| Resource & environmental sciences |
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| Bioaccumulation kinetics of hexavalent chromium in the tissues of Exopalaemon carinicauda and Portunus trituberculatus |
| Li Lei, Shen Xinqiang, Li Chao, Wang Yunlong, Jiang Mei, Wu Qingyuan, Niu Junxiang, Xu Gaopeng |
| (1. East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai 200090, China; 2. College of Marine Sciences, Shanghai Ocean University, Shanghai 201306, China) |
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Abstract Chromium (Cr) is considered to be one of the major heavy metal pollutants in marine environment, and in existence of two valence states: hexavalent chromium ［Cr(Ⅵ)］ and trivalent chromium ［Cr(Ⅲ)］. The source of Cr pollution in marine environment was mainly from discharge of effluents by a variety of industries. Cr(Ⅵ) is considered as the most toxic form of Cr, whereas Cr(Ⅲ) is much less toxic. Cr(Ⅵ) is nonbiodegradable and can rapidly accumulate in creatures and reach toxic levels in short periods of time. Although the bioaccumulation of heavy metals in many creatures has been well studied, details on mechanisms and differences of Cr(Ⅵ) bioaccumulation in different marine creatures remain unclear.
In this paper, the bioaccumulation processes of Cr(Ⅵ) in muscle tissues of crustaceans Exopalaemon carinicauda and Portunus trituberculatus were investigated, and the kinetic parameters of the Cr(Ⅵ) accumulation and elimination were determined using the semi-static two-compartment kinetic model, which included biouptake rate constant (k1), bioelimination rate constant (k2), bioaccumulation factor (BCF), and biological half-life (B1/2).
The kinetic model described the transport of Cr(Ⅵ) between ambient seawater and muscle tissue of two kinds of crustaceans. The modeling results indicated that the range of k1, k2, BCF, Cr(Ⅵ) content under an equilibrium condition (CAmax) and B1/2 was 3.37 to 20.65, 0.058 to 0.121, 58.10 to 171.00, 8.55 to 290.52 mg/kg, 5.74 to 11.95d, respectively, and the average value of k1, k2, BCF, CAmax and B1/2 was 11.00, 0.089, 110.13, 116.57 mg/kg and 8.50 d for Cr(Ⅵ) in the muscle tissue of E. carinicauda. However, the range of k1, k2, BCF, CAmax and B1/2 was 4.36 to 12.44, 0.115 to 0.154, 37.91 to 80.81, 4.85 to 56.87mg/kg, 4.50to6.03 d, respectively, and the average value of k1, k2, BCF, CAmax and B1/2 was 7.70, 0.131, 56.53, 25.66 mg/kg and5.38 d for Cr(Ⅵ) in the muscle tissue of P. trituberculatus. It was found that the k1, k2 and BCF generally decreased and the CAmax and B1/2 increased in the muscle tissues of E. carinicauda and P. trituberculatus with the increase of Cr(Ⅵ) exposure concentration in ambient seawater.
In sum, the bioaccumulation content of Cr(Ⅵ) in the muscle tissue of E. carinicauda is higher than that in P. trituberculatus, and the bioaccumulation rate in early stage is higher than in later stage. Meanwhile, the elimination rate of Cr(Ⅵ) in the muscle tissue of P. trituberculatus is faster than that in E. carinicauda, and the elimination process of Cr(Ⅵ) is mainly in the initial stage, and the elimination ability of E. carinicauda is weaker than that of P. trituberculatus.
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Published: 20 July 2015
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六价铬离子在脊尾白虾和三疣梭子蟹体内的富集动力学
通过15 d的富集以及之后15 d的清水释放实验，应用双箱动力学模型拟合获得了六价铬离子［Cr(Ⅵ)］在脊尾白虾(Exopalaemon carinicauda)和三疣梭子蟹(Portunus trituberculatus)体内的富集与释放动力学参数，同时分析探讨其动力学参数的变化特征及差异.拟合结果表明：脊尾白虾和三疣梭子蟹对Cr(Ⅵ)的吸收速率常数k1范围分别为3.37~20.65和4.36~12.44，平均值分别为11.00和7.70；释放速率常数k2范围分别为0.058~0.121和0.115~0.154，平均值分别为0.089和0.131；生物富集因子(bioaccumulation factor，BCF)范围分别为58.10~171.00和37.91~80.81，平均值分别为110.13和56.53；在平衡状态下2种海洋生物体内Cr(Ⅵ)含量（CAmax）范围分别为8.55~290.52和4.85~56.87 mg/kg，平均值分别为116.57和25.66 mg/kg；生物半衰期（B1/2）范围为5.74~11.95和4.50~6.03 d，平均分别为8.50和5.38 d.2种海洋生物对Cr(Ⅵ)质量的吸收速率常数k1释放速率常数k2和BCF均随外部水体中Cr(Ⅵ)质量浓度的增大而减少CAmax和B1/2随外部水体中Cr(Ⅵ)浓度的增大而增大.脊尾白虾对Cr(Ⅵ)的富集能力高于三疣梭子蟹，富集速率前期高于后期；而其对Cr(Ⅵ)的释放能力弱于三疣梭子蟹，且释放主要集中在前期.
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