Ecological problems of land use and soil pollution of natural, arable and fallow lands of the Selenga river delta

In the summer of 2017–2018 we researched the landscape-geochemical and socio-geographical aspects in the delta of the Selenga river (southeast coast of Lake Baikal). The structure of land use is dominated by hayfields and pastures. The study area is important for the development of meat and dairy farming in Buryatia. The cultivated crops here are cereals, legumes, cold-resistant silage crops, potatoes and other vegetables. In the Selenga river delta various types of soils have been formed: fluvisols, folic-podburs, and gray metamorphic and folic-gray soils. The fertile soils of the high floodplain with chernozems and phaeozems are used for arable land. The agricultural land of terraces with gray and folic-gray soils is used for pasture. The soils of the low floodplain of waterlogged meadows are included in agricultural circulation. We revealed that the soils of most agricultural lands have a satisfactory agronomic quality. The upper horizons of gray soils under the forest and chernozems under the steppe have high humus concentrations in their natural state. In constantly used agricultural soils humus content is reduced. In fallow lands, its concentrations are restored. The water pH level of soils is mostly neutral. It is revealed that the soils of the Selenga delta are mainly light soils. It was revealed that gray soils after forest clearing and using them for arable land, quickly degrade and lose their fertility. Soils of the steppes show good resistance to agricultural use. Soil deposits and arable land, previously located under forest, are infertile and require introduction of nitrogen and potassium fertilizers. Soils recently introduced for agricultural use require phosphorus and potassium fertilizers. Chernozems and gray soil of natural landscapes, as well as anthrosols, previously located under steppe, are in good and satisfactory agronomic condition. Near the settlement of Kabansk we established high concentrations of some heavy metals in alluvial soils, exceeding the MPC. An increased content of oil products, phosphates, fluorides and heavy metals in the waters of the Selenga river was revealed. The coastal waters of Lake Baikal at the mouth of the Selenga river still meet sanitary and hygienic requirements. Alluvial soils of the Selenga river delta acts as a geochemical barrier to the migration of pollutants into Lake Baikal.