Nitrogen Compounds in the Soil of the Continental Margins of the European Russian Arctic

The specific features in the distribution of organic and mineral nitrogen compounds in marsh and tundra soils of the European Russian Arctic (coastal areas of the Barents and White Seas) were analyzed. Total nitrogen was determined by gas chromatography (CHNS-O elemental analyzer), and inorganic nitrogen, by photometry. The composition of hydrolyzable amino acids was analyzed by liquid chromatography on ion exchange resins. Mineral compounds accounted for an insignificant part of the total soil nitrogen; its major part (to 97% of the total content) was represented by organic substances (Nоᵣg). The Nоᵣg varied within a wide range in both marsh (0.3–15.8 g/kg) and tundra soils (5–20 g/kg in the peat horizons and 0.3–2 g/kg in the mineral horizons). The content of N-[Formula: see text] varied from 5 to 20 mg/kg in marsh soils and from 30 to 200 mg/kg in tundra soils. In marsh soils, the content of nitrate nitrogen was 0.2–4.6 mg/kg in the upper horizons. Marsh soils were characterized by the accumulation of Nоᵣg either on the surface or in the middle part of the profile in the presence of humus-accumulative horizons buried under recent marine sediments. The accumulation of Nоᵣg and N-[Formula: see text] was observed above the permafrost in the peat-gley soil and in the permafrost in the oligotrophic peat soil. The content of hydrolyzable amino acids in the soils of different geneses was 0.6–8 g/kg, which corresponded to 30–60% of the soil organic nitrogen and 2–12% of the soil organic carbon. Distribution patterns of the amino acid nitrogen and organic nitrogen in the soil profiles were similar. The qualitative composition of amino compounds was relatively uniform, and the ratios of most of them were close. The shares of arginine, histidine, phenylalanine, tyrosine, and isoleucine were less than 4% each; of lysine, valine, proline, serine, and threonine, 5 to 7%; and of alanine and leucine, 10–12%. The share of glycine increased downward the profile from 12 to 20%, and the shares of aspartic and glutamic acids decreased from 11 to 6%. In marsh soils, Nоᵣg, N-[Formula: see text], and nitrogen of most amino acids correlated (r = 0.6–0.9) with the clay content and nonsilicate iron forms. The tightest correlations were observed between the dithionite-soluble iron and the nitrogen of threonine and histidine.