Natural occurrence of hexavalent chromium in a sedimentary aquifer in Urânia, State of São Paulo, Brazil

Abstract

Anomalous concentrations of hexavalent chromium have been detected in groundwater of the Adamantina Aquifer in at least 54 municipalities located in the northwestern region of the State of São Paulo, southeast Brazil, occasionally exceeding the permitted limit for human consumption (0.05 mg.L -1 ). An investigation was conducted in the municipality of Urânia, where the highest concentrations of chromium were detected regionally. It was defined that the origin of this contamination is natural, since high concentrations of chromium were detected in aquifer sandstones (average of 221 ppm) and also in pyroxenes (6000 ppm), one of the main heavy minerals found in the sediments. Besides, no other possible diffuse or point sources of contamination were observed in the study area. Stratification of groundwater quality was observed and the highest concentrations of Cr 6+ were detected at the base of the aquifer (0.12 mg.L -1 ), where groundwater shows elevated values for redox potential (472.5 mV) and pH (8.61). The origin of Cr 6+ in water may be associated with the weathering of pyroxene (augite), followed by the oxidation of Cr 3+ by manganese oxides. The highest concentrations of Cr 6+ are probably related to desorption reactions, due to the anomalous alkaline pH found in groundwater at the base of the aquifer.

Local and Global Sensitivity Analysis of Cr (VI) Geogenic Leakage Under Uncertain Environmental Conditions

“…The relevance of the setting considered is supported by the observation that nonnegligible concentrations of dissolved Cr (VI) in groundwater bodies are documented in diverse geographical regions. For example, alarming concentrations of Cr (VI) are registered in Countries such as Italy, United States (California), Greece, Mexico, Japan, Indonesia, Brazil, and Australia (e.g., Apollaro et al, 2011;Bourotte et al, 2009;Fantoni et al, 2002;Gray, 2003;Kaprara et al, 2015;Kazakis et al, 2015Kazakis et al, , 2017Lelli et al, 2013;Mills et al, 2011;Morrill et al, 2013;Robles-Camacho & Armienta, 2000;Saputro et al, 2014). It is now well established that the presence of Cr (VI) in natural waters can be linked to anthropogenic pollution and/or geogenic origins.…”

Occurrence of Cr(VI) in drinking water of Greece and relation to the geological background

“…However, recent surveys [8][9][10] support the natural occurrence of chromium, verified by the presence of Cr-containing minerals (chromite, Fechromite, Cr-bearing goethite and silicates) in the Asopos basin. The contact of water with ultramafic rocks and soils such as serpentinite, dunites, and ophiolites was also proved the cause of high Cr(VI) concentrations in numerous cases in Mexico [11], California [12][13][14], Zimbabwe [15], Italy [16], Brazil [17], Japan and Indonesia [18].…”

Aspects of Hexavalent Chromium Pollution of Thebes Plain Aquifer, Boeotia, Greece

“…Hexavalent chromium pollution is a common phenomenon, since several case studies can be mentioned from all around the world such as Urania State of Sao Paolo, Brazil [1]; La Specia Province, Italy [2]; Leon Valley, Mexico [3]; and Mojave Desert, California, USA [4]. Also in the USA., in four major lakes of the Mississippi, pollutant toxic metals including chromium have been detected [5]; additionally, pollutant substances have been found in bottom sediments of Lake Symsar, Poland [6].…”