Relationships between Heavy Metal Concentrations in Roadside Topsoil and Distance to Road Edge Based on Field Observations in the Qinghai-Tibet Plateau, China

Xuedong Yan,Chen Zeng,Man Zhang,Fan Zhang,Dan Gao,Wang Xiang

doi:10.3390/ijerph10030762

Abstract

This study investigated the spatial distribution of copper (Cu), zinc (Zn), cadmium (Cd), lead (Pb), chromium (Cr), cobalt (Co), nickel (Ni) and arsenic (As) in roadside topsoil in the Qinghai-Tibet Plateau and evaluated the potential environmental risks of these roadside heavy metals due to traffic emissions. A total of 120 topsoil samples were collected along five road segments in the Qinghai-Tibet Plateau. The nonlinear regression method was used to formulize the relationship between the metal concentrations in roadside soils and roadside distance. The Hakanson potential ecological risk index method was applied to assess the degrees of heavy metal contaminations. The regression results showed that both of the heavy metals’ concentrations and their ecological risk indices decreased exponentially with the increase of roadside distance. The large R square values of the regression models indicate that the exponential regression method can suitably describe the relationship between heavy metal accumulation and roadside distance. For the entire study region, there was a moderate level of potential ecological risk within a 10 m roadside distance. However, Cd was the only prominent heavy metal which posed potential hazard to the local soil ecosystem. Overall, the rank of risk contribution to the local environments among the eight heavy metals was Cd > As > Ni > Pb > Cu > Co > Zn > Cr. Considering that Cd is a more hazardous heavy metal than other elements for public health, the local government should pay special attention to this traffic-related environmental issue.

Highlights

Heavy metals are typical road traffic source contaminants in the local ecological environments and threaten public heath [1]
We investigated the contents of eight heavy metals (Cu, Zn, Cd, Pb, Cr, Co, Ni and As) in roadside soils along five major road segments across the Qinghai-Tibet Plateau
Because the sampling sites are off residential, agricultural and industrial activities, the extra heavy metals accumulations in roadside soils are almost purely due to traffic activities, which is helpful to assess the degree of traffic pollution and clarify the spatial relationships between the heavy metals’

Summary

Introduction

Heavy metals are typical road traffic source contaminants in the local ecological environments and threaten public heath [1]. If there are farmlands within the scope that the contaminants can reach, they may enter the food chain as a result of their uptake by edible plants [4], causing serious health risks. Because of their toxicity (especially for Cd and Pb), persistence and non-degradability characteristics, it is of great importance to monitor the heavy metals concentrations in roadside environments. Heavy metal levels in atmospheric particulates, roadside dust and soil along a major urban highway.

Methods

Results

Conclusion