ABSTRACT. – Acid precipitation influence on the quality of surface water. Research chemical composition of precipitation and air monitoring concentrations of oxides and sulphates acidification in the years 1990-2008 showed the presence of acid rain and the Republic of Moldova. pH value of samples of water collected from rainfall varied in limits from 2.65 to 10.35. During the years 1990-1998 the percentage of water samples acid increased continuously. In the years 1999-2002 the water samples were mostly neutral and a further increase in acid samples was detected during 2002-2008. It was found that the Stratus and Stratocumulus clouds, which absorb pollutants from the layer of atmosphere below the clouds, are less acidic precipitation than Cumulonimbus clouds, which make contact with the upper atmospheric layers and perhaps incorporating pollutants brought by air masses from the front. Content analysis of ions and pH investigated, depending on the wind we see that the rainfall fell in descending air masses are more acidic compared with the masses of air upward. Analysis of water samples collected from surface waters in the territory of the Republic have shown that the quality of surface water is not practical influenced of acid rainfall due to the chemical composition of soil water bed, which has an increased content of carbonates. Moldova is affected by the phenomenon of acid rain and the determining factor is the transfer of transboundary acid substances.
Key words: acid rain, atmosphere, transboundary transfer, ecological impact.