Heavy metal contamination of overlying waters and bed sedimentsof Haihe Basin in China

Wenzhong Tang a, Yu Zhao a, Chao Wang a, Baoqing Shan a,n, Jingguo Cui b

a State Key Laboratory on Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences,Beijing 10085, Chinab Beijing Sound Environmental Engineering Co., Ltd., Beijing 101102, China

a r t i c l e i n f o

Article history:Received 24 July 2013Received in revised form27 September 2013Accepted 30 September 2013Available online 18 October 2013

Keywords:Heavy metalsHaihe BasinContaminationOverlying watersSurface sediments

a b s t r a c t

The Haihe Basin is in an area of high population density and rapid economic development, and is one ofthe most polluted river basins in China. Examination of heavy metals (Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn) inoverlying waters and surface sediments in rivers was conducted in the basin's seven watersheds. Cdconcentrations of overlying river waters exceeded Chinese environmental quality standard values forsurface water (40.010 mg/L) at 90% of stations. In surface river sediments, average concentrations of Cd,Co, Cr, Cu, Mn, Ni, Pb and Zn in the basin were 0.364, 13.4, 81.9, 53.3, 435, 27.8, 20.0 and 256 mg/kg,respectively. Cd, Zn and Cu were the most anthropogenically enriched elements, as indicated byenrichment factor (EF) values41.5; EF values were highest for these metals in the Zi Ya He (ZYH) andZhang Wei He (ZWH) watersheds. Cd in surface river sediments showed a high potential ecological risk(PER) in the ZYH and ZWH watersheds. The comprehensive PER due to all studied metals was high atmany stations, especially in the ZYH and ZWH watersheds. The results indicate that heavy metalcontamination in the rivers of the Haihe Basin should be considered when developing basin manage-ment strategies for protecting the aquatic environment.

& 2013 Elsevier Inc. All rights reserved.

1. Introduction

Heavy metal contamination of aquatic bodies is one of the environ-mental problems that accompany rapid economic development inboth developed and developing countries (Gao and Chen, 2012).Heavy metals are widespread and persistent in the environment,potentially toxic, and can become incorporated into food webs(Suresh et al., 2012; Taweel et al., 2013; Xiao et al., 2012). Heavymetals with low solubility in water, are easily adsorbed andaccumulated in sediments (Alvarez et al., 2011; Jain et al., 2008;Ma et al., 2013). Sediments in river beds or lake bottoms thereforeoften represent a major repository for contaminants dischargedinto water bodies (Ma et al. 2013; Vandecasteele et al., 2004).Heavy metals adsorbed in sediments can be desorbed back intooverlying water under certain conditions, causing secondary pollutionand potentially having toxic effects on organisms (Niu et al., 2009;Segura et al., 2006). Moreover, the equilibrium partitioning of metalsat the sediment–water interface is an important factor influencingtheir biogeochemical processes and bioavailability (Huo et al., 2013).Heavy metal contamination of sediments can critically degrade

aquatic systems (Suresh et al., 2012), so the accumulation of heavymetal in sediments is a cause of growing interest and concern;environmental problems due to heavy metal pollution of aquaticsystems have recently been extensively studied (Buggy and Tobin2008; Griscom et al., 2000; Karak et al., 2013; Shi et al., 2013;Wang et al., 2012).

Heavy metal pollution in rivers in other areas of the world hasbeen a research focus for a long time; the Reedy River in theUnited States (Otter et al., 2012), the Hindon River in India(Chabukdhara and Nema, 2012) and the Xanaes River in Argentina(Harguinteguy et al., 2013) are examples of rivers in which heavymetal pollution has been examined. In China, heavy metal con-tamination of river sediments did not attract much attention fromresearchers and governments prior to 2000, with relatively fewstudies conducted (He et al., 1998; Ma et al., 2013; Zhao et al., 1999).In recent years, industrial and mining activities that dischargeheavy metals through atmospheric emissions or effluent intorivers have been developing continuously and rapidly, particularlyin the Haihe Basin. One-sixth of all arable lands in China have beencontaminated by heavy metals. To control the problem of heavymetal contamination, in early 2011 the State Council of Chinaapproved the “12th National 5-yr Plan for Comprehensive Preven-tion and Control of Heavy Metal Pollution”. Heavy metal pollutionhas become an important topic for the Chinese government andthe public (Ma et al., 2013). The Haihe Basin, with an area of318,000 km2, is one of the most developed regions and has the

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Abbreviations: BSH, Bei San He; YDH, Yong Ding He; DQH, Da Qing He; ZYH, Zi YaHe; HLG, Hei Long Gang; ZWH, Zhang Wei He; TMH, Tu-hai Ma-xia He; EF,enrichment factor; PER, potential ecological risk; RAC, risk assessment code

n Corresponding author.E-mail addresses: wztang@rcees.ac.cn (W. Tang), bqshan@rcees.ac.cn (B. Shan).

Ecotoxicology and Environmental Safety 98 (2013) 317–323

highest population density in China. Heavy industrial develop-ment and rapid urbanization have caused significant pollution ofrivers in this area, including heavy metal pollution. It is importantto understand the heavy metal contamination status in the riversof a large basin, such as the Haihe Basin, to provide a reference forthe large-scale control and management of heavy metals.

To assess heavy metal contamination and provide backgroundinformation for the Haihe Basin, Cd, Co, Cr, Cu, Mn, Ni, Pb, and Znin overlying river waters and surface river sediments was con-ducted in the seven watersheds of the basin. The purposes of thisstudy were (1) to investigate heavy metal concentrations in over-lying river waters and surface river sediments; and (2) to analyzetheir contamination status through the enrichment factor (EF),potential ecological risk (PER) and risk assessment code (RAC).

2. Materials and methods

2.1. Study area

The Haihe Basin, located mainly within the province of Hebei, includes Beijing,Tianjin, parts of Inner Mongolia, and the provinces of Shanxi, Henan, and Shandong(Fig. 1). The area of the Haihe Basin is 318,000 km2, and its climate is temperatecontinental monsoon. The mean annual precipitation is 527 mm. It is one of severalmajor basins under the management of the Ministry of Water Resources. Heavyindustrial development and rapid urbanization have caused significant pollution towaters in this region. Water resources are in high demand and the deterioration of waterquality has hastened the shortage of water resources. Therefore, the Haihe Basin hasattracted much attention from the Chinese government and has become one of the mostimportant basins in the National 11th and 12th 5-year Plan for Water Pollution Control.

The Haihe Basin is divided into nine major watersheds: Luan He, Bei San He(BSH), Yong Ding He (YDH), Da Qing He (DQH), Hai-he Gan-liu, Zi Ya He (ZYH), HeiLong Gang (HLG), Zhang Wei He (ZWH), and Tu-hai Ma-xia He (TMH).

2.2. Sample collection and analysis

Surface sediments were collected from July to November 2009 at 117 stations inthe BSH, YDH, DQH, ZYH, HLG, ZWH and TMH watersheds (Fig. 1) using hand-heldPVC corers with a diameter of 80 mm and a length of 150 cm. Three sediment

columns were taken at random from each station, and the upper 0–10 cm ofsediment was manually collected with a plastic spoon. In the laboratory, thesamples (n¼351) were air-dried then transferred to an oven to dry at 40 1C, thenground and passed through a 100-mesh sieve prior to analysis. The overlying watersamples (n¼351) were collected at each station simultaneously. The water sampleswere filtered using Millipore membrane filters with 0.45 mm pores, then stored inpolystyrene bottles and preserved with concentrated nitric acid (AR grade) atpHo2 prior to heavy metal analysis.

For total heavy metal analysis, sediment samples (0.100 g) were digested with a5:l mixture of hydrofluoric: perchloric acid (Tessier et al., 1979) in a microwave inTeflon vessels (Marsx Press, CEM); the digestion conditions are presented in TableS1. The geochemical fractionation of heavy metals was determined using the BCRthree-step sequential extraction procedure (Nemati et al., 2011). This methodprovides the exchangeable (sediment solution, carbonates, exchangeable metals),reducible (oxides Fe/Mn), oxidizable (organic matter and sulfides), and residual(remaining, non-silicate bound metals) fractions of heavy metals in sediments. Allof the above solutions and the overlying water samples were stored at 4 1C prior toanalysis. The concentrations of Cd, Co, Cr, Cu, Mn, Ni, Pb, Zn, and Al were measuredby inductively coupled plasma-mass spectrometry (ICP-MS) (7500a, Agilent, USA)(detection limit 0.015–0.120 mg/L) and inductively coupled plasma optical emissionspectrometer (ICP-OES) (Optima 2000DV, Perkin Elmer, USA) (detection limit0.001–0.030 mg/L). Laboratory quality control consisted of the analysis of sedimentreference material (GBW07302a, China) and triplicate samples. Recoveries variedbut all fell within the range of 90–95%, and the precision was under 5% relativestandard deviation (RSD). The results of all indices were the average of the threeparallel samples of sediments and overlying water, respectively.

2.3. Enrichment factor

To obtain information about the sources and temporal variation of metal con-taminants, the EFs of heavy metals in river sediments were calculated using theequation from Zhang and Shan, (2008)

EF¼ ½CnðsampleÞ=CAlðsampleÞ�=½BnðbaselineÞ=BAlðbaselineÞ� ð1Þ

where Cn is metal content in the sediments, Bn is the background concentration ofthe metal, CAl is the Al concentration in the sediments, and BAl is the backgroundconcentration of Al. In this study, the soil background values of the Haihe Basinwere adopted as the baseline values (China National Environmental MonitoringCenter (CNEMC), 1990).

2.4. Potential ecological risk

The PER index was used to assess the degree of contamination of heavy metalsin the sediments. The equations for calculating the PER index were proposed byGuo et al. (2010) and are as follows:

Eir ¼ Tir � Ci

f ¼ Tir � ðCi

s n CinÞ ð2Þ

RI¼ ∑n

i ¼ 1Eir ð3Þ

where Cis is the content of the element in samples, Cin is the reference value of theelement, Cif is the single element pollution factor, Eir is the PER index of an individualelement, and Tir is the biological toxicity factor of an individual element, which aredefined as Cd¼30, Cr¼2, Co¼Cu¼Ni¼Pb¼5, Mn¼Zn¼1 (Guo et al., 2010;Hakanson, 1980). RI is the comprehensive PER index, which is the sum of Eir.Table S2 shows the factor standard of different levels.

2.5. Risk assessment code

The RAC was used to assess the heavy metal content of the sediments from aregulatory perspective in this study. The RAC assesses the potential release of heavymetals in solution by calculating the percentage of metals occurring in exchange-able fraction in the studied sediments (Singh et al., 2005).

3. Results and discussion

3.1. Heavy metal concentrations in overlying river waters

The heavy metal concentrations in overlying river waters of theHaihe Basin are given in Table S3. Average concentrations of Cd, Cr, Cu,Mn, Ni, Pb and Zn in the entire basin were 0.028, 0.062, 0.079, 0.162,0.056, 0.069 and 0.058 mg/L, respectively. Concentrations of all metals,except Cd, were lower than the standard values of the environmentalquality standards for Chinese surface water (China 2002). In contrast,Fig. 1. Map showing the sediment sampling stations in the rivers of the Haihe Basin.

W. Tang et al. / Ecotoxicology and Environmental Safety 98 (2013) 317–323318

high Cd concentrations (40.010 mg/L) were observed at most sites,exceeded the environmental quality standard at 90% of stations andwere highest in the BSH, ZYH and ZWH watersheds. These resultsindicate that Cd pollution has become a major environmental problemin the rivers of the Haihe Basin.

3.2. Heavy metal content of surface river sediments

Fig. 2 shows heavy metal concentrations of surface riversediments in the Haihe Basin. Average concentrations of Cd, Co,Cr, Cu, Mn, Ni, Pb and Zn across the basin were 0.364, 13.4, 81.9,53.3, 435, 27.8, 20.0 and 256 mg/kg, respectively. Average Cdconcentrations were highest in the surface river sediments ofZYH (0.704 mg/kg) and ZWH (0.587 mg/kg). Average Cr, Cu and Pbconcentrations were highest in the surface river sediments of the

ZYH watershed (201, 114 and 43.0 mg/kg, respectively). Average Znconcentrations were highest in surface river sediments of the YDH,ZYH and ZWH watersheds (327, 580 and 269 mg/kg, respectively).There was no apparent spatial variability in average Co, Mn, and Niconcentrations in the surface river sediments of the seven water-sheds. In addition, Al concentrations of the studied sedimentsranged from 47.9 g/kg to 81.2 g/kg. High levels of metals in thesurface river sediments of the ZYH and ZWH watersheds impliedthat a substantial increase in anthropogenic metal loading hasoccurred in these two regions, as suggested by Sondi et al. (2008).

The inter-element relationships can provide informationregarding heavy metal sources (Dragovic et al., 2008); therefore,the Spearman correlation coefficients of the heavy metals wereanalyzed (Table S4). The results revealed that the heavy metals(Cd, Cr, Pb and Zn) (Co, Mn and Ni) were positively correlated

Fig. 2. Concentrations of heavy metals in surface river sediments of the Haihe Basin (mg/kg).

W. Tang et al. / Ecotoxicology and Environmental Safety 98 (2013) 317–323 319

among themselves (pr0.01), and that there was also a positivecorrelation (pr0.01) between Cu and the other metals, except Cd,Co and Mn. In addition, a significant positive correlation (pr0.05)was observed between Cd and Cu, Co and Cr, Cr and Ni, Ni and Pb,and Ni and Zn. These results indicate that the metals in theanalyzed sediments had different origins or controlling factors.

3.3. Heavy metal contamination in surface river sediments

3.3.1. Enrichment factorEnrichment factor is a normalization technique widely used to

separate metals derived from natural sources in the environ-ment from those associated with anthropogenic activities (Gao and

Chen, 2012). To further evaluate anthropogenic influences onheavy metals in the surface river sediments of the Haihe Basin,the EF for each metal was calculated and is shown in Fig. 3. Themean EF was highest for Cd (4.47) indicating the highest degree ofanthropogenic contamination of this metal, followed by Zn (3.71),Cu (2.50), Cr (1.34), Co (1.10), Ni (1.05), Pb (1.02), and Mn (0.76).The spatial distribution pattern of EF values of the metals exam-ined was similar to that of their contents.

An EF value of approximately 1 suggests that a given metal mayoriginate entirely from natural sources, such as crustal materials ornatural weathering processes (Zhang and Liu, 2002). A slightpositive deviation of an EF value from unity may not necessarilyarise from anthropogenic activities; it may also be caused by

Fig. 3. EF values for heavy metals in surface river sediments of the Haihe Basin.

W. Tang et al. / Ecotoxicology and Environmental Safety 98 (2013) 317–323320

natural variation in the elemental composition between studiedsediments and reference soils used in the EF calculation (Gao andChen, 2012). Therefore, an EF value between 0.5 and 1.5 suggeststhat the metal may be entirely from crustal materials or naturalweathering processes. However, an EF greater than 1.5 suggeststhat a significant portion of the metal originated from anthropo-genic processes (Feng et al., 2004). In the Haihe Basin, Cd, Zn andCu were positively correlated among themselves (Table S4) andwere the most anthropogenically enriched elements in the surfaceriver sediments; potential anthropogenic sources include mining,leather industry activities, and agricultural fertilization. The meanEF values of Cr, Co, Ni, Pb and Mn were all less than 1.5, indicatingthat these metals were derived from the natural sources, such asunderlying geological material. With the exception of sedimentsfrom the TMH watershed, the mean EF values for Cd were allgreater than 1.5 in the surface river sediments, and were particu-larly high in the ZYH (8.34) and ZWH (8.07) watersheds. The meanEF values of Zn and Cu were also greater in ZYH and ZWH (Fig. 3).These results indicate contamination of the Haihe Basin with Cd,Zn and Cu, which is consistent with other studies (Chabukdharaand Nema, 2012; Quinton and Catt, 2007; Tang et al., 2010); the EF

values obtained may be useful indicators of the role of anthro-pogenic processes in their distribution.

3.3.2. Potential ecological riskPotential ecological risk represents the sensitivity of the biolo-

gical community to a given substance and illustrates the risk posedby contamination (Suresh et al., 2012; Yi et al., 2011). CalculatedPER indexes of an individual element (Eir) are presented in TableS5, and the comprehensive PERs (RI) are shown in Fig. 4. In theHaihe Basin, all elements showed low PER, with the exception ofCd. The Eir values of Cd ranged from 33.8 to 240, with an average of119 in the surface river sediments of seven watersheds, indicatinghigh Cd contamination of the sediments in the rivers of the HaiheBasin (Nemati et al., 2011), which is consistent with the resultsobtained from the overlying water samples. The PER of Cd was lowin the TMH watershed, moderate in the DQH watershed, consider-able in the BSH, YDH and HLG watersheds, and high in the ZYHand ZWH watersheds, respectively. In the ZYH and ZWH watersheds,30.0% and 19.0% of samples had very high PER. The mean RI values ofthe surface river sediments were 117, 141, 91.2, 302, 125, 231, and57.1 in BSH, YDH, DQH, ZYH, HLG, ZWH and TMH watersheds,

km

Da Qing He

Hai-he Gan-liu

Luan HeBei San HeYong Ding He

Zhang Wei He

Zi Ya He

River

<150

Watershed boundary Basin boundary

150-300 300-600 ≥ 600

Fig. 4. PER indexes of heavy metals in surface river sediments in the Haihe Basin.

W. Tang et al. / Ecotoxicology and Environmental Safety 98 (2013) 317–323 321

respectively, with an overall average of 152. As shown in Table S2,there were many stations in the rivers of the Haihe Basin with highPER, which were mainly located in the ZYH and ZWH watersheds(Fig. 4). This may be due to mining and industrial development inthe two watersheds, and the distribution plots of RI could beuseful in identifying the stations that need the most attention.

To further examine heavy metal contamination in surface riversediments of the Haihe Basin, the speciation of Cd, Cr, Cu, Ni, Pband Zn in samples from ZYH watershed (RI4300) was investi-gated. The results of the sequential extraction are shown in Fig. 5.Cr, Cu, Ni and Pb occur predominantly in the residual fraction,representing an average of 58%, 48%, 74% and 61% of the totalmetal contents, respectively. In contrast, more than 30% of thetotal Cd and Zn contents were observed in the exchangeablefraction. The high proportion of metals in the exchangeablefraction is indicative of anthropogenic pollution and is in accor-dance with the results of similar studies carried out on sitesaffected by heavy metal pollution in different rivers, including theLouro River (Spain) (Filgueiras et al., 2004), the Danube River (Relićet al., 2005) and the River Po (Italy) (Farkas et al., 2007). Theclassification of RAC is as follows: proportion of a metal occurringin the exchangeable fraction o1%, no risk; 1–10%, low risk; 11–30%, medium risk; 31–50%, high risk; andZ75%, very high risk(Singh et al., 2005). According to the classification, the riskassociated with Cd and Zn in the sediments of ZYH watershed(RI4300) was high, which corroborate the results of the EF andPER index. Sediment contaminants may move into the food chain,particularly if the contaminants occur in bioavailable forms. Cdand Zn can accumulate in relatively large amounts in plants withoutany apparent effects, which could cause human health problems(Lambert et al., 2007; Zhao et al., 2007). Therefore, it is importantthat heavy metal contaminants, especially Cd, in the river sediments ofthe Haihe Basin continue to be carefully monitored.

4. Conclusion

An examination of heavy metal contamination in overlyingwaters and surface sediments was conducted in the rivers of sevenwatersheds in the Haihe Basin. High Cd concentrations in over-lying waters, especially in the rivers of the BSH, ZYH and ZWHwatersheds were observed, while Cd concentrations in surfacesediments were highest in rivers of the ZYH and ZWH watersheds.As indicated by EF values, Cd, Zn, and Cu were the most anthro-pogenically enriched elements in the surface river sediments of

the Haihe Basin, while Cr, Co, Ni, Pb andMnwere derived from naturalsources in most rivers. Cd had low PER in the TMH watershed,moderate PER in the DQH watershed, considerable PER in the BSH,YDH and HLG watersheds, and high PER in the ZYH and ZWHwatersheds. Many stations in the rivers of the Haihe Basin were foundto have high PER; these sites were mainly distributed in the ZYH andZWH watersheds, which may be due to mining and rapid industrialdevelopment. This information could be useful in the development ofeffective management strategies to control heavy metal pollution inthe rivers of the Haihe Basin.

Acknowledgments

This research was supported by the National Natural ScienceFoundation of China (No. 21107126), and the National WaterPollution Control Program (No. 2012ZX07203-006).

Appendix A. Supplementary materials

Supplementary data associated with this article can be found in theonline version at http://dx.doi.org/10.1016/j.ecoenv.2013.09.038.

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