Investigation of arsenic behaviour in a marine environment
The conversion of arsenic into organoarsenic compounds is affected by the action of organisms, particularly marine organisms. These arsenic species require a suitable technique to distinguish the species and quantify their abundance. The ICP-MS coupled to either HPLC or HG-CT are the most popular techniques for arsenic species could be separated, but the limit of detection (LOD) was not satisfactory for the concentration of arsenic in natural waters and the chloride interference in the marine samples was high. While the HG-CT-ICP-MS, the LOD was sufficient to detect very low concentrations of arsenic, particularly for methylated arsenic species, and there was no chloride interference, however the inorganic arsenic in the reagents was high and only the reducible arsenic species could be detected. The transformation of organoarsenic compounds, specifically the conversion of arsenosugars by micro-organisms in sediment, was studied by analysing porewater from decaying seaweed in a mesocosm experiment. Arsenosugars degraded to DMAE further to DMAA to MMAA and finally to As(V) and As(III), but not as previously proposed to AsB, AsC and TMAO. Arsenic was released by the dissolution of manganese and iron clay particles in a pristine area but much more by anaerobic degradation in an industrial area. Arsenic was removed from the water phase to the sediment by precipitation, particularly with manganese at the surface sediment only in the pristine area but with iron in the industrial area.