中国煤中砷的含量分布、赋存状态、富集及环境意义

Arsenic in Chinese Coals:Its Abundance, Distribution, Modes of Occurrence, Enrichment Processes,and Environmental Significance

砷是煤中有害微量元素之一,在煤加工利用过程中,砷会以各种形式释放出来,进入环境。本文在全面分析现有资料和文献的基础上,结合作者对中国煤中砷的研究成果,分析了中国煤中砷的含量与分布、赋存状态、富集因素以及环境意义。通过研究和分析可知,中国煤中砷的平均值约为5μg/g,但在不同地区、不同时代以及不同类型的煤中有较大的差异,除中国西南地区含量异常高外,一般含量均在10μg/g以内;煤中砷的赋存状态多种多样,主要以无机态的硫化物结合为主,并常与黄铁矿等矿物伴生,也存在有机态结合的砷;中国煤中砷的来源和富集主要是以陆源母岩、成煤植物、沉积环境和构造裂隙—热液作用等为主的多种因素综合控制的结果;在煤燃烧过程中,煤中的砷释放出来,并对长期生活在燃煤地区的环境和人体产生影响。本文还提出今后煤中砷研究的主要方向,以为煤中砷的研究提供参考资料。

Arsenic is one of the hazardous elements in coal. During coal processing and combustion, arsenic is released into the environment. Based on data available and research achievements, the authors reviewed in this paper abundance, distribution, modes of occurrence, geological processes for arsenic enrichment in Chinese coals as well as its environmental significance. The arsenic abundances are quite different in coals from different coal basins or of different geological ages and grades. The average arsenic content in Chinese coals is estimated to be 5 μg/g, excluding the Late Permian coals in southwestern China which have anomalously high arsenic content. Arsenic may occur in several modes in coals. It is most commonly contained in mineral matter, mainly pyrite and other sulfide minerals. Part of arsenic in coals is associated with the organic matter. The sources of arsenic in coal include parental plant materials, detrital minerals, basinal fluids, and hydrothermal fluids. In southwestern China, some Late Permian coals are anomalously enriched in arsenic because of the effect of hydrothermal fluids. Arsenic in these coals is mainly present in the form of arsenate (AsO_4~ 4+ ), and partly existent in pyrite. During coal combustion, most arsenic ends in the formation of fly ash, with a small part released into the environment. As a significant portion of arsenic is in the mineral matter, it may be removed with the mineral matter during coal preparation.