DEGEO - Departamento de Geologia

URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/8

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20202

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Assunto: search.filters.subject.Groundwater contamination

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Agora exibindo 1 - 2 de 2
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    Nitrate contamination in Brazilian urban aquifers : a tenacious problem.
    (2020) Hirata, Ricardo; Cagnon, Fabiana Alves; Bernice, Aline Michelle; Maldaner, Carlos Henrique; Galvão, Paulo Henrique Ferreira; Marques, Carlos Henrique Gil; Terada, Rafael; Varnier, Claudia Luciana; Ryan, M. Cathryn; Bertolo, Reginaldo Antonio
    This study follows the geochemistry of nitrogen in a Cretaceous and unconfined sedimentary aquifer in the city of Urânia (Brazil) over 20 years. Although the sewer network was built in the 1970s, the nitrate contamination problem (>45 mg/L-NO3 −) persists to this day. The oldest urbanization areas located in the north of the city initially used cesspits for wastewater and currently present the highest nitrate concentrations (>120 mg/L-NO3 −), with the plume reaching the deeper aquifer portions (up to 100 m). The contamination is not as dramatic in the south part of the city, where urbanization including installation of the sewage network with PVC pipes that are more resistant to leak than the old ceramic networks occurred after 1985. Based on the constructive well profiles, three hydrogeochemical zones were established: shallow (60 m), with 17 mg/L-NO3 −. The current total nitrate mass in the aquifer exceeds 731 kg-NO3 −. Numerical flow (Modflow) and transport (MT3D) model scenarios support the hypothesis that the nitrate contamination is caused by substantial infiltration of nitrogen through the cesspits until the 1970s, but after the 1990s, leaks from the sewer network should be responsible for the maintenance of the recently observed high concentrations of nitrate.
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    Natural background levels and validation of the assessment of intrinsic vulnerability to the contamination in the Carste Lagoa Santa Protection Unit, Minas Gerais, Brazil.
    (2020) Cardoso, Frederico Aragão; Velásquez, Leila Nunes Menegasse; Galvão, Paulo Henrique Ferreira; Tayer, Thiaggo de Castro; Lucon, Thiago Nogueira; Azevedo, Úrsula Ruchkys de
    The contamination of karst aquifers by anthropogenic activities causes a major issue regarding environmental policies, since they present high sensitivity, influenced by unique features such as dolines, swallow holes, and conduits. This paper is focused on the Carste Lagoa Santa Protection Unit, MG, Brazil, and presents three main objectives: to determine the natural background levels of chloride, nitrate, sulfate, and phosphate; to indicate the locations where the concentrations of those parameters exceed the natural background levels in the existing vulnerability map and, finally, to determine the proportion of the areas (in percentage) where this surpassing occurs, according to the vulnerability classes (high, moderate and low). Results have shown values (90th percentile) of 2.4 mg/L, 1.0 mg/L, 5.3 mg/L, and 0.1 mg/L, for Cl−, NO3−, SO4−2, and PO4−3, respectively, indicating that for all four parameters, there were areas (mainly distributed within moderate vulnerability portions) where the values were surpassed, which suggests anthropogenic activity due to the presence of urban settlements and agricultural activities. Therefore, the proposal of natural background levels was essential to understand the hydrochemistry of the studied region.