MadSci Network: Environment/Ecology

Re: Specific particle size (microns) of common drinking water contaminants?

Date: Sat May 30 13:33:41 1998
Posted By: David Winsemius, MadSci Admin
Area of science: Environment/Ecology
ID: 895875651.Ot

Of the examples you gave, only asbestos fibers would be expected to be measured 
in microns. Microns are units for particles that can be seen with a light 
microscope. A micron is a thousandth of a millimeter, which is in turn a 
thousandth of a meter (about a yard if you live in that backward country, the 
United States of America). Lead and chlorine are atomic sized contaminants, far 
smaller even than viruses, which are in turn far smaller than bacteria. Bacteria 
are typically measured in microns.

Here are sizes that different types of microscopes can "see". Snipped from 
another posting on the MadScie archives:
"Light Microscopes up to about 200 nm (= .2 microns)(about the size of bacteria) 
TEMs to about 0.1 nm (about the diameter of an atom!) and STMs can resolve
features as small as 1/100 of an atomic diameter!!!"

TEM=transmission electron microscope
STM=scanning tunnelling microscope

Snipped from another posting:
"Coxsackie B virus, which you mentioned, has a diameter of approximately 30 
nanometers, or 0.03 microns. "

Another snppet:
"Atomic radii, in angstoms, from Nebergall, Holtzclaw, and Robinson, 
  "General Chemistry", 6th ed, DC Heath, Lexington, MA, 1980:

Lithium  Beryllium  Boron  Carbon  Nitrogen  Oxygen  Fluorine
 1.52       1.11     0.88   0.77     0.70     0.66     0.64    "

(Angstroms are one ten-thousanth of a micron.)
Lead and chlorine in solution are probably a bit bigger than the atoms listed 
above but not by much.

Hope this helps
David Winsemius, MD

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