Prof. Ault elected as Vice-Chair of the Atmospheric Chemistry Working Group for AAAR

Dr. Ault was elected this week as the vice-chair of the "Atmospheric Chemistry" working group for the American Association for Aerosol Research (AAAR). This position is elected across the entire AAAR membership. From AAAR "These leaders are selected for a 2-year rotation, serving as Vice-Chair for the first year and then becoming Chair for the second year. The Chair presides over the WG meeting at the annual conference and then serves on the conference program committee, planning the next year's annual conference." Dr. Ault is excited to provide service to a community he has been involved with for the past decade!

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. 

Aerosol pH Paper Selected for JPC-A Virtual Issue

A recent paper led by Joel Rindelaub and Becky Craig from the Ault Laboratory on measuring the pH of individual aerosol particles was selected for a virtual issue of the Journal of Physical Chemistry - A focused on Atmospheric Physical Chemistry (link). From the journal's website:

"This collection contains 25 papers published in the Atmospheric Chemistry section of the Journal of Physical Chemistry A (JPC A) since 2013. The vision is that this collection will be useful for generating new ideas, pushing existing boundaries, and motivating new research in atmospheric chemistry. Moreover, this Virtual Issue may serve as a basis for assembling or updating a graduate course on atmospheric physical chemistry."
 
Great work Becky and Joel!

Hotspots of Aiborne Lead Identified in Delhi, India (Publication and Press Coverage)

A new article by the Ault Group highlighting airborne lead hotspots in Delhi, India was recently published in Environmental Science and Technology, with the title of "Elevated Concentrations of Lead in Particulate Matter on the Neighborhood-Scale in Delhi, India As Determined by Single Particle Analysis". Professor Ault and first author Hongru Shen worked in collaboration with Prof. Thomas Peters (University of Iowa), Gary Casuccio (RJ Lee Group), and Prof. Naresh Kumar (University of Miami). Soon after the publication, this work was highlighted in a press release by Michigan News and reported on in the Hindustan Times, and Governance Now.

This work provides scientific evidence that emissions from informal recycling operations of used lead-acid battery, may contribute to localized high airborne lead concentrations in Delhi, India. Our collaborators (led by Prof. Kumar) collected the particle samples across Delhi (August - December 2008) using the passive samplers. RJ Lee Group characterized the samples using computer-controlled scanning electron microscopy with energy dispersive X-ray spectroscopy (CCSEM-EDX). During our data analysis at Michigan higher than expected lead-rich particles jumped out and caught our attention. Traditional sources, such as coal-fired power plants, leaded fuel, and resuspended road dust, were excluded after temporal and spatial analysis. With both physical and chemical properties of each single particle, we further confirmed informal recycling operations of used lead-acid battery as the likely source. For more details check out our paper and the press linked above!

MGU Symposium 2016

Bringing together graduate and undergraduate students from the disciplines of earth, oceanic, atmospheric, and space sciences, the Michigan Geophysical Union (MGU) symposium, held on central campus at U of M, was a success again in 2016! Hosted by the Climate and Space Sciences and Engineering (CLaSP) department, this 13th annual symposium fosters collaboration and works to generate interest among the various departments. This year, poster keyword bingo was played to further discussion among students from different programs and fields.

Graduate students Becky Craig and Amy Bondy presented posters at the symposium, as did undergraduate students Sydney Niles and Peter Tirella, all shown in the photos below with their posters. Congratulations to Becky for winning 2nd place in the chemistry section of the poster competition!

Amy Bondy presents on her latest manuscript, sea spray aerosol (SSA).

Sydney Niles presents on secondary organic aerosol (SOA) structure, which she also took to the ACS national meeting this spring.

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Peter Tirella presents his first-ever poster on surface enhanced Raman spectroscopy (SERS).

Becky Craig presents research on her latest publication, pH of aerosol single particles.

The Mobile Lab is Here!

A couple of weeks ago, Dr. Ault and I traveled to Fenton, Michigan to pick up our new Mobile Lab trailer. The trailer is 8.5 ft x 20 ft long and will allow us to embark on field campaigns with all of our instrumentation!

The first field study planned with the mobile lab will be to the University of Michigan Biological Station (UMBS) this July. Next winter, another field study to Kalamazoo, Michigan is planned.

Some of the instrumentation that will be aboard include:

Aerosol Time-of-Flight Mass Spectrometer (ATOFMS)

Chemical Ionization Mass Spectrometer (CIMS)

Ambient Ion Monitor- Ion Chromatograph (AIM-IC)

Dr. Andrew Ault (above) and Ryan Cook (below) in front of the brand new trailer!

In addition to plenty of room for our instruments, the trailer also has a large amount of storage!

We are looking forward to the currently planned field studies as well as future deployments of our mobile lab. This unique setup enables us to study atmospheric chemistry from a much different angle!

Water Center Funds Ault and Pratt Groups to Develop Mobile Laboratory

The Ault Group received a research grant from the University of Michigan Water Center to "advance water research capabilities at the University of Michigan". This collaboration with the Pratt Group will develop a mobile laboratory to to transport state-of-the-art instrumentation for field sampling of atmospheric aerosols produced from wave-breaking on the Great Lakes, a phenomenon we have termed "lake spray aerosol (LSA)" as the freshwater corollary to sea spray aerosol. This research builds on efforts with the Water Center to understand impacts of harmful algal blooms on air quality, in addition to water quality, for coastal communities on the Great Lakes. This research direction has grown in recent years with a general focus characterizing lake spray aerosol (aerosols produced by wave-breaking on the Great Lakes) both in the laboratory and in the field. This exciting project has produced two manuscripts that will be submitted shortly. 

The Lake Spray Aerosol Project and mobile lab to study it have received press from across Michigan in recent months.

The funding for this project was recently highlighted by the University of Michigan Biological Station (UMBS) (link).

In addition the general Lake Spray Aerosol (LSA) project was recently highlighted in the Grand Traverse Record Eagle (link).

We are looking forward to getting out and seeing what the Great Lakes tell us the next time the wind causes waves like this!

Photo Credit: Dave Sanford

New method for measuring pH of aerosol particles

An new article by the Ault Lab detailing a new method to measure the pH of individual aerosol particles was recently accepted by the Journal of Physical Chemistry A. Co-first author Rebecca Craig worked in collaboration with Dr. Joel Rindelaub (co-first author), a recent graduate from the Shepson Lab at Purdue University, and Lucy Nandy, a graduate student from the Dutcher Lab at the University of Minnesota, on the paper titled "Direct Measurement of pH in Individual Particles via Raman Microspectroscopy and Variation in Acidity with Relative Humidity." 

Aerosol particle acidity plays on important role in secondary organic aerosol (SOA) formation and other atmospheric processes, but has traditionally been difficult to measure as sulfate and bisulfate are not distinguishable by most methods used to determine aerosol chemical composition. This work used a Raman microspectrometer to probe the sulfate and bisulfate vibrational modes in laboratory generated aerosol particles, which were atomized from solutions of magnesium sulfate with varying concentrations of sulfuric acid. Using calibration curves relating integrated peak area to concentration for sulfate and bisulfate and their relationship with the acid dissociation constant, activity coefficients and pH could be determined for each aerosol particle.

Particles at ambient relative humidity had measured pH between 0.18 and 0.79. Continued probing of the particles as relative humidity was varied showed that aerosol particle pH increases as a function of increasing relative humidity and yielded pH measurements within the range of -0.68 to 1.33. This is consistent with the -0.5 to 3 range recently reported for ambient aerosol pH in the southeast United States from indirect methods. Future work will expand this method to other acid/base equilibrium systems to cover a wider range of pH, as well as work to apply this method to ambient aerosol particles.

Highlight in the U-M Water Center Fall Newsletter!

On Wednesday, November 18, 2015 the University of Michigan's Water Center sent their quarterly Newsletter in which one of our projects was highlighted related to lake spray aerosol, the freshwater equivalent of sea spray aerosol. Here is the link for those of you who would like to check it out: http://graham.umich.edu/water/newsletter/featured-projects-2015-11#ault-project, and they include a project factsheet as well.