Composition of the Water-Soluble Soil Fraction on the Barents Sea Coast: Organic Carbon and Nitrogen, Low-Molecular Weight Components

Abstract

Water extracts from soils of the Barents Sea coast (the Khaipudyr Bay) were analyzed for the contents of organic carbon and total nitrogen by the method of high-temperature catalytic oxidation with non-dispersive IR registration; the contents of low-molecular-weight acids, carbohydrates, and alcohols were determined by gas chromatography and gas chromatography–mass-spectrometry. The mass fraction of inorganic carbon $$\left( {{\text{HCO}}_{3}^{ - }} \right)$$ was measured potentiometrically, and the content of inorganic nitrogen (N–$${\text{NO}}_{3}^{ - },$$ N–$${\text{NH}}_{4}^{ + }$$) was determined by photometry. In marsh soils (Tidalic Fluvisols (Arenic or Loamic, Epiprotosalic)), = 0.1–0.8, $${\omega }{{\left( {{{{\text{N}}}_{{{\text{org}}}}}} \right)}_{{{{{\text{H}}}_{{\text{2}}}}{\text{O}}}}}$$ = 0.01–0.05 g/kg, $${\omega }{{\left( {{{{\text{N}}}_{{{\text{org}}}}}} \right)}_{{{{{\text{H}}}_{{\text{2}}}}{\text{O}}}}}$$ = + 0.01, and $${{\left( {{\text{C/N}}} \right)}_{{{{{\text{H}}}_{{\text{2}}}}{\text{O}}}}}$$ = 7–21. The content of individual components does not exceed 20 mg/kg, including carbohydrates (50–90%), acids (10–50%), and alcohols (<3%). In peat horizons of tundra soils (Cryic Histosols and Histic Cryosols), = 4–10, $${\omega }{{\left( {{{{\text{N}}}_{{{\text{org}}}}}} \right)}_{{{{{\text{H}}}_{{\text{2}}}}{\text{O}}}}}$$ ~ 0.2 g/kg, and $${{\left( {{\text{C/N}}} \right)}_{{{{{\text{H}}}_{{\text{2}}}}{\text{O}}}}}$$ = 25–56. Litter and peat horizons accumulate both individual humus components and total dissolved organic carbon. The total weight of the identified substances is 200–300 mg/kg, 80–90% of them are carbohydrates, 10–20% are acids, and 0–9% are alcohols. The accumulation of and (N–$${\text{NH}}_{4}^{ + }{{)}_{{{{{\text{H}}}_{2}}{\text{O}}}}}$$ takes place above the permafrost table. It is argued that the ratios of organic forms of carbon and nitrogen in soil water extracts and the content of low-molecular weight organic compounds in soils can be used as indicators of pedogenic processes in the Far North.