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METALS IN SEDIMENTS FROM THE SHELF-SLOPE INTERFACE OFF THE POTIGUAR BASIN OFFSHORE OIL EXPLORATION AREA, NE BRAZIL. Marine sediments collected in November 2009 and July 2011 at depths ranging from 150 m to 2,000 m in the Potiguar Basin, northeastern Brazil, were analyzed for their main sedimentological characteristics (contents of carbon, nitrogen and their stable isotopes) and metals (Al, Fe, Mn, As, Cr, Cu, Ni, Pb, V and Zn) concentrations and their spatial distribution. Sediments were relatively rich in organic matter (C-org: 0.21% to 0.56%) and metals concentrations increased with depth, suggesting an accumulation of fine and terrigenous sediments eroded and transported from the continental shelf to the slope region. Metals concentrations were higher than those observed in coarser shelf sediments, because of sorting of fine-grained sediments. Iron (Fe), Cr and Cu distribution, although presenting this general pattern, also suggests some changes along the transport. Fe and Cr, probably in discrete minerals, are less affected by accumulation in deeper sediments. The high enrichment in Cu, however, suggests additional sources directly to slope sediments, probably by biological productivity and deposition through the water column. The concentrations of all metals are lower or fall close to the lowest range of concentrations reported for slope sediments from other marine regions worldwide and no evidence of anthropogenic contribution was evident.

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SOURCE OR SINK? A REVIEW OF THE CO2 FLUXES AT THE BRAZILIAN CONTINENTAL SHELF. Studies of global carbon balance estimates are still incipient in the oceans of the Southern Hemisphere, mainly in coastal areas and continental shelf. Even in Brazil, despite its continental proportion coastline, there is still a great inconsistency in studies on the marine carbonate system and CO2 fluxes at the air-sea interface. This article presents a review of studies on CO2 fluxes on the coast of Brazil, published between the years 2000 and 2022, aiming to map the distribution of CO2 fluxes on the Brazilian continental shelf, to understand its role as a source or sink of CO2. In general, large-scale studies show that the Brazilian shelf exhibits a latitudinal variation of air-sea CO2 fluxes, behaving mainly as a source in the north, where there is no influence of the Amazon River plume, and as a sink in the south portion. We also identified there is a strong influence on the occurrence of mesoscale and synoptic oceanographic and meteorological events, and the presence of different ecosystems, which can change the behavior of CO2 fluxes locally. However, there are still many data gaps along the continental shelf, as well as in different seasons for the entire coast.

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The present work aimed at evaluating indicators of hydrocarbon sources to sediments from the Solimões River region, in the central Amazon. The 16PAH, the alkylated homologs and molecular markers were investigated. The entire series of alkylated PAH were present and, in some cases, with a distribution observed when oil residues dominate. Nevertheless, hopanes characterizing immature environments undergoing diagenetic transformation were identified in samples from the Solimões River and in surface as well as in core sediment samples from Preto Lake, in the Coari-Manaus stretch. Investigation suggests early diagenesis of the organic matter confirmed by identifying biogenic markers produced during organic matter transformation. Some of these markers derive from incomplete combustion of biomass and are contained in particulate matter formed during forest burning. In the sediments of an industrial area near the city of Manaus, the entire series of mature hopanes was present indicating anthropogenic source of hydrocarbons. The results so far obtained point out the complexity of PAH source appraisal.

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EVALUATING DIRECT AND INDIRECT pCO2 MEASUREMENTS IN ESTUARINE ENVIRONMENTS. Estuaries are dynamic systems globally characterized as sources of CO2 to the atmosphere. However, they present large spatial-temporal variability in both pCO2 and FCO2. Increased CO2 emissions turns imperative to obtain continuous and accurate measurements of pCO2 in air and water to monitor FCO2 in these sensitive and complex environments. Currently, direct measurements of pCO2 and estimates of FCO2 in estuarine regions are still scarce and frequently the indirect pCO2 estimates are used that consists of measurements from at least two other parameters of the carbonate system: total alkalinity, dissolved inorganic carbon or pH. In this work, we evaluated recent direct and indirect measurements of pCO2 in the Jaguaribe River estuary-CE. This study provides a critical analysis of the data obtained through the two main methods mostly used to estimate pCO2, presenting the challenges towards greater consistency in obtaining data for a better understanding of the carbonate system in estuarine waters. We highlight the potential for continuous pCO2 measurements and long-term monitoring in coastal environments, contributing to improve knowledge of regional CO2 exchanges and to elucidate the role of estuaries in the global carbon cycle.

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THE ESTUARINE ENVIRONMENT AND pH VARIATION: NATURAL LIMTS AND EXPERIMENTAL OBSERVATION OF THE ACIDIFICATION EFFECT ON PHOSPHORUS BIOAVAILABILITY. This study shows the variation of pH in the Cananéia-Iguape Estuarine-Lagoon Complex (CIELC). Data from 3 years (2019, 2021, 2022) were obtained in 17 points presenting the following ranges: temperature (14.88-27.05 ºC), pH (7.16-8.40) and DIP (0.20-11.28 µmol L-1) along a saline gradient (0.05-32.09) under different hydrodynamics, biogeochemical processes and anthropogenic influence. The pH buffering capacity due to the presence of weak acid salts in saline water (S ≥ 30) was associated to the lowest DIP, decreasing with low salinity values, confirming the direct correlation among salinity and pH. The highest temperatures in the winter of 2021, corroborated with the abnormal climate event in that year. An in vitro experiment showed results of the interaction of PID and sediments with different textures, with and without the presence of the benthic microbiota under a considerable decreasing of the pH (acidification) in relation to the natural condition of this environment. The P sediment flux characterized Iguape sector as a P sink with or without biota, Ararapira sector as a P source with biota and Cananéia, as P source without biota. The salt water buffered the pH and sediment buffered DIP both associated to the biogeochemical and hydrodynamic processes contribute to the homeostasis in the system.

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ORGANIC MATTER SOURCES TO THE SUPERFICIAL SEDIMENT OF THE ITAPICURU RIVER ESTUARY (BAHIA - BRAZIL). The present study evaluated the sources of organic matter (O.M.) in the Itapicuru River estuary (IRE), which is in an environmentally protected area surrounded by the Atlantic Rainforest in the northeast of Brazil. Eleven sediment samples were collected along the study area. Total organic carbon (TOC) and the δ13C values were determined using an elemental analyzer coupled with an isotope ratio mass spectrometer. The n-alkanes composition was evaluated through gas chromatography coupled to a flame ionization detector. TOC and total n-alkanes concentrations ranged, respectively, from not detected to 0.72%, and from lower the limit of detection to 5024 ng g-1. There was a significant concentration of n-C22 and n-C24 in some samples showing bacterial production and recycling of O.M. Values of δ13C ranged from -27.6 to -21.9‰. Carbon preference index, terrestrial-aquatic ratio, aquatic production index, average chain length, and the ratio between n-C29 and n-C31 values ranged, respectively, from 1.42 to 4.11; 2.82 to 9.40; 0.00 to 0.25; 27.7 to 29.9; and 0.27 to 0.43. These results show that concentrations of O.M. to IRE are low, and its main source is C3 plants, such as those from mangroves. There is also the contribution of macrophytes.

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Multiple environmental problems are caused by the accumulation of nitrogen (N) and phosphorus (P) in river water on its way to the ocean. The objective of this work was to determine the N and P loads in 12 hydrographic basins that flow into estuaries along the northeastern coast of Brazil using established methods. Additionally, natural and anthropogenic loads trends in the hydrographic basins of 12 tropical rivers in northeastern Brazil over 27 years (1990-2016) were evaluated. The results indicated an annual average increase of +1.1% in population density, while precipitation showed no significant trend. The anthropogenic loads were 21 and 112 times higher than natural inputs for N and P, respectively. Anthropogenic sources accounted for ~ 96% of all contributions. The positive trends of these loads (mainly wastewater) represented an annual average increase of 1.1% for N and 1.2% for P, for all river basins included in this study. These percentages represent average annual loads of 251 t N yr-1 and 54.8 t P yr-1. The time series of N and P in the study region showed trends that point to a constant increase, implying a greater contribution of these loads to the adjacent coastal region year after year.

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PERFLUORINATED COMPOUNDS: A THREAT TO THE CLEAN OCEAN. Per- and polyfluorinated compounds (PFAS) have been produced for more than seven decades and widely used in the most diverse areas, from food packaging, textile industry, aqueous film-forming foam to pesticides and surfactants. However, the characteristics that allow the wide range of applications also bring environmental concerns due to their persistence and toxic effects. Although the ocean might be the final destination of PFAS, in Brazil few studies have been carried out about PFAS and there are many gaps regarding their environmental occurrence, sources and distribution. Therefore, this article presents a review of the production, use, behavior in the environment, legislation, the occurrence of classic PFAS in the Brazilian marine environment, as well as perceptions about their fluorinated substitutes.

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ORGANIC AND INORGANIC BIOMARKERS OF ATMOSPHERIC AEROSOLS FROM MARINE REGIONS. In this study, we overview the recent advancements in knowledge regarding organic and inorganic biomarkers of atmospheric aerosols from coastal zones and open marine areas. It deals with the interaction between the ocean and the atmosphere through their interface, the formation of a seawater microlayer (SML) and the exchange of a myriad of chemical compounds between those environmental compartments. We also discuss how marine aerosols (MAs) are intrinsically related to the global carbon cycle, influence the radiative budget of the Earth, and are related to global climate. At the end, we discuss the trends of new studies on the topic.

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Plastic pollution is causing worldwide concern, especially after evidence that the various types of plastic degrade into particles of smaller sizes; known as micro- and nanoplastics. The origin of the plastics in the environment is related to human actions. The objective of this review is to describe the main routes of microplastic input in the Amazonian rivers and how local environmental characteristics can affect the transformation of plastics into microplastics until their absorption by aquatic organisms. The current situation regarding the presence of microplastic particles in freshwater is analyzed considering the environmental dynamics of the region, and focuses on rivers, estuaries and sediments, their effects on organisms, especially on fish, followed by the transportation of microplastic particles to the sea. Amapá, Amazonas, Pará and Mato-Grosso are the states of the Brazilian Amazon with scientific reports on the characterization of microplastic particles in sediment, water, and fish. These studies are local and descriptive and most of them highlight the characterization of microplastics. There is a need for field research in the various microregions of the Amazon, as well as actions to mitigate the damage, including to riverine populations, that is caused by these pollutants in the region.

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UNCONVENTIONAL POLYAROMATICS COMPOUNDS AND MERCURY IN THE TODOS OS SANTOS BAY, BRAZIL: RECENT ADVANCES AND CONTRIBUTIONS TO BETTER UNDERSTAND OF THEIR ROLE IN THE MARINE ENVIRONMENT. Baía de Todos os Santos (BTS) is the second-largest Brazilian bay; it was the first oil producing region in Brazil, with three large industrial parks in its north-northeast portion. In addition, the BTS has two large ports and a population of around 3 million inhabitants distributed among 14 cities. In the present study, recent studies on contamination by polycyclic aromatic compounds (PACs) and Hg in sediments, water, and biota from the BTS region are presented and critically discussed. Among the PACs, studies evaluating the presence of polycyclic aromatic hydrocarbons (PAHs) and their nitrated (nitro-PAHs), oxygenated derivatives (oxy-PAHs), and those containing atoms of S as a heteroatom (PASHs) are considered, as well as the element Hg distributed in seawater, sediments, and biota. Regarding biomonitoring organisms, recent results on polychaetes, ascidians, and corals are presented. Trends for future studies are presented at the end of the text.