groundwater pollution groundwater pollution groundwater pollution (also called groundwater contamination) occurs when pollutants are released to the ground and make their way into groundwater. this type of water pollution can also occur naturally due to the presence of a minor and unwanted constituent, contaminant, or impurity in the groundwater, in which case it is more likely referred to as contamination rather than pollution. groundwater pollution can occur from on-site sanitation systems, landfill leachate, effluent from wastewater treatment plants, leaking sewers, petrol filling stations, hydraulic fracturing (fracking) or from over application of fertilizers in agriculture. pollution (or contamination) can also occur from naturally occurring contaminants, such as arsenic or fluoride. using polluted groundwater causes hazards to public health through poisoning or the spread of disease (water-borne diseases). part of a series onpollutiongroundwater pollution example in lusaka, zambia, where the pit latrine in the background is polluting the shallow well in the foreground with pathogens and nitrate air acid rain air quality index atmospheric dispersion modeling chlorofluorocarbon exhaust gas haze indoor air internal combustion engine global dimming global distillation ozone depletion particulates persistent organic pollutant smog aerosol soot volatile organic compound biological biological hazard genetic introduced species (invasive species) digital information electromagnetic light ecological overillumination radio spectrum natural ozone radium and radon in the environment volcanic ash wildfire noise transportation land water air rail sustainable transport urban sonar marine mammals and sonar industrial military abstract noise control radiation actinides bioremediation depleted uranium nuclear fission nuclear fallout plutonium poisoning radioactivity uranium electromagnetic radiation and health radioactive waste soil agricultural herbicides manure waste pesticides land degradation bioremediation defecation electrical resistance heating soil guideline values phytoremediation solid waste biodegradable waste brown waste electronic waste battery recycling food waste green waste hazardous waste biomedical waste chemical waste construction waste lead poisoning mercury poisoning toxic waste international waste industrial waste lead smelting litter mining coal mining gold mining surface mining deep sea mining mining waste uranium mining municipal solid waste garbage nanomaterials plastic microplastics packaging waste post-consumer waste waste management landfill thermal treatment space satellite thermal urban heat island visual air travel advertising clutter overhead power lines traffic signs vandalism war chemical warfare herbicidal warfare (agent orange) nuclear holocaust (nuclear fallout - nuclear famine - nuclear winter) scorched earth unexploded ordnance war and environmental law water agricultural wastewater diseases eutrophication firewater freshwater groundwater hypoxia industrial wastewater marine debris monitoring nonpoint source see misc section nutrient ocean acidification oil spill pharmaceuticals freshwater salinization septic tanks sewage septic tanks pit latrine shipping stagnation sulfur water surface runoff turbidity urban runoff water quality misc point source area source legacy pollution lists diseases law by country most polluted cities least polluted cities by pm2.5 treaties categories by country environment portal ecology portal the pollutant often creates a contaminant plume within an aquifer. movement of water and dispersion within the aquifer spreads the pollutant over a wider area. its advancing boundary, often called a plume edge, can intersect with groundwater wells and surface water, such as seeps and springs, making the water supplies unsafe for humans and wildlife. the movement of the plume, called a plume front, may be analyzed through a hydrological transport model or groundwater model. analysis of groundwater pollution may focus on soil characteristics and site geology, hydrogeology, hydrology, and the nature of the contaminants. different mechanisms have influence on the transport of pollutants, e.g. diffusion, adsorption, precipitation, decay, in the groundwater. the interaction of groundwater contamination with surface waters is analyzed by use of hydrology transport models. interactions between groundwater and surface water are complex. for example, many rivers and lakes are fed by groundwater. this means that damage to groundwater aquifers e.g. by fracking or over abstraction, could therefore affect the rivers and lakes that rely on it. saltwater intrusion into coastal aquifers is an example of such interactions. prevention methods include: applying the precautionary principle, groundwater quality monitoring, land zoning for groundwater protection, locating on-site sanitation systems correctly and applying legislation. when pollution has occurred, management approaches include point-of-use water treatment, groundwater remediation, or as a last resort, abandonment. pollutant types contaminants found in groundwater cover a broad range of physical, inorganic chemical, organic chemical, bacteriological, and radioactive parameters. principally, many of the same pollutants that play a role in surface water pollution may also be found in polluted groundwater, although their respective importance may differ. arsenic and fluoride main article: arsenic contamination of groundwater arsenic and fluoride have been recognized by the world health organization (who) as the most serious inorganic contaminants in drinking-water on a worldwide basis. inorganic arsenic is the most common type of arsenic in soil and water. the metalloid arsenic can occur naturally in groundwater, as seen most frequently in asia, including in china, india and bangladesh. in the ganges plain of northern india and bangladesh severe contamination of groundwater by naturally occurring arsenic affects 25% of water wells in the shallower of two regional aquifers. groundwater in these areas is also contaminated by the use of arsenic-based pesticides. arsenic in groundwater can also be present where there are mining operations or mine waste dumps that will leach arsenic. natural fluoride in groundwater is of growing concern as deeper groundwater is being used, "with more than 200 million people at risk of drinking water with elevated concentrations." fluoride can especially be released from acidic volcanic rocks and dispersed volcanic ash when water hardness is low. high levels of fluoride in groundwater is a serious problem in the argentinean pampas, chile, mexico, india, pakistan, the east african rift, and some volcanic islands (tenerife) in areas that have naturally occurring high levels of fluoride in groundwater which is used for drinking water, both dental and skeletal fluorosis can be prevalent and severe. pathogens waterborne diseases can be spread via a groundwater well which is contaminated with fecal pathogens from pit latrines. the lack of proper sanitation measures, as well as improperly placed wells, can lead to drinking water contaminated with pathogens carried in feces and urine. such fecal-oral transmitted diseases include typhoid, cholera and diarrhea. of the four pathogen types that are present in feces (bacteria, viruses, protozoa, and helminths or helminth eggs), the first three can be commonly found in polluted groundwater, whereas the relatively large helminth eggs are usually filtered out by the soil matrix. deep, confined aquifers are usually considered the safest source of drinking water with respect to pathogens. pathogens from treated or untreated wastewater can contaminate certain, especially shallow, aquifers. nitrate nitrate is the most common chemical contaminant in the world's groundwater and aquifers. in some low-income countries, nitrate levels in groundwater are extremely high, causing significant health problems. it is also stable (it does not degrade) under high oxygen conditions. elevated nitrate levels in groundwater can be caused by on-site sanitation, sewage sludge disposal and agricultural activities. it can therefore have an urban or agricultural origin. nitrate levels above 10 mg/l (10 ppm) in groundwater can cause "blue baby syndrome" (acquired methemoglobinemia). drinking water quality standards in the european union stipulate less than 50 mg/l for nitrate in drinking water. the linkages between nitrates in drinking water and blue baby syndrome have been disputed in other studies. the syndrome outbreaks might be due to other factors than elevated nitrate concentrations in drinking water. organic compounds volatile organic compounds (vocs) are a dangerous contaminant of groundwater. they are generally introduced to the environment through careless industrial practices. many of these compounds were not known to be harmful until the late 1960s and it was some time before regular testing of groundwater identified these substances in drinking water sources. primary voc pollutants found in groundwater include aromatic hydrocarbons such as btex compounds ( benzene, toluene, ethylbenzene and xylenes), and chlorinated solvents including tetrachloroethylene (pce), trichloroethylene (tce), and vinyl chloride (vc). btex are important components of gasoline. pce and tce are industrial solvents historically used in dry cleaning processes and as a metal degreaser, respectively. other organic pollutants present in groundwater and derived from industrial operations are the polycyclic aromatic hydrocarbons (pahs). due to its molecular weight, naphthalene is the most soluble and mobile pah found in groundwater, whereas benzo(a)pyrene is the most toxic one. pahs are generally produced as byproducts by incomplete combustion of organic matter. organic pollutants can also be found in groundwater as insecticides and herbicides. as many other synthetic organic compounds, most pesticides have very complex molecular structures. this complexity determines the water solubility, adsorption capacity, and mobility of pesticides in the groundwater system. thus, some types of pesticides are more mobile than others so they can more easily reach a drinking-water source. metals several trace metals occur naturally in certain rock formations and can enter in the environment from natural processes such as weathering. however, industrial activities such as mining, metallurgy, solid waste disposal, paint and enamel works, etc. can lead to elevated concentrations of toxic metals including lead, cadmium and chromium. these contaminants have the potential to make their way into groundwater. the migration of metals (and metalloids) in groundwater will be affected by several factors, in particular by chemical reactions which determine the partitioning of contaminants among different phases and species. thus, the mobility of metals primarily depends on the ph and redox state of groundwater. pharmaceuticals trace amounts of pharmaceuticals from treated wastewater infiltrating into the aquifer are among emerging ground-water contaminants being studied throughout the united states. popular pharmaceuticals such as antibiotics, anti-inflammatories, antidepressants, decongestants, tranquilizers, etc. are normally found in treated wastewater. this wastewater is discharged from the treatment facility, and often makes its way into the aquifer or source of surface water used for drinking water. trace amounts of pharmaceuticals in both groundwater and surface water are far below what is considered dangerous or of concern in most areas, but it could be an increasing problem as population grows and more reclaimed wastewater is utilized for municipal water supplies. others other organic pollutants include a range of organohalides and other chemical compounds, petroleum hydrocarbons, various chemical compounds found in personal hygiene and cosmetic products, drug pollution involving pharmaceutical drugs and their metabolites. inorganic pollutants might include other nutrients such as ammonia and phosphate, and radionuclides such as uranium (u) or radon (rn) naturally present in some geological formations. saltwater intrusion is also an example of natural contamination, but is very often intensified by human activities. groundwater pollution is a worldwide issue. a study of the groundwater quality of the principal aquifers of the united states conducted between 1991 and 2004, showed that 23% of domestic wells had contaminants at levels greater than human-health benchmarks. another study suggested that the major groundwater pollution problems in africa, considering the order of importance are: (1) nitrate pollution, (2) pathogenic agents, (3) organic pollution, (4) salinization, and (5) acid mine drainage. causes causes of groundwater pollution include (further details below): naturally-occurring (geogenic) on-site sanitation systems sewage and sewage sludge fertilizers and pesticides commercial and industrial leaks hydraulic fracturing landfill leachate other naturally-occurring (geogenic) "geogenic" refers to naturally occurring as a result from geological processes. the natural arsenic pollution occurs because aquifer sediments contain organic matter that generates anaerobic conditions in the aquifer. these conditions result in the microbial dissolution of iron oxides in the sediment and, thus, the release of the arsenic, normally strongly bound to iron oxides, into the water. as a consequence, arsenic-rich groundwater is often iron-rich, although secondary processes often obscure the association of dissolved arsenic and dissolved iron.. arsenic is found in groundwater most commonly as the reduced species arsenite and the oxidized species arsenate, the acute toxicity of arsenite being somewhat greater than that of arsenate. investigations by who indicated that 20% of 25,000 boreholes tested in bangladesh had arsenic concentrations exceeding 50 μg/l. the occurrence of fluoride is close related to the abundance and solubility of fluoride-containing minerals such as fluorite (caf2). considerably high concentrations of fluoride in groundwater are typically caused by a lack of calcium in the aquifer. health problems associated with dental fluorosis may occur when fluoride concentrations in groundwater exceed 1.5 mg/l, which is the who guideline value since 1984. the swiss federal institute of aquatic science and technology (eawag) has recently developed the interactive groundwater assessment platform (gap), where the geogenic risk of contamination in a given area can be estimated using geological, topographical and other environmental data without having