Chemical transformation of Kamchatka soils after input of products of volcanic eruption

It has been revealed that changes in the chemical composition of soils after the input of volcanic ash under conditions of a cold humid climate depend on granulometric and lithogeochemical compositions of eruption products, the ways and forms of the input of chemical elements to soil, the period of the year, and weather conditions at ash falls. The lithogeochemical composition of ash mainly determines the type of change in the total composition of soils. Variations in the contents of mobile forms of elements depend mainly on the period of year and meteorological conditions during ash falls. Most mobile compounds (99.3%) of many elements are transported to soil upon ash falls not as components of ash particles, but in gas- and watersoluble forms directly from the dispersion medium of the volcanic aerosol. The following regularities were revealed in soils at a distance of 25 km from the centers of eruption: (i) the increase in the total contents of elements and the removal of their mobile forms in winter and (ii) the accumulation of mobile compounds, a drop in their total compounds, and soil acidification with a significant (about 1.5 times) decrease in the degree of base saturation of soils in summer.