6Raask E. The mode of occurrence and concentration of trace elements in coal[J].FUEL,1985,(01):97-118.
7Swaine D J. Why trace elements are important[J].Fuel Processing Technology,2000,(65-66):21-23.
8Kong S F,Lu B,Ji Y Q. Levels,risk assessment and sources of PM10 fraction heavy metals in four types dust from a coal-based city[J].Microchemical Journal,2011.280-290.
9Zhao H T,Li X Y,Wang X M. Grain size distribution of road-deposited sediment and its contribution to heavy metal pollution in urban runoff in Beijing,China[J].Journal of Hazardous Materials,2010.203-210.
10Madrid F,Barrientos E D,Madrid L. Availability and bioaccessibility of metals in the clay fraction of urban soils of Sevilla[J].Environmental Pollution,2008.605-610.