How acid rain affects stonework The picture on the left was taken in 1908 The picture on the right was taken in 1968
2 Aluminum activation in soil Exchangeable Hydrogen is the main source of H+ at ph 6 and above Below ph 6 Aluminum is the main source of H+ due to dissociation of Al from clay minerals. Aluminum becomes more soluble at lower pH's A|3++H20---A(OH)++H Al(OH)+++H2O--->Al(OH)2++H+ Al(OH)++H20---> Al(OH)3+H+
Exchangeable Hydrogen is the main source of H+ at pH 6 and above. Below pH 6 Aluminum is the main source of H+ due to dissociation of Al from clay minerals. Aluminum becomes more soluble at lower pH’s Al3+ + H20 ----> Al(OH)++ + H+ Al(OH)++ + H2O ---> Al(OH)2 + + H+ Al(OH)2 + + H20 ---> Al(OH)3 + H+ 2. Aluminum activation in soil
(=) The types of soil acidity 1. Active acidi Active Acidity -The activity of hydrogen ion in the aqueous phase of a soil expressed as a ph value. 土壤减的级 等级 pH值 超强砖 极强度 35~44 强性 4.5~4 张性 55-64 甲性 6s-7 7b~85 强碱性 86-95 极强碱注
（二）The types of soil acidity 1．Active acidity Active Acidity –The activity of hydrogen ion in the aqueous phase of a soil expressed as a pH value
2. Soil potential acidity (1) Strong acidity in soil Colloid-A13+=Colloid+A13+ A3++3H2O Al(OH)3+ 3H (2) Acidity and weak acidity in soil Al(OH 2+ +HOH A1(OH)2++H+ Al(OH 2+ + HOH Al(OH)3++H+ Or: Colloid-H+—H
2． Soil potential acidity (1) Strong acidity in soil Colloid-Al3+ = Colloid + Al3+ Al3+ + 3H2O Al（OH)3 + 3H+ (2) Acidity and weak acidity in soil Al（OH）2+ + HOH Al（OH）2+ + H+ Al（OH）2+ + HOH Al（OH）3+ + H+ Or: Colloid-H+ H+
3. Soil exchangeable acidit Exchangeable acidity- The aluminum and hydrogen that can be replaced from an acid soil by an unbuffered salt solution such as KCI or NaCl(cmol (+)/kg)
3. Soil exchangeable acidity • Exchangeable acidity- The aluminum and hydrogen that can be replaced from an acid soil by an unbuffered salt solution such as KCl or NaCl. (cmol（＋）/kg）