SYDNEY, March 10 (Xinhua) -- More than half of the world's population faces a major threat to drinking water quality and availability because climate change and urbanization are set to cause increases in groundwater contaminants, according to latest Australian research.
Dissolved organic carbon (DOC) is a naturally occurring component of groundwater, but the higher its concentration, the more difficult and expensive it is to make groundwater drinkable, according to a University of New South Wales statement on Tuesday.
The study examined a global dataset of more than 9,400 published and unpublished groundwater DOC concentrations from aquifers in 32 countries across six continents, forecasting elevated DOC levels "because of projected changes in temperature and rainfall due to climate change, as well as increased urbanization," it said.
"We identified groundwater DOC concentration increases of up to 45 percent, largely because of increased temperatures in the wettest quarter of the year - for example, in a number of southeastern states in the United States," university researcher and study lead author Liza McDonough said.
"Generally, we expect urbanization to increase groundwater DOC concentrations by up to 19 percent, compared to agricultural or natural land use, likely as the result of contamination - for example, through leaking septic and sewer systems."
The study, published in scientific journal Nature Communications, found four major contributing factors to groundwater DOC levels: climate, land use, inorganic chemistry and aquifer age.
Increased groundwater DOC, naturally occurring or due to contamination, also posed a threat to human health, McDonough said.
"Groundwater is Earth's largest source of freshwater and provides essential drinking water for more than 50 percent of the world's population," she said.
"But, because most health impacts caused by DOC are related to the formation of by-products of water treatment chlorination and depend on concentrations of other water chemical parameters, the World Health Organization and many countries - including Australia - do not regulate DOC concentrations in drinking water directly."
McDonough said that while DOC is a naturally occurring, key element of groundwater, it could combine with, and transport, potentially dangerous heavy metals otherwise bound to rocks and sediment where groundwater occurs.
"This is a concern when, for example, more than 100,000 lifetime cancer cases in the United States alone can be attributed to drinking water contaminants," she said.
McDonough said she looked forward to conducting further research to determine the best water treatment options for areas where groundwater DOC concentrations are anticipated to increase.
"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," she said.
"This will help provide guidance on the most suitable water treatment options in areas where DOC concentrations are expected to increase."
