Abstract: To evaluate the pollution of harmful elements (Cr, Cu, Zn, As, Cd, Pb and Ni) from road dust in vicinity of the coal mining area near rural area in southwest Guizhou Province, China, 36 dust samples in rural roads were collected. The leaching contents of harmful elements were quantitatively extracted by the method of toxicity characteristic leaching procedure (TCLP). Nemerow comprehensive pollution index (P) and Hkanson index were subsequently calculated to assess the ecological risk. The results showed that the TCLP leaching contents of the total harmful elements were in the range of 1.73%-21.12%. Nemerow comprehensive pollution index (P) results indicated that Pb was at heavy pollution level, As at moderate pollution level, Cr and Cu at mild pollution level, Cd and Zn at the alert level, and Ni at safety level. The potential ecological risk index (E_i) results manifested that Cd achieved strong ecological risk level, As was at the medium level, and other elements belonged to the slight ecological risk level. The total potential ecological risk index (RI) value reached 321.85, which indicated a strong potential of ecological risk. Furthermore, the SBET (simple bioaccessibility extraction test) method was used to evaluate bio-accessibility of harmful elements in the road dust samples, and human exposure risk assessment method adopted by the United States Environmental Protection Agency (USEPA) was used to estimate their health risk after oral intake. The results showed that the average bioavailability of harmful elements in dust were in the range of 7.32%-31.06%. For human health, total carcinogenic risk (TCR) indexes for children and adults were 5.91×10^-5 and 2.15×10^-5, respectively. The potential non-carcinogenic risk (HQ) index of the human body was not significant except for As. The total noncarcinogenic risk (HI) indexes of the harmful elements in road dusts for children and adults were 1.30 and 0.16, respectively, which may pose a potential non-carcinogenic hazard to children. In conclusion, the risk level of Pb, As and Cd in road dusts in rural areas investigated by this study was significant, and should be highly concerned.

Key words: spatial heterogeneity, desert grassland, anthropogenic introduced shrub, soil water