Groundwater is vulnerable to pollutants that leach from the land surface. This ‘diffuse’ pollution comes from non-point source, widespread activities within the current and past agricultural and urban environments. There is also a contribution from atmospheric deposition.
Diffuse pollution can leach from the land surface into groundwater from non-point sources such as crop spraying. BGS © UKRI.
Rural sources of diffuse pollution
Rural diffuse pollution arises from land-use activities spread across large areas, such as:
- fertilisers and pesticides used in the cultivation of land to grow crops
- livestock grazing with associated manure and slurry storage and disposal
- sewage sludge disposal
- forestry operations
Dispersed housing may also be a source.
Livestock manure can be a source of groundwater pollution. Image by from .
The pollutants of concern include:
- nutrients such as nitrogen (typically in the form of nitrate) and phosphorus
- pesticides
- Per- and polyfluoroalkyl substances (PFAS)
- metals
- artificial micro- and nanoparticles (for example, plastics; tyre wear particles)
- biodegradable substances
- ammonia
- microorganisms, such as faecal coliforms
Urban sources of diffuse pollution
In urban areas, both industrial and municipal activities generate pollutants. Urbanisation changes the natural pattern of recharge to groundwater with run-off from built areas and impervious surfaces, such as roads and car parks. There is also input from mains water, leaking sewers and pluvial drains.
Infiltration may carry a mix of polluting substances, such as:
- toxic metals
- pesticides
- oils and hydrocarbons
- sediments
- oxygen-depleting substances
- tyre wear and plastic particles and additives
Emerging contaminants
Recently, advancing analytical techniques have identified a range of widespread emerging contaminants in groundwater, including:
- pesticide breakdown products
- pharmaceuticals
- food additives
- industrial compounds
- PFAS
- caffeine
- microplastics
- tyre wear additives
Further reading
Ascott, M,Lewis, M,Gooddy, D,Mackay, J,Smedley, P L, andCartwright, C. 2022. . British Geological Survey Open Report OR/22/076. (Nottingham, UK: British Geological Survey, 134pp.)
Lapworth, D J, and Shockley, D J. 2022. . British Geological Survey Open Report OR/22/015. (Nottingham, UK: British Geological Survey.)
Morris, B, and Cunningham, J. 2008. .Water and Environment Journal, Vol. 22(2), 88–99. DOI: https://doi.org/10.1111/j.1747-6593.2007.00082.x
Morris, B L, Darling, W G, Cronin, A A, Rueedi, J, Whitehead, E J, and Gooddy, D C. 2006. .Hydrogeology Journal, Vol. 14 (6), 979–997. DOI: https://doi.org/10.1007/s10040-006-0028-1
Rueedi, J, Cronin, A A, and Morris, B. 2009. .Water and Environment Journal, Vol. 23(2), 134–144. DOI: https://doi.org/10.1111/j.1747-6593.2008.00119.x
Vero, S, and Ascott, M. 2022. . Chapter 3 inNitrate Handbook. Tsadilas, C (editor). (Boca Raton, USA: CRC Press.)
White, D, Lapworth, D J, Stuart, M E, and Williams, P J. 2016. . Science of The Total Environment, Vol. 562, 962–973. DOI: https://doi.org/10.1016/j.scitotenv.2016.04.054
Our research
Nitrate contamination of groundwater
Contamination of groundwater by nitrate is increasing and BGS is investigating the cause.
Emerging contaminants in groundwater
Improvements in analysis mean that more organic compounds are being detected in groundwater.