Nitrate Contamination in Brazilian Urban Aquifers: A Tenacious Problem

Autor: Carlos Henrique Maldaner, Carlos Henrique Gil Marques, Aline Michelle Bernice, Ricardo Hirata, Fabiana Alves Cagnon, Reginaldo Antonio Bertolo, Paulo Galvão, M. Cathryn Ryan, Claudia Varnier, Rafael Terada
Rok vydání: 2020
Předmět:
Zdroj: Repositório Institucional da USP (Biblioteca Digital da Produção Intelectual)
Universidade de São Paulo (USP)
instacron:USP
Water
Volume 12
Issue 10
Water, Vol 12, Iss 2709, p 2709 (2020)
ISSN: 2073-4441
DOI: 10.3390/w12102709
Popis: This study follows the geochemistry of nitrogen in a Cretaceous and unconfined sedimentary aquifer in the city of Urâ
nia (Brazil) over 20 years. Although the sewer network was built in the 1970s, the nitrate contamination problem (>
45 mg/L-NO3&minus
) 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&minus
), 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&minus
intermediate (20&ndash
60 m), with 30 mg/L-NO3&minus
and deep (>
60 m), with 17 mg/L-NO3&minus
The current total nitrate mass in the aquifer exceeds 731 kg-NO3&minus
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.
Databáze: OpenAIRE