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  Why It's Better?

Standard impact traps, including commercially available models that utilize a clock-driven adhesive tape, capture airborne particulate matter by trapping particles on an adhesive substrate. Capture efficiency is dependent upon the physical attributes of the particles, e.g. size, shape and density, which affect their tendency to move against the airstream and impinge upon the adhesive capture medium. These devices do not generate an attractive force between particulate matter in the airstream and the capture medium; rather, they rely solely on the random collisions of spores and other particulates with the adhesive tape or glass slide. These collisions are caused by centrifugal force imposed upon the particles as the air stream in which they are being carried is forced to deviate around the adhesive tape. Thus, particles of different sizes and densities will be subjected to different forces and capture efficiencies, and physical laws require that air velocities must be very low or capture efficiency will affected. In addition, because of the required low air velocity, these traps must face into the wind. If variable air currents are too low to turn these traps squarely into the wind, capture efficiency will vary as a function of the angle of the orifice and the direction of the wind. Aside from low air volumes and variable capture efficiency, this technology, which is more than 50 years old, provides a very low quality microscopic image because of the adhesive substrate that must be used. This last feature renders these devices essentially useless when attempting to distinguish among closely related species of spores and pollen.

        Comparison to other Spore Traps

The Ionic Spore Trap overcomes all of the limitations described above. The electrostatically charged particles are forcibly attracted to the capture medium, and this assures a very high capture efficiency at very high volumetric air flow rates. High volumetric throughput is essential if spore density (spores per cubic meter of air) is low, otherwise the initial arrival of airborne spores would be missed entirely. In addition, high volumetric air sampling eliminates the need for a wind vane device. In fact, we found that our technology is less efficient when it is incorporated into a wind vane because the device did not respond to changes in wind direction when wind velocity was low. Another crucial advantage inherent with the Ionic Spore Trap is the option of using any of several capture media. We routinely capture particulate matter; including spores, pollen and abiotic particles, on carbon coated scanning electron microscope (SEM) stubs, and these samples can then be viewed without further processing with a SEM. Double-stick tape or plastic cover slips can be applied to the adhesive stubs, and these can be viewed with a conventional light microscope. In addition, we have used cellulose membrane filters as the capture medium. These filters were then incubated in a moist chamber, which allowed spores to germinate, and these were viewed with a SEM as well as a standard light microscope after the membranes were stained with methyl blue (Cotton blue). Finally, assuming that appropriate primers are available, these membranes can be analyzed by Real Time PCR.