Salinization of groundwater in the North German Basin: results from conjoint investigation of major, trace element and multi-isotope distribution

Abstract

Conjoint consideration of distribution of major, rare earth elements (REE) and Y (combined to REY) and of H, O, C, S, Sr isotopes reveals that four types of groundwater are distinguishable by their chemical composition presented by spider patterns. REY patterns indicate thermosaline deep water and two types of shallow saline groundwaters. Presence of connate waters is not detectable. Sr isotope ratios distinguish three sources of Sr: fast and slow weathering of biotite and K-feldspar in Pleistocene sediments, respectively, and dissolution of limestones. d 13 C(DIC) indicate dissolution of limestone under closed and open system conditions. Numerous samples show d 13 C(DIC) > 13& which is probably caused by incongruent dissolution of calcite and dolomite. The brines from below 1,000 m represent mixtures of pre-Pleistocene seawater or its evaporation brines and infiltrated post-Pleistocene precipitation. The shallow waters represent mixtures of Pleistocene and Recent precipitation salinized by dissolution of evaporites or by mixing with ascending brines. The distribution of water types is independent on geologic units and lithologies. Even the Tertiary Rupelian aquiclude does not prevent salinization of the upper aquifer.

Quaternary channels within the Northeast German Basin and their relevance on double diffusive convective transport processes: Constraints from 3‐D thermohaline numerical simulations

“…In particular, observed processes confirm hypothesizes suggested by previous hydrochemical studies [Tesmer et al, 2007;Möller et al, 2008]. The results corroborate major conclusions derived by previous two-dimensional numerical simulations , at the same time providing insights in novel aspects of the hydrodynamics of the system.…”

“…Following Möller et al [2008], an ascending flow component is the likely cause of the observed shallow salinization. This was not possible to be confirmed based on the results from previously published two-dimensional numerical investigations.…”

“…[74] However, Möller et al [2008] also observed salinization in the upper Shallow Aquifer in which the groundwater salt content exceeds concentrations typical for this system that cannot be explained without assuming a contribution from deep seated water bodies to the shallow groundwater dynamics. Following Möller et al [2008], an ascending flow component is the likely cause of the observed shallow salinization.…”

“…These hydrogeological windows are manifested either by locations where the Rupelian Aquitard was primarily not deposited or was removed after its deposition by erosional Quaternary channels filled with highly permeable glacial deposits. Interaquifer hydraulic connections were suggested by previous hydrochemical studies performed for different areas in the basin [Tesmer et al, 2007 andMöller et al, 2008]. Based on an analysis of stable H and O isotopes and pattern of rare-earth elements and yttrium (REY), these studied convey that across-aquifer flow must exist in areas where the Rupelian Aquitard is missing.…”

Thermal effects on microbial composition and microbiologically induced corrosion and mineral precipitation affecting operation of a geothermal plant in a deep saline aquifer

“…However, due to lower diversity of fermentative bacteria compared with the SRB and low DOC content in fluids, hydrogen release from fermentation processes was probably not that relevant than chemical corrosion. Besides 16S rRNA gene sequences assigned to SRB, the isotopic signature of the residual sulfate (δ 34 S(SO 4 ) > 30 ‰, Möller et al 2008), a 10 % lower sulfate content in fluids produced from the cold well, and the detection of sulfide precipitates in topside facility filters (Fig. 4) clearly indicate metabolically active SRB.…”