Aquifer Restoration
Water pollution can be grouped into two categories:
1) Naturally-Occurring Pollution
An example of naturally-occurring pollution is the high concentrations of arsenic in Bangladesh groundwater, which is generally believed to originate from the unconsolidated sediments (sands, silts, clays and gravels) that host the groundwater
2) Man-made, or Anthropogenic Pollution
Most anthropogenic groundwater pollution can be categorized into either agricultural, sewage, or industrial pollution (Figure 1). There is widespread nitrate and phosphate pollution from agricultural and sewage sources, including fertilizers, animal manure and human sewage, and detergents. Industrial pollutants can be grouped as fuels (gasoline, diesel), solvents (degreasers including trichloroethylene), metals (cars, batteries), semi-volatile organic compounds (pesticides, polychlorinated biphenyls [PCBs]), and wood treatment compounds (pentachlorophenol in creosote); and explosives,
Restoration of Portions of Contaminated Groundwater
Areas of contaminated groundwater, often referred to as plumes, are commonly caused by human activities (anthropogenic effects). Plumes of groundwater contamination can also form in areas where there are high concentrations of naturally-occurring elements or compounds such as copper or uranium. Where naturally-occurring or anthropogenic (man-made) pollution exists, cost-effective remediation technologies are available to restore portions of an aquifer to quality levels that may be suitable for agricultural or industrial use. Remediation to drinking water quality levels will be more costly than for other uses, and take longer to achieve, but can likewise be attained. Usable water can be extracted within the radius of influence of a pumping well even where aquifer contamination extends beyond the well. See Chapter 8 UNESCO 2021 (attached below).
The Connection Between Surface H2O & Groundwater
The relationship between surface water and groundwater is of fundamental importance when considering the movement of pollutants.
In many environments, surface water seeps through soil and becomes groundwater. It is also common for groundwater to feed surface water sources. Common naturally-occurring and anthropogenic groundwater pollution sources are summarized in the following table:
Common naturally-occurring and anthropogenic groundwater pollution sources.
Naturally-Occurring Groundwater Pollutants:
Type Source Comment
Arsenic Soils or bedrock Elevated arsenic may occur in many geologic
environments.
Copper,
Lead, Zinc, Higher concentrations in bedrock Bedrock source areas
Cadmium versus soil may leach to groundwater
Uranium & other Soil or bedrock (igneous or Elevated uranium in many aquifers in India.
radionuclides. sedimentary rock.
Iron &
Manganese. Soil or bedrock Often found together in groundwater in elevated
concentrations
Selenium. Coal-bearing or volcanic rocks. Selenium is a significant pollutant, released
& soils in metal & coal mining, power plant effluent
Anthropogenic Groundwater Pollutants:
Type Source. Comment
Fuels. Gasoline & diesel fueling stations, l. Gasoline: carcinogenic with benzene, toluene,
large spill locations ethylbenzene
Solvents. Degreasers, cleaning solutions, Perchloroethylene dry cleaning fluid now largely
pesticides, glues, resins. phased out, caused enormous groundwater
pollution.
Arsenic Mining and industrial air & water
effluent; diesel exhaust Occurs as arsenites & arsenates; carcinogenic
Heavy Metals: Mining operations, industrial effluent, These heavy metals commonly occur together.
Copper, Lead, road runoff, open burning
Zinc, Cadmium
Selenium. Metal & coal mining, effluent from Increasingly recognized as a significant pollutant
power plants that occurs naturally but mobilized during mining.
Uranium & Nuclear weapons production, Uranium, radon & radium occur together in
other power plants, coal & groundwater
radionuclides phosphate mining, uranium mining
Nitrates,
phosphates & Fertilizer runoff from agriculture, Nitrates in urea or ammonium nitrate are most
potassium. commercial or residential sources; widely used in fertilizers
septic systems
Polychlorinated Formerly used as a di-electric oily Very stable and present throughout food chain;
Biphenyls fluid in transformers, and a lubricant banned in US & EU
(PCBs)
Per- and. Flame-retardant) in carpet, furniture; Over 4,000 known PFAS compounds;
Polyfluoroalkyl formerly in Teflon; still used in exceedingly stable; understudied
Substances aqueous fire fighting foam (AFFF)
Pentachloro- A wood preservative Exceedingly stable
phenol
(Creosote)
Prescription Septic systems and wastewater Antibiotics & blood-pressure medicines are
Drugs treatment plants (WWTPs) being increasingly detected in groundwater
Microplastics plastic bags & containers Presence & extent in groundwater is poorly
known due to lack of sampling
Pesticides and Surficial soils in agricultural areas Chemicals reach groundwater via runoff
Herbicides leaching.
Classes of Pollutants
Heavy metals such as copper, lead zinc, and cadmium; arsenic; uranium;
Emerging Pollutants-Microplastics
Bisphenol A (BPA) is a common constituent of many types of plastic. It is a confirmed endocrine disruptor, which means it can have adverse health effects on hormone function in humans and animals.
Emerging Pollutants-Per- & Polyfluoroalkyl Substances (PFAS)
PFAS compounds are in Teflon, Gore-Tex, aqueous fire fighting foam [AFFF], also known as aqueous film forming foam, and metal plating baths. PFAS are a widespread emerging class of compounds whose toxicity is still being defined, but its cancer-causing (carcinogenic) effects have been confirmed..