Hazardous trace elements in Jurassic coal from Ordos basin, China

摘要

Dongsheng Coalfield lies in the northern part of Ordos basin and near its margin. The main coal-bearing measure in this coalfield is Yan'an formation deposited in continental environment of middle -lower Jurassic. The coal from this coal-bearing measure are caking coal or long flame coal with 5 percent-9 percent average ash, less than 0.7 percent average total sulfur. Therefore these coals have good quality. In this paper, the hazardous elements such as Cu, Pb, Zn, Cd, Hg, Ni, V, and Mn in these coals were determined using atomic absorption spectroscopy (AAS), atomic fluorescence spectroscopy (AFS) and polarography and visible light spectrophotometric methods after coal samples were treated with chemical method. The data for these trace elements in coals show that average concentrations of Cu, Pb, Zn, Ni, Cr, Cd, Hg and V in Jurassic coal of Dongsheng Coalfield are very low, and is 0.11, 0.03, 0.23, 0.34, 0.11, 0.02, 0.01, 0.11 times of that in whole Chinese coal. However, the content of Mn is 2.34 times higher than that of whole Chinese coal. The pyrite and other sulfur-bearing minerals are very small, main minerals are clay minerals (with average 4.87 percent SiO_2 and 0.61 percent Al_2O_3). Hence, distribution characteristics of mineral in coals lead to low concentrations of above hazardous trace elements, especially the chalcophile elements.