Chemometrics methods for the investigation of methylmercury and total mercury contamination in mollusks samples collected from coastal sites along the Chinese Bohai Sea

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Abstract

The development and application of chemometrics methods, principal component analysis (PCA), cluster analysis and correlation analysis for the determination of methylmercury (MeHg) and total mecury (HgT) in gastropod and bivalve species collected from eight coastal sites along the Chinese Bohai Sea are described. HgT is directly determined by atomic fluorescence spectrometry (AFS), while MeHg is measured by a laboratory established high performance liquid chromatography-atomic fluorescence spectrometry system (HPLC-AFS). One-way ANOVA and cluster analysis indicated that the bioaccumulation of Rap to accumulate Hg was significantly (P<0.05) different from other mollusks. Correlation analysis shows that there is linear relationship between MeHg and HgT in mollusks samples collected from coastal sites along the Chinese Bohai Sea, while in mollusks samples collected from Hongqiao market in Beijing City, there is not any linear relationship.

Introduction

Mercury is an important but toxic element. Both the direct drainage of industry wastewater and rainwater run-off leads to mercury contamination in oceans. The toxicity of mercury is well known since the notorious poisoning accident at Minamata Bay in southern Japan during 1950s and 1960s (Kurland et al., 1960). This tragic event was due to the consumption of methylmercury-contaminated fish and 48 persons died. Mercury is first absorbed by phytoplankton and then by various consumers within the oceanic ecosystem. Its virulence effect cannot be eradicated for many years. Although the discharging of mercury compounds directly to waterways has been increasingly regulated or prohibited since that time (Douglas, 1994), the deposited mercury still exists in sediments and releases to waters and mercury continues to be released to the atmosphere (Mason et al., 1994). Elevated levels have been found in water and fish samples even in areas far from major sources (Sorenson et al., 1990, Slemr and Langer, 1992, Nater and Gringal, 1992).

Mercury presents in several forms previous works have determined (Westöö, 1966, Hintelmann and Wilken, 1993, Ramalhosa et al., 2001, Liang et al., 2003). Because MeHg is the most toxic forms, the determination includes not only HgT content but also MeHg content.

Mollusks, which lie in the second trophic level in this ecosystem, are popular seafood and long-term consumption of them may result in MeHg accumulation in human body. In previous works, directions for monitoring marine pollution (Goldberg and Bertine, 2000) and implications in estimation of metal bioavailability in Mussel Watch programmes have been recommended (Soto et al., 2000, Szefer, 2000, Szefer, 2002). Organisms Mytilus spp. have been considered to be potential biomonitors of toxic metals in marine ecosystems (Fowler and Oregioni, 1976, Koide et al., 1982, Szefer et al., 1997, Szefer et al., 1999, Szefer et al., 2000, Chase et al., 2001).

Trace metal concentrations in mollusks are not just related to the metal concentrations in the environment. They are also affected by other factors, including mollusk size, growth rate, age, sex, allometric growth ratios, reproductive condition, position in the intertidal zone, sea water salinity, temperature and trace metal interaction with other pollutants in the environment. Even when all known sources of variation in the mollusks are taken into account, and a careful sampling is performed to avoid these sources of variation, variability is still encountered (Borchardt et al., 1988, Lobel et al., 1991).

So, in this study, nine kinds of mollusks were selected to investigate the pollution levels of MeHg and HgT in eight sampling sites and to try to find the biomonitors of mercury in the area of the coastal sites along the Chinese Bohai Sea. The sampling was carried out twice in July to August 2002 and 2003. In addition, in order to compare the relationship between MeHg and HgT, mollusks samples were collected from Hongqiao market, which locates in Beijing city, from the January to March 2003.

Section snippets

Sampling

Fig. 1 shows eight sampling sites. These sites spread out around the Bohai Sea. The collected mollusks were depurated in filtered seawater for approximately 24 h before transported to the laboratory with ice freezing. Stainless steel scalpel blades were used to cut open the mollusks and remove the soft tissues, which were then thoroughly rinsed with Milli-Q water to remove extraneous material and homogenized by blender and stored in glass bottles at −18 °C until analysis. Different species of

Concentration of HgT and MeHg

In order to prove the validity of the method, we analyzed certified reference materials and the recoveries are reported in Table 2. The found values of HgT and MeHg were in good agreement with the certified values, suggesting the proposed method was feasible in the determination of Hg in biota samples. The limit of detection (LOD) HgT and MeHg was 0.70 and 0.15 ng g−1, respectively.

Based on the investigation of Zhang (2001), the main Hg pollution area of Bohai Sea was the northland. In 2001,

Conclusion

The contamination levels of MeHg and HgT in nine species of mollusks sampled from eight coastal sites along the Bohai Sea were investigated. Comparing with twice samples (at an interval of one year), we found that the results were rather different. On the whole, the concentration of MeHg and HgT of the second is lower than the first. Because of the lack of reference points for comparison, the reasons of these were not known yet. The further work is going on. Chemometrics methods were performed

Acknowledgements

This work was jointly supported by National Natural Science Foundation of China (20137010, 20205008) and Chinese Academy of Sciences (KZCX2-414). We acknowledge Professor F.C. Adams for his kindly offering CRM DORM-2.

References (43)

  • R.P. Mason et al.

    The biogeochemical cycling of elemental mercury: anthropogenic influences

    Geochimica et Cosmochimica Acta

    (1994)
  • N. Mikac et al.

    Uptake of mercury species by transplanted mussels Mytilus galloprovincialis under estuarine conditions Krka River estuary

    The Science of the Total Environ

    (1996)
  • E.Ma. Peña-Méndez et al.

    Chemical fingerprinting applied to the evaluation of marine oil pollution in the coasts of Canary Islands (Spain)

    Environmental and Pollution

    (2001)
  • M. Soto et al.

    Changes in mussel biometry on exposure to metals: implication in estimation of metal bioavailability in ‘Mussel-Watch’ programmes

    The Science of the Total Environment

    (2000)
  • P. Szefer

    Distribution and behaviour of selected heavy metals and other elements in various components of the solution Baltic ecosystem

    Applied Geochemistry

    (1998)
  • P. Szefer

    Possible priorities for future research in the field of marine environmental pollution

    The Science of the Total environment

    (2000)
  • P. Szefer et al.

    Mercury and other trace metals (Ag, Cr, Co, and Ni) in soft tissue and byssus of Mytilus edulis from the east coast of Kyushu Island, Japan

    The Science of the Total Environment

    (1999)
  • P. Szefer et al.

    Distribution and relationships of mercury, lead, cadmium, copper and zinc in perch (Perca.uviatilis) from the Pomeranian Bay and Szczecin Lagoon, southern Baltic

    Food Chemistry

    (2003)
  • S.F. Wang et al.

    The Evolution of Heavy metal Pollution During last hundred years in the dalian bay

    Chinese of Journal of Earth Science Frontiers

    (2002)
  • T. Borchardt et al.

    Trace metal concentrations in mussels: comparison between estuarine, coastal and onshore regions in the southeastern North Sea from 1983 to 1986

    Marine Ecology

    (1988)
  • G.W. Bryan et al.

    A guide to the assessment of heavy metal contamination in estuaries using biological indicators

    Occ Publ Mar Biol Assoc. UK, Citadel Hill, Plymouth, Devon, England

    (1985)
  • Cited by (0)

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