Investigação hidrogeoquímica do cromo no aquífero Adamantina no município de Urânia - SP

Abstract

Anomalous concentrations of chromium VI, sometimes exceeding the maximum limit permitted for human consumption (0.05 mg/L), have been detected in groundwater from the Northwestern region of São Paulo state. Previous studies indicated that this ocurrence is of natural origin. The city of Urânia was selected for the study since the local aquifer has the highest and most persistent contents of chromium in this region. As part of a geochemical investigation of rock-water interaction, this article describes the chemical, mineralogical and petrographical characterization of sandstone samples taken from boreholes that reached the depth of 100 m, aiming to identify in which layers and in which manner chromium is inserted in the solid phase. Solid phase analyses were performed by X-ray fluorescence, X-ray diffraction and scanning electron microscopy (SEM). The results of this investigation indicated that: (1) the concentration of chromium in the Urânia sandstones is anomalous, since the average value obtained (221 mg/kg) is quite higher than the reported average concentration for a generic sandstone (35 mg/kg) and for soils from another regions of São Paulo state (26,3 mg/kg); (2) the highest chromium concentrations were detected in the depths of around 50 meters (336 mg/kg); (3) chromium concentrations reached values of 6.000 ppm in pyroxen (augite) crystals, which is one of the main heavy minerals of the sandstones; and (4) chromium concentrations on clay minerals and on iron hidroxydes are also relatively high (up to 650 ppm).

Soil, water and plants contamination by total chrome and chrome VI

“…Is presented in several Chemical composts which are employed in industrial processes, amongst them chromage (Gomez & Callao, 2006). Apart of that, Marcolan (2009) adds that the Cr VI) general possesses a greater solubility, mobility and biodisponibility in the environment when compared to Cr (III). The concentration determination of its biodisponibility, there for is important to specify the Cr, for the total knowledge and its biodisponibility in the soil and water (López‐ mosquera et al., 2000).…”

Influência da infraestrutura urbana nas águas subterrâneas na cidade de Urânia (SP)

“…Dados dos poços tubulares, profundos e cacimbas como suas localizações, perfis construtivos e histórico de análises químicas foram consultados em teses e dissertações de Almodovar (2000), Cagnon (2003), Marcolan (2009), Bertolo et aç (2009) Depois, procedeu-se com a instalação de tubos geomecânicos com diâmetros de 4 polegadas aninhados em três níveis 30, 50 e 70 m, com filtros de 6, 4 e 4 m na porção final de cada poço.…”

“…Após Cagnon (2003), vieram outros como Varnier et al (2007), Marcolan (2009), Bourrotte et al (2009), Maldaner (2010), Berenice (2010), Marques (2019) e Hirata et al (2020), este último confirmando que, embora ocorra uma sistemática desativação de poços cacimbas, tubulares, profundo e de fossas negras, as concentrações de nitrato ainda apresentam valores compatíveis com os trabalhos conduzidos na área, quando espera-se que o aumento da eficiência do sistema sanitário promova reduções no aporte de efluentes no aquífero. Apesar do reconhecimento da existência da contaminação abaixo da malha urbana, os mecanismos que a mantem não estavam claros.…”