Soil Pollution and Mitigation Pt. 2

What are Soluble Pollutants?

Pollutants that can dissolve is soil moisture and can leach into deer soil layers and eventually groundwater.

What are particulate pollutants?

Pollutants that bind to sediment and soil, rather than dissolving in water. They're transported through erosion.

What are brownfields?

Abandoned industrial urban sites that contains heavily polluted soil, typically heavy metals and organic chemicals.

How are agricultural and suburban soils polluted?

Extensive use of fertilizers for crops or lawns, leading to phosphate-saturated soils.

How does pollution change as it moves away from the source?

It's concentration decreases until it reaches groundwater, where it moves with the groundwater's flow.

What are the four remediation techniques for soil pollution?

Total or partial excavation and disposal, In Situ and on site processing, retention and restriction of contamination, and monitoring or natural weakening of contaminated areas.

What is total or partial excavation and disposal ?

The removal of contaminated soil, and either treating it or disposing it as hazardous waste.

How is in situ processing done?

Contaminated soil is treated directly underground without being removed.

How is on site processing done?

Contaminated soil is removed and treated and reused.

How is retention and restriction of contaminated soil done?

The contaminated soil is isolated with caps, liners, or underground barriers.

What are some newer methods of soil remediation?

Electrokinetic remediation, phytoremediation, remediation with nanoparticles, and biochar.

What is electrokinetic remediation?

An in-situ cleanup method that applies a low electrical current through contaminated soil, moving pollutants toward electrodes where they can be collected and removed.

What is phytoremediation?

Using living plants to absorb pollutants.

What is remediation with nanoparticles?

It uses small particles into contaminated soil. The particles break down pollutants or convert them into less harmful and less mobile forms.

What is biochar?

When added to contaminated soil, it traps pollutants, reduces their movement, and can improve soil quality.

What is remediation time?

The time needed to clean up, contain, or reduce contamination at a site.

How do remediation times for soils/sediments and air/water compare?

remediation times in air or water are much less that soils and sediments.

Between soil and sediment, which has a faster remediation time? Why?

Sediment has a faster cleanup time because the contaminated sediments would be covered by less contaminated sediments and act as a barrier between surface water.

How does soil clean itself up?

Leaching

What are hydrophobic compounds?

Compounds that do not interact with water. Usually organic pollutants and metals.

Why do hydrophobic compounds have a high remediation time?

They do not dissolve easily in water and strongly attach to soil. This means that they're less mobile.

Why do soluble pollutants have a low remediation time?

They dissolve easily in water and are mobile. This means that it's easier to extract and treat.

What is the soil storage capacity?

The amount of pollutant that a soil can hold or trap before it moves into groundwater or runoff.

What is the idea of a "chemical time bomb"?

A pollutant stored in soil or sediment may remain trapped for years, then suddenly be released when environmental conditions change

What capacity controlling parameters could change the soil storage capacity?

pH conditions, Redox conditions, Organic matter, Carbon exchange capacity, Clay content, Salinity conditions, Cation exchange capacity, and clay content.

How does pH affect soil pollution?

pH controls how strongly pollutants bind to soil and how easily they dissolve or move.

What does a low pH mean for soil pollution?

Low pH make metals more soluble and mobile

What does a high pH mean for soil pollution?

High pH makes metals less soluble and mobile

What is the "absorption cliff" for pH?

It shows a sharp and steep change in dissolution of heavy metals due to a small change in pH.

What is the Redox staircase?

As soil becomes more anoxic, it moves down the staircase. These changes can dissolve heavy metals, causing them to be released from the soil or trapped in new forms. This can therefore change the soils pollutant capacity.

What are the steps to the redox staircase>

Aerobic transpiration, denitrification, Manganese reduction, Iron reduction, Sulfate reduction, Methane formation.

What is aerobic transpiration on the Redox staircase?

microorganisms use oxygen and deplete the oxygen content, giving anoxic conditions.

What is denitrification in the Redox staircase?

After oxygen in depleted, microorganisms use nitrate and is converted into nitrogen gas and released into the atmosphere.

What are the manganese and iron reduction zones in the redox staircase?

once oxygen and nitrate are depleted, microorganisms use manganese and iron compounds, converting them into ions, which dissolve easily.

What is the sulfate reduction stage in the redox staircase?

Once oxygen, nitrate, manganese, and iron are depleted, microorganisms use sulfate and create sulfide

What is methane fermentation in the redox staircase?

Under the most oxygen depleted conditions, microorganisms break down organic matter and produce methane.

How does soil organic matter affect soil storage capacity?

Soil organic matter binds and stores many pollutants, mainly hydrophobic compounds and metals, so soil with more (OM%) has a greater capacity.

What is humus?

A nutrient-rich organic matter formed from plant and animal material decomposition.

Why do aerated soils have less organic matter?

Oxygen allows microorganisms to decompose organic matter quickly, so the soils contain less organic matter.

Why do saturated soils have higher organic matter?

Limited oxygen slows decomposition, allowing organic matter to accumulate

What are mineral soils?

Soils with high sand, silt, and clay content with little organic matter.

How can organic matter content increase?

Use of organic fertilizers, reducing tillage to allow crop residues to accumulate on surface, wetland creation/conversion, and land conversions.

How can organic matter decrease?

Drainage of wetlands, use of chemical fertilizers, deforestation, and land conversion.

What is cation exchange capacity (CEC)?

A measure of a soil's ability to hold and supply cations (Ca²⁺, Mg²⁺, K⁺, NH₄⁺)

How can we increase a soils CEC?

Adding liming acids to soils (increasing pH).

How does clay affect soils storage capacity?

Clay have negatively charge surfaces, high CEC, and a large surface area, allowing it to bind to positively charged pollutants.

How do salinity condition affect soil storage capacity?

Salt ions compete for binding sites and displace absorbed or precipitated metals. These metals enter the soil water and become mobile, contaminating groundwater or runoff. (ONLY applies to metals)