AAAR Annual Conference

Last month, October 20-24, second-year master student Hongru Shen (me) and Prof. Andrew Ault traveled to Orlando, FL to attend the 33^rd Annual Conference of the American Association for Aerosol Research (AAAR). Prof. Ault presented the latest research findings of single particle diversity and its impact on heterogeneous reactivity during the SOAS field, which was really exciting.

I presented a poster of my work, elemental and individual particle analysis of atmospheric aerosols from New Delhi, India. Few particulate matter studies conducted in New Delhi have focused on individual atmospheric particles, with most studies confined to bulk particles analysis. The lack of such studies in New Delhi has motivated this work investigating the particle sources and processing in the atmosphere. Both natural and anthropogenic sources were determined.  During this analysis process, I discovered an unexpectedly large number of lead-rich particles in New Delhi – even though lead has been phased out of gasoline since 1998. By further examining the chemical composition, size distribution, and morphological characteristics of these lead-rich particles, all of properties indicate that a poor regulation of lead-acid battery recycling is likely the major source. This is further confirmed by the spatial variability of the lead concentrations.

Presenting these results were extremely rewarding. I was able to show experts in the aerosol field, including our great collaborators, the findings I discovered. I was also very excited to talk with someone from India, during which I further confirmed the two sources of salt particles.

I also served as the student assistance of the AAAR, which is a unique way to interact with these excellent researchers. Meeting several people whose names always appear on papers makes reading a new experience in the future as I can match faces with their names on the page. Overall, AAAR was a fascinating time, which confirmed my determination to work in the aerosol field. And I will be very excited if I can return in the future.

UMBS Field Study - Round 1

Looking up to the top of the 100ft tower

Daniel Gardner (me), Nate May, Professor Kerri Pratt and Professor Andy Ault all traveled to the University of Michigan Biological Station (UMBS) in Pellston, Michigan to begin a summer field campaign studying the size distribution, concentration, and composition of aerosol particles in the region. Also joining us was Professor Steve Bertman from Western Michigan University and Stephanie Schmidt, an REU student from Michigan State University, spending her summer up as an REU student at UMBS.

The main site of the study is the PROPHET (Program for Research on Oxidants: PHotochemistry, Emissions, and Transport), a 100 foot tower reaching above the treetops with a wide variety of instrumentation and lines for pulling gases and particles down to the lab at the base of the tower.

The inside of the PROPHET lab with all current instruments

The gas and particle lines - covered with reflective insulation

Since the groups involved with the study will be analyzing both gases and particles, two separate lines were needed coming down the tower. A glass manifold is already installed on the tower from a previous study, and needed to be thoroughly cleaned after a long winter, as many bugs had flown into the pipeline and died. Cleaning a 100+ foot glass pipeline is no small task. It required a highly advanced piece of technology: a rag with 100 ft of rope tied to either side. Two teams were set up, one at the top of the tower and one at the bottom. The rag was dropped down and pulled back up the tube several times to scrub it clean. A bucket of water was lifted to the top of the tower to clean the rag in between each scrub. While cleaning and reassembling the pipeline, we had to pick up the pace, as a rainstorm was approaching, and it is quite unsafe to be on the top of the tower, as rain can make tower slippery and the descent unsafe.

The insluated copper tube sticking out of Lakeside Lab

The next step was to install a 100ft copper tube for the particle line, which was also a daunting task. The top of the copper coil was attached to a pulley system, and slowly lifted to the top of the tower, while the coil was straightened out. The tubing was secured to the tower with high strength cable ties, and then the entire length was wrapped with foam insulation and reflective tape to keep the temperature inside constant.There aerosol line was brought inside the lab on the ground, where it will connect to a variety of instruments. Only a few were set up so far - a Aerodynamic Particle Sizer (APS) and a Scanning Mobility Particle Sizer (SMPS) - two instruments designed to measure the size distribution of the particles. We will return in the future with many more instruments to add.

We also set up the same set of instruments at another location - at Lakeside Lab - a research facility located on the shore of Douglas Lake at UMBS. We set up another 10 feet of copper tubing to stick out the window of the lab, and connected it to the same instruments (APS + SMPS). This way we can compare the sizes of particles from above the canopy vs particles from the lake.




We would like to thank Professor Bertman for all of his help in setting up all the lines and instruments at the two labs, and Stephanie for monitoring all of the instruments while we are not there!

Daniel Gardner (Left), Stephanie Schmidt (Right)

Stephanie (Left), Professor Bertman (Center), Professor Andy Ault (Right)

Molina Symposium

On May 12, 2014, Prof. Andrew Ault attended the Molina Symposium in La Jolla, CA to honor Professor Mario Molina. Molina is a celebrated chemist and Nobel Prize recipient; he won the Nobel Prize in chemistry in 1995 along with Paul J. Crutzen and F. Sherwood Rowland for their discovery of the role of CFCs (chlorofluorocarbons) in ozone depletion. This symposium took place at the Scripps Institution of Oceanography UC San Diego since Molina moved to UCSD in 2005 from MIT to research the chemical properties of atmospheric particles and the effect of these particles on clouds and climate. At this symposium, Dr. Ault presented a poster concerning the spectroscopic and microscopic analysis of particles from SOAS.

 

Picture of Dr. Ault showing the work of grad student Amy Bondy on particle analysis from the SOAS campaign.

Michigan Geophysical Union Poster Presentation

Graduate student Hongru Shen presented her work on the analysis of atmospheric aerosol particles from New Delhi, India at the Michigan Geophysical Union Meeting at the University of Michigan on April 7.  Several students from the Pratt lab, as well as students from the Earth and Environmental Sciences and Atmospheric, Oceanic and Space Sciences departments, also presented in the poster session.

Welcome to Jessica Axson!

The Ault Lab is welcoming a new member - postdoctoral fellow Dr. Jessica Axson!  Jess received her Ph.D. from the University of Colorado, Boulder in 2012 where she worked in the Vaida group and then spent some time as a postdoctoral fellow in the Prather group at the University of California, San Diego.  We are very excited Jess has decided to leave sunny California and join us here in Ann Arbor!

Congratulations to Amy Bondy!

Congratulations to second-year graduate student Amy Bondy on passing her candidacy exam last week!  She's now officially on her way towards a doctorate!

Raman and Scanning Electron Microscopy Snow Research - March Update

            Exciting renovations are in process at the Ault Lab, which are detailed in the previous February blog post. As Raman instrumentation is sensitive to dust and other particles, it is currently being held in storage. We will be switching focus to scanning electron microscopy for imaging and elemental analysis of snow until renovations are complete.

SEM differs significantly from Raman in relation to our project in two ways: the need for a vacuum and the tradeoffs required for proper imaging. SEM essentially is based around receiving backscatter from an electron beam focused on a sample which cannot be done at ambient pressures. This is particularly problematic for snow samples as they will sublimate at a quick rate in a vacuum. We hope to mitigate the issue through a variable-pressure chamber that will allow usage of only a partial vacuum. Furthermore, a coating such as gold is often required to offset charging of the sample; while coating allows crisp imaging of structures, it masks the sample which prevents elemental analysis. Our plan is to use a black carbon tape to reduce charging and liberal amounts of liquid nitrogen to replace the use of coating.

 Wergin, W.P.

Observations of snow crystals using low-temperature SEM

Journal: Scanning

1995

Along with sublimating, melting is a more significant problem in SEM compared to Raman, we expect to see deformed crystal structures similar to previous SEM snow image research 

We are continuing to read relevant literature on the subject of snow research, with specific emphasis on Dr. Sobron whose interests lie in the potential of Ramman in planetary exploration. In a paper entitled Low-Temperature Raman Spectroscopy of Materials Relevant for Planetary Exploration from the 42nd Lunar and Planetary Science Conference of 2011, he notes that Raman peaks are affected by temperature. Specifically as temperature decreases, peak widths become narrower, peak positions decrease, and intensities weaken in ice crystals. These changes are due to strengthened hydrogen bonding and weakened O-H bonds. As we will be working at temperatures well below freezing, we will need to account for these findings.

Preceding the renovations, we were able to continue gaining experience on Raman using silicon and quartz standards. The peak strengths were strangely muted in comparison to similar spectrum taken previously in the year. However, we were eventually able to successfully have the quartz background peaks to appear after adjusting the laser to a higher setting. Currently we are in the process of scheduling training on SEM and expect to start within one to two weeks.

In the meantime, we are pondering what additional factors must be considered as we continue creating a protocol for Raman analysis. Further research into the usage of the Linkam cooling stage revealed the maximum cooling rate is 30 degrees Celsius per minute. This suggests roughly 2-3 minutes will elapse from the time of placing the snow sample on the stage to final temperature stability at -30 Celsius. We are assuming the time to reach this maximum rate is short, however, we will confirm the speed of cooling once we are fully prepared to return to Raman. Tentatively, we expect to pre-chill the stage within a freezer in order to minimize the sample’s exposure to melting temperatures.

The University’s Undergraduate Research Opportunity Program will be hosting its annual symposium on April 23rd. We hope to present images and preliminary data from both Raman and SEM assuming no unexpected time constraints.  

Congratulations to Daniel Gardner!

Congratulations to Daniel Gardner who officially passed his candidacy exam at the end of April!

First Field Study - Dexter, Michigan

The Ault lab has just begun its first field study! The site is located north of Dexter, Michigan, which isn't too far away from the main University of Michigan campus in Ann Arbor, but it is a good start for field work. The site is owned by the university and is currently operated by Dr. Tim Dvonch, a professor in the Environmental Health Sciences department. The site is covered in several feet of snow, but has a wooden deck raised well above the ground to keep the instruments dry. This field study involves taking a Micro-Orifice Uniform Deposit Impactor (MOUDI) out to the site and measuring the amount and composition of aerosol particles in the air. The MOUDI is placed inside an electrical box to protect it from the environment and has a hole cut out of the top to allow for the aerosol inlet to stick out.
The MOUDI works by using a pump to suck in air and pass it through a series of stages. The size of the holes from one stage to the next and the air flow rate are designed to have only particles of a particular size collide on the substrates. Anything smaller than selected will travel with the air to the next stage. The stages are also rotating - this allows for a uniform deposit of particles, and prevents large piles from forming directly underneath each orifice. On top of the MOUDI is a Cyclone, a specialized device that prevents anything larger than 10 microns from passing through. This prevents bugs or very large dust particles from clogging up all the tiny orifices. The cyclone is very heavy, and requires support or it will fall over with the MOUDI. By drilling another hole in the electrical box and setting the cyclone in the hole, we can stabilize the weight with the sturdy electrical box. The substrates are replaced twice each day for a day set and an overnight set. The substrates are placed in the fridge to prevent anything from happening between collection and analysis, and will be analyzed via SEM, TEM and Raman spectroscopy.
One of Dr. Dvonch's graduate students - Pearl Nathan - is also doing testing at the site, and provided a great deal of help in setting up the instrument. While it is extremely cold, the snowy site is a beautiful location. The study will run from Saturday, March 1st to Sunday March 9th, giving us plenty of samples to analyze and determine the composition of the air out here in Dexter.

Me (Daniel Gardner) with the MOUDI

UMBS Winter Research Meeting

February 21 and 22 brought about the third annual winter research meeting for the University of Michigan Biological Station (UMBS) hosted at the Michigan League. These meetings were created as a way for all the researchers working at the UMBS to meet others, learn about different research projects and to form new collaborations, sometimes between people who would normally not have anything in common. 
The meeting began with an introduction by the director of the station, and was followed by a hand drawn poster session. One of the biggest challenges in science is finding a way to easily and clearly communicate the research you are doing. The people in charge of the UMBS think that one way to make your research simple is to hand draw a poster in under an hour. Then over the course of the conference, people would read over the basic idea of your project on your poster and if they see something interesting, they can approach you to discuss it. This often leads to new projects and advancements in the current one.
Our current project at the UMBS is: Climate and Air Quality Impacts of Greenhouse Gases and Atmospheric Particles in Northern Michigan, and is funded by MCubed, a program that takes three professors from different departments and has them all work together. Our team includes Dr. Andy Ault from environmental health sciences (EHS), Dr. Kerri Pratt from chemistry, and Dr. Eric Kort from atmospheric, oceanic and space sciences (AOSS). Each professor brought one student/post-doc with them to the conference: Daniel Gardner (Ault), Nate May (Pratt), and Dr. Mackenzie Smith (Kort). While the three professors mingled with the other researchers, the students and post-doc took to the paper and made an artistic masterpiece.

Dr. Mackenzie Smith showing off our work of art.

After the poster session, there was a series of presentations, from a wide variety of research fields, ranging from the reproductive cycles of microscopic organisms to harvesting invasive plant life for conversion to biofuel. Once the talks were done, everyone got together and discussed potential projects for the future and who wanted to be involved in each. The big overarching project for the future was to do burn plots: highly control fires designed to burn down small sections of the forest to measure how it affects the air, soil, water, and nearby plant life, as well as to measure all aspects of the regrowth.
The group of three professors - Andy, Kerri and Eric - were the only atmospheric researchers there - the rest were mostly biologists - and several of them were interested in potential collaborations.
Overall, we learned a great deal about the biological station, the people that worked there, and the wide range of projects that can be done in the future!

Lab Renovations!

Exciting changes are happening in the Ault group as one of our labs undergoes some renovations!  We have been working hard the past week to clean up and prep the lab for the construction crew.  Most of the instruments were moved into temporary storage and out of harms way for the duration of the renovation.  Pictured to the right, the large and heavy Raman spectrometer could not be moved and was instead wrapped up and barricaded behind protective layers of tables, freezers, and boxes.  The Raman spectrometer needs to be protected from any dust, bumps, or other hazards of construction.

Above, the future site of our brand new desks and cabinets.  On the right, grad students, Hongru, Dan, Diana, and Becky, taking extra boxes and a lot of packing peanuts out to recycling during the lab cleanup.  We are very excited to be moving into our new lab space within the next couple weeks!  Be sure to check back for pictures when the renovation is complete!

Analysis at the Pacific Northwest National Lab

Analysis at the Pacific Northwest National Lab

This winter, Dr. Andrew Ault and 2nd year graduate student Amy Bondy, along with Dr. Kerri Pratt and 1st year graduate student Eric Boone, traveled across the country to visit the Pacific Northwest National Lab (PNNL). Although we experienced some flying difficulty due to the "Polar Vortex" and a frozen fuel line on our flight out of Detroit, we eventually arrived in Richland, Washington only a day late and after quite a few unexpected tours of airports out west. 

While at the national lab, we used some of the unique instrumentation available there to analyze aerosol samples collected from SOAS. With Alex Lasking as our host, and the help of his postdoc BingBing Wang, we were able to get up and running samples on the computer-controlled SEM (CCSEM) in no time! We were able to capture images, elemental maps (lots of pretty colors!), and get statistical information about the aerosols from many of the SOAS samples. With access to the lab 7 days a week, we were able to collect a ton of data! 

Although we spent almost all our time in lab, we were also able to have some fun in Richland. Cooking dinner and watching movies together in the evenings gave us a way to recharge before heading back to the lab that night. Additionally, the warm weather (up to 55 degrees) and sunshine in the "desert" of Washington was very welcome after the temperatures we left behind in Ann Arbor!

Raman Snow Analysis

Last September, two undergraduate students were fortunate to be invited to a joint project between both Prof. Andrew Ault’s and Prof. Pratt’s research groups, through the University of Michigan Undergraduate Research Opportunity Program. The project intends to establish a protocol for imaging and analyzing snow crystals for climate research, specifically the impurity concentration and distribution in Arctic snow.

We intend to use the Raman spectrometer detailed in the previous December blog post “Raman Installation” for its imaging and elemental mapping capabilities. It is an exciting prospect to be among the first in utilizing Raman on snow crystals, however, we have run into several complications. The Ault group’s Raman spectrometer features a laser filter that can control its intensity. Higher settings generally result in increasing base resolution for imaging. Unfortunately, a high filter setting is a dual-edged sword as the laser will heat up samples. In our test run with the Raman, the laser burnt through the silicon sample several times! We will most likely use a low filter setting despite the base resolution drop.  

Linkam Stage (Placeholder for lab one)

A more immediate complication is the tendency for snow to melt, especially under the Raman’s laser. We’ve made progress in the last two months in finding a way to preserve the snow crystals long enough for Raman analysis. A Linkam cooling stage is in the Ault Lab which will allow us to keep samples at a stable -30°C during imaging. 

The Lab also has a recirculating cooler which will be paired with the Linkam stage once the necessary bath fluids are ordered. Soon after, we will be ready to begin determining parameters for imaging.

Placeholder for Freezer/Snow

The Ault Group has snow that is kept in the new freezers mentioned previously in the blog. It will be used along with natural Ann Arbor snowfall until we are ready to analyze our Arctic snow currently in storage. Hopefully we will continue updating our progress as we come closer to the Undergraduate Research Symposium in April!