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Abstract: Carbon cycling was investigated monthly (July, August, September, October, November, March and May) from July 2023 to May 2024 in the Radovna stream originating from the permanent Lipnik spring in the Julian Alps, Slovenia using isotopic composition of carbon in dissolved inorganic carbon (δ13CDIC) and particulate organic carbon (δ13CPOC). The investigated catchment is composed of massive coarse - crystal dolomite and limestone. Total alkalinity ranged from 2.2 to 2.7mM and is characteristic for carbonate pristine environments. In-situ parameters e.g. dissolved oxygen ranged from 11.0 to 12.0mg/L, pH from 7.9 to 8.1 and specific electrical conductivity from 275 to 318μS/cm, respectively. The values of dissolved oxygen reflect that the water system is well oxygenated. CO2 presented a source of carbon to the atmosphere during all investigated months. Oversaturation with CO2 is 1.01 to 4.1 times of atmospheric value. δ13CDICranged from -11.8 to -9.7‰. This indicates that dissolved inorganic carbon under different discharge conditions mainly originates from the dissolution of carbonates (from 50.3 % to 57.3%), followed by the degradation of organic matter (from 42.8% to 49.7%). Equilibration with atmospheric CO₂ has a negligible impact, ranging from 0.01% to 0.11%. δ13CPOC in river water indicate sources such as plant debris, with δ13CPOC of -29.4‰, and highly degraded soil organic matter, with δ13CPOC of -24.9‰. The δ13CDIC and δ13CPOC values are typical for a forest stream flowing over a limestone substrate. Strong statistical negative significant correlation was obtained between electrical conductivity and water temperature, mass of total suspended solids (mTSS) and pH.
Keywords: total alkalinity, stable isotopes, carbon, pCO2, headwater stream, Julian Alps
Published in DiRROS: 23.12.2025; Views: 769; Downloads: 88
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Abstract: None declared.Conflict of interestHigh-resolution carbon isotope ratio (δ13C) measurements of tree rings have the potential to provide seasonal environmental information. However, due to the complexity of the wood formation processes, the reliability of this method for intra-seasonal reconstruction of growing conditions remains unclear. We, therefore, investigated the intra-annual variation of δ13C in tree rings of three conifer species (Pinus sylvestris, Picea abies, Abies alba) across sites from the Swiss Alps to assess their response to seasonal variation of soil water potential (SWP) and vapour pressure deficit (VPD). Intra-annual δ13C values at a resolution of 10 points per year were assessed using laser-ablation isotope-ratio mass spectrometry. Seasonal δ13C patterns were analyzed for synchronicity across trees and species, and their correlation with on-site environmental variables was used to determine the driving factors of δ13C, to reconstruct growing season dynamics, and to estimate timings of the growth dynamics and allocation of carbon to xylem formation. The δ13C patterns showed high synchronicity between species, with characteristic maxima in wet and dry years occurring in the middle of the ring and at the end of the ring, respectively. Seasonal δ13C variations reliably reflected atmospheric dryness. Higher than normal soil dryness hindered integration of further fresh assimilates into the xylem, thus allowing the identification of species- and site-specific threshold conditions that disrupt wood formation. The δ13C of Scots pine shows the strongest correlations with VPD and SWP, making it an excellent indicator of environmental variability. Silver fir appears to integrate carbon into xylem structural material over a longer season than the other conifers, whilst Norway spruce shows more plastic site-specific responses to environmental conditions. In conclusion, we identify how atmospheric and soil drought jointly impact tree growth and intra-annual δ13C patterns across conifer species, offering valuable insights for climate reconstructions and wider applications on forest dynamics.
Keywords: water availability, annual growth, laser ablation, tree-ring isotopes, carbon isotopes
Published in DiRROS: 01.10.2025; Views: 392; Downloads: 211
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Abstract: Bottled natural mineral waters from an andesitic aquifer in Slovenia are enriched in magnesium (1.1 g/l), sulphate (2.2 g/l) and dissolved inorganic carbon (204 g/l). We analysed major ions, trace elements, tritium activity, 14 C, d18 OH2O , d2 HH2O, d13 CDIC, gas composition and noble gases in six wells. In addition, 87 Sr/ /86 Sr, d34 SSO4 and d11 B were analysed here for the first time. Stable isotopes with d18 O = -11.97 to -10.30% and d2 H = -77.3 to -63.8 confirm meteoric origin. CO2 degassing is evident at three wells, causing the oxygen shift of about -1.3%. Tritium activity was detectable only in the shallowest well, where the freshwater component was dated to the 1960s. d13 CDIC in five waters is -1.78 to ? 1.33%, typical of carbonate dissolution. Radiocarbon is low, 1.03–5.16 pMC. Chemical correction with bicarbonate concentration and d13 C correction methods gave best mean residence times, slightly longer than previously published. Sulphate has d34 S 26.6–28.9% and d18 O 8.9–11.1% due to dissolution of evaporites in carbonate rocks. Boron at concentrations of 1.2–6.1 mg/l has two origins: d11 B = 11.3–16.4% from hydrothermal alteration and d11 B = 26.6–31.7% from carbonate dissolution. Strontium at concentrations of 0.5–22.0 mg/l has 87 Sr/ /86 Sr, indicating three sources: 0.7106 for Miocene clastic rocks, 0.7082 for Triassic carbonates and 0.7070 for Lower Oligocene andesitic rocks. CO 2 represents the majority of the dissolved ([ 98.84 vol%) and separated gas ([ 95.23 vol%). Methane is only found in two wells with a max. of 0.30 vol%. All waters show excess helium and 16–97% of mantlederived helium. Since all show subsurface degassing, the paleo-infiltration temperature could not be calculated.
Keywords: natural tracers, carbon, sulphur, strontium and boron isotopes, noble gases
Published in DiRROS: 24.03.2022; Views: 2328; Downloads: 639
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