Increasing trends (2001–2018) in photochemical activity and secondary
                        aerosols in Santiago, Chile

Menares, Camilo; Gallardo, Laura; Kanakidou, Maria; Seguel, Rodrigo; Huneeus, Nicolás

doi:10.1080/16000889.2020.1821512

Cited by 16 publications

(8 citation statements)

References 94 publications

(157 reference statements)

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“…8a and 8c), consistently with observations and the literature (e.g. Menares et al, 2020), due to a more balanced VOC/NO x ratio than in the western area. At Independencia (center Santiago), the VOC/NO x ratio at emission is between 1:1 and 2:1 on average.…”

supporting

confidence: 91%

Referee comment on acp-2020-1249

2021

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Central Chile faces atmospheric pollution issues all year long, in relation with elevated concentrations of fine particulate matter during the cold months and tropospheric ozone during the warm season. In addition to public health issues, environmental problems regarding vegetation growth and water supply, as well as meteorological feedback are at stake. Sharp spatial gradients in regional emissions along with a complex geographical situation make for variable and heterogeneous dynamics in the localization and long-range transport of pollutants, with seasonal differences. Based on chemistry-transport modeling with WRF-CHIMERE, this work studies for one winter period and one summer period: (i) the contribution of emissions from the Santiago Metropolitan Area to air pollution in central Chile, (ii) the reciprocal contribution of regional pollutants transported into the Santiago basin. The underlying 3-dimensional advection patterns are investigated. We find that on average for the winter period 5 µg m −3 to 10 µg m −3 of fine particulate matter in Santiago come from regional transport, corresponding to 13% to 15% of average concentrations. In turn, emissions from the Metropolitan Area contribute to 5% to 10% of fine particulate matter pollution as far as 4 • north and 4 • south. Wintertime transport occurs mostly close to the surface.In summertime, exported precursors from Santiago, in combination with mountain-valley circulation dynamics, are found to account for most of ozone formation in the adjacent Andes cordillera and to create a persistent plume of ozone of more than 50 ppb, extending along 80 km horizontally and 1.5 km vertically, and located several hundred meters above ground, slightly north of Santiago. This work constitutes the first description of such an ozone bubble formation mechanism. Emissions of precursors from the capital city also affect daily maxima of surface ozone hundreds of kilometers away. In parallel, cutting emissions of precursors in the Santiago basin results in an increase of surface ozone mixing ratios in its western area. IntroductionMost urban areas in central Chile, including the capital city Santiago, deal with harmful atmospheric concentrations of fine particulate matter (PM 2.5 ) in wintertime (

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confidence: 91%

Referee comment on acp-2020-1249

2021

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“…Consequently, while urban air is mostly a NO x -rich environment, precursors ratios become more balanced, along with the export, to create more favorable conditions for O 3 formation on reaching less urbanized areas. Such a mechanism has been observed for Paris and its suburbs, for instance (e.g., Menut et al, 2000). Export by easterlies occurs less frequently and mostly at night when O 3 cannot be created due to lack of sunlight, which is why the rural area west of Santiago shows smaller O 3 maxima.…”

Section: Summertime Omentioning

confidence: 72%

Seasonal variation in atmospheric pollutants transport in central Chile: dynamics and consequences

Lapere¹,

Menut²,

Mailler³

et al. 2021

Atmos. Chem. Phys.

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Abstract. Central Chile faces atmospheric pollution issues all year long as a result of elevated concentrations of fine particulate matter during the cold months and tropospheric ozone during the warm season. In addition to public health issues, environmental problems regarding vegetation growth and water supply, as well as meteorological feedback, are at stake. Sharp spatial gradients in regional emissions, along with a complex geographical situation, make for variable and heterogeneous dynamics in the localization and long-range transport of pollutants, with seasonal differences. Based on chemistry–transport modeling with Weather Research Forecasting (WRF)–CHIMERE, this work studies the following for one winter period and one summer period: (i) the contribution of emissions from the city of Santiago to air pollution in central Chile, and (ii) the reciprocal contribution of regional pollutants transported into the Santiago basin. The underlying 3-dimensional advection patterns are investigated. We find that, on average for the winter period, 5 to 10 µg m−3 of fine particulate matter in Santiago come from regional transport, corresponding to between 13 % and 15 % of average concentrations. In turn, emissions from Santiago contribute between 5 % and 10 % of fine particulate matter pollution as far as 500 km to the north and 500 km to the south. Wintertime transport occurs mostly close to the surface. In summertime, exported precursors from Santiago, in combination with mountain–valley circulation dynamics, are found to account for most of the ozone formation in the adjacent Andes cordillera and to create a persistent plume of ozone of more than 50 ppb (parts per billion), extending along 80 km horizontally and 1.5 km vertically, and located slightly north of Santiago, several hundred meters above the ground. This work constitutes the first description of the mechanism underlying the latter phenomenon. Emissions of precursors from the capital city also affect daily maxima of surface ozone hundreds of kilometers away. In parallel, cutting emissions of precursors in the Santiago basin results in an increase in surface ozone mixing ratios in its western area.

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“…The decrease in PM 10 concentrations was not significant in 2020 compared to the historical period ( p > 0.01), while the PM 2.5 concentration was significantly reduced ( p < 0.001). These can be attributed to combined local factors such as a decline in mobile sources emissions and relatively similar wind conditions throughout the years.. Another contributing factor is the reduction from precursors of secondary particulate matter, such as NO x , whose neutralization products mainly contribute to the <2.5 μm accumulation fractions of PM ( Menares et al, 2020 ). NO x showed the greatest decreases among all the pollutants studied, which can be attributed to the reduced emissions associated to land traffic, which emit more than 70% of the total NO x in the SMA (private land traffic was reduced by 30–50%) ( ISCI, 2020 ).…”

Section: Resultsmentioning

confidence: 99%

Air pollution and COVID-19 lockdown in a large South American city: Santiago Metropolitan Area, Chile

et al. 2021

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The implementation of confinement and physical distancing measures to restrict people's activities and transit in the midst of the COVID-19 pandemic allowed us to study how these measures affect the air quality in urban areas with high pollution rates, such as Santiago, Chile. A comparative study between the concentrations of PM10, PM2.5, NOx, CO, and O3 during the months of March to May 2020 and the corresponding concentrations during the same period in 2017–2019 is presented. A combination of surface measurements from the air quality monitoring network of the city, remote satellite measurements, and simulations of traffic activity and road transport emissions allowed us to quantify the change in the average concentrations of each pollutant. Average relative changes of traffic emissions (between 61% and 68%) implied statistically significant concentrations reductions of 54%, 13%, and 11% for NOx, CO, and PM2.5, respectively, during the pandemic period compared to historical period. In contrast, the average concentration of O3 increased by 63% during 2020 compared to 2017–2019. The nonlinear response observed in the pollution levels can be attributed to the changes in the vehicular emission patterns during the pandemic and to the role of other sources such as residential emissions or secondary PM.

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Increasing trends (2001–2018) in photochemical activity and secondary aerosols in Santiago, Chile

Cited by 16 publications

References 94 publications

Referee comment on acp-2020-1249

Referee comment on acp-2020-1249

Seasonal variation in atmospheric pollutants transport in central Chile: dynamics and consequences

Air pollution and COVID-19 lockdown in a large South American city: Santiago Metropolitan Area, Chile

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