Hourly tropospheric ozone (O3) began to be measured in the Los Andes county, Valparaíso region, in March 2018 (SINCA 2020). After almost 3 years of monitoring, it can be observed that this county presents the highest levels of atmospheric pollution by ozone than in all of Chile. Indeed, from the following graphs made with OpenAir-Project software, it is observed that the maximum daily concentrations of the 8-hour moving average exceeded the ozone air quality standard (DS 112/2003) for several days during the years 2018 , 2019 and so far in 2020.
Ozone is a pale blue, irritating and pungent gas, very oxidative. Ozone can irritate the respiratory system, causing coughing, throat irritation and / or an uncomfortable chest sensation. Ozone can reduce lung function and make normal deep, vigorous breathing more difficult. Ozone can make asthma worse. When ozone levels are high, more people with asthma have attacks that require medical attention or the additional use of medications. Ozone can inflame and damage the cells that line the lungs. Finally, high levels of tropospheric ozone produce significant damage in agriculture, generating fewer seeds and fruits.
In general, tropospheric ozone is formed in the atmosphere insitu by photochemical reactions from the precursors nitrogen oxides (NOx) and volatile organic compounds (VOCs) in the presence of higher solar radiation; These NOx are emitted mainly by diesel and thermoelectric mobile sources that use fossil fuels, and on the other hand, VOCs come mainly from gasoline mobile sources, the chemical industry and tree respiration (mainly isoprene and terpenes).
But where do those precursors who arrive in the Los Andes county come from?
We believe that most of the NOx comes from the Santiago Metropolitan Region basin and / or from thermoelectric plants and industries in the Valparaíso Region, since the number of vehicular sources in the Los Andes and San Felipe counties are low compared to larger counties. On the other hand, VOCs would be emitted mainly by agricultural plantations and forests in the Los Andes and San Felipe counties, and would probably also travel from the Metropolitan Region basin. From the ozone pollution rose graphs generated with OpenAir-Project software for the sampling period, it can be seen that the highest ozone levels occurred during the spring and summer seasons, where the wind blew mainly from the south-west towards the monitoring station, with values close to 3 to 6 m / s. It is also observed from the cycle graph that the highest concentrations of ozone occurred around 5:00 p.m. in the Los Andes county, approximately coinciding with the highest wind speeds. The maximum temperatures occurred around 3:00 p.m.
It can be concluded that, if these high levels of tropospheric ozone contamination are maintained for a third year, the Los Andes county could be declared as a Saturated Zone, and therefore, an Atmospheric Decontamination Plan (PDA) will be required for this county. As a consulting company, we recommend carrying out photochemical modeling in the area and installing NOx (NO and NO2), total hydrocarbon (HCT) and solar radiation monitoring stations in Los Andes to study the formation of this photochemical ozone smog in more detail.
In 2009, engineers who today are part of www.particulas.cl, carried out photochemical modeling (WRF / CMAQ) and monitoring campaigns of chemical species of VOCs in the O’Higgins Region, since in those years several communes of that region were zones saturated by tropospheric ozone. The highest levels of ozone were recorded in the pre-cordilleran communes and in the Rancagua valley.
