Source apportionment of polycyclic aromatic hydrocarbons in continental shelf of the East China Sea with dual compound-specific isotopes (δ13C and δ2H)

Journal Pre-proofs Source apportionment of polycyclic aromatic hydrocarbons in continental shelf of the East China Sea with dual compound-specific isotopes (δ 13C and δ 2H) Rui Zhang, Tiegang Li, James Russell, Fan Zhang, Xin Xiao, Yaxin Cheng, Zhiyong Liu, Minglei Guan, Qi Han PII: DOI: Reference:

S0048-9697(19)35452-X https://doi.org/10.1016/j.scitotenv.2019.135459 STOTEN 135459

To appear in:

Science of the Total Environment

Received Date: Revised Date: Accepted Date:

16 September 2019 7 November 2019 8 November 2019

Please cite this article as: R. Zhang, T. Li, J. Russell, F. Zhang, X. Xiao, Y. Cheng, Z. Liu, M. Guan, Q. Han, Source apportionment of polycyclic aromatic hydrocarbons in continental shelf of the East China Sea with dual compoundspecific isotopes (δ 13C and δ 2H), Science of the Total Environment (2019), doi: https://doi.org/10.1016/j.scitotenv. 2019.135459

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

© 2019 Published by Elsevier B.V.

Title Page Manuscript title: Source apportionment of polycyclic aromatic hydrocarbons in continental shelf of the East China Sea with dual compound-specific isotopes (δ13C and δ2H)

Word count: 5918

Author names, affiliations and institutional mailing addresses: Rui Zhang, Yaxin Cheng Affiliation a: School of Geodesy and Geomatics Engineering, Jiangsu Ocean University, Lianyungang 222005, Jiangsu Province, China. Affiliation b: Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI 02912, USA. Affiliation c: Co-Innovation Center of Jiangsu Marine Bio-industry Technology, Jiangsu Ocean University, Lianyungang 222005, Jiangsu Province, China. Affiliation d: Jiangsu Key Laboratory of Marine Bioresources and Environment, Jiangsu Ocean University, Lianyungang 222005, Jiangsu Province, China. Address: No.59, Cangwu Road, Xinpu District, Lianyungang, Jiangsu Province, China Tiegang Li Affiliation: First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China. Address: No. 6, Xianxialing Road, Laoshan District, Qingdao, Shandong Province, China.

E-mail: [email protected] James Russell Affiliation c: Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI 02912, USA Address: 324 Brook Street, Providence, RI 02912, USA. Xin Xiao, Fan Zhang Affiliation: Department of Chemical Engineering, Jiangsu Ocean University, Lianyungang 222005, Jiangsu Province, China Address: No.59, Cangwu Road, Xinpu District, Lianyungang, Jiangsu Province, China Zhiyong Liu Affiliation: School of Radiation Medicine and Protection, Medicine College, Soochow University, Suzhou 100083, Jiangsu Province, China. Address: No. 199, Renai Road, Industrial Park District, Suzhou, Jiangsu Province, China Minglei Guan Affiliation: School of Geodesy and Geomatics Engineering, Jiangsu Ocean University, Lianyungang 222005, Jiangsu Province, China. Address: No.59, Cangwu Road, Xinpu District, Lianyungang, Jiangsu Province, China Qi Han Affiliation: School of Ocean Sciences, China University of Geosciences, Beijing 100083, People’s Republic of China.

Address: No.3, Xueyuan Road, Haidian District, Beijng, People’s Republic of China

Correspondence author Tiegang Li Affiliation: First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, China. Tel: +86-0532-88967468 Email: [email protected]

Source apportionment of polycyclic aromatic hydrocarbons in continental shelf of the East China Sea with dual compound-specific isotopes (δ13C and δ2H) Rui Zhanga,b,c,d, Tiegang Lie,f,g1, James Russellb, Fan Zhangh, Xin Xiaoh, Yaxin Chenga, Zhiyong Liui, Minglei Guana, Qi Hank

a School of Geomatics and Marine Information, Jiangsu Ocean University, Lianyungang 222005, Jiangsu Province, China. b Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI 02912, USA. c Co-Innovation Center of Jiangsu Marine Bio-industry Technology, Huaihai Institute of Technology, Lianyungang 222005, Jiangsu Province, China. d Jiangsu Key Laboratory of Marine Bioresources and Environment, Huaihai Institute of Technology, Lianyungang 222005, Jiangsu Province, China. e First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, Shandong Province, China. 1

Corresponding author. E-mail: [email protected]

f Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266061, PR China g University of Chinese Academy of Sciences, Beijing 100049, China h Department of Chemical Engineering, Jiangsu Ocean University 222005, Jiangsu Province, China i School of Radiation Medicine and Protection, Medicine College, Soochow University, Suzhou 215123, Jiangsu Province, China. j School of Ocean Sciences, China University of Geosciences, Beijing 100083, China.

Abstract In this study, we firstly report the application of a dual-isotope approach for the source apportionment of polycyclic aromatic hydrocarbons (PAHs) in the East China Sea (ECS). The δ13C and δ2H isotope signatures of the PAHs were determined in the surface sediments collected from the ECS. Statistical modeling based on a Bayesian Markov chain Monte Carlo (MCMC) framework was used to the environmental dual-isotope PAH data. An end-member PAH isotope database was also compiled to account for the uncertainties and quantitative contributions on the potential PAH sources, including coal combustions, liquid fossil fuel combustions, biomass combustions and petrogenic sources. The results indicate that the PAHs in the ECS had a clear predominance of the coal combustion source (~42%). The combustion of liquid fossil fuels, biomass as well as petrogenic sources represented approximately 23%, 21%, and 11% of the total PAH burden, respectively. This study on the source apportionment of environmental PAHs will provide a reference for

improvingemission inventories of the PAHs, and also give guidance for the efforts to extenuate PAH pollutions in the marginal sea.

Keywords: East China Sea; PAHs; Source apportionment; Dual-CSIA; δ13C; δ2H

1. Introduction Polycyclic aromatic hydrocarbons (PAHs) are predominantly anthropogenic organic molecules of environmental concern because of their mutagenic and carcinogenic properties (Bostrom et al., 2002; Ghosal et al., 2015). As a result, they cause a threat to both human health and the environment, considering their toxicity. PAHs can be classified into three main categories: 1) petrogenic-derived PAHs formed from the slow maturation of organic matter under geothermal gradient conditions; 2) pyrogenic-derived PAHs from the incomplete combustion of recent (e.g., biomass burning) and fossil (e.g., coal) organic matter; and 3) diagenetic PAHs derived from biogenic precursors (Baumard et al., 1998; Soclo et al., 2000). Given the ecotoxicological importance, the source identification of PAHs represents a significant aspect of environmental monitoring in coastal and marine areas. Previous studies of PAH source discrimination have usually depended on molecular criteria to identify between pyrogenic PAHs (combustion-derived, e.g., emissions from biomass combustion and motor vehicles) and petrogenic (petroleum-derived, e.g., oil leakages) (Wakeham et al., 1996; Budzinski et al., 1997; Yunker et al., 1996). These molecular criteria are based on the overall PAH molecular

fingerprints or the relative concentrations of isomers with the same mass. However, chemical and biological contaminants are often subjected to change the composition of PAHs, which may result in hindering identification of the sources (O’Malley et al., 1994). In addition, owing to the substantial overlapping in the isomer ratios within the source types, it is difficult for quantitative source apportionment using the diagnostic ratios of PAHs (Galarneau, 2008). To overcome these limitations of approaches on the “classical” PAH source identifications, the intrinsic carbon isotopei compostitions of an individual PAH molecule are considered as a more conservative source tracer (O’Malley et al., 1994; McRae et al., 1999; Reddy et al., 2002; Mandalakis et al., 2004). Despite the well-established tool for stable carbon (δ13C) compound-specific isotope analysis (CSIA) on individual PAHs to discriminate sources (McRae et al., 1999; Bosch et al., 2015; Jautzy et al., 2015; Holman and Grice, 2018), however combining both stable carbon and hydrogen (δ2H) isotopic signatures (i.e., dual-CSIA) may be a far more powerful tool for the quantitative determining the sources of contaminants in the environment (Bosch et al., 2015; Jautzy et al., 2015; Holman and Grice, 2018; Sun et al., 2003; Wang et al., 2004; Vitzthum et al., 2011; Grice et al., 2009). The continental shelf of the East China Sea (ECS) is one of the widest shelves and river-dominated ocean margins in the world (Liu et al., 2007; Guo et al., 2006). It receives large amounts of riverine terrigenous sediment in its estuaries and inner shelf, characterized by the mud area of the subaqueous delta and the southeast coastal mud belt, i.e. the Zhe-Min coastal mud belt. These mud areas are

accumulative deposition sinks of sediment loads from the Changjiang River into the ECS (Liu et al., 2007). However, environmental contamination of PAHs in the ECS is recognized as being a major environmental problem (Guo et al., 2006; Li et al., 2012; Liu et al., 2012a, 2012b; Lin et al., 2013; Yu et al., 2015; Wang et al., 2016; Wang et al., 2017; Chen et al., 2018). A better understanding of the PAH sources in the ECS will be essential to mitigate PAHs pollutions. Nevertheless, the relative contributions of the different sources of PAHs are still poorly understood in the ECS. In this study, the objectives are designed to: 1). report the detailed spatial distributions of the PAHs and dual-CSIA of individual compounds; 2). identify and revealed their efficiency to quantitatively decipher between different PAHs sources in the ECS with the help of dual-CSIA mixing end-member model.

2. Materials and methods 2.1 Sample collection The ECS is a typical marginal sea that features as a semi-enclosed marginal basin surrounded by a series of East Asian countries, e.g., China, Korea, and southern Japan, It is noted for high levels of river runoff, receiving a large amount of terrigenous sediments mainly from the Changjiang (Yangtze) River. In this study, 53 surface sediment samples (0–2 cm) were collected in the ECS during 2013–2015 using a stainless-steel grab sampler (Fig. 1). Immediately after collection, all the sediment samples were put into precleaned aluminum foil, and then were refrigerated. In addition, we also collected a sample of coal combustion slag from a

coal-fired power plant in the city of Nantong near the Changjiang River, as well as a sample of vehicle emissions from the city of Nantong. 2.2 Analysis of the test indices The test indices included PAHs, grain size distribution, total organic carbon (TOC), and the stable carbon and hydrogen isotopes of the PAHs. Samples were analyzed for sixteen PAHs, containing naphthane (Nap), acenaphthylene (Acy), acenaphthene (Ace), fluorene (Flo), phenanthrene (Phe), anthracene (Ant), fluoranthene (Fla), pyrene (Pyr), benzo[a]anthracene (BaA), chrysene (Chr), benzo[b]fluoracene

(BbF),

benzo[k]fluoracene

(BkF),

benzo[a]pyrene

(BaP),

indeno[1,2,3-cd]pyrene (IcdP), dibenzo[a,h]anthracene (DahA) and benzo[g, h, i]perylene (BghiP). The PAH analysis procedure was carried out according to the procedure described by Zhang et al. (2013). Briefly, homogenized samples were freeze-dried and ground. Approximately 3-5 g of the sample was spiked with a mixture of recovery standards of two deuterated PAHs (phenanthrene-d10 and perylene-d12). The samples were subjected to ultrasonication-assisted extraction with a dichloromethane-methanol (3:7, v:v) mixture. The extract was concentrated by vacuum evaporation, and then transferred into a mini vial. Samples were analyzed by a Trace GC 2000 (Thermo, USA) capillary gas chromatograph coupled to an ion-trap mass spectrometer Trace-PolarisQ MS (Thermo, USA) using electronic ionization (70 eV). Further details on sample extraction, cleanup, instrumental analysis, and quality control procedures are included in the Text S1of the Supporting

Information. Thirty-six sediment subsamples and two samples from Nantong city near the Changjiang River were analyzed for dual isotopes of PAHs. Methods for the extraction, purification, and instrumental analysis for PAH compound specific isotope measurement have been described previously (Bosch et al., 2015; Jautzy et al., 2015; Kim et al., 2008). Briefly, sediments (about 20 g) dried chemically by mixing with anhydrous sodium sulfate were extracted on ASE (Dionex, USA) system using dichloromethane. Concentrated extracts were separated into aliphatic and aromatic fractions

using

aluminum/silica

column

chromatography.

Gel-permeation

chromatography was applied to remove high molecular weight compounds from the samples. Samples were concentrated to a final volume of 1 mL for further isotope analyses. Because the abundances of some individual PAHs in sediment samples were quite low and overlapping, isotopes of individual PAHs were taken account as follows: (1) Phe+Ant; (2) Fla; (3) Pyr; (4) BaA + Chr; (5) BbF + BkF; (6) BaP; and (7) IcdP +DaA+BghiP. Further information on these cleanup procedures is provided in the Supporting Information (Text S1). It was reported that no significant isotopic fractionation occurred for the compounds during the experimental procedures. Results in this study on isotope fractionation during laboratory procedures are included in Table S2 of the Supporting Information, implying that control experiments did not show isotope fractionation. The δ13C and δ2H isotope ratio determinations were measured by gas chromatography-isotope ratio mass spectrometry (GC-IRMS). δ13C analyses were

performed using a Thermo Quest Finnigan Delta Plus XL IRMS coupled to an Agilent 6890 GC via a Thermo Quest Finnigan GC Combustion III interface. δ2H determinations were performed using a Thermo DeltaV Plus IRMS coupled to a Trace GC via a GC Isolink and ConfloIV interface. The reported isotopic results, expressed in the per mil (‰) deviation of the isotope ratio from the standards Vienna Peedee belemnite (VPDB) and Vienna standard mean ocean water (VSMOW) for C and H, respectively, represent the arithmetic means of triplicate analyses. The quality control (QC) standards were run bracketing all sets of analyses, and at least every three samples. The accuracies of the sample measurements was estimated as the standard deviation (SD) between the real and the calculated values of standards and were all within 0.6 ‰ for δ13C and 7 ‰ for δ2H. The total errors of these analysis are reported as the largest uncertainty associated with either precision or accuracy for each sample. Further information on the instrumental analysis and quality procedures is provided in Text S1 (Experimental section) of the Supporting Information. Experimental procedures of sediment grains size and TOC were conducted according to Zhang et al. (2018). Further information on these cleanup procedures is provided in the Supporting materials (Text S1). 2.3 Statistical methods and mapping Correlation analyses were performed using SPSS 17.0 for Windows. A p value of <0.05 indicated statistical significance. Spatial distribution maps were produced using Surfer 8.0 (Golden Software Inc., Colorado), and the kriging method of gridding

was used for the data interpolation.

3. Results 3.1 Sediment grain size distribution and total organic carbon The clay content of the collected surface sediments ranges from 7.82 to 42.91%, with an average of 26.65% (Fig. S1). The general spatial distribution of the sediment grain size in the ECS shows several mud deposits, which composed primarily of silt and clay in the subaqueous delta of the Changjiang River and the inner shelf of the ECS, i.e., the Zhe-Min coastal mud area. In contrast, lots of coarse sediment is found in the outer shelf. These results are consistent with the previous studies (Liu et al., 2007; Lin et al., 2013; Chen et al., 2018; Wang et al., 2017). The TOC in the ECS ranges from 0.11 to 0.64% of the sediments, and the mean is 0.36% (Fig. S1). The TOC distribution also shows an increasing trend from the estuary to the southeast coastal mud area. There is also a positive correlation between TOC contents and the clay constituents (r2 = 0.65, p<0.01, n = 53), suggesting that the TOC could be mainly dependent on the sediment grain size (Lin et al., 2013). 3.2 Concentrations and isotope compositions of the PAHs In the following, the PAH weights are expressed as dry weights. The total concentration of the total PAHs in the surface sediments varies from 24.73 ± 8.51 ng g-1 to 420.85 ± 35.23 ng g-1, with an average value of 151.68 ± 18.56 ng g-1 (Fig. 2a). In addition, the δ13C values of the PAH in the sediment ranges between −26.47 ±

0.11‰ and −22.16 ± 0.16‰, with a mean of −24.51 ± 0.15‰ (Fig. 2b). The results for δ13C values of individual PAH compounds are shown in Figure S2. Low molecular weight PAHs in sediment were relative enriched in 13C, for example, the δ13C of the PAH group Phe+An ranges between −26.56 ± 0.14‰ and −21.13± 0.112‰ (−23.88 ± 0.12‰ on average). Whereas, high molecular weight PAHs in sediment showed depletion in

13C,

for example, the δ13C of group BbF+BkF ranges between −28.62 ±

0.14‰ to −23.10 ± 0.08‰ (−25.39 ± 0.10‰). In addition, the δ2H value of the PAHs ranges between −107.21 ± 13.21‰ and −66.45 ± 1.74‰ (−87.99 ± 4.31‰ on average) (Fig. 2c).

4. Discussion 4.1 The distribution, composition, and diagnostic ratios of the PAHs in the surface sediments of the ECS As seen in Figure 2a, the PAH concentrations are relatively higher near the estuary of the Changjiang River and the inner shelf than in the outer shelf of the ECS. This result is comparable to the previous studies in the ECS (Lin et al., 2013; Yu et al., 2015; Wang et al., 2016; Wang et al., 2017; Chen et al., 2018). A comparison of PAH concentrations with the literature data from other large estuarine-coastal systems (Table S3) indicates that PAH concentrations in this study area are at the low and moderate levels of the global range, but it still contains higher than those of James Ross Island and Antarctica (Table S3). However, the observed PAH levels in the ECS are lower than in highly urbanized estuaries, such as the Pearl River Estuary, Nile

Estuary, Yellow River Estuary, as well as Boston Harbor (Table S3). In the ECS, high PAH concentrations are found in the subaqueous delta and the Zhe-Min coastal mud area. It is suggested that the PAHs in the ECS are a direct influence of river input from the Changjiang River, because the middle and lower reaches of the Changjiang River are some of the most developed and populated regions of China. In addition, there are lots of atmospheric PAHs from coal burned for residential and industrial purposes in eastern China, which may be also attributed to high PAH concentrations in the coastal area. However, in our study, relatively low PAH concentrations are measured at the estuary of the Changjiang River (Fig. 2a). It is explained possibly that large accumulation of fluvial terrigenous sediments from Changjiang River may dilute the pollutants at the estuary, which is consistent with the results reported in previous studies (Guo et al., 2006; Li et al., 2012; Lin et al., 2013; Li et al., 2016; Liu et al., 2012b; Wang et al., 2016, 2017) Some previous studies have revealed that sediment grain size distributions and TOC content play an important role in the control of PAH distribution patterns (Wang et al., 2006; Oros et al., 2007; Liu et al., 2008; Nascimento et al., 2017). Positive correlations (r2=0.53, p<0.01, n=53) between the PAHs and clay content and between the PAHs and TOC content (r2=0.49, p<0.01, n=53) in the sediments of the ECS may verify the influence of TOC and sediment grain size on the PAH distribution in our study. Nevertheless, this result is contradictory to some reported studies, in which no significant correlations between these variables were found (Lin et al., 2013; Yu et al., 2015; Wang et al., 2016; Wang et al., 2017; Chen et al., 2018;

Mostafa et al., 2009). It is indicated that the distribution and fate of PAHs are controlled by local complicated environmental factors, e.g. sediment sources, hydrodynamic conditions, and TOC sources. PAHs are generally grouped according to their source characteristics into low-molecular-weight (LMW) PAHs (LMW with 2–3 rings, i.e., Nap, Acy, Ace, Flo, Phe, Ant, and Fla) and high molecular weight (HMW) PAHs (HMW with 4–6 rings, i.e. Pyr, Chr, BbF, Bkf, BaP, IcdP, DahA, and BghiP). LMW PAH concentrations in the ECS range from 9.21 to 246.38 ng/g, with a mean of 72.73 ng/g (Fig. S3a). The HMW PAHs vary between 4.82 and 290.39 ng/g, with a mean of 78.95 ng/g (Fig. S3b). Previous studies have reported that LMW PAHs are considered to be originated from petrogenic sources, and HMW PAHs are generated from pyrogenic sources such as biomass burning, fossil fuel combustion, and vehicles emissions (Yunker et al., 2002; Guo et al., 2006). HMW PAHs were mainly deposited in the estuary and the inner shelf, and tended to decrease with increasing distance from the coast. This result can be implied that the PAHs in the estuary and inner shelf are mainly originated from riverine inputs, discharging pyrogenic sources from significant anthropogenic contributions in the catchment of the Changjiang River. Then these PAHs are prone to rapid deposition and retention close to the source regions. The relative high level of LMW PAHs in few samples from the estuary and northern Zhe-Min coastal mud area may have also been caused by oil leakages due to shipping activities. Moreover, the diagnostic ratios (e.g. Fluo/(Fluo+Pyr), InP/(InP+BghiP) and BaA/(BaA+Chr)) (Yunker et al., 2002, 2003) also confirm that mixtures of petroleum, coal, and

biomass combustion are likely to be the main sources of PAHs in most of the sediment samples, while the PAHs in some samples originate from petroleum sources (Text S2, Fig. S3c, S3d). As discussed above, molecular ratios may be applied to assign PAH sources in the ECS based on source-specific diagnostic ratios (Yunker et al., 2002). However, the molecular diagnostic ratios and compound compositions may be quite different from the original sources compared with fingerprinting techniques of CSIA,

experiencing chemical and biological alterations. It is difficult

to quantify and identify the origins of the PAHs using the molecular diagnostic ratios. Thus, the results of this study suggest that the CSIA of the PAH pollutants can be a useful tool to decipher the origins of complex mixtures of PAHs in the marginal sea, e.g. the ECS. 4.2 Carbon and hydrogen isotope compositions of the PAHs in the sediment of the ECS Considering the difficulties in achieving source assignment of PAHs, we used compound-specific stable carbon and hydrogen isotopes to apportion the sources. Figure 2b and Table S4 show the δ13C values of the PAHs in the ECS, ranging from −26.47 ± 0.11‰ to −22.16 ± 0.16‰. In addition, it seems that some δ13C variations can be observed between the different PAH compounds in the sediments, which suggests relatively nonhomogeneous sources for the PAHs in the ECS. The highest δ13C value is found in the individual PAH compound BaP, with −21.11 ± 0.11‰ (Fig. S2), and the PAH group BbF+BkF has the lowest δ13C value of −28.62 ± 0.14‰ (Fig. S2).

During

high-temperature

processes

(e.g.

fossil

fuel

combustion),

polyaromatization reactions can result in the loss of

13C,

raising the possibility of

further δ13C depletion (Wang et al., 2004). Generally, the δ13C of the total PAHs presents an increasing tendency from the estuary of the Changjiang River and the inner shelf to the outer shelf, which is consistent with the individual HMW PAH compounds, e.g., BaA+Chr, BbF+BkF, BaP, and IcdP+DaA+BghiP (Fig. S2). Moreover, the δ13C of the individual LMW PAH compounds (e.g. Phe+An) shows an interesting pattern, in which the δ13C values at the estuary and the outer shelf are relatively higher than ones at the middle shelf (Fig. S2). These spatial distributions of δ13C may be related to the hydrodynamic and sedimentary conditions in the ECS. Most sediment-associated PAHs from the Changjiang River are trapped and deposited in the estuary and inner shelf owing to the blocking effect of the northward Taiwan warm Current, and few suspended sediment can be transported in the outer shelf (Liu et al., 2007). In addition, these patterns in the ECS may resulted from the different properties and characteristics of the HMW and LMW PAHs. HMW PAHs are easily absorbed onto sediments (Berrojalbiz et al., 2011; Lin et al., 2013; Wang et al., 2016) and eventually deposited at the coastal areas, inducing that the δ13C is relatively higher than that at the outer shelf. Whereas, LMW PAHs tend to travel further compared with HMW-PAHs, and the δ13C values of LMW PAHs always are higher than ones of HMW PAHs (Gao et al., 2018; Wang et al., 2004), resulting in the relative high δ13C values in the outer shelf. In addition, it is noted that there is a positive correlation between the δ13C of the individual PAH compounds Fla and Pyr (r2 = 0.74, n=36, p<0.01; Fig. S4). Positive correlations (r2 = 0.74, n=36, p<0.01)

between the δ13C of IcdP+DaA+BghiP and the δ13C of BaP or the δ13C of BbF+BkF (r2 = 0.45, n=36, p<0.01) are also found in the ECS (Fig. S4). It is suggested that these individual PAH compounds can be attributed to homogeneous sources. Previous studies have reported that the HMW PAHs, such as Fla, Pyr, Chr, BbF, Bkf, BaP, IcdP, DaA, and BghiP, are considered to generate primarily from high-temperature combustion (Yunker et al., 2002). This could explain the correlations among the δ13C values of some individual PAH compounds. The isotope values of the environmental samples in the reported studies are summarized in Table S5. Overall, the δ13C values of the PAHs recorded in this study are comparable to those observed in aerosols from Chinese cities (Okuda et al., 2002) and coal combustion (McRae et al., 2005; Bosch et al, 2015; Jautzy et al., 2015; Yan et al., 2006; Chen et al., 2012; Kawashima and Haneishi, 2012), as well as liquid fossil fuel combustion, including gasoline and diesel soot (McRae et al., 2000; Okuda et al., 2002; Sun et al., 2003; Wang et al., 2004; Bosch et al, 2015; Jautzy et al., 2015; Holman and Grice, 2018). The δ13C values of PAHs in sediments of the ECS, however, are generally higher than the values reported for biomass (e.g. grass, straw, and wood) sources (Bosch et al, 2015; Jautzy et al., 2015; Guillon et al., 2012; Ahad et al., 2015) and petrogenic sources (O’Malley et al., 1994; Yan et al., 2006; Kim et al., 2008; Bosch et al, 2015). In addition, the isotopic signatures in the ECS are in distinct contrast with those of methane (Yan et al., 2006). The δ2H values of the PAHs in the ECS range between −107.21 ± 13.21‰ and −66.45 ± 1.74‰ (−87.99 ±4.31‰ on average) (Fig. 2c; Table S4). Comparing with δ13C, there is relative large variability in

the pattern of δ2H in the ECS. It is demonstrated that C-H bonds are weaker than C-C bonds (Sun et al., 2003; Gao et al., 2018; Bosch et al, 2015), resulting in the H isotopic signatures show a higher variability in sediment of the ECS. Even though δ2H values in the reported literature are currently limited, the δ2H values obtained in this study are comparable to those of biomass combustion, petroleum and liquid fossil fuel combustion, and coal combustion (Bosch et al, 2015; Jautzy et al., 2015). Considering limited researches of typical sources on CSIA of PAHs, we also analyzed δ13C and δ2H of two typical source samples at Nantong City near the Changjiang River, in which one is a sample of coal combustion slag from a coal-fired power plant, another is a sample of vehicle emissions. δ13C and δ2H values of coal combustion were −24.19 ± 0.15‰ and −119.25± 18.32‰, with −23.13 ± 0.22‰ and −59.06 ± 6.12‰ of the vehicle emissions, respectively. Taking all the above into account, the isotopic signatures of the PAHs in the ECS are similar to those derived from biomass combustion, coal combustion, and liquid fossil fuel combustion (Table S6, Fig. 3), implying that these environmental sources seem to be responsible for the PAH pollution in the ECS. The contributions of these environmental sources are discussed in detail in Section 4.3. Some studies have reported that the carbon isotopic signatures of individual PAHs

seemed

to

be

conservative

though

evaporation,

water

flowing,

photodecomposition, biodegradation, and decomposition of organic matter (O’Malley et al., 1994, 1996; Mazeas et al., 2002). With regard to biodegradation, significant isotope fractionation of the PAHs resulting in

13C-enrichment

of the

residues has thus far not been reported for δ13C values (Mazeas et al., 2002). While, carbon and hydrogen isotopes of 2-ringed naphthalene could behave fractionation in controlled laboratory experiments (Morasch et al., 2002; Bergmann et al., 2011). Furthermore, some studies have reported that the BaA generally tends to be depleted in the most photoreactive components with compared with Chr, implying degradation after long-range transport (Tolosa et al., 1996). Thus, the ratio of BaA/Chry can indicate the photochemical degradation (Tolosa et al., 1996). In our study, there is no correlation between the diagnostic ratios for photochemical degradation (BaA/Chry) and their respective δ13C values (Fig. S5). However, if we assume that PAH degradation under aerobic conditions may lead to hydrogen isotope shifts, such hydrogen isotopic fractionations will be accompanied by shifts of δ13C values (Bosch et al, 2015; Jautzy et al., 2015; Bergmann et al., 2011). It is worth-noted here that no correlation among carbon and hydrogen isotopes can be observed in the sediment of the ECS. Previous studies reported that the organic matter has inhibited PAHs biodegradation within the sediment (Bergmann et al., 2011). Thus, the relatively high TOC content measured in the sediment of the ECS may weaken biodegradation of PAHs, resulting in no correlation between the δ13C and δ2H values of PAHs. As a result, it is suggested that photodegradation has not significantly fractionated the hydrogen isotopes recorded in this study. Therefore, in accordance with this analysis, δ13C and δ2H fractionation of the PAHs during atmospheric transport is likely insignificant. The variation in the δ13C and δ2H values observed in the surface sediment of the ECS is explained bysource changes, rather

than microbial or photochemical fractionation during degradation processes. Therefore, the dual isotopic signatures can be used to identify PAH sources in the ECS. 4.3 Source apportionment of PAHs based on carbon and hydrogen isotope compositions In contrast to their δ13C values, only a few source δ2H values have been reported in the previous literatures (Sun et al., 2003; Bosch et al, 2015; Jautzy et al., 2015). Therefore, in the future, there is the need to better characterize the hydrogen isotopic signatures of the primary sources of PAHs. Although δ2H values are currently limited in the literature, the simultaneous use of δ13C and δ2H provides the possibility of greater differentiation, and allows to apportion quantitatively the relative contributions of the different source classes to the PAH pollution. The isotope signatures of the different PAHs were applied in an isotopic mass-balance source apportionment model to discriminate four potential sources of PAHs: biomass combustion, liquid fossil fuel combustion (e.g., gasoline and diesel soot), coal combustion, and petrogenic sources (e.g. crude oil seeps, oil spills, and leakage of crankcase and lubrication oil), on the basis of two criteria: 1) they envelop most of the PAHs emission in this area (Morasch et al., 2002; Bergmann et al., 2011; Bosch et al, 2015; Jautzy et al., 2015); and 2) they are discriminated by the δ13C and δ2H isotopic signatures. The source-specific isotope values (end-members) are summarized in Table S6 from the previous studies, in which the isotopic values of the PAHs are used. These end-members are associated with a relatively large range of

variation, especially in the δ2H dimension from −107.21‰ to −66.45‰. It is illustrated in some studies that such variability could affect the precision of the source apportionment, but also the estimated mean values of the source fractions (Morasch et al., 2002; Bergmann et al., 2011; Andersson et al., 2011). Accounting for this variability, a Bayesian Markov chain Monte Carlo (MCMC) approach was implemented (Morasch et al., 2002; Parnell et al, 2010; Bergmann et al., 2011; Bosch et al, 2015), in which the end-member distributions are modeled as normal distributions. This model as a source apportionment approach requires a preliminary step in order to validate its application, which can be carried out by plotting the samples’ and sources’ average values in a dual isotopic plot. And this step will characterize a unique mixing polygon and the relative locations of the samples to this polygon. As recommended by previous studies (Phillips and Gregg, 2003; Parnell et al, 2010; Smith et al., 2013), all the possible mixing polygons in accordance with the isotopic signatures of the selected potential sources were simulated in this study (Fig. S6), which verified the application of this mixing model based on an R-based model (Parnell et al, 2010; Smith et al., 2013; Bosch et al, 2015; Jautzy et al., 2015). This simulation allowed us to test the ability of each mixing polygon to establish a mass balance. The MCMC approach effectively samples the fractional source space while satisfying the mass-balance criterion and simultaneously considering the end-member variability. The Bayesian-based mixing model was thus applied with 200000 iterations to the four sources’ isotopic distributions, with a burn-in (initial search phase) of 10000, and a data thinning of 10 (Parnell et al, 2010; Smith et al.,

2013; Bosch et al, 2015; Jautzy et al., 2015). Most of the sediment samples are comprised within the 80% mixing region (Fig. S6). It is referred that the model can explain the sources’ contributions, lending confidence to the source discrimination for the ECS (Parnell et al, 2010; Smith et al., 2013; Bosch et al, 2015; Jautzy et al., 2015). The results show that the source with the highest contribution is coal combustion, ranging from 26 to 70% (42 ± 5%, Fig. 4). Contributions from liquid fossil fuel combustion (e.g., gasoline and diesel soot) can also be observed for all the samples (23±6%, Fig. 4). Biomass sources contribute an average of 21 ± 5% of the PAHs in the surface sediments of the ECS. The combustion of petrogenic sources is the least important source of PAHs in the surface sediment of the ECS, with an average of 11 ± 6%. Spatially different sources of PAHs in the ECS are highlighted in Figure 4. Some sediment samples with the highest PAH concentrations from the estuary of the Changjiang River and the inner shelf have higher coal-related contributions (an average of 47 ± 5%, Fig. 4), while the average contributions of liquid fossil fuel combustion, biomass combustion, and petrogenic sources are 25 ±7%, 21 ±8%, and 9 ± 5%, respectively (Fig. 4). Compared to the coastal sea, the proportion of PAHs from petrogenic sources shows an increase in the outer shelf of the ECS (16 ± 7%) (Fig. 4). In contrast, the contributions from the other sources in this area seem to be slightly lower than in the coastal area, with an average of 41 ± 5% for coal combustion, 20 ± 5% for biomass combustion, and 17 ± 6% for liquid fossil fuel combustion, respectively.

4.4 Sources of the PAHs in the ECS In general, the distribution of the PAHs in the ECS may be significantly affected by the variable lifestyles and economic development in the area (Soclo et al., 2000; Liu et al., 2012a). China still rely mainly on coal for energy, and coal consumption reached 4490 Mt in 2017, accounting for over 60% of the total energy consumption (followed by petroleum at over 18%) (NBSC, 2018), representing approximately 37% of the global consumption (Chen and Xu, 2010). The usage of coal in China ranges from large power plants and industries to individual domestic households, and thus coal combustion has become the largest contributor of environmental pollution in China (Liu and Diamond, 2005; Chan and Yao, 2008). In addition, exhaust gases produced from lot of industries are emitted into the upper air, where most pollutants could be transported over long distances. Consequently, these PAHs in the upper air can be absorbed by fine particles and are then deposited into the ocean through dry and wet precipitation (Chen et al., 2016). This situation may cause the high contribution of the coal combustion source in this study. Moreover, the PAHs in the surface samples collected from the ECS also mainly originate from vehicular emissions. There are two possible origins of the traffic-related PAHs in the sediment of the ECS. The distribution patterns of the PAHs in the ECS are mainly controlled by direct riverine inputs and surface runoff (Lin et al., 2013; Hu et al., 2012). In recent decades, a rapid increase in vehicles has a great pressure on the environment, raising more attentions in China (Riley, 2002). Some

cities in the economic zone of the Changjiang River catchment has over 2 million cars, especially megacities (e.g. Shanghai, Suzhou, Hangzhou, and Nanjing) in the Changjiang River Delta

(NBSC, 2016). Therefore, the other sources of PAHs in the

riverine inputs and surface runoff are vehicular emissions. In addition, pyrogenic PAHs in the marine environment may also derive from vessel emissions (Boitsov et al., 2009). The ECS is an important fishing ground, as well as an important shipping traffic route, so emissions from fishing boats and cargo vessels may further exacerbate the PAHs pollution. In addition, biomass combustion is commonly used for cooking and heating in rural China, owing to a traditional fuel (Liu et al., 2012a, 2012b). The emission from biomass combustion has been reported as accounting for over 65% of the total emission of PAHs from the major combustion sources (biomass, domestic coal, industrial coal, coke industry, transport oil, and other oil) (Liu et al., 2012a, 2012b). Previous studies have also reported that biomass combustion releases more PAHs than the combustion of petroleum or natural gas (Yan et al., 2006). Therefore, it is believed that biomass combustion is another important PAHs emission source in the ECS (Li et al., 2012; Liu et al., 2012b). Furthermore, petrogenic sources have also been identified as a potential pollution source in the ECS. The estuary of the Changjiang River is an important shipping center, and there are some important fishing harbors along the Zhe-Min coast. Shipping transportations could therefore release some oil into the coastal waters. Compared with the coastal areas, petroleum hydrocarbons in the outer shelf can be attributed to crude oil leaks from

the oilfields. It should be emphasized that the PAH sources of coal combustion, biomass combustion, and liquid fossil fuel combustion show a decreasing trend with distance from the coast, while the contribution of petrogenic sources increases. The PAHs pollutants from these sources are primarily controlled by direct riverine inputs and surface runoff (Lin et al., 2013; Hu et al., 2013), whereas only a small amount of riverine input is transported to the outer shelf (Liu et al., 2007). Thus, the contributions from coal combustion, biomass combustion, and liquid fossil fuel combustion are lower than in the coastal area, especially liquid fossil fuel combustion. In addition, due to atmospheric physical processes and the physicochemical properties of PAHs, the liquid fossil fuel combustion source is closer to the Earth’s surface, resulting in the fact that it cannot easily be transported to the upper atmosphere and consequently over long distances (Vitzthum et al., 2011). Therefore, the amount of liquid fossil fuel combustion source could be less in the outer shelf of the ECS.

5. Conclusions. In this study, we have presented the carbon and hydrogen isotopes of the PAHs in the surface sediment of the ECS, and then quantitatively identified PAH source apportionment, based on a dual-CSIA approach. The results have shown the spatial variabilities of δ13C and δ2H values of the PAHs in the ECS, implying that different

environmental sources of PAHs seem to be responsible for the PAHs pollution in marginal sea. The usage of dual-CSIA can figure out the source apportionment by identifying the complex mixture of sources that contribute to the PAHs in surface sediments. The results indicated that coal combustion is the predominant source of PAHs in the ECS, but the other sources (i.e., biomass combustion, liquid fossil fuel combustion, and petrogenic sources) were also identified in the ECS. Overall, these results from the dual-CSIA are also consistent with ones of PAH diagnostic ratios as well as the findings of previous studies (Li et al., 2012; Liu et al., 2012a, 2012b; Lin et al., 2013; Wang et al., 2016, 2017). The present study demonstrates that the dual isotope-characterization of the PAHs in the surface sediments of the ECS is viable, and that this information can provide more detailed and valid source apportionments. However, the reported literature on the isotopic signatures of PAHs in coastal areas and marginal seas is still limited. It is hoping that such work will promote the supplement of the existing source database.

Notes The authors declare no competing financial interest.

Acknowledgments This work was financed by the National Natural Science Foundation of China

(91958108, 41830539, 41406055, 41506106, 41230959, 41476043), the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA11030104), the project

of

Global

Change

and

Air-Sea

Interaction

(GASI-GEOGE-06-02,

GASI-GEOGE-04), International Postdoctoral Exchange Fellowship Program (20160073), Natural Science Foundation of Jiangsu Province (BK20170451, BE2016701), Six talent peaks project in Jiangsu Province (JNHB-143), “521”talent peaks project in Lianyungang City (LYG52105-2018044), Project of Innovation for Undergraduate in Jiangsu Province (SD201911641107001, SZ201911641107002). We are also grateful to “Qing Lan Project” of Jiangsu Provincial Department of Education, “Sea Swallow Project” of Lianyungang City and Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).

References Ahad, J. M. E., Jautzy, J., Cumming, B. F., Das, B., Kingsbury, M., Laird, K. R., Sanei, H., 2015. Sources of polycyclic aromatic hydrocarbons (PAHs) to northwestern Saskatchewan lakes east of the Athabasca oil sands. Org. Geochem. 80, 35-45. Andersson, A. A., 2011. Systematic examination of a random sampling strategy for source apportionment calculations. Sci. Total Environ. 412-413, 232-238. Baumard, P., Budzinski, H., Michon, Q., Garrigues, P., Burgeot, T., Bellocq, J., 1998. Origin and bioavailability of PAHs in the Mediterranean Sea from mussel and sediment records. Estuar. Coast. Shelf S. 47(1), 77-90. Bergmann, F. D., Abu Laban, N. M. F. H., Meyer, A. H., Elsner, M., Meckenstock, R. U.,

2011. Dual (C, H) isotope fractionation in anaerobic low molecular weight (poly) aromatic hydrocarbon (PAH) degradation: Potential for field studies and mechanistic implications. Environ. Sci. Technol. 45 (16), 6947-6953. Berrojalbiz, N., Dashes, J., Ojeda, M., Valle, M., Castro-Jimenez, J., Wollgast, J., Ghiani, M., Hanke, G., Zaldivar, J., 2011. Biogeochemical and physical controls on concentrations of polycyclic aromatic hydrocarbons in water and plankton of the Mediterranean and Black seas. Global Biogeochem. Cycles, 25, GB4003. Boitsov, S., Jensen, H.K.B., Klungsoyr, J., 2009. Natural background and anthropogenic inputs of polycyclic aromatic hydrocarbons (PAH) in sediments of South-Western Barents Sea. Mar. Environ. Res. 68, 236-245. Bosch, C., Andersson, A., Krusa, M., Bandh, C., Hovorkova, I., Klanova, J., 2015. Source apportionment of polycyclic aromatic hydrocarbons in central European soils with compound-specific triple isotopes (δ13C, Δ14C and δ2H). Environ. Sci. Technol. 49(13), 7657-65. Bostrom, C.E., Gerde, P., Hanberg, A., Jernstrom, B., Johansson, C., Kyrklund, T., 2002. Cancer risk assessment, indicators, and guidelines for polycyclic aromatic hydrocarbons in the ambient air. Environ. Health Perspec. 110, 451-488. Budzinski, H., Bellocq, J., Pierard, C., Garrigues, P., 1997. Evaluation of sediment contamination by polycyclic aromatic hydrocarbons in the Gironde estuary. Mar. Chem. 58, 85-97. Chan, C. K., Yao, X. H., 2008. Air Pollution in Mega Cities in China. Atmos. Environ. 42, 1-42.

Chen, W. Y., Xu, R. N., 2010. Clean coal technology development in China. Energy Policy. 38, 2123-2130. Chen, X., Liu, X., Liu, M., Yang, Y., Wu, S., Wang, C., 2018. Molecular characterization of PAHs based on land use analysis and multivariate source apportionment in multiple phases of the Yangtze estuary, China. Environ Sci Process Impacts 20(3), 531-543. Chen, Y., Lin, T., Tang, J., Xie, Z., Tian, C., Li, J., Zhang, G., 2016. Exchange of polycyclic aromatic hydrocarbons across the air-water interface in the Bohai and Yellow Seas. Atmos. Environ. 141, 153-160. Chen, Y. J., Cai, W. W., Huang, G. P., Li, J., Zhang, G., 2012. Stable carbon isotope of black carbon from typical emission sources in China. Environ. Sci. 33, 673-678 (in Chinese). Galarneau, E., 2008. Source specificity and atmospheric processing of airborne pahs: implications for source apportionment. Atmos. Environ. 42, 8139-8149. Gao, P., Li, H., Wilson, C., Townsend, T., Xiang, P., Liu, Y., Ma, L., 2018. Source identification of PAHs in soils based on stable carbon isotopic signatures. Crit Rev Env Sci Tec, 48(13-15), 923-948. Ghosal, D., Ghosh S., Tapan K., Ahn, D.Y., 2015. Current State of Knowledge in Microbial Degradation of Polycyclic Aromatic Hydrocarbons (PAHs): A Review. Front. Microbio. 7(386), 1-27. Grice, K., Lu, H., Atahan, P., Hallmann, C., Asif, M., Greenwood, P.F., Tulipani, S., Maslen, E., Williford, K.H., Dodson, J., 2009. New insights into the origin of

perlyene in geological samples. Geochim. Cosmochim. Acta 73, 6531-6543. Guo, Z., Lin, T., Zhang, G., Yang, Z., Fang, M., 2006. High-resolution depositional records of polycyclic aromatic hydrocarbons in the central continental shelf mud. Environ. Sci. Technol, 40(17), 5304-5311. Guillon, A., Le Menach, K., Flaud, P.M., Marchand, N., Budzinski, H., Villenave, E., 2012. Chemical characterization and stable carbon isotopic composition of particulate polycyclic aromatic hydrocarbons issued from combustion of 10 Mediterranean woods. Atmos. Chem. Phys. Discuss. 12, 20631-20671. Holman, A.I., Grice, K., 2018. δ13C of aromatic compounds in sediments, oils and atmospheric emissions: A review. Org. Geochem. 123, 27-37. Hu, L., Shi, X., Yu, Z., Lin, T., Wang, H., Ma, D., Guo, Z., Yang, Z., 2012. Distribution of sedimentary organic matter in estuarine-inner shelf regions of the East China Sea: Implications for hydrodynamic forces and anthropogenic impact. Mar. Chem. 142, 29-40. Jautzy, J. J., Ahad, J. M. E., Gobeil, C., Smirnoff, A., Barst, B. D., Savard, M. M., 2015. Isotopic evidence for oil sands petroleum coke in the Peace-Athabasca Delta. Environ. Sci. Technol. 49(20), 12062-70. Kawashima, H., Haneishi, Y., 2012. Effects of combustion emissions from the Eurasian continent in winter on seasonal δ13C of elemental carbon in aerosols in Japan. Atmos. Environ. 46, 568-579. Kim, M., Kennicutt, M. C., Qian, Y., 2008. Source characterization using compound composition and stable carbon isotope ratio of PAHs in sediments from lakes,

harbor, and shipping waterway. Sci. Total Environ. 389 (2-3), 367-377. Li, B.H., Feng, C.H., Li, X., Chen, Y.X., Niu, J. F., Shen, Z.Y., 2012. Spatial distribution and source apportionment of PAHs in surficial sediments of the Yangtze Estuary, China. Mar. Pollut. Bull. 64, 636-643. 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, 566-567, 1387-1397. Lin, T., Hu, L., Guo, Z., Zhang, G., Yang, Z., 2013. Deposition fluxes and fate of polycyclic aromatic hydrocarbons in the Yangtze River estuarine-inner shelf in the East China Sea. Global Biogeochem. Cyc. 27, 77-87. Liu, J., Diamond, J., 2005. China’s environment in a globalizing world. Nature. 435, 1179-1186. Liu, J.P., Xu, K.H., Li, A.E.A., Milliman, J.D., Velozzi, D.M., Xiao, S.B., Yang, Z.S., 2007. Flux and fate of Yangtze River sediment delivered to the East China Sea. Geomorphology 85, 208-224. Liu, L. Y., Wang, J. Z., Wei, G. L., Guan, Y. F., Wong, C. S., Zeng, E. Y., 2012a. Sediment records of polycyclic aromatic hydrocarbons (PAHs) in the continental shelf of China: Implications for evolving anthropogenic impacts. Environ. Sci. Technol. 46(12), 6497-6504. Liu, L. Y., Wang, J. Z., Wei, G. L., Guan, Y. F., Wong, C. S., Zeng, E. Y., 2012b. Polycyclic aromatic hydrocarbons (PAHs) in continental shelf sediment of China:

Implications for anthropogenic influences on coastal marine environment. Environ. Poll. 167(12), 155-162. Liu, Y., Chen, L., Jianfu, Z., Qinghui, H., Zhiliang, Z., Hongwen, G., 2008. Distribution and sources of polycyclic aromatic hydrocarbons in surface sediments of rivers and an estuary in Shanghai, China. Environ. Poll. 154, 298-305. Hu, L., Shi, X., Yu, Z., Lin, T., Wang, H., Ma, D., Guo, Z., Yang, Z., 2012. Distribution of sedimentary organic matter in estuarine-inner shelf regions of the East China Sea: Implications for hydrodynamic forces and anthropogenic impact. Mar. Chem. 142, 29-40. Mandalakis, M., Gustafsson, O., Reddy, C. M., Xu, L., 2004. Radiocarbon apportionment of fossil versus biofuel combustion sources of Polycyclic Aromatic Hydrocarbons in the Stockholm Metropolitan Area. Environ. Sci. Technol. 38, 5344-5349. Mazeas, L., Budzinski, H., Raymond, N., 2002. Absence of stable carbon isotope fractionation of saturated and polycyclic aromatic hydrocarbons during aerobic bacterial biodegradation. Org. Geochem. 33 (11), 1259-1272. McRae, C., Sun, C., Snape, C. E., Fallick, A. E., Taylor, D., 1999. δ13C values of coal-derived PAHs from different processes and their application for source apportionment. Org. Geochem. 30, 881-889. McRae, C., Sun, C., McMillan, C. F., Snape, C. E., Fallick, A. E., 2000. Sourcing of fossil fuel-derived PAH in the environment. Polycyclic Aromat. Comp. 20, 97-104. Morasch, B., Richnow, H. H., Schink, B., Vieth, A., Meckenstock, R. U., 2002. Carbon

and hydrogen stable isotope fractionation during aerobic bacterial degradation of aromatic hydrocarbons. Appl. Environ. Microbiol. 68 (10), 5191-5194. Mostafa, A. R., Wade, T. L., Sweet, S. T., Al-Alimi, A.K.A., Barakat, A.O., 2009. Distribution and characteristics of polycyclic aromatic hydrocarbons (PAHs) in sediments of Hadhramout coastal area, Gulf of Aden, Yemen. J. Ma. Sys. 78, 1-8. Nascimento, R. A., De Almeida, M., Escobar, N. C. F., Ferreira, S. L. C., Mortatti, J., Queiroz, A. F. S., 2017. Sources and distribution of polycyclic aromatic hydrocarbons (PAHs) and organic matter in surface sediments of an estuary under petroleum activity influence, Todos os Santos Bay, Brazil. Mar. Pollut. Bull. 119(2), 223-230. National Bureau of Statistics of China (NBSC), 2016. China Economic Yearbook in 2016, Beijing. National Bureau of Statistics of China (NBSC), 2018. China Energy Statistical Yearbook 2018, Beijing. O’Malley, V.P., Abrajano, T.A., Hellou, J., 1994. Determination of the 13C/12C ratios of individual PAH from environmental samples: can PAH sources be apportioned? Org. Geochem. 21, 809-822. O’Malley, V. P., Abrajano, T. A., Hellou. J., 1996. Stable Carbon Isotopic Apportionment of Individual Polycyclic Aromatic Hydrocarbons in St. John’s Harbour, Newfoundland. Environ. Sci. Technol. 30(2), 634-639. Okuda, T., Kumata, H., Naraoka, H., Takada, H., 2002. Origin of atmospheric polycyclic aromatic hydrocarbons (PAHs) in Chinese cities solved by

compound-specific stable carbon isotopic analyses. Org. Geochem. 33, 1737-1745. Oros, D.R., Ross, J.R.M., Spies, R.B., Mumley, T., 2007. Polycyclic aromatic hydrocarbon (PAH) contamination in San Francisco Bay: a 10-year retrospective of monitoring in an urbanized estuary. Environ. Res. 105, 101-118. Parnell, A. C., Inger, R., Bearhop, S., Jackson, A. L., 2010. Source apportionment using stable isotopes: coping with too much variation. PLOS One 5, e9672. Phillips, D. L., Gregg, J. W., 2003. Source partitioning using stable isotopes: coping with too many sources. Oecologia 136 (2), 261-269. Reddy, C. M., Pearson, A., Xu, L., McNichol, A. P., Benner, B. A., Wise, S. A., Klouda, G. A., Currie, L. A., Eglinton, T. I., 2002. Radiocarbon as a tool to apportion the sources of polycyclic aromatic hydrocarbons and black carbon in environmental samples. Environ. Sci. Technol. 36, 1774-1782. Riley, K., 2002. Motor vehicles in China: the impact of demographic and economic changes. Populat. Environ. 23, 479-494. Smith, J. A., Mazumder, D., Suthers, I. M., Taylor, M. D., 2013. To fit or not to fit: Evaluating stable isotope mixing models using simulated mixing polygons. Methods Ecol. Evol. 4 (7), 612-618. Soclo, H. H., Garrigues, P., Ewald, M., 2000. Origin of polycyclic aromatic hydrocarbons (PAHs) in coastal marine sediments: case studies in Cotonou (Benin) and Aquitaine (France) areas. Mar. Pollut. Bull. 40(5), 387-396. Sun, C., Cooper, M., Snape, C. E., 2003. Use of compound-specific δ13C and δD stable

isotope measurements as an aid in the source apportionment of polyaromatic hydrocarbons. Rapid Commun. Mass Spectrom. 17, 2611-2613 Tolosa, I., Bayona, J. M., Albaiges, J., 1996. Aliphatic and Polycyclic Aromatic Hydrocarbons and Sulfur/Oxygen Derivatives in Northwestern Mediterranean Sediments: Spatial and Temporal Variability, Fluxes, and Budgets. Environ. Sci. Technol. 30(8), 2495-2503. Vitzthum, C. D., Grice, K., Ioppolo-Armanios, M., Jones, M., 2011. δ13C and δD of volatile organic compounds in an alumina industry stack emission. Atmos. Environ. 45, 5477-5483. Wakeham, S.G., 1996. Aliphatic and polycyclic aromatic hydrocarbons in Black Sea sediments. Mar. Chem. 53, 187-205. Wang, C., Zou, X., Gao, J., Zhao, Y., Yu, W., Li, Y., 2016. Pollution status of polycyclic aromatic hydrocarbons in surface sediments from the Yangtze River estuary and its adjacent coastal zone. Chemosphere 162, 80-90. Wang, C. L., Zou, X. Q., Zhao, Y. F., Li, Y. L., Song, Q. C., Wang, T., 2017. Distribution pattern and mass budget of sedimentary polycyclic aromatic hydrocarbons in shelf areas of the eastern china marginal seas. J. Geophy. Res. 122, 4990-5004. Wang, X.C., Sun, S., Ma, H.Q., Liu, Y., 2006. Sources and distribution of aliphatic and polyaromatic hydrocarbons in sediments of Jiaozhou Bay, Qingdao, China. Mar. Pollut. Bull. 52, 129-138. Wang, Y., Huang, Y., Huckins, J. N., Petty, J. D., 2004. Compoundspecific carbon and hydrogen isotope analysis of sub-parts per billion level waterborne petroleum

hydrocarbons. Environ. Sci. Technol. 38 (13), 3689-3697. Yan, B., Abrajano, T.A., Bopp, R.F., Benedict, L.A., Chaky, D.A., Perry, E., Song, J., Keane, D.P., 2006. Combined application of δ13C and molecular ratios in sediment cores for PAH source apportionment in the New York/New Jersey harbor complex. Org. Geochem. 37, 674-687. Yu, W. W., Liu, R. M., Wang, J. W., Xu, F., Shen, Z. Y., 2015. Source apportionment of PAHs in surface sediments using positive matrix factorization combined with GIS for the estuarine area of the Yangtze River. China. Chemosphere 134(12), 263-271. Yunker, M.B., Snowdon, L.R., Macdonald, R.W., Smith, J.N., Fowler, M.G., Skibo, D.N., McLaughlin, F.A., Danyushevskaya, A.I., Petrova, V.I., Ivanov, G.I., 1996. Polycyclic aromatic hydrocarbon composition and potential sources for sediment samples from the Beaufort and Barents Seas. Environ. Sci. Technol. 30, 1310-1320. 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. 32, 489-515. Yunker, M. B., Macdonald, R. W., 2003. Alkane and PAHs depositional history, sources and fluxes in sediments from the Fraser River Basin and Strait of Georgia, Canada. Org. Geochem. 34(10), 1429-1454. Zhang, R., Zhang, F., Zhang, T. C., 2013. Sedimentary records of PAHs in a sediment core from tidal flat of Haizhou Bay, China. Sci. Total Environ. 450-451, 280-288.

Zhang, R., Li, T.G., Russell, J., Zhou, Y.R., Zhang, F., Liu, Z.Y., Guan, M.L., Han, Q., 2018. High-resolution reconstruction of historical flood events in the Changjiang River catchment based on geochemical and biomarker records. Chem. Geol. 499, 58-70.

Figure Captions Figure. 1. Study area and sampling stations

Figure. 2. The distribution patterns of PAHs (ng g-1), δ13C (‰) and δ2H (‰) of the PAHs in surface sediments of the East China Sea. (a) PAHs; (b) δ13C; (c) δ2H.

Figure. 3. δ13C and δ2H isotopes of PAHs in surface sediments from the ECS, and simulated isotopic mixing region with four source end members. Data of coal combustion (McRae et al., 2005; Bosch et al, 2015; Jautzy et al., 2015; Yan et al., 2006; Chen et al., 2012; Kawashima and Haneishi, 2012), liquid fossil fuel combustion (McRae et al., 2005; Bosch et al, 2015; Jautzy et al., 2015; Sun et al., 2003; Yan et al., 2006), biomass combustion (Bosch et al, 2015; Jautzy et al., 2015; Ahad et al., 2015) and petroleum leakage (Lin et al., 2013; Bosch et al, 2015; Kim et al., 2008) are from references therein. The colored heat map represents the probabilities of all dual-isotopic signatures that can be explained with the given sources’ isotopic distributions..

Figure. 4. Calculated percentage contributions (%) from (a) coal combustion, (b) liquid fossil combustion, (c) biomass combustion and (d) petrogenic sources for PAHs in surface sediments of the ECS.

Figure. 1. Study area and sampling stations Changjiang River

N1-2

N1-1 N2-1

N2-2

N3-1 N4-1

N3-2

N3-3

N3-4

N4-2

N4-3

N4-4

S2-1 S3-2 S3-1 S4-1

Ou River

S2-2 S2-3

S3-3 S3-4

S4-2 S5-1 S5-2

S6-1

S6-3

S6-2

S6-4

S7-2

S2-4

S3-5

S2-5

N1-

N2-4

N2-3

S1-1 S1-2 S1-3 S1-4 S1-5 S1-6 N4-3

Qiantang River

S7-1

N1-3

N4

N

S1-7

S2-6

S3-6 S4-3 S4-4 S4-5

S5-3 S5-4

S6-5

S7-3

Figure. 2. The distribution patterns of PAHs (ng g-1), δ13C (‰) and δ2H (‰) of the °N PAHs in surface sediments of the ECS. (a) PAHs; (b) δ13C; (c) δ2H.

Surface Sam

Figure. 3. δ13C and δ2H isotopes of PAHs in surface sediments from the ECS, and simulated isotopic mixing region with four source end members. Data of coal combustion10,14,15,42-44, liquid fossil fuel combustion10,14,15,17,41, biomass combustion 14,15,47

and petroleum leakage

8,14,28,32

are from references therein. The colored heat

map represents the probabilities of all dual-isotopic signatures that can be explained

δ2H (‰)

with the given sources’ isotopic distributions.

Petroleum leakage

δ13C (‰)

Biomass combustion

Liquid fossil fuel combustion Coal combustion

Figure. 4. Calculated percentage contributions (%) from (a) coal combustion, (b) liquid fossil combustion, (c) biomass combustion and (d) petrogenic sources for PAHs in surface sediments of the ECS.

a

b

c

d

Changjiang River

Estuary and Inner Shelf

Outer Shelf

East China Sea Coal combustion Liquid fossil combustion Biomass combustion Petrogenic source

WEST PACIFIC

Highlights

 δ13C and δ2H isotope signatures of PAHs in the ECS are detailed reported

 Their isotopic compositions can allow source apportionment of PAHs

 CSIA approach indicate coal combustion as primary source of PAHs in the ECS