To identify the concentrations and sources of heavy metals, and to assess soil environmental quality, 63 soil samples were collected in Yibin City, Sichuan Province, China. Mean concentrations of As, Pb, Zn, and Cu were 10.55, 61.23, 138.88 and 56.35 mg/kg, respectively. As concentrations were comparable to background values, while Pb, Zn, and Cu concentrations were higher than their corresponding background values. Industrial areas exhibited the highest concentrations of As, Pb, Zn, and Cu, while the lowest concentrations occurred in parks. Statistical analysis was performed and two cluster groups of metals were identified with Pb, Zn, and Cu in one group and As in the other. Spatial distribution maps indicated that Pb, Zn, and Cu were mainly controlled by anthropogenic activities, whereas As could be mainly accounted for by soil parent materials. Pollution index values of As, Pb, Zn, and Cu varied in the range of 0.24-1.93, 0.66-7.24, 0.42-4.19, and 0.62-5.25, with mean values of 0.86, 1.98, 1.61, and 1.78, respectively. The integrated pollution index （IPI） values of these metals varied from 0.82 to 3.54, with a mean of 1.6 and more than 90% of soil samples were moderately or highly contaminated with heavy metals. The spatial distribution of IPI showed that newer urban areas displayed relatively lower heavy metal contamination in comparison with older urban areas.
The temporal distribution of polycyclic aromatic hydrocarbons （PAHs） was investigated in a sediment core from Lake Erhai in Southwest China using gas-chromatography/mass spectrometry （GC/MS） method. The total organic carbon （TOC） normalized total PAHs concentrations （sum of US Environmental Protection Agency proposed 16 priority PAHs） ranged from 31.9 to 269 ixg/g dry weight （dw）, and were characterized by a slowly increasing stage in the deeper sediments and a sharp increasing stage in the upper sediments. The PAHs in the sediments were dominated by low molecular weight （LMW） PAHs, suggesting that the primary source of PAHs was low- and moderate temperature combustion processes. However, both the significant increase in high molecular weight （HMW） PAHs in the upper sediments and the vertical profile of diagnostic ratios pointed out a change in the sources of PAHs from low-temperature combustion to high-temperature combustion. The ecotoxicological assessment based on consensus-based sediment quality guidelines implied that potential adverse biological impacts were possible for benzo（ghi）perylenelene and most LMW PAHs. In addition, the total BaP equivalent quotient of seven carcinogenic polycyclic aromatic hydrocarbons （BaA, CHr, BbF, BkF, BaP, DBA and INP） was 106.1 rig/g, according to the toxic equivalency factors. Although there was no great biological impact associated with the HMW PAils, great attention should be paid to these PAH components based on their rapid increase in the upper sediments.
