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Contaminated land and Groundwater :oil_drum: - Coggle Diagram
Contaminated land and Groundwater
:oil_drum:
Sources
Extraction of geological resources is the main responsibility for pollutants
Most is inert waste
Coal, metal ore waste
Contains sulfide
Once exposed to oxygen/water
Create acid waters with metals in solution
Oil/Gas extraction/refining
Resulting in contamination of organic pollutants
Fracking has raised concern
Agriculture
Organic waste
Hazardous material
Pesticides
Domestic/Commercial
Requires consideration of underlying geology
Brownfields
Land that has been used for commercial/industrial purposes
Well known to contain pollutants
Soil contamination by hazardous waste
Pollution Problems
Must be prevented from harming
People
Livestock
Wildlife
Pollution has to be isolated
Prevent breathing/ingestion
Easier to achieve if pollutant cannot be move by water
Not taken into solution
Not carried as emulsion
Suspended particles
Geological/engineering knowledge is needed to predict water movement
Destination of metals is a concern
Examples
Nickel
Copper
Manganese
Mercury
Cadmium
Lead
Chronium
Concern over toxicity
Simple Geochemical analysis may be misleading
Bioavailability is very important
the proportion of total metals that are available for incorporation into biota
In reducing conditions
Metals are locked up
Lowering the water table results in oxidation/mobilisation
Insoluble sulfides
Below water table
Deep underwater
Disturbing the land will change the nature of the problem
Increasing permeability
Therefore increasing oxidation
Increasing surface area
Remediation
Phytoremediation
Plants
Can deal with substances that do not benefit them
Heavy metals cannot damage plants
Stored in their leaves
Drawn through solution
Use of bioaccumulation
Organism absorbs a substance quicker than its lost
plants are removing the metals from the soil
Removing and disposing of the leaves removes the metal
Stabilisation and Solidification (S/S)
Aims to immobilise the toxic constituents
Prevents them from leaching
Immobilisation
Done by reducing the solubility of waste components
Done by isolating waste
S/S treatments
mixing a variety of binding reagents into contaminated ground/waste
Commonly included
Portland cement
Lime
Limestone
Fly ash
Slag
Gypsum
Phosphate mixtures
Controversial subject in the UK
Used in USA
Best Demonstrated Available Technology (BDAT)
Treating hazardous waste
Radioactive
Increasingly used for treating contaminated soil at sites being redeveloped
Groundwater treatments
Can be pumped up and treated
Clays and their minerals
Routinely successfully used
absorbent
Remove toxic heavy metals from aqueous solutions
Organic contaminates
Perfluorinated compound (PFCs)
respond to ion exchange treatments
Resins can be regenerated for reuse
Using activated carbon
In situ
Involve chemicals introduced into the subsurface
At periphery of polluted site
Designed to intercept and immobilise water borne contaminates
Metals
Adding caustic soda
Increases pH
Precipitates metal hydroxides
There's a minimum solubility
At a particular pH
Raising the alkalinity indiscriminately
Hydroxides are removed by adding coagulants
Aluminium salts/polymers
Causing flocculation
Superficial deposits can be treated
In Situ
Use soil augers to distribute
Dug up and treated elsewhere
Treatments varied
Based on chemical treatments
Designed in labs with samples
Overview
The UK has a high population density
Long history of heavy industry
75% of land is for agriculture
Increasing use of brownfields sites
Treatment of land is needed to make it safe
Detailed knowledge of chemistry is needed