Bioavailability assessment of toxic metals using the technique “acid-volatile sulfide (AVS)-simultaneously extracted metals (SEM)” in marine sediments collected in Todos os Santos Bay, Brazil

Abstract

This paper reports the bioavailability of the metals (cadmium, copper, zinc, lead, and nickel) in sediment samples collected in seven stations from the São Paulo Estuary, Todos os Santos Bay, Brazil. The bioavailability was determined by employing the technique "acid-volatile sulfide (AVS) and simultaneously extracted metal (SEM)". The elements cadmium, copper, lead, and zinc were determined using differential pulse anodic stripping voltammetry (DPASV), while nickel was quantified utilizing electrothermal atomic absorption spectrometry (ET AAS). The accuracy of these methods was confirmed using a certified reference material of estuarine sediment (NIST 1646). The sulfide was quantified using potentiometry with selective electrode and the organic matter determination employing an indirect volumetric method using potassium dichromate and iron(II) sulfate solutions. The bioavailability of the metals was estimated by relationship between the concentration of AVS and the sum of the concentrations of the simultaneously extracted metals (ΣSEM), considering a significant toxicity when (ΣSEM)/(AVS) is higher than 1. The bioavailability values in the seven stations studied varied from 0.93 to 1.31 (June, 2014) and from 0.34 to 0.58 (September, 2014). These results demonstrated a critical condition of toxicity (bioavailability >1) in six of the seven sediment samples collected during the rainy season (June, 2014). In the other period (September, 2014), the bioavailability was always lower than 1 for all sediment samples collected in the seven stations. The individual values of the concentrations of the five metals were compared with the parameters PEL (probable effects level) and TEL (threshold effects level), which are commonly employed for characterization of ecological risk in environmental systems. This comparison revealed that all metals have concentrations lower than the PEL and only zinc and lead in some stations have contents higher than the TEL. The bioavailability evaluation and the concentrations achieved for the five elements in the sediments samples analyzed demonstrated that the ecosystem studied does not present an environmental risk.

Impact of Seasonality on Copper Bioavailaility to Crabs (Ucides cordatus, Linnaeus, 1763) in Mangrove Soils of Todos os Santos Bay (Bahia, North Eastern Brazil)

“…Previous studies have shown high concentrations of pollutants in this area, including hydrocarbons (Queiroz and Celino, 2008a, b;Silva et al, 2014) and trace elements, mostly copper (Hatje and Barros, 2012;Andrade et al, 2017). Despite pollution having been reported in the BTS (Milazzo et al, 2014;Rocha et al, 2016;Andrade et al, 2017), most of the studies carried out focused on total levels in soil and sediments, with works on bioavailability based mainly on the quantification of acid-volatile sulphides and metals extracted simultaneously (AVS-Me; Silva-Júnior et al, 2016;Brito et al, 2020). This technique has limitations with regard to the quantification of sulfides, with underestimation of concentrations in the system as well as of metallic bioavailability (Cooper and Morse, 1998;Luther, 2005), since it disregards other associations established between metals and other geochemical phases of soils/sediments (Huerta-Días and Morse, 1992;Otero and Macías, 2003).…”

A Comparison of Sediment Metal Concentrations as Potential Stressors to Resident Benthic Communities in an Agricultural Waterbody

“…Heavy metals have been increasing in the global environment since the industrial evolution [1]. Metals in aquatic natural systems are of concern to regulators because they can be toxic at concentrations above ambient conditions, non-biodegradable in the environment, and accumulate in animal and plant tissue [2]. Many metals are essential for living organisms, yet can be toxic at high concentrations [3].…”

“…In aquatic ecosystems, sediments are the main sink for metals [4]. Sources for metals in the environment are both anthropogenic and natural and include effluents from wastewater treatment plants, industrial and agricultural wastes, power stations, mining, boating activities, transportation vehicles, urban runoff, and geological processes [2,5,6].…”

Historical Review of Simultaneously Extracted Metal Copper Sediment Concentrations in Agricultural and Non-Agricultural Areas

“…However, there is one study where a brief review of SEM copper data based on just agricultural use has been conducted [9]. Anthropogenic sources for SEM copper in the aquatic environment include wastewater treatment plants, various industrial wastes, stormwater runoff, mining activities, antifouling boat paints, and agricultural use [10][11][12]. For example, copper-based compounds are used as fungicides to protect crops from important diseases in many areas of the world.…”