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RESEARCH ARTICLE Preliminary assessment of heavy metal contamination in surface water and sediments from Honghu Lake, East Central China Ying HU 1,2 , Shihua QI () 1,2 , Chenxi WU 2 , Yanping KE 1,2 , Jing CHEN 1,2 , Wei CHEN 1,2 , Xiangyi GONG 3 1 State Key Laboratory of Biogeology and Environmental Geology, Wuhan 430074, China 2 School of Environmental Studies, China University of Geosciences, Wuhan 430074, China 3 College of Resources and Environmental Engineering, Wuhan University of Science and Technology, Wuhan 430081, China © Higher Education Press and Springer-Verlag Berlin Heidelberg 2012 Abstract Heavy metal concentrations in surface water and sediments collected from Honghu Lake in Hubei Province, China were analyzed, and ecological risks were evaluated according to the sediment quality guidelines. The results showed that the average concentrations of heavy metals in surface water were ranked as: As > Zn > Cu > Cr > Pb > Ni > Cd > Hg. In comparison with results reported in other rivers and the background values, The Honghu Lake was polluted by As, Cr, Pb, Cu and Ni. Most of metals might be mainly from fertilizers, industrial efuent and domestic wastewater around the lake. Heavy metals concentrations were relatively higher in the inlet area than in other areas. Negative correlations were observed between most heavy metals and pH, while a signicant positive correlation was present between Zn, Cd and Pb. In the sediment core, Cu, Zn, Cr and Ni showed a decreasing trend while Cd present an increasing trend. The decrease of As, Cu, Zn, Cr and Ni in the 1990s might due to the ood event in 1998. The analysis of ecological risk assessment based on sediment quality guidelines suggested that heavy metals in most sediments from the Honghu Lake had moderate toxicity, with Cr being the highest priority pollutant. Keywords metal distribution, sediment core, ecological risk assessment, wetland 1 Introduction Lakes are considered one of the most versatile ecosystems in the world, but they are more sensitive to environmental pollution and anthropogenic impacts (Forghani et al., 2009). Heavy metals, such as arsenic (As), mercury (Hg), cadmium (Cd), lead (Pb), and chromium (Cr), are commonly detected in lakes (Anshumali et al., 2009; Ongeri et al., 2009). Like other aquatic systems, heavy metals enter lakes through natural sources (e.g. weathering, erosion) and anthropogenic sources (e.g. mining, urban and industrial wastewater) (Zorer et al., 2008; Alhas et al., 2009). At present, heavy metal pollution has become a great environmental concern with their toxicity, persis- tence, bioaccumulation and biomagnication in the food chain (Li et al., 2008; Yuan et al., 2011). For human beings, lakes are important sources of water and food. Thus, heavy metals in lakes might ultimately have adverse biologic effects on human health through drinking water and consuming aquatic products (Huang et al., 2009; Zhang et al., 2009). For these reasons, it would be desirable and imperative to investigate their distribution in lakes, which can provide valuable information of heavy metal pollution and help evaluate potential environmental risks. Honghu Lake (113°12113°26E and 29°4029°58N), the seventh largest natural freshwater lake in China, is a unique inland freshwater lake in the middle-lower reaches of the Yangtze River. The lake covers an area of 344km 2 , with an average water depth of 1.34 m. It is mainly used for aquatic cultivation, water supply, and irrigation. Due to the extensive water conservancy constructions, the Honghu Lake changed an overowing lake to a semi-closed one during the 1950s1970s. With rapid development of the local economy since 1980s, large amounts of wastewater from industrial, domestic and agricultural sources from Honghu City and Jianli County in Hubei Province, China was discharged into the lake. As a result, water environ- ment in the Honghu Lake has deteriorated in terms of Received October 14, 2011; accepted November 13, 2011 E-mail: [email protected] Front. Earth Sci. 2012, 6(1): 3947 DOI 10.1007/s11707-012-0309-z

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RESEARCH ARTICLE

Preliminary assessment of heavy metal contamination insurface water and sediments from Honghu Lake,

East Central China

Ying HU1,2, Shihua QI (✉)1,2, Chenxi WU2, Yanping KE1,2, Jing CHEN1,2, Wei CHEN1,2, Xiangyi GONG3

1 State Key Laboratory of Biogeology and Environmental Geology, Wuhan 430074, China2 School of Environmental Studies, China University of Geosciences, Wuhan 430074, China

3 College of Resources and Environmental Engineering, Wuhan University of Science and Technology, Wuhan 430081, China

© Higher Education Press and Springer-Verlag Berlin Heidelberg 2012

Abstract Heavy metal concentrations in surface waterand sediments collected from Honghu Lake in HubeiProvince, China were analyzed, and ecological risks wereevaluated according to the sediment quality guidelines.The results showed that the average concentrations ofheavy metals in surface water were ranked as: As>Zn>Cu>Cr> Pb>Ni>Cd>Hg. In comparison with resultsreported in other rivers and the background values, TheHonghu Lake was polluted by As, Cr, Pb, Cu and Ni. Mostof metals might be mainly from fertilizers, industrialeffluent and domestic wastewater around the lake. Heavymetals concentrations were relatively higher in the inletarea than in other areas. Negative correlations wereobserved between most heavy metals and pH, while asignificant positive correlation was present between Zn, Cdand Pb. In the sediment core, Cu, Zn, Cr and Ni showed adecreasing trend while Cd present an increasing trend. Thedecrease of As, Cu, Zn, Cr and Ni in the 1990s might dueto the flood event in 1998. The analysis of ecological riskassessment based on sediment quality guidelines suggestedthat heavy metals in most sediments from the HonghuLake had moderate toxicity, with Cr being the highestpriority pollutant.

Keywords metal distribution, sediment core, ecologicalrisk assessment, wetland

1 Introduction

Lakes are considered one of the most versatile ecosystems

in the world, but they are more sensitive to environmentalpollution and anthropogenic impacts (Forghani et al.,2009). Heavy metals, such as arsenic (As), mercury (Hg),cadmium (Cd), lead (Pb), and chromium (Cr), arecommonly detected in lakes (Anshumali et al., 2009;Ongeri et al., 2009). Like other aquatic systems, heavymetals enter lakes through natural sources (e.g. weathering,erosion) and anthropogenic sources (e.g. mining, urbanand industrial wastewater) (Zorer et al., 2008; Alhas et al.,2009). At present, heavy metal pollution has become agreat environmental concern with their toxicity, persis-tence, bioaccumulation and biomagnification in the foodchain (Li et al., 2008; Yuan et al., 2011). For human beings,lakes are important sources of water and food. Thus, heavymetals in lakes might ultimately have adverse biologiceffects on human health through drinking water andconsuming aquatic products (Huang et al., 2009; Zhang etal., 2009). For these reasons, it would be desirable andimperative to investigate their distribution in lakes, whichcan provide valuable information of heavy metal pollutionand help evaluate potential environmental risks.Honghu Lake (113°12′–113°26′E and 29°40′–29°58′N),

the seventh largest natural freshwater lake in China, is aunique inland freshwater lake in the middle-lower reachesof the Yangtze River. The lake covers an area of 344 km2,with an average water depth of 1.34 m. It is mainly used foraquatic cultivation, water supply, and irrigation. Due to theextensive water conservancy constructions, the HonghuLake changed an overflowing lake to a semi-closed oneduring the 1950s–1970s. With rapid development of thelocal economy since 1980s, large amounts of wastewaterfrom industrial, domestic and agricultural sources fromHonghu City and Jianli County in Hubei Province, Chinawas discharged into the lake. As a result, water environ-ment in the Honghu Lake has deteriorated in terms of

Received October 14, 2011; accepted November 13, 2011

E-mail: [email protected]

Front. Earth Sci. 2012, 6(1): 39–47DOI 10.1007/s11707-012-0309-z

entrophication (Cheng and Li, 2006; Gui and Yu, 2008)and heavy metal pollution (Yao et al., 2009). A number ofrecent studies have discussed the distribution and sourcesof heavy metals in various freshwater systems (Chen et al.,2010; Kurun et al., 2010; Botsou et al., 2011). Somestudies concerned metal distribution in the Honghu Lakehave also been reported (Yao et al. 2006; Liu and Li, 2011),but little is known about the ecological risk associated withheavy metal concentrations in the sediments.The aims of this study were to: 1) investigate the

contamination levels and distributions of heavy metals insurface water and sediment core from the Honghu Lake; 2)compare their concentrations with other rivers in the worldand environmental quality standards, and 3) evaluate thepotential toxicity of the metal concentrations based onsediment quality guidelines.

2 Materials and methods

2.1 Sample collection

In July 2005, water samples at 0.5 m below the watersurface were collected at sampling locations shown in

Fig. 1. All of these water samples were obtained usingcleaned polyethylene bottles, which were washed withhydrochloric acid and then rinsed with distilled water.Subsequently, water samples were filtered through0.45 µm millipore filters, acidified to pH< 2 with 2 mL6 N HCl and transported to the laboratory for analysis.During the sample collection, a global positioning system(GPS) was used to locate the sites. In addition, watertemperatures and pH were measured, and electricalconductivity was analyzed by a Model 3010 portableconductivity meter.A sedimentary core (S1) for metal analysis was

recovered at the central part of the Honghu Lake(113°22′18′′E, 29°51′35′′N), using a static gravity corer(5 cm i.d.). Another core was taken from the same site fordating. Each core with a length of 75 cm was sectioned at1 cm interval. Total 150 sediment samples were obtainedfrom the sampling site (S1). All the samples were thenplaced into sealed polyethylene bags and transported to thelaboratory for storage at – 20°C until analysis. In thelaboratory, samples were air-dried at room temperature andsieved through a 100-mesh sieve. For heavy metalanalysis, 0.1 g of dry sample was digested using 10 mLHCl-HNO3-HF. Details about the procedure for the

Fig. 1 Location map of Honghu Lake and sampling sites of surface water and sediment core

40 Front. Earth Sci. 2012, 6(1): 39–47

digestion were described elsewhere (Yao et al., 2009; Baiet al., 2011). The solution was finally diluted to 25 mL withdeionized distilled water.

2.2 Sample analysis

Concentrations of Pb, Cd, Ni, Cr, Cu, Zn in all sampleswere determined using an inductively coupled plasmamass spectrometry (ICP-MS), while As and Hg wereanalyzed by atomic fluorescence spectroscopy (AFS). Forquality control, procedural blanks and duplicates were runevery 10 samples. The standard deviations were below10% for all elements. The detection limit for individualmetal was 0.5 to 5 ng/L for a water sample and 0.005 to1 µg/g for a sediment sample.

2.3 Dating

The sediment core was dated by the 210Pb method. 210Pbwas measured by the analysis of the α-radioactivity of itsdecay product 210Po with the assumption that the two are inequilibrium (Zhang et al., 2011). Polonium isotopes wereextracted, purified and plated onto a silver disk from thesample solution (in 1 N HCl) at 80°C. The counting resultswere corrected for the decay of 210Pb and 210Po (Hosono etal., 2010). Sedimentation rates were determined by aconstant activity (CA) model (Lin et al, 1998).

3 Results and discussion

3.1 Distribution of heavy metals in water from HonghuLake

3.1.1 Concentration of heavy metals in surface water

Table 1 presents concentrations of heavy metals in waterfrom the Honghu Lake. Results showed that the concen-trations of heavy metals in lake water show a greatvariation. Generally, average concentrations of thesemetals in the Honghu Lake decrease with the followingorder: As>Zn>Cu>Cr> Pb>Ni>Cd>Hg. ChineseEnvironment Quality Standard for Surface Water(GB3838-2002) classified water quality into five levels(SEPA, 2002), whereas Grade 1 is the highest standard setto protect national nature reserves. According to thisstandard, the concentrations of heavy metals in the water ofthe Honghu Lake are much lower than cutoff values for thegrade 1 water quality.To better understand the status of heavy metals in the

study area, concentrations of these pollutants werecompared with those reported in other rivers of the world(Table 2). The average concentrations of most heavymetals in the Honghu Lake are slightly higher than those inwater samples from the Shur River (Karbassi et al., 2008),Rivers of Latvia (Klavinš et al., 2000) and Chaohu Lake

Table 1 Concentrations of heavy metals and pH in surface water from Honghu Lake and the water quality guidelines/(µg$L–1)

Sampling sites pH As Cr Cd Pb Cu Hg Ni Zn

H1 8.06 3.41 1.86 0.054 2.26 3.10 0.019 1.36 5.05

H2 8.10 2.26 2.05 0.029 0.67 2.02 0.005 1.22 2.00

H3 8.28 2.32 1.98 0.036 0.78 1.85 0.005 1.21 2.13

H4 8.43 3.34 1.85 0.034 2.47 2.18 0.042 1.27 2.21

H5 8.52 2.56 1.74 0.022 1.55 1.64 0.005 1.27 1.19

H6 8.39 3.26 1.92 0.026 0.34 1.44 0.005 1.15 0.94

H7 8.32 2.14 1.30 0.026 1.84 1.20 0.005 0.69 0.88

H8 8.22 1.71 1.22 0.027 2.12 0.95 0.005 0.65 0.91

H9 8.00 4.31 1.51 0.080 4.75 3.03 0.005 1.78 7.53

H10 8.48 2.37 1.41 0.045 0.25 1.29 0.018 1.28 1.40

H11 8.57 2.85 1.70 0.045 0.40 1.49 0.005 1.41 2.21

H12 8.50 3.05 1.57 0.032 0.14 2.28 0.006 1.20 1.23

H13 8.21 2.47 1.57 0.022 0.08 2.22 0.018 1.21 0.72

H14 8.08 2.61 1.96 0.022 0.03 2.28 0.005 1.14 0.84

H15 7.93 3.72 1.99 0.044 1.46 1.94 0.005 1.17 2.64

Min 7.93 1.71 1.22 0.022 0.03 0.95 0.005 0.65 0.72

Max 8.57 4.31 2.05 0.080 4.75 3.10 0.042 1.78 7.53

Mean 8.27 2.83 1.71 0.036 1.28 1.93 0.010 1.20 2.13

Ⅰ* 6–9 £50 £10 £1 £10 £10 £0.05 £50

Note: Ⅰ*–Environmental Quality Standard for Surface Water (GB3838-2002)

Ying HU et al. Assessment of heavy metal contamination in surface water and sediments 41

(Li et al., 2011), but much lower than those reported in theKolleru Lake (Adhikari et al., 2009), Three GorgesReservoir (Qi et al., 2002), Danjiangkou Reservoir (Liet al., 2008) and the Yangtze River (Wu et al., 2009). Whencompared with background values in water from DongtingLake (Li et al., 1986), the Honghu Lake was polluted withAs, Cr, Pb, Cu and Ni, but less polluted with Cd, Hg andZn. These results suggested that the Honghu Lake waspolluted with some heavy metals. The Honghu Lake is alowland lake, where flooding and waterlogging occurfrequently. The relative high level of As in this area may bedue to the landform and hydrogeological conditions.Similar result has reported in water samples from HonghuCity, which provides further evidence for the high level ofAs (Li et al., 2010). The area where the Honghu Lake liesis one of the most important agricultural bases in China(Liu et al., 2010; Liu and Li, 2011). Fertilizers (forexample, phosphate fertilizer contains heavy metals suchas Cu, Ni, Cd and Pb) are used yearly on a regular basis,and this might be the reason for the presence of heavymetals (Ahmed et al., 2010; Li et al., 2011). It is reportedthat the amounts of fertilizer applied in the Honghu LakeBasin increased from 461 kg/hm2 in 1988 to 845 kg/hm2 in2004 (Gui and Yu, 2008). Moreover, industrial effluent anddomestic wastewater from Honghu City and Jianli Countyare discharged into this lake. The Honghu Lake is used fordrinking water source, cultivation and irrigation. Thus,continuous monitoring is needed to the heavy metalpollution in the surface water from the Honghu Lake.

3.1.2 Spatial distribution of heavy metals in surface water

According to the spatial distribution of heavy metalconcentrations in water samples from the Honghu Lake,Cr, As, Pb, Cu, Ni and Zn present similar distributions inthe lake water. This is further supported by the significantcorrelation among these elements (R: 0.94–0.96; p< 0.05).Nevertheless, there is not so much variation in theconcentration levels of Cd and Hg among the sampling

sites, indicating Cd and Hg have different geochemicalbehavior in this aquatic system. The relative higher level ofheavy metals was observed in the inlet area (H1, H9 andH15) since pollution sources are around these sites.Among these sampling sites, site H9 exhibits the highestwater concentrations of As, Cd, Pb, Ni and Zn, which isclose to Jianli County and the entry of the Yangtze River.There are two possible reasons that might explain the highconcentration of these heavy metals at this site. The firstpossibility is that agricultural runoff and wastewater fromthe surrounding area was discharged into the HonghuLake. On the other hand, it may be due to inflows from theYangtze River. This is further supported by the fact thatconcentrations of Zn, Cu, Cd, Ni, Cr and As in the YangtzeRiver are higher than in the Honghu Lake (Wu et al.,2009). The relative low concentrations of heavy metalswere observed at sites H8 and H10. Site H8 is at thewetland protection area, where wastewater discharge isforbidden by the government. Site H10 is close to theXintan drainage sluice, where is far away from the inletarea and water exchange ability is strong.Pearson correlation is used to evaluate the co-variance of

heavy metals (Li et al., 2011). The correlation coefficientsfor heavy metals and pH in the surface water samples(Table 3) present a positive correlation among Cd, Cu, Ni,Zn and As, among Pb, Cu, Ni and Cd, among Ni, Zn andCu. High correlations among these metals in the watermight indicate their same origin or similar enrichmentmechanism (Nguyen et al., 2009). There is a strongpositive correlation among Pb, Cd and Zn, suggesting thatthe anthropogenic sources of these metals are closelyrelated in the water from the Honghu Lake. However,negative correlations were found between pH and As, Cr,Cd, Pb, Cu, Ni or Zn, with the correlation coefficientsbeing – 0.31, – 0.27, – 0.33, – 0.38, – 0.51, – 0.09 and– 0.48, respectively. As shown in Table 1, pH values arelower at sites H1, H9, H15 where the concentrations ofthese metals are higher compared to other sites. Thisprovides further support by the fact that negative

Table 2 Average concentrations of heavy metals in water from other rivers over the world/(µg$L–1)

Sites As Cr Cd Pb Cu Hg Ni Zn

Kolleru Lakea) n.d. 36 16 24 n.d.

Dongting Lakeb) 0.9 0.89 0.06 1 1 0.025 0.4 4

Three Gorges Reservoirc) 10.129 1.125 3.244 6.463 0.018 30.636

Rivers of Latviad) 0.02 0.2 1 0.3 10

Danjiangkou Reservoire) 11.08 6.29 1.17 10.59 13.32 1.73 2.02

Shur Riverf) 0.026 0.116 0.771 0.688

Chaohu Lakeg) 0.73 0.89 1.55 0.36 1.09 7.59

Background valueh) 2 0.5 0.07 0.2 1.8 0.01 0.3 10

Yangtze Riveri) 13.2 20.9 4.7 55.1 10.7 13.4 9.4

This study 2.83 1.71 0.036 1.28 1.93 0.010 1.20 2.13

Note: n.d. means not detected; a) Adhikari et al. (2009); b) Niao et al. (1990); c) Qi et al. (2002); d) Klavinš et al. (2000); e) Li et al. (2008); f) Karbassi et al. (2008); g)Li et al. (2011); h) Li et al. (1986); i) Wu et al. (2009)

42 Front. Earth Sci. 2012, 6(1): 39–47

correlations between pH and heavy metals were observed.

3.2 Heavy metals in the sediment core from Honghu Lake

3.2.1 210Pb Chronology

As shown in Fig. 2, sediments of the Honghu Lake have210Pbex activities which range from 0.45 to 24.67 dpm/gwith a mean of 8.54 dpm/g. The 210Pbex activity is higherin the top layer than in the downward section. 210Pbexshows sharp peaks at 2 and 21 cm from the top of the core,suggesting anthropogenic activities may have resulted insignificant increase of the 210Pb activity due to the rapiddevelopment of industry and agriculture. At depths of 27–60 cm, a simple exponential decrease of 210Pbex with depthwas observed. Below the depth of 60 cm, the concentrationof 210Pbex presents an increase trend. The verticaldistribution of 210Pbex in this core indicates that theaccumulation rate varies greatly. Assuming that sedimentmixing is restricted to the surface mixed layer, the least-square fits for the logarithmic decrease of the 210Pbexactivity give a sedimentation rate of 0.44 cm/a. Thus thesection of 27–60 cm sediment represents about 75 years ofdeposition. The average accumulation rate in the HonghuLake is higher than that obtained from Jiaozhou Bay (Daiet al., 2007). It might be related to the high content of

suspended particles that were carried by rivers, floodingstreams, surface runoff flowing into this lake (Al-Masriet al., 2002).

3.2.2 Historical trends of heavy metals in the sediment core

Concentrations of heavy metals in the S1 from the HonghuLake present the following variation (Fig. 3). Overall, thedrastic changes were observed in the 0–30 cm section incomparison to deeper sediments. Increase of Cd in the top30 cm of the profiles reflects that this metal in thesediments might originate from the anthropogenic activ-ities around the Honghu Lake due to the rapid industrialdevelopment and urbanization. Industry sources, agricul-tural runoff in some heavily polluted soils resulting fromthe intensive use of phosphate fertilizer contained Cdmight be the main reason for Cd pollution in the HonghuLake (Ahmed et al., 2010). However, concentrations of Zn,Cu, Cr and Ni in the top layer show the same decreasingtrend compared to those in the sub-surface layer. Thesimilar distribution patterns are most likely related to theirsimilar geochemical behavior, which is consistent with thestrong correlations among these elements (R: 0.94–0.96;p< 0.01). Cu, Ni and Zn are frequently associated insediments as authigenic sulfide minerals (Ahmed et al.,2010). Hg, As and Pb show different distributions incomparison with the heavy metals mentioned above.As shown in Fig. 3, the levels of all metals had almost no

obvious change in the pre-1950s. Concentrations of allmetals decreased in the 1950s, especially for Cu, Zn, Crand Ni. Obvious decreases in concentration of Zn, Cu, Crand Ni were also found in the 1970s. Xintan drainagesluice, built in 1958, blocked the connection between thelake and the Yangtze River. In the 1970s, Luoshan maincanal and Four-lake main canal were also built. The factssuggest that these metals might be associated withhydraulic construction, which is likely to reduce pollutioninput into the lake. Elevated Hg, Cd, As and Cuconcentrations were observed in the 1974. These increasesin heavy metal contents suggest there might be an increase

Table 3 Pearson correlation coefficients of heavy metals and pH values in the surface water from Honghu Lake (n = 15)

Parameters pH As Cr Cd Pb Cu Hg Ni Zn

pH 1.00

As – 0.31 1.00

Cr – 0.27 0.31 1.00

Cd – 0.33 0.70* – 0.07 1.00

Pb – 0.38 0.50 – 0.24 0.67* 1.00

Cu – 0.51 0.69* 0.37 0.54* 0.38 1.00

Hg 0.17 0.17 0.04 0.040 0.15 0.24 1.00

Ni – 0.09 0.73* 0.35 0.70* 0.28 0.69* 0.15 1.00

Zn – 0.48 0.74* 0.07 0.93** 0.78** 0.72* 0.06 0.71* 1.00

Notes: 2-tailed test of significance is used; * correlation is significant at the 0.05 level; ** correlation is highly significant at the 0.01 level

Fig. 2 Profiles of 210Pbex activity for the S1 from Honghu Lake

Ying HU et al. Assessment of heavy metal contamination in surface water and sediments 43

in pollutant input into the lake through industrial sourcesand other sources. High concentrations of Cd, As, Cu, Zn,

Ni and Pb were observed in the 1990s. After this period,these metals decreased sharply until 2000. A heavy flood

Fig. 3 Vertical distribution of heavy metals in the sediment core (S1) of Honghu Lake

44 Front. Earth Sci. 2012, 6(1): 39–47

happened in the Yangtze River in 1998, which couldproduce dilution effects that resulted in the decreases ofthese pollutants. After the 2000, Pb showed an increasingtrend in concentration, while concentrations of Cu, Zn, Crand Ni showed decreasing trends.The Honghu Lake is a key producing area for freshwater

fish and an ideal habitat for migratory birds. To restore theecosystem, the Honghu Lake Wetland Protection andRestoration Demonstration Project (HLWPRDP) has beenimplemented since 2004. In this program, waste treatmentwas enforced by the government, and the amount ofindustrial waste discharged was reduced. The decreasetrend of these metals reflected the result of environmentalregulation by the local government. However, the increaseof Pb concentration was observed in this time, which mightbe the atmospheric deposit from coal burning of powergeneration plants and lead-gasoline used in vehicle (Yao etal., 2009; Liu et al., 2011).

3.3 Ecological risk assessment of heavy metals in thesediment core

Numerical sediment quality guidelines (SQGs) have beenwidely applied to evaluate the degree to which theconcentrations of heavy metals might adversely affectaquatic organisms (Harikumar and Nasir, 2010; Bai et al.,2011). In this study, the sediment quality guidelines aredeveloped for freshwater ecosystems to determine theecotoxicological potential of heavy metal pollution in thesediment core from the Honghu Lake (MacDonald et al.,2000). This method provides two sets of concentrations:the effect range low (ERL)/effect range median (ERM) andthe threshold effect level (TEL)/probable effect level(PEL). The ERL and TEL represent chemical concentra-tions below which adverse effects would be rarelyobserved. While the ERM and PEL are concentrationsabove which adverse effects are likely to occur (Bai et al.,2011). Furthermore, the potential acute toxicity ofpollutants in sediments can be estimated as the sum ofthe toxic units (TUs), which is defined as the ratio of thedetermined concentration to PEL value (Harikumar and

Nasir, 2010).From Table 4, it is evident that the concentrations of Hg

and Cd in more than 90% samples are below ERL,representing a range with which biologic effects occurrarely. More than 60% sediments with respect to Cu, Niand Zn are greater than TEL but less than PEL, suggestingthat adverse biological effect could occasionally beobserved. Cr and Pb in more than 80% sediment samplesand As in 22.7% samples exceed PEL, representing thatadverse biologic effects could frequently occur. TUs ofheavy metals were calculated (Fig. 4), which was rankedas: Cr> Pb>As>Ni>Zn>Cu>Hg>Cd. This showsthat Cr is the highest priority pollutant (25.5%�3.0%)while Cd is the least significant one (2.2%�0.9%). Thetotal TU of all heavy metals in 94.7% sediment samples ishigher than 4, indicating the presence of moderate toxicity(Pedersen et al., 1998; Bai et al., 2011).

4 Conclusions

The study of the distribution of heavy metals in surfacewater and the sediment core from the Honghu Lakesuggests that the lake is facing heavy metal pollution. Insurface water, abundances of heavy metals in water wereranked as: As> Zn> Cu> Cr> Pb>Ni> Cd>Hg.Some heavy metals exceeded background values, indicat-ing that the Honghu Lake is polluted with some heavymetals. Concentrations of heavy metals in the inlet areawere higher than those in other areas in the lake. Thespatial distribution of these metals indicated that theymight be related to fertilizers, industrial effluent anddomestic wastewater around the lake. Lower pH valueswere observed at sampling sites where the concentrationsof these metals were higher. This was consistent with thenegative correlation between pH and most metals.

210Pb chronology revealed that the average sedimenta-tion rate of S1 from the Honghu Lake is 0.44 cm/a. In thesediment core, the drastic changes were observed in the toplayer (0–30 cm) in comparison to the deeper layer. Increaseof Cd concentration in the top 30 cm of the profiles

Table 4 Risk assessment of heavy metals in the sediment core

ElementsGuidelines/(µg$g–1) Frequency/%

TEL PEL ERL ERM <TEL TEL-PEL > PEL <ERL ERL-ERM >ERM

As 5.9 17 33 85 0 77.3 22.7 100 0 0

Cr 37.3 90 80 145 0 17.3 82.7 10.7 89.3 0

Cd 0.596 3.53 5 9 94.7 5.3 0 100 0 0

Pb 18 36 35 110 0 12.0 88.0 2.7 97.3 0

Cu 35.7 197 70 390 5.3 94.7 0 100 0 0

Hg 0.174 0.486 0.15 1.3 100 0 0 100 0 0

Ni 35 91.3 30 50 4.0 96.0 0 1.3 29.3 69.4

Zn 123 315 120 270 37.3 62.7 0 33.3 66.7 0

Ying HU et al. Assessment of heavy metal contamination in surface water and sediments 45

reflected that this metal in the sediments might originatefrom the anthropogenic activities. Decrease in concentra-tion of Cu, Zn, Cr and Ni was likely associated with theHLWPRDP. Pb in sediments might be from atmosphericdeposit of coal burning, and lead-gasoline used in vehicle.The potential acute toxicity of pollutants in most sedimentssuggested that heavy metal concentrations in the HonghuLake should be of moderate concern, and Cr was thehighest priority pollutant.

Acknowledgements This work was financially supported by the NationalNatural Science Foundation of China (Grant No. 41073070) and the ResearchFund for the Doctoral Program of Higher Education, China (No.20090145110004). The authors are grateful to acknowledge the StateLaboratory of Biogeology and Environmental Geology. The authors alsowould like to appreciate the reviewers for their suggestions.

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Dr. Shihua Qi is a professor in the Schoolof Environmental Studies, China Univer-sity of Geosciences, Wuhan, China. Heobtained his B.S. degree in Geochemistry,Wuhan College of Geology, received hisM.S. degree in Geochemistry and Ph.D.in Paleontology and Stratigraphy fromChina University of Geosciences. Hiscurrent research focuses on fate and

behaviour of environmental organic pollutants and persistent organicpollutants, environmental geochemistry and remote sensing applica-tions to environment. He holds three patents and has published morethan 150 refereed journal articles and conference papers.

Ying HU et al. Assessment of heavy metal contamination in surface water and sediments 47