Maria de Lourdes Souza Santos

Influence of the Amazon and Para Rivers on Water Composition and Phytoplankton Biomass on the Adjacent Shelf

Abstract In the context of the REVIZEE programme, an extensive sampling cruise was carried out in the northern section of the Brazilian Exclusive Economic Zone on board O.V. Antares (Operation North III). Several parameters were surveyed along the Amazon continental shelf during this cruise, such as horizontal and vertical distributions of temperature, salinity, dissolved oxygen, pH, dissolved inorganic nutrients, and phytoplankton biomass. Water with salinity below 33 psu and high silicate content was observed throughout the shelf, indicating the influence of the Amazon River plume up to a distance of 147 km from the coast; pH always remained alkaline. Water temperature was relatively homogeneous at the surface, with an average of 28°C. A permanent thermocline was detected in oceanic regions. Coastal waters were eutrophic, well oxygenated (maximum of 6.54 mL O2 L−1), and presented high chlorophyll a (maximum of 9.8 mg chlorophyll a m−3) and nutrient concentrations (up to 9.54 μmol L−1 NO3−, 0.89 μmol L−1 PO42−, and 108.59 μmol L−1 Si044−). Oceanic waters adjacent to the Amazon shelf presented high transparency (Secchi depth up to 35 m) and chlorophyll a (mean: 0.1 mg m−3) and low nutrient concentrations (maximum of 1.58 μmol L−1 NO3−, 0.18 μmol L−1 PO42−, and 5.92 μmol L−1 Si044−). Cluster analysis performed with all data showed a clear separation between coastal and oceanic waters at the surface layer and at 1% light penetration layers. This separation into two groups of stations clearly represents areas with different degrees of influence from the discharges of the Amazon Basin. The Amazon River is very important to the nutrient budgets of the shelf.

Nutrient and phytoplankton biomass in the Amazon River shelf waters

The Amazon River estuary is notable at the Amazon Continental Shelf, where the presence of the large amount of water originating from the Amazon during the rivers falling discharge period was made evident by the low salinity values and high nutrient levels. Even so, the presence of oceanic waters in the shelf area was significant. Dissolved organic nitrogen was the predominant species of the nitrogen cycle phases, followed by total particulate nitrogen, nitrate, ammonium and nitrite. The chlorophyll a data in the eutrophic area indicated that there is sufficient nitrogen in the area to withstand productivity, though dissolved inorganic nitrogen removal processes are faster than regeneration or mineralization. The anomalous amounts of inorganic dissolved nitrogen showed more removal than addition. The simulations with the bidimensional MAAC-2D model confirmed that high nutrient waters are displaced northwest-ward (two cores at 2.5 degrees N-50 degrees W and 4 degrees N-51 degrees W) by the stronger NBC during falling river discharge. During high river flow period these nutrient-rich lenses are distributed around 0.5 degrees N-48.5 degrees W as well as along the shallow Amazonian shelf (20 m-50 m depth, 1 degree N-3.5 degrees N), as a result of the spreading of Amazon freshwater outflow.

Observações hidrológicas e resultados de modelagem no espalhamento sazonal e espacial da pluma de água Amazônica

In this study, we present surface synoptic data collected during four oceanographic cruises undertaken in March-April 1995, October-November 1997, April-May 1999 and August-September 2001 in the Brazilian Program “REVIZEE/SCORE-NO” and a combination of model results (1/6 deg.). The emphasis of this paper is to point out the monthly changes on the spreading of the Amazon plume over the external Amazon shelf area and the eastern region of the Amazon River. Hydrographic data and model results demonstrated that during March-May, the Amazon plume moved southwestward along the northern coast of Brazil, decreasing during August-September; but this was not observed during October-November. Model results revealed ring signatures shedding from the North Brazil Current (NBC). Results also showed that during August the Amazon plume encircling the NBC retroflection was around 7o N.

Estudo das diferentes formas de fósforo nas águas da plataforma continental do Amazonas

Hydrological samples were collected on the continental shelf of the Amazon river to determine particulate organic and inorganic matter, dissolved organic phosphorus (DOP), phosphate, total particulate phosphorus (TPP), chlorophyll a, temperature, salinity, pH, water transparency, dissolved oxygen (DO) and saturation rate. The objective was to study the forms of DOP, phosphate and TPP. In the euphotic layer, the fluvial discharge from the Amazon river favored the distribution of phosphate, TPP and DOP. In the aphotic layer, the phosphate concentration increased due to the decomposition of DOP and TPP. This increase is due to the absence of photosynthetic processes.

An Analysis of Total Phosphorus Dispersion in Lake Used As a Municipal Water Supply

In Belém city is located the potable water supply system of its metropolitan area, which includes, in addition to this city, four more municipalities. In this water supply complex is the Água Preta lake, which serves as a reservoir for the water pumped from the Guamá river. Due to the great importance of this lake for this system, several works have been devoted to its study, from the monitoring of the quality of its waters to its hydrodynamic modeling. This paper presents the results obtained by computer simulation of the phosphorus dispersion within this reservoir by the numerical solution of two-dimensional equation of advection-diffusion-reaction by the method θ/SUPG. Comparing these results with data concentration of total phosphorus collected from November 2008 to October 2009 and from satellite photos show that the biggest polluters of the water of this lake are the domestic sewage dumps from the population living in its vicinity. The results obtained indicate the need for more information for more precise quantitative analysis. However, they show that the phosphorus brought by the Guamá river water is consumed in an area adjacent to the canal that carries this water into the lake. Phosphorus deposits in the lake bottom should be monitored to verify their behavior, thus preventing the quality of water maintained therein.

AVALIAÇÃO DA CONCENTRAÇÃO DE METAIS NA ÁGUA SUBTERRÂNEA CONSUMIDA EM COMUNIDADES AMAZÔNICAS BRASILEIRAS

Este artigo visa avaliar a concentracao de metais na agua subterrânea consumida em comunidades amazonicas, considerando os riscos que os altos teores de metais podem ocasionar a saude dessa populacao. Foram analisadas 24 amostras de agua em dois periodos distintos, menor e maior precipitacao pluviometrica, para determinacoes de: cor aparente, turbidez, cloreto, solidos totais dissolvidos, N-amoniacal, nitrito, nitrato, bario, chumbo, cobre, aluminio, ferro, manganes, sodio, zinco. Os resultados foram enquadrados nas legislacoes vigentes para consumo humano e submetidos a uma analise de componentes principais para combinar linearmente as variaveis estudadas. Palavras-chave: agua subterrânea, qualidade da agua, legislacao. ABSTRACT The article aims to evaluate the concentration of metals in groundwater consumed in Amazonian communities, considering the risks that high metals concentration can cause to population health. 24 water samples were analyzed in two different periods, lower and higher rainfall periods, in order to determinate the following parameters: apparent color, turbidity, chloride, total dissolved solids, ammonia-N, nitrite, nitrate, barium, lead, copper, aluminum, iron, manganese, sodium, zinc. The results were classified in the current legislations for human consumption and submitted to the main components analysis in order to combine linearly the studied variables. Keywords: groundwater, water quality, legislation.