Effect of pH on uptake, tissue distribution and retention of hexavalent chromium in rainbow trout ( Salmo gairdneri)

Abstract

Uptake, distribution and retention of chromium in rainbow trout ( Salmo guirdneri) was studied after short-term (2–4 days) exposure to 51CrO 4 2− -containing Na 2CrO 4 solutions of different concentrations (2–50 mg/l Cr) and pH (7.8 and 6.5). At pH 7.8, highest contents of chromium were found in gill, liver, kidney, and digestive tract of the trout. Chromium was not distributed evenly among the different subcellular fractions of the tissues, but was concentrated in the nuclear fraction of the gill tissue and in the soluble fraction of the kidney and liver tissue. Upon transfer of exposed fish to tap-water, chromium was rapidly eliminated from blood, gill and digestive tract. However, chromium contents tended to remain high in kidney and liver. When the pH was decreased from 7.8 to 6.5, the lethal action of hexavalent chromium increased and a different pattern of accumulation and elimination of chromium was observed. The major differences were found in the gills, which concentrated significantly more chromium at pH 6.5 than at pH 7.8, irrespective of the exposure time and concentration. As an electronspin-resonance signal characteristic for trivalent or pentavalent chromium was detected in the gills, the differences must have been at least partly due to the higher oxidizing action of hexavalent chromium at the lower pH.