Seminar

Abstract

Atmospheric models indicate that black carbon (BC) aerosol has substantially different atmospheric impacts and spatial distributions depending on how it is mixed with other species. Measurements in the last decade using single-particle techniques have dramatically increased our understanding of the degree to which BC is mixed with other material and the timescales on which this mixing occurs. There are fewer direct measurements of the impacts the BC mixing state has on the resulting mixed particle properties, and most focus on laboratory-generated BC proxies. Here I present recent ambient measurements examining the relationship between BC mixings state and aerosol optical and hygroscopic properties. I will show results from several field campaigns featuring simultaneous measurements of BC mixing state by a single particle soot photometer and optical properties using photoacoustic and filter-based absorption measurements. Second, I describe a method for directly measuring BC hygroscopicity and mixing state simultaneously and show results for measurements made at an urban site in the United Kingdom. The collection of observations shows only a limited impact of BC mixing state on bulk aerosol optical properties but a clear relationship with measured BC hygroscopicity. To conclude I will discuss the implications of the results and also briefly describe some upcoming measurements investigating the impacts of BC and BC mixing state on clouds.