Physics Today Daily Edition
Science: Tetrafluoromethane (CF4) is a greenhouse gas that persists in the atmosphere for 50 000 to 100 000 years. It is commonly produced by the weathering of granite and other metamorphic rocks by rainfall. Now Daniel Deeds of the US Geological Survey and his colleagues have discovered that CF4 is also produced by tectonic activity. Surprised to find the chemical in groundwater samples collected near an active fault in the Mojave Desert, the researchers then examined 14 samples taken from aquifers along part of the San Andreas Fault. All but one of the samples showed higher CF4 levels than did water that had been exposed to the air. That suggested the gas was being absorbed from stone deep underground. The researchers also found that the samples from closer to the fault had higher concentrations of the gas than did those from farther away. Whether the CF4 is produced by the fracturing of rocks during earthquakes or by pressure stresses is not clear. However, the discovery that CF4 levels are not exclusively tied to weathering means they are no longer a reliable indicator of past changes in climate.
New Scientist: Following the 2004 tsunami in the Indian Ocean, several studies examined satellite data to determine the ability of mangrove forests to protect communities from the destructive effects of such seismic sea waves. One study found an 8% reduction in fatalities in villages protected by mangrove forests. Another found that a 100-m-wide band of dense mangrove growth could reduce the strength of a tsunami by up to 90%. In the years since the tsunami, several groups have worked to restore and expand mangrove forests along shorelines of countries bordering the Indian Ocean. The most successful appears to be the Green Coast project run by Oxfam Novib and Wetlands International. The organizations planted mangroves in the Indonesian province of Aceh and provided loans to residents to establish new businesses in their villages. The villages were left in charge of maintaining the new mangrove trees. If 75% of the trees were still growing after 2 years, the loan debts were written off. Almost 2 million trees were planted near 70 villages, and five years after the end of the project most of the businesses are still operating.
Telegraph: A study earlier this year revealed a higher rate of skin cancer in pilots than in the general population. A new study by Martina Sanlorenzo of the University of California, San Francisco, and her colleagues shows that every 56 minutes that airline pilots spend at a normal cruising altitude of 30 000 ft (9144 m) exposes them to as much UV radiation as a 20-minute session in an average tanning bed. They measured UV-A exposure at ground level and in cockpits during flights to Los Vegas, Nevada, in April 2014. For every 2952 ft (900 m) of altitude gained above sea level, the radiation exposure increased by 15%. At the typical cruising altitude for commercial aircraft, UV levels were more than twice those on the ground.