The influence of solid matrices on arsenic toxicity to Corophium orientale

Abstract

In marine ecosystems, benthic organisms are really important because they are the first step in the transfer of contaminants from environment to biota. To this end, this study focused on biological assays with the amphipod Corophium orientale exposed to two different molecules of arsenic: arsenate (As^V), the most abundant form in sediments, and dimethyl-arsinate (DMA), expected to be moderately toxic as an intermediate in the process of detoxification. The toxicity of arsenic compounds was measured after exposure to three different matrices: water, spiked natural sediment and inert spiked quartz sand. LC₅₀ values were calculated for each exposure, and the results confirmed the highest toxicity of As^V, in addition to underlining the importance of matrix of exposure. Water exposure was the matrix which presented the highest toxicity for inorganic arsenic (As^V LC₅₀=3.51 mg L⁻¹ vs DMA LC₅₀=54.65 mg L⁻¹), spiked natural sediment demonstrated its capability to chelate arsenate toxicity (As^V LC₅₀=34.27 mg kg⁻¹ vs. DMA LC₅₀=52.19 mg kg⁻¹) and spiked quartz sand presented intermediate values for As^V (LC₅₀=25.26 mg kg⁻¹), whereas for DMA a lower toxicity was registered (LC₅₀=872.35 mg kg⁻¹). This study can provide some useful data linked with chemical speciation of arsenic and exposure matrix, for improving the correct management of contaminated sediment.

Keywords:

• arsenate
• dimethyl-arsinate
• chemical speciation
• spiked sediment
• spiked quartz sand