Black Carbon Particles Physicochemical Real‐Time Data Set in a Cold City: Trends of Fall‐Winter BC Accumulation and COVID‐19

Black carbon (BC) plays an important role in climate and health sciences. Using the combination of a year real‐time BC observation (photoacoustic extinctiometer) and data for PM(2.5) and selected co‐pollutants, we herein show that annual BC Mass concentration has a bi‐modal distribution, in a cold‐climate city of Montreal. In addition to the summer peak, a winter BC peak was observed (up to 0.433 μg/m(3)), lasting over 3 months. A comparative study between two air pollution hotspots, downtown and Montreal international airport indicated that airborne average BC Mass concentration in downtown was 0.344 μg/m(3), whereas in the residential areas around Montreal airport BC Mass values were over 400% higher (1.487 μg/m(3)). During the numerous snowfall events, airborne BC Mass concentration decreased. High‐resolution scanning/transmission electron microscopy with energy dispersive X‐ray spectroscopy analysis of the snow samples provided evidence that airborne BC particles or carbon nanomaterials were indeed transferred from polluted air to snow. During the COVID‐19 lockdown, the BC concentration and selected co‐pollutants, decreased up to 72%, confirming the predominance of anthropogenic activities in BC emission. This first cold‐climate BC data set can be essential for more accurate air quality and climate modeling. About one‐third of the Earth's land surface receive snow annually, the impact of this study on air quality, health and climate change is discussed.