Investigating the Provenance and Seasonal Variations in Sulphate Sulphur and Oxygen Isotopes of Central Roztocze River Water,SE Poland

The isotope composition of sulphur and oxygen were measured in water collected from the Central Roztocze (SE of Poland) rivers. The research focused mainly on the upper section of the Wieprz River, its confluences and springs and on two confluences of the Tanew River. The results proved that there are two sources of sulphate dissolved in water: the Cretaceous aquifer and soil within the catchment's area. Seasonal variation of the sulphate concentration together with sulphur and oxygen isotope composition was observed. The isotope composition of sulphate varied in water collected at the different locations of the same river. They are similar for sulphates in springs and rivers. The isotope composition of sulphate varied in water collected at the different locations of the same river. The δ³⁴S values of sulphates in the Wieprz River are the lowest (negative) in lower part of the river. It shows that the contribution of sulphate from spring water increases downstream. The low sulphate content and high δ³⁴S and δ¹⁸O value in sulphates was found downstream from dams. It may be the result of deficiency of oxygen in mud and the reduction in bacteria activity. The seasonal variations of the oxygen isotope composition in sulphate are significant in sulphates collected from rivers and from springs. They are caused by seasonal variations of the δ¹⁸O in water stored in the soil. The narrow range of the δ¹⁸O values for the sulphates extracted from springs at the same time means that the main source of sulphate in spring water are oxidising processes using the same source of oxygen in every location. The high sulphate content combined with the high δ³⁴S values of the sulphates in springs suggest, that the sulphates from Cretaceous aquifer were mixed with sulphates dissolved from the soil.     

Differentiation between adsorbed and precipitated sulphate in soils and at micro-sites of soil aggregates by sulphur K-edge XANES

To investigate the potential of synchrotron‐based X‐ray Absorption Near‐Edge Structure spectroscopy (XANES) at the sulphur (S) K‐edge for a discrimination of adsorbed and precipitated sulphate in soils and soil particles, XANES spectra of ionic sulphate compounds and Al/Fe hydroxy sulphate minerals were compared with spectra of SO₄^2? adsorbed to ferrihydrite, goethite, haematite, gibbsite or allophane. Ionic sulphate and hydroxy sulphate precipitates had broader white‐lines (WL) at 2482.5 eV (full width at half maximum (FWHM) of edge‐normalized spectra, 2.4–4.2 eV; Al hydroxy sulphates, 3.0 eV) than SO₄^2? adsorbed to Al/Fe oxyhydroxides or allophane (FWHM, 1.8–2.4 eV). The ratio of the white‐line (WL) height to the height of the post‐edge feature at 2499 eV (WL/PEF) was larger for SO₄^2? adsorbed to Al/Fe oxyhydroxides or allophane (8.1–11.9) than for Al/Fe hydroxy sulphates and ionic sulphates (3.9–5.7). The WL/PEF ratio of edge‐normalized S K‐edge XANES spectra can be used to distinguish adsorbed from precipitated SO₄^2? in soils and also at microsites of soil particles. The contribution of adsorbed and precipitated SO₄^2? to the total SO₄^2? pool can be roughly quantified. Adsorbed ester sulphate may result in overestimation of precipitated SO₄^2?. The spectra of most soils could be fitted by linear combination fitting (LCF), yielding a similar partitioning between adsorbed and precipitated SO₄^2? as an evaluation of the WL/PEF ratio. The SO₄^2? pool of German forest soils on silicate parent material in most cases was strongly dominated by adsorbed SO₄^2?; however, in three German forest soils subject to elevated atmospheric S deposition, a considerable portion of the SO₄^2? pool was precipitated SO₄^2?, most likely Al hydroxy sulphate. The same is true for Nicaraguan Eutric and Vitric Andosols subject to high volcanogenic S input. In the subsoil of the Vitric Andosol, adsorbed SO₄^2? and Al hydroxy sulphate coexist on a micron scale.     

Sulfur Isotope Variations in Atmospheric Sulfur Oxides, Particulate Matter and Deposits Collected at Kyushu Island, Japan

Atmospheric sulfur oxides, particulate matter and deposits (wet and dry deposits) were collected from July 1998 to June 1999 at Kyushu Island, Japan. The isotopic composition of sulfur (δ³⁴S) was measured to identify the source of sulfur in the samples. The monthly δ³⁴S values were always low in the order of the sulfur oxides, sulfate in particulate matter and deposits. The δ³⁴S values of the sulfur oxides ranged from ?2.7 ‰ to ?0.4 ‰ and were close to those of fossil fuels used in Japan. The δ³⁴S values of sulfate in the particulate matter and deposits correlated with seasalt contribution, so that the δ³⁴Snss value was calculated for non-seasalt sulfate. The δ³⁴Snss values of sulfate in the particulate matter and deposits trended higher in winter than summer, suggesting the possibility of isotopic fractionation during chemical transformation (SO₂ to SO₄ ^2?) and of contribution of sulfate derived from sulfur sources with higher δ³⁴S values.     

sulphur isotope composition of stream water,moss and humus from eight arctic catchments in the Kola Peninsula region (NW Russia,N Finland,NE Norway)

In summer 1994, stream water, moss and humus samples were collected for sulphur isotopic analysis from eight catchments located in the western Kola Peninsula region, where several industrial centres emit high loads of SO₂ and other elements to the atmosphere. Three potential sources of sulphur and their isotopic signatures were identified: (1) marine (δ ³⁴S+20 to +21‰ CDT), (2) anthropogenic emissions (<+10‰), and (3) geogenic (variableδ ³⁴S, mostly <+10‰). Averaged per catchment, the sulphur isotopic composition varies between +6.0 and +16.3‰ for stream water sulphate, +6.0 and +8.4‰ for moss sulphur, and +5.2 and +12.2‰ for humus sulphur. Theδ ³⁴S composition of stream water from the more remote catchments is quite variable, reflecting several natural (geogenic) sources, but it becomes restricted to the range +8 to +10‰ near the pollution sources. A plot ofδ ³⁴S vs. 1:SO₄ in stream water suggests that sulphate originating from the smelters has aδ ³⁴S value ≈+9.5‰, and is a dominant source. Sulphur isotope values for moss and humus are consistent with the deduced composition for the emitted sulphur, though for humus a component of geogenic sulphur incorporated via vegetation uptake may play a role. Further isotopic characterisation of atmospheric emissions, together with environmental samples, is needed to better understand sulphur sources and sinks in the area.     

Evaluation of the Impacts of Marine Salts and Asian Dust on the Forested Yakushima Island Ecosystem, a World Natural Heritage Site in Japan

To elucidate the influence of airborne materials on the ecosystem of Japan??s Yakushima Island, we determined the elemental compositions and Sr and Nd isotope ratios in streamwater, soils, vegetation, and rocks. Streamwater had high Na and Cl contents, low Ca and HCO₃ contents, and Na/Cl and Mg/Cl ratios close to those of seawater, but it had low pH (5.4 to 7.1), a higher Ca/Cl ratio than seawater, and distinct ⁸⁷Sr/⁸⁶Sr ratios that depended on the bedrock type. The proportions of rain-derived cations in streamwater, estimated by assuming that Cl was derived from sea salt aerosols, averaged 81?% for Na, 83?% for Mg, 36?% for K, 32?% for Ca, and 33?% for Sr. The Sr value was comparable to the 28?% estimated by comparing Sr isotope ratios between rain and granite bedrock. The soils are depleted in Ca, Na, P, and Sr compared with the parent materials. At Yotsuse in the northwestern side, plants and the soil pool have ⁸⁷Sr/⁸⁶Sr ratios similar to that of rainwater with a high sea salt component. In contrast, the Sr and Nd isotope ratios of soil minerals in the A and B horizons approach those of silicate minerals in northern China??s loess soils. The soil Ca and P depletion results largely from chemical weathering of plagioclase and of small amounts of apatite and calcite in granitic rocks. This suggests that Yakushima??s ecosystem is affected by large amounts of acidic precipitation with a high sea salt component, which leaches Ca and its proxy (Sr) from bedrock into streams, and by Asian dust-derived apatite, which is an important source of P in base cation-depleted soils.     

Elemental concentrations in fresh snowfall across a regional transect in the northeastern U.S.: Apparent sources and contribution to acidity

Fresh snowfall was collected on the surface of 8 lakes across a 350 km west-east transect from northeastern New York state to the coast of Maine after a single storm. In addition, every snowfall event during the winter of 1993 was collected on a single lake near the center of the transect. Across the transect, midwestern sources appear to dominate Pb and Cd concentrations, while Sb appears to be derived from midwestern sources as well as local and/or industrial East Coast sources. In all samples, the highest Na, Cl and Mg concentrations reflect a marine influence, but at some transect sites roadspray aerosol appears to contribute to Na and Cl concentrations. The regional pattern of Ca, K, Mn and Sr concentrations and Mn/Sr ratios indicate that woodsmoke may be an important winter source of these elements at some sites. In all samples, H⁺ is strongly correlated with NO₃ ^? (R² = 0.97) and mean NO₃ ^?/SO₄ ^2? molar ratios of 6.4 for transect samples, and 4.7 for temporal samples, are higher than mean NO₃ ^?/SO₄ ^2? reported for other precipitation studies in the same region. The contribution of NO₃ ^? to the snowpack greatly exceeds that of SO₄ ^2?, and may be a major source of acidity in aquatic ecosystems during snowmelt.     

Räumliche Variabilität der Phosphorgehalte im Oberboden landwirtschaftlich genutzter Flächen in kleinen Einzugsgebieten

Spatial variability of Phosphorus contents in topsoils of two small catchments under agricultural use The spatial variability of total phosphorus (P_t) contents was investigated in two small agriculturally used catchments in Saxony/Germany. The mean P_t concentration was 982 mg kg^–1, with 80 % of values between 560 and 1530 mg kg^–1. The largest P_t contents were found at the tops and foots of slope, and the smallest at the middle slope positions. At the scale of slopes (microscale) the spatial variability was caused by the relief and soil properties, whereas at the scale of catchments, agricultural management had the largest influence. These differences must be considered for the modeling of diffuse P inputs to surface waters.     

Effects of reduced atmospheric deposition on soil solution chemistry and elemental contents of spruce needles in NE—Bavaria,Germany

The decrease in anthropogenic deposition, namely SO₄^2— and SO₂, in European forest ecosystems during the last 20 years has raised questions concerning the recovery of forest ecosystems. The aim of this study was to evaluate if the long term data of element concentrations at the Fichtelgebirge (NE‐Bavaria, Germany) monitoring site indicates a relationship between the nutrient content of needles and the state of soil solution acidity. The soil at the site is very acidic and has relatively small pools of exchangeable Ca and Mg. The trees show medium to severe nutrient deficiency symptoms such as needle loss and needle yellowing. The Ca and Mg concentrations in throughfall decreased significantly during the last 12 years parallel to the significant decline in the throughfall of H⁺ and SO₄^2— concentrations. Soil solution concentrations of SO₄^2—, Ca and Mg generally decreased while the pH value remained stable. Aluminum concentrations decreased slightly, but only at a depth of 90 cm. Simultaneously a decrease in the molar Ca/Al and Mg/Al ratios in the soil solution was observed. Ca and Mg contents in the spruce needles decreased, emphasizing the relevance of soil solution changes for tree nutrition. The reasons for the delay in ecosystem recovery are due to a combination of the following two factors: (1) the continued high concentrations of NO₃^— and SO₄^2— in the soil solution leading to high Al concentrations and low pH values and, (2) the decreased rates of Ca and Mg deposition cause a correlated decrease in the concentration of Ca and Mg in the soil solution, since little Ca and Mg is present in the soil's exchangeable cation pools. It is our conclusion that detrimental soil conditions with respect to Mg and Ca nutrition as well as to Al stress are not easily reversed by the decreasing deposition of H⁺ and SO₄^2—. Thus, forest management is still confronted with the necessity of frequent liming to counteract the nutrient depletion in soils and subsequent nutrient deficiencies in trees.     

Sequential Leaching of Volcanic Soil to Determine Plant-Available Cations and the Provence of Soil Minerals Using Sr Isotopes

Sequential leaching experiments using H₂O, H₂O₂, NH₄Cl, and HCl were performed on surface soils on an andesite substrate at four sites in the Kawakami mountainous area, central Japan. The solutions extracted from the dehydrated soil by H₂O, H₂O₂, and NH₄Cl have relatively constant ratios with respect to Ca, Mg, and Sr, while they have variable ⁸⁷Sr/⁸⁶Sr ratios depending on the site. The elemental ratios and Sr isotopes in the extracted solution are different from those of the soil minerals but identical to those of the soil solution and the plants. Sr isotopic data indicate that the residues after extraction from fine-grained minerals by NH₄Cl and HCl are a mixture of acid-resistant minerals derived from bedrock and from arid areas in China. We suggest that there is a vital exchange of Sr and other cations between plants and the soil pool of exchangeable cations through the soil solution, while soil minerals, except chlorite, do not participate in the exchange reaction.     

Inorganic sulphate extraction from SO2-impacted Andosols

Sulphate sorption on to the surface of short‐range ordered minerals and precipitation of Al‐hydroxy sulphate contribute to the acid neutralizing capacity of soils. The correct measurement of total inorganic sulphate is thus essential in soils that are accumulating SO₄^2– anions. We extracted SO₄^2– by various solutions, namely 0.005 m Ca(NO₃)₂, 0.016 m KH₂PO₄, 0.5 m NH₄F and 0.2 m acidic NH₄‐oxalate (pH 3), from Vitric and Eutric Andosols exposed to prolonged deposition of acid and SO₂ from an active volcano (Masaya, Nicaragua). We attributed sulphate extractable by KH₂PO₄ (20–3030 mg kg^?1) to anion‐exchangeable SO₄^2–, which was much smaller than NH₄F‐ and oxalate‐extractable SO₄^2– (400–9680 and 410–10 480 mg kg^?1, respectively). Our results suggest the occurrence of a sparingly soluble Al‐hydroxy‐mineral phase extractable by both NH₄F and oxalate. The formation of Al‐hydroxy minerals would result from the combination of enhanced weathering caused by strong acid loading and simultaneous occurrence of large SO₄^2– concentrations in soil solution. Oxalate extracted slightly more inorganic SO₄^2– than did NH₄F, this additional amount of SO₄^2– correlating strongly with oxalate‐extractable Si and Fe contents. Preferential occlusion of SO₄^2– by short‐range ordered minerals, especially ferrihydrite, explains this behaviour. If we exclude the contribution of occluded sulphate then oxalate and NH₄F mobilize similar amounts of SO₄^2– and are believed to mobilize all of the inorganic SO₄^2– pool.     

Sulphate Mobilization and Pore Water Chemistry in Relation to Groundwater Hydrology and Summer Drought in two Conifer Swamps on the Canadian Shield

Variations in sulphate (SO₄ ^2-) concentration of porewater and net SO₄ ^2- mobilization were related to differences in water level fluctuations during wet and dry summers in two conifer swamps located in catchments which differed in till depth and seasonality of groundwater flow. Sulphate depletion at the surface and in 20 cm porewater coincided with anoxia and occurred mainly during the summer when water levels were near the peat surface and water flow rates were low in both catchments. There was an inverse relationship between net SO₄ ^2- mobilization and water level elevation relative to the peat surface, explaining variation in SO₄ ^2- dynamics between the swamps during summer drought periods. Aeration of peat to 40 cm and a large net SO₄ ^2- mobilization (10–70 mg SO₄ ^2- m^-2 d^-1) occurred during a dry summer in which the water level dropped to 60 cm below the surface in the swamp receiving ephemeral groundwater inputs from shallow tills within the catchment. This resulted in high SO₄ ^2- concentrations in the surface water and porewater (30–50 mg L^-1), and elevated SO₄ ^2- concentrations remained through the fall and winter. In contrast, within the swamp located in the catchment with greater till depth (> 1 m), continuous groundwater inputs maintained surface saturation during the dry summer, and SO₄ ^2- mobilization and concentrations of SO₄ ^2- in the pore water during the following fall did not increase. Susceptibility to large water table drawdown and mobilization of accumulated SO₄ ^2- is influenced by the occurrence of ephemeral vs. continuous groundwater inputs to valley swamps during dry summer periods in the Canadian Shield landscape. This study reveals that extrapolation of results of SO₄ ^2- cycling from one wetland to another requires knowledge of the hydrogeology of the catchment in which the wetlands are located.     

Recovery of acidified catchments in the extremely polluted Krusne hory Mountains,Czech Republic

Runoff and atmospheric chemistry in the Krusne hory Mts. have changed significantly from 1978 to 1994. Forest die-back related deforestation resulted in decreased dry deposition of SO₂ and changes in streamwater chemical composition. Atmospheric sulphur (S) deposition decreased from extremely high values of 66.6 kg S ha^?1 year^?1, in the early 1980s to 35.5 kg S ha^?1 year^?1 in 1994. Decreasing S input is reflected in decrease of streamwater sulphate (SO₄ ^2?) concentrations, which decreased from 1560 μeq l^?1 to 1164 μeq l^?1. Runoff export of S was 53 kg S ha^?1 year^?1 in 1993, S is not retained in the catchments. Nitrogen (N) budget indicates accumulation in the catchment, which is attributed to forest regrowth.     

Sulfur isotope dynamics in a high-elevation catchment,West Glacier lake,Wyoming

Stable isotopes of S are used in conjunction with dissolved SO ₄ ^2? concentrations to evaluate the utility ofδ ³⁴S ratios in tracing contributions of bedrock-derived S to SO ₄ ^2? in runoff. Water samples were collected over the annual hydrograph from two tributaries in the West Glacier Lake, Wyoming, catchment. Concentrations of SO ₄ ^2? ranged from 12.6 to 43.0 Μeq L^?1;δ ³⁴S ratios ranged from ?1.8‰ to +4.9‰ Theδ ³⁴S value of atmospherically derived SO ₄ ^2? is about +5.6%c.; four samples of pyrite from the bedrock hadδ ³⁴S ratios that ranged from +0.7 to +4.1‰ Concentrations of SO ₄ ^2? were inversely related toδ ³⁴S and discharge. The data for the tributary with the higher SO ₄ ^2? concentrations were reasonably consistent with mixing between atmospheric S and S from a bedrock source with aδ ³⁴S ratio of about ?4.5‰. The difference from the measured bedrock values presumably indicates that S isotopes in the bedrock pyrite are heterogeneously distributed. The data from the tributary with lower SO ₄ ^2? concentrations did not follow a two-component mixing line. Deviation from a two-component mixing line is most likely caused by preferential elution of SO ₄ ^2? from the snowpack during the early stages of snowmelt, although microbially mediated fractionation of S isotopes in the soil zone also may cause the deviation from the mixing line. Sulfur isotopes are useful in identifying whether or not there is a substantial contribution of bedrock S to runoff, but quantifying that contribution is problematic.     

Nitrogen and Sulfate Export from High Elevation Catchments of the Sierra Nevada,California

Based on studies of high-elevation, Sierra Nevada catchments during the period from 1983 through 1996, we describe temporal variations in the concentrations of NO₃ ^- and SO₄ ^2- in surface waters. During snowmelt, some catchments had a pattern of NO₃ ^- increase to a plateau between the start of snowmelt and some weeks before runoff peaked, and a decline as runoff increased to its maximum. In other catchments, NO₃ ^- concentrations peaked during the autumn and winter. Long-term trends in surface water chemistry were evident in only two catchments: an increase in SO₄ ^2- concentrations in surface waters of the Ruby Lake basin, and a lowering of annual maxima and minima of NO₃ ^- concentrations at Emerald Lake. From October 1987 through April 1994, SO₄ ^2- concentrations increased from about 6 µeq L^-1 to about 12 µeq L^-1 in Ruby Lake, and in Emerald Lake, NO₃ ^- maxima declined by 25-50 %.     

The Importance of Sr Isotopic Compositions as an Indicator of Acid-Soluble Minerals in Arid Soils in China

Aeolian particles originating from arid areas in China, termed Kosa, are considered to be a major source of non-sea-salt Ca, a dominant base cation, in acid precipitation in northeastern Asia. We extracted evaporite minerals (halite, gypsum, and carbonate) from the surface soil collected at eight desert and loess areas in northern China with water and acetic acid. Most ⁸⁷Sr/⁸⁶Sr ratios of the extracted fractions fell in a restricted range (0.7115 ± 0.0015) and differed from those of bulk soils and acid-insoluble minerals (0.712–0.717). The selective dissolution of the soil carbonates in the atmosphere is consistent with two facts: (1) their ⁸⁷Sr/⁸⁶Sr ratios are close to the maximum ⁸⁷Sr/⁸⁶Sr ratios of spring precipitation in Japan, when Kosa activity is marked; and (2) their mole ratios of Mg/Ca (0.15) and Sr/Ca (0.001) are almost identical to those of precipitation in China and Japan when Kosa activity is marked. The ⁸⁷Sr/⁸⁶Sr, Mg/Ca, and Sr/Ca ratios in the acid-soluble components can be used as indexes of Kosa aerosols in the precipitation of the northwestern Pacific.     

Sulphur gas emissions in the Boreal Forest: The West Whitecourt case study V. Stable sulphur isotopes

Sulphur (S) gas emissions from the West Whitecourt Gas Plant were shown to have δ³⁴S value near +22%. while the δ³⁴S value for pre-industrial soil and ground water was found to be near 0‰ This isotopic ‘leverage’ provided a means of assessing the fate of S-gas emissions and the movement of S-compounds among the four main compartments of the forest ecosystem: air, vegetation, soil, and water. Several high volume sampling techniques were used to relate the δ³⁴S values of atmospheric S-compounds to wind direction at the intensive experimental site 1.5 km cast of the gas plant. These techniques included field testing of a wind directionally controlled high volume sampling array. Winds from the direction of the gas plant carried particulates and SO₂ which were considerably more enriched in δ³⁴S than for other wind directions. The stable S isotopic compositions of lodgepole × jack pine needles at sampling locations around the S-gas emission source were consistent with the wind rose summary for the area. Height dependences were found for the δ³⁴S values of atmospheric particulates and for pine foliage. Needles in the upper canopy frequently had δ³⁴S values 5 to 10‰ higher than S-gas emission from the gas plant, thereby suggesting an isotopically selective metabolic process. δ³⁴S values of total S-compounds in surface waters increased with increasing organic S content, approaching a limit near +22‰, suggesting that both parameters were mutually influenced by the input of S-gas emissions to the forest ecosystem. Limited soil profile δ³⁴S data indicated that S of industrial origin penetrated the soil to at least 1 m depth in exposed, dry areas lacking biological cover while in a light forest cover, penetration to 60 cm had not yet occurred. Stable S isotopes were found to be a practical environmental tracer of industrial S in the forest ecosystem in Alberta.     

Snow contamination by heavy metals and sulphur in Cracow agglomeration (Southern Poland)

The concentration of heavy metals (Cd, Pb, Zn, Fe), light metals (Ca, Mg), sulphate (SO _inf4 ^sup2? ) and pH in snow samples collected along 35 km transect from a large steel mill was determined. The concentration of heavy metals, light metals and sulphate decreased with the increasing distance from the emittors, whereas the snow acidity increased. Significant differences in the concentration of pollutants in snow between forest and open stands, between deciduous and mixed forests as well as with the date of snow collection were found.     

Soil properties that affect sulphate adsorption by palexerults in western and central Spain

Abstract

The beneficial action of gypsum in suppressing aluminum (Al) toxicity in Bt horizons of Ultisols is related to the self‐liming effect of the adsorption of sulphate (SO₄ ^2‐) ion. The relationship between SO₄ ^2‐ adsorption by gypsum‐amended soils and some components and properties of 38 surface and subsurface horizons from seven Palexerults in western and central Spain was analyzed. The highest correlations of maximal SO₄ ^2‐ adsorption as determined from langmuir isotherms were with clay, free iron oxyhydroxides (Fe_dcb), and exchangeable Al contents, and pH. Liming reduces SO₄ ²’ ion adsorption; consequently, the joint application of limestone and gypsum to the surface of these soils results in increased availability of gypsum for the subsurface horizons.     

Effect of K2SO4 concentration on extractability and isotope signature (δ13C and δ15N) of soil C and N fractions

Determination of the labile soil carbon (C) and nitrogen (N) fractions and measurement of their isotopic signatures (δ¹³C and δ¹⁵N) has been used widely for characterizing soil C and N transformations. However, methodological questions and comparison of results of different authors have not been fully solved. We studied concentrations and δ¹³C and δ¹⁵N of salt‐extractable organic carbon (SEOC), inorganic (N–NH₄⁺ and N–NO₃^?) and organic nitrogen (SEON) and salt‐extractable microbial C (SEMC) and N (SEMN) in 0.05 and 0.5 m K₂SO₄ extracts from a range of soils in Russia. Despite differences in acidity, organic matter and N content and C and N availability in the studied soils, we found consistent patterns of effects of K₂SO₄ concentration on C and N extractability. Organic C and N were extracted 1.6–5.5 times more effectively with 0.5 m K₂SO₄ than with 0.05 m K₂SO₄. Extra SEOC extractability with greater K₂SO₄ concentrations did not depend on soil properties within a wide range of pH and organic matter concentrations, but the effect was more pronounced in the most acidic and organic‐rich mountain Umbrisols. Extractable microbial C was not affected by K₂SO₄ concentrations, while SEMN was greater when extracted with 0.5 m K₂SO₄. We demonstrate that the δ¹³C and δ¹⁵N values of extractable non‐microbial and microbial C and N are not affected by K₂SO₄ concentrations, but use of a small concentration of extract (0.05 m K₂SO₄) gives more consistent isotopic results than a larger concentration (0.5 m ).