Difference in particle formation at a mountaintop location during spring and summer: Implications for the role of sulfuric acid and organics in nucleation

Abstract

New particle formation (NPF) has been observed frequently at Storm Peak Laboratory (SPL), a high-elevation mountaintop observatory in Colorado. A detailed analysis of field measurements taken in March and July 2012 at SPL reveals significant and interesting differences in NPF during the spring and summer months. Persistent long-lasting NPF occurred on a daily basis in March but was absent in July. Bursts of ultrafine particles did occur frequently in July, but such bursts were short-lasting and did not show any obvious pattern. A global chemical transport model (GEOS-Chem) coupled with a size-resolved advanced particle microphysics model is used to interpret in-depth this observed nucleation phenomenon. The model captures well the observed persistent daily nucleation events in March and the absence of regional-scale NPF in July. Model simulations indicate that aerosol precursors were dominated by H 2 SO 4 gas in March and by low-volatile secondary organic gases (LV-SOGs) in July, which are consistent with previous particle composition measurements at SPL. The observed persistent daily NPF in March and the absence of regional-scale nucleation in July at SPL indicate that H 2 SO 4 gas plays a much more critical role in the initial nucleation process, although LV-SOGs dominate particle growth in July. Our analysis suggests that the short-lasting bursts of ultrafine particles observed at SPL in July are likely associated with nucleation in subgrid power plant plumes, where concentrations of H 2 SO 4 rather than LV-SOGs are expected to be higher.

Estimating the Lower Limit of the Impact of Amines on Nucleation in the Earth’s Atmosphere

“…However, binary H2SO4-H2O (BHN) [8,9] nucleation cannot fully explain nucleation events observed in the polluted PBL [1][2][3][4]7,10]. While key atmospheric nucleation mechanisms are still a subject of ongoing debates [1][2][3][4][5]7,[11][12][13][14], it is commonly accepted that trace atmospheric species other than H2SO4 and H2O are involved in new particle formation in the Earth's atmosphere and that neutral H2SO4-H2O clusters must be stabilized with ions [12,13], ammonia [14][15][16][17][18][19], amines [20][21][22][23] or organic acids [24][25][26][27][28][29][30][31][32] in order to nucleate. Theoretical formalism of nucleation of H2SO4, H2O and NH3 is commonly known as the Ternary Homogeneous Nucleation (THN) theory [11,[14][15][16][17][18]…”

“…Nucleation is a critically important process that significantly increases concentrations of cloud condensation nuclei (CCN) and impacts the Earth's climate due to scattering and absorbtion of solar radiation [1][2][3][4]. Formation of new nano-and ultrafine particles in polluted areas of the planetary boundary layer (PBL) causes adverse public health impacts, including epidemics of respiratory and cardiovascular diseases, lung cancer and increased overall mortality due to the presence of toxic species in inhaled particles [5,6].…”

Vertical Profiles and Seasonal Variations of Key Parameters Controlling Particle Formation and Growth at Storm Peak Laboratory

“…They showed significant differences in NPF during the spring and summer months at SPL: Persistent long-lasting NPF occurred on a daily basis in March but was absent in July while short-lasting bursts of ultrafine particles appeared frequently in July. While the GEOS-Chem/APM model captures well the observed persistent daily nucleation events in March and the absence of regional scale NPF in July, it is not able to reproduce the short-lasting bursts of ultrafine particles in July (Yu and Hallar, 2014). The short-lasting bursts in July have been suggested to be associated with nucleation in sub-grid power plant plumes (Yu and Hallar, 2014).…”

“…SPL is situated on a 70 km ridge oriented perpendicular to the prevailing westerly winds (Hallar et al, 2011). Yu and Hallar (2014) investigated in detail the NPF during the two contrasting months (March and July, 2012) at SPL, through comparisons of aerosol measurements with model simulations based on a global chemical transport model (GEOS-Chem) coupled with a size-resolved advanced particle microphysics (APM) model. They showed significant differences in NPF during the spring and summer months at SPL: Persistent long-lasting NPF occurred on a daily basis in March but was absent in July while short-lasting bursts of ultrafine particles appeared frequently in July.…”

Source attribution of aerosol size distributions and model evaluation using Whistler Mountain measurements and GEOS-Chem-TOMAS simulations

“…The complexity of air-mass influences at high-elevation sites often makes measurements at these sites difficult to compare to simulations of regional and global models that do not resolve the sub-grid topography. While global models have been used to understand the processes shaping aerosols at mountaintop sites (e.g., Yu and Hallar, 2014), these models have resolution too coarse to explicitly resolve topographic meteorology effects of many mountain peaks. Synoptic meteorology, including advection and subsidence, influences the particles observed at mountain sites (Collaud Coen et al, 2011;Gallagher et al, 2011); however, one may expect chemical transport models to resolve these processes if synoptic meteorology is well represented.…”