Retrieval of the Depolarization Ratio of Graphite Particles Using an Aerosol Chamber

Abstract. This study derives the intrinsic depolarization ratio of graphite particles using a custom-built near-field polarization light detection and ranging (LiDAR) system combined with an aerosol chamber. To minimize the inherent geometric overlap problem in typical LiDAR systems, the receiver and chamber were separated by 30 m and signals were acquired at ultrahigh spatial resolution (0.03 m). Pure graphite particles and fugitive graphite particles collected from a steel plant were individually injected into a standardized chamber using a dust feeder. Parallel and perpendicular polarized backscatter signals were then measured at a wavelength of 532 nm. Background aerosol signals in the acquired raw data were eliminated through signal preprocessing and a correction algorithm. Ultimately, the intrinsic depolarization ratio was calculated as 0.15 ± 0.01 for pure graphite and 0.16 ± 0.03 for mixed particles collected from the steel plant. The results are statistically consistent (within the margin of error). The derived optical indicators provide a scientific foundation for the future development of remote monitoring technologies that can measure fugitive dust originating from steel plants in real time.