Changes in the surface water quality of a tropical watershed in the southeastern amazon due to the environmental impacts of artisanal mining.

The expansion of areas of human occupation and the increase in economic activity and deforestation are negatively impacting the Amazon ecosystem. Situated in the Carajás Mineral Province in the southeastern Amazon, the Itacaiúnas River Watershed (IRW) encompasses several active mines and has a historical record of intense deforestation primarily linked with the expansion of pasturelands, but also of urban areas, and mining activities. Industrial mining projects are subjected to strict environmental control, but artisanal mining (ASM; 'garimpos') sites have not been controlled, despite their known environmental impacts. In recent years, the opening and expansion of ASM in the IRW for the exploitation of mineral resources (Au, Mn, and Cu) have been remarkable. This study presents evidence of anthropogenic impacts, mainly caused by ASM, on the quality and hydrogeochemical characteristics of the IRW surface water. The hydrogeochemical data sets of two projects carried out in the IRW, during 2017 and from 2020 until present, were used to evaluate these impacts within the region. Water quality indices were calculated for the surface water samples. For the whole IRW, water collected during the dry season tended to yield better quality indicators in comparison to those collected during the rainy season. Two sampling sites at Sereno Creek showed very poor water quality and extremely high concentrations of Fe, Al, and potentially toxic elements over time. From 2016 to 2022, ASM sites increased markedly. Moreover, there are indications that Mn exploitation via ASM in Sereno hill is the main source of contamination in the area. New trends of ASM expansion were observed along the main watercourses, related to the exploitation of Au from alluvial deposits. Similar anthropogenic impacts are registered in other regions of the Amazon and environmental monitoring should be encouraged to assess the chemical safety of strategic areas.

Análise faciológica e estratigráfica da planície costeira de Soure (margem leste da ilha de Marajó-PA), no trecho compreendido entre o canal do Cajuúna e o estuário Paracauari / Faciological and stratigraphical analysis of Soure's coastal plain (eastern Marajó island-Pará), between Cajuúna channel and Paracauari estuary

A planície costeira de Soure, na margem leste da ilha de Marajó (Pará), é constituída por áreas de acumulação lamosa e arenosa, de baixo gradiente, sujeitas a processos gerados por marés e ondas. Suas feições morfológicas são caracterizadas por planícies de maré, estuários, canais de maré e praias-barreiras. A análise faciológica e estratigráfica de seis testemunhos a vibração, com profundidade média de 4 m, e de afloramentos de campo permitiu a caracterização dos ambientes deposicionais, sua sucessão temporal e sua correlação lateral, a elaboração de seções estratigráficas e a definição de uma coluna estratigráfica. Foram identificadas cinco associações de facies: (1) facies de planície de maré, (2) facies de manguezal, (3) facies de barra de canal de maré, (4) facies de praia e (5) facies de duna. A história sedimentar da planície costeira de Soure é representada por duas sucessões estratigráficas: (1) a sucessão progradacional, constituída pelas associações de facies de planície de maré, manguezal e barra de canal de maré; e (2) a sucessão retrogradacional, formada pelas associações de facies de praia e de duna. Essas sucessões retratam uma fase de expansão das planícies de maré e manguezais, com progradação da linha de costa (Holoceno médio a superior), e uma posterior fase de retrogradação, com migração dos ambientes de praias e dunas sobre depósitos lamosos de manguezal e planície de maré, no Holoceno atual. A história deposicional da planície costeira de Soure é condizente com o modelo de evolução holocênica das planícies costeiras do nordeste paraense.

Soures's coastal plain, eastern Marajó island (Pará), is formed by muddy and sandy deposits, low gradient areas submitted to tidal and wave processes. The morphological features are tidal flats, estuaries, tidal channels and barrier-beach ridges . The faciological and stratigraphical analysis of six vibra-core with medium deph of four meters and from outcrops allowed a caracterization of depositional environments, temporal sequence and spacial corelation, the elaboration of stratigraphical seccions and column. Were identified five facies associations: (1) tidal flat facies, (2) mangrove facies, (3) tidal channel bar facies, (4) beach facies and (5) dune facies. The sedimentary history of the Soure coastal plain is represented by two stratigraphical successions: (1) progradational succession (tidal flat, mangrove and channel bar facies association) and (2) retrogradational succession (beach and dune facies association). These successions are related to a expansion phase of tidal flats and mangroves with progradation of the coastline (Middle/Late Holocene) and a posterior retrogradation phase with landward migration of the shoreline (Late Holocene). The depositional history of the Soure coastal plain is related to the holocenic evolution model of the northeast coastal plains of Pará.