Sources and Export Fluxes of Inorganic and Organic Carbon and Nutrient Species From the Seasonally Ice-Covered Yukon River

• Main Authors: Guo, Laodong, Cai, Yihua, Belzile, Claude, McDonald, Robie W.
• Format: Text
• Language: unknown
• Published: The Aquila Digital Community 2012
• Subjects: dissolved organic matter; particulate organic matter; dissolved inorganic carbon; nutrients; river ice formation; export fluxes; yukon river; arctic river; Biogeochemistry; Earth Sciences; Physical Sciences and Mathematics; Arctic; Yukon; Yukon river
• Online Access: https://aquila.usm.edu/fac_pubs/230; http://lynx.lib.usm.edu/login?URL=https://link.springer.com/content/pdf/10.1007%2Fs10533-010-9545-z.pdf

Climate and environmental changes are having profound impacts on Arctic river basins, but the biogeochemical response remains poorly understood. To examine the effect of ice formation on temporal variations in composition and fluxes of carbon and nutrient species, monthly water and particulate samples collected from the lower Yukon River between July 2004 and September 2005 were measured for concentrations of organic and inorganic C, N, and P, dissolved silicate (Si(OH)4), and stable isotope composition (δD and δ18O). All organic carbon and nutrient species had the highest concentration during spring freshet and the lowest during the winter season under the ice, indicating dominant sources from snowmelt and flushing of soils in the drainage basin. In contrast, inorganic species such as dissolved inorganic carbon (DIC) and Si(OH)4 had the highest concentrations in winter and the lowest during spring freshet, suggesting dilution during snowmelt and sources from groundwater and leaching/weathering of mineral layer. The contrasting relation with discharge between organic, such as dissolved organic carbon (DOC), and inorganic, such as DIC and Si(OH)4, indicates hydrological control of solute concentration but different sources and transport mechanisms for organic and inorganic carbon and nutrient species. Concentration of DOC also shows an inter-annual variability with higher DOC in 2005 (higher stream flow) than 2004 (lower stream flow). Average inorganic N/P molar ratio was 110 ± A 124, with up to 442 under the ice and 38-70 during the ice-open season. While dissolved organic matter had a higher C/N ratio under the ice (45-62), the particulate C/N ratio was lower during winter (21-26) and spring freshet (19). Apparent fractionation factors of C, N, P, Si and δD and δ18O between ice and river water varied considerably, with high values for inorganic species such as DIC and Si(OH)4 (45 and 9550, respectively) but lower values for DOC (4.7). River ice formation may result in fractionation of inorganic and organic ...