Gabriela Cugler de Pontes

Increasing inputs of nutrients and organic matter from urban areas accumulate in coastal sediments, which act as a storage compartment that can trigger eutrophication events, and promote organism mortality. The aim of this research was to evaluate the factors that determine the distribution of nutrients in sediments and porewater from a coastal environment. Jurujuba cove receives nutrients and organic matter inputs from diffuse sources (mainly domestic sewage) and from intensive mussel farming. Fifteen sediment samples were collected. pH and Eh were measured in situ. Sediments were centrifuged to extract porewater, where dissolved nutrients were analyzed. Total phosphorus and total organic carbon were analyzed in the bulk sediment by spectrophotometry and titration, respectively. Granulometry was analyzed with a laser granulometer, and carbonates were measured gravimetrically. Sediment phosphorus concentrations ranged between 0.2 and 3.2 mg g ⁻¹ and were possibly related to sewage and aquaculture, with higher concentrations at the Cachoeira River mouth and close to mussel farms. The results indicated high dissolved nitrogen (2.2 ± 4.8 mg L ⁻¹ ) and phosphorus (0.3 ± 0.3 mg L ⁻¹ ) concentrations in porewater, indicating possible diffusive release to the water column. The Q-mode cluster analysis showed the formation of two distinct groups, determined by the characteristics of the sediments. The first group incorporates samples located near the shoreline, representing an environment with higher accumulation of organic matter (average 16.6%). The other group comprised stations in the middle of the inlet, showing slightly smaller concentrations of organic matter (average 12.0%). Nonetheless, overlapping physicochemical conditions made it difficult to clearly separate the influence of urban drainage and mussel farming, indicating that multiple stressors act simultaneously in the cove. The application of isotopic relationships (nitrogen mainly) would contribute to the depiction of sources in the research area.

This study examines CH₄ and N₂O fluxes during the dry season in two distinct areas of the Pantanal: Barranco Alto Farm (BAF), dominated by grasslands, and Passo da Lontra (PL), a forested region. As climate change increases the occurrence of droughts, understanding greenhouse gas (GHG) fluxes in tropical wetlands during dry periods is crucial. Using static chambers, CH₄ and N₂O emissions were measured from soils and tree stems in both regions, with additional measurements from grass in BAF. Contrary to expectations, PL—characterized by clayey soils—had sandy mud samples that retained less water, promoting oxic conditions and methane uptake, making it a CH₄ sink. Meanwhile, BAF’s sandy, well-drained soils exhibited minimal CH₄ fluxes, with negligible methane uptake or emissions. N₂O fluxes were generally higher in BAF, particularly from tree stems, indicating significant interactions between soil type, moisture, and vegetation. These findings highlight the pivotal roles of soil texture and aeration in GHG emissions, suggesting that well-drained, sandy soils in tropical wetlands may not always enhance methane oxidation. This underscores the importance of continuous GHG monitoring in the Pantanal to refine climate change mitigation strategies.

Arsenic, cadmium, lead, and mercury in fish is the result of long-term 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 (–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.

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⁻¹. On the other hand, concentrations ten times lower than those observed in the natural system (8 ng g⁻¹) could be observed. It was concluded that the only possible source for the contamination of the sludge was the chemicals used for water treatment.