Acid Rain and Its Effects on the Lakes of Fars County in Iran

One of the main environmental issue these days is acid rain and its effects on the human and environment. Acid rain effects are more dominant in countries such as United States, Canada, and Europe due to acidic nature of soils in some parts of their lands as well as heavy pollution resulted from vast industrial activities which are conducted through these countries. Contrary to these facts, Iran situation regarding acid rain is totally different and in spite of high pollution in cities and industrial areas, the water of lakes and streams are not acidic. Data collected in this research show that the pH and alkalinity of the lake water and soils are almost high. Some of the lakes in Fars County are dried and the rest are not in normal situation. Lakes of Barmshoor, Droodzan, and Haftbarm have pH around 7.93 -8.07 and alkalinity around 186 to 220 mg/L CaCO3. The soils around the lakes have pH in the range of 7.69-7.89 and alkalinity 208-235 mg/L CaCO3. Therefore both the soil and the water have high alkaline buffer capacity to resist acid rain because; most part of the Fars County consist of calcite, dolomite and some alkaline salts. Pollution load indexes for Al, Zn and Cu for both lake water and related soils are close to one (1.063-1.54) which means no considerable metal pollutions are created by acid rain in Fars County. In fact, high pH and alkalinity of the water and soil make metal salts mostly insoluble and limit the availability of the free metals. The pH changes of rain water show gradual increase of pH during raining. If the sample of rain water is left alone, its pH decreases by residence time.