Page - 30 - in Water, Energy, and Environment - A Primer

agricultural runoff.Fossil fuels, amajor sourceof thermalenergy forelectricitygeneration,createalargenumberof toxicemissions whencombusted: carbondioxide (CO2), carbonmonoxide (CO), sulfur dioxide (SO2), nitrogen oxides (NOx), particulate matter (PM), heavy metals such as mercury (Hg), and low levels of radioactivity released when coal is burned. Combustion products contaminate the air we breathe and can contaminate water sources unless carefully controlled. Nitrogen-rich fertilizers, now widely used in agriculture, release nitrogen dioxide (NO2) into the atmosphere; NO2 is a powerful greenhouse gas, much more so than CO2. CH4 is widely used as a fuel in power generation, and is also apowerful greenhouse gas that can leak into the atmosphere if not carefully contained. In addition, the transport of fossil fuels – as in the movement of petroleum products through pipelines and by rail – has occasionally involved accidents that have spilled large amounts of petroleum, threatened water supplies, and in some cases led to damaging fires. Deforestation and land degradation: trees are a major sink for CO2, which is required for biomass growth.When they are chopped down for energy use or other uses and not replaced systematically, the land is degraded in termsof itswater-holding ability and its aesthetic appearance. With less vegetation, less CO2 is removed from the atmosphere, and combined with the contemporaneous release of CO2 into the atmosphere from the combustion of fossil fuels the atmosphere’s average concentration of CO2 increases. This enhances the global warming effect. Also, power plants can have large footprints that prevent other uses of surface areas as well as changing the covered ground’s reflective properties (albedo), which can also contribute toglobalwarming. Habitat destruction and loss of biodiversity: the destruction of forests has another impact, the removal of traditional homes/habitats for many species of animals. If these animals cannot move and adapt to new habitats, their numbers Water,Energy, andEnvironment–APrimer30