Chromium (Cr) accumulation in the freshwater crab, Zilchiopsis collastinensis.

The freshwater crab, Zilchiopsis collastinensis was exposed in vivo to determine Cr accumulation in visceral content. After an acclimation period we added Cr (K2Cr2O7 ) at nominal concentrations of 2 mg l-1 Cr(VI) and 5 mg l-1 Cr(VI) and a control (T0) under the same conditions, without Cr. At days 1, 7 and 14, Cr was measured in water, sediments and crabs and the bioconcentration factor (BCF) in relation to water and to sediment were obtained. Considering all samples and all the study period, crabs registered 3 times more Cr than sediments and 18 times more Cr than water. Cr levels in Z. collastinensis tissues were always lower in the control than in T1 and T2; no significant differences among days 1, 7 and 14 were found in the control. In the treatments, no significant increase in Cr levels in tissues were found between days 1 and 7, neither between days 7 and 14 in both concentrations tested. Significant differences were found between the control and T1 and T2 (p<0.001), but not between T1 and T2. The highest BCF obtained for Z. collastinensis were 51.82 and 51.42 in T1 and T2 in water at 14 days of exposure. This study shows the efficiency of freshwater crabs to accumulate Cr from water.

Accumulation of chromium and interaction with other elements in Chlorella vulgaris (Cloroficeae) and Daphnia magna (Crustacea, Cladocera).

Assays with Chlorella vulgaris Beijerinck Novakova, 1890 and Daphnia magna Straus, 1820 were performed to determine Cr and other elements concentration in tissues of both species by instrumental neutron activation analysis (INAA), after being exposed to 150, 280 and 350 .g l-1Cr (VI). Interaction among Cu, Zn, Fe and Cr were also registered. In the control of C. vulgaris, the amount of Cr was < 4μg g-1; in the treatments with Cr (VI) the values were 47, 82 and 100 folds greater than the control for the lowest, intermediate and highest concentrations tested respectively. In the control of D. magna, the amount of Cr was <3 μg g-1; in the treatments with Cr (VI) the values were 14, 13 and 27 folds higher than the control for the lower, intermediate and higher Cr (VI) concentrations respectively, and from 3 to 9 times less than for C. vulgaris These results show that C. vulgaris is very efficient accumulator of Cr (VI) from polluted waters, and in consequence, it is proposed to be used in phytoremediation procedures.