Geochemistry of water and ground water in the Nhecolândia, Pantanal of Mato Grosso, Brazil: variability and associated processes

Abstract

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Biogeochemical processes and the diversity of Nhecolândia lakes, Brazil

“…In October 2008, 19 lakes were sampled for hydrogeochemistry and 14 for limnological analyses, of which seven were EC < 750 μS.cm −1 and 12 EC > 2,000 μS.cm −1 . The results of the chemical analyses showed that all the waters were extremely poor in Ca 2+ and Mg 2+ but, in the salinas, rich in Na + and K + , as stated in the general literature (Zavarzin 2002) and that on Nhecolândia (Barbiero et al 2002. Table II presents the results of the August 2007 sampling, where the poverty in Ca 2+ and Mg 2+ ions is clear.…”

“…Such differences are essentially due to the greater isolation of the salinas from phreatic recharge by continuous horizons of greenish and grizzly soil of low porosity . Despite these different salinities, Barbiero et al (2002) and Furquim et al (2010) concluded that the salinas and baías waters belong to the same chemical family, excluding the possibility that the salinity is a legacy of past climatic periods. The isolation of the saline lakes is associated with high alkalinity, which helps to attack the quartzose sand and silt, supplying silica (in solution probably as H 3 SiO − 4 or H 2 SiO 2− 4 ) to precipitate Mg silicates (saponite and stevensite), illite and the amorphous silica cementing the grains of quartzose sand.…”

“…Like the Rift Valley lakes, the lakes of Nhecolândia have a water deficit (Por 1995. The waters are poor in Ca 2+ and Mg 2+ (Barbiero et al 2002, Furquim et al 2010, and there are frequent cyanobacteria blooms and an increase in salinity during the dry season (De-Lamonica-Freire and Heckman, 1996, Oliveira and Calheiros, 2000, Medina-Júnior and Rietzeler 2005. It is important to note that the hypothesis that alkalinisation in the lakes of Nhecolândia originates from carbonate massifs has been completely discarded.…”

Natural arsenic in groundwater and alkaline lakes at the upper Paraguay basin, Pantanal, Brazil

“…Until now, the salt has always been attributed to alternating humid and arid phases during the Pleistocene (i.e., inherited from the past), but Barbiéro et al (2002) have shown a unique geochemical family of waters evolving currently in an alkaline manner under the influence of evaporation [index word 3]. The geochemical composition changes gradually from feebly mineralised waters that flood the region during the rainy season to the strongly mineralised ones in the salinas.…”

Soil morphological control on saline and freshwater lake hydrogeochemistry in the Pantanal of Nhecolândia, Brazil

“…More recently, it was shown that all the waters of this region belong to the same chemical family (Barbiero et al, 2002) and that the changes observed in the chemical composition (major elements) result from salt precipitation associated with the concentration process. Therefore, the saline lakes could arise from the present-day concentration of lowsalinity waters that supply the Pantanal area each year.…”