D-RISE Summer 2016 Internship

This summer, the Ault lab participated in the Detroit Research Internship Summer Experience (D-RISE) for the third year. Our student, Stephanie Camarena, a rising senior at Cass Technical High School in Detroit, spent the seven week program working on a project measuring the pH of laboratory generated atmospheric aerosols. The D-RISE students were able to attend many events on the UM campus and within the Ann Arbor community over the course of their program, even meeting UM President Mark Schlissel! Check out this link to an article on the D-RISE students and program from the UM Diversity, Equity, & Inclusion website for more information!

Two new articles from joint Ault and Pratt Lab work on freshwater, or Lake Spray Aerosols (LSA), have been accepted to AMT and EST:

• “Lake Spray Aerosol Generation: A Method for Producing Representative Particles from Freshwater Wave Breaking” Nathaniel W. May, Jessica L. Axson, Alexa Watson, Kerri A. Pratt, and Andrew P. Ault, doi:10.5194/amt-2016-115. (http://www.atmos-meas-tech-discuss.net/amt-2016-115/)
• “Lake Spray Aerosol: A Chemical Signature from Individual Ambient Particles” Jessica L. Axson, Nathaniel W. May, Isabel D. Colόn-Bernal, Kerri A. Pratt, and Andrew P. Ault (http://pubs.acs.org/doi/abs/10.1021/acs.est.6b01661)

Through laboratory experiments and a small field campaign, we have examined the relationship of LSA to bubble bursting dynamics (May et al.) and provide the first chemical signature for ambient LSA (Axson et al.). A LSA generator, utilizing a plunging jet, was constructed to create aerosols under isolated conditions from freshwater samples and model salt solutions. 

The LSA generator shown as a (a) schematic and (b) photograph

Systematic examination of model salts, synthetic freshwater, and Lake Michigan sample indicate that LSA is characterized by a larger bubble size distribution, compared to seawater, with a peak near 300 μm and a bimodal aerosol size distribution with a primary mode at 180 nm and secondary mode at 46 nm. The chemical signature for LSA was determined from ambient collected particles on the shore of Lake Michigan during a wave event in 2015 and surface freshwater from the same location run in the LSA generator. LSA composition was show to consist primarily of calcium carbonate and coupled to great lakes water chemistry (Ca²⁺>Mg²⁺>Na⁺> K⁺), making it chemically distinct from sea spray.

Schematic of ambient LSA from wave breaking on Lake Michigan

The study of LSA is needed as models, at present, utilize SSA parametrizations for freshwater systems, which are not accurate for predicting climate properties of LSA. Given the abundance of freshwater lakes globally, this can be a potentially important source of aerosols that may contribute to light scattering, cloud condensation nuclei (CCN) and ice nuclei (IN) concentrations, air quality, and health around the Great Lakes and other bodies of freshwater.