Digital Optical Method to quantify the visual opacity of fugitive plumes

摘要

Fugitive emissions of particulate matter (PM) raise public concerns due to their adverse impacts on human health and atmospheric visibility. Although the United States Environmental Protection Agency (USEPA) has not developed a standard method for quantifying the opacities of fugitive plumes, select states have developed human vision-based opacity methods for such applications. A digital photographic method. Digital Optical Method for fugitive plumes (DOM_(fugitive)), is described herein for quantifying the opacities of fugitive plume emissions. Field campaigns were completed to evaluate this method by driving vehicles on unpaved roads to generate dust plumes. DOM_(fugitive) was validated by performing simultaneous measurements using a co-located laser transmissometer. For 84% of the measurements, the individual absolute opacity difference values between the two methods were ≤15%. The average absolute opacity difference for all the measurements was 8.5%. The paired t-test showed no significant difference between the two methods at 99% confidence level. Comparisons of wavelength dependent opacities with grayscale opacities indicated that DOM_(fugitive) was not sensitive to the wavelength in the visible spectrum evaluated during these field campaigns. These results encourage the development of a USEPA standard method for quantifying the opacities of fugitive PM plumes using digital photography, as an alternative to human-vision based approaches.