A LONG-TERM MONITORING OF ACID RAIN AT YOKOSUKA CITY

Abstract

In Japan, the natural environment has been harmed by air pollution such as acid rain. In recent years, the problem has become more and more serious as the acidities of rainfall and snowfall decrease. Acid rain is generally defined as rain, snow and fog with a concentration of hydrogen ions (pH) less than 5. 6. The large causes for acid rain are the pollutants of NOx and Sox generated from waste gas and factory exhausts due to the human activities. Both pollutants are converted into the ions of NO_3^- and SO₄^2- in the atmosphere, and these ions are dissolved in rainfall as HNO₃ and H₂SO₄, respectively. That is, the acid rain is rainfall with very high concentrations of HNO₃ and H₂SO₄. In this investigation, based on the measurement of pH value and the results of chemical microanalyses, some conclusions are formed about the real condition and ion-composition of acid rain at Yokosuka city, Kanagawa. The authors have carried out the monitoring on rainfalls since May 1991 at Yokosuka city near the Tokyo Bay. It has been observed that the rainfalls at this city have very high concentrations of NO_3^- and SO₄^2-