Evaluation of the Sulfate Dynamics in Groundwater by Means of Environmental Isotopes

Abstract

Elevated sulfate concentrations and their heterogeneous distribution in the drinking water catchment area Torgau-Mockritz (Germany) were investigated by means of multiple isotope signatures such as 834S, delta18O-H2O, deltaD, tritium, and 85K5r. delta34S values of the groundwater sulfate vary between -19...+ 37 per thousand CDT. No simple correlation exists between sulfate concentrations and delta34S. Superimposition of different sulfur sources and mobilization processes combined with a complicated groundwater movement create a complex distribution pattern. The oxidation of reduced sedimentary sulfur has to be regarded as a main source of dissolved sulfate at least regionally. Tritium and 14C data revealed that old groundwater can be excluded as source for high sulfate contents. Correlated temporal variations in the concentrations of tritium and sulfate are observed in deeper sampling positions. Highly variable delta18O and 8D, as detected in parts of the catchment area, indicate local influences of surface water infiltration into the aquifer. The spatial distribution of isotope signatures enables the identification of zones with descending younger water or hindered groundwater movement and hence provides useful hints for flow modeling.

Sulphur cycling in the drinking water catchment area of Torgau–Mockritz (Germany): insights from hydrochemical and stable isotope investigations

“…Investigations of the hydrodynamics in the catchment area by Trettin et al (2002) showed that there is no evidence for an infiltration of such. Hence, the highly mineralized brines can be ruled out as a source of sulphate.…”

“…The two oxygen sources show a large difference in their isotopic compositions. Whereas atmospheric oxygen has a υ 18 O value of 23Ð5‰ (Kroopnick and Craig, 1972), the oxygen isotopic composition of water is typically negative, in our case showing a mean value of approximately 9‰ (Trettin et al, 2002). Taylor and Wheeler (1994) suggested the following equation for calculating the relative proportions of oxygen derived from water and air:…”

“…This is partly due to the low groundwater table leaving most of the dump body in unsaturated conditions where the gypsum solution is only of minor importance. On the other hand, the existing groundwater flow dynamics exclude the transport of the mobilized sulphate into the water intakes of the catchment area (Trettin et al, 2002).…”

“…The coupled investigation of υ 34 S and υ 18 O does not always enable the definite assignment of the sulphate samples to a certain source or process. Owing to the dynamic flow regime in the entire catchment area (Trettin et al, 2002), mixing of dissolved groundwater sulphate of different origins is a very widespread process. Mixing processes can significantly influence the isotopic composition of the sulphate.…”

Identification of groundwater recharge sources and processes in a heterogeneous alluvial aquifer: results from multi‐level monitoring of hydrochemistry and environmental isotopes in a riverside agricultural area in Korea

“…An integrated use of hydrogeological, hydrochemical, and isotopic data is helpful in identifying the sources and mechanisms of groundwater recharge in a heterogeneous alluvial aquifer (Schürch and Vuataz, 2000). Environmental isotopes (υ 18 O, υ 2 H, and 3 H) have been particularly successful in elucidating the source and recharge characteristics of alluvial groundwater (Guglielmi et al, 1998;Harvey and Sibray, 2001;Böhnke et al, 2002;Trettin et al, 2002;Zhang et al, 2005).…”