TRANSFORMATION OF CHEMICAL COMPOSITION OF ATMOSPHERIC PRECIPITATION BY THE CANOPY OF INDIGENOUS AND SECONDARY CONIFEROUS-DECIDUOUS FORESTS
The results of studying the precipitation transformation by the canopy in indigenous and secondary forests in the southern Sikhote-Alin are discussed. The studied precipitation water classes differ especially in anion composition. At deforested plots, SO <sup>2- </sup>4, NO <sup>- </sup>3, HCO <sup>- </sup>3, H <sup>+</sup> and Ca <sup>2+</sup> prevail in rain water samples. К+ increases in intermittent rain water what could be explained by the biota influence. In the waters, passing through the tree canopy, dissolved chemicals concentration is 7-30 times higher than in the rain water. Nevertheless, the water passing through the tree canopy remains ultra-fresh and, at the same time, enriched in TOC, K <sup>+</sup> and Ca <sup>2+</sup>. The water passing through the tree canopy sampled in young deciduous forests is found to be characterized by lower concentrations of main ions and higher acidity as compared to that from old forest communities. The most developed and dense crowns (canopy) of old forests create the conditions for the leaching of cations to neutralize acidic precipitation, and it leads to the increase in the hydro-carbonates in the water passing through the tree canopy. It is assumed that the protective properties of forest canopy will be kept until the latter provides the components binding H <sup>+</sup> greater than the strong acids anions entering from precipitation.