Polycyclic aromatic hydrocarbons (PAHs) and alkylated PAHs in the coastal seawater, surface sediment and oyster from Dalian, Northeast China

Highlights

• Parent and alkylated PAHs were determined in marine matrixes from Northeast China.

• Contaminations of PAHs were spread in marine matrixes.

• Compositions of PAHs were different among marine matrixes.

• Ecotoxicological risk of PAHs was evaluated.

• The seawater-sediment partition status was investigated.

Abstract

A total of 46 polycyclic aromatic hydrocarbons (PAHs, 21 parent and 25 alkylated) were determined in seawater, surface sediment and oyster from coastal area of Dalian, North China. The concentration of Σ₄₆PAHs in seawater, sediment, and oyster were 136–621 ng/L, 172–4700 ng/g dry weight (dw) and 60.0–129 ng/g wet weight (ww) in winter, and 65.0–1130 ng/L, 71.1–1090 ng/g dw and 72.8–216 ng/g ww in summer, respectively. High PAH levels were found in industrial area both in winter and summer. Selected PAH levels in sediments were compared with Sediments Quality Guidelines (ERM–ERL, TEL–PEL indexes) for evaluation probable toxic effects on marine organism and the results indicate that surface sediment from all sampling sites have a low to medium ecotoxicological risk. Daily intake of PAHs via oyster as seafood by humans were estimated and the results indicated that oyster intake would not pose a health risk to humans even 30 days after a oil spill accident near by. Water-sediment exchange analysis showed that, both in winter and summer, the fluxes for most high molecular weight PAHs were from seawater to sediment, while for low molecular weight PAHs, an equilibrium was reached between seawater and sediment.

Introduction

Dalian, with an area of 12574 km², lies on the south side of Liaodong Peninsula, Northeast China (E120°58′-E123°31′, N38°43′-N40°10′) (see Fig. SI-1, Supporting information, (SI)), a typical coastal city which is one of the metropolis in China with a population of 600 millions. During the last three decades, the coastal areas of this region have been influenced by a range of socio-economic activities, such as urbanization, industrialization and maritime transport that have resulted in widespread pollution by organic contaminants (Jia et al., 2011, Na et al., 2013, Hong et al., 2014). Besides, a fuel pipeline exploded and caught fire in the southwest of Dayao Bay in Dalian on July 16, 2010 (the location of oil spill place can be found in Fig. SI-1). About 1500 t of crude oil were spilled from the pipeline and a large extent of the shoreline in Dalian was significantly polluted (Liu et al., 2013, Zhang et al., 2013).

Polycyclic aromatic hydrocarbons (PAHs), defined as a group of aromatic hydrocarbons with two or more fused benzene rings, which are one of the most important classes of hydrophobicity organic contaminants. PAHs have proved to be the main components responsible for effects on organisms, because of their carcinogenic, mutagenic and toxic effects (Lotufo and Fleeger, 1997). PAHs in environment are mainly from two sources: petrogenic, composed by PAHs associated with spills of crude and refined oil; pyrogenic, which includes the compounds formed by fossil fuel combustion, waste incineration, biomass burning, and asphalt production. Petrogenic PAHs mainly consist of 2- and 3-rings, as well as alkylated PAHs with one to a few methyl group, while pyrogenic PAHs are often characterized by 4-6 aromatic rings. Alkylated PAHs are classified according to the number of parent rings and the carbon number of alkylated substituents, and they are peculiarly important in the case of crude oil, in which 90% PAH are alkylated (Lian et al., 2009b).

In coastal environments, PAHs come from atmosphere (Esen et al., 2008), urban runoff (McCready et al., 2000), municipal or industrial effluents (Blanchard et al., 2001, Vogelsang et al., 2006), and spillage of fossil fuel (Pettersen et al., 1997). The inputs of PAHs would pose a high risk to the health of humans and wildlife, especially to aquatic organism (Barron et al., 1999). More importantly, alkylated PAHs have been shown to be more toxic (Fallahtafti et al., 2012) and contain higher concentrations than their parent compounds (Hawthorne et al., 2006).

Researches on PAHs in various environmental matrices have been investigated in Dalian, including surface seawater, sediment, soil, and atmosphere (Wan et al., 2006, Wang et al., 2007, Wang et al., 2008, Tian et al., 2009, Wang et al., 2011, Liu et al., 2013). On land, industrial and business/residential areas have been proved to contain higher levels of PAHs both in soil and air than rural and garden areas in Dalian (Wang et al., 2008). While factor analysis model results showed that gasline- and coal-combustion related residential emissions were the primary sources (Wang et.al., 2007). For the aquatic environment, Wang et al. (2011) presented 24 PAH compounds in seawater and sediment, and their water-sediment exchange. Recently, Liu et al. (2013) reported 25 PAH compounds in seawater and sediment sampled from Lingshui Bay to Xiaoyao Bay, Dalian, 50 days after the oil spill accident, and the results indicated that the PAHs in seawater likely originated from the spilt oil and PAHs in sediment were due to historical accumulation. However, these studies just focused on the parent PAHs, and little information of alkylated PAHs have been reported in environmental mediums from Dalian.

The current study investigates both the parent and alkylated PAHs concentrations in seawater, sediment and oyster in the coastal area of Dalian. The objectives of this study are 1) to investigate the pollution levels of parent and alkylated PAHs in multi-matrices, 2) to determine the potential risk caused by these chemicals to human and aquatic organisms, and 3) to analyze water-sediment exchange for each PAH compounds in a coastal marine environment.