Abstract
Review of biogeochemical processes studied in three Slovenian rivers (River Kamniška Bistrica, River Sava in Slovenia and River Idrijca), which represent an ideal natural laboratory for studying biogeochemical processes and anthropogenic impacts in catchments with high weathering capacity is presented. The River Kamniška Bistrica, the River Sava in Slovenia and the River Idrijca water chemistry is dominated by HCO3-, Ca2+ and Mg2+, and Ca2+/Mg2+ molar ratios indicate that calcite/dolomite weathering is the major source of ions to the river System. The Kamniška Bistrica River, the River Sava and River Idrijca and its tributaries are oversaturated with respect to calcite and dolomite. pCO2 concentrations were on average up to 25 times over atmospheric values for River Kamniška Bistrica, 20 times for River Sava and 13 times over atmospheric values for River Idrijca. δ13CDIC values ranged from -12.7 to -2.7 ‰ in River Kamniška Bistrica, from -12.7 to -6.3 ‰ in River Sava in Slovenia, from -10.8 to -6.6 ‰ in River Idrijca, respectively. In all investigated rivers we found out that carbonate dissolution is the most important biogeochemical process affecting carbon isotopes in the upstream portions of the catchment, while carbonate dissolution and organic matter degradation control carbon isotope signatures downstream, except for River Idrijca where both processes contribute equally from source to outflow to River Soča.
Highlights
Systematic studies of river water geochemistry provide important information on chemical weathering of bedrock/soil and natural and anthropogenic processes that may control the dissolved chemical loads (Schulte et al, 2011; Gibbs, 1972; Reeder et al, 1972; Huh et al, 1998; Négrel & Lachassagne, 2000)
The major solute composition of selected gravel-bed rivers was dominated by HCO3, Ca2+ and Mg2+
The major solute composition of the River Kamniška Bistrica is dominated by HCO3, Ca2+ and Mg2+
Summary
Systematic studies of river water geochemistry provide important information on chemical weathering of bedrock/soil and natural and anthropogenic processes that may control the dissolved chemical loads (Schulte et al, 2011; Gibbs, 1972; Reeder et al, 1972; Huh et al, 1998; Négrel & Lachassagne, 2000). Freshwaters cover small fraction of the Earth’s surface area, inland freshwater ecosystems ( lakes, rivers and reservoirs) have rarely been considered as potentially important quantitative components of the carbon cycle at either global or regional scales (Cole et al, 2007). Rivers are the major pathways for the transport of carbon (C) from the continents top the oceans. Global river carbon fluxes are estimated to be 0.4 Pg C/year of organic C (evenly divided between particulate and dissolved phases) and 0.4 Pg C/ year for dissolved inorganic carbon (DIC). Bulk fluxes are small components of the global C cycle but are significant compared to net oceanic uptake of anthropogenic CO2 (Sarmiento & Sundquist, 1992)
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