Journals Information
Environment and Ecology Research Vol. 11(6), pp. 979 - 992
DOI: 10.13189/eer.2023.110609
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Hydrogeochemical Characteristics of Subsurface and Overland Runoff Indicating Seawater Intrusion into Deep Coastal Aquifers
Lalita Zakharikhina 1,*, Sergey Zakharikhin 1, Polina Lesnikova 1, Olga Bykhalova 2
1 Federal Research Centre the Subtropical Scientific Center of the Russian Academy of Sciences, Russian Federation
2 Federal State Budgetary Organization, State Nature Reserve, Russian Federation
ABSTRACT
Seawater intrusion (SI) into deep freshwater aquifers is a serious problem in coastal areas around the globe that has been exacerbated in recent decades by climate change and rising sea levels. Pumping and seawater upcoming can intensify the mixing of groundwater and seawater within the aquifer to the point where fresh groundwater becomes unfit for drinking. Here, based on the study of subsurface and overland runoff (seepage, springs, and streams) conducted in the pristine Utrish Nature Reserve on the Russian Black Sea coast, several geochemical characteristics of the runoff indicating the occurrence of SI have been identified for the first time. We have termed the diffusion of highly diluted seawater from the seawater-freshwater mixing zone into deep aquifers and subsequently into subsurface and overland runoff the secondary contamination (SC) of subsurface and overland runoff. The identified characteristics are: positive correlation of excess trace elements with Cl and SO4 anions predominant in seawater, consistently higher Br content (marine factor) in spring water compared to stream water, and, conversely, lower concentrations of Al, Cr, Zn, Cs, and all rare earth elements (REEs) (terrestrial factor). Furthermore, overland and subsurface runoff exhibited anomalous REE fractionation relative to rocks, channel sediments, and soils. The occurrence of europium (Eu/Eu* = 3.96 in spring water and Eu/Eu* = 1.44 in stream water) was a positive anomaly attributed to changes in redox potential at the geochemical barrier at the seawater-freshwater interface. The impact of SI on stream water and springs fed by perched aquifers was linked to the topography of the area characterized by low hypsometry. The geochemical indicators described in this study will help establish the occurrence and magnitude of SI in groundwater aquifers in coastal areas without resorting to suboptimal sampling methods, such as drilling, which can damage aquifers. Furthermore, these indicators can serve as reference benchmarks for monitoring SI intensity in heavily used coastal aquifers to control pumping rates and reduce contamination by seawater due to upcoming and mixing for enhanced coastal water security.
KEYWORDS
Hydrogeochemical Parameters, Overland and Subsurface Runoff, Seawater Intrusion
Cite This Paper in IEEE or APA Citation Styles
(a). IEEE Format:
[1] Lalita Zakharikhina , Sergey Zakharikhin , Polina Lesnikova , Olga Bykhalova , "Hydrogeochemical Characteristics of Subsurface and Overland Runoff Indicating Seawater Intrusion into Deep Coastal Aquifers," Environment and Ecology Research, Vol. 11, No. 6, pp. 979 - 992, 2023. DOI: 10.13189/eer.2023.110609.
(b). APA Format:
Lalita Zakharikhina , Sergey Zakharikhin , Polina Lesnikova , Olga Bykhalova (2023). Hydrogeochemical Characteristics of Subsurface and Overland Runoff Indicating Seawater Intrusion into Deep Coastal Aquifers. Environment and Ecology Research, 11(6), 979 - 992. DOI: 10.13189/eer.2023.110609.