Toxicity of three forms of copper to the Chironomus tentans in both the aquatic and sediment media

Abstract

The toxicity of copper (Cu) to the Chironomus tentans was studied using both aquatic and sediment-based media. This was done so as to compare toxicity values from aquatic versus sediment exposure. This investigation also examined the pore water concentration of Cu and attempted to link sediment toxicity to metal availablity in pore water. Three salts of Cu where used to study variability in toxicity. The LC50 values for the three Cu salts were 17.2 mg L⁻¹ for Cu chloride; 18.55 mg L⁻¹ for Cu sulphate and 18.21 mg L⁻¹ for Cu nitrate. For the two sediment types used in this investigation, the LC50 values were observed to be 44.8 mg L⁻¹ and 55.1 mg L⁻¹ for clay loam and sandy loam, respectively, for Cu chloride. LC50 values for Cu sulphate and Cu nitrate were also calculated. Pore water studies indicated that the LC50, when calculated from pore water concentration, was actually closer to the 96 hr LC50 value obtained from aquatic toxicity tests, with LC50 values of 17.3 mg L⁻¹ for Cu chloride in clay loam. This trend was observed for all three metal salts in both sediment types. Data indicate that pore water concentrations play an important role in sediment-based metal toxicity.

Keywords:

• copper
• toxicity
• Chironomus tentans
• pore water
• sediment
• aquatic toxicity tests