LIDAR Monitoring of Urban Areas

Abstract

The use of a LIDAR to monitor the air pollution makes it possible to control large city areas and detect the spatiotemporal location of Particulate Matter (PM) emissions sources. LIDAR monitoring is a fast method for estimating the pollution, respectively the mass concentration of PM in the atmospheric ground bioaerosol. The careful study of air pollution becomes especially relevant as the PM are potential carriers of solid-state particles dangerous to health and biologically active components. The present report summarizes our experience [1-3] on how the intricate complex of particles with different content and size found in the aerosol might affect the LIDAR monitoring results on the long distance. LIDAR subject of this study is capable of scanning and mapping the horizontal and vertical aerosol distributions and the transport of air masses with a range resolution along the Line of Sight (LOS) of 30m and a beam divergence of ~1 mrad at operational distances of about 25km [3]. The laser emitter (wavelength of 510.6nm) is a pulsed CuBr vapor laser with a repetition rate of 5-10kHz at a 15-ns pulse duration. The receiving system comprises a Carl Zeiss Jena Cassegrain telescope (aperture of 20cm and a focal distance of 1m), a 2-mm-wide focal diaphragm, an interference filter with a 2-nm-wide passband, and an EMI 9789 photo-multiplier tube operating in a photon-counting mode along the entire operational distance. The receiving system is fully computerized for collecting and processing the LIDAR data using a PCO 1001 1024-channel digital interface system for signal strobing and accumulation. The LIDAR monitoring was calibrated based on the data from a sampling absorber located just below the spot of the LIDAR beam with a flow rate of 100m /h, where the particles are collected on a filter with pore size 3µ m (FILTER-LAB, Material MCE, Lot.180509006).