| A great number of mining areas along the Xiang River in Hunan Province results in pollution of heavy metal in Xiang River, including arsenic, chromium, zinc, manganese, mercury, cadmium, lead, nickel, copper, etc.With the pollution of aquatic environment, the whole ecological system of Xiang River has been affected, such as pollution of water and sediment, shape decreasing in species and number of plankton, interrupting of the breeding of fish and so on. This makes monitor and govern the heavy metal of Xiang River a top priority.In order to evaluate the pollution degree of heavy metals in aquatic environment and aquatic products such as fish in Xiang River, this paper mainly studies that:Concentration of heavy metal in water,sediment and silver carp from Xiang River and the evaluation of the pollution degree; Analysis of the differences of heavy metal enrichment between silver carp and aristichthys nobilis in east Dongting Lake; Distribution of heavy metals in silver carp organs and correlation analysis between accumulation of heavy metal and weight of silver carp; Migration regularity of heavy metals from environment （water and sediment） and food （plankton） to aristichthys nobilis. The main research results are as follows:There are differences of heavy metal pollution in water and sediment among Hengyang, changsha sections of Xiang River and east Dongting Lake.Cd and Hg in water are not detected, the highest personal annual health risk values of carcinogenic heavy metals Cr and As reach 7.344×10-5a-1 and 7.389×10-5a-1 respectively, partly beyond the maximum acceptable risk value of 5.0x10-5a"’which is recommended by ICRP, and the personal annual health risk values of non-carcinogenic heavy metals Pb, Zn, Cu are lower than the recommended value of 5.0×10-5a-1; The heavy metals Cr, Cu, Zn, As and Pb in sediment from all sampling sites belong to low potential ecological risk, Hg in sediment belongs to middle potential ecological risk, Cd in sediment belongs to serious potential ecological risk. Sorted by average potential ecological index of heavy metals is Cd> Hg> As> Cu> Pb>Zn> Cr, and sorted by average potential ecological comprehensive index of three sections is Hengyang section>Changsha section>east Dongting Lake.There are differences of heavy metal accumulation among different organs in a fish and among same organ in different types of fish. The sequence of tissues of silver carp and aristichthys nobilis arrayed by the concentration of heavy metal is consistent, the sequece arrayed by the concentration of Cr is gill> liver> brain> meat, Cu is liver> brain> gill> meat, Cd is liver> gill> brain> meat, Pb is gill> liver> meat>brain, Hg is meat>liver>brain> gill, on the whole, compare to gill and liver, meat and brain have weaker affinity for heavy metals; According to the BSFAs of fish, compare to Cr and Pb, silver carp and aristichthys nobilis are more likely to enrich Cu, Cd and Hg, and silver carp is easier to enrich Cd, while aristichthys nobilis enrichs Hg easier; Differences of enrichment of heavy metals in different fishs do exist, while the sequence of tissues in different types of fish arrayed by the concentration of heavy metal is consistent due to the same physiological function.The concentration of heavy metal in silver carp is related to weight of the fish. The correlations of weight of silver carp and concentration of Cd in the muscle, Pb in the liver, Hg and As in all the tissues are positive, while in other cases, the correlations are negative; Significant positive correlations are found between tissues of silver carp; The correlations among Cr, Cu, Se, Cd, Pb, Zn are positive, while negative correlations are more common in regarding to Hg and As.Migration of heavy metals from environment or food to aquatic organisms has its regularity. Sort the heavy metals in plankton by concentration is Zn>Cu>Pb>Cr>As>Hg>Cd; And sort the heavy metals by concentration in aristichthys nobilis is Zn>Cu>Pb>Cr>As>Hg>Cd, all the concentrations of heavy metals are lower than China’s national and industry standards; Heavy metals’ concentrations in plankton mainly depend on the concentrations in water, at the same time under the influence of concentrations in sediment. Cd and Pb in aristichthys nobilis mainly come from the environment, while Zn and Hg mainly come from food.To sum up, although the concentration of Cd in silver carp and aristichthys nobilis exceed the limited value of industry standard, the concentration of heavy metals in edible parts of fish are lower than the standard limited value, and belongs to the category of the safe to eat. |
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