Block 2

Question 1

List chem reactions in soil liquid phase

Answer 1

• Acid base
• Hydrolysis
• Complexation
• Redox

Question 2

pH

Answer 2

Measures hydrogen ion concentration. Log scale for aqueous solutions.

pOH also exists, measure of hydroxide ion concentration.

Question 3

What form do metals exist as within acidic vs alkaline environments

Answer 3

Metals exist as free ions at a pH <7 such as Pb2+ or CrO42-

Metals exist as insoluble precipitates or minerals at a pH >7 such as Pb(OH)2

Question 4

Hydrolysis

Answer 4

Ion/compound reacts chemically with water and a new chemical species is formed (aka broken down by reacting with water). Involves the addition of a water molecule to the reactant.

The rate of this reaction depends on pH such that an increase in pH (alkaline) increases the hydrolysis of metals and makes metals insoluble.

Question 5

Complexation (aka chelation)

Answer 5

Increases mobility of metals in soil. But reduces mobility of organic molecules.

Question 6

List processes in aerobic environment

Answer 6

• Biodeg of organic contaminants
• Nitrification
• Precipitation of dissolved Fe2+ and Mn2+
• Sulfur or sulfide oxidation

Question 7

List processes in anaerobic environment

Answer 7

• Biodeg or organic contam
• Denitrification
• Reductive dissolution of iron and mang oxide minerals
• Sulfate reduction
• Methanogenesis
• Biotrans of redox-sensitive toxic metals