Assessment of Heavy Metal Pollution and Potential Ecological Risk in Soils of Tianjin Sewage Irrigation Region, North China

Abstract

The aim of the study was to investigate heavy metals concentrations in wheat field soils of Tianjin sewage irrigation region, and evaluate the potential ecological risk of heavy metals pollution. ICP-OES was employed to analyze the heavy metals concentrations in wheat field soils of Tianjin sewage-irrigation region. The grading standard of Tianjin soil environmental quality was used as the assessment foundation for soils and Lars Hakanson’s potential ecological hazards index method was used to evaluate the heavy metals pollution potential ecological risk in soils. The results showed that: Cd concentrations in soils ranged from 0.03 mg•kg-1 to 1.17 mg•kg-1, with an average value of 0.46 mg•kg-1; Zn concentrations in the soils ranged from 62 mg•kg-1 to 307 mg•kg-1, with an average value of 129.08 mg•kg-1. The concentrations of Cd and Zn in the soils exceeded second grade standards of Tianjin soil environment quality, so the soil was polluted. The other heavy metal elements, such as Cu, Pb, Cr and Ni, were all lower than second level of Tianjin soil environment quality standards, meaning that the soil was not contaminated by these heavy metals. The heavy metal concentrations were relatively rich in saline wet fluvo-aquic soil and clayification fluvo-aquic soil. Based on Lars Hakanson’s potential ecological hazards index method, Cd had heavily ecological risk in soils and was the main pollutant, while the other heavy metals had lightly ecological risk. Ecological risk of total heavy metals pollution was moderate. The heavy metals were most likely from wastewater irrigation. The pollutants in the soils came mainly from sewage irrigation. The waste water treatment technology should involve steps to remove heavy metals causing risk to human health.