Marine Pollution Bulletin 64 (2012) 2151–2159

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Marine Pollution Bulletin

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Distribution and contamination of heavy metals in surface sedimentsof the South Yellow Sea

Huamao Yuan, Jinming Song ⇑, Xuegang Li, Ning Li, Liqin DuanKey Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, PR China

a r t i c l e i n f o a b s t r a c t

Keywords:Heavy metalsEnvironmental assessmentSedimentsSedimentation fluxSouth Yellow Sea

0025-326X/$ - see front matter � 2012 Elsevier Ltd. Ahttp://dx.doi.org/10.1016/j.marpolbul.2012.07.040

⇑ Corresponding author. Tel./fax: +86 532 289 8583E-mail address: jmsong@qdio.ac.cn (J. Song).

The distributions, annual sedimentation and atmospheric deposition flux of heavy metals have beenstudied in sediments of the South Yellow Sea (SYS), in order to evaluate their levels and pollution status.The higher concentrations of heavy metals were generally found in the central part of the SYS, which maybe associated with the organic matters due to their high affinity to the metals. According to the calculatedenrichment factor (EF) of the studied metals, Cd in the sediments posed a high risk to local environments,while Mn, Hg, Pb and Zn were at moderate risk levels. Sedimentation fluxes study in the SYS showed thatmost heavy metals were deposited in the Chinese offshore. Annual dry deposition flux of these metalsindicated that the particulate heavy metals deposition via atmosphere also play an important role in bio-geochemical cycles in the SYS.

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1. Introduction

With the rapid industrialization and economic development incoastal region, heavy metals are continuing to be introduced toestuarine and coastal environment through rivers discharge, oce-anic dumping and aeolian processes (Kaimoussi et al., 2002). Thecontamination is especially significant in the estuarine and coastalsediments which usually act as a sink receiving the heavy metalsthrough adsorption onto suspended matter and subsequent sedi-mentation (Fang and Hong, 1999; Zwolsman et al., 1996). Accumu-lation of heavy metals occur in upper sediment in aquaticenvironment by biological and geochemical mechanisms and be-come toxic to sediment-dwelling organisms and fish, resulting indeath, reduced growth, or in impaired reproduction and lower spe-cies diversity (Praveena et al., 2007). Therefore, the evaluation ofmetal distribution in surface sediments is useful to assess pollutionin the marine environment.

The Yellow Sea is a typical epicontinental sea, bordered by Chi-na and the Korea Peninsula. It is separated from the Bohai Sea at itsnorthern extremity by the Shandong Peninsula, and from the EastChina Sea to the south by an arbitrary line connecting the north ofthe Yangtze River mouth with Cheju Island (Yang et al., 2003). TheShandong Peninsula separates the North Yellow Sea from the southYellow Sea (SYS). The SYS covers 309,000 m2, with an averagedepth of 46 m and a maximum depth of 140 m in the northern areaof Cheju Island.

ll rights reserved.

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Because industrial activity and automobile usage are increasingannually in the surrounding countries, the environment of the SYShas been affected by anthropogenic activities and populationgrowth, which receives billions of tons of particulate materialsannually from surrounding rivers (the Yellow River, Changjiang(Yangtze) River, and various Korean rivers). In addition to rivers,atmospheric inputs including dust and anthropogenic metals con-tribute greatly to the pollution of this sea (Choi et al., 2007). Metalcontamination of sediments has been reported in coastal areas ofthe Yellow Sea, however, the distribution and contamination statusof heavy metals for the whole SYS has not been established. In or-der to establish such knowledge, the present study investigates thespatial distribution of heavy metals in surface sediments of theSYS. In addition, based on the mass accumulation rates and the ele-ments contents both in sediments we studied and in atmosphericaerosols published in the literature for the SYS, the annual sedi-mentation fluxes and dry deposition flux of the studied metals inthe SYS are also estimated.

2. Sampling and methods

2.1. Study area

The Yellow Sea receives a vast amount of fresh water from bothChinese and Korean rivers, such as the Yangtze, Yellow, Yalu,Daliao and Haihe Rivers of China and the Han, Keum and YeongsanRivers of Korea (Qin et al., 1989). Two general circulation patternsin the Yellow Sea were reported as one counterclockwise gyre withnorthward inflow of the Yellow Sea Warm Current (YSWC) alongthe eastern margin, and a southward inflow of the Yellow Sea

0

5

10

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30

40

50

60

70

100

200

N

E

Fig. 1. Bathymetry and location of sediment sampling station in the South Yellow Sea. The arrows indicate the Yellow Sea Warm Current (YSWC), the Yellow Sea CoastalCurrent (YSCC), the Korea Coastal Current (KCC).

2152 H. Yuan et al. / Marine Pollution Bulletin 64 (2012) 2151–2159

Coastal Current (YSCC) along the west coast. In the eastern part,another clockwise gyre consists of the YSWC and a southward in-flow of the Korea Coastal Current (KCC) (Yang et al., 2003; Fig. 1).Thirty-three sample stations on four sections (A, B, C and D) weredesignated according to their latitude from 33�34.70 N to 36�55.50

N during a cruise onboard the Zhehaihuanjian (543T/G) from 12to 20 October, 2006 (Fig. 1). In the four sections, section A wasset to evaluate the influence of the Han River, and similarly, sectionD was for the Yangtze River.

2.2. Analytical method

Samples were taken with a stainless steel bottom sediment grabsamplers and frozen immediately at �20 �C. Approximately 50 g ofwet sample was freeze-dried, ground and homogenized with amortar and pestle. The processed sample was stored in acid-cleaned polypropylene tubes for further analysis. The bulksediment samples were divided into three sub-samples for thedeterminations of total organic carbon, heavy metals and grain sizeanalysis.

2.2.1. Total organic carbon analysisThe analytical procedure of the total organic carbon (TOC) mea-

surement in the sediment samples was according to Ryba withsome modification (Ryba and Burgess, 2002). Briefly, about 3 g ofa freeze-dried and pulverized sediment sample was treated with10% HCl to remove inorganic carbon, washed with deionized waterthree times, and dried overnight at 60 �C. The TOC content wasdetermined with an elemental analyzer (Perkin Elmer model2400).

2.2.2. Heavy metals analysisThe surface sediments were totally digested with mixed acid

solution (HNO3: HClO4: HF = 2:1:2) in a Teflon bottle with a screwcap and used microwave digestion system to remove any organicmatters presented in the sediment. Digested samples were broughtto a final volume of 100 ml using a solution of 1% nitric acid. Cop-per (Cu), cadmium (Cd), lead (Pb) and zinc (Zn) in sediments were

measured with inductively coupled plasma mass spectrometry(Perkin Elmer model, Elan 9000). Mercury (Hg) was measured witha gold amalgam mercury analyzer (Milestone model, DMA-80). Inaddition, the concentration of Al and Fe was analyzed by induc-tively coupled plasma-atomic emission spectrometry (Thermo IRISIntrepid II) to calculate the enrichment factor for each element.

Analytical quality assurance was performed by measurementsof the GBW-07314 reference material (The second Institute ofOceanography, the State Oceanic Administration of China. Therehas no certified value of Mn for GBW07314). The results were con-sistent with the reference values, and the differences were all with-in 8%. All plastic and glassware were pre-cleaned by soaking in 10%HNO3 (v/v) for at least 2 days, followed by soaking and rinsing withde-ionized water. All chemicals used in the experiment were guar-anteed reagent grade.

2.2.3. Sediment type and grain size analysisSediment type and grain size were analyzed with an X-ray auto-

matic grain size analyzer. The sediment samples were dried in theoven until their weights were consistent, and then weighed andnoted. The pretreated samples were placed into beakers withH2O2 solution (10%) added, in order to digest the organic matterin sediments. The excessive H2O2 solution was removed by wayof heating and evaporation. After that, 0.5% of sodium hexameta-phosphate was added to the samples, aiming at making the sedi-ments disperse completely, and then the mixture was analyzedwith an X-ray automatic grain size analyzer (SediGraphy 5100).The data issued from the weighing and analyses were statisticallytreated based on Momentum methods, and then the average grainsize and distribution ratio were calculated.

3. Results and discussion

3.1. Spatial distribution

The concentration ranges of TOC and heavy metals in surfacesediments of the SYS were as follows: TOC, 0.07–1.43%; Cu, 6.00–32.9 lg g�1; Mn, 152–1910 lg g�1; Cd, 0.06–1.54 lg g�1; Hg,

Table 1Concentrations of heavy metals in surface sediments at the study stations in the South Yellow Sea.

Station TOC (%) Al (%) Fe (%) Cu (lg g�1) Mn (lg g�1) Cd (lg g�1) Hg (lg g�1) Pb (lg g�1) Zn (lg g�1)

A1 0.38 5.43 5.21 15.0 / 0.75 0.006 39.3 244A2 0.98 4.43 3.24 12.3 1430 1.54 0.008 28.6 198A3 0.67 5.54 3.12 8.20 1030 0.26 0.011 20.6 54.8A4 0.73 5.83 2.75 14.2 782 0.39 0.020 15.0 49.1A5 0.50 5.50 2.45 11.5 607 0.22 0.022 12.5 48.4A6 0.54 5.78 2.88 13.9 660 0.21 0.031 13.2 51.1

B1 0.07 3.99 / / 152 0.06 0.008 6.20 24.6B2 1.12 6.35 3.43 17.7 395 0.20 0.013 20.6 85.0B3 1.43 7.13 3.78 32.9 381 0.32 0.062 21.3 109B4 1.01 7.24 4.27 24.7 462 0.37 0.051 21.9 128B5 1.17 7.46 4.57 25.5 826 0.21 0.069 23.6 116B6 1.19 7.75 4.69 26.5 1910 0.22 0.048 21.4 116B7 1.21 7.79 4.56 29.8 1550 0.33 0.053 23.1 110B8 0.63 5.83 3.28 17.4 1780 0.26 0.020 13.5 84.0B9 0.47 5.61 2.99 13.9 1420 0.23 0.013 10.4 78.4

C1 0.99 7.38 3.82 19.6 562 0.25 0.016 28.6 100C2 0.96 7.09 3.76 19.2 435 0.25 0.022 27.0 84.7C3 0.75 6.65 3.31 14.3 582 0.16 0.018 15.7 74.7C4 0.85 7.46 3.91 18.1 469 0.21 0.026 17.6 99.0C5 0.83 7.46 3.94 17.6 462 0.21 0.029 22.9 90.6C6 0.75 6.90 3.57 17.8 695 0.20 0.021 14.4 68.6C7 0.67 6.17 3.28 15.3 1380 0.18 0.010 29.0 76.5C8 0.43 5.69 2.84 11.5 1330 0.21 0.015 11.1 64.0C9 0.15 4.80 2.43 6.00 516 0.18 0.014 11.7 52.3

D1 0.94 6.79 3.96 13.5 675 0.28 0.015 12.0 129D2 0.92 7.11 4.14 19.2 654 0.55 0.025 15.4 202D4 0.82 7.31 4.06 18.5 543 0.25 0.021 14.0 105D5 0.75 7.27 3.97 18.4 671 0.22 0.023 16.9 98.1D6 0.41 6.31 3.21 14.5 504 0.26 0.016 14.1 79.8D7 0.39 5.61 3.01 13.1 525 0.20 0.018 9.70 56.5D8 0.24 5.32 2.44 9.70 532 0.16 0.028 7.90 50.8D9 0.28 5.8 2.73 14.2 528 0.26 0.022 10.4 71.2

H. Yuan et al. / Marine Pollution Bulletin 64 (2012) 2151–2159 2153

0.006–0.069 lg g�1; Pb, 6.20–39.3 lg g�1; Zn, 24.6–244 lg g�1; Fe,1.00–5.21% and Al, 3.99–7.79%, respectively (Table 1). The spatialdistributions of TOC and heavy metals are shown in Fig. 2. Higherconcentrations of TOC and heavy metals were generally found inthe central part of the SYS, especially the northern area in centralpart. Away from the central part area, concentrations (except forMn) decreased both in the Korean coast and Chinese coast direc-tion. The spatial distributions of heavy metals (except for Mn)and TOC in the SYS generally exhibited similar patterns and theconcentration of TOC correlated well with heavy metals (exceptsome individual stations for Fe, Cd, Pb and Zn) (Fig. 3). It is wellestablished that natural organic matter has a high affinity throughadsorption or complexation for heavy metals in the aquatic envi-ronment (El Bilali et al., 2002). As a consequence, it affects theeco-toxicity, environmental transfer and geochemical behavior ofheavy metal in the aquatic environment. The coupling betweenthe cycles of TOC and heavy metals is ultimately reflected in thechemical composition of marine sediments (Fang et al., 2009). Itis worthy mention that some heavy metals such as Cd, Pb and Znin station A1 and A2 (near Korean coast) are not correlated wellwith TOC in their relative analysis. The concentrations of thosemetals in station A1 and A2 were much higher than those in otherstations, in which the metals were probably influenced by anthro-pogenic activity.

It is also well established that grain size is one of the controllingfactors affecting natural concentrations of heavy metals in sedi-ments. Fine-grained sediments tend to have relatively high metalconcentrations due in part to the high specific surface area of thesmaller particles. This enrichment is mainly due to surface adsorp-tion and ionic attraction (Zhang et al., 2009). The sediment typeand mean grain size of surface sediments in different stations areshown in Table 2. In this study, we found that concentrations ofFe, Al and Hg were significantly correlated with mean grain size

(Fe, r2 = 0.252, P < 0.01, n = 31 (except A1); Al, r2 = 0.438,P < 0.001, n = 32; Hg, r2 = 0.231, P < 0.01, n = 32), indicating thatFe, Al and Hg concentrations are also controlled by the grain sizeto a certain extent.

In addition, the distribution of Mn showed a distinct way withTOC and other metals. The high value of Mn is located in the north-west part of the SYS and is generally decreasing towards the cen-tral part and both in eastern and southern direction. Thisdistribution was also reported by previous study (Zhao, 1993).The study has shown that the reason why Mn is not correlated wellwith TOC and grain size is mainly due to the source of Mn in sed-iments. It was argued that the origin of Mn in sediments is not onlyfrom terrestrial debris, but from biogenic matter. This fraction ofMn is liable to be deposited in coarse sediment with high oxygencontent to form MnO2nH2O. Another mechanism caused such dis-tribution of Mn is probably due to the sediment of this high con-tent area being dominated by biogenic carbonate (Fang et al.,2009; Lin et al., 2002). Previous studies have shown that dissolvedmanganese can become adsorbed on, or incorporated into, freshlyprecipitated CaCO3 in seawater. The relatively high content of car-bonate (5–10%) was found in the area with high content of Mn,which is mainly originated from the Yellow River but is alsostrongly influenced by the biogenic CaCO3 (Yang et al., 2003).

Based on the information of heavy metals, TOC and grain sizeabove, we performed hierarchical clustering analysis on the data.Distance metrics are based on the Euclidean distance single linkagemethod (nearest neighbor). As shown in Fig. 4, the concentrationsof Fe, Al, Cu and Hg are controlled by TOC as demonstrated by theirclose association with each other, in which Cu has the closest asso-ciation with TOC. However, the concentrations of Pb, Cd and Znhave not the close association with Fe, Al, Cu and Hg, indicatingtheir association with anthropogenic origin while Fe and Al areusually present in sediments in relatively high concentration under

120 121 122 123 124 125 126 127 128

Longitude (E)

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TOC (%)

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Al (%)

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Fig. 2. Spatial variation of heavy metals concentrations in the surface sediment in the study area of the South Yellow Sea.

2154 H. Yuan et al. / Marine Pollution Bulletin 64 (2012) 2151–2159

natural condition. It is also seen that grain size have the relativelong distance with the heavy metals, indicating the minor influ-ence of grain size on the heavy metals although Fe, Al and Hg havesignificant correlation with grain size as discussed above. Finally,Mn is not correlated well with other heavy metals, implying thedifferent geochemical behavior between Mn and other metals in

sediments. This is also consistent with our discussion above thatthe distribution of Mn showed a distinct way with TOC and othermetals.

The range and mean concentrations of studied metals in SYSand in other various continental shelves were summarized in Table3. It can be seen that the average concentrations of all studied

R2 = 0.666 (exclude A1)

0

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0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8TOC(%)

Fe(%

)

A1

R2 = 0.556

01

23

45

67

89

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8TOC(%)

Al(%

)R2 = 0.631

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0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8TOC(%)

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R2=0.217 (exclude A1 and A2)

0

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0.8

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Zn (µ

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D2A2

Fig. 3. Relationship between TOC and heavy metals.

H. Yuan et al. / Marine Pollution Bulletin 64 (2012) 2151–2159 2155

metals except Mn in SYS sediments were within the range found inother shelf areas. Among all the shelf areas chosen for comparison,the average concentration of Mn for SYS was the highest one. Asdiscussed above, higher concentrations of Mn maybe attributedto the relatively high content of carbonate in this area, where thedissolved manganese can be adsorbed on, or incorporated into,freshly precipitated CaCO3 in seawater.

3.2. Enrichment factors

Measurement of total concentration as a criterion to assess metalcontamination in the sediment environment is not satisfactory indiscriminating between natural and anthropic sources. The enrich-ment factor (EF) is widely used to estimates the anthropogenic im-pact on sediments based on the use of a normalization element (Al

Table 2Sediment type and mean grain size of surface sediments at the studied stations in theSouth Yellow Sea.

Station Contents (%) Mean grain size (Ø) Type

Sand Silt Clay

A1 96.75 2.55 0.70 1.87 SandA2 93.37 5.22 1.41 2.45 SandA3 92.83 5.49 1.68 2.60 SandA4 80.15 16.70 3.15 3.25 SandA5 56.58 36.84 6.58 4.44 Silty sandA6 23.29 67.02 9.69 5.30 Sandy silt

B1 95.94 3.18 0.88 2.03 SandB2 79.07 16.36 4.57 3.19 SandB3 83.51 13.71 2.78 2.34 SandB4 12.42 67.36 20.22 6.39 Clayey siltB5 7.38 76.56 16.06 6.35 SiltB6 9.08 74.74 16.18 6.34 SiltB7 0.01 77.68 22.31 7.01 Clayey siltB8 60.09 31.85 8.06 4.54 Silty sandB9 55.82 36.39 7.79 4.63 Silty sand

C1 69.42 22.96 7.62 3.93 Silty sandC2 39.60 44.91 15.49 5.31 Sandy siltC3 27.58 59.87 12.55 5.55 Sandy siltC5 0.73 78.77 20.5 6.84 Clayey siltC6 9.71 68.86 21.43 6.47 Clayey siltC7 73.39 20.5 6.11 3.66 Silty sandC8 71.09 24.53 4.38 3.51 Silty sandC9 59.43 36.32 4.25 3.81 Silty sand

D1 55.75 34.73 9.52 4.12 Silty sandD2 30.11 48.37 21.52 5.09 Clayey siltD4 13.37 66.44 20.19 6.42 Clayey siltD5 9.73 66.69 23.58 6.66 Clayey siltD6 48.61 41.9 9.49 4.56 Silty sandD7 9.09 76.94 13.97 5.87 SiltD8 32.91 59.25 7.84 4.84 Sandy siltD9 21.65 65.89 12.46 5.43 Sandy silt

2156 H. Yuan et al. / Marine Pollution Bulletin 64 (2012) 2151–2159

or Fe) in order to alleviate the variations produced by heterogeneoussediments (Adamo et al., 2005). The EF of heavy metals in the SYSsediment are calculated using the following equation:

EF ¼ ðM=AlÞS=ðM=AlÞR;

(M/Al)S and (M/Al)R are the ratio of metal to Al concentrations insample and in reference sample, respectively. For this calculation,

Fig. 4. Hierarchical clustering analysis of the relevant as

background values of the heavy metals in the SYS sediment are ta-ken from Lu and Zhu (1987) (for Cu, Cd, Hg, Pb and Zn) and fromZhao et al. (1995) (for Mn, Al and Fe). By convention, the range ofEF value of 0.5–1.5 indicates that heavy metal is entirely providedfrom crustal contribution (e.g. weathering product) in sediment,while values greater than 1.5 are considered to indicate an impor-tant proportion of non-crustal materials delivered from either nat-ural processes (e.g. biota contributions) and/or anthropogenicinfluences (Zhang and Liu, 2002). The EF range of the studied metalswere as follow: Fe, 0.8–1.8 (average 1.0); Cu, 0.5–1.7 (average 0.9);Mn, 0.3–2.9 (average 1.1); Cd, 0.8–19.6 (average 2.9); Hg, 0.4–3.4(average 1.3); Pb, 0.6–2.9 (average 1.1); Zn, 0.6–4.4 (average 1.4).The EF values of Fe and Cu are almost approaches to 1, which indi-cates a predominantly natural origin for those two elements in theSYS sediments. The EF values of Cd are the highest (almost greaterthan 1.5) and indicate a marked anthropogenic burden, suggestingthat Cd was the most contaminated metal among the studied met-als. In the case of Mn, Hg, Pb and Zn, their EF values are almost low-er than 1.5 with some exception of the values of greater than 2,suggesting moderate contamination in those exception stations. Inthe relative analysis between the heavy metals and TOC, we dis-cussed that the metals in stations A1 and A2 may be influencedby anthropogenic activity. The EF values of Cd, Pb, Zn and Fe in sta-tion A1 are 7.8, 2.9, 4.4 and 1.8, respectively, and are 19.6, 2.6, 4.3and 1.4 in station A2, respectively, which are much higher thanthose in other stations. As for Mn, the EF cannot be calculated inA1 due to the very high value founded in there, which is consideredas an anomalous value but the EF of Mn in A2 is 2.9 which is also thehighest value in all stations. That is further demonstrated that A1and A2 were contaminated by anthropogenic input.

3.3. Heavy metals sedimentation flux

The sedimentation rates in the SYS were comprehensively eval-uated by previous studies (Alexander et al., 1991; Zhao and Li,1991). Based on their data and heavy metals concentrations in sur-face sediment found in the present study, we can calculate the hea-vy metals sedimentation fluxes in the SYS. According to thedifferent sedimentation rates observed by Alexander and Zhao,the present study area is divided into three sections (I, II and III,

sociation among heavy metals, TOC and grain size.

Table 3Comparison of heavy metals concentrations in surface sediments of representative seas.

Location Cu Mn Cd Hg Pb Zn Reference

South Yellow Sea 6.0–32.9 152–1910 0.06–1.54 0.006–0.069 6.2–39.3 24.6–244 This study16.9 789 0.30 0.024 17.8 93.7

Coastal northern Bohai and Yellow Seas 0.53–35 ND 0.050–0.83 0.020–0.18 9.5–49 9.8–170 Luo et al. (2010)13 0.15 0.028 25 60

Coastal Bohai Bay 20.1–62.9 ND 0.12–0.66 ND 20.9–66.4 55.3–457.3 Gao and Chen (2012)38.5 0.22 34.7 131.1

East China Sea 4.3–42 152–1152 ND ND 10–49 18–114 Fang et al. (2009)15 484 27 60

South China Sea 5.29–122 ND 0.08–2.14 ND 4.18–58.7 10.7–346 Zhu et al. (2011)38.1 0.40 23.6 87.4

Shelf adjacent to Nazaré canyon 2.13–40 116–1323 <0.3–4.44 0.002–0.363 <2–69 25–206 Oliveira et al. (2011)16.8 341 0.311* 0.066 19.6 84

Southern California coastal shelf 1–166 ND <0.02–7.18 <0.005–0.580 0.9–77.7 6–294 Schiff and Weisberg (1999)15 0.33 0.050 10.9 59

Black Sea 1.9–107.6 ND 0.018–3.992 ND 0.5–50.3 1–185 Secrieru and Secrieru (2002)32.2 0.753 15 64.6

Northwestern Mediterranean 21.7 429 0.15 0.055 21.48 71.1 Heimbürger et al. (2012)

Eastern Aegean Sea 10.3–25.8 410–729 0.06–0.19 0.22–0.48 2.43–17.2 46.2–91.9 Uluturhan et al. (2011)18.51 562 0.107 0.331 10.49 71

ND: no data.* Survey 2007 data.

H. Yuan et al. / Marine Pollution Bulletin 64 (2012) 2151–2159 2157

Fig. 5). In section III, the high sedimentation rates (>18 mm yr�1) isseem to be an overestimate and then omitted because of the strongbiological mixing effect (Lim et al., 2007). Table 4 shows the area,the sedimentation rate, dry bulk density and the concentrationrange of heavy metals obtained in the present study and in eachsection.

There are three values for each metal-related parameter: mini-mum, maximum and average. The minimum value of the annualmetals sedimentation flux was calculated from the minimum con-centration of metals multiplied the minimum value of sedimenta-tion rates and then the minimum value of dry bulk density. Themaximum and average values were calculated in the similar man-ner. The average annual sedimentation fluxes of heavy metals inthe calculated area were as follow: Fe, 11300 � 109 g yr�1; Cu,5.4 � 109 g yr�1; Mn, 291 � 109 g yr�1; Cd, 83 � 106 g yr�1; Hg,8.3 � 106 g yr�1; Pb, 5.4 � 109 g yr�1 and Zn, 27.8 � 109 g yr�1.

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3.42.7

6.54.1 1.1 0.4

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III

III

Fig. 5. The different sedimentation rates (mm yr�1) according to Alexander et al.(1991) (+) and Zhao(1991) (N) and the divided three sections, as defined on thebasis of sedimentation rates.

Most of the sedimentation fluxes of heavy metals were concen-trated in section I, accounting for 69–85% of the total fluxes of eachmetal, which indicate that the suspended loads of metals in the SYSwere mostly exported from the Yellow and Changjing River anddeposited on the Chinese offshore. The sedimentation fluxes of sec-tion II are much lower than that of section I in spite of having thesimilar area. Although the flux in section III is lower than that ofsection I, the flux is not ignorable if considering its less than halfarea of section I.

It is known that ca. 90% of riverine sediments can be depositedin the coastal areas. Although at present, the Changjiang and theHuanghe Rivers do not directly empty into the Yellow Sea, theywere regarded to have governed the sedimentation of major partsof the Yellow Sea during Holocene (Yang et al., 2003). Table 5shows the annual flux of particles to the coast and their heavy me-tal contents both in Chinese and Korean rivers. Based on thosedata, the annual particulate heavy metal fluxes of these rivers wereestimated (Table 5). The suspended load of the Yellow and Chang-jiang River in Chinese are the major contributions and the threerivers in Korea, the Han, Keum and Yeongsan River, contributeminor inputs to the SYS. These riverine fluxes of particulate metalsare generally higher than the calculated sedimentation fluxes. Itcan be explained that the particles of the Changjiang and HuangheRiver are not all deposited into the Yellow Sea. Martin reported theactual flux of the Yellow River sediment to the Yellow Sea (Martinet al., 1993). They estimated about 6 � 106 tons yr�1 of the YellowRiver sediments were transported to the Yellow Sea via a neph-eloid layer across the Bohai Sea strait. If considering the actual fluxto the SYS, the value will be further small. Unfortunately, the actualflux of the Changjiang River to the SYS cannot be found in the lit-erature so that the actual annual particulate heavy metal flux ofthe Changjiang and Huanghe Rivers to the SYS cannot be estimatedaccurately.

3.4. Atmospheric heavy metals flux

Besides riverine input, atmospheric deposition is also an impor-tant metal input route to the coastal sea. The severe Asian dustfrom arid regions can be transported by northwest winds to the

Table 4The area, ranges of sedimentation rate, dry bulk density and metals concentration and annual sedimentation flux for each section of the South Yellow Sea.

Section Area(km2)

Sedimentation rate(mm yr�1)a

Dry bulk density(g cm-3)

Fe (%) Cu(lg g�1)

Mn(lg g�1)

Cd (lg g�1) Hg (lg g�1) Pb (lg g�1) Zn (lg g�1)

I 56500 1.6–8.6 (4.6) 0.73–1.14 (1.00) 2.43–4.69(3.40)

6.0–29.8(16.6)

462–1910(956)

0.163–0.334(0.221)

0.010–0.069(0.027)

7.9–29(15.8)

50.8–116(79.0)

II 50800 0.1–1.2 (0.7) 0.67–0.86 (0.76) 2.45–4.57(3.60)

8.2–32.9(18.3)

381–1030(591)

0.164–0.386(0.249)

0.011–0.069(0.029)

12.5–28.6(19.4)

48.4–128(86.2)

III 23300 0.3–3.9 (1.8) 0.60–1.12 (0.92) 3.12–5.21(3.85)

8.2–19.6(15.1)

152–1430(700)

0.056–1.540(0.486)

0.006–0.025(0.013)

6.2–39.3(21.4)

24.6–244(129.7)

Annual metals sedimentation flux (Cd and Hg in 106 g yr�1, all other in 109 g yr�1)I 1600–26000

(8800)0.4–16.5(4.3)

30–1060(248)

11–190 (57) 0.66–38 (7.0) 0.52–16(4.1)

3.3–64(20.5)

II 80–2400(970)

0.03–1.7(0.5)

1.3–54(16.0)

0.6–20 (7) 0.04–3.6(0.8)

0.04–1.5(0.5)

0.2–6.7(2.3)

III 130–5300(1500)

0.03–2.0(0.6)

0.6–146(27.0)

0.2–160 (19) 0.03–2.5(0.50)

0.03–4.0(0.83)

0.1–25(5.0)

Total 1800–33700(11300)

0.46–20.2(5.4)

31.9–1260(291)

11.8–370(83)

0.73–44.1(8.3)

0.59–21.5(5.4)

3.6–96(27.8)

a Data taken from Alexander et al. (1991) and Zhao and Li (1991).

Table 5The annual suspended load, the concentration of riverine particulate metals and annual transportation flux of particulate metals of the major Chinese and Korean rivers enteringto the seas.

River Suspended sediment load (106 tons yr�1)a Fe (%) Cu (lg g�1) Mn (lg g�1) Cd (lg g�1) Pb (lg g�1) Zn (lg g�1)

Riverine particulate metals conc. (Fe in %; all others in lg g�1)Chinese rivers b Yellow River 495 3.72 26.7 767 0.18 16.5 69.8

Changjing River 345 5.2 62.3 811 0.44 39.9 97.7

Korean rivers c Han River 12.4 4.81 46.3 2005 42.5 209Keum River 3.95 5.35 53.6 1266 46.1 163Yeongsan River 1.24 4.54 39.1 927 35 130

Annual flux (109 g yr�1)Chinese rivers Yellow River 18,400 13.2 380 0.089 8.17 34.6

Changjiang River 17,900 21.5 280 0.152 13.8 33.7

Korean river Han River 596 0.574 24.9 0.527 2.59Keum River 211 0.212 5.00 0.182 0.644Yeongsan River 56.3 0.0485 1.15 0.0434 0.162

Total flux (109 g yr�1) 37,163 35.5 691 0.241 22.7 71.7

a Data taken from Yang et al. (2003).b Data taken from Zhang and Liu (2002).c Data taken from Yang et al. (2003).

Table 6The dry deposition fluxes of the heavy metals to the Yellow Sea.

Annual flux (mg m�2 yr�1) Fe Cu Mn Cd Pb Zn

Zhang et al. (1993) 2918 12.4 36.2 17.3 29.0This study 2252 21.1 63.6 2.3 130 213Studied area (109 g yr�1) 294 2.76 8.31 0.30 17.0 27.8

2158 H. Yuan et al. / Marine Pollution Bulletin 64 (2012) 2151–2159

China seas and may have a significant impact on the biogeochem-ical cycles of heavy elements. Zhang and Gao (2007) analyzed theeffect probability of Asian dust deposition in China seas and theprobabilities to the Yellow Sea were 20.2%, 39.5% and 33.0% inthe year 2000, 2001 and 2002, respectively. The total amount ofdry deposition to the Yellow Sea was about 17.9 Tg yr�1. Annualwind-dust flux to the Yellow Sea accounts for 20–70% of the totalinput of mineral materials to the Yellow Sea (Gao et al., 1992). Sucha large aeolian matter supply can considerably change the geo-chemical composition of the Yellow Sea sediment, particularlyfor some transition metals (Gao et al., 1992; Yang et al., 2003).Zhang et al. (1993) also reported that the high flux of particulateheavy metal deposition to the Yellow Sea via the atmospherewas attributed to the important wind-dust deposition and atmo-spheric pollution.

Hao et al. (2007) and Zhang et al. (2001) analyzed various ele-ments in the atmospheric aerosol and aerosol concentration inQingdao, respectively, which is in the transport path of the stormsmoving to the Yellow Sea and is thus an ideal site to monitor thecomposition, transportation and deposition of the ions, metalsand minerals in the aerosols and its adjacent sea, the Yellow Sea.Based their data and the annual dry deposition flux to the YellowSea reported by Zhang and Gao (0.13 g m�2 d�1; 2007), we

estimated the atmospheric deposition flux of heavy metals to theYellow Sea and compared with the data presented by Zhanget al. (1993) (Table 6). The annual dry deposition flux of heavy met-als to the Yellow Sea were as follows: Fe, 2252 mg m�2 yr�1; Cu,21.1 mg m�2 yr�1; Mn, 63.6 mg m�2 yr�1; Cd, 2.3 mg m�2 yr�1;Pb, 130 mg m�2 yr�1 and Zn, 213 mg m�2 yr�1. Except Fe, thefluxes of other heavy metals were higher than that presented byZhang et al. (1993). Owing to the increasing intensity of anthropo-genic activity, the frequency and scale of dust events giving rise todust storm aerosols has increased rapidly in the east Asian regionsince 2000 (Mori et al., 2003). The higher flux also reflected theincreasing effect of anthropogenic activities on the transport ofmaterials via the atmosphere to the Yellow Sea. Based on this data,we also estimated the aerosol dry deposition fluxes of these metals

H. Yuan et al. / Marine Pollution Bulletin 64 (2012) 2151–2159 2159

to the studied area (Table 6). The aerosol dry deposition fluxes ofthese metals (except Cd) are relatively small when comparing withthe riverine annual fluxes. However, the significance of particulateheavy metals deposition to the Yellow Sea via the atmosphere can-not be neglected as the actual riverine flux is much smaller thanthe calculated value, as mentioned above.

4. Conclusions

Analyses of heavy metals (Cu, Mn, Cd, Hg, Pb and Zn) from theSYS surface sediments showed that the higher contents of heavymetals were generally found in the central part of the SYS andthe contents decreased both in Korean and Chinese offshore area.The spatial distributions of heavy metals generally exhibited simi-lar patterns with TOC and their concentration correlated well withTOC, suggesting that their distributions were significantly influ-enced by natural organic matters due to their high affinity to themetals. Enrichment factors analysis suggested that anthropogenicinfluence on the environment has been significant in the case ofCd, while Mn, Hg, Pb and Zn were at moderate risk levels. In addi-tion, although the contents of heavy metals decreased in Koreanoffshore area, the EF values of Cd, Pb, Zn, Mn and Fe in northernKorean offshore area are much higher than those in other stations,which demonstrated that this area were contaminated seriously byanthropogenic input.

According to the different sedimentation rates obtained by pre-vious studies, the studied area of the SYS is divided into three sec-tions and the annual sedimentation fluxes of heavy metals in eachsection were estimated. It was found that most of the sedimenta-tion fluxes of heavy metals were deposited in the Chinese offshore,accounting for 69–85% of the total fluxes of each metal. Annual drydeposition flux of these metals indicated that the particulate heavymetals deposition via atmosphere also play an important role inbiogeochemical cycles in the SYS.

Acknowledgments

This study was financially supported by the National Key Pro-ject for Basic Research of China (No. 2011CB403602), the NationalNatural Science Foundation of China (Grant No. 40906056), theFoundation for Innovative Research Groups of the National NaturalScience Foundation of China (No. 41121064) and the KnowledgeInnovation Program of the Chinese Academy of Sciences (KZCXZ-YW-Q07-02).

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