Tactic and strategic management and policing of atmospheric pollution in México, specifically by particulate material (PM) from mobile sources (internal combustion powered vehicles), critically requires state-of-the-science technologies due to the problem's complexity including its public health dimension. The authors consider that proper decision making on the problem would benefit from permanent revision on currently employed PM monitoring and measurement systems and also the effort to improve them. These later currently offer information on O(10^0) ultraviolet-visible-infrared (UV-VIS-IR) spectral bands at O(10^0) spatial resolutions and O(10^1) in [min^-1] temporal resolutions. In contrast, they propose the novel use of acousto-optic tunable filter (AOTF) spectrometry to study PM in atmospheric suspension, capable of offering information on O(10^2) UV, VIS, or IR spectral bands at similar or better spatial and temporal resolutions. The potential of AOTF spectrometry towards PM assessment is clear and the objective is to explore its usefulness.
TopIntroduction
Particulate material (PM) in atmospheric suspension monitoring is crucial in big cities (i. e., Megalopolis and sub-urban areas), regarding both tactical and strategic environmental and epidemiological governmental policing. One of the main causes of PM pollution is the use of internal combustion vehicles operating in high densities over constrained vehicular traffic networks (Molina et al., 2019). Even though the push for alternative automotive vehicular power plants is strong, with hybrid electric-internal combustion vehicles leading the front, it is clear that we will have to deal with the impact of internal combustion as one of the most important automotive energy sources for decades still to come. Thus, Universidad Politécnica de Querétaro (UPQ) and associate institutions to this research proposal have the call to assist within their capacities to the management of subjects related to PM pollution, and its effects on human health and society. The main PM monitoring methods used in México are based on Beta radiation attenuation instrumentation, in order to measure its concentration (Molina et al., 2019; Red Automática de Monitoreo Atmosférico de la ZMVT, 2019). These instruments are reliable and accurate, but their sampling frequency is hourly at best, and in most cases the logistics required for deployment and implementation better functions at ground level or close to it. Moreover, they only assess PM2.5 and PM10 concentration, not being able to assess on critical information such as PM physico-chemical speciation/reactivity and epidemiological relevance. On the other hand, there is instrumentation that in some cases can give information closer to real time, and at different levels above ground on PM concentration, such as the Moderate Resolution Imaging Spectroradiometer (MODIS), mounted on the Terra-Earth Observing System-EOS satellite (Just et al., 2015), solar spectrometers/photometers (Volkova et al., 2018), and Light Imaging Detection and Ranging -LIDAR- devices (Hair et al., 2008). These instruments measure particulate material parameters by aerosol optical depth (AOD) in the atmosphere via the physical principle of comparative radiance/irradiance at different atmospheric column heights respect to ground level. Within this context, a more general denomination for PM in atmospheric suspension would be aerosols in atmospheric suspension, since it considers its nature of molecular agglomerates beyond their current material physical state. Atmospheric Aerosol Optical Depth measured in satellites such as the one carrying MODIS and other means represent the fundamentals of global climatological monitoring systems such as the World Climate Research Program (Holben et al., 2001; Van Donkelaar et al., 2010); and have also recently been used specifically for PM-aerosol monitoring in México City, as reported by (Just et al., 2015). Unfortunately, measurements in these systems are limited to a few spectral bands for each available spatial resolution. For example: bands 1 through 7 and 20 (MODIS bands and spectral ranges, 2019), that is, O(10^0) spectral bands are used at 10 and 3 km (at nadir) spatial resolution above ground, and a 12 min^-1 temporal resolution for atmospheric aerosol study by MODIS (MODIS aerosol product information, 2019a; MODIS aerosol product information, 2019b).