SOIL CHEMISTRY

Question 1

[] is generally more available in neutral to slightly alkaline soils, while [] is more available in acidic conditions.

Answer 1

1. Nitrogen (N) - nitrate, ammonium

Question 2

The rate of many chemical reactions, including those involving soil minerals and organic matter, is []. For instance, acid-base reactions are more favorable in certain pH ranges, affecting the transformation of nutrients.

Answer 2

pH-dependent

Question 3

comprises the inorganic components of soil, primarily derived from weathered rocks.

Answer 3

mineral matter

Question 4

The ability of soil to support loads is a critical factor in engineering. Different
soil types have varying load-bearing capacities, which must be assessed
during the design phase. For instance, [] can expand and contract, impacting structures, while [] may provide better drainage but lower load support.

Answer 4

Load-Bearing Capacity
clay soils
sandy soils

Question 5

Multifunctional Roles of Soil

Answer 5

1. Agricultural Productivity
2. Infrastructure Development
3. Ecological Balance

Question 6

Other Remediation Techniques
Additional methods for cleaning contaminated soils include:

Answer 6

i. Soil Washing: Physically removing contaminants through water or chemical solutions, washing away pollutants while leaving soil structure intact.
i. Thermal Treatment: Heating contaminated soil to volatilize and
destroy organic pollutants.
ii. Chemical Oxidation: Applying chemical agents to oxidize and break down contaminants.

Question 7

Heating contaminated soil to volatilize and
destroy organic pollutants.

Answer 7

thermal treatment

Question 8

Different microorganisms thrive at different pH levels. A [] pH is generally
favorable for a wide variety of microbes, whereas [] conditions may limit microbial diversity

Answer 8

neutral
highly acidic or alkaline

Question 9

Good aeration is essential for root respiration and microbial activity.
[] soils typically allow for better aeration compared to [] soils, which can become compacted and restrict air flow.

Answer 9

sandy
clay

Question 10

industrial wastes

Answer 10

i. Manufacturing Facilities: Factories may release heavy metals (e.g., lead, mercury), solvents, and other toxic compounds into the soil through spills, leaks, or improper
disposal.
ii. Mining Operations: Mining can lead to soil contamination from heavy metals and acidic runoff, affecting surrounding
ecosystems.
iii. Construction Sites: Construction debris, concrete, and hazardous materials can contribute to soil pollution.

Question 11

Elements like iron (Fe), manganese (Mn), and zinc (Zn) become more available in acidic soils but may become deficient in alkaline conditions.

Answer 11

4. Micronutrients:

Question 12

Applying chemical agents to oxidize and
break down contaminants.

Answer 12

chemical oxidation

Question 13

Physically removing contaminants through water or chemical solutions

Answer 13

Soil Washing

Question 14

a process that utilizes living organisms, primarily microorganisms, to degrade or transform contaminants in the soil. Key
aspects include:

Answer 14

bioremediation

Question 15

High fertilizer use can lead to the accumulation of salts in the soil, adversely affecting soil structure and fertility.

Answer 15

ii. Salinization:

Question 16

Composition of Soil

Answer 16

Mineral Matter
Organic Matter
Water and Air

Question 17

resulting from decomposed plant and animal materials, enriches the soil by improving fertility, moisture retention,
and microbial activity. It plays a vital role in nutrient cycling and enhances soil structure.

Answer 17

organic matter

Question 18

[]: [] particles ([] mm) that have high nutrient retention and water-holding capacity but can lead to drainage issues.

Answer 18

clay: Fine
<0.002

Question 19

The metabolic rates of bacteria and fungi are affected by pH, influencing their efficiency in breaking down organic matter and cycling nutrients. For example, some nitrogen-fixing bacteria prefer slightly acidic conditions.

Answer 19

Microbial Activity:

Question 20

Rain or irrigation can wash pesticides from fields into nearby soils and water bodies, leading to broader environmental impacts.

Answer 20

ii. Runoff:

Question 21

[] is a measure of the acidity or alkalinity of the soil, expressed on a logarithmic scale ranging from 0 to 14, where:

pH < 7:
pH = 7:
pH > 7:

Answer 21

Soil pH
acidic
neutral
alkaline

Question 22

Sources of Soil Contamination

Answer 22

industrial wastes
pesticides
fertilizer

Question 23

pesticides

Answer 23

i. Direct Application: Overuse or improper application of pesticides can result in residues remaining in the soil, affecting
microbial life and plant health
ii. Runoff: Rain or irrigation can wash pesticides from fields into nearby soils and water bodies, leading to broader environmental impacts.

Question 24

[] can lead to soil contamination from heavy metals and acidic runoff, affecting surrounding ecosystems.

Answer 24

ii. Mining Operations:

Question 25

Factories may release heavy metals (e.g., lead, mercury), solvents, and other toxic compounds into the soil through spills, leaks, or improper disposal.

Answer 25

i. Manufacturing Facilities:

Question 26

Soil contains [] in the spaces between soil particles, which is essential for plant growth and microbial activity. Air is also crucial, as it provides oxygen for roots and microorganisms. The balance of water and air in soil affects its physical properties and overall health.

Answer 26

water

Question 27

Construction debris, concrete, and hazardous materials can contribute to soil pollution.

Answer 27

iii. Construction Sites:

Question 28

Nitrogen and phosphorus from fertilizers can leach into the soil and waterways, causing eutrophication and altering soil chemistry.

Answer 28

i. Nutrient Runoff:

Question 29

[] particles have a larger surface area and can hold more nutrients than sand, making them more fertile. However, [] soils may require more frequent fertilization due to their lower nutrient-holding capacity

Answer 29

clay
sandy

Question 30

Certain nutrients, such as [] and [], become more soluble and available to plants in acidic conditions, while others, like [], can become less available due to precipitation in alkaline soils.

Answer 30

iron and manganese
phosphorus

Question 31

Contaminated soil is excavated and treated elsewhere, often requiring controlled conditions.

Answer 31

microbial action: ex situ

Question 32

Highly reactive and can form insoluble compounds, particularly in alkaline soils (pH > 7). Maintaining a slightly acidic to neutral pH (around 6-7) enhances [] availability.

Answer 32

2. Phosphorus (P)

Question 33

[]: [] particles ([] to [] mm) that provide good drainage and aeration but have low nutrient retention

Answer 33

sand: coarse
0.05 to 2

Question 34

Typically remains relatively available across a wide pH range, but extreme pH levels can affect its uptake due to changes in soil structure and microbial activity.

Answer 34

3. Potassium (K)

Question 35

Soil texture plays a critical role in determining how water moves through
the soil. [] soils drain quickly, which can be beneficial in preventing waterlogging but may require more frequent irrigation. [] soils retain water longer, which can lead to saturation and reduced aeration.

Answer 35

Drainage
Sandy
Clay

Question 36

[] refers to the gradual sinking of structures as the underlying soil compresses under load. Understanding the compressibility of different soil types helps engineers design foundations that minimize [] and ensure structural integrity

Answer 36

Settlement

Question 37

the use of plants to absorb, accumulate, and detoxify contaminants from the soil. The plants can uptake heavy metals and organic pollutants through their roots and either store them in their tissues or transform them into less harmful forms.

Answer 37

phytoremediation

Question 38

Treatment occurs on-site, allowing for natural conditions to be maintained

Answer 38

microbial action: in situ

Question 39

[]: [] particles ([] to [] mm) that hold moisture well and provide moderate fertility.

Answer 39

silt: medium
0.002 to 0.05

Question 40

fertilizers

Answer 40

i. Nutrient Runoff: Nitrogen and phosphorus from fertilizers can leach into the soil and waterways, causing eutrophication and altering soil chemistry.
ii. Salinization: High fertilizer use can lead to the accumulation of salts in the soil, adversely affecting soil structure and fertility.

Question 41

Overuse or improper application of pesticides can result in residues remaining in the soil, affecting microbial life and plant health

Answer 41

i. Direct Application: