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[MIS01-18] Geochemical features of elements migration and speciation in soil waters of the Valday Upland
Keywords:soil waters, mobility of elements, Valday Upland, lysimetric water
Soil waters are an integral part of the hydrochemical cycle and a main agent of the migration of elements in the aeration zone. The unsaturated soil zone (aeration zone) plays an important role in many aspects of biogeochemistry, including infiltration, accumulation of moisture in the soil, evaporation, absorption of plant water, replenishment of groundwater, runoff and leaching of elements. The chemical composition of soil waters is formed during the filtration of atmospheric precipitation through the soil.
The study area in the Valday Hills is constrained to the northwestern part of the Russian plate. In the mild continental excessively humid climate with short indulgent summers, sod-podzolic soils were formed on the moraine, fluvioglacial, and alluvial sediments. The sod−podzol horizon is underlain by sand and sandy loam.
On the territory of the study, 2 experimental sites were selected to study the formation of soil waters. The first section was located 20 km from the town of Valday, in the catchment area of Gusinoe lake; the second in the city of Valday near the Valdayskoe lake. The experimental sites were equipped with sediment collectors and lysimetric installations for sampling atmospheric precipitation and soil water.
To determine the mobile forms of trace elements, samples of soil genetic horizons were selected for an extraction experiment and experiment with soil columns. Extraction of the sample with deionized water makes it possible to transfer easily soluble forms of trace elements into solution, as well as soluble complex compounds with organic and inorganic ligands. Exchangeable forms are obtained by extraction of soil samples with ammonium acetate buffer.
The main characteristics and genesis of the studied soils determine the differences in the distribution of bulk contents and concentrations of mobile element forms in soil profile. The content of mobile forms is determined by the total content of trace elements in soils. Therefore, the content of mobile forms of chalcophile elements (Zn, Cu) is higher than that of siderophile elements (Ni, Co).
The acidity of the lysimetric water depends on the content of organic matter in the soil. The pH of the soil solution controls mainly the behavior of sulfates, Zn and Ni. Some elements, such as P, N, Fe, Zn, Cu, Co, and Mn, are actively consumed by living organisms and plants at vegetation. Pb and Cd dominantly migrate in the soil water with organic complexes.
In the lysimetric waters of podzolic soils, mineralization increases with increasing depth and from the spring season to the autumn. In summer and autumn, the pH increases with depth, which is due to a decrease in the content of organic acids. Statistical methods have established that Fe, Co, Mn migrate in soil waters as part of organic complexes regardless of the change of season.
Soil waters of borozems are characterized by a neutral reaction and a high content of HCO3-ions and Ca, Si, Zn. Significant differences in the formation of lysimetric waters of brown soils and podzols are introduced by Ca and Mg, in which the main intake of these elements occurs. Leaching of easily soluble and exchangeable forms of Zn prevails in the experiment with soil extracts, and the most active migration is characteristic of Cu. The mobility of easily soluble and exchangeable forms of trace elements prevails over the mobility of macronutrients. The most active migrants in the experiment with soil columns and extracts in brown and podzolic soils are: Cu, Zn, Ca.
The study area in the Valday Hills is constrained to the northwestern part of the Russian plate. In the mild continental excessively humid climate with short indulgent summers, sod-podzolic soils were formed on the moraine, fluvioglacial, and alluvial sediments. The sod−podzol horizon is underlain by sand and sandy loam.
On the territory of the study, 2 experimental sites were selected to study the formation of soil waters. The first section was located 20 km from the town of Valday, in the catchment area of Gusinoe lake; the second in the city of Valday near the Valdayskoe lake. The experimental sites were equipped with sediment collectors and lysimetric installations for sampling atmospheric precipitation and soil water.
To determine the mobile forms of trace elements, samples of soil genetic horizons were selected for an extraction experiment and experiment with soil columns. Extraction of the sample with deionized water makes it possible to transfer easily soluble forms of trace elements into solution, as well as soluble complex compounds with organic and inorganic ligands. Exchangeable forms are obtained by extraction of soil samples with ammonium acetate buffer.
The main characteristics and genesis of the studied soils determine the differences in the distribution of bulk contents and concentrations of mobile element forms in soil profile. The content of mobile forms is determined by the total content of trace elements in soils. Therefore, the content of mobile forms of chalcophile elements (Zn, Cu) is higher than that of siderophile elements (Ni, Co).
The acidity of the lysimetric water depends on the content of organic matter in the soil. The pH of the soil solution controls mainly the behavior of sulfates, Zn and Ni. Some elements, such as P, N, Fe, Zn, Cu, Co, and Mn, are actively consumed by living organisms and plants at vegetation. Pb and Cd dominantly migrate in the soil water with organic complexes.
In the lysimetric waters of podzolic soils, mineralization increases with increasing depth and from the spring season to the autumn. In summer and autumn, the pH increases with depth, which is due to a decrease in the content of organic acids. Statistical methods have established that Fe, Co, Mn migrate in soil waters as part of organic complexes regardless of the change of season.
Soil waters of borozems are characterized by a neutral reaction and a high content of HCO3-ions and Ca, Si, Zn. Significant differences in the formation of lysimetric waters of brown soils and podzols are introduced by Ca and Mg, in which the main intake of these elements occurs. Leaching of easily soluble and exchangeable forms of Zn prevails in the experiment with soil extracts, and the most active migration is characteristic of Cu. The mobility of easily soluble and exchangeable forms of trace elements prevails over the mobility of macronutrients. The most active migrants in the experiment with soil columns and extracts in brown and podzolic soils are: Cu, Zn, Ca.