Effects of acid precipitation on organic and inorganic chemistry of leachate from an organic-rich forest soil

The general purpose of this study was to determine the role of simulated acid rain in mobilizing soil organic constitutes and selected organochlorine compounds from an organic-rich soil.; Soil samples from the Newman Lake watershed of Washington State was treated with simulated "acid rain" at pH 3.20 and control at 5.7. The soil column study was carried out in the laboratory over a 10-day period during which the soil received a total of 121 mm of simulated rainfall. The simulated acid rain treatment leached less dissolved organic carbon and more nonhydrolyzable cations relative to the control treatment. Organic molecules of higher molecular weight and size were present in the leachate of soils treated with acid rain relative to the control.; To examine the effect of acid precipitation on mobility of selected organochlorine pesticides, DDT, methoxychlor and lindane, soils were spiked with these compounds at a rate of 0.038 mg kg{dollar}sp{lcub}-1{rcub}{dollar} prior to column packing. Acid rain reduced the amount of DDT and methoxychlor in soil leachate and had no effect on the amount of lindane. The amount of insecticide in the soil leachate of the acid treated soil was a function of the compound's polarity and the amount of dissolved organic carbon.; The influence of the anion composition of simulated acid rain on leachate chemistry was investigated in a second test. Soils were leached with HNO{dollar}sb3{dollar} and H{dollar}sb2{dollar}SO{dollar}sb4{dollar} simulated acid rain at pH 3.20 and compared to a control at pH 5.7. Nitric acid rain leached more cations compared to H{dollar}sb2{dollar}SO{dollar}sb4{dollar} and both acid treatments leached more cations than the control solutions. The amount of dissolved organic carbon in the soil leachate increased according to treatment as follows: HNO{dollar}sb3{dollar} {dollar}<{dollar} H{dollar}sb2{dollar}SO{dollar}sb4{dollar} {dollar}<{dollar} control. The same relationship among treatments was seen for the DDT and methoxychlor levels in the soil leachate. The amount of lindane in the soil leachate did not change significantly with treatments.