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Distribution, sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in surface sediments from the Nantong Coast, China
MPB-08033; No of Pages 6 Marine Pollution Bulletin xxx (2016) xxx–xxx
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Distribution, sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in surface sediments from the Nantong Coast, China Na Liu a,b,c,1, Xian Li b,1, Daolai Zhang c,⁎, Qiang Liu d, Lihui Xiang d, Ke Liu a, Dongyun Yan a, Yue Li a a
College of Environmental Science and Engineering, Qingdao University, Qingdao 266071, China Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China Key Laboratory of Coastal Wetland Biogeosciences, China Geological Survey, Qingdao 266071, China d Eastern China Geological & Mining Organization for Non-ferrous Metals in Jiangsu Province, Nanjing 210007, China b c
a r t i c l e
i n f o
Article history: Received 26 July 2016 Received in revised form 2 September 2016 Accepted 10 September 2016 Available online xxxx Keywords: Polycyclic aromatic hydrocarbons Sediment Source Ecological risk assessment Nantong Coast
a b s t r a c t The distribution, sources, and ecological risk assessment of 16 polycyclic aromatic hydrocarbons (PAHs) in surface sediments from the Nantong coast in China were investigated. The results indicated that the total concentrations of the 16 PAHs in the surface sediments from the study area ranged from 1.4 to 87.1 ng g−1 dw (mean value 19.9 ng g−1 dw), which were generally low compared to the adjacent offshore area and other coastal zones around the world. The selected PAH ratios and the principal components analysis for each site showed that petroleum combustion and petrogenic pollution (mainly caused by petroleum spills) were the dominant PAHs sources in the surface sediments of the coast. The ecological risk assessment indicated that most of the individual PAHs had few negative effects in this area. © 2016 Elsevier Ltd. All rights reserved.
The recent rapid development of industry, the economy, and urban expansion along the world's coastlines has meant that polycyclic aromatic hydrocarbons (PAHs) (Table 1) have attracted the attention of environmental chemists, toxicologists, and regulatory agencies over the past few decades. PAHs are ubiquitous, volatile organic pollutants in the environment that are composed of two or more fused aromatic rings (Bouloubassi et al., 2012; Bragato et al., 2012; Callén et al., 2013; Carver et al., 1986; Lea-Langton et al., 2013; Readman et al., 2002). They have low aqueous solubilities and high octanol/water partition coefficients, which mean that PAHs entering the ocean tend to associate with particulate material and accumulate in sediments (Lindgren et al., 2014; Naes et al., 1995). PAHs in marine sediments have attracted considerable attention around the world because of their negative effects on marine aquatic systems and humans (Chen and Chen, 2011; Deng, 2013; Guo et al., 2012; Culotta et al., 2006; Guzzella et al., 2005; Soliman et al., 2014). The coastal zones are where the land and marine ecosystems mix and they receive substantial quantities of PAHs, which may pose an ecological risk to coastal ecosystems. It has been suggested that the coastal sediments in China are heavily polluted by PAHs, especially on coasts where there is extensive anthropogenic activity (Li et al., 2016). In addition, many studies have reported that large concentrations of PAHs and the associated high ecological risks have been observed in coastal sediments (Lee et al., ⁎ Corresponding author. E-mail addresses: [email protected] (N. Liu), [email protected] (D. Zhang). 1 Co-first authors.
2005; Wang et al., 2012; Zhang et al., 2016). Therefore, concerns about PAH pollution, ecological risk, and PAH pollution sources in coastal marine sediments of China have increased recently (Huang et al., 2011; Yuan et al., 2014; Zhang et al., 2016). Nantong is regarded as the “Golden Coast” and “Golden Waterway” and is located at the southernmost tip of Jiangsu's coastal zone and is to the north of the Yangtze River. It was one of the earliest open-up cities and the city's economy has developed rapidly, but this has simultaneously brought about environmental deterioration. The Nantong coast provided large numbers of areas for land use. The quality of Nantong coast has been affected by increased human activity, accelerated industrialization, and the rapid expansion of the local economy, which has exposed it to an increasing risk of pollution from toxic chemicals. In addition, rapid economic growth on the coast around Nantong has raised concerns about significant pollution of aquatic environments, especially of sediments that act as a natural repository of organic pollutants. However, only a few studies about the characteristics of the polychlorinated naphthalenes and polybrominated diphenyl ethers present in sediments located around the Nantong coast have been conducted (Wang et al., 2016; Zhang et al., 2015). Most of these studies focused on areas south of Nantong, such as the surface sediments of the Yangtze River and the Chongming wetland (Wang et al., 2012; Yu et al., 2016). This means that there is a lack of data describing the sediment PAH concentrations on the Nantong coast. Therefore, we investigated the distribution, source, and ecological risk posed by PAHs in the surface sediments of the Nantong coast. The results of this study will serve as a
http://dx.doi.org/10.1016/j.marpolbul.2016.09.020 0025-326X/© 2016 Elsevier Ltd. All rights reserved.
Please cite this article as: Liu, N., et al., Distribution, sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in surface sediments from the Nantong Co..., Marine Pollution Bulletin (2016), http://dx.doi.org/10.1016/j.marpolbul.2016.09.020
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N. Liu et al. / Marine Pollution Bulletin xxx (2016) xxx–xxx
Table 1 Descriptive of 16 PAHs. Species
Abbreviations
Number of rings
Naphthalene Acenaphthylene Acenaphthene Fluorene Phenanthrene Anthracene Fluoranthene Pyrene Benzo(a)anthracene Chrysene Benzo(b)fluoranthene Benzo(k)fluoranthene Benzo(a)pyrene Dibenzo(a,h)anthracene Indeno(1,2,3-cd)pyrene Benzo(g,h,i)perylene
NAP ACY ACE FLO PHE ANT FLA PYR B[a]A CHR B[b]F B[k]F B[a]P DB[a,h]A I[1,2,3-cd]P B[g,h,i]P
2 3 3 3 3 3 4 4 4 4 5 5 5 5 6 6
baseline to assess future anthropogenic effects and will be valuable to local governments. The sampling stations were arranged from the Nantong coast in Jiangsu Province, China. The surface sediments (depth 0–5 cm) were collected from the sample sites using a Smith–Mcintyre grab sampler, the position of the sites were showed in Fig.1 (121.42–122.23 E, 31.71–32.30 N). The sampler of each sample was washed by the seawater in the same sample site. All of the sediments were wrapped in solvent-rinsed aluminum foil, transported to the laboratory stored at −20 °C until further analysis. The samples were freeze-dried and ground into a fine powder (b0.25 mm) for PAHs analysis. The extraction of PAHs was carried out according to the method reported by Nicola et al. (2005). A mixture of perdeuterated internal standards ([d-10]phenanthrene, [d-10]pyrene, [d-12]chrysene, [d-12]perylene, and [d-12]benzo[g,h,i] perylene) was added to the sieved samples (10 g). Each sample was subsequently mixed with an equal quantity of anhydrous sodium sulfate in 60 mL of
dichloromethane/acetone (1:1, v/v) solution for 20 min and then sonicated three times. The extract was concentrated, solvent-exchanged with n-hexane, and further reduced to approximately 1 mL under gentle nitrogen flow. The resulting extract was loaded into a 1:2 alumina/silica gel glass column for fractionation and cleanup. The first fraction, which contained aliphatic hydrocarbons, was eluted with 15 mL n-hexane. The second, which contained PAHs, was collected after elution with 5 mL nhexane and 70 mL of methylene chloride/n-hexane (30:70) solution. The purified extracts were concentrated to a volume of 1 mL under a stream of nitrogen. Known quantities of an internal standard were added to the sample prior to instrumental analysis. Grain size analysis for the surface sediments were performed with a laser granulometer (Malvern Mastersizer 2000) after the organic matter digestion with 10% H2O2 and the dispersion with sodium hexametaphosphate. Grain size parameters were calculated following the formula of Folk (1957). The PAH concentrations were measured by gas chromatography using an HP 5890 GC equipped with an HP-5MS capillary column (30 m, 0.25 mm i.d., 0.25 μm film thickness) coupled to an HP 5975 mass spectrometer with a mass-selective detector. The carrier gas, helium, was introduced at a flow rate of 1.0 mL min−1. The oven temperature was initially set at 70 °C, then increased by 20 °C min− 1 to 280 °C, which was held for 24 min. Quantitation was conducted by using the primary ions for each compound. Two to three secondary ions were used for qualitative confirmation. The glassware and sodium sulfate were solvent-rinsed and heated for 4 h at 450 °C prior to use. For quality assurance and control, a spiked blank, a procedural blank, matrix spikes, and a duplicate sample were analyzed in the same way as the test sample for each batch of 10 samples. No quantifiable targets were detected in these blanks. Analysis of a reagent blank demonstrated that the analytical system and glassware were free of contamination. The recovery for the spiked blanks was 75.0%–120.0%. The results reported in this work were not corrected for recoveries and the relative standard deviation for parallel samples was b15% (n = 3).
Fig. 1. Locations of the studied areas of Nantong coast of China.
Please cite this article as: Liu, N., et al., Distribution, sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in surface sediments from the Nantong Co..., Marine Pollution Bulletin (2016), http://dx.doi.org/10.1016/j.marpolbul.2016.09.020
N. Liu et al. / Marine Pollution Bulletin xxx (2016) xxx–xxx
The ANT/(ANT + PHE), FLA/(FLA + PYR), B[a]A/(B[a]A + CHR), and I[1,2,3-cd]P/(I[1,2,3-cd]P + B[g,h,i]P) ratios were calculated to determine the source of the PAHs. These sources can be categorized into different groups (Yunker et al., 2002): ANT/(ANT + PHE) b 0.1 and FLA/ (FLA + PYR) b 0.4: petroleum pollution; 0.1 b ANT/(ANT + PHE) b 0.5 and 0.4 b FLA/(FLA + PYR) b 0.5: petroleum combustion; ANT/ (ANT + PHE) N 0.5 and 0.1 b FLA/(FLA + PYR) b 0.5: grass, wood, and charcoal combustion; B[a]A/(B[a]A + CHR) b 0.2: petroleum pollution; B[a]A/(B[a]A + CHR) N 0.35: pyrolytic processes; I[1,2,3-cd]P/(I[1,2,3cd]P + B[g,h,i]P) b 0.2: petroleum pollution; 0.2 b I[1,2,3-cd]P/(I[1,2,3cd]P + B[g,h,i]P) b 0.5: petroleum combustion; and I[1,2,3-cd]P/ (I[1,2,3-cd]P + B[g,h,i]P) N 0.5: grass, wood, and charcoal combustion. Principal component analysis (PCA) with multivariate linear regression (MLR) was conducted to identify the source contributions of the different PAHs and was performed using IBM SPSS Statistics v20 for Windows. The spatial distributions of PAHs in the surface sediments from the Nantong coast are shown in Fig. 2. The total concentrations of 16 US EPA priority PAHs ranged from 1.4 to 87.1 ng g− 1 dw with a mean value of 19.9 ng g−1 dw. The highest concentration was obtained from site NT25 (87.1 ng g−1 dw) followed by NT24 (57.8 ng g−1 dw), whereas the lowest concentration was measured at site NT52 (1.4 ng g−1 dw) where only eight PAH compounds were detected. Anthropogenic use of the terrestrial area has continually increased, which means that the higher concentrations of PAHs detected inshore might be due to human activities. On the coast at Nantong, there are two types of ocean currents: the forward ocean current of the East Sea and the rotary ocean current of the Yellow Sea (Yao, 2013). The crests of these two waves converge and their energies aggregate. This results in the active movement of sediments that come from the Yangtze River estuary through coastal erosion of the ancient Yangtze River Delta and from ocean sediments. They have caused sand ridges to form in Nantong's offshore shallow water and they are significant sediment sources. Furthermore, it is possible that the PAHs in the Yangtze River might be carried into the study area. ACYs were not found in the study area, ACEs were found in 18.9% of the sediment samples, ANTs were present in 39.6% of the samples, FLAs were found at 50.9% of the sites, and the detection rates for PYR, FLO, PHE, and NAP were 84.9%, 86.8%, 64.2%, and 98.1%, respectively, B[a]A, CHR, B[b]F, B[k]F, B[a]P, DB[a,h]A, I[1,2,3-cd]P, and B[g,h,i]P were all present in the sediments. The results showed that NAP account for over 30% of total concentrations of the 16 PAHs at the sites, whereas ACY and ANT only account for about 1.0%. The mean value order for the 16 PAHs was NAP N PHE N DB[a,h]A N I[1,2,3-cd]P N CHR N B[a]P N B[b]F N PYR N FLO N FLA N B[k]F N B[g,h,i]P N B[a] A N ANT N ACE N ACY. The PAHs in the surface sediments from the Nantong coast and its surrounding area were compared to the PAH concentrations in surface
Fig. 2. Total PAHs in the surface sediments from the Nantong coast, China.
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Table 2 Comparison of PAH concentrations (ng g−1 dw) in surface sediments from different coastal zones around the world and their adjacent areas.
Nantong, China Chongming Island, China The intertidal zone of Bohai Bay, China Yangtze estuary, China Kaohsiung, Taiwan Haizhou Bay, China South Yellow Sea Guan River, China Gulf of Mexico, North America Chao Phraya River Estuary, Thailand a
Mean (ng g−1 dw)
∑PAHs (ng g−1 dw)
References
19.9 –a 140 ± 84.1
1.4–87.1 38.7–136.2 –
This study Wang et al. (2012) Huang et al. (2011)
449.8 – – 825 ± 716 132.7 305
76.9–2936.8 88–729 72.5–805.2 61–3601 91–218 52–403
Wang et al. (2012) Lee et al. (2005) Zhang et al. (2013) Deng (2013) He et al. (2014) Wang et al. (2011)
2290
6–8399
Ruchaya et al. (2006)
not reported in the reference.
sediments from different coastal zones around the world and their adjacent areas. Table 2 shows that the total concentrations of the 16 PAHs obtained from the Nantong coast (1.4 to 87.1 ng g−1 dw; mean value 19.9 ng g−1 dw) were less than the values reported for adjacent areas, such as Chongming Island, China (38.7 to 136.2 ng g− 1 dw; mean value 737.0 ng g−1) (Wang et al., 2012), the Yangtze River (76.9 to 2936.8 ng g−1 dw; mean value 449.8 ng g−1 dw) (Wan et al., 2012), and the South Yellow Sea (61 to 3601 g−1 dw; mean value 825 ± 716 ng g−1 dw) (Deng, 2013). They were also much lower than the intertidal zone in Bohai Bay, China (mean value, 140 ± 84 ng g−1 dw) (Huang et al., 2011), Haizhou Bay (mean value 140 ± 84.1 ng g− 1 dw) (Zhang et al., 2013), the Guanhe River (91–218 ng g−1 dw; mean value 132.7 ng g− 1 dw) (He et al., 2014), Kaohsiung, Taiwan (88– 728 ng g−1 dw) (Lee et al., 2005), Chao Phraya River Estuary, Thailand (6–8399 ng g− 1 dw; mean value 2290 ng g− 1 dw) (Ruchaya et al., 2006), and the Gulf of Mexico, North America (52–403 ng g− 1 dw; mean value 305 ng g−1 dw) (Wang et al., 2011). The mean grain size (Mz) of the samples in the Nantong coast varies between 2.0Φ and 7.4Φ, with a mean value of 4.3Φ, indicating that the sediments are mainly composed of coarse silt-sized components, which meant that the properties of the sediment in this area were considerably affected by sediment texture. The PAHs adsorbed in sand sediments are easily washed out to adjacent seas and coastal zones. So PAH compounds were much lower in the Nantong coast area. The composition patterns of the PAHs ranged by ring size in the Nantong coast surface sediments are shown in Fig. 3. The PAH compositional patterns in the sediments were mainly 2-ring (NAP) and 5-ring (B[b]F, B[k]F, B[a]P, and DB[a,h]A) compounds. The 2- and 5-ring PAHs accounted for 30.1% and 25.3%, respectively, of the total PAHs, whereas the 3-ring (PHE and ANT), 4-ring (FLA, PYR, B[a]A, and CHR), and 6-ring (B[g,h,i]P and I[1,2,3-cd]P) compounds accounted for 17.4%, 17.4%, and 9.7%, respectively. The PAH composition followed a gradient of 2-ring N5-ring N 3-ring N4-ring N 6-ring. This was different from its adjacent sea, the Yellow Sea (3-ring and 4-ring PAHs were more abundant), and the Guanhe River estuary in Jiangsu Province (3-ring and 5-ring PAHs were more abundant), China. This means that the PAH concentrations in the sediments are influenced by a number of factors, including total organic carbon content, mean sediment grain size, clay content, currents, and pollution source (Zhang et al., 2016). PAHs are distributed in environments throughout the world and are generated by many different pathways. Therefore, it is important to identify PAH sources if their distribution is to be controlled and responsibility for remedial action is to be properly allocated. Various sources produce different compounds and lead to different concentrations in the environment. Studies have shown that isomeric ratios and PCA of PAH concentration can be used to identify the different sources (Budzinski et al., 1997; Magi et al., 2002; Sicre et al., 1987; Soclo et al.,
Please cite this article as: Liu, N., et al., Distribution, sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in surface sediments from the Nantong Co..., Marine Pollution Bulletin (2016), http://dx.doi.org/10.1016/j.marpolbul.2016.09.020
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N. Liu et al. / Marine Pollution Bulletin xxx (2016) xxx–xxx
100% 90% 80% 70% 6-ring
60%
5-ring
50%
4-ring 40%
3-ring
30%
2-ring
20% 10%
NT1 NT2 NT3 NT4 NT5 NT6 NT7 NT8 NT9 NT10 NT11 NT12 NT13 NT14 NT15 NT16 NT17 NT18 NT19 NT20 NT21 NT22 NT23 NT24 NT25 NT26 NT27 NT28 NT29 NT30 NT31 NT32 NT33 NT34 NT35 NT36 NT37 NT38 NT39 NT40 NT41 NT42 NT43 NT44 NT45 NT46 NT47 NT48 NT49 NT50 NT51 NT52 NT53
0%
Fig. 3. PAH composition patterns by ring size in surface sediments from the Nantong coast, China.
2000; Nilsen et al., 2015). Therefore, we used these methods to further assess the sources of the PAHs in surface sediments from the Nantong coast. The ANT/(ANT + PHE), FLA/(FLA + PYR), B[a]A/(B[a]A + CHR), and I[1,2,3-cd]P/(I[1,2,3-cd]P + B[g,h,i]P) ratios have been shown to be useful in the identification of PAH sources. Fig. 4 shows the ratios and sources of PAHs in surface sediments from the Nantong coast. Petroleum usually contains compounds that are more thermodynamically stable, such as NAP, FLA, PHE, and CHR. FLA and PYR are usually the most abundant compounds from pyrolytic PAH sources, such as combustion of petroleum, grass, wood, and coal (Magi et al., 2002; Sicre et al., 1987; Zhang et al., 2004). The ANT/(ANT + PHE) and FLA/ (FLA + PYR) ratios from NT8, NT11, NT29, and NT31 suggested that petroleum was the pollution source at these sites. NT14, NT18, NT26, NT40, and NT51 were affected by pyrolytic PAH sources, and the NT1 and NT4 site results indicated that both combustion and petroleum were the principle sources. The PAHs at sites NT3, NT15, NT17, NT19, and NT24 originated from a mixture of petroleum and coal combustion sources, while the PAHs at NT10, NT16, and NT25 were dominated by
petroleum pollution and petroleum combustion. The B[a]A/ (B[a]A + CHR) and I[1,2,3-cd]P/(I[1,2,3-cd]P + B[g,h,i]P) ratios indicated that NT6 and NT18 were dominated by petroleum pollution and combustion. The pollution at 14 of the sites (NT11, NT15, NT20, NT23, NT24, NT27, NT28, NT34, NT36, NT39, NT41, NT42, NT43, and NT48) was mainly caused by petroleum spills, and the PAHs in the sediments from NT3, NT5, and NT9 originated from mixed petroleum pollution and combustion. The PAHs in N60% of the sites, including NT1, NT2, NT7, NT8, NT10, NT12, NT13, NT16, NT17, NT19, NT21, NT22, NT25, NT26, NT29, NT30, NT31, NT32, NT33, NT35, NT37, NT38, NT40, NT44, NT45, NT46, NT47, NT49, NT50, NT51, NT52, and NT53 were produced by petroleum combustion, whereas the PAHs at NT4 and NT14 were probably produced by grass, wood, and charcoal combustion. PCA was used to further examine the relationships between PAH composition and the possible chemical sources for each factor. Loading plots of the two principal components are shown in Fig. 5. Most of the variance (85.1%) in the normalized dataset can be explained by the first two factors.
Fig. 4. Ratios and sources of PAHs in surface sediments from the Nantong coast, China.
Please cite this article as: Liu, N., et al., Distribution, sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in surface sediments from the Nantong Co..., Marine Pollution Bulletin (2016), http://dx.doi.org/10.1016/j.marpolbul.2016.09.020
N. Liu et al. / Marine Pollution Bulletin xxx (2016) xxx–xxx
Fig. 5. Loading plots for the two principal components.
The first principal component (PC1) of all the individual PAHs accounted for 65.3% of the variance in the dataset. High positive loadings for NAP, FLA, PYR, B[a]A, CHR, B[b]F, B[k]F, B[a]P, DB[a,h]A, B[g,h,i]P, and I[1,2,3-cd]P were observed for this factor. B[b]F, B[k]F, B[a]P, I[1,2,3-cd]P, and DB[a,h]A belong to the high molecular weight PAHs with 4–6-rings, and B[g,h,i]P has been identified as a tracer for automobile emissions because it has been found to be enriched along with B[a]P in traffic tunnel emissions (Harrison et al., 1996; Larsen and Baker, 2003). B[k]F and its isomers, such as B[b]F and B[a]P, are dominant compounds in particulate samples from roadside air (Boonyatumanond et al., 2007). Therefore, vehicular traffic pollution was a major contributor to PAH contamination in PC1. In contrast, PC2, which accounted for 19.7% of total variance, was positively dominated by low-molecularweight PAHs, such as ACE, ANT, FLO, and PHE. PAHs with low molecular weights are abundant in petrogenic sources, which are mainly caused by petroleum spills (Dobbins et al., 2006; Marr et al., 1999), whereas those with high molecular weights are abundant in compounds from pyrolytic sources.
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The isomeric ratios and PCA led to the similar conclusion: petroleum combustion sources and petrogenic pollution (mainly caused by petroleum spills) were dominant in the surface sediments from the Nantong coast. Pyrolytic PAHs may come from the diesel engine emissions produced by shipping. Nantong is located at the intersection of the coastal economic zone and the Yangtze River Economic Zone, and it borders Shanghai, which is the international metropolis of China. The geographical position of Nantong has promoted local and rapid economic development in this city. In addition, industrial emissions, heavy traffic, and coal heating could also have increased the PAH loadings through atmospheric deposition and freshwater run off. Sediment quality guidelines (SQGs) are based on the Biological Effects Database for Sediments. They are commonly used in sediment assessments of marine environments (Long et al., 2006). SQGs provide two target values: the effects range low (ERL) and effects range median (ERM) values, which are established using the 10th and 50th percentiles, respectively, in a database of increasing concentrations associated with adverse biological effects. Table 3 shows the toxicity guidelines for 12 PAHs and classifies the sites into three different ranges, which are defined by the ERL and ERM values. The concentration of individual PAHs in the surface sediments of the Nantong coast were all below the ERL, which indicated that the PAHs in the sediments do not have any adverse effect on organisms. However, with the exception of ACY, all 16 PAHs were detected in the surficial sediments samples. Therefore, more attention should be paid to protecting the Nantong coast, although the probability of negative effects from the PAH compounds is low. Additionally, there were no reported sediment quality guideline values for B[k]F, B[a]P, B[g,h,i]P, and I[1,2,3-cd]P, but they were found at all the sites. The total concentration of 16 US EPA priority PAHs ranged from 1.4 to 87.1 ng g−1 dw with a mean value of 19.9 ng g−1 dw in the Nantong coast area, but they had a relatively low PAH contamination value compared to the adjacent areas and other coastal zones around the world. The PAHs in the surface sediments of the Nantong coast mainly originated from petrogenic pollution (mainly caused by petroleum spills) and petroleum combustion. The rapid economic development of the city might result in industrial emissions, heavy traffic, diesel engine exhausts from shipping, and coal powered heating, which would raise PAH loadings through atmospheric deposition and freshwater run off. The ecological risk assessment revealed that the 16 PAHs have a low probability of negatively affecting the surface sediments in the Nantong coast. However, the recent rapid urbanization and industrial development, and the pollution drainage caused by human activity inputs
Table 3 Concentration ranges of PAHs in the surface sediments of the Nantong coast, China, and some of their toxicity guidelines. Compound
NAP ACE ACY FLO PHE ANT FLA PYR B[a]A CHR B[b]F B[k]F B[a]P DB[a,h]A B[g,h,i]P I[1,2,3-cd]P SUM a b
Concentration range(ng g−1)
a
ND -21.78 ND-3.13 ND ND-7.45 ND-12.94 ND-1.82 ND-7.21 ND-5.69 0.05–3.35 0.08–8.29 0.15–5.79 0.1–2.8 0.02–6.51 0.07–9.84 0.1–7.76 0.02–4.49 1.4–87.09
Mean values(ng g−1)
5.99 0.21 ND 0.83 2.20 0.21 0.83 0.95 0.48 1.21 1.17 0.72 1.17 1.97 1.35 0.58 19.88
SQGb (ng g−1 dw)
Sites
ERL
ERM
bERL
ERL ~ ERM
NERM
160 16 44 19 240 85.3 600 665 261 384 – – 430 63.4 – – 4022
2100 500 640 540 1500 1100 5100 2600 1600 2800 – – 1600 260 – – 44,792
All sites All sites All sites All sites All sites All sites All sites All sites All sites All sites – – All sites All sites – – All sites
– – – – – – – – – – – – – – – – –
– – – – – – – – – – – – – – – – –
Not calculated due to the concentration of individual PAH compound being below the detection limits. SQG values taken from Long et al. (1995) and MacDonald et al. (1996).
Please cite this article as: Liu, N., et al., Distribution, sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in surface sediments from the Nantong Co..., Marine Pollution Bulletin (2016), http://dx.doi.org/10.1016/j.marpolbul.2016.09.020
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around the coastal area of Nantong means that the area should be properly managed to avoid further contamination by PAH pollutants. Acknowledgments This study was supported by the National Natural Science Foundation of China (grant nos. 41306152, 41306064, 31400371) and Special Scientific Research Funds of Land and Resources Public Welfare Industry (no. 201411072). References Boonyatumanond, R., Murakami, M., Wattayakorn, G., Togo, A., Takada, H., 2007. Sources of polycyclic aromatic hydrocarbons (PAHs) in street dust in a tropical Asian megacity, Bangkok, Thailand. Sci. Total Environ. 384 (1–3), 420–432. Bouloubassi, I., Roussiez, V., Azzoug, M., Lorre, A., 2012. Sources, dispersal pathways and mass budget of sedimentary polycyclic aromatic hydrocarbons (PAH) in the NW Mediterranean margin, Gulf of Lions. Mar. Chem. 142–144 (0), 18–28. Bragato, M., Joshi, K., Carlson, J.B., Tenório, J.A.S., Levendis, Y.A., 2012. Combustion of coal, bagasse and blends thereof: part II: speciation of PAH emissions. Fuel 96 (0), 51–58. Budzinski, H., Jones, I., Bellocq, J., Pierrad, C., Garrigues, P., 1997. Evaluation of sediment contamination by polycyclic aromatic hydrocarbons in the Gironde estuary. Mar. Chemophere. 58, 85–97. Callén, M.S., López, J.M., Iturmendi, A., Mastral, M.A., 2013. Nature and sources of particle associated polycyclic aromatic hydrocarbons (PAH) in the atmospheric environment of an urban area. Environ. Pollut. 183, 166–174. Carver, J.H., Machado, M.L., MacGregor, J.A., 1986. Application of modified Salmonella/microsome prescreen to petroleum-derived complex mixtures and polynuclear aromatic hydrocarbons (PAH). Mutat. Res. 174 (4), 247–253. Chen, C.W., Chen, C.F., 2011. Distribution, origin, and potential toxicological significance of polycyclic aromatic hydrocarbons (PAHs) in sediments of Kaohsiung Harbor. Taiwan. Mar. Pollut. Bull. 63, 417–423. Culotta, L., Stefano, C.D., Gianguzza, A., Mannino, M.R., Orecchio, S., 2006. The PAH composition of surface sediments from Stagnone coastal lagoon, Marsala (Italy). Mar. Chem. 99, 117–127. Deng, W., 2013. A Preliminary Study on the Composition, Distribution and Source Apportionment of Aliphatic and Polycyclic Aromatic Hydrocarbons in Surface Sediments from the South Yellow Sea and East China Sea. Ocean University of China, College of Marine Geosciences, pp. 63–96. Dobbins, R.A., Fletcher, R.A., Benner, J.B.A., Hoeft, S., 2006. Polycyclic aromatic hydrocarbons in flames, in diesel fuels, and in diesel emissions. Combust. Flame 144 (4), 773–781. Folk, R.L., 1957. Brazos River bar: a study in the significance of grain size parameters. J. Sediment. Res. 27 (1), 3–26. Guo, G.H., Wu, F.C., He, H.P., Zhang, R.Q., Li, H.X., Feng, C.L., 2012. Distribution characteristics and ecological risk assessment of PAHs in surface waters of China. Sci. China. Earth. Sci. 55 (6), 914–925. Guzzella, L., Roscioli, C., Viganò, L., Saha, M., Sarkar, S.K., Bhattacharya, A., 2005. Evaluation of the concentration of HCH, DDT, HCB, PCB and PAH in the sediments along the lower stretch of Hugli estuary, West Bengal, northeast India. Environ. Int. 31, 523–534. Harrison, R.M., Smith, D.J.T., Luhana, L., 1996. Source apportionment of atmospheric polycyclic aromatic hydrocarbons collected from an urban location in Birmingham, UK. Environ. Sci. Technol. 30 (3), 825–832. He, X., Pang, Y., Song, X., Chen, B., Feng, Z., Ma, Y., 2014. Distribution, sources and ecological risk assessment of PAHs in surface sediments from Guan River Estuary, China. Mar. Pollut. Bull. 80, 52–58. Huang, G.P., Chen, Y.J., Lin, T., Tang, J.H., Liu, D.Y., Li, J., Zhang, G., 2011. The distribution and ecological risk of polycyclic aromatic hydrocarbons of surface sediments in the intertidal zone of Bohai Bay, China. China Environ. Sci. 31 (11), 1856–1863. Larsen, R.K., Baker, J.E., 2003. Source apportionment of polycyclic aromatic hydrocarbons in the urban atmosphere: a comparison of three methods. Environ. Sci. Technol. 37 (9), 1873–1881. Lea-Langton, A.R., Ross, A.B., Bartle, K.D., Andrews, G.E., Jones, J.M., Li, H., Pourkashanian, M., Williams, A., 2013. Low temperature PAH formation in diesel combustion. J. Anal. Appl. Pyrol. 103 (0), 119–125. Lee, C.L., Hsieh, M.T., Fang, M.D., 2005. Aliphatic and polycyclic aromatic hydrocarbons in sediments of Kaohsiung Harbour and Adjacent Coast, Taiwan. Environ. Monit. Assess. 100, 217–234. Li, X., Hou, L., Li, Y., Liu, M., Lin, X., Cheng, L., 2016. Polycyclic aromatic hydrocarbons and black carbon in intertidal sediments of China coastal zones: concentration, ecological risk, source and their relationship. Sci. Total Environ. (Science of the Total Environment. On line).
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Yu, X., Ma, J., Kumar, K.R., Zhu, B., An, J., He, J., Li, M., 2016. Measurement and analysis of surface aerosol optical properties over urban Nanjing in the Chinese Yangtze River Delta. Sci. Total Environ. 542, 277–291. Yuan, H.M., Li, T.G., Ding, X.G., Zhao, G.M., Ye, S.Y., 2014. Distribution, sources and potential toxicological significance of polycyclic aromatic hydrocarbons (PAHs) in surface soils of the Yellow River Delta. China. Mar. Pollut. Bull. 83, 258–264. Yunker, M.B., Macdonald, R.W., Vingarzan, R., Mitchell, R.H., Goyette, D., Sylvestre, S., 2002. PAHs in the Fraser River basin: a critical appraisal of PAH ratios as indicators of PAH source and composition. Org. Geochem. 33, 489–515. Zhang, J., Cai, L.Z., Yuan, D.X., Chen, M., 2004. Distribution and sources of polynuclear aromatic hydrocarbons in Mangrove surficial sediments of Deep Bay, China. Mar. Pollut. Bull. 49, 479–486. Zhang, R., Zhang, F., Zhang, T.C., 2013. 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Please cite this article as: Liu, N., et al., Distribution, sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in surface sediments from the Nantong Co..., Marine Pollution Bulletin (2016), http://dx.doi.org/10.1016/j.marpolbul.2016.09.020
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Distribution, sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in surface sediments from the Nantong Coast, China Na Liu a,b,c,1, Xian Li b,1, Daolai Zhang c,⁎, Qiang Liu d, Lihui Xiang d, Ke Liu a, Dongyun Yan a, Yue Li a a
College of Environmental Science and Engineering, Qingdao University, Qingdao 266071, China Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China Key Laboratory of Coastal Wetland Biogeosciences, China Geological Survey, Qingdao 266071, China d Eastern China Geological & Mining Organization for Non-ferrous Metals in Jiangsu Province, Nanjing 210007, China b c
a r t i c l e
i n f o
Article history: Received 26 July 2016 Received in revised form 2 September 2016 Accepted 10 September 2016 Available online xxxx Keywords: Polycyclic aromatic hydrocarbons Sediment Source Ecological risk assessment Nantong Coast
a b s t r a c t The distribution, sources, and ecological risk assessment of 16 polycyclic aromatic hydrocarbons (PAHs) in surface sediments from the Nantong coast in China were investigated. The results indicated that the total concentrations of the 16 PAHs in the surface sediments from the study area ranged from 1.4 to 87.1 ng g−1 dw (mean value 19.9 ng g−1 dw), which were generally low compared to the adjacent offshore area and other coastal zones around the world. The selected PAH ratios and the principal components analysis for each site showed that petroleum combustion and petrogenic pollution (mainly caused by petroleum spills) were the dominant PAHs sources in the surface sediments of the coast. The ecological risk assessment indicated that most of the individual PAHs had few negative effects in this area. © 2016 Elsevier Ltd. All rights reserved.
The recent rapid development of industry, the economy, and urban expansion along the world's coastlines has meant that polycyclic aromatic hydrocarbons (PAHs) (Table 1) have attracted the attention of environmental chemists, toxicologists, and regulatory agencies over the past few decades. PAHs are ubiquitous, volatile organic pollutants in the environment that are composed of two or more fused aromatic rings (Bouloubassi et al., 2012; Bragato et al., 2012; Callén et al., 2013; Carver et al., 1986; Lea-Langton et al., 2013; Readman et al., 2002). They have low aqueous solubilities and high octanol/water partition coefficients, which mean that PAHs entering the ocean tend to associate with particulate material and accumulate in sediments (Lindgren et al., 2014; Naes et al., 1995). PAHs in marine sediments have attracted considerable attention around the world because of their negative effects on marine aquatic systems and humans (Chen and Chen, 2011; Deng, 2013; Guo et al., 2012; Culotta et al., 2006; Guzzella et al., 2005; Soliman et al., 2014). The coastal zones are where the land and marine ecosystems mix and they receive substantial quantities of PAHs, which may pose an ecological risk to coastal ecosystems. It has been suggested that the coastal sediments in China are heavily polluted by PAHs, especially on coasts where there is extensive anthropogenic activity (Li et al., 2016). In addition, many studies have reported that large concentrations of PAHs and the associated high ecological risks have been observed in coastal sediments (Lee et al., ⁎ Corresponding author. E-mail addresses: [email protected] (N. Liu), [email protected] (D. Zhang). 1 Co-first authors.
2005; Wang et al., 2012; Zhang et al., 2016). Therefore, concerns about PAH pollution, ecological risk, and PAH pollution sources in coastal marine sediments of China have increased recently (Huang et al., 2011; Yuan et al., 2014; Zhang et al., 2016). Nantong is regarded as the “Golden Coast” and “Golden Waterway” and is located at the southernmost tip of Jiangsu's coastal zone and is to the north of the Yangtze River. It was one of the earliest open-up cities and the city's economy has developed rapidly, but this has simultaneously brought about environmental deterioration. The Nantong coast provided large numbers of areas for land use. The quality of Nantong coast has been affected by increased human activity, accelerated industrialization, and the rapid expansion of the local economy, which has exposed it to an increasing risk of pollution from toxic chemicals. In addition, rapid economic growth on the coast around Nantong has raised concerns about significant pollution of aquatic environments, especially of sediments that act as a natural repository of organic pollutants. However, only a few studies about the characteristics of the polychlorinated naphthalenes and polybrominated diphenyl ethers present in sediments located around the Nantong coast have been conducted (Wang et al., 2016; Zhang et al., 2015). Most of these studies focused on areas south of Nantong, such as the surface sediments of the Yangtze River and the Chongming wetland (Wang et al., 2012; Yu et al., 2016). This means that there is a lack of data describing the sediment PAH concentrations on the Nantong coast. Therefore, we investigated the distribution, source, and ecological risk posed by PAHs in the surface sediments of the Nantong coast. The results of this study will serve as a
http://dx.doi.org/10.1016/j.marpolbul.2016.09.020 0025-326X/© 2016 Elsevier Ltd. All rights reserved.
Please cite this article as: Liu, N., et al., Distribution, sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in surface sediments from the Nantong Co..., Marine Pollution Bulletin (2016), http://dx.doi.org/10.1016/j.marpolbul.2016.09.020
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Table 1 Descriptive of 16 PAHs. Species
Abbreviations
Number of rings
Naphthalene Acenaphthylene Acenaphthene Fluorene Phenanthrene Anthracene Fluoranthene Pyrene Benzo(a)anthracene Chrysene Benzo(b)fluoranthene Benzo(k)fluoranthene Benzo(a)pyrene Dibenzo(a,h)anthracene Indeno(1,2,3-cd)pyrene Benzo(g,h,i)perylene
NAP ACY ACE FLO PHE ANT FLA PYR B[a]A CHR B[b]F B[k]F B[a]P DB[a,h]A I[1,2,3-cd]P B[g,h,i]P
2 3 3 3 3 3 4 4 4 4 5 5 5 5 6 6
baseline to assess future anthropogenic effects and will be valuable to local governments. The sampling stations were arranged from the Nantong coast in Jiangsu Province, China. The surface sediments (depth 0–5 cm) were collected from the sample sites using a Smith–Mcintyre grab sampler, the position of the sites were showed in Fig.1 (121.42–122.23 E, 31.71–32.30 N). The sampler of each sample was washed by the seawater in the same sample site. All of the sediments were wrapped in solvent-rinsed aluminum foil, transported to the laboratory stored at −20 °C until further analysis. The samples were freeze-dried and ground into a fine powder (b0.25 mm) for PAHs analysis. The extraction of PAHs was carried out according to the method reported by Nicola et al. (2005). A mixture of perdeuterated internal standards ([d-10]phenanthrene, [d-10]pyrene, [d-12]chrysene, [d-12]perylene, and [d-12]benzo[g,h,i] perylene) was added to the sieved samples (10 g). Each sample was subsequently mixed with an equal quantity of anhydrous sodium sulfate in 60 mL of
dichloromethane/acetone (1:1, v/v) solution for 20 min and then sonicated three times. The extract was concentrated, solvent-exchanged with n-hexane, and further reduced to approximately 1 mL under gentle nitrogen flow. The resulting extract was loaded into a 1:2 alumina/silica gel glass column for fractionation and cleanup. The first fraction, which contained aliphatic hydrocarbons, was eluted with 15 mL n-hexane. The second, which contained PAHs, was collected after elution with 5 mL nhexane and 70 mL of methylene chloride/n-hexane (30:70) solution. The purified extracts were concentrated to a volume of 1 mL under a stream of nitrogen. Known quantities of an internal standard were added to the sample prior to instrumental analysis. Grain size analysis for the surface sediments were performed with a laser granulometer (Malvern Mastersizer 2000) after the organic matter digestion with 10% H2O2 and the dispersion with sodium hexametaphosphate. Grain size parameters were calculated following the formula of Folk (1957). The PAH concentrations were measured by gas chromatography using an HP 5890 GC equipped with an HP-5MS capillary column (30 m, 0.25 mm i.d., 0.25 μm film thickness) coupled to an HP 5975 mass spectrometer with a mass-selective detector. The carrier gas, helium, was introduced at a flow rate of 1.0 mL min−1. The oven temperature was initially set at 70 °C, then increased by 20 °C min− 1 to 280 °C, which was held for 24 min. Quantitation was conducted by using the primary ions for each compound. Two to three secondary ions were used for qualitative confirmation. The glassware and sodium sulfate were solvent-rinsed and heated for 4 h at 450 °C prior to use. For quality assurance and control, a spiked blank, a procedural blank, matrix spikes, and a duplicate sample were analyzed in the same way as the test sample for each batch of 10 samples. No quantifiable targets were detected in these blanks. Analysis of a reagent blank demonstrated that the analytical system and glassware were free of contamination. The recovery for the spiked blanks was 75.0%–120.0%. The results reported in this work were not corrected for recoveries and the relative standard deviation for parallel samples was b15% (n = 3).
Fig. 1. Locations of the studied areas of Nantong coast of China.
Please cite this article as: Liu, N., et al., Distribution, sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in surface sediments from the Nantong Co..., Marine Pollution Bulletin (2016), http://dx.doi.org/10.1016/j.marpolbul.2016.09.020
N. Liu et al. / Marine Pollution Bulletin xxx (2016) xxx–xxx
The ANT/(ANT + PHE), FLA/(FLA + PYR), B[a]A/(B[a]A + CHR), and I[1,2,3-cd]P/(I[1,2,3-cd]P + B[g,h,i]P) ratios were calculated to determine the source of the PAHs. These sources can be categorized into different groups (Yunker et al., 2002): ANT/(ANT + PHE) b 0.1 and FLA/ (FLA + PYR) b 0.4: petroleum pollution; 0.1 b ANT/(ANT + PHE) b 0.5 and 0.4 b FLA/(FLA + PYR) b 0.5: petroleum combustion; ANT/ (ANT + PHE) N 0.5 and 0.1 b FLA/(FLA + PYR) b 0.5: grass, wood, and charcoal combustion; B[a]A/(B[a]A + CHR) b 0.2: petroleum pollution; B[a]A/(B[a]A + CHR) N 0.35: pyrolytic processes; I[1,2,3-cd]P/(I[1,2,3cd]P + B[g,h,i]P) b 0.2: petroleum pollution; 0.2 b I[1,2,3-cd]P/(I[1,2,3cd]P + B[g,h,i]P) b 0.5: petroleum combustion; and I[1,2,3-cd]P/ (I[1,2,3-cd]P + B[g,h,i]P) N 0.5: grass, wood, and charcoal combustion. Principal component analysis (PCA) with multivariate linear regression (MLR) was conducted to identify the source contributions of the different PAHs and was performed using IBM SPSS Statistics v20 for Windows. The spatial distributions of PAHs in the surface sediments from the Nantong coast are shown in Fig. 2. The total concentrations of 16 US EPA priority PAHs ranged from 1.4 to 87.1 ng g− 1 dw with a mean value of 19.9 ng g−1 dw. The highest concentration was obtained from site NT25 (87.1 ng g−1 dw) followed by NT24 (57.8 ng g−1 dw), whereas the lowest concentration was measured at site NT52 (1.4 ng g−1 dw) where only eight PAH compounds were detected. Anthropogenic use of the terrestrial area has continually increased, which means that the higher concentrations of PAHs detected inshore might be due to human activities. On the coast at Nantong, there are two types of ocean currents: the forward ocean current of the East Sea and the rotary ocean current of the Yellow Sea (Yao, 2013). The crests of these two waves converge and their energies aggregate. This results in the active movement of sediments that come from the Yangtze River estuary through coastal erosion of the ancient Yangtze River Delta and from ocean sediments. They have caused sand ridges to form in Nantong's offshore shallow water and they are significant sediment sources. Furthermore, it is possible that the PAHs in the Yangtze River might be carried into the study area. ACYs were not found in the study area, ACEs were found in 18.9% of the sediment samples, ANTs were present in 39.6% of the samples, FLAs were found at 50.9% of the sites, and the detection rates for PYR, FLO, PHE, and NAP were 84.9%, 86.8%, 64.2%, and 98.1%, respectively, B[a]A, CHR, B[b]F, B[k]F, B[a]P, DB[a,h]A, I[1,2,3-cd]P, and B[g,h,i]P were all present in the sediments. The results showed that NAP account for over 30% of total concentrations of the 16 PAHs at the sites, whereas ACY and ANT only account for about 1.0%. The mean value order for the 16 PAHs was NAP N PHE N DB[a,h]A N I[1,2,3-cd]P N CHR N B[a]P N B[b]F N PYR N FLO N FLA N B[k]F N B[g,h,i]P N B[a] A N ANT N ACE N ACY. The PAHs in the surface sediments from the Nantong coast and its surrounding area were compared to the PAH concentrations in surface
Fig. 2. Total PAHs in the surface sediments from the Nantong coast, China.
3
Table 2 Comparison of PAH concentrations (ng g−1 dw) in surface sediments from different coastal zones around the world and their adjacent areas.
Nantong, China Chongming Island, China The intertidal zone of Bohai Bay, China Yangtze estuary, China Kaohsiung, Taiwan Haizhou Bay, China South Yellow Sea Guan River, China Gulf of Mexico, North America Chao Phraya River Estuary, Thailand a
Mean (ng g−1 dw)
∑PAHs (ng g−1 dw)
References
19.9 –a 140 ± 84.1
1.4–87.1 38.7–136.2 –
This study Wang et al. (2012) Huang et al. (2011)
449.8 – – 825 ± 716 132.7 305
76.9–2936.8 88–729 72.5–805.2 61–3601 91–218 52–403
Wang et al. (2012) Lee et al. (2005) Zhang et al. (2013) Deng (2013) He et al. (2014) Wang et al. (2011)
2290
6–8399
Ruchaya et al. (2006)
not reported in the reference.
sediments from different coastal zones around the world and their adjacent areas. Table 2 shows that the total concentrations of the 16 PAHs obtained from the Nantong coast (1.4 to 87.1 ng g−1 dw; mean value 19.9 ng g−1 dw) were less than the values reported for adjacent areas, such as Chongming Island, China (38.7 to 136.2 ng g− 1 dw; mean value 737.0 ng g−1) (Wang et al., 2012), the Yangtze River (76.9 to 2936.8 ng g−1 dw; mean value 449.8 ng g−1 dw) (Wan et al., 2012), and the South Yellow Sea (61 to 3601 g−1 dw; mean value 825 ± 716 ng g−1 dw) (Deng, 2013). They were also much lower than the intertidal zone in Bohai Bay, China (mean value, 140 ± 84 ng g−1 dw) (Huang et al., 2011), Haizhou Bay (mean value 140 ± 84.1 ng g− 1 dw) (Zhang et al., 2013), the Guanhe River (91–218 ng g−1 dw; mean value 132.7 ng g− 1 dw) (He et al., 2014), Kaohsiung, Taiwan (88– 728 ng g−1 dw) (Lee et al., 2005), Chao Phraya River Estuary, Thailand (6–8399 ng g− 1 dw; mean value 2290 ng g− 1 dw) (Ruchaya et al., 2006), and the Gulf of Mexico, North America (52–403 ng g− 1 dw; mean value 305 ng g−1 dw) (Wang et al., 2011). The mean grain size (Mz) of the samples in the Nantong coast varies between 2.0Φ and 7.4Φ, with a mean value of 4.3Φ, indicating that the sediments are mainly composed of coarse silt-sized components, which meant that the properties of the sediment in this area were considerably affected by sediment texture. The PAHs adsorbed in sand sediments are easily washed out to adjacent seas and coastal zones. So PAH compounds were much lower in the Nantong coast area. The composition patterns of the PAHs ranged by ring size in the Nantong coast surface sediments are shown in Fig. 3. The PAH compositional patterns in the sediments were mainly 2-ring (NAP) and 5-ring (B[b]F, B[k]F, B[a]P, and DB[a,h]A) compounds. The 2- and 5-ring PAHs accounted for 30.1% and 25.3%, respectively, of the total PAHs, whereas the 3-ring (PHE and ANT), 4-ring (FLA, PYR, B[a]A, and CHR), and 6-ring (B[g,h,i]P and I[1,2,3-cd]P) compounds accounted for 17.4%, 17.4%, and 9.7%, respectively. The PAH composition followed a gradient of 2-ring N5-ring N 3-ring N4-ring N 6-ring. This was different from its adjacent sea, the Yellow Sea (3-ring and 4-ring PAHs were more abundant), and the Guanhe River estuary in Jiangsu Province (3-ring and 5-ring PAHs were more abundant), China. This means that the PAH concentrations in the sediments are influenced by a number of factors, including total organic carbon content, mean sediment grain size, clay content, currents, and pollution source (Zhang et al., 2016). PAHs are distributed in environments throughout the world and are generated by many different pathways. Therefore, it is important to identify PAH sources if their distribution is to be controlled and responsibility for remedial action is to be properly allocated. Various sources produce different compounds and lead to different concentrations in the environment. Studies have shown that isomeric ratios and PCA of PAH concentration can be used to identify the different sources (Budzinski et al., 1997; Magi et al., 2002; Sicre et al., 1987; Soclo et al.,
Please cite this article as: Liu, N., et al., Distribution, sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in surface sediments from the Nantong Co..., Marine Pollution Bulletin (2016), http://dx.doi.org/10.1016/j.marpolbul.2016.09.020
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100% 90% 80% 70% 6-ring
60%
5-ring
50%
4-ring 40%
3-ring
30%
2-ring
20% 10%
NT1 NT2 NT3 NT4 NT5 NT6 NT7 NT8 NT9 NT10 NT11 NT12 NT13 NT14 NT15 NT16 NT17 NT18 NT19 NT20 NT21 NT22 NT23 NT24 NT25 NT26 NT27 NT28 NT29 NT30 NT31 NT32 NT33 NT34 NT35 NT36 NT37 NT38 NT39 NT40 NT41 NT42 NT43 NT44 NT45 NT46 NT47 NT48 NT49 NT50 NT51 NT52 NT53
0%
Fig. 3. PAH composition patterns by ring size in surface sediments from the Nantong coast, China.
2000; Nilsen et al., 2015). Therefore, we used these methods to further assess the sources of the PAHs in surface sediments from the Nantong coast. The ANT/(ANT + PHE), FLA/(FLA + PYR), B[a]A/(B[a]A + CHR), and I[1,2,3-cd]P/(I[1,2,3-cd]P + B[g,h,i]P) ratios have been shown to be useful in the identification of PAH sources. Fig. 4 shows the ratios and sources of PAHs in surface sediments from the Nantong coast. Petroleum usually contains compounds that are more thermodynamically stable, such as NAP, FLA, PHE, and CHR. FLA and PYR are usually the most abundant compounds from pyrolytic PAH sources, such as combustion of petroleum, grass, wood, and coal (Magi et al., 2002; Sicre et al., 1987; Zhang et al., 2004). The ANT/(ANT + PHE) and FLA/ (FLA + PYR) ratios from NT8, NT11, NT29, and NT31 suggested that petroleum was the pollution source at these sites. NT14, NT18, NT26, NT40, and NT51 were affected by pyrolytic PAH sources, and the NT1 and NT4 site results indicated that both combustion and petroleum were the principle sources. The PAHs at sites NT3, NT15, NT17, NT19, and NT24 originated from a mixture of petroleum and coal combustion sources, while the PAHs at NT10, NT16, and NT25 were dominated by
petroleum pollution and petroleum combustion. The B[a]A/ (B[a]A + CHR) and I[1,2,3-cd]P/(I[1,2,3-cd]P + B[g,h,i]P) ratios indicated that NT6 and NT18 were dominated by petroleum pollution and combustion. The pollution at 14 of the sites (NT11, NT15, NT20, NT23, NT24, NT27, NT28, NT34, NT36, NT39, NT41, NT42, NT43, and NT48) was mainly caused by petroleum spills, and the PAHs in the sediments from NT3, NT5, and NT9 originated from mixed petroleum pollution and combustion. The PAHs in N60% of the sites, including NT1, NT2, NT7, NT8, NT10, NT12, NT13, NT16, NT17, NT19, NT21, NT22, NT25, NT26, NT29, NT30, NT31, NT32, NT33, NT35, NT37, NT38, NT40, NT44, NT45, NT46, NT47, NT49, NT50, NT51, NT52, and NT53 were produced by petroleum combustion, whereas the PAHs at NT4 and NT14 were probably produced by grass, wood, and charcoal combustion. PCA was used to further examine the relationships between PAH composition and the possible chemical sources for each factor. Loading plots of the two principal components are shown in Fig. 5. Most of the variance (85.1%) in the normalized dataset can be explained by the first two factors.
Fig. 4. Ratios and sources of PAHs in surface sediments from the Nantong coast, China.
Please cite this article as: Liu, N., et al., Distribution, sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in surface sediments from the Nantong Co..., Marine Pollution Bulletin (2016), http://dx.doi.org/10.1016/j.marpolbul.2016.09.020
N. Liu et al. / Marine Pollution Bulletin xxx (2016) xxx–xxx
Fig. 5. Loading plots for the two principal components.
The first principal component (PC1) of all the individual PAHs accounted for 65.3% of the variance in the dataset. High positive loadings for NAP, FLA, PYR, B[a]A, CHR, B[b]F, B[k]F, B[a]P, DB[a,h]A, B[g,h,i]P, and I[1,2,3-cd]P were observed for this factor. B[b]F, B[k]F, B[a]P, I[1,2,3-cd]P, and DB[a,h]A belong to the high molecular weight PAHs with 4–6-rings, and B[g,h,i]P has been identified as a tracer for automobile emissions because it has been found to be enriched along with B[a]P in traffic tunnel emissions (Harrison et al., 1996; Larsen and Baker, 2003). B[k]F and its isomers, such as B[b]F and B[a]P, are dominant compounds in particulate samples from roadside air (Boonyatumanond et al., 2007). Therefore, vehicular traffic pollution was a major contributor to PAH contamination in PC1. In contrast, PC2, which accounted for 19.7% of total variance, was positively dominated by low-molecularweight PAHs, such as ACE, ANT, FLO, and PHE. PAHs with low molecular weights are abundant in petrogenic sources, which are mainly caused by petroleum spills (Dobbins et al., 2006; Marr et al., 1999), whereas those with high molecular weights are abundant in compounds from pyrolytic sources.
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The isomeric ratios and PCA led to the similar conclusion: petroleum combustion sources and petrogenic pollution (mainly caused by petroleum spills) were dominant in the surface sediments from the Nantong coast. Pyrolytic PAHs may come from the diesel engine emissions produced by shipping. Nantong is located at the intersection of the coastal economic zone and the Yangtze River Economic Zone, and it borders Shanghai, which is the international metropolis of China. The geographical position of Nantong has promoted local and rapid economic development in this city. In addition, industrial emissions, heavy traffic, and coal heating could also have increased the PAH loadings through atmospheric deposition and freshwater run off. Sediment quality guidelines (SQGs) are based on the Biological Effects Database for Sediments. They are commonly used in sediment assessments of marine environments (Long et al., 2006). SQGs provide two target values: the effects range low (ERL) and effects range median (ERM) values, which are established using the 10th and 50th percentiles, respectively, in a database of increasing concentrations associated with adverse biological effects. Table 3 shows the toxicity guidelines for 12 PAHs and classifies the sites into three different ranges, which are defined by the ERL and ERM values. The concentration of individual PAHs in the surface sediments of the Nantong coast were all below the ERL, which indicated that the PAHs in the sediments do not have any adverse effect on organisms. However, with the exception of ACY, all 16 PAHs were detected in the surficial sediments samples. Therefore, more attention should be paid to protecting the Nantong coast, although the probability of negative effects from the PAH compounds is low. Additionally, there were no reported sediment quality guideline values for B[k]F, B[a]P, B[g,h,i]P, and I[1,2,3-cd]P, but they were found at all the sites. The total concentration of 16 US EPA priority PAHs ranged from 1.4 to 87.1 ng g−1 dw with a mean value of 19.9 ng g−1 dw in the Nantong coast area, but they had a relatively low PAH contamination value compared to the adjacent areas and other coastal zones around the world. The PAHs in the surface sediments of the Nantong coast mainly originated from petrogenic pollution (mainly caused by petroleum spills) and petroleum combustion. The rapid economic development of the city might result in industrial emissions, heavy traffic, diesel engine exhausts from shipping, and coal powered heating, which would raise PAH loadings through atmospheric deposition and freshwater run off. The ecological risk assessment revealed that the 16 PAHs have a low probability of negatively affecting the surface sediments in the Nantong coast. However, the recent rapid urbanization and industrial development, and the pollution drainage caused by human activity inputs
Table 3 Concentration ranges of PAHs in the surface sediments of the Nantong coast, China, and some of their toxicity guidelines. Compound
NAP ACE ACY FLO PHE ANT FLA PYR B[a]A CHR B[b]F B[k]F B[a]P DB[a,h]A B[g,h,i]P I[1,2,3-cd]P SUM a b
Concentration range(ng g−1)
a
ND -21.78 ND-3.13 ND ND-7.45 ND-12.94 ND-1.82 ND-7.21 ND-5.69 0.05–3.35 0.08–8.29 0.15–5.79 0.1–2.8 0.02–6.51 0.07–9.84 0.1–7.76 0.02–4.49 1.4–87.09
Mean values(ng g−1)
5.99 0.21 ND 0.83 2.20 0.21 0.83 0.95 0.48 1.21 1.17 0.72 1.17 1.97 1.35 0.58 19.88
SQGb (ng g−1 dw)
Sites
ERL
ERM
bERL
ERL ~ ERM
NERM
160 16 44 19 240 85.3 600 665 261 384 – – 430 63.4 – – 4022
2100 500 640 540 1500 1100 5100 2600 1600 2800 – – 1600 260 – – 44,792
All sites All sites All sites All sites All sites All sites All sites All sites All sites All sites – – All sites All sites – – All sites
– – – – – – – – – – – – – – – – –
– – – – – – – – – – – – – – – – –
Not calculated due to the concentration of individual PAH compound being below the detection limits. SQG values taken from Long et al. (1995) and MacDonald et al. (1996).
Please cite this article as: Liu, N., et al., Distribution, sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in surface sediments from the Nantong Co..., Marine Pollution Bulletin (2016), http://dx.doi.org/10.1016/j.marpolbul.2016.09.020
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Please cite this article as: Liu, N., et al., Distribution, sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in surface sediments from the Nantong Co..., Marine Pollution Bulletin (2016), http://dx.doi.org/10.1016/j.marpolbul.2016.09.020