PSU McNair Scholars Online Journal


Air -- analysis


To make air quality monitoring accessible to a broad range of people (i.e. consumers, educational groups, and environmental activist) a low-cost method for sampling nitrogen dioxide (NO₂) was modeled after the Palmes and Gunnison diffusion samplers. This article describes the results of using cost-effective passive diffusion tubes for measuring NO₂ in outdoor environments. Samplers are compared against a collocated chemiluminescence (active) monitor in a gas exposure chamber for concentration of NO₂ between 10 and 200 ppb/v (parts per billion per volume). In these calibration experiments diffusion samplers had strong correlation to the active monitor, R2 = 0.94 for a one week sample interval, and a R2 = 0.91 for a two week sample interval. A four week study was conducted with a collocated active monitor and a total of 42 samplers. The samplers were divided into 6 groups and exposed in one week and two week intervals under environmental conditions: temperature 18 - 31°C, relative humidity 27 - 57 %, wind speed 0.4 - 3 m/s, and NO₂ concentration 2 - 22 ppb/v. The precision, calculated as the relative standard deviation, for the one week sample interval was found to be 8.2%, and for the two week sample interval 20.2%. Three cleaning methods of exposed samplers are compared in order to identify bias in reusing components. Using the best cleaning method the mean NO₂ absorbance of a dry sampler is 1.3 ± 0.4 ppb/v as opposed to a zero absorbance for unused samplers.

Faculty Mentor: Linda George



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