Abstract
This study presents data on the detailed evaluation (tier 2) of a site-specific ecological risk assessment (ssERA) in a former smelter area contaminated with metals (Santo Amaro, Bahia, Brazil). Combining information from three lines of evidence (LoE), chemical (ChemLoE), ecotoxicological (EcotoxLoE) and ecological (EcoLoE), in the Triad approach, integrated risk values were calculated to rank sites and confirm the potential risk disclosed with tier 1. Risk values were calculated for the habitat and for the retention functions in each sampling point. Habitat function included the ChemLoE calculated from total metal concentrations. The EcotoxLoE was based on reproduction tests with terrestrial invertebrates (Folsomia candida, Enchytraeus crypticus, Eisenia andrei), shoot length and plant biomass (Avena sativa, Brassica rapa). For the EcoLoE, ecological parameters (microbial parameters, soil invertebrate community, litter breakdown) were used to derive risk values. Retention function included the ChemLoE, calculated from extractable metal concentrations, and the EcotoxLoE based on eluate tests with aquatic organisms (Daphnia magna reproduction and Pseudokirchneriella subcapitata growth). Results related to the habitat function indicated that the metal residues are sufficient to cause risk to biota, while the low metal levels in extracts and the general lack of toxicity in aquatic tests indicated a high soil retention capacity in most sampling points. Integrated risk of tier 2 showed the same trend of tier 1, suggesting the need to proceed with remediation actions. The high risk levels were related to direct toxicity to organisms and indirect effects, such as failure in the establishment of vegetation and the consequent loss of habitat quality for microorganisms and soil fauna. This study shed some light on the selection of tools for the tier 2 of an ssERA in tropical metal-contaminated sites, focusing on ecological receptors at risk and using available chemical methods, ecological surveys and ecotoxicity tests.
Highlights
Ecological risk assessment (ERA) is a process of collecting, organizing and analyzing environmental exposure and effect data to estimate the risk of contamination to ecosystems, being a useful tool, for managing contaminated areas [1]
Soils from the study sites showed high clay percentage low (
The present results suggest that the retention function of soils at most sampling points prevented the mobilization of metals via the water pathway, especially to groundwater, a finding in agreement with the results of the ChemLoE reporting low amounts of extractable metals
Summary
Ecological risk assessment (ERA) is a process of collecting, organizing and analyzing environmental exposure and effect data to estimate the risk of contamination to ecosystems, being a useful tool, for managing contaminated areas [1]. A site-specific ERA (ssERA) integrating contaminant exposure and biological effects, either through toxicity tests or in situ surveys, may reveal potential adverse effects of specific (point or diffuse) pollution problems [2]. For the process of risk characterization the Triad approach, which consists of integrating three lines of evidence (LoE), chemical (ChemLoE), ecotoxicological (EcotoxLoE) and ecological (EcoLoE) [5], has been highly recommended and successfully applied in ssERA of contaminated soils [1, 6, 7]. The Triad approach is usually applied within a tiered system, i.e., information from each LoE is collected at each tier following a step-wise cost-effective process [1]. The tools used in tier 2 to collect information of each LoE should indicate long-term direct or indirect effects of contamination, while being more ecologically relevant and of a high capacity to differentiate levels of contamination [8]
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