D A Frenz1. 1. Multidata LLC, St. Louis Park, Minnesota 55416-5702, USA.
Abstract
BACKGROUND: A recent review article presented conflicting evidence concerning the relationship between the Rotorod Sampler's particle collection efficiency and windspeed. Conventional wisdom holds that its collection efficiency is not affected by windspeed; experimental data paint a mixed picture. OBJECTIVES: This brief addendum will present additional data concerning the relationship between the Rotorod's collection efficiency and windspeed. This information will be contrasted with similar data for the Burkard spore trap. DATA SOURCE: Data obtained from an obscure technical report published by Ogden et al. in 1969 will be assessed. RESULTS: The Rotorod's collection efficiency appeared to be greatest at moderate windspeeds; lower efficiencies occurred at both lower and higher windspeeds. Maximum changes in collection efficiency ranged from 29% to 39% over the six windspeeds employed. The Burkard exhibited the opposite relationship between collection efficiency and windspeed. Collection efficiency was lowest at moderate windspeeds and higher at both lower and higher windspeeds. Maximum changes in collection efficiency ranged from 38% to 142%. CONCLUSIONS: Four principal conclusions emerged. First, these newly rediscovered data demonstrate that the Rotorod's collection efficiency is affected by windspeed. These results appear to overturn the conventional wisdom which holds that this device is insensitive to wind. Second, the Rotorod is less affected by windspeed than the Burkard. The maximum change in collection efficiency uncovered for the former device was 39%; this represented the minimum maximum change for the latter device. Third, the Rotorod and Burkard are affected by windspeed in fundamentally different ways. The former device's collection efficiency is greatest at moderate windspeeds and lower at both lower and higher windspeeds. The opposite effect occurs with the latter device. Last, the previous two findings may partially explain some of the differences in particle recovery by the two devices noted in the parent publication. Figures and equations presented in this addendum indicate which circumstances are likely to produce these differences.
BACKGROUND: A recent review article presented conflicting evidence concerning the relationship between the Rotorod Sampler's particle collection efficiency and windspeed. Conventional wisdom holds that its collection efficiency is not affected by windspeed; experimental data paint a mixed picture. OBJECTIVES: This brief addendum will present additional data concerning the relationship between the Rotorod's collection efficiency and windspeed. This information will be contrasted with similar data for the Burkard spore trap. DATA SOURCE: Data obtained from an obscure technical report published by Ogden et al. in 1969 will be assessed. RESULTS: The Rotorod's collection efficiency appeared to be greatest at moderate windspeeds; lower efficiencies occurred at both lower and higher windspeeds. Maximum changes in collection efficiency ranged from 29% to 39% over the six windspeeds employed. The Burkard exhibited the opposite relationship between collection efficiency and windspeed. Collection efficiency was lowest at moderate windspeeds and higher at both lower and higher windspeeds. Maximum changes in collection efficiency ranged from 38% to 142%. CONCLUSIONS: Four principal conclusions emerged. First, these newly rediscovered data demonstrate that the Rotorod's collection efficiency is affected by windspeed. These results appear to overturn the conventional wisdom which holds that this device is insensitive to wind. Second, the Rotorod is less affected by windspeed than the Burkard. The maximum change in collection efficiency uncovered for the former device was 39%; this represented the minimum maximum change for the latter device. Third, the Rotorod and Burkard are affected by windspeed in fundamentally different ways. The former device's collection efficiency is greatest at moderate windspeeds and lower at both lower and higher windspeeds. The opposite effect occurs with the latter device. Last, the previous two findings may partially explain some of the differences in particle recovery by the two devices noted in the parent publication. Figures and equations presented in this addendum indicate which circumstances are likely to produce these differences.
Authors: Thomas van Hengstum; Danny A P Hooftman; Hans C M den Nijs; Peter H van Tienderen Journal: Aerobiologia (Bologna) Date: 2011-11-19 Impact factor: 2.410