Distribution Characteristics Of PAHs In Coal With Different Coal Ranks

Polycyclic aromatic hydrocarbons(PAHs)are organic pollutants with carcinogenicity,teratogenicity and gene mutation.Coal is one of the main sources of PAHs in the environment,and coal will release PAHs to the environment during mining,transportation,and utilization.Raw coal is the basis of coal production and utilization,so the study of PAHs in raw coal is crucial.In this paper,the raw coals of different metamorphic degrees in Heidaigou Coal Mine,Malan Coal Mine,Tunlan Coal Mine,Ximing Coal Mine,Sijiazhuang Coal Mine and Gushuyuan Coal Mine are taken as the research objects(vitrinite reflectances R₀,max are 0.60%,1.21%,1.47%,1.84%,2.70%,3.30%).The Soxhlet extraction method was used to extract PAHs in coal samples,the rotary evaporator and column chromatography were used to concentrate and purify the extracting solution,and high-performance liquid chromatography(HPLC)was used to measure the contents of PAHs in the samples,to study the distribution of PAHs in coal with different coal ranks,C contents,H/C molar ratio and O/C molar ratio;analyze the change of PAHs toxicity in raw coal with different coal ranks;and study the raw coal source of PAHs in the environment by useing Ant/(Ant+Phe),Flua/(Flua+Pyr),Ba A/(Ba A+Chr)and Total index.The purpose of the study is to provide information for the formation and release control of PAHs and source judgment during coal utilization,and to provide a strong basis for reducing PAHs pollution in the environment and retrieving the source of pollution.The results show that:(1)The contents of 3-6 ring PAHs in coal increase first and then decrease with the increase of coal ranks,the contents of 2ring PAHs keep decreasing,and the total contents of PAHs in coal increase first and then decrease with the increase of coal ranks(R₀,max=0.60%-3.30%).(3)The contents of PAHs in coal increase gradually with the increase of C_daf%in coal(C_daf%=76.25%-84.49%),and then the contents of PAHs decrease gradually with the increase of C_daf%in coal(C_daf%=84.49%-93.71%).The contents of PAHs experienced the process of decreasing,increasing and decreasing with the increase of H/C mole ratio(the mole ratio of H/C range from0.63 to 0.91).The contents of PAHs in coal increase first and then decrease with the increase of O/C molar ratio(the mole ratio of O/C range from 0.026 to0.121).The toxicity of PAHs in coal increases first and then decreases with the increase of coal ranks.(7)The ratios of Ant/(Ant+Phe)are 0.073-0.085,the proportions of Flua/(Flua+Pyr)are 0.237-0.340,the ratios of Ba A/(Ba A+Chr)are 0.064-0.178,and the range of total index in samples are 2.286-3.738,all of which are within the range of non-combustion source.