Nearly five-year continuous atmospheric measurements of black carbon over a suburban area in central France

Atmospheric black carbon (BC) concentration over a nearly 5 year period (mid-2017-2021) was continuously monitored over a suburban area of Orleans city (France). Annual mean atmospheric BC concentration were 0.75 +/- 0.65, 0.58 +/- 0.44, 0.54 +/- 0.64, 0.48 +/- 0.46 and 0.50 +/- 0.72 mu g m(-3), respectively, for the year of 2017, 2018, 2019, 2020 and 2021. Seasonal pattern was also observed with maximum concentration (0.70 +/- 0.18 mu g m(-3)) in winter and minimum concentration (0.38 +/- 0.04 mu g m(-3)) in summer. We found a different diurnal pattern between cold (winter and fall) and warm (spring and summer) seasons. Further, fossil fuel burning contributed >90 % of atmospheric BC in the summer and biomass burning had a contribution equivalent to that of the fossil fuel in the winter.Significant week days effect on BC concentrations was observed, indicating the important role of local emissions such as car exhaust in BC level at this site. The behavior of atmospheric BC level with COVID-19 lockdown was also analyzed. We found that during the lockdown in warm season (first lockdown: 27 March-10 May 2020 and third lockdown 17 March-3 May 2021) BC concentration were lower than in cold season (second lockdown: 29 October-15 December 2020), which could be mainly related to the BC emission from biomass burning for heating. This study provides a long-term BCmeasurement database input for air quality and climate models. The analysis of especially weekend and lockdown effect showed implications on future policymaking toward improving local and regional air quality as well.

Automated summary

Continuous monitoring of atmospheric black carbon (BC) concentration was conducted in a suburban area of Orleans city, France, over a period of nearly 5 years (mid-2017-2021). The annual mean BC concentration ranged from 0.48 to 0.75 μg/m³, with seasonal variations and higher concentrations during winter. Fossil fuel burning contributed over 90% of atmospheric BC in summer, while biomass burning had a similar contribution in winter. The study also analyzed the impact of COVID-19 lockdowns on BC concentrations, showing lower levels during warmer lockdowns compared to the colder one.