Study Of The Aerosol Optical Absorption Coefficient Of On-line Detection Device Based On Photoacoustic Spectroscopy

Atmospheric aerosol particles are an important part of the earth atmosphere system,through scattering solar radiation,absorbing the earth’s radiation and the interaction with the clouds to change global climate.At the same time,aerosols is the main causes of haze.It is an important object of environmental monitoring.Haze not only affects human health,but also seriously affects the environment visibility.Climate forcing and visibility depend on optical properties of aerosols.Therefore,it is very important to accurate measure the optical absorption properties of atmospheric aerosols.Photoacoustic spectroscopy is a new method for detection trace gas,which can directly make online detection of aerosol particles in natural state,without the need for particles separation.And it is insensitive to light scattering.Based on the theory of photoacoustic spectroscopy technology,a small-size photoacoustic detection device for measurement and calibration of outdoor atmospheric aerosols absorption coefficient was developed.By designing a high performance photoacoustic cell,which has high Q value and make the resonant frequency not easily affected by the environment temperature and humidity,eliminating the s necessity of regular calibration;through the inhibition of system noise,effectively improve the system sensitivity and lower detection limit;and analyzes the miniaturized device calibration and overall system performance.The main innovation points of this paper as follows:: 1.A small photoacoustic instrument was developed which can be used in the measurement and calibration of optical absorption coefficienthe of atmospheric aerosols.Compared with the conventional photoacoustic systems,we used the data acquisition card instead of the function generator.In data processing,we used the high-speed data acquisition card to replace the lock-in amplifier.2.The high performance photoacoustic cell was designed,which can ensure that the resonance frequency is not affected by the ambient temperature and humidity,and the necessity of the regular calibration of the photoacoustic cell is removed.3.In the aspect of noise processing,we reduced the absorption noise of the windows,and used the muffler to reduce the interference of environmental noise,and reduce the system’s noise,improve the system sensitivity and reduce the detection limit.4.In terms of device calibration,compared with the conventional method using standard gas to calibration PA cell,we used indoor air as calibration gas,and the carbon dioxide in the indoor air as the calibration absorption component.The buffer gas used in the calibration and in the outdoor measurement are basically same,so we have a more true and accurate result,without additional preparation standard gas.5.We put forward a traceability system for the photoacoustic instrument and evaluated the instrument’s uncertainty of measurement.