Heavy metals in muscle tissues and organs of fish species from Lake Baihua

Concentrations and distribution characteristics of six heavy metals (Pb, Cd, Cu, Cr, As and Hg) in Hypophthalmichthys molitrix and Cyprinus carpio sampled from Baihua Lake were studied by analysis of these heavy metals in their organs (gills, liver, kidney and heart) and muscle tissues (back muscle, abdominal muscle and tail muscle), and their associations with these heavy metals in the water were also examined. The results showed that the average levels of these heavy metals in H. molitrix and C. carpio decreased in the order of Cu> Pb> Cr> Cd> As> Hg; and Cr and Cu showed a significant correlation in the four organs of H. molitrix and C. carpio with the correlation coefficients of r = 0.878 (P < 0.01) and r = 0.972 (P<0.01) respectively, while Cr and Hg in C. carpio presented only a negative correlation with the coefficient of r = -0.782 (P<0.05). There were significant correlations between concentrations of the heavy metals in the organs of these fish species, but the average levels of these heavy metals in each organ presented low correlations with those in the sediment and overlying water samples. A cluster analysis showed that the six heavy metals in the two fish bodies could be divided into three categories. The content of as in the heart of C. carpio was relatively high, but the content of as in the different organs of H. molitrix had little difference. The level of Hg was relatively uniform in the organs and tissues of the two fish species, the content of these six heavy metals in edible muscle tissue of the fish was generally low. Since heavy metals in sediments from Baihua Lake mainly existed as sulfide compounds that were of low bioavailability, the fish species in this lake were not polluted severely with heavy metals.