Аннотация:According to monitoring of the atmospheric precipitation of Moscow a number of episodes is revealed, the content of hydrocarbonates in which repeatedly surpasses equilibrium level. Facts of their registration are linked to complex structure of precipitation which is caused by a different chemical composition of condensation nucleus. As a result on the underlying surface two groups of drops with acidity of the different nature are transferred. The actual acidity of raindrops could greatly exceed that is measured by the standard procedures for monitoring rainfall, which should be taken into account when calculating the so-called critical levels of acid loads on people and the environment