The municipality of São Caetano de Odivelas/PA, is located on the Atlantic Coast of Northeastern Pará, and is composed of two coastal ecosystems: mangroves and sandbanks. Its average annual temperature is 27.7° C and its relative air humidity presents annual averages around 80%. The mangroves, with the genera Avícennía, Rhizophora and Laguncularia, dominate the landscape in the study area occupying muddy banks, mainly at the mouth of the Mojuim River and contiguous areas, presenting an alternating behavior between net importer and exporter of suspended materials and heavy metals. This work aims to determine the heavy metal contents (Ni, Pb and Zn) and relate them to pH and EH variables of mangrove soils. Three soil collection sites were chosen along the mouth of the Mojuim River (Mojuim Bay), whose mud auger samplings were performed up to three meters deep, always at three points in the last of three contiguous plots PI, P2 and P3. In the field analyses to determine pH in H20 and EH in H20 a pH meter calibrated in distilled H20 was used, obtaining on average a pH ranging from 4 to 7, while for EH an inversely proportional relationship was found. The morphological analysis of the samples, based on EMBRAPA (1997) and MUNSELL (1994), showed soil without a developed structure with A and Cg horizons and a predominance of the clay fraction, varying in the following order: clays>silt>fine sand. The Ni, Pb and Zn contents obtained will be related to other studies carried out in mangroves of the North Coast of Brazil.
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