Occurrence Modes of Arsenic in Coal: A Case Study from the Hanshuiquan Coal Mine, Santanghu Coalfield, Xinjiang Province, China  
Bo Zhu  
Key Laboratory of Coalbed Methane Resources & Reservoir Formation Process, Ministry of Education, Xuzhou 221108, China School of Resources and Geosciences, China University of Mining & Technology, Xuzhou 221116, China  
[PERSON]  
Key Laboratory of Coalbed Methane Resources & Reservoir Formation Process, Ministry of Education, Xuzhou 221008, China School of Resources and Geosciences, China University of Mining & Technology, Xuzhou 221116, China  
Jijun Tian  
College of Geology and Mining Engineering, Xinjiang University, Urumqi 830046, China  
[PERSON]  
Key Laboratory of Coalbed Methane Resources & Reservoir Formation Process, Ministry of Education, Xuzhou 221108, China School of Resources and Geosciences, China University of Mining & Technology, Xuzhou 221116, China  
[PERSON]  
Key Laboratory of Coalbed Methane Resources & Reservoir Formation Process, Ministry of Education, Xuzhou 221108, China School of Resources and Geosciences, China University of Mining & Technology, Xuzhou 221116, China
the content of elements in coal could guarantee the national energy strategic needs, and (2) revealing the occurrence modes, migration, and transformation mechanisms of elements in coal and coal by-products may help solve the environmental problems in the process of coal utilization [1; 2; 3; 4; 5; 6; 7]. Twenty-four elements (Sb, As, Ba, Be, B, Cd, Cl, Cr, Co, Cu, F, Pb, Hg, Mn, Ni, Mo, P, Se, Tl, Th, Sn, V, U, and Zn) are defined as hazardous elements. According to their negative influence on the environment, these hazardous elements can be classified into four types, with As, Cd, Cr, Hg, and Se thought to cause the most severe damage to the environment [8]. During the exploitation and utilization of coal, there are large amounts of waste and exhaust gases produced, and these hazardous materials could threaten human health through the air, soil, drinking water, and the food chain. Examples include the endemic coal-fired arsenic poisoning of Guizhou Province in southwest China [9; 10], and the poor skeletal growth of children influenced by the discharged As and Pd from the nearby coal-fired power plant in Former Czechoslovakia [11]. In addition, it has also been reported that pollution of the residential water wells in Virginia (USA) is disposal of coal slurry using underground injection [12]. Previous studies have proven that the migration and release of elements from coal during its exploitation, storage, and utilization have a certain influence on the environment, and the occurrence state of various elements determines how difficult it is for them to migrate and be released [13; 14]. The poisonousness of As(III) is 60 times that of As(V) [15], and organic-state arsenic is difficult to extracted using physical methods, but arsenic gas can be released during burning [16]. Furthermore, the As in sulfate, carbonates, sulfide, and part-organic matter can be separated easily, while the arsenic in silicate minerals (such as the clay minerals) is quite stable in the surface environment [17]. Therefore, research on the occurrence states of arsenic could have a positive impact on coal exploitation and environmental protection. There have been several large-scale studies on the occurrence states of arsenic in coal. It was found that arsenic could be enriched in pyrite in coal at the beginning of the twentieth century [18], and it can also be divided into two types, the arsenopyrite and pyrite form states [19]. There are some arsenic minerals inclined to accrete with sulfides, such as realgar, orpiment and arsenopyrite. These sulfides mainly contain the elements of Cu, Pb and Zn, such as chalcopyrite, sphalerite and pyrite [20; 21]. It has been found that arsenic cannot be enriched as an independent mineral in Guizhou, and that there is a positive relationship between the S and As contents, and that pyrite is the dominant carrier for arsenic [22].