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Article

Nitrate Contamination in Brazilian Urban Aquifers: A Tenacious Problem

1
CEPAS|USP Groundwater Research Center, Institute of Geosciences, University of São Paulo, São Paulo 05508-080, Brazil
2
G360 Institute for Groundwater Research, University of Guelph, Guelph, ON N1G 2W1, Canada
3
Pampulha Campus, Department of Geology, Federal University of Minas Gerais, Belo Horizonte 31270-901, Brazil
4
Geological Institute, Secretariat of Infrastructure and Environment of the Government of the State of São Paulo, São Paulo 04015-12, Brazil
5
Geosciences Department, University of Calgary, Calgary, AB T2N 1N4, Canada
*
Author to whom correspondence should be addressed.
Water 2020, 12(10), 2709; https://doi.org/10.3390/w12102709
Received: 31 August 2020 / Revised: 21 September 2020 / Accepted: 24 September 2020 / Published: 27 September 2020
(This article belongs to the Special Issue Groundwater and Contaminant Transport)
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 (<20 m deep), with average nitrate of 63 mg/L-NO3; intermediate (20–60 m), with 30 mg/L-NO3; and deep (>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. View Full-Text
Keywords: nitrate; groundwater contamination; urban hydrogeology; urban aquifer recharge nitrate; groundwater contamination; urban hydrogeology; urban aquifer recharge
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MDPI and ACS Style

Hirata, R.; Cagnon, F.; Bernice, A.; Maldaner, C.H.; Galvão, P.; Marques, C.; Terada, R.; Varnier, C.; Ryan, M.C.; Bertolo, R. Nitrate Contamination in Brazilian Urban Aquifers: A Tenacious Problem. Water 2020, 12, 2709. https://doi.org/10.3390/w12102709

AMA Style

Hirata R, Cagnon F, Bernice A, Maldaner CH, Galvão P, Marques C, Terada R, Varnier C, Ryan MC, Bertolo R. Nitrate Contamination in Brazilian Urban Aquifers: A Tenacious Problem. Water. 2020; 12(10):2709. https://doi.org/10.3390/w12102709

Chicago/Turabian Style

Hirata, Ricardo, Fabiana Cagnon, Aline Bernice, Carlos H. Maldaner, Paulo Galvão, Carlos Marques, Rafael Terada, Claudia Varnier, M. C. Ryan, and Reginaldo Bertolo. 2020. "Nitrate Contamination in Brazilian Urban Aquifers: A Tenacious Problem" Water 12, no. 10: 2709. https://doi.org/10.3390/w12102709

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