A Shelter to Protect a Passive Sampler for Coarse Particulate Matter, PM_(10-2.5)

摘要

This work designed and tested a shelter to protect a passive sampler for measuring coarse particulate matter, PM_(10-2.5). The shelter protects the sampler from precipitation and reduces the effects of wind on the deposition of particles to its collection surface. Six shelters were tested in a wind tunnel at three wind speeds: 2,8, and 24 km hr~(-1). Shelter performance was expressed as the ratio of PM_(10-2.5)measured with the passive samplers to that measured with a filter-based dichotomous sampler. For most shelters, the PM_(10-2.5) ratio averaged across wind speeds was well above one (2.4 to 8.5) and was generally dependent on wind speed. However, the PM_(10-2.5) ratio for one shelter, the Flat Plates shelter, was 1.04 with substantially less effect on particle deposition from wind speed. Eight week-long field tests were conducted to compare PM_(10-2.5) measured with a passive sampler installed in a Flat Plates shelter to that measured with a collocated filter-based dichotomous sampler. In these tests, the mean PM_(10-2.5) ratio was 1.29. The linear relationship between PM_(10-2.5) measured passively to that measured with the filter-based sampler had a Pearson correlation coefficient of 0.97 and was not significantly affected by the addition of weekly mean wind speed (p = 0.35). Although temperature was significant in this regression model (p = 0.02), it only improved the relationship marginally. The passive sampler in a Flat Plates shelter offers an inexpensive means to assess ambient PM_(10-2.5) without on-site measurement of wind speed.