Soil Heavy Metal Contamination and Risk Assessment Around the Fenhe Reservoir, China

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  • Soil Heavy Metal Contamination and Risk Assessment Aroundthe Fenhe Reservoir, China

    Hong Zhang Guanglei Liu Wei Shi

    Jinchang Li

    Received: 21 November 2013 / Accepted: 21 May 2014

    Springer Science+Business Media New York 2014

    Abstract Heavy metal contamination in the soil around a

    water source is a particularly serious issue, because these

    heavy metals can be transferred into the water source and

    can pose significant human health risks through the con-

    tamination of drinking water or farmland irrigation water.

    In this paper, we collected surface soil samples from the

    area surrounding the Fenhe Reservoir. The concentrations

    of As, Cd, Cr, Cu, Hg, Ni, and Zn were determined and the

    potential ecological risks posed by the heavy metals were

    quantitatively evaluated. The primary inputs for As, Ni,

    and Zn were natural sources, whereas the other elements

    were derived from mainly anthropogenic sources. Hg dis-

    plays more serious environmental impacts than the other

    heavy metals. The upper reaches of the reservoir, located in

    the northwest, display a higher potential ecological risk.

    Keywords Heavy metals Sources identification Ecological risk Spatial distribution

    The contamination of urban and peri-urban soils by heavy

    metals has received increasing public attention and cor-

    relative surveys have been carried out in several munici-

    palities (Birke and Rauch 2000; Rizo et al. 2013).

    However, the contamination pattern in soils of water source

    areas, especially in developing countries, remains inade-

    quate, which is a particular problem because these heavy

    metals can be transferred from the soil into reservoirs,

    rivers, or underground water, which will pose a severe

    threat to human health if it contaminates drinking water or

    farmland irrigation water (Zahra et al. 2014; Suresh et al.

    2012). Therefore, fully understanding (quantifying and

    mapping) the spatial characteristics of soil contamination

    by heavy metals in water source areas will facilitate

    accurate risk assessment and planning of mitigation and/or

    remediation (Lin 2002).

    The Fenhe River, which is the second-largest tributary

    of the Yellow River, possesses a length of 716 km and a

    watershed area of 39, 000 km2, and flows through the

    central and southern areas of the Shanxi Province of China.

    The Fenhe Reservoir, located in the upper reaches of the

    Fenhe River, is the largest reservoir and drinking water

    source area in Shanxi Province. We conducted the present

    study to survey soil heavy metal contamination around the

    Fenhe Reservoir. The aims of this study are: (1) to deter-

    mine and compare the concentrations of heavy metals in

    soils surrounding the Fenhe Reservoir with those of other

    areas; (2) to identify their possible sources; and (3) to

    assess the potential ecological risks posed by these heavy

    metals.

    Materials and Methods

    About 50 soil samples were collected around the Fenhe

    Reservoir during April 2011. The detailed sampling loca-

    tions are shown in Fig. 1. Each sample was a composite of

    soil subsamples taken from the top 20 cm of 10 sites. At

    each site, we obtained about 1 kg of soil using a stainless-

    steel spade, and stored the samples in sealed polyethylene

    bags. Site descriptions were registered at the time of

    sampling to record the sample locations, elevations, land

    use types and major environmental features.

    H. Zhang (&)College of Environmental Science and Resources, Shanxi

    University, Taiyuan 030006, China

    e-mail: zhanghong@sxu.edu.cn

    H. Zhang G. Liu W. Shi J. LiInstitute of Loess Plateau, Shanxi University, Taiyuan 030006,

    China

    123

    Bull Environ Contam Toxicol

    DOI 10.1007/s00128-014-1304-8

  • Each sample was air-dried, ground with agate mortar and

    sieved to 200 mesh size and homogenized with cut sizes of

    0.075 mm. All procedures of handling were carried out

    without contacting any metals in order to avoid potential

    cross-contamination of the samples. For analysis of Cr, Cu,

    Zn, Ni, and Pb, samples were pressed into pellets having a

    diameter of 3.1 cm under the pressure of 20 ton per cm2 and

    then exposed to X-rays from a rhodium tube. The mea-

    surements were carried out using a Rigaku ZSX 100e

    wavelength dispersive X-ray fluorescence spectrometer. For

    analysis of As and Hg, the soil samples were digested with

    concentrated HNO3 and HCL in a microwave-accelerated

    reaction system and were quantified using Atomic Fluores-

    cence Spectrometer. For analysis of Cd, the soil samples

    were digested with concentrated HF and H2SO4 in a

    microwave-accelerated reaction system and were quantified

    using graphite atomic absorption spectrometer.

    Appropriate quality assurance procedures and precau-

    tions were carried out to ensure reliability of the results.

    Double distilled deionized water was used throughout the

    study. Reagents blank determinations were used to correct

    the instrument readings. Standard reference soil (GSS-

    11\10\14) obtained from the China National Center for

    Standard Materials were used for validation of the analyt-

    ical procedure. Table 1 shows the analytical limits of

    detection and relative standard deviation (RSD) of each

    heavy metal.

    Many factors can influence the concentrations of heavy

    metals in soil and their impacts upon ecosystems. Principal

    components analysis (PCA) has been widely used to

    identify the sources of soil pollutants (Mico et al. 2006;

    Gurhan and Semiha 2008). In the present study, we per-

    formed PCA using SPSS 13.0 for Windows.

    The potential ecological risks posed by the heavy metals

    were quantitatively evaluated using Hakansons method

    (1980; Muge et al. 2013). These risk indices are calculated

    as follows:

    Eir Tir CisCin

    1

    RI Xn

    i1Eir 2

    where Eir is the potential ecological risk index of an indi-

    vidual metal i; Tir is the toxic-response index for heavy

    metals i, Hakanson (1980) suggested that appropriate Tirvalues for As, Cd, Cr, Cu, Hg, Ni, and Zn were 10, 30, 2, 5,

    40, 5, and 1, respectively. Cis is the measured concentration

    of metal i at sampling sites s, Cin is the background value

    (BGV) of heavy metal i in the research area. RI is the

    potential ecological risk index that results from the com-

    bination of multiple metals. The higher the E and RI are,

    the higher the risk is. Table 2 summarizes the potential

    ecological risk indices and corresponding risk grades.

    Results and Discussion

    Table 3 summarizes the results of heavy metal concentra-

    tions in soils in the research area. The median was selected

    as a representative of central tendency because the data

    does not require a normal distribution. We have provided

    Fig. 1 Location of the studyarea and sampling sites

    Table 1 The limits of detection and RSD of each heavy metal

    Heavy metal Limits of detection (mg kg-1) RSD (%)

    As 0.42 3.09

    Cd 0.029 6.64

    Cr 5 3.25

    Cu 1 5.54

    Hg 0.003 1.80

    Ni 2 3.73

    Zn 2 1.62

    Bull Environ Contam Toxicol

    123

  • the Grade I and Grade II values in the Chinese Environ-

    mental Quality Standard for Soil as well as the soil BGV

    for the Taiyuan Basin in Table 3. In the Chinese standard,

    Grade I levels represent the average natural background

    levels for uncontaminated soil of China, and Grade II

    levels represent the levels at which a pollutant is hazardous

    to agricultural production and human health.

    The concentrations of heavy metals in the research area

    are lower than the Grade I and Grade II criteria, suggesting

    that the soils of the research area has not been contami-

    nated related to the average natural background levels of

    heavy metals in soils of China and were currently not

    hazardous to agricultural production and human health.

    However, Cr and Hg displayed relatively higher mean

    concentrations than the corresponding background levels

    for soil in the Taiyuan Basin, suggesting that both elements

    were more likely to be affected by anthropogenic sources.

    The coefficients of variation (CV) values were all relatively

    small for the seven elements, suggesting that these

    elements were derived predominantly from natural sources

    or from dispersed anthropogenic sources.

    In this study, the concentrations of heavy metals of soils

    in this research area were in the approximate order of

    magnitude when compared with those in other areas of

    China (Table 4). The concentrations of heavy metals in

    different research areas were various, which may be

    attributed to the different natural background and human

    activities.

    PCA was applied here to identify the sources of soil

    pollutants. The results of the efficiency of the method are

    indicated in Table 5. It can be seen that the first 4 factors

    explain over 86.61 % of the total variation. The first PC,

    which explained 37.15 % of the total variance, was

    strongly and positively related to As, Ni, and Zn. As, Ni,

    and Zn showed significant correlations and their mean

    concentrations were comparable to the corresponding

    background levels in the research area. Therefore, it seems

    reasonable to infer that PC1 is related to natural sources at

    Table 2 Indices and grades of

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