Specificity and ecological risk of heavy metal pollution in Liaoning sewage irrigation district

To address the problems of sewage irrigation, fuzzy recognition model was developed to evaluate sewage irrigated soil environmental quality and improve potential ecological risk index used to assess potential ecological risk of heavy metals. The soil environment quality, heavy metal pollution characteristics and potential ecological risk of Liaoning sewage irrigation district were evaluated by the established model. Results show that the primary contaminant in sewage irrigation districts of Liaoning Province is Cd, whereas Hg, Pb and Ni constitute pervasive pollutants. Correlation analysis indicates that wastewater irrigation and fertilization of farmland are the main sources of heavy metal pollution in Liaoning sewage irrigated soils. Pollution is more serious in the regions irrigated with industrial wastewater than in regions irrigated with river water. The order of heavy metal pollution intensity is: Cd > Pb > Ni > Hg > Cu > Cr > As; and that for potential ecological risk is: Cd > Hg > Pb > Cu > Ni > As > Cr. On the whole, the sewage irrigation district of Liaoning Province is polluted and characterized as a complex pollution situation. The degree of ecological risk is somehow moderate. In the future, soil pollution countermeasures should take into account of pollution characteristics and risk level of every sewage irrigation region.