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Heavy metal contamination in western Xiamen Bay sedimentsand its vicinity, China

Luoping Zhang a, Xin Ye a, Huan Feng b,*, Youhai Jing a, Tong Ouyang a, Xingtian Yu c,Rongyuan Liang c, Chengtie Gao c, Weiqi Chen a

a State Key Laboratory of Marine Environmental Science, Environmental Science Research Center, Xiamen University, Xiamen, Fujian 361005, PR Chinab Department of Earth and Environmental Studies, Montclair State University, Montclair, NJ 07043, USA

c Xiamen Environmental Monitoring Station, Xiamen, Fujian 361004, PR China

Abstract

Concentrations of selected heavy metals (Cu, Pb, Zn, Cd, Cr, Ni and Fe) in surface sediments from nine sites in western Xiamen Bayand its vicinity were studied in order to understand current metal contamination due to urbanization and economic development in Xia-men, China. The sediment samples were collected in December 2004 and July 2005 respectively in order to examine temporal variations.In this study, we found that heavy metal concentrations in surface sediments sampled in the western Xiamen Bay and adjacent MaluanBay and Yuandang Lagoon varied from 19 to 97 mg kg�1 for Cu, 45 to 60 mg kg�1 for Pb, 65 to 223 mg kg�1 for Zn, 0.11 to1.01 mg kg�1 for Cd, 37 to 134 mg kg�1 for Cr, 25 to 65 mg kg�1 for Ni and 3.08 to 4.81% for Fe. Although all metal concentrationsin sediments meets Chinese National Standard Criteria for Marine Sediment Quality, both metal enrichment factors (EF) and geoaccu-mulation index (Igeo) show that Pb contamination exists in the entire study area and contamination of other metals are also present insome locations depending on the sources, of which sewage outlets and commercial ports are the main sources of contaminants to thearea. This study shows that using the sediment quality standard criteria only to assess sediments cannot properly reflect sediment con-tamination. A multiple approaches should be applied for the sediment quality assessment.� 2007 Elsevier Ltd. All rights reserved.

Keywords: Xiamen Bay; Sediment; Heavy metals; Contamination; Sewage sludge; Sediment quality criteria

1. Introduction

With the rapid industrialization and economic develop-ment in coastal region, heavy metals are continuing to beintroduced to estuarine and coastal environment throughrivers, runoff and land-based point sources where metalsare produced as a result of metal refinishing by products.Therefore, heavy metal contamination is still an environ-mental problem today in both developing and developedcountries throughout the world. Western Xiamen Bay(24�29 0N, 118�04 0E) is a semi-enclosed bay in southeastChina and within the Xiamen Economic Special Zone thatwas created in 1980. The water depth ranges from 6 to 25 m

with a deep-water coastline of about 30 km. Thus, it has anexcellent natural condition for navigation and shippingactivities. Although the economic development in XiamenEconomic Zone speeds the urbanization and industrializa-tion of the region, promotes the prosperous of the area andraises the living standards of residents, it also brings envi-ronmental problem to the region. The rapid developmentof the Xiamen Economic Special Zone in past 25 yearshas resulted in great environmental stress to western Xia-men Bay and its adjacent areas. With the expansion ofXiamen Harbor, navigation channel dredging in westernXiamen Bay has been operated every year since 1993. Inthe meantime, the municipality of Xiamen City has decidedto restore the ecosystem of man-made lagoons adjacent towestern Xiamen Bay. Therefore, more than 2 · 107 m3 sed-iment will be dredged at the end of the project. Currently, a

0025-326X/$ - see front matter � 2007 Elsevier Ltd. All rights reserved.

doi:10.1016/j.marpolbul.2007.02.010

* Corresponding author. Tel.: +1 973 655 7549; fax: +1 973 655 4072.E-mail address: fengh@montclair.edu (H. Feng).

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Marine Pollution Bulletin 54 (2007) 974–982

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certain amount of dredged materials are dumped to off-shore outside of Xiamen Bay. As the sediment could havecontamination problem, this operation has raised environ-mental concerns around the dumping site.

Although several sediment contamination studies haveconducted in Xiamen Bay recently, these studies are mainlyfocused on organic contaminants (e.g., Chen et al., 2002;Hong et al., 1995; Klumpp et al., 2002; Maskaoui et al.,2002, 2005; Ou et al., 2004; Zhou et al., 2000). There isalmost no information available from the published litera-tures discussing metal contamination in western XiamenBay sediments in recent 10 years or so, although thereare few studies in the adjacent Xiamen Sea (e.g., Honget al., 1995, 2003). How to properly assess the sedimentquality is an important issue related to the regional eco-nomic development. In 2002, China enforced MarineSediment Quality (GB 18668-2002) to protect marine envi-ronment (CSBTS, 2002). Therefore, Marine SedimentQuality (GB 18668-2002) is used as a general measure ofmarine sediment contamination in China. The same prac-tice can be also found in other countries and regions, suchas USA and Hong Kong, and has been discussed (e.g.,Chapman et al., 1999; DiToro et al., 1991; EPA/USACE,1998). The purpose of this study is to investigate currentmetal distributions and concentrations in the western Xia-men Bay sediments and its adjacent areas, examine theenvironmental status and impact after 25 years urbaniza-tion and economic development in the area, and updatethe information for effective environmental managementin the region.

2. Methods

Field samplings for surface sediments (<5 cm) were con-ducted in December 2004 and July 2005, respectively, inorder to examine if there is a significant temporal variationof metal concentrations and distribution. The sampling sta-tions in western Xiamen Bay, Maluan Bay and YuandangLagoon are shown in Fig. 1. Stations X1–X6 consist of twotransects along the axis of Xiamen Bay and the inner bay,of which Stations X1 and X2 are in the open main channelof western Xiamen Bay with water depths of 16 m and18 m, respectively. Stations X3 and X4 are near DongduPort, where is a commercial port. Water depths at StationsX3 and X4 are 10 m and 14 m, respectively. Station X5 islocated next to the outlet of the Sewage Treatment Plantof Xinlin Industrial Area. Water depth at this station is8 m. Station X6 is in the inner bay with water depth of4 m. Stations M1 and M2 are in Maluan Bay that is aman-made lagoon created in 1960s and situated in thesouthwest of Xinlin Industrial Area. Water depths at Sta-tions M1 and M2 are 2 m and 1.5 m, respectively. StationsY1 and Y2 are in Yuandang Lagoon that is located in thenorth of downtown area of Xiamen city, surrounded by thenewly developed urban area, and once served as a mainmunicipal sewage-accepting lagoon. There are still smallamount of sewage discharged into the lagoon nowadays

although most sewage has been intercepted into urban sew-age treatment system. We did not get any sediment sampleat Station Y1 because of too many shell hashes in the bot-tom that prevented us from getting sediment samples.Water depth at Station Y2 is 1.5 m.

As soon as the field work was finished, sediment sampleswere carefully shipped to and processed and preserved atState Key Laboratory of Marine Environmental Scienceat Xiamen University. Subsamples for trace metal analysiswere initially dried naturally in the air in a controlled cleanenvironment for a week. Then, the samples were trans-ferred to an oven and dried at 40 ± 2 �C. The samples werethen ground to a powder with a mortar and pestle, sievedthrough a 80 meshes sieve and kept in a pre-cleaned con-tainer for future use. Total digestion of an aliquot of�0.25 g sediment samples was performed in Teflon beakersusing 9 ml HNO3 + 3 ml H2O2 + 1 ml HF at 180 �C in aclosed system for 12 h. The completely dissolved sampleswere then diluted to 20 ml for further analysis. Samplesolutions and reagent blanks were analyzed for metals ofinterest using Agilent 7500 ICP-MS at Xiamen Environ-mental Monitoring Station. Background correction andmatrix interference were monitored throughout the analy-ses. All the sediment samples were analyzed in duplicates.The analytical precisions were better than 10%. To monitorthe quality of chemical analysis and examine the accuracyof the data, soil reference materials, GB ESS1 and GBESS2 issued by State Oceanographic Administration ofChina, were analyzed with the sediment samples duringthe course of analysis. The analytical concentrations ofthe selected metals of interest are listed in Table 1. It is seenthat our analytical values are within the range of the certi-fied values of the reference materials.

3. Results and discussion

As shown in Table 2, metal concentrations in the surfacesediments from the two samplings show a general consis-tency except for few elements in a few stations (e.g., Cuat station Y2, Zn at stations X6 and M2). The differencescould be attributed to temporal variations of contami-nant source input. However, we do not exclude the possi-bility of spatial variations of metal distributions in thesediments. In this study, we found that heavy metal con-centrations in surface sediments of our study area variedfrom 19 to 97 mg kg�1 for Cu, 45 to 60 mg kg�1 for Pb,65 to 223 mg kg�1 for Zn, 0.11 to 1.01 mg kg�1 for Cd,37 to 134 mg kg�1 for Cr, 25 to 65 mg kg�1 for Ni and3.08% to 4.81% for Fe.

It is well-established that granulometry and organicmatter contents are important controlling factors in theabundance of trace metals in natural environment. Fine-grained sediments tend to have relatively high metal con-tents, due in part to the high specific surface of the smallerparticles. This enrichment is mainly due to surface adsorp-tion and ionic attraction (McCave, 1984; Horowitz andElrick, 1987). Also, organic matter on particles is prevalent

L. Zhang et al. / Marine Pollution Bulletin 54 (2007) 974–982 975

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Table 1Results of analytical values of the soil standard reference materials (GB ESS1 and GB ESS2) in comparison with the certified reference values

Metals GB ESS1 soil reference material GB ESS2 soil reference material

Reference value Analytical value Reference value Analytical value

Cu (mg kg�1) 20.9 ± 0.8 20.5 ± 0.6 27.6 ± 1.0 28.3 ± 0.3Pb (mg kg�1) 23.6 ± 1.2 23.1 ± 0.1 24.6 ± 1.0 24.2 ± 0.6Zn (mg kg�1) 55.2 ± 3.4 56.2 ± 1.4 63.5 ± 3.5 60.4 ± 1.4Cd (mg kg�1) 0.083 ± 0.011 0.080 ± 0.006 0.041 ± 0.011 0.041 ± 0.012Ni (mg kg�1) 29.6 ± 1.8 27.1 ± 3.5 33.6 ± 1.6 35.8 ± 0.0Cr (mg kg�1) n.a. 75.9 ± 4.6 73.0 ± 0.4Fe (%) n.a. 4.98 ± 0.12 4.76 ± 0.13

ESS2 was analyzed with the samples from the first sampling (December 2004) and ESS1 was analyzed with the sediment samples from the second sampling(July 2005).

Fig. 1. Map showing the study area and sampling locations.

976 L. Zhang et al. / Marine Pollution Bulletin 54 (2007) 974–982

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in fine-grained sediments, and the biofilm binds a variety oftrace elements (Wangersky, 1986). In this study, we did notanalyze particle grain size distribution and organic mattercontent in the sediments, but we analyzed these parametersfor the sediments from our previous samplings (particlegrain sizes analysis for samples from the 2001 samplingand total organic carbon (TOC) analysis for samples fromthe 2003 sampling) in the same area and the data are tab-ulated in Table 2 along with other parameters as references.Comparing these particle grain size and TOC data with ourprevious data (L. Zhang unpublished data), no significantchanges have been found.

The relationships of Fe and TOC with median grain sizeare shown in Figs. 2 and 3. Except Stations X5 and Y2, Feconcentration linearly increases with increase of U valuesof median grain size (Fig. 2). The factors causing StationsX5 and Y2 deviate from the linear trend could be attrib-uted to localized sediment composition. For example, thereis a razor clam aquiculture farm about 300 m south of Sta-tion X5. Clam shell hash can affect Fe concentration in thesediments. In a relationship between TOC and grain size,except Station X5 that falls off the trend line possibly dueto razor clam aquiculture farm nearby, TOC concentrationshows a decrease with the increase of the U value of mediangrain size (Fig. 3). Stations that have local sewage input,such as Maluan Bay and Yuandang Lagoon, have rela-tively high TOC concentration, suggesting anthropogenicinfluence.

Metal contaminant sources to the western Xiamen Bayand adjacent areas should include land-based point andnon-point input, riverine/stream discharge and atmo-spheric fallout. Studies on atmospheric inputs to Chinasea have become a new focus of biogeochemical cycle inthe past few years (e.g., Gao et al., 2002). However, thisinformation of atmospheric fallout to the study area ismissing based on our literature review. As the western Xia-men Bay area is within the coastal region, we expect theland-based influence should be more predominant.

In order to explore the possible associations betweenthese variables, we performed simple statistical analysison the data. Pearson’s correlation coefficient matrix amongCu, Pb, Zn, Cd, Ni, Cr, Fe and TOC concentrations in sed-iments of western Xiamen Bay are presented in Table 3.Although not statistically significant, metal contaminants(Cd, Cr and Ni) show negative correlation with Fe exceptPb that shows low positive linear correlation with Fe, sug-gesting these heavy metal concentrations are not stronglycontrolled by natural weathering processes. Except Pb thatshows statistically insignificant negative correlation withTOC, the rest of heavy metal contaminants (Cu, Cd, Cr,Ni and Zn) show a low positive correlation with TOC. Thiscould suggest that these metal contaminants have low asso-ciation with organic matter. Significant correlation betweenNi and Cr (n = 9, r = 0.749) indicate Ni and Cr source con-tamination and significant correlation between Zn and Cucould suggest Zn and Cu source input. In most cases, how-ever, there are no significant correlations among theseT

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metals, suggesting that these metals are not associated witheach other and the relationship doest not exist betweenthese variables. Furthermore, these metals could have dif-ferent anthropogenic and natural sources in sediments ofthe western Xiamen Bay and its vicinity. These patternsmay also reflect the main anthropogenic discharges to thewestern Xiamen Bay, Maluan Bay and Yuandang Lagoonthat constitute a source for several heavy metals, beingYuandang Lagoon the most noticeable point for these dis-charges (Table 2).

We compared the metal concentrations from our studywith that of previous studies in Xiamen and other regions

and found that the present metal concentrations in XiamenBay and its vicinity are comparable to that found in PearlRiver (China) and Shenzhen Bay (China), slightly higherthan that in Jiaozhou Bay (China) and significantly lowerthan that in other larger industrialized/urban ports in theworld such as New York/New Jersey Harbor (USA) (Table4). We also compared our metal concentrations againstMarine Sediment Quality (GB 18668-2002) that was issuedby China State Bureau of Quality and Technical Supervi-sion (CSBTS) in order to prevent and control marine sed-iment pollution, protect the marine life and resource, takeadvantage of marine resource sustainable use, maintainmarine ecological equilibrium, and protect human health.GB 18668-2002 has three standard criteria for marine sed-iments. The primary sediment standard criteria, which isthe most strict, is applied to protecting habitats for marinelife including natural, rare and endangered species as wellas places for human recreation and sports. The secondarystandard criteria are applied to regulating general indus-trial use and coastal tourism; and the tertiary standard cri-teria are for defining harbors and special use for oceanexploration. Referring to GB 18668-2002, the overall aver-age concentrations of all selected heavy metals in sedimentsfrom western Xiamen Bay, Maluan Bay and YuandangLagoon meet the primary standard criteria (Table 2). How-ever, as shown in Table 2, there are significant spatial andtemporal variations in the metal concentrations, of whichsome exceed the primary standard criteria. Nevertheless,all metal concentrations meet the secondary standard crite-ria at all the stations. Therefore, with respect to the sedi-ment quality criteria a general conclusion could be drawnthat sediments in western Xiamen Bay and its adjacentareas have been contaminated by certain metals, but thesediment quality has not been significantly impactedby metal pollution based on the pollution definition (GES-AMP, 1973) that states that ‘‘Marine pollution is theintroduction, by man, of substances into the marine envi-ronment resulting in such deleterious effects as harm to liv-ing resources, hazards to human health, hindrance tomarine activities including fishery, impairment of qualityfor the use of sea water and reduction of amenities’’.

However, the purpose of our study is to understand thecurrent environmental status and the extent of metal con-tamination with respect to natural environment. Therefore,other approaches have to be applied besides just using thesediment quality criteria.

Commonly, geochemical normalization of the heavymetals data to a conservative element such as Al and Feis employed in order to identify anomalous metal concen-tration. In our case, we use metal enrichment factor (EF)as an index to evaluate anthropogenic influences of heavymetals in sediments, we can reasonably evaluate the metalcontamination in the area. Enrichment factor (EF) is com-monly defined as the observed metal to aluminum (Al)ratio in the sample of interest divided by the backgroundmetal/Al ratio because Al is one of the most abundantelements on the earth and usually has no contamination

Fig. 2. Correlation of Fe concentration with median particle diameter.Except Stations X5 and Y2, Fe concentration shows an linear increasewith the increasing U values of particles, suggesting higher Fe concentra-tion from lithegenic origin is associated with smaller particles.U = �log2D, where D is diameter of particle in mm. Stations X5 andY2 are excluded from linear regression.

Fig. 3. Correlation of total organic carbon (TOC) concentration withmedian particle diameter. Except Station X5, TOC concentration showsan linear decrease with the increasing U values of particles. U = �log2D,where D is diameter of particle in mm. Station X5 is excluded from linearregression.

978 L. Zhang et al. / Marine Pollution Bulletin 54 (2007) 974–982

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pyconcern and has been widely used by many researchers tostudy the sources and contamination of trace metals in riv-erine, estuarine and coastal environment (Windom et al.,1989, 1991; Zhang and Liu, 2002; Feng et al., 2004). Itcan indicate whether the metals are from natural weather-ing processes of rocks or from anthropogenic sources andreflect the status of environmental contamination. Theassessment criteria are generally based on the EF values.If an EF value is between 0.5 and 1.5 (i.e., 0.5 6 EF 6 1.5),it suggests that the trace metals may be entirely from crus-tal materials or natural weathering processes (Zhang andLiu, 2002). However, if a value of EF is greater than 1.5(i.e., EF > 1.5), it suggests that a significant portion oftrace metal is delivered from non-crustal materials ornon-natural weathering processes. Instead, the trace metalsare provided by other sources, e.g., point and non-pointpollution sources and biota (Klerks and Levinton, 1989;Zhang and Liu, 2002).

In this study, we did not analyze Al concentration in thesediments. Therefore, we can not use Al to calculate metalenrichment factor. In stead, we used Fe to calculate theenrichment factor. The reason is besides Al is one of themost abundant elements on the earth Fe is also an abundantelement in the structure of clay minerals and is also associ-ated with particle surfaces as oxide coatings. Iron (Fe) in theestuarine sediment is mainly from natural weathering pro-cesses and has been broadly used to normalize the metalconcentrations in order to reduce particle grain size influ-

ence because variations in Fe concentration could beexplained by particle grain size differences, with fine-grainedsediments having high Fe concentrations (e.g., Daskalakisand O’Connor, 1995; Feng et al., 1998). In addition, a sig-nificant linear correlation (n = 200, r = 0.799) betweenAl2O3 and Fe2O3 was found in Xiamen Harbor surface sed-iments (Shen, 1992). Therefore, we believe it is reasonable touse Fe to calculate metal enrichment factor. In fact, severalauthors have successfully used iron to normalize heavy met-als contaminants (Feng et al., 1998; Schiff and Weisberg,1999; Baptista Neto et al., 2000; Mucha et al., 2003).According to Ergin et al. (1991) the metal enrichment factor(EF) is defined as follows:

EF ¼MeFe

� �Sample

MeFe

� �Background

ð1Þ

where (Me/Fe)Sample is the metal to Fe ratio in the samplesof interest; (Me/Fe)Background is the natural backgroundvalue of metal to Fe ratio. As we do not have metalbackground values for our study area, we adopt the valuesfrom crust material, which gives 32 mg kg�1 for Cu,16 mg kg�1 for Pb, 127 mg kg�1 for Zn, 0.2 mg kg�1 forCd, 71 mg kg�1 for Cr, 50 mg kg�1 for Ni and35900 mg kg�1 for Fe (Martin and Whitfield, 1983).

Because we do not have Fe concentration for the sam-ples from the July 2005 sampling, we can not performenrichment factor calculations for this sampling. However,

Table 4Comparison of metal concentrations in the sediments in the study area with that in other regions of the world

Region Cu Pb Zn Cd Cr Hg Ni Reference

Western Xiamen Bay (China) 44.0 50.0 139 0.33 75 – 37.4 This studyWestern Xiamen Bay (China) 24.8 64.1 618 – – – 44.9 Chen et al. (1987)Western Xiamen Bay (China) 30.0 75.6 215 0.20 – 0.091 – Chen et al. (1992)Western Xiamen Bay (China) 30.2 77.2 144 0.70 – – – Liu et al. (1995)Peral River Estuary (China) 39.0 59.4 111 0.34 56 1.4 – Liu et al. (2002)Shenzheng Bay (China) 48.8 46.0 135 – – – 29.9 Huang et al. (2003)Jiaozhou Bay (China) 27.3 30.9 – 0.15 – 0.08 – Xu et al. (2005)New York Harbor (USA) 105–131 109–136 188–244 1–2 175 2–3 33–40 USEPA et al. (1999)Bremen Harbor (Germany) 87 122 790 6.0 131 0.3 60 Hamer and Karius (2002)Izmir Harbor (Turkey) 182 97 182 6.2 108 – 222 Filibeli and Yilmaz (1995)Boston Harbor (USA) 67 86 118 – 131 – – Bothner et al. (1998)

Concentrations in mg kg�1.

Table 3Correlation matrix of the data

Variables TOC Cu Pb Zn Cd Ni Cr Fe

TOC 1.000Cu 0.411 1.000Pb �0.354 �0.315 1.000Zn 0.482 0.802 0.181 1.000Cd 0.507 0.077 0.165 0.457 1.000Ni 0.401 0.344 �0.898 �0.026 �0.024 1.000Cr 0.036 0.481 �0.624 0.060 �0.335 0.749 1.000Fe �0.471 0.172 0.742 0.365 �0.115 �0.800 �0.306 1.000

Metal data for the analysis are from the average values of the two sampling events. (n = 9) Bold face values indicate significant correlation (95%significance level).

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as the concentrations of the same metals from both sam-plings in general do not vary significantly (Table 2), wethink metal enrichment factors calculated from the Decem-ber 2004 sampling can fairly well represent the environ-mental status of the study area. The results from thisstudy show that, in our study area, Cu enrichment factor,EF (Cu), ranges from 0.7 to 2.6, EF (Pb) from 2.2 to 3.9,and EF (Zn) from 0.9 to 2.0, EF (Cd) from 0.6 to 5.5,EF (Cr) from 0.4 to 2.2, and EF (Ni) from 0.6 to 1.4 (Table5). As shown in Table 5, the enrichment factor of Pb isgreater than 1.5 everywhere, indicating a significant Pbcontamination in the study area. In contrast, enrichmentfactor of Ni is less than 1.5 everywhere, suggesting thatNi contamination is not a problem at present. Most ofEF values of Cu, Cd, Zn and Cr are generally less than1.5 (EF < 1.5), suggesting that these metal contaminationsin most of the study area are not significant. However, withrespect to a specific site in the study area, YuandangLagoon is severely contaminated by Cu, Pb and Cd asreflected by the enrichment factor values of these metalsthat are all greater than 1.5 (Table 5). The source of thesecontaminants can be attributed to the sewage input in thearea because the lagoon was used to accept the municipalsewage (Hong et al., 1995). Metal enrichment factors alsosuggest that Maluan Bay be significantly contaminatedby Pb and Cd (Table 5). The source input of metal contam-inants to Maluan Bay could be tracked back to the timeperiod before 1999 when it received direct sewage dischargefrom Xinling Industrial Area. After 1999, most of sewagewas intercepted into sewage treatment plant. However, asshown in this study, metal contamination in surface sedi-ments still exists in this area, suggesting recent contamina-tion of these metals. In western Xiamen Bay, metalenrichment factors suggest that Station X5 is contami-nated by Cu, Pb and Cr (Table 5). Because Station X5 isin the inner harbor, water circulation in this area is notas good as that in other stations in the main channel andthe station is located near an outlet of sewage discharge,which was uncontrolled in the past and is presently treatedby Sewage Treatment Plant of Xinlin Industrial Area. Allthese could be factors causing high metal concentrationsin the area.

Another criterion to evaluate the heavy metal pollutionin the western Xiamen Bay sediments is the geoaccumula-tion index (Igeo) introduced by Muller (1979). It was origi-nally defined by Muller (1979) in order to determine anddefine metals contamination in sediments, by comparingcurrent concentrations with pre-industrial levels and canbe calculated by the following equation:

Igeo ¼ Log2

Cn

1:5Bn

� �ð2Þ

where Cn is the measured concentration of the examinedmetal (n) in the sediment and Bn is the geochemical back-ground concentration of the metal (n). Factor 1.5 is thebackground matrix correction factor due to lithogenic ef-fects. Because we did not have the background values ofthe metals of interest, same as we did in enrichment factorcalculation, we adopt the earth crust values (Martin andWhitfield, 1983) in geoaccumulation index calculation.

The geoaccumulation index can assess to the estimationof these pollution process. Muller has distinguished sevenclasses of geoaccumulation index (Muller, 1981) (Table6). The highest class (class six) reflects 100-fold enrichmentabove the background values. The results of Igeo values aretabulated in Table 7. According to the Muller scale (Mul-ler, 1981), the index of geoaccumulation indicates that Pbcan be considered as a moderate pollutant in all the studyareas (Igeo > 1). In addition, Station X5 in the western Xia-men Bay shows less degree of pollution by Cu and Cr(Igeo,Cu = 0.7, Igeo,Cr = 0.3). Maluan Bay shows values fall-ing into the unpolluted to moderately polluted classes ofCd (Igeo = <0 �1.7) possibly due to the input of industriesaround. Yuandang Lagoon (Station Y2) shows a moderatepollution with Cu (Igeo,Cu = 0.4–1.0), Cd (Igeo,Cd = 0.8–1.1)and, to less extent, Zn (Igeo,Zn = 0.1–0.2). Moderate pollu-tion of Cd (Igeo,Cd = 1.4) at Station X4 was found in theDecember 2004 sampling, but it was not repeated in theJuly 2005 sampling. Based on the Muller scale (Muller,1981), Ni and Cr (except for one case at Station X5) as wellas Zn (excluding Yuandang Lagoon) in the bottom sedi-ments exhibit Igeo values corresponding to an unpollutedsituation (Igeo < 0). Because Maluan Bay receives wastewa-ter discharge from Xinlin Industrial Area, Station Y2 inYangdang Lagoon receives waster water discharge fromold Xiamen Industrial Area and Station X4 in DongduPort receives waste water discharge from Huli SpecialIndustrial Area, respectively, metal contaminations in these

Table 5Metal enrichment factors in the sediments from western Xiamen Bay andadjacent areas

Station EF_Cu EF_Pb EF_Zn EF_Cd EF_Ni EF_Cr

X1 0.82 2.98 0.87 0.76 0.52 0.81X2 0.80 2.91 0.83 0.70 0.54 0.90X3 1.25 2.67 0.82 0.69 0.53 0.80X4 1.11 2.92 0.88 2.11 0.58 0.88X5 2.74 3.54 1.35 0.89 1.48 2.21

X6 0.80 3.15 0.80 0.56 0.57 0.96M1 1.09 3.62 1.08 2.17 0.83 0.56M2 1.03 3.82 1.23 4.14 1.04 1.19Y2 1.86 2.65 1.24 2.16 0.43 0.67

The samples were collected in December 2004. A bold face value suggestsanthropogenic input to the area.

Table 6Muller’s classification for geoaccumulation index (Muller, 1981)

Igeo value Class Quality of sediment

60 0 Unpolluted0–1 1 From unpolluted to moderately polluted1–2 2 Moderately polluted2–3 3 From moderately to strongly polluted3–4 4 Strongly polluted4–5 5 From strongly to extremely polluted>5 6 Extremely polluted

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areas or stations may be caused by local point sources. Theresults show that the metal contamination found in westernXiamen Bay, Maluan Bay and especially in YuandangLagoon by the simple examination of metal concentrationcan be more correctly evaluated if a complementary infor-mation based on metal baseline values is considered usingthe geoaccumulation index (Table 7) that provides a moresuitable appraisal of the pollution process caused byanthropogenic inputs.

4. Conclusion

This study shows that with the creation of Xiamen Eco-nomic Special Zone and establishment of industrial enter-prises, the environmental impact has been seen asdemonstrated by metal contamination in western XiamenBay and adjacent Maluan Bay and Yuandang Lagoon,which is becoming an environmental problem. In thisstudy, we found that although metal (Cu, Pb, Zn, Ni, Cdand Cr) concentrations in the surface sediments meet theChinese National Standard of Marine Sediment Qualitycriteria, metal enrichment factors (EF) and geoaccumula-tion index (Igeo) confirm the certain extent of metal con-tamination or pollution in the western Xiamen Bay,Maluan Bay and Yuandang Lagoon, particularly withregard to Pb that causes moderate pollution in the wholestudy area. Depending on the source input, we found thatmoderate pollution of specific metals exist in localized sites.The results suggest that point source input of some specificmetal contaminant(s) has caused significant sediment con-tamination in the local area. Although the application ofnational sediment quality standard criteria could be a gen-eral measurement of sediment quality, the results from thisstudy suggest that it be not reasonable and fair to use thiskind of criteria only to evaluate the environmental statusand sediment contamination. A multiple approachesshould be considered for sediment quality assessment. Withthe further industrialization and economic development inthe region, greater attention should be paid to land-basedpoint sources around the area. Greater caution should alsobe taken when these sediments are dredged and dumpeddue to their impact on the environment.

Acknowledgements

We would like to thank Xiaoxia Li and Chunlin Yang,graduate students at Xiamen University, for their assis-tance in the field work. Informative comments and sugges-tions from an anonymous reviewer greatly improved thismanuscript. The work was supported in part by theDepartment of Science and Technology of Fujian Prov-ince, China, under Project No. 2004I001 and the MontclairState University Sokol Faculty Fellow Award (HF) as wellas Montclair State University FSP Program (HF).

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