Migration and Transformation of Heavy Metals in the Soil of the Water-Level Fluctuation Zone in the Three Gorges Reservoir under Simulated Nitrogen Deposition

Liuyi Zhang,Fumo Yang,Yimin Huang,Chuan Fu,Zhengjun Guo,Yang Chen,Tingzhen Li,Kun Fu,Stanislav Frančišković-Bilinski

doi:10.1155/2021/6660661

Abstract

The accumulation of heavy metals (HMs) in the water-level fluctuation zone (WLFZ) of the Three Gorges Reservoir (TGR) area is potentially harmful to the water environment. In order to reveal whether nitrogen (N) deposition is a potential driving factor for the migration and transformation of HMs (Cd, Cr, Cu, Ni, and Pb), a simulated N deposition experiment was performed on the soil in the WFLZ of the TGR. The results showed that the accumulative release amounts of HMs increased with the increase of N deposition. It was found that the Elovich equation, double-constant equation, and parabolic diffusion equation could well describe the release process of Cu, Cd, Cr, and Ni, while the double-constant equation, parabolic diffusion equation, and first-order equation could be applicable for Pb. The exchangeable fractions of HMs increased to varying degrees after the N deposition treatment, wherein Ni was most significant, indicating that N deposition could increase the ecological risk of HM pollution in the TGR area. The results provide insight into the major factors affecting the release of different HMs under N deposition in this vulnerable region ecologically.

Highlights

Introduction e ree GorgesReservoir (TGR) area is located in the middle and upper reaches of the Yangtze River, southwestern China. e the ree Gorges Reservoir (TGR) stores water from October to April and discharges water from May to September, resulting in the water-level fluctuation between 135 m and 145 m, and the formation of a water-level fluctuation zone (WLFZ) with an area of 348.9 km2
A gentle WLFZ was selected at 154 m of water-level elevation in the Tanshao village, Wanzhou District (Figure 1); 12 undisturbed soil samples were collected with clean PVC pipes (15 cm in diameter and 20 cm in height)
We covered both ends of the soil pillar samples with plastic wrap and brought them back to the laboratory for subsequent N addition experiment. e physicochemical properties of soil in WFLZ and concentrations of heavy metals (HMs) are shown in Table 1. e single factor index method was applied to assess the pollution degree of HMs

Summary

Introduction

Introduction e ree GorgesReservoir (TGR) area is located in the middle and upper reaches of the Yangtze River, southwestern China. e TGR stores water from October to April and discharges water from May to September, resulting in the water-level fluctuation between 135 m and 145 m, and the formation of a water-level fluctuation zone (WLFZ) with an area of 348.9 km. Affected by the periodic flooding, the ecological environment of the WLFZ is fragile, and the related environmental problems, e.g., accumulation of heavy metals (HMs), have raised the attention [1, 2]. Since the initial impoundment of the TGR, HMs in the WFLZ soil have shown an upward trend because of the external inputs from agricultural activities and domestic wastes [3]. Factors affecting the activity and mobility of HMs in the soil of WFLZ in the TGR are implicated in two aspects. The local agricultural activities, such as plowing and fertilization in WFLZ during the period of exposure, can accelerate the migration of HMs from WFLZ to the water body of the TGR [4, 5].

Methods

Results

Discussion

Conclusion