Water Quality made in boreal forest fire plumes over Canada,” and these data are in “very good agreement between emission estimates derived from different aircraft studies by different groups …” The authors compared the emission rates of toluene based on values from previously published reports. They concluded that the total toluene emission rate for biomass burning is 1.11 million tonnes per year. Plants, dust, soot, vapour Large volumes of dust, soot and vapour rise into the atmosphere around the planet. Each of these has been shown to contain some toluene all the time or at least sometimes. The book “The Secret Life of Dust”, H. Holmes (2001), provides data from highly regarded journals and institutions such as the Journal of Geophysical Research, Science, Nature, NASA, U.S. Centers for Disease Control and Scientific American, regarding the input of toluene and other substances to our atmosphere. • “Between 1-3 billion tons of dust fly up into the sky annually.” Toluene has been measured in dust. • “Trees and other plants exhale a billion tons of organic chemicals into the wind, perhaps one-third of which condenses into tiny sailing beads.” Toluene is a natural, major component of these organic chemicals. • “Burning trees and grasses throw up six million tons of black soot.” As seen earlier, toluene is found in burn gases and soot. • “Eight million tons of black soot are attributable … to the conflagration of fossil fuels - especially coal.” Toluene is present in coal. Given the very large amounts of soot, dust, and vegetative vapour, it is not surprising that toluene, one of the most frequently detected volatile organic compounds in the atmosphere and the biosphere, is considered “ubiquitous.”
Environmental significance of atmospheric toluene Once toluene is in the atmosphere, some of it is degraded by various atmospheric processes. However, numerous studies show that toluene is regularly detected and measured in rain, snow, surface water, groundwater, drinking water and seawater.
Large volumes of dust, soot and vapour rise into the atmosphere around the planet. Each of these has been shown to contain some toluene. Toluene in water Toluene is found in water as a result of its natural production by geological processes over millions of years. These processes result from bacteria in water and sediments, plants on land and in water and atmospheric processes such as precipitation.
Toluene from ocean/sea water seeps A publication from the US Geological Survey “Natural Seepage of Crude Oil into the Marine Environment” sums up the role of natural oil seeps. The amount of natural crude oil seepage is currently estimated to be 600,000 tonnes/year, with a range of uncertainty of 200,000 to 2,000,000 tonnes/year. Thus, natural oil seeps may be the single most important source of oil that enters the ocean, exceeding each of the various sources of crude oil that enters the ocean through its exploitation by humankind.” Toluene in groundwater Toluene is found in water near geologic formations below the Earth’s surface and is persistent in groundwater because it is resists anaerobic biodegradation. Groundwater sources of toluene are often found in limestone or shalebased rock formations and it is present in naturally occurring coal seams. Toluene in drinking water Numerous government agencies have analyzed toluene and other organic chemicals in drinking water: • “In a study of more than 800 water samples taken across Canada from 1985 to 1988, concentrations of toluene in only six samples were greater than 0.5 µg/l.” Actual values ranged continued overleaf...
Burning tires Globally, hundreds of millions of tires are discarded each year. They are generally stored in large numbers in landfills, which occasionally ignite. One of the largest tire fires in Ontario was in 1990; with 1,300 people evacuated from the black oily smoke as 14 million tires burned for 17 days. www.esemag.com
124 MA.15_Toluene.indd 59
March/April 2015 | 59
4/1/15 8:54 PM