Effect of acid deposition on soil acidification and metal mobilisation

Simulated acid rain treatments of pH 5.6, 4.0 and 2.5 in the laboratory produced marked acidification and Al and Zn mobilisation in columns of an homogenised incipient podsolic soil. Exposure of monoliths of the same soil and an acid brown earth to ambient levels of acid deposition in the U.K. for 3 a, resulted in soil acidification at higher rainfall and slightly contaminated sites, whilst the drier but more contaminated sites exhibited a more variable response. Changes in DTPA-extractable Zn did not conform to any obvious pattern, although at 5 of the 6 sites the acid brown earth monoliths underwent a decrease in Zn concentration.