S–O–C isotopic picture of sulphate–methane–carbonate system in freshwater lakes from Poland. A review

Abstract

Microbial oxidation of organic compounds (including methane), in freshwater sediments, may result in precipitation of carbonates, which may become an important geochemical archive of paleoenvironmental variations. Most probably low δ 13 C value in calcite in eutrophic systems results from an advanced oxidation of organic compounds in turbulent or/and sulphate-rich conditions. Likewise, high δ 13 C value in calcite from organic-rich sediments may evidence low redox potential of the freshwater system. Oxidation of methane and organic matter results in significant isotope effects in sulphates dissolved in water. Therefore, to better understand the origin of carbon isotope signal in carbonates, concentration and stable isotope measurements in dissolved sulphate (water column), bubble methane and calcite (freshwater sediments) have been carried out in 24 lakes, 2 ponds and 4 rivers in Poland. The highest concentration of sulphate has been detected in rivers (85.47 SO 4 2− mg/l) and an artificial lake (70.30 SO 4 2− mg/l) located in the extremely SO 4 2− -polluted region called the "Black Triangle". The lowest concentration of sulphate is found in dystrophic and mountain lakes (from 0.5 SO 4 2− to about 3 mg/l). The lowest δ 34 S(SO 4 2− ) and δ 18 O(SO 4 2− ) values occur in unpolluted lakes in eastern Poland (−0.94 and 1.38‰, respectively). The highest S and O isotopic ratios are found in a polluted lake in western Poland (δ 14 S(SO 4 2 )=12.95‰) and in a dystrophic lake in eastern Poland (δ 18 O(SO 2 4 ) = 16.15‰) respectively. It is proposed that δ 34 SO 2− 4 and ( 18 O(SO 4 2− ) values in lakes represent a good tool to assess and quantify anthropogenic impact by acid precipitation and to monitor variations in the trophic state and redox processes controlled by biodegradation of organic compounds in sediments and water column. In general, increasing depth (up to 12 m) of the water column is associated with decreasing trend the δ 13 C(CH 4 ) value from about -35 to about -78‰. However, δ 13 C value in sedimentary calcite (δ 13 C vary from -10 to 0.5‰) shows opposite trends as compared to the corresponding methane. This is probably due to redox processes and distribution of heavy isotopes between methane and calcite. Likewise, turbulent water (river) show high δ 13 C value in methane and low δ 13 C value in calcite-this is probably due to an enhanced oxidation of methane producing 13 C-depleted CO 2 . In contrast to clean lakes, it is observed that an increase of the δ 13 C(CH 4 ) value occurs with increasing depth of the water column in a strongly SO 4 2− -contaminated lake. This is probably due to a loss of biological buffering potential of the lake accompanied by an active oxidation of methane precursors.

Sulphur isotope mass balance of dissolved sulphate ion in a freshwater dam reservoir

“…Significant seasonal variations in d 34 S(SO 4 2-) value are mainly due to biological activity, as it has been pointed out by Mandernack et al (2000). Numerous studies addressed the isotope biogeochemistry of sulphate ion in freshwater environments, like peat-bogs waters (Mandernack et al 2000;Jezierski et al 2006), groundwaters (Moncaster et al 2000;Jezierski et al 2006), lakes (Jędrysek 2005), and rivers (Cortecci et al 2002;Trembaczowski et al 2004). However, there is no literature on diurnal variations of d 34 S(SO 4 2-) value.…”

“…The d 34 S values of agrochemical pollutants can be relatively high and may reach 8% (Cortecci et al 2002) or 10% (Moncaster et al 2000), which corresponds to the value calculated by means of the isotopic mass balance for spring (10.06%). Nevertheless, the third source of sulphate can originate not only from agrochemicals but also from the coniferous forests (Jędrysek 2005), which are also present in the direct catchment of the reservoir. Namely, the coniferous vegetation may add about 1 mg/dm 3 of the allochtonous biogenic sulphate (Jędrysek 2005) enriched in heavy sulphur isotopes due to oxidation of organic sulphur to sulphate ion (Jędrysek et al 2002).…”

“…sulphate minerals dissolution, oxidation of pyrite (Cortecci et al 2002), oxidation of organic sulphur by microorganisms (Mandernack et al 2000), or anthropogenic origin, e.g. acid rains (Jędrysek 2005), industry, sewage and agrochemical contamination (Moncaster et al 2000;Cortecci et al 2002). The main sink of sulphate ion dissolved in freshwater systems is biosphere due to dissimilatory or assimilatory sulphate reduction (Mitchell et al 1998).…”

Variability of sulfur speciation in sediments from Sulejów,Turawa and Siemianówka dam reservoirs (Poland)

“…The sulfur isotopic composition of the sulfate(VI) ion is determined by the sources of its origin and redox reactions, which are predominantly controlled by the biosphere and which in consequence lead to changes in its concentration in the water column and in the sediment [13][14][15]. The process that modi es the isotopic composition of the sulfate(VI) ion to the greatest extent is bacterial sulfate(VI) reduction which causes sulfate(VI) to be enriched in the heavy sulfur isotope ( S), because sulfate(VI) reducing bacteria prefer the light sulfur isotopes ( S) [16].…”

Spectrophotometric Characterisation of Surface Lakewater Samples: Implications for the Quantification of Nitrate and the Properties of Dissolved Organic Matter

“…[1][2][3][4] Additionally they play an important role, together with nitrite, in water photochemistry and photobiology concerning both the transformation of dissolved molecules [5][6][7][8][9][10][11][12] plus the connected possible production of harmful compounds, 13,14 and the penetration of radiation inside the water column. [15][16][17] DOM also plays a crucial role in defining the water solubility and bioavailability of toxic metal species and complexes, and of organic pollutants.…”