RESUMO
The sanitary measures implemented to control and prevent an increase in infections due to the COVID-19 pandemic have produced an improvement in the air quality of many urban areas around the world. We assessed air quality during the COVID-19 pandemic for particulate matter (PM2.5 and PM10), NO2 and O3 in in metropolitan area of Lima, Peru between pre-lockdown period (February 1 and March 15 of 2020), historical period (March 16 to April 30 2017-2019) and lockdown period (March 16 to April 30, 2020). The complete national lockdown that was implemented in Peru produced statistically significant reductions in the in-air pollutant (PM10 (-40% and -58%), PM2.5 (-31% and -43%) and NO2 (-46% and -48%)), as recorded by the by the ground-based air quality monitoring network throughout the metropolitan area, compared with the corresponding concentrations for the previous weeks and over the same period for 2017-2019. Analysis of the spatial Distribution of satellite data also show decreases in the concentrations of PM10, PM2.5 and NO2 as a result of the containment measures and suspension of activities implemented by the Peruvian government. The concentrations of O3 significantly increased (11% and 170%) as a result of the decrease in the concentration of NO2, confirming that the study area is a hydrocarbon-limited system, as previously reported. The results obtained contribute to the assessment by the regulatory agencies of the possible strategies of control and monitoring of air pollution in the study area. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11869-021-00990-3.
RESUMO
The temporal and spatial trends in the variability of PM10 and PM2.5 from 2010 to 2015 in the metropolitan area of Lima-Callao, Peru, are studied and interpreted in this work. The mean annual concentrations of PM10 and PM2.5 have ranges (averages) of 133-45 µg m-3 (84 µg m-3) and 35-16 µg m-3 (26 µg m-3) for the monitoring sites under study. In general, the highest annual concentrations are observed in the eastern part of the city, which is a result of the pattern of persistent local winds entering from the coast in a south-southwest direction. Seasonal fluctuations in the particulate matter (PM) concentrations are observed; these can be explained by subsidence thermal inversion. There is also a daytime pattern that corresponds to the peak traffic of a total of 9 million trips a day. The PM2.5 value is approximately 40% of the PM10 value. This proportion can be explained by PM10 re-suspension due to weather conditions. The long-term trends based on the Theil-Sen estimator reveal decreasing PM10 concentrations on the order of -4.3 and -5.3% year-1 at two stations. For the other stations, no significant trend is observed. The metropolitan area of Lima-Callao is ranked 12th and 16th in terms of PM10 and PM2.5, respectively, out of 39 megacities. The annual World Health Organization thresholds and national air quality standards are exceeded. A large fraction of the Lima population is exposed to PM concentrations that exceed protection thresholds. Hence, the development of pollution control and reduction measures is paramount.
