Dissertation Defense
Student: Márcio Matheus Santana Farias
Program: Meteorologia
Title: “Avaliação do desempenho de monitor compacto de médio custo para poluentes atmosféricos na região metropolitana de São Paulo”
Advisor: Profa. Dra. Adalgiza Fornaro - IAG/USP
Judging Committee:
- Profa. Dra. Adalgiza Fornaro - Orientadora - IAG/USP
- Prof. Dr. Leonardo Hoinaski - UFSC
- Prof. Dr. Andrea Cavicchioli - EACH/USP
Abstract: Air pollution monitoring is a necessary tool to ensure public health in urban
environments. Official monitoring networks are not always able to meet the minimum
coverage corresponding to the number of inhabitants, which is the case in Brazil as well
as in the state of São Paulo. Low-cost sensors allow for much more extensive
distribution compared to reference stations, due to their low price, lower infrastructure
requirements and compact size, and they can be used in a broader variety of
applications. However, their measurements generally lack the degree of accuracy and
precision required for regulatory purposes. This study aimed to evaluate the
performance of compact, mid-cost pollutant monitors in the Metropolitan Region of São
Paulo (MRSP). Two Vaisala AQT530 monitors were installed, one on the campus of the
University of São Paulo (Matão-IAG - within the densely urbanized area) and another in
the Morro Grande Reserve (RMG - outside the densely urbanized area) of the RMSP.
Data on meteorological parameters temperature (T), relative humidity (RH),
atmospheric pressure (P) was compared with reference instruments installed on the
same tower of the monitors, while pollutants carbon monoxide (CO), nitrogen dioxide
(NO2), ozone (O3) and particulate matter (PM10 and PM2.5) were analyzed against
different air quality monitoring stations from the São Paulo State Environmental
Company (CETESB). Overall, excellent data completeness was obtained for all the
atmospheric variables measured. The meteorological parameters T, RH and P generally
showed similar values and time series and were highly correlated with the reference at
both sites. The time series and diurnal cycles of the pollutants were similar and showed
lower concentrations, but of the same order of magnitude as those at the reference
stations. It should be noted that PM10 in RMG showed some abnormal data spikes,
probably due to the hygroscopic growth effect under high humidity. In the co-location
study between Matão-IAG and the IPEN reference station for O3, the slope, intercept,
R2 and REQM were 0.71, 3.68 μg/m3, 0.93 and 15.76 μg/m3, showing better
correlation than a previous study with the same model of monitor in Finland (PETÄJÄ
et al., 2021). However, MP2.5 had a slope, intercept, R2 and REQM equal to 0.33, 3.26
μg/m3, 0.45 and 13.96 μg/m3, showing poorer correlation than the same study. When
comparing the measurements between the two study sites, higher T was observed in
Matão-IAG, while RH was lower, indicating heat island effects due to urbanization. CO
concentrations were higher in Matão-IAG (0.33 μg/m3) than in RMG (0.15 μg/m3). O3
showed similar profiles and reached similar peaks around 100 μg/m3 on some days. It is
necessary to install the monitor next to a reference station that measures all the
pollutants in order to obtain more robust conclusions, but in qualitative terms they were
adequate, considering the characteristics of Matão-IAG as a suburban area and RMG as
a forest area.
Keywords: Low-cost sensor, atmospheric pollutants, air quality monitoring network, co-location