A new flow–through directional passive air sampler: design, performance and laboratory testing for monitoring ambient nitrogen dioxide

A new type of passive air sampler for monitoring trace air pollutants in ambient air is introduced. It has a rotatable upper part that can turn into the prevailing wind direction. Pollutants from different directions are transported through a specially–shaped air channel in the upper part and retained on different parts of a sample carousel in the fixed lower part. Pollution sources are trackable by examining the pollutant distribution in the carousel. The design of this new directional passive air sampler (DPAS) is described. Wind tunnel tests show the DPAS responding to wind direction changes at wind velocities as low as 0.9 m s-1. Measurements of wind velocities inside and outside the DPAS revealed good correlation for potential quantitative results. The DPAS was tested at a wind velocity of 2.0 m s-1 using stainless steel meshes impregnated with triethanolamine (TEA) for nitrogen dioxide (NO2). The source direction was clearly identifiable. Further tests and field trials are advocated.