Arsenic, cadmium, lead, and mercury in fish is the result of longterm biomagnification in the food chain and is of public concern, due to the toxicity they engender. The objective of this research was to determine the concentrations of arsenic, cadmium, lead, and mercury in 13 species of marine fish broadly commercialized in Aracaju, SE, Brazil and to evaluate the risks of fish consumption associated with these trace elements, using the Target Hazard Quotient (THQ). As, Cd, and Pb levels were measured with inductively coupled plasma mass spectrometry (ICP-MS), and mercury was analyzed via cold vapor atomic absorption spectrometry. The results indicate a large variability in concentrations for arsenic (0.07-2.03 mg kg -1 ) and mercury (0.01-1.44 mg kg -1 ), associated with the animal dietary category. Cadmium (0.04-0.19 mg kg -1 ) and lead (<0.01-0.45 mg kg -1 ), on the other hand showed a mild variability. None of the evaluated specimens had As, Cd, and Pb THQ values higher than 1. The THQ values for mercury were higher but indicated no consumption risk, except for amberjack, and snook fish. Overall THQ indicates lower risk of consumption in fish that are at the base of the food chain, than in those that are top predators.

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Although sludge piles from drinking water treatment plants can contain harmful substances, in many countries, their disposal methods are still unregulated. Besides aluminum, which is a major constituent in these residues, many other contaminants-like trace metals-can be present and may result from the quality of the raw materials used for water treatment. The application of these chemicals for the treatment of drinking water can generate toxic sludge and contaminate the produced water. In the present work, mercury contamination in the sludge piles of two drinking water treatment plants located along the margins of the Juturnaíba Reservoir, Southeast Brazil, was evaluated to verify whether contaminants are incorporated during water treatment. In the summer 2012, five cores were collected from the piles, and were analyzed for Eh, granulometry, total carbon, total nitrogen, and total mercury. The results indicated an anoxic environment, reflecting composition of the suspended matter. Carbon and nitrogen presented elevated concentrations, but also seemed to reproduce the characteristics of the suspended matter in the raw water. The concentrations of mercury were extremely variable but presented unexpectedly high values in some of the layers, reaching 18,484 ng g. On the other hand, concentrations ten times lower than those observed in the natural system (8 ng g) could be observed. It was concluded that the only possible source for the contamination of the sludge was the chemicals used for water treatment.

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.

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 (r2 = 0.66) and %MeHg in relation to THg (r2 = 0.75) were observed only for RJH sediments. These findings 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.

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