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Chemical Factors
Published in Michael J. Kennish, Ecology of Estuaries Physical and Chemical Aspects, 2019
The chemical precipitation of gypsum (CaSO4 · 2H2O) and anhydrite (CaSO4 minerals in evaporite deposits (i.e., chemical sedimentary rocks) removes sulfate ions from seawater. The formation of halite (NaCl) and sylvite (KC1) minerals extracts chloride ions from solution. These minerals are chemically precipitated in isolated seas and lagoons by the concentration of soluble salts from evaporating waters.36,37
Hydrogeochemical characterization, multi-exposure deterministic and probabilistic health hazard evaluation in groundwater in parts of Northern India
Published in Toxin Reviews, 2023
Herojeet Rajkumar, Pradeep K. Naik, Gagandeep Singh, Madhuri Rishi
All the groundwater samples have SI <0 i.e. negative (-) values for anhydrite (-3.16 to −2.62 and −3.39 to −2.50), gypsum (-2.95 to −2.34 and −3.06 to −2.17), halite (-9.02 to −7.25 and −9.0 to −7.33) and sylvite (-9.52 to −7.94 and −9.55 to −7.68) for pre and post monsoon seasons (Table S3). The negative SI values for anhydrite and gypsum also corroborate the results of geochemical signatures discussed in section 3.2; thus, dissolution will continue to release Ca2+ and SO42− ions in the aquifer system. Further, the SI values (-) for halite mineral supports the role of restricted dissolution in the contribution of Na+ and Cl- ions (as discussed in above section 3.2) in the groundwater of the study area. The plots between SI vs. EC indicate that anhydrite and gypsum minerals are more influenced in the hydrochemistry due to the faster dissolution process than halite and sylvite [Figure S2(a–d)]. Also, the increasing trend of SI values of anhydrite, gypsum, halite, and sylvite along with EC divulges that the dissolution of these minerals in the aquifer system with time may directly lead to groundwater salinity.
Multi-parametric groundwater quality and human health risk assessment vis-à-vis hydrogeochemical process in an Agri-intensive region of Indus basin, Punjab, India
Published in Toxin Reviews, 2022
Vijay Jaswal, Ravishankar Kumar, Prafulla Kumar Sahoo, Sunil Mittal, Ajay Kumar, Sunil Kumar Sahoo, Yogalakshmi Kadapakkam Nandabalan
The piper plot (Figure 6(b)) shows that the majority of groundwater samples are characterized as Ca-Mg-Cl, followed by Ca-Mg-SO42− and Na-Cl types in the region. This indicates that alkaline earth metals are dominating over alkali metals, and SO42− and Cl are dominant anions. Water type Ca-Mg-Cl might be originating from the dissolution of the carbonates, i.e. limestone and dolomite, and chloride rich minerals, while the Ca-Mg-SO42− type in groundwater is attributed to their contribution through gypsum and carbonate weathering. The Na and Cl concentrations in groundwater can be linked to the weathering of silicate rocks, evaporation process and/or seawater intrusion (Narany et al.2014). The dominance of rock-weathering process indicates Na mainly comes through the dissolution of acidic silicate minerals that are usually present in alluvial rocks of this region. Further, the molar ratio of Na/Cl > 1 in the majority of samples also indicate the absence of halite and dominancy of silicate weathering in the study area (Singh et al.2011). The significant presence of Ca and Mg and the Ca/Mg ratio <1 in the majority of samples was indicating the dominancy of calcite weathering. Similarly, the molar ratio Ca/SO42− <1 in most of the samples indicate calcite as the major source of Ca (Singh et al.2014). The dominance of HCO3− ion among carbonate species in groundwater indicated bicarbonate alkalinity as the major source of alkalinity. Weathering of carbonate minerals may be the reason for an elevated level of HCO3− ions in groundwater of the study area (Rao et al.2017), although silicate weathering may also be responsible for enhancing groundwater alkalinity (Singh et al.2011, Bottrell et al.2019). The detailed impacts of natural lithology and the influence of anthropogenic practices have been assessed by PCA, HCA and PCM analyses in the next section for the major existing contaminants of groundwater.
Isotopic and chemical facies for assessing the shallow water table aquifer quality in Goly Region, White Nile State, Sudan: focusing on nitrate source apportionment and human health risk
Published in Toxin Reviews, 2021
Ibrahim E. A. Idriss, Mussa Abdel-Azim, Kamal I. Karar, Saida Osman, Abubakr M. Idris
The current PCA reveals that the loadings of the first two components are almost similar, i.e. 22%. Component-1 recorded a strong positive loading by fluoride (0.83) as well as strong negative loadings by TH (–0.97), magnesium (–0.77), and calcium (–0.77). Moderate positive loadings were also observed by pH (0.72), EA (0.55), and sodium (0.67), whereas moderate negative loading was observed by potassium (–0.73). It may suggest that this component represents the parameters of natural origin, which may be due to weathering processes (Popugaeva et al.2020). Component-2 recorded strong positive loadings by EC (0.87), TDS (0.87), sulfate (0.80), and chloride (0.92). In addition, positive moderate loadings were obtained by nitrate (0.74), nitrite (0.68), and sodium (0.59). In contrast, it could be suggested that component-2 represents parameters of anthropogenic contribution. It is known that chloride in groundwater is considered an indicator of contribution by animal and human sewage as well as the use of fertilizers (Minet et al.2017). Notably, sodium contributed to both component-1 and component-2. This means that sodium in the shallow water table aquifer was of both natural and anthropogenic origins. While sodium of anthropogenic origin may be attributed to the use of sodium-based fertilizers, sodium of natural origin may be attributed to the dissolution of halite mineral (Ogrinc et al.2019). While Component-4 was positively and strongly loaded by SWL (0.72), T (0.76), and depth (0.79), Component-6 was positively and strongly loaded by altitude (0.75). The loadings of the rest of parameters in Component-4 and Component-6 were all weak. Hence, Component-4 and Component-6 were in favor of physical characteristics (Popugaeva et al.2020). Notably, Component-5 was significantly characterized by ammonia since it is the only parameter that recorded strong and negative loading (0.88), while all other parameters recorded weak loadings. This result may suggest anthropogenic enrichment by fertilizers to groundwater samples (Jia et al.2020). Nevertheless, enrichment by fertilizers may not be significant as the representative factor has a loading of 7.1% of the whole module.