乌达煤田尘土汞溯源分析

Traceability analysis of dustfall mercury and topsoil mercury in Wuda Coalfield

本文采用多接收电感耦合等离子体质谱仪(MC-ICPMS)分析了乌达煤田9号火区的不同煤层煤、落尘和地表土汞同位素比值,以探讨煤火区地表汞的可能来源煤层。结果表明,煤、落尘和地表土δ^(202)Hg均值分别为-1.98‰、-1.30‰、-1.26‰,皆具明显偏负特征;地表汞Δ^(199)Hg、Δ^(201)Hg值也显示了偏负异常,如落尘分别为-0.13‰、-0.11‰,地表土分别为-0.11‰、-0.10‰。对比分析汞同位素组成特征,尘土δ^(200)Hg、δ^(202)Hg、Δ^(200)Hg值均介于9号煤层与10号煤层之间,趋于9号煤且偏负,表明9号火区尘土汞主要来源于9号煤层,而非10号煤层。尘土δ^(202)Hg值较9号煤显示明显偏负现象是煤燃烧和加热过程中动力分馏效应及地质层析效应的综合结果。汞同位素可有效判别煤火区地表汞来源煤层,添加汞同位素分析可有利于提高地下煤火监测效果。

The Hg isotopic ratios of coal,dustfall and topsoil from coal fire area No.9 in Wuda coalfield were determined by multiple-collector inductively coupled plasma-mass spectrometry(MC-ICPMS)to explore the possible coal seam source of surface Hg in coal fire areas.The findings were that the δ^(202)Hg of coal,dustfall and topsoil were-1.98‰,-1.30‰and-1.26‰,respectively,which showed a significant mass-dependent fractionation(MDF)characteristics.And there were slightly negative anomaly mass-independent fractionation(MIF)values of surface soil,such as dustfall(Δ^(199)Hg、Δ^(201)Hg:-0.13‰、-0.11‰)and topsoil(Δ^(199)Hg、Δ^(201)Hg:-0.11‰、-0.10‰).A comparative analysis of the characteristics of Hg isotopic showed that the values of surface soil(δ^(200)Hg、δ^(202)Hg、Δ^(200)Hg)were all be-tween the No.9 coal seam and the No.10 seam,and closer to the former,which indicated that the Hg source of surface soil in coalfire area No.9 was coal seam No.9 rather than No.10.Theδ202Hg of dust-fall was more negative than that of coal seam No.9,which was caused not only by the kinetic fractionation effect of burning and heating process but also by the geologic chromatography effect of migration process in crack and hold.Surface sample Hg isotopes characterizations can be used to distinguish coal seam Hg and then identify the burning coal seam.