The Correlation Between Acid Material in Atmosphere and Precipitation Acidity

The characteristic of precipitation during 1991～1999 in Zhengzhou was studied.The result indicated that ① The annually averaged pH value in Zhengzhou was above 5\^6 showing the occurrence of acid rain in many years in Zhengzhou although it does not belong to Acid Rain Area.② Vitriolic pollution is main form of precipitation in Zhengzhou.There is close correlation between pH value in precipitation and SO\-2 concentration in atmosphere,but not strong correlation between pH value and SO 4\+\{2-\} concentration in precipitation.③ There is also preferable correlation between NO\+-\-3 concentration in precipitation and NO\-x in atmosphere.