Effect of acid rain on the soil microorganisms
1996
Sutharat Vitchaivuttiwong | Sirintornthep Towprayoon (King Mongkut's Institute of Technology Thonburi, Bangkok (Thailand). School of Energy and Materials)
Effect of simulated acid rain on soil microorganisms was studied using laboratory soil column. The soil was filled with 45 cm height in the column of 15 cm in diameter and 50 cm height. The soil columns were treated with simulated acid rain (sulfuric acid) at pH 5, 4 and 3. Two levels of acid application were set up in this experiment. The first level was 20 ml/day in representation of low amount of precipitation while the second level was 70 ml/day representation of higher amount of precipitation. At appropriate time interval, the soil sample were collected at 6, 18 and 38 cm depth from the top of column and was analyzed the moisture content, pH, total count of bacteria, fungi, actinomycetes, ammonifying bacteria, nitrogen fixing bacteria (Azotobacter) and nitrite oxidizer microorganisms. Bacteria, fungi, actinomycetes and Azotobacter were enumerated by total plate counts technique while ammonifying bacteria and nitrite oxidizer were enumerated by most probable number technique. In the soil column treated with 70 ml/day of simulated acid rain, the significant impacts were observed at the column with high acidic applications pH 4 an 3. The total amount of bacteria, actinomycetes and ammonifying bacteria were clearly reduced when compared to the control, particulary at the soil level of 6 cm where high H+ were accumulated. The concentration of H+ applied to the soil column that caused the effect to microorganisms in this study was 7.5*10*[-6) meq/100 g of soil. It is noticed that there was no pH change during the acid rain treatment which may be due to the high buffering capacity of the forest soil.
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