Major ions and rare earth elements hydrogeochemistry of the Atibaia and Jaguari rivers subbasins (Southeast Brazil)

Autor(es)

Mortatti, Bruno Cesar ^[1] ; Enzweiler, Jacinta ^[1]

Afiliação do(s) autor(es)

^[1] Univ Estadual Campinas, Inst Geosci, UNICAMP, Rua Carlos Gomes 250, BR-13083855 Campinas, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: APPLIED GEOCHEMISTRY; v. 111, DEC 2019.
• Citações Web of Science: 0

Resumo

The rivers that comprise the Atibaia and Jaguari medium size subbasins and their interconnected reservoirs (Cantareira Water System) provide drinking water for about one-third of Sao Paulo's State population. Native vegetation covers nearly 30% of the catchments' territory, and the remaining comprises small-scale farming, reforestation, industries, and urban agglomerations. The study aimed to find at which extent the silicate rock lithologies, land uses, and the water transference between reservoirs influence the rivers' water composition. Forty-seven river water samples, collected before and after the dams during a rainy and a dry period, presented circumneutral pH values, while electric conductivity, major ions and dissolved organic carbon concentrations increased in the downstream direction, controlled by silicate weathering, noticeable anthropogenic inputs, and negligible seasonal influence. The water type is Na-Ca-HCO3, the overall total dissolved solids (TDS) presented one order of magnitude difference between higher and lower reaches, and evidences of solute transference between the two subbasins. River water turbidity was higher during the rainy season and positively correlated with the Sigma REE measured in the <0.22 mu m pore filtered samples because of the dispersion of sediments (eroded soil) in the water bodies. We show that rock weathered material dispersed in water can increase the Sigma REE and originate positive Ce anomalies in its filtrate, similar to features observed in normalized patterns in the river water samples. Most samples exhibited flat shale-normalized REE distributions, with less fractionation between light and heavy REE than the regional lithotypes. Most samples also presented positive Eu anomalies, which source are the rocks of the area. The more urbanized stretches of the rivers exhibited discrete anthropogenic Gd anomalies. The results of this study demonstrate increasing signatures from human activities in the water bodies. (AU)

• Processo FAPESP: 12/05024-2 - Hidrogeoquímica de lantanídeos em águas fluviais e subterrâneas: estudos de caso na região de Campinas, SP
• Beneficiário: Jacinta Enzweiler
• Modalidade de apoio: Auxílio à Pesquisa - Regular