Assessment of Heavy Metal Contamination in the Surrounding Soils and Surface Sediments in Xiawangang River, Qingshuitang District

Min Jiang,Ming Chen,Qian Yu,Lifeng Liu,Jiachao Zhang,Langping Hu,Chang Zhang,Guangming Zeng,Lunhui Lu,Xiaoying Ma,Karl Rockne

doi:10.1371/journal.pone.0071176

Abstract

Xiawanggang River region is considered to be one of the most polluted areas in China due to its huge amount discharge of pollutants and accumulation for years. As it is one branch of Xiang River and the area downstream is Changsha city, the capital of Hunan Province, the ecological niche of Xiawangang River is very important. The pollution treatment in this area was emphasized in the Twelfth Five-Year Plan of Chinese government for Xiang River Water Environmental Pollution Control. In order to assess the heavy metal pollution and provide the base information in this region for The Twelfth Five-Year Plan, contents and fractions of four heavy metals (Cd, Cu, Pb and Zn) covering both sediments and soils were analyzed to study their contamination state. Three different indexes were applied to assess the pollution extent. The results showed this area was severely polluted by the four heavy metals, and the total concentrations exceeded the Chinese environmental quality standard for soil, grade III, especially for Cd. Moreover, Cd, rated as being in high risk, had a high mobility as its great contents of exchangeable and carbonates fractions in spite of its relative low content. Regression analysis revealed clay could well explain the regression equation for Cd, Cu and Zn while pH and sand could significantly interpret the regression equation for Pb. Moreover, there was a significant correlation between Non-residual fraction and Igeo for all the four metals. Correlation analysis showed four metals maybe had similar pollution sources.

Highlights

Environmental contamination by heavy metals is a serious and worldwide problem that accompany with the rapid industrialization and urbanization in many countries
The heavy metal water samples were collected in bottles by acidification in the field with concentrated HNO3.The bottles were kept in ice cake on the way to the laboratory, and stored in fridge at 4uC before analysis
The concentration of Cu varied from 0.31 mg/L to 0.82 mg/L, which was less than the reference value (GB 8978– 1996), while the other metals were found to be in the range of Cd 0.03–0.32, Pb 0.64–1.21 and Zn 2.79–5.69, all on mg/L unit

Summary

Introduction

Environmental contamination by heavy metals is a serious and worldwide problem that accompany with the rapid industrialization and urbanization in many countries. It is widely recognized that the measurement of total metal concentration in sediments/soils is not sufficient to provide information about the exact dimension of pollution by heavy metals [9]. The total concentration of sulphate in Xiawangang River varied from 37.1 mg/L to 436.2 mg/L. This was fairly high and could be attributed to the use of sulfuric acid by the surrounding factories. Phosphate in Xiawangang River was observed from 0.06 mg/L to 0.18 mg/L, which was similar with Xiang River It was in the scope of Integrated Wastewater Discharge Standard (GB 8978–1996). The concentration of Cu varied from 0.31 mg/L to 0.82 mg/L, which was less than the reference value (GB 8978– 1996), while the other metals were found to be in the range of Cd 0.03–0.32, Pb 0.64–1.21 and Zn 2.79–5.69, all on mg/L unit

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