Hydraulic and geochemical interactions between surface water and sediment pore water in seasonal hypersaline Maharlu Lake, Iran

Abstract

Study of interactions between surface‐water and pore‐water in lakes is complicated due to spatio‐temporal heterogeneities in flow condition across the sediment–water interface. In this study, seasonal hypersaline Maharlu Lake was investigated by collecting surface‐water and pore‐water samples from four nests of multilevel piezometers installed at different distances from the inflow of rivers to the lake. The hydraulic heads in the piezometers as well as vertical profiles of Mg+2, Na/Cl, and Br/Cl were used to investigate both hydraulic and geochemical interactions between surface‐water and pore‐water in the lake. Depletion of lake surface water and pore water with respect to B, Br, Li+, K+, Mg2+ and the absence of Mg‐K chlorides and sulphates in the lake bed sediments is probably due to leakage of highly evaporated residual brine from the lake. Hydraulic gradients in the multilevel piezometric nests indicate that a general downward flow from surface‐water to pore‐water occurs across sediment–water interface. Vertical profiles of Br/Cl, Mg2+, and Na/Cl showed that the maximum flow rate was more than 1 m/yr close to the mouth of the inflowing rivers. The downward vertical flow was limited in the area far from the inflowing rivers due to the presence of an impermeable confining halite layer which interrupts the hydraulic connection between shallow pore water (less than 50 cm deep) and deeper zones. The hydraulic and geochemical interactions between surface‐water and pore‐water across sediment–water interface in the Maharlu Lake are of interest to find out the fate of pollutants and their distribution in the lake.

Sources, concentrations, distributions, fluxes and fate of microplastics in a hypersaline lake: Maharloo, south-west Iran

“…The specific conductance of the lake samples averages about 480 mS cm -1 , and this is equivalent to a salinity of about 385 parts per thousand. Assuming that halite is the principal salt present in the lake (Khosravi et al, 2020), the water is saturated with a density of about 1.2 g cm -3 (Sigma-Aldrich, 2018). Such a high density inhibits the settlement of four out of six polymer types detected, or, according to Table 1, about 80% of the MPs in lake water.…”

“…The bedrock of the lake is underlain by silty limestone and marl from the Oligo-Miocene age, and the high salinity lake is due to the presence of Late Proterozoil salt domes in the catchment (Forghani et al, 2012). Sediments consist of successive layers of halite, black, organic rich sediment, green-grey sulphates, halite and carbonates, and fine, brown aluminosilicates, with the depths of each layer exhibiting considerable spatial variation throughout the lake (Khosravi et al, 2020).…”

Factors and processes controlling hydrochemistry and evaporitic deposits in hypersaline wetland‐shallow lake systems

“…Hypersaline or saline lakes usually occur under arid, semiarid, and subhumid climates where evaporation exceeds precipitation (Canevari et al, 1999;Hardie et al, 1978). Geology, geomorphology, tectonics, and climate are factors that determine the surface and groundwater flows and the distribution and features of hypersaline and evaporite environments around the world (e.g., Allen & Collinson, 1986;Cohen, 2003;Jones & Deocampo, 2003;Khosravi et al, 2020;Last & Vance, 1997;Lowenstein et al, 2003;Sun et al, 2016;Talbot & Allen, 1996). These factors also control the geochemical processes that determine the chemical composition of groundwater and surface water and consequently control the type of evaporite minerals that are formed in hypersaline wetlands and shallow lakes.…”