Distribution of Heavy Metals in Muscles of Fish: Concentrations and Change Tendencies

Abstract

Concentrations of six heavy metals (Pb, Cd, Cr, Ni, Cu, V) in muscles of freshwater fish have been determined in this work. Samples are taken from 20 freshwater reservoirs in Lithuania. The concentrations of HMs have been determined using the ICP-MS model "Element" (Finnigan MAT). It is found that in 20 % of samples the concentration of Pb exceeds the Maximum Tolerable Limit (MTL). The highest Cd concentration - 0.14 mg/kg - almost 1.5 times higher than the MTL is found in the sample from the Elektrėnai Pond which collects cooling water from the thermal electric power station. In other samples of fish muscle the Cd concentration does not exceed the MTL and ranges from 0.042 mg/kg to 0.058 mg/kg.

When comparing the results of the present research with the data from 1998, it is found that the concentrations of HMs are increasing. Increase in the concentrations of Pb and Cd is particularly significant. As an example, an increase in the amount of Pb in 3 samples ranges between 11.3 % and 14 %, in one sample - almost 27 %, in 4 samples - from 50 % to 66 %, in one sample - 89 %, and in one - almost 18 times. The concentration of Cd in 2 samples has increased almost by 20 %, in 5 samples, on average - by 40-70 %, in one sample - 86 %, and in one sample - 3 times. The concentration of other HMs in fish muscles has increased in the following way: the arithmetic average of Cr concentration increase is 82. 4 %, Cu and V increase, on average - 28 %, Ni - 17 times. In order to develop the fishing industry in freshwater reservoirs it is important to maintain the water quality standards, and to regularly monitor the levels of accumulation of HMs in water, sediments and fish.