Hydrogeochemical characterization of reservoir waters undergoing salinization processes in Northeastern Brazil

Abstract

The geochemical processes that potentially control the chemical characteristics of the waters of three reservoirs located in the state of Sergipe, Northeastern Brazil, were evaluated using the Gibbs diagram, correlation analysis, ionic ratios and geochemical modeling. The results of the reverse geochemical modeling applied between two water samples from each reservoir were in agreement with the observations of the correlation analysis and ionic ratios, which indicated sea salt dissolution, silicate weathering and, to a lesser extent, carbonate dissolution, as the main geochemical processes responsible for the chemical characteristics of the waters of the three reservoirs, also confirming the importance of ion exchange for the Macela and Ribeirópolis reservoirs. These findings therefore suggest that the growing salinization process of the reservoirs is mainly controlled by water-rock interactions and may also be influenced by contributions from evaporation and anthropogenic inputs.

Geochemical modeling of the evaporation process in salinized reservoirs in the semi-arid region of Northeastern Brazil

“…The value of A for the samples ranged from -8.5% to 3.7% with an absolute mean value of 3.5% for the Algodoeiro reservoir, from -4.7% to 2.5% with an absolute mean value from 2.1% for Três Barras and from -5.5% to -5.2% with an absolute mean value of 3.7% for Glória. These values are in agreement with the absolute mean values reported by Merchán et al (2015), which ranged from 2.5% to 4.4% when assessing salinization in an irrigation basin in Spain, and with the absolute mean values indicated by Alves et al (2021), which ranged from 2.5% to 3.0% when evaluating reservoirs undergoing salinization in Northeastern Brazil. According to El Yaouti et al ( 2009), a ± 10% error in the ion balance is acceptable for this type of study.…”

“…They also highlighted that the local geology favors silicate weathering as the most likely cation and bicarbonate source. Alves et al (2021), when assessing reservoirs undergoing increasing salinization processes in northeastern Brazil, also concluded that atmospheric transport and silicate were the main geochemical processes responsible for the chemical characteristics of the waters of the investigated reservoirs, with a smaller contribution to carbonate dissolution. Wisitthammasri et al (2020) indicated that the fact that they did not observe a relationship between (Ca 2+ + Mg 2+ ) with HCO 3 -, in agreement with the theoretical range predicted for carbonate dissolution, is an indication that water hydrochemistry in the Province of Saraburi/Thailand is consistent with silicate minerals.…”

“…The impacts of salinization, irregular demands and large periods without water renewal have been highlighted by Santos et al (2000) and Alves et al (2021) in studies concerning reservoirs located in Northeastern Brazil. For Santos et al (2000), the salinization of reservoirs located in southwestern Bahia has increased with reservoir age and/or the hydraulic retention time, while Alves et al (2021) observed that the salinization process in reservoirs located in the state of Sergipe intensified in reservoirs with longer hydraulic retention time and with low demand for accumulated water.…”

Intervening Factors in the Groundwater Salinization Process, Cachoeira River Basin, Northeastern Brazil

“…During the direct ion exchange reaction, Na + (± K + ) ions from the surface of clay minerals are displaced by Ca 2+ (± Mg 2+ ) ions present in the water, resulting in the enrichment of water in Na + (± K + ) (Alves et al 2021). Direct ion exchange with clay materials is generally observed when water is being salinized (Slama & Bouhlila 2017).…”

“…In this context, Gomes and Franca (2019) state that the studying the groundwater chemistry can provide information on anthropogenic interference and dissolution/precipitation processes. Water salinization, a frequent problem in northeastern Brazil, can affect freshwater reservoirs, and poses a risk for human health and to many natural systems (Alves et al 2021). The literature (Fontes et al 2015;Guo et al 2018;Jia et al 2020) highlights that salinization occurs as a function of climatic conditions, reservoir age, rock solubility, marine aerosol deposition, etc.…”