The aim of this study was to evaluate the distribution of DDT and metabolites in surface soils and soil profiles from two areas containing deposits of obsolete pesticides in Belém, Amazon Region, Brazil. DDT and metabolites were extracted by microwave assisted extraction and analyzed by gas chromatography with electron capture detection. Concentrations of total DDT in surface soil samples ranged from 64.22 mg kg in area 1 (A1) to 447.84 mg kg in area 2 (A2). Lower levels were found in soil profiles than at the surface (6.21-21.17 mg kg in A1 and 36.13-113.66 mg kg in A2). pp'-DDT, pp'-DDE and pp'-DDD were detected in sediments at levels of 2.01, 0.96 and 0.35 mg kg, respectively. The ratio (DDE + DDD)/ΣDDT was low indicating the recent introduction of DDT to the environment in the two study areas, through the volatilization and atmospheric deposition of the obsolete pesticides.

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Marine phycotoxins are organic compounds synthesized by some species of microalgae, which accumulate in the tissues of filter-feeder organisms such as bivalve mollusks. These toxins can cause acute intoxication episodes in humans, a severe threat to aquaculture and fisheries. In the State of Pará, Brazil, oyster farming has community, artisanal and sustainable bases, using mangroves as cultivation environment and seed banks. In small-scale production, there are often no established methods of safeguarding the health of consumers elevating the potential risks of shellfish poisoning outbreaks. Our study evaluated the presence of phycotoxins in oysters cultivated in five municipalities in the region of the Atlantic Amazon (Pará, Brazil) assessing the quality of the final product. We further evaluated the microalgae, water quality, and the spatio-temporal variation of physicochemical factors in the same area. Diatoms dominated the microalgae composition, followed by dinoflagellates, some of which are reported to be potentially toxic and producers of paralytic shellfish toxins. For the first time, we describe the occurrence of the potentially toxic dinoflagellate Ostreopsis sp. in the Amazon region. Furthermore, for the first time, toxins were detected in oyster farming in the northeast of the State of Pará, namely GTX2,3, STX, and dc-STX nevertheless, with nontoxic values. The identified toxins represent a potential threat to shellfish consumers.