Soil pH regulates the capacity of soils to store and supply nutrients, and thus contributes substantially to controlling productivity in terrestrial ecosystems.

However, soil pH is not an independent regulator of soil fertility—rather, it is ultimately controlled by environmental forcing. In particular, small changes in water balance cause a steep transition from alkaline to acid soils across natural climate gradients.

Although the processes governing this threshold in soil pH are well understood, the threshold has not been quantified at the global scale, where the influence of climate may be confounded by the effects of topography and mineralogy. Here we evaluate the global relationship between water balance and soil pH by extracting a spatially random sample (n = 20,000) from an extensive compilation of 60,291 soil pH measurements. Read more

New research from Caltech shows that sour-sensing taste cells play an important role in detecting water on the tongue.

The work, appearing in a paper in the May 29 issue of the journal Nature Neuroscience, was done in the laboratory of Yuki Oka, assistant professor of biology.

“The tongue can detect various key nutrient factors, called tastants — such as sodium, sugar, and amino acids — through taste,” says Oka. “However, how we sense water in the mouth was unknown. Many insect species are known to ‘taste’ water, so we imagined that mammals also might have a machinery in the taste system for water detection.”

Taste cells relay information about tastants to the brain via nerves called the taste nerves. First author and graduate student Dhruv Zocchi measured the electrical responses from taste nerves in mice to various tastants as well as to water. The nerves responded in predictable ways to different basic tastes — sweet, sour, bitter, salty, and umami — but they were also stimulated by pure water. “This was exciting because it implied that some taste cells are capable of detecting water,” Zocchi says. Read more

The location and persistence of surface water (inland and coastal) is both affected by climate and human activity and affects climate, biological diversity and human wellbeing. Global data sets documenting surface water location and seasonality have been produced from inventories and national descriptions, statistical extrapolation of regional data8 and satellite imagery, but measuring long-term changes at high resolution remains a challenge.

Here, using three million Landsat satellite images, we quantify changes in global surface water over the past 32 years at 30-metre resolution. We record the months and years when water was present, where occurrence changed and what form changes took in terms of seasonality and persistence. Between 1984 and 2015 permanent surface water has disappeared from an area of almost 90,000 square kilometres, roughly equivalent to that of Lake Superior, though new permanent bodies of surface water covering 184,000 square kilometres have formed elsewhere. Read more

Researchers at Dartmouth College have developed a new material that scrubs iodine from water for the first time. The breakthrough could hold the key to cleaning radioactive waste in nuclear reactors and after nuclear accidents like the 2011 Fukushima disaster.

The new-generation microporous material designed at Dartmouth is the result of chemically stitching small organic molecules to form a framework that scrubs the isotope from water.

“There is simply no cost-effective way of removing radioactive iodine from water, but current methods of letting the ocean or rivers dilute the dangerous contaminant are just too risky,” said Chenfeng Ke, assistant professor in the Department of Chemistry at Dartmouth College. “We are not sure how efficient this process will be, but this is definitely the first step toward knowing its true potential.” Read more

Without action, the supply of fresh water in Iqaluit will begin to dwindle by 2024 due to climate change and increased demand, research led by York University has found.

“Extreme climates make the management of fresh water difficult, but add climate change to the mix, along with too few financial and human resources, and northern cities, such as Iqaluit could run out of fresh water,” said Andrew Medeiros of York U who led the research.

Even if population growth remains stagnant, current climate change projections show demand will outstrip supply for freshwater in the Arctic community, said Medeiros, a research fellow for York University’s Robarts Centre for Canadian Studies. However, as Iqaluit is a growing city, the pressure on water resources will only increase. Read more