Effect of Extended Storage Time on the Toxicity of Sediment-Associated Cadmium on Midge Larvae ( Chironomus tentans )

Abstract

The effect of the duration of spiked sediment storage on cadmium toxicity was studied. Sediment samples were spiked with cadmium to obtain concentrations of 0.6,16.0, 29.0 and 53.0 μg Cd per g sediment (dry weight). The spiked sediment was then stored in sealed plastic containers at 4°C in the dark. Sediment bioassays, using Chironomus tentans , were conducted immediately and at periodic intervals for up to 4 months. Though the levels of cadmium in the bulk sediment samples from different stored periods were not significantly different, different toxicity levels to C. tentans were observed. The toxicity was significantly different between subsequent storage times. There was a significant decrease in the bioaccumulation factor (BAF) values with extended storage times, indicating a reduction in the bioavailability of cadmium. This study suggests that the storage of spiked sediment used in sediment toxicity study can influence the results.