Development and evaluation of a high-volume dichotomous sampler for chemical speciation of coarse and fine particles

This study presents the development and field evaluation of a compact high-volume dichotomous sampler (HVDS) that collects coarse (PM2.5–10)(PM2.5–10) and fine (PM2.5)(PM2.5) particulate matter. The key features of this device is the utilization of a round nozzle virtual impactor with a 50% cutpoint at 2.5μm aerodynamic diameter, operating at a high inlet flow rate (1000lmin-1) with a calculated Reynolds number of approximately 1.1×1051.1×105. In its primary configuration as tested, the sampler size-fractionates PM10PM10 into coarse and fine fractions with a minor flow ratio of 10% (minor/total flow rate), with major and minor flow rates of 900 and 100lmin-1, respectively. Performance evaluation for concentration enrichment was conducted with a 4% minor flow ratio (40lmin-1 minor flow) as well. Tests demonstrated near ideal results at both 10% and 4% minor flow ratios, indicating enrichment to be independent of minor flow rates within the range evaluated. Reasonable agreement was found between the new sampler and collocated Partisol and MOUDI for ambient measurements. A tandem virtual impactor super-concentration system was also tested with the 1000lmin-1 virtual impactor followed by a 100lmin-1 round nozzle virtual impactor and proved to be an efficient system to achieve higher concentration enrichment of ambient particles up to 180 times ambient levels. Investigation of the effect of different ambient parameters like RH and wind speed on coarse PM concentration corroborates results from earlier studies. The HVDS is an effective system to collect coarse and fine PM simultaneously, allowing for comprehensive standard chemical analyses over short sampling intervals.