Insight into the Global Distribution and Chemical Composition of PM2.5 from the SPARTAN Global Aerosol Network

The Surface PARTiculate mAtter Network (SPARTAN) is a long-term project that includes characterization of chemical and physical attributes of aerosols from filter samples collected worldwide. This presentation discusses the ongoing efforts of SPARTAN to define and quantify major ions and trace metals found in fine particulate matter (PM2.5). Gravimetrically-weighed filters represent multi-day averages of PM2.5, with a collocated nephelometer sampling air continuously. SPARTAN instruments are paired with AERONET sun photometers to better understand the relationship between ground-level PM2.5 and columnar aerosol optical depth (AOD). We examine the chemical composition of PM2.5 in more than 10 countries between the years 2013 and 2016. Several PM2.5 chemical components varied by more than an order of magnitude between sites. Ammonium sulfate ranged from 1.1 μg m-3 (Buenos Aires, Argentina) to 17 μg m-3 (Kanpur, India [dry season]). Ammonium nitrate ranged from 0.2 μg m-3 (Mammoth Cave, in summer) to 6.7 μg m-3 (Kanpur, dry season). Equivalent black carbon ranged from 0.7 μg m-3 (Mammoth Cave) to 8 μg m-3 (Dhaka, Bangladesh and Kanpur). Comparison with coincident measurements from the IMPROVE network at Mammoth Cave yielded a high degree of consistency for daily PM2.5 (r2 = 0.76, slope = 1.12), daily sulfate (r2 = 0.86, slope = 1.03) and mean fractions of all major PM2.5 components (within 6%). Enhanced anthropogenic dust fractions in large urban areas (e.g. Singapore, Kanpur, Hanoi and Dhaka) were apparent from high Zn:Al ratios. The GEOS-Chem chemical transport model is used to provide further insight into the aerosol processes and emission sources that drive variation in ground-level PM2.5 mass, chemical composition, and the relationship between AOD and PM2.5 at SPARTAN sites.