(105b) Pollution and Risk Assessment of Polycyclic Aromatic Hydrocarbons (PAHs) in Typical Sections of Yangtze River and Yellow River, China

State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, P.R. China

Abstract: The Yangtze River and Yellow River are two main rivers in China. In this study, 16 priority polycyclic aromatic hydrocarbons (PAHs) in the sediments of the Yangtze River (Wuhan catchment) and the Yellow River Delta was investigated as many PAHs are prone to associate with solid phase matrix in aquatic systems. The concentrations of total 16 PAHs in sediments in Yangtze River ranged from 22.62~563.90 mg/kg for mainstream and 18.62~8881.78 mg/kg for tributaries, whereas in the Yellow River Delta the total PAH concentrations were found to be ranged from 23.9 to 520.6 mg/kg. The concentrations of the 16 individual PAHs presented varied profiles among different regions. Based on the average effect range low (ERL) quotients method, the ecological risk assessment of PAHs in the two regions were investigated. The results showed that adverse effects would rarely occur in the sediments of the Yellow River Delta, but there were certain potential health risks to drinking water consumers and organism in Yangtze River (Wuhan catchment).

Keyword: Pollution; Risk assessment; Polycyclic aromatic hydrocarbons; Sediment; Yangtze River; Yellow River Delta

1. Introduction

Polycyclic aromatic hydrocarbons (PAHs) are a class of diverse compounds that consist of two or more fused aromatic rings. Due to their carcinogenicity, mutagenicity, and toxicity (IARC, 1987), some of PAHs are of environmental concern and are included in the list of priority pollutants of US EPA and Europe Union.

Due to their low water solubility and high hydrophobicity, once PAHs are introduced into the aquatic environment, they rapidly associate with suspended particles (Chiou et al., 1998) and subsequently deposit in sediments. However, most studies of PAH distribution in sediments have been conducted in the more industrialized areas of the world such as the United States, Canada, Europe, Australia, and Japan (Dickhut et al., 2000; McCready et al., 2000; Headley et al., 2001; De Luca et al., 2005). The Yangtze River and the Yellow River are the two longest rivers in China. The city of Wuhan, located on the middle reaches of Yangtze River, is one of the main industrial centers and economically more developed than many parts of China. The Yellow River Delta, one of the most active regions of land-ocean interaction among the large river deltas in the world, is a newly born wetland.

The objectives of the present work were to determine the concentrations of PAHs in sediments of Yangtze River (Wuhan catchment) and Yellow River Delta in order to assess the effect on PAHs contamination caused by rapid industrialization, urbanization, agriculturalization and fisheries, to provide data for comparison with other rivers and to assess potential ecotoxicological effect.

2. Materials and methods

2.1. Sample collection

The sediment samples were collected using a Van Veen stainless steel grab sampler from 27 sites along Yangtze River and its tributaries, and 30 sites in the Yellow River Delta. During the whole sampling process global position system (GPS) was used to locate the sampling stations. All samples were transferred to laboratory directly after sampling and stored at 4 ¨¬C prior to extraction within 2 days.

2.2. Analytical methods

Each sediment sample was extracted in an ultrasonic bath (KQ-502B, Kunshan Ultrasonic Instruments, China) and concentrated with a rotary evaporator (RV 05 basic, IKA, Germany). After a solvent exchange to methanol, HPLC analysis was used to quantify the PAH values (Niu et al., 2004).

3. Results and discussion

3.1. PAH concentrations in sediments

Concentrations of individual PAHs in different sampling sites were summarized. Most of the 16 PAHs were detected at all sampling sites. The detected concentrations of ¢²PAHs were 22.62~563.90 mg/kg with a mean value of 239.02 mg/kg for Yangtze mainstream, 18.62~8881.78 mg/kg with a mean value of 1212.12 mg/kg for Yangtze tributaries, 23.9~520.6 mg/kg with a mean value of 150.9 mg/kg in the Yellow River Delta. The results indicated that a significant difference among ¢²PAHs in these sampling sites was observed. The PAHs levels at Yangtze tributaries were much higher than those at Yangtze mainstream and the Yellow River Delta. The levels of PAHs in sediments of Yangtze River and Yellow River Delta were not high in comparison with many other aquatic systems.

3.2. Ecological risk assessment

In order to assess whether sediments in this drinking water resource would cause toxic effect, PAHs levels in sediments were compared against effects-based guideline values such as effect range low (ERL), effect range median (ERM), apparent effects threshold values developed by the US Natural Oceanic and Atmospheric Administration (Long et al., 1995). The concentrations of total PAHs and individual PAH in most sediment samples were lower than their respective ERL values. However, two sites in Yangtze tributaries with the total PAH concentration of 8881.78 mg/kg, 4037.30 mg/kg, respectively, showed higher effects-based guideline values than ERL value (4022 mg/kg) but lower than ERM (44792 mg/kg) value. It may be concluded that PAHs may cause mild toxic effect but would not cause immediate biological effects in sedimentary environment in Yangtze River.

4. Conclusions

Analyses of Yangtze River (Wuhan catchment) and Yellow River Delta have provided very useful information for the evaluation of trace PAHs and assessment of their potential risk. The results obtained in this study showed that concentrations of total and individual PAHs in sediment varied significantly among sampling locations. From the ecotoxicological point of view, the concentrations of most PAHs in sediments from the two regions would not cause immediate biological effects in sedimentary environment, but it should be cautioned that occasional adverse effects may occur in the tributaries of the Yangtze River.

Acknowledgements

The research was supported by the National Basic Research Program of China (973 Project, 2006CB403303) and the National Science Foundation for Distinguished Young Scholars (50625926). We gratefully acknowledge project 40701166 supported by National Natural Science Foundation of China.

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