南京农业大学：《土壤学》（双语版） Chapter 9 Soil acid-base and redox reaction

Chapter 9 Soil acid-base and redox reaction 中土壤酸碱度分布图 盐基能和度% P H 5=5 20-60 7.5-8,5

Chapter 9 Soil acid-base and redox reaction

Chapter 9 Soil acid-base and redox reaction Section 1 The formation of soil acid-base The acid-base reaction of soil The acid-base reaction of soil is change in soil pH. soil oH is probably the single most important chemica charecteristic of a soil. The knowledge of ph is needed to understand important chemical processes such as ion mobility, precipitation and dissolution equilibria, and oxidation-reduction equilibria. a knowledge of ph is also needed to understand nutrient availability to plants and the negative response of many plant species to soil acidity The soil ph value in China is about 4.5-8.5

Chapter 9 Soil acid-base and redox reaction Section 1 The formation of soil acid-base The acid-base reaction of soil The acid-base reaction of soil is change in soil pH. Soil pH is probably the single most important chemical charecteristic of a soil. The knowledge of pH is needed to understand important chemical processes such as ion mobility, precipitation and dissolution equilibria, and oxidation-reduction equilibria. A knowledge of pH is also needed to understand nutrient availability to plants and the negative response of many plant species to soil acidity. The soil pH value in China is about 4.5-8.5

中土壤酸碱度分布图 盐基饱和度 P H 盐饱和度 ac-10c 20-60 7,5-8.5 1 62一33 4-6-1

、 Soil acidity (-) The cause of soil acidity 1. Climatic factor 2. Biological factor 3. Fertilizer application and irrigation 1. The source of hydrogen ions. (1 Water dissociation (2) Carbon dioxide (3) Organic acid (4 Inorganic acid(inorganic fertilizer) (5 Acid rain

一、Soil acidity （一）The cause of soil acidity 1． Climatic factor 2．Biological factor 3．Fertilizer application and irrigation 1.The source of hydrogen ions （1）Water dissociation （2）Carbon dioxide （3）Organic acid （4）Inorganic acid (inorganic fertilizer) （5） Acid rain

Acid rain Acid rain is caused by the burning of fossil fuels Burning oil, gas and coal in Acid Rain Formation power stations releases Sulfuric Dioxide(SO2) into Acid the atmosphere Burning oil and gasoline in motor vehicles puts nitrogen 50 oxides(NOx) into the atmosphere These gases mix with water droplets in the atmosphere 田田田 creating weak solutions of nitric and sulfuric acids When precipitation occurs these solutions fall as acid rain

Acid rain ▪ Acid rain is caused by the burning of fossil fuels. ▪ Burning oil, gas and coal in power stations releases Sulfuric Dioxide (SO2 ) into the atmosphere. ▪ Burning oil and gasoline in motor vehicles puts nitrogen oxides (NOX) into the atmosphere. ▪ These gases mix with water droplets in the atmosphere creating weak solutions of nitric and sulfuric acids. ▪ When precipitation occurs these solutions fall as acid rain

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）