Abstract Understanding the variability in synthetic aperture radar (SAR) backscatter as a function of the phenological variability of vegetation and tropical environmental conditions is still a challenge. Through quantitative and qualitative analyses, this study addresses how both environmental and precipitation conditions, tidal range, and vegetation density affect the backscatter coefficients of coastal environments based on the analysis of four C-band, HH-Polarization, RADARSAT-1 Wide 1 images, in descending orbit, acquired in the wet and dry seasons. The canopy structural variations were analyzed using the enhanced vegetation index (EVI), and correlated with the backscatter values of SAR images, in order to define the predominant backscatter mechanisms, making it possible to distinguish the mangroves from the brackish marshes in the easternmost Amazon coastal plain (Caranguejos Island). The C-band, HH-Polarization RADARSAT-1 backscatter shows the highest correlation with average EVI values in the dry season. The results show that mangroves and brackish marshes can be distinguished in images acquired under low precipitation, especially in the dry season. Variations in the tidal conditions have no effect on the backscatter values of RADARSAT-1 images. We conclude, therefore, that multitemporal RADARSAT-1 images are adequate for monitoring and discriminating wetland environments in a humid tropical climate.

Abstract We present this manuscript as a methodological approach and general guidelines for geochemical mapping and background/baseline projects for environmental assessment in tropical areas. A case study was carried out in the Itacaiúnas River watershed (IRW), Eastern Amazon, to fill in a gap in knowledge on the distribution of chemical elements, particularly those potentially toxic, in the near-surface environment of the area. The high-impact results of this research project revealed the need for similar scientific investigation across the globe with the implementation of a systematic methodology. The study shows, for example, the importance of well-planned field activities, multi-medium sampling, analytical methods, laboratory procedures, database construction, and general aspects of data processing and statistical treatment. The importance of this contribution is that it can be used as a reference in support of geospatial analysis in research within the scope of geochemical mapping and background-baseline projects. The database is accessible through a web-based geographic information system front-end; a Geochemical Atlas of the IRW will be available as soon as possible.

RESUMO Compreender a dinâmica hidrossedimentológica dos rios tropicais é um desafio, principalmente na Amazônia, devido às suas áreas remotas e de difícil acesso. Este estudo foi baseado em dados coletados em 16 seções hidrossedimentológicas de controle distribuídas nas 6 sub-bacias que compõem a bacia hidrográfica do Rio Itacaiúnas (BHRI), com 4 campanhas anuais (enchente, cheia, vazante e seca) entre 2015 e 2019, objetivando a construção e comparação da curva-chave de sedimentos e produção de sedimentos. Os dados na foz da bacia revelaram que o período chuvoso é responsável por 93% das descargas líquidas com médias de 1460,88 m3/s e por 98% das descargas de sedimentos em suspensão com média de 5864,15 ton/dia. As Concentrações de sedimentos em suspensão (CSSs) são baixas a moderadas (50 a 150 mg/l). As análises das curvas obtidas com todos os dados apresentaram R2 (0,92 a 0,99) maiores do que utilizando apenas os valores da estação chuvosa ou seca, mostrando um bom ajuste da equação de potência aos dados QSS e Q para todas as seções estudadas. Os maiores valores do coeficiente a e b indicam áreas de maior produção de sedimentos e desmatamento e áreas com novas fontes de sedimentos e floresta preservada.

ABSTRACT Understanding the hydrosedimentological dynamics of tropical rivers is a challenge in the Amazon due to its remote and difficult-to-access areas. This study was based on data collected from 16 hydrosedimentological control sections in the 6 subbasins that make up the Itacaiúnas River Watershed (IRW), with 4 annual campaigns (high water levels, rising water levels, falling water levels, low water levels) between 2015 and 2019, with the aim of constructing and comparing sediment rating curves and sediment yield. The data at the mouth of the IRW revealed that the rainy season is responsible for 93% of liquid discharges (Q) with an average of 1460.88 m3/s and for 98% of suspended sediment discharges (SSQ) with an average of 5864.15 tons/day. Suspended sediment concentrations (SSCs) are low to moderate (50 to 150 mg/l). The curves encompassing all the data showed R2 values (0.92 to 0.99) greater than the curves with only the values of the rainy or dry season, indicating a good fit of the power equation to the SSQ and Q data for all sections studied. Higher values of coefficients a and b show areas of greater sediment production and deforestation, as well as areas with new sources of sediment and preserved forest.

ABSTRACT: Phosphorus (P) fixation in the soil reduces the utilization of this element by plants and can be one of the main problems for fertilization management in soils containing Fe oxides. As a strategy to minimize the effects of P retention, organic materials, such as biochar or commercial composts, may be useful tools to maintain P availability and delay immobilization of this element in the soil, thereby benefiting, for example, the rehabilitation of areas impacted by Fe mining. The objective of this study was to evaluate the kinetics of P sorption and desorption and the hysteresis index in red mining waste from Fe mining subjected to açaí biochar and commercial compost amendments. Therefore, a substrate collected from Fe mining waste piles in the Carajás Mineral Province was incubated for 30 days with açaí biochar, commercial compost, and açaí biochar + commercial compost at a ratio of 90 % mining waste and 10 % organic amendment (w/w). The P sorption and desorption kinetics were evaluated in a solution containing 10 mg L−1 P at times from 0.5 to 48 h; the data were modeled according to a pseudo-first-order equation considering two types of reaction sites, and the hysteresis index was obtained by the difference between the sorption and desorption isotherms. Treatment of the mining substrate with açaí biochar reduced P sorption, while P desorption was increased by up to 60 % by applying biochar and/or commercial compost. Açaí biochar also reduced the hysteresis of P sorption from 78 to 54.8 %, in addition to slowing P fixation in this substrate. Thus, this study showed that açaí biochar and commercial compost may maximize the benefits of phosphate fertilization during the rehabilitation of areas impacted by Fe mining. However, as these composts can cause different effects on P dynamics in mining waste, their effects on other elements, such as micronutrients, whose availability may be affected, are important to be evaluated.

A fusão de imagens multisensor tem sido um procedimento amplamente utilizado em função da natureza complementar dos vários conjuntos de dados. Este artigo compara o desempenho de quatro métodos diferentes para fusão de imagens Landsat-7 ETM+ e RADARSAT-1 W1. A comparação foi baseada nas características espectrais das imagens, utilizando-se de análise estatística e visual dos produtos gerados. Quatro métodos foram usados para a fusão das imagens Landsat-7 ETM+ e RADARSAT-1 W1: i) fusão do SAR (radar de abertura sintética) com a tríade selecionada pelo OIF (Optimum Index Factor ); ii) realce por decorrelação da tríade selecionada pelo OIF, seguida da fusão com SAR; iii) ACP (Análise por Componentes Principais) para as seis bandas ETM+ do espectro refletido (1, 2, 3, 4, 5 e 7) e posterior fusão das três primeiras componentes principais (1CP; 2CP; 3CP) com o SAR; iv) SPC-SAR (Principal Componente Seletivo - SAR). O produto SPC-SAR mostrou melhor desempenho na identificação das feições costeiras e permitiu o realce mais efetivo dos diferentes ambientes.

Multisensor data fusion has been widely used in response to complementary nature of many data sets. This paper compares the results of four different data fusion methods used to merge Landsat-7 ETM+ and RADARSAT-1 Wide 1 data. The comparison was based on spectral characteristics of images using statistical and visual analyses of generated products. Four methods were used in the Landsat-7 ETM+ and RADARSAT-1 W1 data fusion: i) The best three bands combination(Landsat-7) based OIF (Optimum Index Factor) selection were merged with RADARSAT-1 data; ii) Decorrelation stretch was applied in the three bands (Landsat-7) selected by OIF and merged with RADARSAT-1 image; iii) PCA (Principal Component Analysis) to six reflective ETM+ bands (1, 2, 3, 4, 5 and 7) and posterior fusion of the three first Principal Components (PC1, PC2, PC3) with SAR; iv) A new approach SPC-SAR (Selective Principal Component - Synthetic Aperture Radar). The SPC-SAR product presented the best performance in the identification of coastal features and allowed the most effective enhancement of the different environments.

Este trabalho apresenta os resultados do reconhecimento e mapeamento dos ambientes costeiros da região do Golfão Maranhense, Brasil, utilizando uma abordagem metodológica que incluiu: (a) análise integrada com base no processamento digital de imagens, ópticas Landsat-4 TM e SPOT-2 HRV, de imagens SAR (Synthetic Aperture Radar) do RADARSAT-1, e dados de elevação da SRTM (Shuttle Radar Topography Mission); (b) sistema de informações geográficas; e (c) levantamentos de campo relativos à geomorfologia, topografia e sedimentologia. Os ambientes costeiros, assim mapeados foram agrupados em quatro setores: Setor 1, com pântanos salinos, pântanos de água doce, lagos intermitentes e canal estuarino; Setor 2, abrangendo tabuleiro costeiro, planície de maré lamosa, planície fluvial, planície de maré arenosa, praias de macromaré, área construída e lagos artificiais; Setor 3, com manguezal, paleodunas e planície de maré mista; e Setor 4, constituído por dunas móveis. Além disso, foram também reconhecidos lagos perenes, deltas de maré vazante e planícies de supramaré arenosas. O processamento digital e a análise visual das imagens de sensores remotos orbitais, associados ao uso de sistemas de informações geográficas, mostraram-se eficazes no mapeamento de zonas costeiras tropicais, possibilitando a geração de produtos com boa acurácia e precisão cartográfica.

This paper presents the results of coastal environmental mapping of Golfão Maranhense, Brazil, using a methodological approach that includes: (a) integrated analysis based on digital image processing of Landsat-4 TM, SPOT-2 HRV, RADARSAT-1 SAR (Synthetic Aperture Radar) and SRTM (Shuttle Radar Topography Mission) data; (b) geographic information system; (c) field surveys related to geomorphology, topography and sedimentology. Mapped environments were grouped into four sectors: Sector 1, with salt marsh, fresh marsh, estuarine channel and intermittent lake; Sector 2, embracing coastal plateau, fluvial floodplain, sandflats, macrotidal beach, urban areas, artificial lakes and mudflats; Sector 3, including, paleodunes covered with grass, mangroves and mixed intertidal banks; Sector 4, constituted by mobile dunes. In addition, perennial lakes, ebb-tidal deltas and supratidal sandflats were recognized. Digital image processing visual analysis of orbital remote sensing data in association with geographic information system, proved to be effective in tropical coastal mapping, allowing the generation of products with good accuracy and cartographic precision.

Acidentes relacionados ao transporte de petróleo constituem uma ameaça às zonas costeiras de todo o mundo, pois se trata de um evento ecologicamente desastroso podendo causar sérios danos ao meio ambiente. Na costa nordeste do Pará ocorre intenso fluxo de navios e balsas transportando petróleo e derivados, daí a necessidade de estabelecer estratégias de prevenção e gestão dos impactos ambientais ao derrame de óleo para elaboração de planos de emergência. O objetivo deste trabalho é gerar o mapa dos ambientes costeiros e o mapa de índice de sensibilidade ambiental ao derrame de óleo dos ambientes costeiros de uma porção da costa nordeste do Pará. A metodologia consistiu no processamento digital de imagens Landsat ETM+7, associadas aos dados do MDE do SRTM (shuttle radar topography mission) e aos dados de campo, em ambiente de SIG (sistema de informação geográfica). Os resultados permitiram o reconhecimento e a descrição de cinco unidades geomorfológicas e de ambientes sedimentares; identificação e hierarquização de nove índices de sensibilidade ambiental (ISA); além da geração do mapa de índice de sensibilidade ambiental ao derramamento de óleo. As técnicas de sensoriamento remoto e SIG mostraram ser importantes ferramentas no reconhecimento dos ambientes costeiros e geração dos mapas propostos.

Accidents related to exploration and oil transport are a threat to coast zones around the world. Oil spills are an ecological disaster that may cause irreparable damage to the environment. In the northeast cost of Pará state the intense flow of ships and rafts transporting petroleum and flowed, then the need to establish prevention strategies and administration of the environmental sensitivity about the oil spills in a certain part of Pará state northeast cost. The methodology consisted on processing digital images from remote sensors in the Landsat ETM+7 associated to data from the SRTM (shuttle radar topography mission) digital model of elevation, and to the field data collected in a GIS (geographical information system) environment. The most important results allowed: recognizing and describing five main geomorphological; identifying and classifying nine units of Environmental Sensitivity Rates (ISA) and creation of the Environmental Sensitivity Rates map to oil spill. The remote sensors techniques and SIG proved to be important tools for recognizing coast environments and for generating proposed maps.

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.

De acordo com o Atlas de Manguezais, este ecossistema representa 8% de toda a linha de costa do planeta e um quarto da linha de costa da zona tropical, perfazendo um total de 181.077 km². Este trabalho objetiva quantificar a extensão dos manguezais de macromaré da costa nordeste do Pará e noroeste do Maranhão, aqui denominada de Costa de Manguezais de Macromaré da Amazônia (CMMA). O reconhecimento das áreas de manguezais e sua quantificação foram realizados a partir da utilização de imagens Landsat-7 ETM+, adquiridas em 1999 e 2000 e de um sistema de informações geográficas (SIG). A integração dos dados de sensores remotos, dados geológicos e oceanográficos permitiu o reconhecimento de cinco setores geomorfológicos, que abrangem uma superfície total de 7.591 km² de manguezais. Esta área representa a maior faixa de manguezais contínuos do planeta e corresponde a 56,6% dos manguezais do Brasil. Medidas prioritárias de conservação dos manguezais da Amazônia devem ser tomadas e pesquisas que busquem a melhor compreensão deste complexo e importante ecossistema devem ser financiadas e desenvolvidas.

According to the World Mangrove Atlas, this ecosystem represents 8% of the world's coastline and one quarter of the tropical coastal zone shoreline, embracing 181,077 km². The aim of this work is to map and to quantify the extension of macrotidal mangroves along the northeastern Pará and northwestern Maranhão coasts, here named as Amazon Macrotidal Mangrove Coast (AMMC). The identification of mangrove areas and their quantification were carried out using Landsat-7 ETM+ images acquired in 1999 and 2000 and a geographic information system (GIS). The integration of remote sensing data, geological and oceanographic data allowed the recognition of five geomorphologic sectors, representing a total mangroves area of 7.591 km². This area represents the largest continuous mangrove belt in the world and constitutes 56,6% of mangroves in Brazil. Prioritary measures for Amazon mangrove conservation must be taken and research to enhance understanding of this complex and important ecosystem must be supported and developed.