ACTRIS-Italy is collecting parallel measurements of atmospheric composition at different altitudes and urbanization contexts in Northern Italy.
According to first analyses, surface concentration of NO2 have decreased in north Italy of about 10% per week during the last four or five weeks4,5. The concentrations of another major air pollutant, the particulate matter (PM10 and PM2.5), have declined too but with large day-to-day variations: after two weeks of lockdown and large reductions in traffic activity in north Italy, PM10 levels above the threshold of 50 mg m-3 are still recorded in several cities of the Po Valley.
The main facility operative within ACTRIS in Northern Italy is “Monte Cimone – Po Valley observatory” (CMN-PV). It is a distributed infrastructure including the GAW and ICOS stations of Monte Cimone (http://www.isac.cnr.it/cimone/) in the northern Apennines, and the two stations of San Pietro Capofiume and Bologna in the south sector of the Po Valley. It is a unique observatory for providing parallel measurements of atmospheric composition at different altitudes and urbanization contexts in the same geographical area. Preliminary measurements at Monte Cimone (2165 m a. s. l.) show reduced submicron aerosol concentrations compared to 2019 (Fig. 1). If confirmed, a negative anomaly with respect to the climatology will proof that the abatement of anthropogenic emissions caused by the lockdown are affecting the composition of the background atmosphere in this region of the world.
Fig. 1. Monthly mean concentrations of accumulation-mode aerosol at Monte Cimone in 2019 and early 2020 (update March 20th).
At the low altitude sites of the observatory (Bologna and San Pietro Capofume), advanced aerosol measurements are set up during intensive observation periods. Currently, a state-of-the-art high-resolution aerosol time-of-flight mass spectrometer (HR-ToF-AMS) is being operated in Bologna (Fig. 2). The instrument provides real-time submicron aerosol chemical composition measurements providing unparalleled detail on the time-resolved PM source contributions including traffic, residential combustion and secondary formation. First observations during the lockdown show that the concentrations of several particulate anthropogenic pollutants – like ammonium nitrate – are still very dynamic in the Po Valley, with a large variability induced by meteorological factors. Accounting for such effects provides baseline knowledge for quantifying the impact of emission changes on PM concentration levels. Probing the complexity of the meteorological and chemical processes linking emissions to concentrations is one of the targets of ACTRIS.
Fig. 2 Time series of the non-refractory chemical components of sub-micrometer aerosol measured by the HR-ToF-AMS in Bologna (preliminary data for the third week of March 2020). “Org”: organic matter; “NO3”: nitrate; “SO4”: sulfate; “NH4”: ammonium; “Chl”: chloride.
International scientific networks and collaborations are of great importance for the empowerment of regional monitoring networks for priority scientific objectives. Further advanced aerosol observations, including multichannel aerosol size and mobility distributions measurements, are being set up in collaboration with the University of Modena, Helsinki and of Eastern Finland.
The established scientific collaborations between CNR and other partners with the EU institutions responsible for satellite Earth observations (EUMETSAT, ASI) will enable to benchmark remote-sensed air quality parameters with the advanced in situ ground measurements carried out by ACTRIS for a more quantitative assessment of the impact of emissions on concentrations and exposure.
In these extraordinary times, scientific research must take a pro-active role to achieve quantitative information on the human impact on the environment, as such information will be key for governance in the upcoming years.
Source: An ACTRIS-Italy contribution to atmospheric monitoring during the COVID-19 lockdown.