Assessment of the distribution, sources and potential ecological risk of heavy metals in the dry surface sediment of Aibi Lake in northwest China.

Jilili Abuduwaili,Zhao Yong Zhang,Feng Qing Jiang,Liping Zhu

doi:10.1371/journal.pone.0120001

Abstract

The distribution, sources and potential ecological risk of heavy metals in the sediment of lakes in eastern China and other areas of the world that have undergone rapid economic development have been widely researched by scholars. However, this is not true for heavy metals in the sediment of rump lakes in the arid regions of China and world-wide. Because of this, we chose Aibi Lake to serve as a typical rump lake in an oasis in an arid area in northwest China for our study. Sediment samples were collected from the lake and then the quantities of the heavy metals Pb, Ni, Cd, Cu, Zn, Hg and Cr were measured. Then using a variety of statistical methods, we analyzed the distribution, sources, pollution status and the potential ecological risk of these metals. The results show that: (1) The amounts of the seven heavy metals all fell within the Second Soil National Standard, but the average and maximum values were all higher than the background values of Xinjiang in northwest China. (2) Multivariate statistical analysis determined that the Cd, Pb, Hg and Zn in the sediment were mainly derived from man-sources, and Cu, Ni, and Cr were mainly from the natural geological background. (3) Enrichment factor analysis and the geo-accumulation index evaluation method show that Cd, Hg and Pb in the surface sediment of the Aibi Lake were at low and partial pollution levels, while Zn, Cr, Ni and Cu were at no and low pollution levels. (4) Calculation of the potential ecological hazards index found that, among the seven tested heavy metals, Cd, Hg and Pb were the main potential ecological risk factors, and the contribution of each was 42.6%, 28.6%, and 24.0%, respectively. Cd is the main potential ecological risk factor, followed by Hg and Pb. This work revealed that recent economic development of the Aibi Lake Basin has negatively influenced the accumulation of heavy metals in the sediments of the lake, and, therefore, we should pay increasing attention to this problem and take effective measures to protect the ecology of the Aibi Lake Basin. This work can provide a scientific basis for an early warning of heavy metal pollution and for protection of the environment. Furthermore, it can serve as a reference when creating policies for the economic development in Aibi Lake Basin and environmental protection of rump lakes in arid regions of northwest China and other areas of the world.

Highlights

Heavy metals are concerning pollutants because they are not biodegradable and, once they reach a certain concentration, are quite harmful to the environment [1,2,3]
(2) Multivariate statistical analysis determined that the Cd, Pb, Hg and Zn in the sediment were mainly derived from man-sources, and Cu, Ni, and Cr were mainly from the natural geological background
The maximum and average values of the heavy metals all exceeded the background levels of Xinjiang [40] and the maximum values of Cd, Hg and Cr exceeded the Secondary National Standard of China[44]. This indicates that, due to the agricultural and human activity in townships in the Aibi Lake Basin, there has been a significant trend of heavy metal accumulation in the sediment of Aibi Lake

Summary

Introduction

Heavy metals are concerning pollutants because they are not biodegradable and, once they reach a certain concentration, are quite harmful to the environment [1,2,3]. Human activity plays an important role in heavy metal pollution in lake sediments. With the recent rapid economic development in China, many lakes have become polluted with heavy metals This pollution is to a higher degree in lakes in the eastern parts of the country. Chen and Li, (2007) [13] measured and analyzed the total amount and morphological fraction of ten heavy metals in the sediments of the Chao hu in eastern China and discussed the activity of different forms of heavy metals They found the bioavailability of Cd was much higher than other heavy metals in the sediment and was a result of agricultural pollution. Zeng and Wu, (2007) [14] using geochemical and statistical methods to distinguish between the anthropogenic sources of heavy metals in the sediment of Fuxian Lake in the Yunnan province of southwest China, found that man-made pollution has become a serious environmental problem in this lake

Methods

Results

Discussion

Conclusion