spectral differences could be observed of Longjing tea. The difference of Longjing tea from different geographical origins was relatively unconspicuous,whereas recognizable. The near-infrared reflectance spectra of tea are studied by the principal component analysis after mathematical treatment. It was indicated by the results that principle component score of Longjing tea is positive . The analysis on principal component of two different space distribution types expressed the characteristics of the tea samples. However, via a principle component analysis (PCA) disposal of Longjing tea, The characteristics can be defined as the particular features which distinguish Xihu Longjing tea from Zhejiang Longjing tea. And coefficient of variation of characteristic parameters was analyzed to determine dispersion in spatial distribution of Xihu Longjing tea was larger than that of the other cities and counties in Zhejiang province.According to the Euclidean distance of NIR spectroscopy, geographical origin can be identified by cluster analysis. So applying FT-NIR fingerprint spectroscopy to trace geographical origin of tea is accurate, rapid and low cost.更多还原