Polychlorinated naphthalenes (PCNs) in surface sediments of the Yangtze and Yellow River Estuaries,...

2013, Vol.18 No.1, 079-087

Article ID 1007-1202(2013)01-0079-09

DOI 10.1007/s11859-013-0897-9

Polychlorinated Naphthalenes (PCNs) in Surface Sediments of the Yangtze and Yellow River Estuaries, China

□ GUO Li1,2, GAO Lirong2†, LI Aimin1, XIAO Ke2

1. Hubei Environmental Monitoring Central Station, Wuhan

430072, Hubei, China;

2. State Key Laboratory of Environmental Chemistry and

Ecotoxicology, Research Center for Eco-Environmental Sciences,

Chinese Academy of Sciences, Beijing 100085, China

© Wuhan University and Springer-Verlag Berlin Heidelberg 2013

Abstract: The concentrations and congener profiles of poly-chlorinated naphthalenes (PCNs) in surface sediment samples collected from the Yangtze and Yellow River Estuaries were inves-tigated. PCN congeners (from MoCNs to OCN) were determined by isotope dilution/high-resolution gas chromatography/high- resolution mass spectrometry (HRGC-HRMS). The total concen-trations of PCNs were 34.3-303.0 pg/g (dry weight, dw) in the Yangtze Estuary samples and 6.2-408.0 pg/g (dw) in the Yellow River Estuary samples, which were lower compared with that in other sediments reported by previous studies. In addition, the re-markably different homologue or congener profiles of PCNs have been obtained in this study. Samples dominated with MoCNs to TrCNs might be attributed to atmospheric deposition and global fractionation, while in other samples taken from the surrounding industrial areas the enrichment of higher chlorinated homologues suggested that the industrial and human activities should be the main potential sources. Key words: polychlorinated naphthalenes (PCNs); sediments; Yangtze Estuary; Yellow River Estuary CLC number: X 132

Received date: 2012-04-19 Foundation Item: Supported by the National Natural Science Foundation of China (20677070, 20621703) Biography: GUO Li, female, Engineer, Ph. D., research direction: distribution, source, environmental behavior of persistent organic pollutants in environments. E-mail: [email protected] † To whom correspondence should be addressed. E-mail: [email protected]

0 Introduction

Polychlorinated naphthalenes (PCNs) have been used since 1910 in the world but were newly selected as candidate by the United Nations Economic Commission of Europe (UN-ECE) for persistent organic pollutants (POPs) Protocol in 1998[1,2]. These products were widely used in many industries, such as cable insulation, ca-pacitor impregnants, lubricants, flame retardants, carriers in dye production, wood preservatives, and oil addi-tives[3-6]. Additionally, PCNs were also unintentionally released as trace contaminants in the processes such as waste incineration and chemical industries[7-9].

Generally, PCNs consist of 75 congeners, in which the number of chlorine atoms and position of substitu-tions are different, whereas their physical and chemical properties and usages are similar to that of polychlori-nated biphenyls (PCBs)[10,11]. In fact, it has been demon-strated that several individual PCN congeners exhibit dioxin-like toxicity as some of the coplanar congeners of PCBs[12,13]. In addition to being persistent and toxic, PCNs are bio-accumulative in food webs[14-16].

Although the production and usage of PCNs have been substituted largely by other chemicals in many coun-tries, PCNs are still ubiquitous global contaminants in the environment because of continuous emission as byproduct of other chemical industries and residues from previous great amount usage. During the last few decades, many studies on PCNs focused on air[17,18], water, soil and sedi-ment[19-21], biota, and human milk[5,14,22,23]. Furthermore, PCNs have also been found in remote areas such as the

Wuhan University Journal of Natural Sciences 2013, Vol.18 No.1 80

Arctic regions because of their persistence and long-range atmospheric transportation[24-26]. Compared with other POPs such as PCBs and dioxins, the knowledge on the distribution, behavior, transport, and environmental risk of PCNs is still very sparse[16,19]. Thus, it is necessary for environment management to evaluate these compounds from different environmental medias.

The Yangtze and Yellow Rivers are the first and sec-ond largest rivers in China, respectively, which play an important role in the economic development of China. Thus, it will be essential for the ecology conversation, fishery protection, and even human health to survey the occurrence of PCNs, which will provide a scientific basis for the policy decision of environment. Although the re-cent studies on PCN concentrations in China revealed that low levels of PCNs have been determined in the air[27], sediment[28], and seafood[15] in China, the investi-gations on PCN concentrations and distribution were still very limited. Especially, no study on PCNs has been conducted in the Yangtze Estuary (YTE) and Yellow River Estuary (YRE). Therefore, in this study, the fol-

lowing characteristics were present: ① surveying the concurrency of PCNs in the two regions and ② assessing the possible sources and potential toxicities of PCNs. Our study is believed to be the first attempt to survey the oc-currence of PCNs in the two estuaries and will be helpful for revision of related sediment standards in the future.

1 Materials and Methods

1.1 Sampling Fifteen sediment samples were collected from the

YRE (118°15′E-119°20′E, 37°20′N-37°50′N), all dis-tributed in Dongying City, while the other six sediment samples were collected from the YTE (120 °04′E- 121°52′E, 31°09′N-31°46′N) in May 2007. Both GPS coordinates and the local maps were used to evaluate the sampling sites. The sampling locations are shown in Fig. 1. All of the surface sediments (0-5 cm) were sampled using a stainless steel grab sampler, placed in aluminum foil, and stored in a freezer at − 20 ℃ or less for further analysis.

Fig. 1 Maps of study areas and sampling sites (a) sampling sites in the YTE; (b) sampling sites in the YRE

1.2 Sample Preparation and Purification The surface sediments were frozen-dried at about

−50 ℃, ground, and homogenized to fine power to pass a 40 mesh screen. Then, about 10 g of these pretreated samples homogenized with anhydrous sodium sulphate were Soxhlet-extracted with toluene for 24 h. Prior to extraction, isotope-labeled PCN standard solution (con-taining 13C10-CN-27, 13C10-CN-42, 13C10-CN-52, 13C10- CN-67, 13C10-CN-73, and 13C10-CN-75, purchased from Cambridge Isotope Laboratories, Andover, MA, USA) was spiked as internal standard. The extract was concen-trated to dryness using a rotary evaporator and then transferred the solvent to hexane.

The concentrated extracts were subsequently puri-fied and fractionated by acidic silica gel, multi-layer sil-ica gel, and basic alumina columns in turn. Samples were subjected to purification on a 70 g BioBead-SX3 gel

permeation chromatography (GPC) for further cleanup, if necessary. The first column, packed with 10 g 44% (m/m) acidic silica gel and 4 g anhydrous sodium sul-phate, was used to remove lipid and polycyclic aromatic hydrocarbons (PAHs). The multi-layer silica gel column was packed from bottom to top with 1 g activated silica, 2 g 10% (m/m) AgNO3 silica, 1 g activated silica, 3 g 33% (m/m) basic silica, 1 g activated silica, 8 g 44% (m/m) acidic silica, 1 g activated silica, and 4 g anhy-drous sodium sulphate. The column was eluted with hexane and transferred to a column containing 8 g basic alumina and 4 g anhydrous sodium sulphate. Afterwards, the elution was concentrated with gentle nitrogen flow to dryness and filled with 20 μL nonane in a mini-vial. To check the recovery of internal standards, a 13C10-labeled standard of PCN (CN-64) was added to the extracts prior to analysis.

GUO Li et al : Polychlorinated Naphthalenes (PCNs) in Surface Sediments …

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1.3 HRGC-HRMS Analysis PCNs identification and quantification were carried

out with a high-resolution gas chromatography/high- resolution mass spectrometry (HRGC-HRMS) system (double-trace GC and DFS, Thermo Electron Corp.) on a resolution of approximately 10 000. A DB-5 (J&W, 60 m×0.25 mm i.d., 0.25 μm film thickness) capillary column was used for determining PCN congeners. The column temperature was initiated at 80 ℃ (2 min) and in-creased to 180 ℃ (1 min) by 20 ℃/min then to 280 ℃ by 2.5 ℃/min until up to 290 ℃ (5 min) by 10 ℃/min. The injector, interface, and ion source temperature were 260, 290, and 270 ℃, respectively. The mass spec-trometer was operated at an electron impact (EI) energy of 45 eV using perfluorotributyl amine (FC43) for con-tinuous calibration of the instrument. The PCNs were identified by tracing two of the most intensive ions of isotope group. The instrumental detection limit (S/N ∨ 3) was approximately 0.001 pg for 1 μL splitless injection.

Several native standards (CN-2, CN-13, CN-27, CN-42, CN-52, CN-54, CN-64, CN-67, CN-70, CN-73, and CN-75) and technical Halowax 1014 together with 13C10-labeled standards were used to identify the elution pattern of PCN congeners. PCNs were quantified using 13C-labeled internal PCN standard on the assumption that the response was the same for each chlorine-substituted PCN group. The peak identification was subsequently per-formed by comparison between the peaks’ retention time and the appropriate PCN chromatographic data pub-lished[29-31]. The peaks of PCN congeners could be identi-fied by relative retention time compared with standards and were quantified if isotope ratio of the two monitored ions for each compound is within 15% of the theoretical value. 1.4 Quality Assurance/Quality Control

All analytical procedures were monitored using

solvents of pesticide residue grade with strict quality assurance and control measures. Before extraction, the whole Soxhlet apparatus were pre-extracted. For each batch of seven samples, a procedural blank was proc-essed to demonstrate free of contamination. No analyte was detected in the blanks. The average recoveries of 13C10-labeled PCN congeners CN-27, CN-42, CN-52, CN-67, CN-73, and CN-75 were 60.4%, 67.1%, 67.4%, 87.8%, 81.9%, and 75.2%, respectively. The limit of detection (LOD) was considered as a signal-to-noise ratio being three times greater than the average baseline variation. Detection limits for each congener ranged from 0.01 to 0.15 pg/g. The concentrations of PCN congeners in samples were destined for LOD values when they were lower than LOD values. 1.5 Organic Carbon Content

Total organic carbon (TOC) in dry sediments (pre-treated by passing 40 mesh screen) was determined by reaction with Cr2O7

2− and sulfuric acid. The remaining unreacted dichromate was titrated with FeSO4 using or-tho-phenanthroline as an indicator and organic carbon content was calculated by relevant formula. 1.6 Principal Component Analysis

Principal component analysis (PCA) was performed on several primary PCN congeners to explore the differ-ence among the profiles between the samples. Statistical analyses were carried out with SPSS 13.0 for Windows, release 13.0 (SPSS).

2 Results and Discussion

2.1 PCN Concentrations and Distributions The total PCN concentrations (sum of MoCNs to OCN congeners, PCNs) (Fig. 2, Table 1) ranged

from 34.3 to 303.0 pg/g (dry weight, dw) with a mean

Fig. 2 Total PCN concentration (C) (pg/g (dw) and ng/g (TOC)) in surface sediments samples of YTE and YRE


Table 1 Summary of statistical results of PCN concentration (C) in surface sediments samples from the YTE and YRE

/ ng g (dw)C −1 Congener RPF / ng g (dw)C −1 Congener RPF

Max. Min. Max. Min.

CN-2 1.8×10−5 16.0 ∧ 0.01 CN-46 — 2.03 ∧ 0.02

CN-1 1.7×10−5 44.3 ∧ 0.01 CN-31 — 0.12 ∧ 0.02

MoCNs 59.0 ∧ 0.01 CN-41 — 0.33 ∧ 0.02

CN-4 2.0×10−8 5.20 ∧ 0.02 TeCNs 130 0.30

CN-5/7 1.8×10−8 17.6 ∧ 0.02 CN-52/60 — 5.19 ∧ 0.04

CN-6/12 — 2.93 ∧ 0.02 CN-58 — 2.00 ∧ 0.04

CN-11/8 — 3.72 ∧ 0.02 CN-61 — 5.33 ∧ 0.04

CN-3 — 4.08 ∧ 0.02 CN-50 6.8×10−5 1.67 ∧ 0.04

CN-10 2.7×10-5 2.79 ∧ 0.02 CN-51 — 1.14 ∧ 0.04

CN-9 — 1.35 ∧ 0.02 CN-54 1.7×10−4 0.62 ∧ 0.04

DiCNs 36.9 ∧ 0.02 CN-57 1.6×10−6 1.83 ∧ 0.04

CN-20 — 1.53 ∧ 0.02 CN-62 — 2.39 ∧ 0.04

CN-19 — 17.2 ∧ 0.02 CN-53/55 — 2.03 ∧ 0.04

CN-21 — 0.82 ∧ 0.02 CN-59 — 1.37 ∧ 0.04

CN-24/14 — 14.2 ∧ 0.02 CN-49 — 0.43 ∧ 0.04

CN-15 — 1.29 ∧ 0.02 CN-56 4.6×10−5 0.20 ∧ 0.04

CN-16 — 0.81 ∧ 0.02 PeCNs 21.2 0.12

CN-17 — 1.51 ∧ 0.02 CN-66/67 2.5×10−3 9.73 ∧ 0.02

CN-13 — 2.51 ∧ 0.02 CN-64/68 1.0×10−3 15.6 ∧ 0.02

CN-22 — 6.99 0.04 CN-69 2.0×10−3 9.02 ∧ 0.02

CN-23 — 6.56 ∧ 0.02 CN-71/72 3.5×10−6 10.3 ∧ 0.02

CN-18 — 0.50 ∧ 0.02 CN-63 2.0×10−3 2.77 ∧ 0.02

TrCNs 42.2 0.14 CN-65 — 0.43 ∧ 0.02

CN-42 — 4.06 ∧ 0.02 CN-70 1.1×10−3 0.35 ∧ 0.02

CN-33/34/37 — 5.76 ∧ 0.01 HxCNs 47.9 0.06

CN-44 — 1.02 ∧ 0.02 CN-73 3.0×10−3 59.4 ∧ 0.04

CN-47 — 2.41 ∧ 0.02 CN-74 — 49.8 ∧ 0.04

CN-45/36 — 112 ∧ 0.02 HpCNs 109 ∧ 0.04

CN-28/43 — 2.39 ∧ 0.02

CN-27/30 — 1.04 ∧ 0.02

CN-75

(OCN) — 76.1 ∧ 0.05

CN-39 — 0.52 ∧ 0.02

CN-32 — 0.62 ∧ 0.02 PCNs 408 6.2

CN-48/35 2.1×10−5 1.62 ∧ 0.02 I-TEQ 0.24 0.0001

CN-38/40 8.0×10−6 3.91 ∧ 0.02 TOC/% 2.92 0.27

RPF: relative potency factor, summarized in Refs. [12,32-34]. “ ∧ ” means the value was below the LOD, which is 0.01 for MoCNs, 0.02 for DiCNs-TeCNs and

HxCNs, 0.04 for PeCNs and HpCNs, and 0.05 for OCN.


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value of 131.0 pg/g (dw) in the YTE surface sediments and 6.2-408.0 pg/g (dw) with a mean value of 78.7 pg/g (dw) in the YRE samples. As for the study of YTE sam-ples, levels at the sites near the south shore of YTE were elevated compared to other sites. In particular, the high

est level of PCNs (303.0 pg/g (dw)) was found at

C3 site, which is located near the mouth of Huangpu River, one of the main inputs to the YTE. Moreover, the site is also situated on the downstream of the west sewage dis-charge plant (Shidongkou, SDK) of Shanghai City.

This phenomenon was also observed with other contaminants, such as PCBs[35]. High levels were found in the samples of site C6 located near the south discharge plant (Bailonggang, BLG) and site C1, which was near the mouth of Baimao River. The concentrations of PCNs were lower at offshore site C2 and north of Chongming Island sites (C4 and C5) than that at the coastal stations possibly due to less human activities.

As regards the YRE samples, PCN concentra-tions were lower than 35.0 pg/g (dw) in about two-thirds of the samples of YRE. The level found in site H8 was so far the lowest, with only 6.2 pg/g (dw). However, at sites H3 and H11, the PCN concentrations were 408.0 and 315.0 pg/g (dw), respectively, about 50 times higher than

the lowest concentration (6.2 pg/g (dw)). These enrich-ments may be related to industrial activities such as the crude oil and other petrochemical production in the sur-roundings of these areas. For the influence of site H3, the PCN concentration of site H4, downstream of site H3, is higher than that in other sites, with a value of 110 pg/g

(dw). PCNs from a near-shore marine site (H15)

also has a relatively high level with the value of 84.8 pg/g (dw).

In comparison, the level of total PCNs in the present study was generally lower than those reported in other studies in the world (see Table 2). For example, slightly higher values were found in sediments in Venice and Orbetello lagoons of Italy (0.03-1.51 ng/g (dw))[10], Qingdao coastal sea in China (0.2-1.2 ng/g (dw))[28], To-kyo Bay in Japan (0.2-4.4 ng/g (dw))[7], and northern Baltic Sea (0.27-2.8 ng/g (dw))[36]. In general, the values mentioned above were all comparable to the background concentrations in sediments found in Europe, America, and Japan (about 1 ng/g (dw))[36]. However, extraordi-nary high levels have been found in the Trenton channel of the Detroit River[37] and near a former chlor-alkali plant[34], reflecting the particularly local sources in the regions.

Table 2 Summary of PCN concentrations in sediments from different countries

Countries and regions PCN homologue 1PCNs / ng g (dw)− Ref.

Northern Baltic Sea, Sweden tetra- to hepta-CNs 0.27-2.8 [36]

Venice and Orbetello lagoons, Italy mono- to octa-CNs 0.03-1.51 [10]

Gdañsk Basin, Baltic Sea, Poland tetra- to hepta-CNs 6.7 [16]

Baltic Sea, Sweden tetra- to hepta-CNs 0.14-7.6 [21]

Detroit River, America tri- to octa-CNs 1.23-8 200 [37]

A dated lake in northwest England tri- to hepta-CNs 0.5-11.5 [38]

Creek Spittelwasser, German penta- to hepta-CNs 2 540 [39]

Southeastern coastal Georgia, America tri- to octa-CNs 19 00-23 400 [34]

Tokyo Bay, Japan tri- to hepta-CNs 0.2-4.4 [7]

Qingdao coastal sea, China tri- to hepta-CNs 0.2-1.2 [28]

Laizhou Bay, China tri- to hepta-CNs 1-5.1 [40]

YTE and YRE, China mono- to octa-CNs 0.01-0.4 This study

The TOC in all samples on dw was measured with

the PCNs at the same time shown in Fig. 2. The TOC

concentrations ranged from 0.74 ng/g (TOC) at site H7

to 26.6 ng/g (TOC) at site H3, with a median value of

7.8 ng/g (TOC). According to correlation analysis, there was close correlation between the concentrations of

PCNs (ng/g (dw)) and PCNs (ng/g (TOC))

(R2=0.83), which indicated that PCN concentrations expressed on an organic carbon basis would have little difference on the results expressed on a dw basis. For samples of YRE, most of them have lower TOC(TOC＜1%), and this might be a further explanation for the


relatively low concentrations of PCNs in these sam-ples. 2.2 PCN Homologue and Congener Profiles

Profiles of PCN homologue groups (from MoCNs to OCN congeners) in the surface sediments collected from YTE and YRE are presented in Fig. 3, but homologue compositions of sites H7 to H9 are not included in this

figure because of their low concentrations ( PCNs ∧

15.0 pg/g (dw)). In general, two quite different homologue profiles

were obtained from Fig. 3. One PCN profile was domi-nated by lower chlorinated homologues such as MoCNs,

DiCNs, and TrCNs. In YTE samples C2, C4, and C5, DiCNs and TrCNs accounted for over 90% of the total PCNs. CN-5/7, CN-3 in DiCNs, and CN-24/14, CN-23 in TrCNs were the dominated congeners. In the YRE samples H5 and H12-H15, MoCNs-TrCNs contributed to the total PCNs even higher than 95%. CN-1 in MoCNs, CN-5/7 in DiCNs, and CN-19, CN-24/14 in TrCNs were the dominant congeners. Since MoCNs, DiCNs, and TrCNs have higher vapor pressure (2.1, 1.7, and 0.13 Pa, respectively)[41], the presence of these PCN homologues in this study might be the result of atmospheric deposi-tion and global fractionation[26].

Fig. 3 Profiles of PCN homologues in the surface sediments from YTE and YRE, except H5 and H7-H9 sites

In another profile, the main contribution was highly chlorinated homologues (TeCNs-OCN). Sites C1, C3, and C6 in YTE and sites H3, H4, and H11 in YRE be-longed to this profile. In sites C1, C3, and C6, dominant PCN homologues were HpCNs and OCN followed by HxCNs. In YRE samples, TeCNs was the dominant homologue with the contribution of 28.0%, 39.3%, and 41.3% in sites H3, H4, and H11, respectively, followed by HpCNs and OCN. Different from these results, in sediments from Qingdao coastal sea[28], the PCNs were dominated by TrCNs and TeCNs, and most of HpCNs and OCN were found to be less than the detection limit. In these six sediment samples, several dioxin-like con-geners, for example, CN-66/67, CN-64/68, CN-69, and CN-71/72 in HxCNs and CN-73 in HpCNs, are the most abundant congeners together with HpCN-74 and OCN-75 congeners. The congeners CN-66/67 and CN-73 in these six samples were more abundant than in Halowax mixtures, which indicated the contributions of

combustion sources[9,42]. Furthermore, in the present study, the ratio of CN-73/CN-74 in HpCNs was higher than 1. This phenomenon has also been reported before for contamination from combustion sources[21,39].

In addition, there is an interesting phenomenon in studying congener patterns of PCNs from YRE sediment samples. Contrary to its less abundance in sediments from YTE, CN-45/36, which were not dioxin-like congeners, seemed to be the most abundant congeners among all PCN congeners in most YRE sediment samples. Except for several samples (H8 and H12-H15), CN-45/36 accounted for 65%-94% of TeCNs and 22%-71% of the total PCNs. To our knowledge, such pattern was not observed in any other previous studies. This congener pattern was likely to be presented in the local source signatures, but more stud-ies were needed to investigate the distributions of PCNs in this local environment. 2.3 PCA Results

PCA was often used in analysis of environmental


85

samples in order to assess the potential emission sources. In this study, PCA based on the percentage of several

primary PCN congeners to PCNs was applied to the

total 21 samples. The two factors explain about 77.1% of the original variance in the data. The loading plot (Fig. 4a) and score plot (Fig. 4b) after varimax rotation were given in Fig. 4. Many highly chlorinated congeners had a strong positive correlation with PC1, particularly CN-52/60, CN-66/67, CN-64/68, CN-69, CN-71/72, CN-73, CN-74, and CN-75, and showed factor loadings higher than 0.8. CN-2/1 and CN-5/7 had negative values with PC1. The congeners related to PC2 can be divided into two groups. One group (CN-5/7, CN-3, CN-24/14, and CN-23) had highly positive values (above 0.6) with PC2, and the other group (CN-19 and CN-45/36) was under the left quadrant along the semicircle.

The sampling sites on the PCA score plot are shown

in Fig. 4b. As for YTE samples, all the six samples were

found on the positive coordinate side of PC2, but they

were separated into two clusters. The C1, C3, and C6

samples were more positively loaded along PC1, which

were characterized by high contributions of CN-52/60,

CN-66/67, CN-64/68, CN-69, CN-71/72, CN-73, CN-74,

and CN-75. The majority of these congeners were

founded as specific congeners in the fly ash and chlor-

alkali samples[30,34]. Therefore, this could be interpreted

as PCNs from combustion sources. As mentioned above,

the effects of river inputs and discharge from the waste

discharge plant might be helpful for the explanation.

Other sites (C2, C4, and C5) of YTE samples were

strongly positively loaded along PC2, which were more

influenced by some DiCN and TrCN congeners.

Most of the sites of YRE are located near the ori-

gin of PCA score plot but have a little variance on the

left side of PC1. The results reflected the low concen-

trations of PCNs in most of the sediments, as the origin

represents the mean concentrations of all samples. Sev-

eral outlying samples of YRE could be observed: four

samples (H3, H4, H7, and H11) were located on posi-

tively loaded of PC1 with higher chlorinated PCN con-

geners from the inputs of industrial activities around the

sampling sites, and two samples had more negative

loads of PC2 with high contents of CN-45/36, which

were the typical congeners of YRE samples, probably

due to proximity to some local potential emission

sources.

Fig. 4 Loading plot (a) and score plot (b) of PCA (PC1 and PC2) based on percentage of primary congeners’ concentrations for

sediment samples in YTE and YRE

2.4 PCN Toxic Equivalents

Although many PCN congeners have been tested

for their dioxin-like potency, the 2,3,7,8-TCDD toxic

equivalent (TEQ) factors (TEFs) of PCN congeners are

very limited. Only 22 of all 75 congeners have been

worked for dioxin-like toxicity and many of them do not

have an assigned TEF. Noma et al [32] and Alcock et al [33]

summarized the RPF values for PCNs from previous

reports. In this study, RPFs were used to calculate the

PCNs -TEQs. TEQ values of PCNs in the surface

sediments ranged from 0.000 1 to 0.24 pg TEQ/g (Table 1). Due to the lower toxicity and relatively lower PCN con-


centrations, TEQs of PCNs were also lower than that of other reports[28,34,40]. HpCN-73 is the predominant con-gener among the dioxin-like congeners of PCNs, with an average relative abundance of 60%, followed by HxCN- 66/67, HxCN-69, and HxCN-63 in most samples.

3 Conclusion

Based on the above work, the PCNs were ubiqui-tous contamination in the surface sediments at the YTE and YRE. Sediment concentrations and TEQs of PCNs were lower than those observed for riverine and coastal sediments in other countries. Total concentrations of PCNs were elevated in some samples from both YTE and YRE. Different PCN homologue and congener pro-files were also found in these samples. Especially, in the YRE samples, congeners of TeCN-45/36 contributed to the total PCNs and ranged from 22% to 71% in most samples from this region, which is notably larger than the others. This indicates the presence of some potential sources in this region, but this needs further investiga-tion.

Acknowledgment: The authors are grateful to Pro-

fessor Liu Zhengtao (Chinese Research Academy of En-vironmental Sciences) for providing sediment samples of the YRE.

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