Metal bioavailability during the periodic drying and rewetting process of littoral anoxic sediment

Bioavailability Assessment of Metals from the Coastal Sediments of Tropical Estuaries Based on Acid-Volatile Sulfide and Simultaneously Extracted Metals

“…They consist of minerals of varying sizes including clay, silt, and sand. Sediments in marine environments are the main reservoirs of organic and metallic pollutants [3,4].…”

“…Under reducing conditions, metals can be incorporated into the solid phase of the sediment to form amorphous monosulfides, operationally defined as volatile sulfides, in reaction with an acid (acid volatile sulfides, AVS). The formation of AVS is related to the anoxic conditions of the sediment and the content of labile organic matter and sulfate, which leads to a higher activity of sulfate-reducing bacteria [4,8]. According to Di Toro et al (1990), insoluble metal sulfide complexes regulate the metal concentration in the pore water of the sediment, due to the formation of AVS.…”

“…These sulfides may also play important roles in controlling the bioavailability of metals in anoxic sediments. Research has established that the relative amount of simultaneously extracted metals (SEM) and AVS is important in predicting bioavailability [4,9,10]. If the molar amount of SEM is less than the amount of AVS, the toxic metals in the sample will potentially not be bioavailable in interstitial waters, as there is enough AVS to react with these metals and remove them from the solid-phase solution [11].…”