Geochemical characteristics and microbial populations of Neogene brown coal from Zhaotong Basin, China
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ORIGINAL ARTICLE
Geochemical characteristics and microbial populations of Neogene brown coal from Zhaotong Basin, China Aikuan Wang • Yong Qin • Fengjuan Lan
Received: 18 February 2011 / Accepted: 9 July 2012 / Published online: 22 July 2012 Ó Springer-Verlag 2012
Abstract For the first time in China, a preliminary survey of geochemical characteristics and microbial populations of Neogene brown coal from Zhaotong Basin in Yunnan province, China was conducted to provide a basis for an understanding of the generation of biogenic coal-bed methane in this basin. Coals in this region consist of soft brown coal with lower maturity and good bioactivity, as determined by coal petrologic measurements. Soluble organic matter in coal exhibits the characteristics of unsaturated humic hydrocarbon source rock. Organics in coal were generally associated with higher plants and lower grade aquatic organisms. The bacterial community was dominated by fermentation bacteria, and sulfate-reducing bacteria were relatively rare. Keywords Brown coal Geochemical characteristic Microbial population Zhaotong Basin
Introduction Coal-bed methane may be categorized as either thermogenic or biogenic in nature. Biogenic coal-bed methane may be further classified as primary- or secondary-biogenic coal-bed methane. Primary biogenic CBM is generated early in the coal formation process with organic matter in A. Wang (&) Y. Qin F. Lan School of Resources and Geoscience, China University of Mining and Technology, Xuzhou 221116, Jiangsu, China e-mail: [email protected] Y. Qin Key Laboratory of CBM Resources and Pooling Process, Ministry of Education of China, Xuzhou 221116, Jiangsu, China
very low rank coal (Ro \ 0.3 %). Secondary biogenic CBM is formed in coal of low to medium rank seams (0.3–1.5 %, Ro) due to microbial activity. Bacteria can be brought into a coal-bed through the water flowing through permeable coal (Scott et al. 1994). Theoretically, biogenic CBM would be mass-produced as long as the environmental and nutrient conditions needed for methanogenesis are met. As a result, the theoretical research and enhanced exploration of biogenic coal-bed methane cause more and more attention in and abroad (Smith and Pallasser 1996; Li and Zhang 1998; Kotarba 2001; Qin 2003; Zhang et al. 2004; Zhu et al. 2007; Steve et al. 2008; Dariusz et al. 2008; Tao et al. 2005). The Zhaotong Basin is located in southeastern Yunnan Province, China, and is the main known brown coal resource region in the country. The basin covers an area of 230 km2 and the major strata are of Tertiary and Neogene age (Wang 2010). The Neogene coal in the basin is all softbrown coal. The humic is the majority in coal maceral composition. The maturity of organic material in coal is low and the coal is considered to be formed in situ in low moor. The Neogene brown coal in the basin contains significant amounts of biogenic CBM, and some geological researchers in China have started studying the geological background and gas exploration in this region (He et al. 2002; Li et a
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