Variation in global chemical composition of PM[subscript 2.5]: emerging results from SPARTAN

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Norford, Leslie Keith, Wang, Chien
• Other Authors: Massachusetts Institute of Technology. Center for Global Change Science, Massachusetts Institute of Technology. Department of Architecture
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Copernicus GmbH 2018
• Subjects: Argentina; Aerosol Robotic Network
• Online Access: http://hdl.handle.net/1721.1/114191

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 paper discusses the ongoing efforts of SPARTAN to define and quantify major ions and trace metals found in fine particulate matter (PM[subscript 2.5]). Our methods infer the spatial and temporal variability of PM[subscript 2.5] in a cost-effective manner. Gravimetrically weighed filters represent multi-day averages of PM[subscript 2.5], with a collocated nephelometer sampling air continuously. SPARTAN instruments are paired with AErosol RObotic NETwork (AERONET) sun photometers to better understand the relationship between ground-level PM [subscript 2.5] and columnar aerosol optical depth (AOD). We have examined the chemical composition of PM[subscript 2.5] at 12 globally dispersed, densely populated urban locations and a site at Mammoth Cave (US) National Park used as a background comparison. So far, each SPARTAN location has been active between the years 2013 and 2016 over periods of 2-26 months, with an average period of 12 months per site. These sites have collectively gathered over 10 years of quality aerosol data. The major PM[subscript 2.5] constituents across all sites (relative contribution±SD) are ammoniated sulfate (20%±11%), crustal material (13.4%±9.9%), equivalent black carbon (11.9%±8.4%), ammonium nitrate (4.7%±3.0%), sea salt (2.3%±1.6%), trace element oxides (1.0%±1.1%), water (7.2%±3.3%) at 35% RH, and residual matter (40%±24%). Analysis of filter samples reveals that several PM[subscript 2.5] chemical components varied by more than an order of magnitude between sites. Ammoniated sulfate ranges from 1.1μg m[superscript -3] (Buenos Aires, Argentina) to 17μg m[superscript -3] (Kanpur, India in the dry season). Ammonium nitrate ranged from 0.2μg m[superscript -3] (Mammoth Cave, in summer) to 6.8 μg m[superscript -3] (Kanpur, dry season). Equivalent black carbon ranged from 0.7μg mp[superscript -3] ...