Mercury methylation upon coastal sediment resuspension: a worst-case approach under dark conditions

Abstract

Mercury behavior upon resuspension of sediments from two impacted areas of Guanabara Bay was evaluated to assess worst-case methylmercury (MeHg) responses, under dark experimental conditions. Total mercury (THg) and MeHg concentrations were determined along 24 hours experiments of sediment resuspension in the bay water. Fine-grained Meriti River estuary (MR) sediments had 8-times higher MeHg initial concentrations than sandy Rio the Janeiro Harbor (RJH) sediments (3.4 ± 0.29 vs. 0.41 ± 0.1 ng g − 1 , respectively).THg contents were uncorrelated with resuspension time, while correlations of resuspension time with MeHg (r 2 = 0.66) and %MeHg in relation to THg (r 2 = 0.75) were observed only for RJH sediments. These ndings correspond to a 2.8-times MeHg concentration increase (ΔMeHg = 0.75 ng g − 1 ) and 4.4-times increase in %MeHg (Δ%MeHg = 1.0%) for station RJH.This suggests that assessments of MeHg spatial-temporal variability can be limited if concentration changes due to sediment resuspension are not considered.

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

“…The discussion on bioavailability and toxicity of metals in sediments using SEM-AVS models in two types of estuaries, one eutrophic and the other mesotrophic, is poorly discussed in an integrated way, which leaves a gap in the literature. Thus, this study contributes to the understanding of the geochemical characteristics and dynamics of AVS in sediment and its relationship with some factors that regulate bioavailability, such as organic matter [2,8].…”

“…Sediments are formed by the deposition of suspended particles from rivers, lakes, estuaries, and oceans. They function as important compartments of aquatic ecosystems and serve as habitats for many species of organisms [1,2]. They consist of minerals of varying sizes including clay, silt, and sand.…”

“…This ratio has been recognized as a key process for determining trace metal behavior in coastal sedimentary environments where anaerobic conditions occur [2,8,12]. This function of sulfides is related to the incorporation of available metals into the dissolved phase by the solid phase of sediments through the formation of metal monosulfides (or the adsorption of metals to them), predominantly composed of FeS [11,13].…”

“…The industrial complex comprises diverse industries, such as gas and oil, pharmaceuticals, and metallurgy. Furthermore, the bay surrounds the largest oil refinery in the country and the former Gramacho landfill, which was considered the largest in South America until 2012, when it was closed [2,20]. In addition, high urban growth in the state's metropolitan region has resulted in intense coastal contamination, especially by metals, which are one of the main by-products of industrialization.…”

“…In addition, high urban growth in the state's metropolitan region has resulted in intense coastal contamination, especially by metals, which are one of the main by-products of industrialization. In recent decades, several initiatives have been undertaken to characterize and provide a behavioral understanding of these contaminants in Guanabara Bay [2,[20][21][22].…”