The Occurrence Characteristics Of PAHs In Coal And Mine Drainage In Xuzhou Area

Polycyclic aromatic hydrocarbons(PAHs) are widely spread. Endowed with a long life span, PAHs are carcinogenic, teratogenic and mutagenic to humans and animals. Produced during the process of dissolution of coals and wastes by groundwater, PAHs may enter the groundwater system or surface water bodies by mining water, through which pose potential threat to water environment. So the research of the occurrence characteristics of PAHs in coal and water in mining area is of great importance.In this paper, we take Xuzhou mining area as the example. Measuring 16 priority control types of PAHs in samples by the rules provided by USEPA, studying the types, contents, distribution, sources,ecological risk of PAHs and the releasing rules of PAHs under certain closed condition in abandoned mine, we come to conclusions as following:(1) The total concentration of PAHs in eight coal samples of Xuzhou ranges from 3.96ug/g to 36.23ug/g, while 12 to 16 types are detected. The total concentration of PAHs in gangue samples is 2.9ug/g, less than it in coal samples. Three-ring, four-ring and five-ring PAHs are chief components of coal samples from Kongzhuang Mine, Quantai Mine and Zhangshuanglou Mine. Coal quality, such as carbon content, hydrogen to carbon ratio and oxygen to carbon ratio and volatile substances influences PAHs occurrence. The content of two-ring and three-ring PAHs in coal samples of Q ishan Mine and Q uantai Mine is higher, while the content of BaP in samples of Q ishan Mine and Zhangshuanglou Mine is higher. As a result, they are of greater danger to the environment.(2) PAHs in mining water are mainly consisted of two-ring and three-ring PAHs. While four-ring, five-ring and six-ring PAHs are much less. Only the content of BaP in Quantai Mine water exceeds Ⅳclass groundwater quality standards(DZ/T 0290-2015). The content of both collapse wetlands water samples and gangue percolation water in Zhangshuanglou Mine exceeds the surface water environmental quality standard(GB3838-2002). According to former research and ratio method, PAHs of mine water come mainly from meteoric water and surface water supply. Coal and coal gangue also leach PAHs. At the same time, it may also be connected to waste emission by people. The ecological risk of PAHs in Q uantai mine water is believed to be much greater than the other mines.(3) PAHs of downhole mud are mainly constituted by high molecular weight PAHs. The mean content of PAHs ranking: Quantai Mine> Q ishan Mine> Xinhe Mine, all of which exceed EPA standards of sediments. Humic acid and organic materials benefit the absorption of PAHs in the mud. The total content of PAHs in resid ue samples from Kongzhuang Mine is 40.3ug/g, which is 55 times than that of water samples. So we should pay close attention to PAHs contamination in mud and residue.(4) We carried out leaching simulation experiments of PAHs in a closed environment with deionized water and mine water for 5 months. The result show that in both deionized water and mine water, PAHs in coal sample s decreased significantly. While in the leached solution, PAHs increased rapidly. Low rings PAHs are easier to release than high rings PAHs. At the same time, the amount of NaP and BaP grew. The content of PAHs trends to increase in mine water under closed condition, so we need to pay attention to the pollution risk of PAHs in mine water of closed mines to groundwater.