Study shows groundwater nitrates threaten global water supplies

Groundwater nitrates threaten water supplies worldwide
Researchers at the British Geological Survey have estimated the nitrate pollution stored in rocks above groundwater (as shown in this diagram) across the globe for the first time

Researchers at the British Geological Survey (BGS) have estimated the amount of pollution from nitrates stored in rocks above groundwater for the first time. Their findings could have severe implications for rivers, water supplies and human health worldwide as well as economic consequences.

In a paper published in Nature Communications, Matthew Ascott and fellow researchers from the BGS and Lancaster University reported finding vast quantities of nitrate stored in rocks below ground and above the drinking water resources they hold.

The chemicals have largely been introduced through the use of nitrate fertilizers, which can cause serious damage to ecosystems and contaminate drinking water while also boosting crop production. As it is released from the rocks into rivers via springs, it can cause toxic algal blooms and fish deaths. Nitrate is also the most widespread pollutant in drinking water sources (groundwater and surface water) with water treatment costing industry and consumers billions of pounds a year.

Professor Rob Ward, BGS Director of Groundwater Science and a co-author of the study, said:

“Nitrate is the most wide-spread water pollutant globally. Managing the source of the problem is extremely challenging but early action is essential as more fertilizer use will be needed to meet an increasing population and a growing need for food.”

The authors of the paper have calculated the amount of nitrate present in rocks to be up to 180 million tonnes – up to twice the amount of nitrate stored in soils. They found the most nitrate to be stored in North America, China and Europe, where huge quantities of fertilizer have been applied for decades. In some developed countries, they even found the amount of nitrate stored in the rocks to be increasing, despite improvements in farming practice and the introduction of regulations to control the pollutant. In developing countries, whilst the problem is currently not so severe, there is evidence of a worsening situation that requires early intervention to avoid the same problems and environmental damage experienced by highly developed countries.

Matthew Ascott, hydrogeologist at the BGS and lead author of the study, said: “With big investments being made to reduce water pollution through changes in farming, it is vital that we understand what pollution is already in the environment. Water and the pollutant travels through the rocks below our feet very slowly. This and a history of intensive agriculture means that a large store of nitrate pollution has built up over time. When this pollution is released, it will continue to impact water quality for decades, in some cases, even where controls on fertilizer use have been put in place.”