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Climate Change And Urbanisation Exacerbate Natural Contaminant Threat to Groundwater Quality, Availability

SYDNEY, Australia

A quarter of the world's population faces theats to quality and availability of drinking water because of climate change and urbanisation.

New research (Nature Communications) led by the University of New South Wales (UNSW) in Sydney examined the largest global dataset of 9404 published and unpublished groundwater dissolved organic carbon (DOC) concentrations from aquifers in 32 countries across six continents. DOC is a naturally occurring component of groundwater, but the higher its concentration, the more difficult and expensive it is to make groundwater drinkable. The research found that climate, land use, inorganic chemistry, and aquifer age contribute to groundwater DOC levels.

The study found that increased temperatures at the wettest part of the year had led to higher concentrations of groundwater DOC, causing considerable increase in treatment required to render the water drinkable.

Any existing groundwater contamination would be further compromised in the higher temperature scenario, particularly affecting China, India and parts of Africa. In the south-east US, the cost for a family of four were predicted to rise by about $134 USD per year.

Lead author, Liza McDonough said: “Generally, we expect urbanisation to increase groundwater DOC concentrations by up to 19 per cent, compared to agricultural or natural land use, likely as the result of contamination – for example, through leaking septic and sewer systems.”

The study suggests that the need to implement additional water treatment measures to remove increased DOC concentrations would cause the cost of water treatment to rise, as much as by 16 percent in some parts of the United States.

The impact of DOC levels from climate change and urbanization are likely to be different according to geography and climate.

“Our research found that in arid climates, groundwater DOC concentrations increased with higher rainfall because microbes can better break down organic matter, such as leaves, under warm and increasingly wet conditions.

“Increased temperatures in arid environments, however, reduced groundwater DOC concentrations because when conditions are too hot and dry, vegetation and organic matter sources are limited.

“By contrast, increased rain in warm and wet environments decreased groundwater DOC concentrations because heavy rainfall dilutes the DOC in groundwater.”

The next step in the research would be to determine the best treatment options and target the study where increased DOC are anticipated.

“Our next step is to investigate how the character of DOC changes when you have different aquifer minerals, because some types of organic matter can stick to certain mineral surfaces and ultimately reduce this type of organic matter remaining in the water.

“This will help provide guidance on the most suitable water treatment options in areas where DOC concentrations are expected to increase.”

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