Distribution and Source Apportionment of Polycyclic Aromatic Hydrocarbons (PAHs) in Forest Soils from Urban to Rural Areas in the Pearl River Delta of Southern China

Yihua Xiao,Yuanwen Kuang,Fuchun Tong,Bufeng Chen

doi:10.3390/ijerph110302642

Abstract

The upper layer of forest soils (0–20 cm depth) were collected from urban, suburban, and rural areas in the Pearl River Delta of Southern China to estimate the distribution and the possible sources of polycyclic aromatic hydrocarbons (PAHs). Total concentrations of PAHs in the forest soils decreased significantly along the urban–suburban–rural gradient, indicating the influence of anthropogenic emissions on the PAH distribution in forest soils. High and low molecular weight PAHs dominated in the urban and rural forest soils, respectively, implying the difference in emission sources between the areas. The values of PAH isomeric diagnostic ratios indicated that forest soil PAHs were mainly originated from traffic emissions, mixed sources and coal/wood combustion in the urban, suburban and rural areas, respectively. Principal component analysis revealed that traffic emissions, coal burning and residential biomass combustion were the three primary contributors to forest soil PAHs in the Pearl River Delta. Long range transportation of PAHs via atmosphere from urban area might also impact the PAHs distribution in the forest soils of rural area.

Highlights

Polycyclic aromatic hydrocarbons (PAHs) are a group of organic contaminants which exist ubiquitously in the environment
Compared to suburban residential areas in the Pearl River Delta (PRD), such as Guangzhou (160.00~1,300.00 ng·g−1), Dongguan (128.00~357.00 ng·g−1), and Shenzhen (230.00~3,700.00 ng·g−1) [31,32], and agricultural soils in suburban areas around Guangzhou (422.00 ± 194.35 ng·g−1), PAH concentrations in suburban forest soils were much lower. This comparison implied that urban forests could play important role in scavenging PAHs from the atmospheric deposition, which was consistent with the findings by Tian et al
The larger fraction of LMW-PAHs in the rural forest soils in this study indicated that PAHs might mainly stem from low- or moderate-temperature combustion processes

Summary

Introduction

Polycyclic aromatic hydrocarbons (PAHs) are a group of organic contaminants which exist ubiquitously in the environment. Environmental PAHs come from two sources: natural processes (e.g., forest fires, volcanic activity, etc.) contributing to the background values of PAHs, and anthropogenic activities (e.g., incomplete combustion of fossil fuels, coke production, industrial processes, etc.) contributing to the contamination levels of PAHs [1,2,3,4]. Owing to their carcinogenic, mutagenic, and teratogenic effects on organisms, 16 PAHs were specified as priority control target pollutants by the United States Environmental Protection Agency (EPA) [5,6]. It has been well documented that most anthropogenic PAHs will be restricted to the top layer of the soils [11]

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Conclusion