Variability between Hirst-type pollen traps is reduced by resistance-free flow adjustment

AbstractDuring an international campaign organized in Munich (Germany) in 2021 to test the performance of automatic pollen traps, we ran four manual Hirst-type pollen traps in parallel. All 4 Hirst-type pollen traps were set and monitored on a weekly basis for the entire campaign to 10 L/min using the same standard hand-held rotameter. Afterwards, a hand-held heat-wire anemometer (easyFlux ®) was used additionally to obtain the correct flow without internal resistance. Uncorrected pollen concentrations were 26.5% (hourly data) and 21.0% (daily data) higher than those obtained after correction with the easyFlux®. After mathematical flow correction, the average coefficient of variatio n between the four Hirst traps was 42.6% and 16.5% (hourly and daily averages, respectively) for birch and 36.8% and 16.8% (hourly and daily averages, respectively) for grasses. When using the correct flow of each pollen trap (i.e. the resistance free anemometer measured flow), for hourly values, th e median standard deviation across the traps for the eight pollen types was reduced by 28.2% (p <  0.001) compared to the uncorrected data. For daily values, a significant decrease in the median standard deviation (21.6%) between traps was observed for 7 out of 8 of the pollen types, (p <  0.05 or lower). We therefore recommend continuing to calibrate Hirst-type pollen traps with standard hand-held rotameters to avoid changing the impacting characteristics of the instruments, but simult...
Source: Aerobiologia - Category: Environmental Health Source Type: research