原油中铅同位素的ICP-MS测定及其在油源鉴别中的应用

Determination of Pb Isotopes in Crude Oil by ICP-MS and Application in Identification of Oil Sources

海洋溢油事件时有发生,探索基于铅同位素特征信息为指标的溢油鉴别技术,在海上溢油鉴别中有着十分重要的意义。本文利用极性较强的二氯甲烷溶解原油样品,分散均匀后在浓硝酸-双氧水氧化消解体系下微波消解,采用电感耦合等离子体质谱法(ICP-MS)测定原油中铅的含量及铅同位素比值(208Pb/206Pb、208Pb/204Pb及208Pb/207Pb),建立了基于铅同位素为特征信息的一种新的油源鉴别辅助技术。实验优化了ICP-MS工作参数,并利用铅标准溶液对同位素积分时间进行优化,提高同位素测定的精密度。结果表明,原油中铅元素测定方法的准确度较高,不确定度<5%,重现性较好,相对标准偏差小于2%(n=3)。该方法应用于测定渤海、南海及国外不同来源的原油样品,分析结果显示不同地区原油中铅元素含量的差异性较大,浓度范围为37.99～1213.00μg/kg。考察了铅同位素比值信息,以208Pb/207Pb与208Pb/206Pb为变量,能够对不同区域原油样品进行分类,我国南海原油样品与其他油源的原油样品差异性明显。本文建立的油源鉴别技术能为油源的初步筛选提供一定的辅助作用。

Oceanic oil spill incidents occur from time to time making it extremely important to establish a new identification method based on Pb isotope information. This method involves dissolving the crude oil in organic solvent （CH2Cl2）, which is a strong polar solvent, and then digesting by microwave with HNO3-H2O2 as the oxidant. The concentration and isotopic compositions of Pb （208Pb/206Pb, 208Pb/204Pb and 208Pb/207Pb） were measured under the optimum conditions of Inductively Coupled Plasma-Mass Spectrometry （ICP-MS）. The accuracy and precision were also studied. The results show that the method is accurate, with a relative error of less than 5%, and a precision with RSD less than 2% （n=3）. The dwell time for different Pb isotopes was also optimized by using Pb standard solution in order to improve the accuracy and get the best integration time. The concentrations of Pb in crude oil from Bohai, Nanhai and other countries was measured, and the concentration range of Pb in all crude oil was 37.99-1213.00 μg/kg demonstrating obvious differences. Meanwhile, the ratios of different Pb isotopic compositions were measured and further processed by cluster analysis by taking 208Pb/207Pb and 208Pb/206Pb as independent variables. It could be seen that the crude oil from different areas can be classified, especially the Nanhai oil. The study could provide some assistance for other identification of oil sources by preliminary screening.