Significance of Anthropogenic Factors to Freely Dissolved PolycyclicAromatic Hydrocarbons in Freshwater of ChinaYao Yao,†,# Chun-Li Huang,‡ Ji-Zhong Wang,§ Hong-Gang Ni,∥ Ze-Yu Yang,⊥ Zhi-Yong Huang,‡

Lian-Jun Bao,*,‡ and Eddy Y. Zeng†,‡

†State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou510640, China‡School of Environment, Guangzhou Key Laboratory of Environmental Exposure and Health and Guangdong Key Laboratory ofEnvironmental Pollution and Health, Jinan University, Guangzhou 510632, China§School of Resources and Environmental Engineering, Hefei University of Technology, Hefei, 230009, China∥Shenzhen Key Laboratory of Circular Economy, Shenzhen Graduate School, Peking University, Shenzhen 518055, China⊥Emergencies Science and Technology Section, Environment and Climate Change Canada, Ottawa, K1A0H3, Canada#University of Chinese Academy of Sciences, Beijing, 100049, China

*S Supporting Information

ABSTRACT: Assessment of surface water pollution by organic pollutantsis a top priority in many parts of the world, as it provides criticalinformation for implementing effective measures to ensure drinking watersafety. This is particularly important in China, where insufficient data ofnational scale have been acquired on the occurrence of any organicpollutants in the country’s water bodies. To fill the knowledge gap, weemployed passive samplers to survey polycyclic aromatic hydrocarbons(PAHs) in 42 freshwaters throughout the country. The dissolved Σ24PAHconcentrations ranged from 0.28 to 538 ng L−1, with the highest and lowestvalues obtained in Southern Lake in Wuhan and in the Nam Co Lake inTibet, respectively. Average Σ24PAH concentrations in West, Central, andEast China correlated well with the population densities in these regions.The composition profiles of PAHs showed a mixed PAH source of coalcombustion, fossil fuel combustion, and oil spills. In addition, all dissolved PAH concentrations were below the water guidelinesdeveloped by the U.S. Environmental Protection Agency, the European Union, and the Canadian government, except foranthracene in Southern Lake. Our results also demonstrated the feasibility of establishing a global network of monitoring organicpollutants in the aquatic environment with passive sampling techniques.

■ INTRODUCTION

The United Nations estimates that more than two-thirds of theglobal population will live in cities by 2050.1 Rapid urbanizationhas created overpopulated metropolises, resulting in inadequatewaste treatment and disposal capacity, deterioration of waterquality, shortage of drinking water, and other health issues.2−6

Intensified human activities have aggravated water pollutionbecause organic pollutants of anthropogenic origin can depositin marine and freshwater systems through effluent discharge,atmospheric fallout, surface runoff, and other means.7 One ofthe most important groups of organic contaminants, polycyclicaromatic hydrocarbons (PAHs), have been shown to causeadverse effects on humans and wildlife because of theirwidespread occurrence, toxic potency, and bioaccumulativeability through the aquatic food web.8−10 In many cases, thefreely dissolved or bioavailable concentration instead of totalconcentration is directly related to bioaccumulation and humanexposure to organic contaminants.11−13

Measurement of freely dissolved organic contaminants on alarge spatial scale, which is critical for identifying trends andpatterns, is no trivial task. The passive sampling approach,capable of simultaneously sampling in a large range of areas, isbeneficial in this aspect.11 Among the available passivesamplers, devices with low density polyethylene (LDPE) asthe sorbent phase have been recommended as a preferredalternative for sensing organic contaminants in aquaticenvironments because they are consistent, biomimetic,inexpensive, and convenient for field deployment.14−16

Enormous economic development and urbanization in Chinahave created severe water pollution issues, which, however, hasnot been adequately monitored.12,17 One of the reasons isobviously that China’s vast territorial area, amounting to more

Received: April 18, 2017Revised: June 25, 2017Accepted: June 27, 2017Published: June 27, 2017

Article

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than 9.6 million square kilometers, poses a great challenge toany monitoring effort. On the other hand, China’s variablegeographical settings and population distribution patternspresent an unparalleled opportunity for examining whetherfreshwater quality has been significantly impacted byanthropogenic activities. Building on our previous efforts indevelopment of robust passive samplers for sensing organiccontaminants in open waters,18,19 we conducted a large-scalesurvey to examine water quality in China using passivesampling techniques. The present campaign was also apreliminary study for a recent effort to establish the AquaticGlobal Passive Sampling (AQUA-GAPS) network.11

The objectives of the present study were to (1) betterunderstand the geographical distribution of freely dissolvedPAH concentrations in freshwater systems of China; (2)examine the relationship between freely dissolved PAHconcentrations and regional population densities to elucidatethe impacts of anthropogenic activities on water quality; and(3) diagnose the potential sources of PAHs in the freshwatersystems under investigation. In the past decade, numerousstudies have been conducted on the occurrence of organiccontaminants in freshwater of China, which, however, werelargely focused on East China, such as the Yangtze River Deltaand the Pearl River Delta.12,20,21 To accomplish the objectivesmentioned above, we deployed a self-developed passive samplerin a wide range of regions in West, East, and Central Chinawith large gradients in population densities and levels ofeconomic development. The passive sampler with LDPE as thesorbent phase and a copper box as protecting mechanism wasdemonstrated to be a useful tool for quantifying freely dissolvedorganic contaminants in seawater (Hailing Bay, China) and infreshwater lakes of Antarctica.18,19

■ MATERIALS AND METHODS

Passive Sampler Preparation. Materials, passive samplerpreparation and deployment procedures, and geographicinformation and characteristics of each sampling site are listedin the Supporting Information Text S1 and Tables S2−S3.Briefly, samplers were deployed at 42 sites, located mainly inNortheast (Songhua River Basin and Liaohe River Basin),Central and East (Yangtze River Basin), and Northwest (lakesand reservoirs of the Xinjiang Uygur Autonomous Region)China in July to November 2013 and Southwest (lakes of theTibet Plateau) China in May to September 2015. All LDPEstrips were spiked with the performance reference compounds(PRCs), i.e., anthracene-d10, benzo[a]anthracene-d12, benzo-[a]pyrene-d12, PCB-29, PCB-61, PCB-155, p,p′-DDT-d8, p,p′-DDD-d8, and p,p′-DDE-d8, by soaking in a mixed solution(Vmethanol:Vwater = 50:50) for 30 d before deployment (placed ona shaking bed at 200 r min−1 in dark). The prepared LDPEswere wrapped in clean aluminum foil and kept in ice chestsduring transport to the sampling sites. At each sampling site, atleast three passive samplers were deployed approximately 1 mbelow the water surface for 15 d with 100 m or longer distancefrom each other depending on the sizes of the target lakes orreservoirs. To reduce inshore influences, the samplers wereplaced as far away as possible from the watersides. Uponretrieval, the sampling devices were disassembled, and theLDPE strips were retrieved and maintained in ice chests duringtransport to the laboratory. A total of 40 top surface (0−5 cm)soil samples were collected at the same time when passivesamplers were deployed; soil samples were not available at

several sites. The procedures for collecting and extracting soilsamples are described in Text S2.

Extraction of Polyethylene Strips. The LDPE strips wererinsed with purified water and cut into small pieces (about 2 cm× 2 cm), wrapped in filter paper (sonicated with dichloro-methane and methanol three times each and dried before use),and extracted three times by soaking in 200 mL of hexane for24 h. The surrogate standards were added to each samplebefore extraction. Three extracts from each sample werecombined and concentrated to approximately 10 mL with aZymark Turbo Vap II (Hopkinton, MA) at 30 °C. Afterdehydration with sodium sulfate, the extract was reduced to 0.5mL with the Zymark Turbo Vap II and purified on a glasscolumn (8-mm inner diameter) packed with neutral alumina(0.8 g), neutral silica gel (0.8 g), and sodium sulfate (0.5 cm)from bottom to top. The eluate was condensed to 100 μL andspiked with internal standards, i.e., fluorene-d10, pyrene-d10,dibenzo[a,h]anthracene-d14, PCB-24, PCB-82, and PCB-189prior to instrumental analysis. Specifically, fluorene-d10, pyrene-d10, and dibenzo[a,h]anthracene-d14 were used to quantifyPAHs, whereas PCB-24, PCB-82 and PCB-189 were used todetermine the concentrations of PCB or DDT compounds.Detailed instrumental analysis are described in Text S1.

Quality Assurance and Quality Control. One field blankand one initial PRC concentration blank were processed at eachsampling site and one laboratory blank was processed for everybatch of 20 samples. Overall, there were 39 sampling sites with134 field samples and 62 blank samples retrieved (includingfield, field-trip, and laboratory blank samples). The concen-trations of target PAHs in blank samples were lower than 10%of those in the corresponding field samples. The concentrationsof PAHs in field samples were blank-subtracted using eachspecific field blanks from the corresponding site but notcorrected for the surrogate standard recoveries. Becausenaphthalene was quite abundant in several LDPE samples, itwas excluded from further analyses. The recoveries of thesurrogate standards, i.e., naphthalene-d8, acenaphthene-d10,phenanthrene-d10, chrysene-d12, PCB-67, and PCB-191, were52 ± 10%, 79 ± 13%, 100 ± 13%, 112 ± 21%, 98 ± 25%, and77 ± 22% in all blank samples and 47 ± 11%, 84 ± 10%, 104 ±12%, 108 ± 20%, 98 ± 20%, and 77 ± 19% in the field samples.The reporting limit (RL) was calculated from the lowestcalibration level divided by the mass of LDPE (about 4 g foreach passive sampler). It was 1.25 ng g−1 for each LDPE passivesampler for all target analytes except IcdP, DahA, and BghiP(the abbreviations of PAH compounds are listed in Table S1),which had a RL of 2.5 ng g−1 for their relatively low massspectral responses. The concentrations of target PAHs were allbelow RLs in re-extracted LDPE samples.

Data Analysis. The dissolved concentration (Cw) of a targetPAH analyte at each sampling site was calculated via akinetically diffusion-controlled quantitation method,16,22 i.e.,

=− −⎜ ⎟

⎡⎣⎢

⎛⎝

⎞⎠⎤⎦⎥

CC

K 1 exp R tK M

wpe

pews

pew pe (1)

where Cpe is the analyte concentration in LDPE at samplingtime t, Kpew is the equilibrium partition coefficient of the targetanalyte between LDPE and water, Rs is the sampling rate, andMpe is the LDPE mass.16 The Kpew values of PAHs (Table S1)were adopted from the results of Reitsma et al.23 under ambientconditions (25 °C and 0 psu), similar to the conditions in the

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present study. Rs can be estimated by the dissipation rates ofpreloaded PRCs using linear regression and molecular volumeadjustment (Table S4). Procedures for calculating Cw andassociated errors were detailed in our previous study.18

Ratios of several paired PAH isomers with similarphysicochemical properties have been employed to diagnoseemission sources of PAHs derived from passive samplingtechniques, such as Flu/(Flu + Pyr), Ant/(Ant + Phe), andBaA/(BaA + Chr).14,15,24−26 If the dissolved concentrations ofindividual PAH isomers were below the reporting limits, suchas Phe, Ant, and BaA at TI-1 and TI-3 sites, BaA at LH-3 andXJ-8 sites, and Phe at YR-7 site, the corresponding paired PAHdiagnostic ratios were excluded for source assessment.

■ RESULTS AND DISCUSSION

Spatial Trend of Freely Dissolved PAH Concentra-tions. Sampling rates (Rs) of PAHs varied at different samplingsites, and the average Rs was 6 ± 4 L d−1 for Ant, 155 ± 98 Ld−1 for BaA, and 1025 ± 650 L d−1 for BaP. They increasedwith increasing log Kpew, which was similar to the results ofother studies.14,15 It should be noted that equilibriumpartitioning between LDPE membrane and water may bereached for lighter PAH compounds with lower sampling ratesthan Ant, such as 2-mNap, 1-mNap, 2, 6-dimNap, ΣC2−Nap,BP, Acy, Ace, and Flo at some sampling sites. On the otherhand, the PAH concentrations in our sampling sites (most lakesand reservoirs) were assumed not to vary considerably duringthe 15-d sampling period. No floods or large point sourceinputs to the sampled water bodies were recorded during the

sampling period. Thus, the measured concentrations of theselight PAHs may be taken as the water concentrations over thewhole sampling period.The concentration data for individual PAHs, along with the

sums of the 24 target PAHs specifically targeted in the presentstudy (Σ24PAH), 15 priority PAHs (Σ15PAH) designated bythe U.S. Environmental Protection Agency (USEPA) exceptnaphthalene, and 7 carcinogenic PAHs (Σ7PAH; the sum ofBaA, BbF, BkF, BaP, IcdP, DahA, and BghiP) classified by theUSEPA, are presented in Tables S5−S10. The Σ24PAH,Σ15PAH, and Σ7PAH concentrations in lakes and reservoirsalong Songhua River and Liaohe River located in NortheastChina (Figure 1) were in the ranges of 1.7−11.3 ng L−1 (mean:7.2 ng L−1), 1.2−5.9 ng L−1 (mean: 3.9 ng L−1), and notdetected (ND)−67 pg L−1 (mean: 18.5 pg L−1), respectively.Compared to Songhua River and Liaohe River, the PAH

concentrations in lakes and reservoirs of the Xinjiang UygurAutonomous Region located in Northwest China (Figure 1)were lower, i.e., the Σ24PAH, Σ15PAH, and Σ7PAHconcentrations were in the ranges of 1.3−16.4 ng L−1 (mean:6 ng L−1), 0.7−6.7 ng L−1 (mean: 3 ng L−1), and ND−32 pgL−1 (mean: 11 pg L−1), respectively. The PAH concentrationsin the Yangtze River flowing through Central and East China(Figure 1) were the highest among all the regions, i.e., theΣ24PAH, Σ15PAH, and Σ7PAH concentrations were 4−538 ngL−1 (mean: 56 ng L−1), 1.4−293 ng L−1 (mean: 29 ng L−1), and7.4−503 pg L−1 (mean: 58 pg L−1), respectively. The greatestconcentration among all sampling sites occurred at SouthernLake, an urban lake within Wuhan heavily polluted by urban

Figure 1. Spatial distribution of dissolved PAHs in freshwaters in China. Σ24PAH is the sum of Σ15PAH and 2-mNap, 1-mNap, BP, ΣC2−Nap, ΣC3−Nap, ΣC1−Phe, ΣC2−Phe, BeP, and Per. Σ15PAH is the sum of 16 priority PAHs identified by the USEPA except Nap. Σ7PAH is the sum of sevencarcinogenic PAHs (BaA, BbF, BkF, BaP, IcdP, DahA, and BghiP). The maximum values of these bars are 20 ng L−1, 20 ng L−1, and 200 pg L−1 forΣ24PAH, Σ15PAH, and Σ7PAH, respectively. When the PAHs concentrations at sampling sites were higher than the maximum values, the data arepresented as numbers in red.

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wastewater derived from surrounding factories and residents.27

Southern Lake was therefore identified as a point source andexcluded from the following discussions. The PAH concen-trations in lakes of Tibet located in Southwest China (Figure 1)were the lowest among all sampling regions, with the Σ24PAH,Σ15PAH, and Σ7PAH concentrations in the ranges of 0.28−0.8ng L−1 (mean: 0.54 ng L−1), 0.01−0.05 ng L−1 (mean: 0.03 ngL−1), and ND−0.52 pg L−1 (mean: 0.3 pg L−1), respectively.Anthropogenic Impacts on Levels of Freely Dissolved

PAHs. Freshwater PAH levels (average Σ24PAH) graduallyincreased from west to east, i.e., 5.4 ± 4.3, 11 ± 11, and 12 ±13 ng L−1, in Western (Tibet and Xinjiang), Central (the upperand middle reaches of the Yangtze River), and Eastern (thelower reaches of the Yangtze River, Liaohe River, and SonghuaRiver) China (Figure 1). This spatial pattern was correlatedwell with the distribution of regional population densities(Table S11), with the determination coefficients (r2) betweenthe concentrations of Σ24PAH, Σ15PAH, and Σ7PAH and thepopulation densities at 0.95 (p < 0.0001), 0.87 (p < 0.0005),and 0.36 (p = 0.07) (Figure 2). Similarly, the concentrations ofΣ24PAH and Σ15PAH also correlated well with the ratio of gross

domestic product/land area (10−1 billion km−2; Table S11),with the determination coefficients (r2) at 0.97 (p < 0.0001)and 0.97 (p < 0.0001), respectively (Figure S1). The correlationbetween Σ7PAH concentrations and the ratio of gross domesticproduct/land area was not significant (r2 = 0.25 and p = 0.25;Figure S1). The use of more target compounds appeared toyield better correlation, which implies that (1) dissolved PAHsin the freshwater bodies may have derived from multiplesources related to complicated anthropogenic activities, and (2)there is an urgent need to identify suitable parameters for betterdescribing anthropogenic activities. McDonough et al.14 alsoobtained a significant correlation between the concentrations ofgaseous PAHs and population densities in the lower GreatLakes. In addition, the correlation between the concentrationsof dissolved PAHs in surface water and PAHs in thesurrounding soil was poor (r2 < 0.1; Figure S3), suggestingno significant contribution from nearby soil to the occurrenceof PAHs in freshwaters.Besides population density, industrialization may also be an

important factor. The population densities of Songhua RiverBasin and Liaohe River Basin are quite similar to each other(263 and 292 persons km−2, respectively),28,29 but the Σ7PAHconcentrations in Songhua River Basin were 1−2 orders ofmagnitude higher than those in Liaohe River Basin, with highlevels around the city of Jilin (Figure 1). Government data30

Figure 2. Correlations between the concentrations of Σ24PAH,Σ15PAH, and Σ7PAH and population densities (10 person km−2) inthe sampling regions. Σ24PAH is the sum of Σ15PAH and 2-mNap, 1-mNap, BP, ΣC2−Nap, ΣC3−Nap, ΣC1−Phe, ΣC2−Phe, BeP, and Per.Σ15PAH is the sum of 16 priority PAHs identified by the USEPAexcept Nap. Σ7PAH is the sum of seven carcinogenic PAHs (BaA,BbF, BkF, BaP, IcdP, DahA, and BghiP).

Figure 3. Comparison of the amounts of domestic and industrialwastewater discharged to Songhua River Basin and Liaohe River Basinfrom their surrounded cities over the years of 2004−2006 and 2011−2012.30 The data of 2007−2010 was not available in this official annualreport.

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showed that the amounts of industrial wastewater discharged toSonghua River Basin were much greater than those dischargedto Liaohe River Basin over the years of 2004−2006 and 2011−2012 (Figure 3). A great number of factories are situated alongthe banks of Songhua River, including steel, petrochemical,pulp and paper, and machinery mills.30 These manufacturingplants discharge large amounts of insufficiently treatedwastewater to Songhua River. Accidental spills have also beenidentified as input sources of organic chemicals, heavy metals,nitrogen-containing substances, and other pollutants.31−33

Worldwide Comparison of Freely Dissolved PAHLevels. The concentrations of freely dissolved PAHs in thepresent study were in the middle range of those reported

worldwide (Table 1). After excluding samples collected fromthe middle and lower Yangtze River, however, the concen-trations of Σ15PAH (0.4−10 ng L−1) in the present study weremuch lower than those reported previously in freshwaters. Forexample, concentrations of Σ15PAH were 8.6−48 ng L−1 in theMeuse-Marne Canal downstream of Paris, France,34 9.5−66 ngL−1 in rivers close to Johannesburg, South Africa,24 and 2.8−29ng L−1 in the Danube river between Vienna and Bratislava.35

Our previous study also obtained low concentrations ofΣ15PAH (<0.01−4.1 ng L−1) in inland lakes of EastAntarctica.18 On the other hand, the results in the presentstudy were comparable to most reported concentrations ofdissolved PAHs in seawater, such as those in southern

Table 1. Comparison of Concentration Range (Mean ± Standard Deviation; Median Value; ng L−1) of Σ15PAH and Σ7PAH,along with Average Concentration (Mean ± Standard Deviation; ng L−1) of Acenaphthene (Ace), Fluorene (Flo),Phenanthrene (Phe), and Anthracene (Ant) in the Present Study with Worldwide Freely Dissolved PAHs Levels

location Σ15PAHc Σ7PAH

d Ace Flo Phe Ant time method

Present Study (Rivers and Lakes)

Songhua Rivers 1.1−10 (3.5 ± 2.3;3.3)

0.001−0.12 (0.03 ± 0.03; 0.02)

0.30 ± 0.20 1.1 ± 0.86 0.82 ± 0.83 0.43 ± 0.66 2013 LDPE

Liaohe River Basin 1.7−7.9 (4.4 ± 1.8;4.2)

<0.01−0.02(0.004 ± 0.004; 0.003)

0.39 ± 0.22 1.6 ± 0.70 1.4 ± 0.71 0.38 ± 0.70 2013 LDPE

Xinjiang Provincea 0.4−7.6 (3.0 ± 1.9;2.8)

<0.007−0.04(0.01 ± 0.01; 0.01)

0.28 ± 0.23 1.1 ± 0.89 0.86 ± 0.70 0.11 ± 0.10 2013 LDPE

Upper Yangtze River 0.67−4.2 (1.7 ± 0.9; 1.6)

0.002−0.02(0.01 ± 0.005; 0.01)

0.06 ± 0.09 0.45 ± 0.46 0.18 ± 0.33 0.06 ± 0.37 2013 LDPE

Middle YangtzeRiverb

1.3−8.5 (4.3 ± 2.1;4)

<0.02−0.04 (0.02 ± 0.01; 0.02)

0.18 ± 0.13 1.3 ± 0.59 1.2 ± 0.96 0.21 ± 0.31 2013 LDPE

Lower Yangtze River 0.2−33 (11 ± 9.7;10)

<0.02−0.08 (0.02 ± 0.02; 0.01)

1.0 ± 2.5 3.5 ± 2.7 4.8 ± 5.1 0.46 ± 0.54 2013 LDPE

Freshwaters (Rivers and Lakes)

Luhu Park, China (25 ± 4.6)e (1.8 ± 0.4) NA 2.5 ± 1.1 7.7 ± 3.3 0.45 ± 0.27 2001−200263 SPMD

Three GorgesReservoir, China

13−80 (30 ± 19;20)

1.1−2.1 (4.8 ± 2.3; 4.8) 1.16 ± 2.01 1.6 ± 2.0 5.7 ± 5.71 0.86 ± 0.85 200837 SPMD

(87 ± 112)f NA NA NA NA NA 200939 SPMD

(44 ± 40)f NA NA NA NA NA 201139 SPMD

Meuse-Marne canal,France

8.6−48 (30 ± 20;32)e

0.8−5.9 (3.4 ± 2.6; 3.6) NA 2.1 ± 1.0 4.7 ± 1.7 1.1 ± 0.76 2008−200934 SPMD

Brisbane River,Australia

6.5−12 (8.8 ± 2.0;9)g

0.44−4.8 (1.7 ± 1.7;2.4)h

0.01 ± 0.01 0.14 ± 0.07 0.80 ± 1.3 0.19 ± 0.16 2001−200238 SPMD

Great Lakes, USA 2.1−26 (7.1 ± 5.8;5.6)i

0.02−2.3 (0.3 ± 0.5; 0.2) NA 0.25 ± 0.26 1.2 ± 0.54 0.23 ± 0.24 201114 LDPE

Johannesburg, SouthAfrica

9.5−66 (23 ± 19;14)

0.2−17.6 (3.3 ± 5.8; 1.3) 1.9 ± 1.1 2.5 ± 2.2 4.7 ± 4.5 1.6 ± 1.2 201124 SPMD

Danube River, Europe 2.8−29 (12 ± 6.3;11)

0.12−3.7 (1.1 ± 0.83;0.94)

0.80 ± 0.43 1.56 ± 1.0 3.6 ± 2.6 0.25 ± 0.12 2010−201135 SPMD

Inland Lakes,Antarctica

<0.01−4.1(2.0 ± 1.9; 1.7)

ND NA 1.6 ± 0.72 1.8 ± 1.2 ND 201318 LDPE

Seawaters

Chesapeake Bay, USA 2.4−3.8 (3.1 ± 1.0;3.1)

0.003−0.006(0.005 ± 0.002; 0.01)

0.74 ± 0.34 0.80 ± 0.25 0.95 ± 0.21 0.05 ± 0.02 199436 SPMD

Moreton Bay,Australia

0.11−0.6 (0.3 ± 0.3; 0.17)g

0.004−0.037(0.022 ± 0.02; 0.02)h

<LOD 0.014 ± 0.019 0.066 ± 0.09 0.001 ± 0.002 2001−200238 SPMD

Narragansett Bay,USA

0.16−5.7 (1.3 ± 1.2; 1)

0.017−0.65 (0.13 ± 0.12; 0.1)

0.01 ± 0.01 0.03 ± 0.02 0.29 ± 0.24 0.08 ± 0.06 200615 LDPE

Ekofisk oil platform,Norway

2.5−4.5 (3.5 ± 0.9;3.5)

0.28−0.34 (0.3 ± 0.02;0.3)

0.12 ± 0.03 0.57 ± 0.25 1.75 ± 0.62 <0.04 200845 SPMD

North Sea, Norway 1.6−2.2 (1.9 ± 0.4;1.9)

0.19−0.19 (0.19 ± 0.0;0.19)

0.08 ± 0.0 0.34 ± 0.08 0.73 ± 0.12 <0.04 200845 SPMD

Gulf of Mexico, USA 0.7−88 (9.5 ± 16;5.5)j

<0.01−1.5 (0.52 ± 0.47;0.28)k

1.31 ± 1.35 0.60 ± 0.67 1.38 ± 3.54 NA 2010−201140 LDPE

aXinjiang Province is short for the Xinjiang Uygur Autonomous Region. bSouthern Lake was identified as point source and excluded fromcalculation. cΣ15PAH: 16 priority PAHs designated by the USEPA except Nap. dΣ7PAH: seven carcinogenic PAHs classified by the USEPA: BaA,BbF, BkF, BaP, IcdP, DahA, and BghiP. eΣ15PAH except for Acy and Ace. fSum of Σ15PAH and Nap, i.e., 16 priority PAHs. gΣ15PAH except for BaP.hΣ7PAH except for BaP. iΣ15PAH except for Ace. jΣ15PAH except for Acy, Ant, and BghiP. kΣ7PAH except for BghiP. The abbreviations of PAHcompounds are listed in Table S1. NA means not available. ND means not detected. LOD is the abbreviation of limits of detection. LDPE is theabbreviation of low density polyethylene. SPMD is the abbreviation of semipermeable membrane devices.

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Chesapeake Bay (2.4−3.8 ng L−1)36 and Narragansett Bay(0.16−5.7 ng L−1).15 The low PAH concentrations in bayscould be resulted from dilution by seawater from the ocean.For Σ7PAH (Table 1), the Three Gorges Reservoir had the

highest concentrations (4.8 ± 2.3 ng L−1)37 among all theregions mentioned above, followed by the Meuse-Marne Canal(3.4 ± 2.6 ng L−1),34 Johannesburg of South Africa (3.3 ± 5.8ng L−1),24 the Brisbane River (1.7 ± 1.7 ng L−1),38 and theDanube river (1.1 ± 0.83 ng L−1).35 The Three GorgesReservoir is located only 15 km down stream of YR-3 site inZigui county in the present study (Table S2), but containedhigher Σ15PAH concentrations (44 ± 40 ng L−1 in 2011)37

even during the impoundment period than those in YR-3 site(1.8 ± 0.6 ng L−1 in 2013). The high levels of PAHs in theThree Gorges Reservoir were probably caused by extensiveshipping activities (up to 400 000 ships in 2008) and theconstruction of highways to relieve the shipping traffic in theThree Gorges Reservoir.39 Finally, the highest concentrationsof individual PAHs, such as Ace, Flo, Phe, and Ant, occurred inJohannesburg,24 the lower reaches of the Yangtze River, and theThree Gorges Reservoir,37 respectively. All these regions aresubject to the influences of intensive anthropogenic activities.It is difficult to quantify the relationship between the

concentrations of dissolved PAHs available in the literature andcorresponding regional population densities, because the datawere acquired at quite different time periods. However,sampling sites in Paris, Johannesburg, Vienna, and Bratislava,either the capital or the largest city of a country, all containedfairly high concentrations of Σ15PAH. The Deepwater Horizonoil spill led to considerably high concentrations of dissolvedPAHs in Gulf of Mexico (0.7−88 ng L−1), another example ofhuman interference with the occurrence of dissolved PAHs.40

Source Diagnostics of Dissolved PAHs. The composi-tion profiles and distribution patterns of PAHs in SonghuaRiver, Liaohe River, freshwaters of the Xinjiang UygurAutonomous Region, and the Yangtze River were similar toeach other (Figure 4). For example, 3-ring PAHs were thedominant components (65%, 57%, 52%, and 47%, respec-tively), followed by 2-ring PAHs (25%, 40%, 42%, and 40%,respectively) and 4-ring PAHs (10%, 3%, 6% and 13%,

respectively), while the relative abundance of 5 + 6-ringPAHs was lower than 1% in all sampling sites. The exceptionwas Tibet where the relative abundance of 2-ring PAHs wasartificially inflated because other PAH compounds were rarelydetected. This distribution pattern of PAHs was similar to thosefound in the gaseous phase of grass,41 wood,41−43 raw coal,44

and coal briquette combustion44 and the water-soluble fractionof fuels,23,45 dominated by the sum of 2- and 3-ring PAHsaccounting for 83%, 90%, 90%, 90%, and 98%, respectively, ofthe total PAH contents (Figure S4). The proportion ofalkylated PAHs was in the range of 38−52% reflecting majorpetrogenic sources and emissions from low-temperaturecombustion, such as vaporization or leakage of petroleum-associated products and emissions from coal briquette andother residential solid fuels.46−48 All these findings suggestedthat PAHs detected in the present study were derived frommultiple anthropogenic sources.Calculated isomer ratios of PAHs and detailed interpreta-

tions are presented in Figures S5−S6 and Text S3. It has beenrecommended that caution must be exercised when isomerratios are interpreted.20,25 Briefly, all sampling areas exceptTibet were subject to PAH inputs from multiple sources ofpetroleum, coal, or biomass combustion and diesel combustion,which are in line with previously reported results in sedimentsadjacent to our study regions.49−56 Overall, potential sources ofdissolved PAHs in surface waters of China can be categorized asof predominantly anthropogenic sources, which includeindustrial and domestic wastewater discharge and leakage andcombustion of petroleum products among others.

Water Quality Concerns and Implications. Among allthe water bodies sampled in the present study, 21 lakes andreservoirs serve as sources of drinking water and six are used forfishery and natural reserve wetlands (Table S3). To protecthuman health, various environmental agencies and organiza-tions have published guidelines and water quality criteria. Forexample, the USEPA in 1980 developed ambient water qualitycriteria and set maximum concentrations for seven carcinogenicPAHs, i.e., BaA at 100 ng L−1, Chr, BbF, BkF, and BaP at 200ng L−1, IcdP at 400 ng L−1, and DahA at 300 ng L−1. In 2015,the USEPA again published water quality guidelines for human

Figure 4. Compositional profiles of dissolved PAHs in freshwaters in China. The columns and error bars represent the average values and standarddeviations, respectively.

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health due to consumption of water and organisms, with Ace at70 000 ng L−1, Flo at 50 000 ng L−1, Flu and Pyr at 20 000 ngL−1, BaA, BbF, and IcdP at 1.2 ng L−1, Chr at 120 ng L−1, BkFat 12 ng L−1, and BaP and DahA at 0.12 ng L−1.57 In 2008, theEuropean Union also released environmental quality standardsfor priority substances in surface waters, and set maximumallowable concentrations for several individual PAHs, i.e., Ant at400 ng L−1, Flu at 1000 ng L−1, BaP at 100 ng L−1, benzo[b +k]fluoranthene at 30 ng L−1, and the sum of IcdP and BghiP at2 ng L−1.58 In 1999, the Canadian Council of Ministers of theEnvironment developed water quality guidelines for theprotection of aquatic life for several PAHs, including Ace,Flo, Phe, Ant, Flu, Pyr, BaA, and BaP, at 5800, 3000, 400, 12,40, 25, 18, and 15 ng L−1, respectively, for long-termexposure.59 Similarly, some U.S. states, such as New York,Pennsylvania, and Texas, also published water quality standardsfor protecting aquatic life from PAHs.60−62 For example, theDepartment of Environmental Conservation of New Yorkrecommended the guidance values of Nap, 2-mNap, Acy, Flo,Phe, Ant, Pyr, and BaA for protection of aquatic life fromchronic effects at 13 000, 4700, 5300, 540, 5000, 3800, 4600,and 30 ng L−1, respectively.61

All concentrations of dissolved PAHs in the present studywere below the above-mentioned guidelines except for Ant inSouthern Lake in Wuhan (27 ± 3.3 ng L−1), which exceeds thewater quality guidelines by the Canadian Council of Ministersof the Environment (12 ng L−1). Nevertheless, the selectedfreshwater systems under investigation were somewhat pollutedby PAHs, especially those surrounding densely populatedmetropolises. This justifies the need to establish a nationwidelong-term monitoring program in China. To this end, theAQUA-GAPS network may serve as a catalyst to stimulate localand national interests in accomplishing the goal.11 It should benoted that freshwater pollution by other substances such asmetals and nutrients is currently more severe than that byorganic contaminants, and any monitoring program should alsoincorporate these more important parameters.

■ ASSOCIATED CONTENT

*S Supporting InformationThe Supporting Information is available free of charge on theACS Publications website at DOI: 10.1021/acs.est.7b02008.

Additional texts, tables, and figures of PAHs infreshwaters of China (PDF)

■ AUTHOR INFORMATION

Corresponding Author*Phone: +86-020-85226853; fax: +86-020-85226615; e-mail:baolianjun@jnu.edu.cn.

ORCID

Lian-Jun Bao: 0000-0002-0634-0829NotesThe authors declare no competing financial interest.

■ ACKNOWLEDGMENTS

The present study was financially supported by the Ministry ofScience and Technology of China (2012ZX07503-003-002)and National Natural Science Foundation of China (41403087and 41390240). This is contribution IS-2405 from GIGCAS.

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