On an empirical relationship between SO2 concentration and distance from a highway using passive samplers: a case study in Shanghai, China.

In this paper, field measurements were performed to determine SO(2) concentration gradients from a highway in Shanghai using passive samplers. It was demonstrated that passive sampling method is a cost-effective and convenient way to monitor specific gaseous pollutants at small scales over long sampling periods in air quality studies. Using function fit analysis for the measured results, a shifted power-law relationship had been found between SO(2) concentration and the distance from a highway. Accordingly, an empirical shifted power-law model was developed for describing and predicting the SO(2) gradients near a highway, in which k is the only parameter and named as diffusion attenuation coefficient. There was a surprisingly significant negative correlation between known SO(2) concentration at reference point (C(0)) and diffusion attenuation coefficient (k). By the correlation equation of C(0) and k, appropriate value of k could be calculated with measured C(0). Therefore, the empirical shifted power-law model developed in this study could be practically and conveniently applied for predicting the SO(2) distributions near a highway with known C(0).