贵州煤中Pb浓度与同位素组成特征

Preliminary Investigation on Concentration and Isotopic Composition of Lead in Coal from Guizhou Province,China

燃煤型Pb已成为我国大气Pb最主要的人为来源,高精度Pb同位素是示踪燃煤Pb排放的强有力工具,但我国煤中Pb同位素的数据报道还较少。本文研究了贵州晚二叠纪不同矿区煤中的Pb浓度和Pb同位素比值。结果表明,样品Pb浓度为2.03~35.6mg/kg,几何均值5.4±3.3mg/kg,低于我国煤中Pb的平均值。煤中^(206)Pb/^(207)Pb为1.1959~1.2774,^(208)Pb/^(206)Pb为1.9500~2.0895,与U/Pb比、全硫、黄铁矿含量有显著相关性,说明煤中U含量和硫化物结合态Pb对Pb同位素组成的影响较大,偏放射性成因。比较分析了贵州省不同Pb来源的同位素组成,初步明确了大方、盘县、水城煤中的Pb主要来源于低温热液流体、玄武岩;毕节、安顺、桐梓煤中的Pb主要来源于陆源玄武岩、低温热液流体,少部分来自海相白云岩;六枝、瓮安煤中的Pb最主要来源于白云岩;晚二叠火山灰可能是兴仁煤的主要来源之一。本研究数据补充了贵州煤中Pb同位素数据的匮乏,并为利用Pb同位素示踪贵州地表环境Pb的来源奠定了基础。

The emission of lead（Pb） during coal combustion is one of the most important anthropogenic sources of atmospheric Pb, and Pb isotopes with high precision provide a powerful tool to trace different sources of Pb in the environment. However, Pb isotopes in coal from China are poorly reported. In this paper, Pb concentrations and isotopic ratios in coals from Upper Permian coal mines, Guizhou Province were investigated. The Pb concentrations in studied samples range from 2.03 mg/kg to 35.58 mg/kg, with a geo-mean of 5.4 ±3.3 mg/kg（n= 9） , lower than the average values of coal from China. The 206pb/207Pb and 208Pb/206Pb isotope ratios range between 1. 195 9-1. 277 4 and 1. 950 0-2. 089 5, respectively, with significant relations with U/Pb, bulk sulfur and pyrite-S. This indicates that Pb isotopes in Guizhou coals have higher radiogenic Pb, controlled by U content and Pb associated with sulfide. On the basis of comparing Pb isotopic composition with different potential sources, we preliminarily suggest that Pb in coal from Dafang, Panxian, and Shuicheng counties mainly come from the low temperature hydrothermal fluid and the basalt ; Pb in coal from Bijie, Anshun, and Tong- zi counties derived from the basalt, the low temperature hydrothermal fluid and few dolomite; the main Pb source of coal from Liuzhi and, Wengan counties is dolomite, and the volcano ash of the Later Permian is one of the major source of Pb in coal from Xingren County. These results fill up the gap of Pb isotopes in coal from Guizhou Province, and provide the basic Pb isotopes data for comparing and tracing the sources of Pb in the different environment of Guizhou, China.