■ Using only low-sulfur coal
■ “Washing” the coal—by mixing crushed coal with water, impurities with
different densities are able to be separated and removed
■ Fluidized gas combustion (i.e., crushed limestone is added to crushed coal
to produce calcium sulfite, calcium sulfate, or gypsum)
■ Using scrubbers in the smokestacks—in the scrubber, there is a water
spray that produces a cloud of fine water droplets which mix with crushed
limestone and react with the sulfur and “pull” it out of the exhaustSUSPENDED PARTICULATE MATTER (PMX)
Suspended particulate matter (PMx) is microscopic solid or liquid matter
suspended in the Earth’s atmosphere. The “x” refers to the size of the particles
(e.g., PM 10 represents particles with an average size of 10 microns [ten-
millionths of a meter—the average diameter of a human hair is 50 microns]).
Naturally Occurring PMx Anthropogenic PMxVolcanoes Burning of fossil fuels—power
plantsDust storms Vehicle exhaustForest and grassland fires Incineration of wastesSea spray Soil erosion—desertification,
deforestationIn general, the smaller and lighter a particle is, the longer it will stay in the
air. Larger particles (greater than 10 micrometers in diameter) tend to settle to
the ground by gravity in a matter of hours, whereas the smallest particles (less
than 1 micrometer) can stay in the atmosphere for weeks and are mostly
removed by precipitation.
Particulate matter :
■ Makes lakes and streams more acidic.
■ Changes the nutrient balance in coastal waters and large river basins.
■ Depletes the nutrients in soil.
■ Damages sensitive forests and farm crops.