Field tripping around Boston – MIT Experimental Atmospheric Chemistry course

It’s my fourth year as a TA for our ‘Experimental Atmospheric Chemistry’ undergraduate and graduate course at MIT, and today we have loaded up the department’s van with nitric oxide (NO) and ozone (O3) monitors, a uv radiometer, and three particulate monitors (PM 10, 2.5, and 1.0 um). As part of the ‘Pollution Exposure’ unit, we will synchronize the monitors and drive around Boston noting changes in pollutant levels and keeping notes to identify possible pollutant sources. The field trip is a good time, and this year our class has grown to ten students, which is the biggest class we’ve had since I helped develop the course in 2007 with my advisor Professor Ron Prinn and group alumnus Arnico Panday, now at University of Virginia.

Experimental Atmospheric Chemistry course collage
Experimental Atmospheric Chemistry course collage

We explore tunnels (Boston’s Big Dig provides miles of them), construction sites, urban sites with high traffic congestion, and cleaner beach sites. The students note changes in particulate levels at different sites, which often have distinct particulate size distributions as you would expect from a variety of types of aerosol sources. We follow cars, trucks, and buses of all shapes and sizes. Diesel buses and accelerating vehicles have much higher particulate emissions than clean natural gas buses and stationary vehicles; we might already expect this, but students are able to witness it first-hand and real-time.

Tunnels provide a unique photochemical ‘experiment’. Outside air, under uv light from the sun, has certain levels of pollutants that are created and destroyed by ‘photochemical’ reactions. When this air is swept into a one-way tunnel by the traffic and moved slowly through the tunnel, the tunnel blocks the sun and air is no longer being acted on by uv light, so the photochemical reactions cease. Students can then watch what happens if certain reactions that don’t need uv light proceed (such as NO+O3-> NO2 + O2, which will decrease concentrations of O3) and certain reactions that need uv light are halted (such as NO2 + uv -> NO + O leading to O + O2 + M -> O3 + M, which would have regenerated concentrations of O3). In the tunnels, ozone concentrations decrease because O3 reacts with NO, and because there is no uv light, ozone cannot be regenerated; the students clearly see ozone concentrations fall to nearly zero by the end of long tunnels, such as the Ted Williams Tunnnel in Boston.

The study of atmospheric chemistry is often the study of invisible reactions producing invisible products in the atmosphere, so driving around with instruments and observing these phenomenon real-time have been invaluable teaching tools for students (and myself). Over the semester, the course includes the following sections and field exercises; 1) CO2 and climate, in which students deploy a CO2 monitor to Harvard Forest to understand the carbon cycle, 2) Pollution exposure, in which students monitor their own daily particulate exposure and also observe pollution around Boston as described here, 3) Photochemical cycles, in which a wide range of instruments are deployed to MIT’s Green Building roof, which is the tallest building in Cambridge, and the concentrations of chemicals linked by photochemical reactions are studied in detail, and 4) Isotopes and the carbon cycle, in which students learn the value of the added information provided by measuring the isotopic composition of atmospheric molecules, not just concentrations, and measure the isotopic composition of some atmospheric trace gases. Isotope expert, professor Shuhei Ono, has joined the course and spearheads this fourth topic on isotopes. I have enjoyed helping develop and teach this course, and along with the students I learn something new every year!

Teaching plant biogeography for the EAPS Extreme Weather and Climate course

This week I traveled up to Mt. Washington with this year’s EAPS FPOP (Freshman Pre-Orientation Program) Discover Earth, Atmosphere and Planetary Sciences: Extreme Weather & Climate. It’s the third time I’ve acted as a TA for the program by heading up the flora and fauna section, or what is now more commonly known as “Flora with Laura.”

Describing the vegetation at the Alpine Garden

The 3 day program is Spotlighted on the PAOC website, which describes it as being “designed to provide incoming freshmen with the opportunity to explore the science of weather and climate through an exciting combination of lectures and fluids experiments, providing a glimpse into some of the most interesting and challenging aspects of research in PAOC.

I’ve always be interested in plants. My father (and now one of my sisters) is a forester in the diverse mixed forests of Southern Oregon. The flora of trails I’ve hiked always interested me, especially the relationships between plant communities and regional climate (and even micro-climates) that were obvious even to my untrained eyes. Shrubby grasslands cover convex faces of the hills in Big Sur, CA, while coastal redwoods thrive in the moist and cool concave recesses. The towering forests of the North Cascades, WA are a world apart from the flowering cacti of the Mojave. However, it wasn’t until I took the Field Course in Arctic Science, held at both the University of Alaska, Fairbanks and the remote Toolik Field Station on the North Slopes of Alaska, that I formally learned about the adaptations of plants (and animals) to climate. We focused on different strategies plants employ for survival in harsh environments, specifically to arctic environments.

The material from that course translates beautifully to Mt. Washington because, just as plants adapt to the harsher climates found at higher latitudes, the plants found at different altitudes on Mt. Washington must adapt to increasingly harsher alpine conditions. Therefore, the altitude gradient on a mountain in Massachusetts reflects the latitudinal gradient from Massachusetts to the northernmost reaches of Alaska. Interestingly, many of the species on the summits of New England are also found in northern most Alaska – the alpine mountain top climes are the last refuge of arctic plants that extended to mid-latitudes during the last ice age.

The DEAPS group ascends the Mt. Washington auto road from the base near Pinkham Notch at 2032 ft to the peak at 6288 ft. The students make temperature, wind speed and pressure measurements to note how the weather varies up the mountain on that day. I teach them how to use the plant ecosystems as the key indicator of the year-long weather experienced at different altitudes on the mountain. The presence of plants that are adapted to cold temperatures, short growing seasons, ice and wind abrasion, high uv light, low water and nutrient retention, and other environmental stresses are visual indicators of the harshness of the year-round weather on Mt. Washington. Students note how these hardy plants increase in prevalence as we ascend the mountain, which confirms their lessons in how weather up the mountain also becomes more extreme.

DEAPS group at the summit

Beyond the actual instruction, it’s a unique opportunity to interact with incoming MIT freshman; often we are the first group of MIT students and staff that they interact with upon arrival. Students come from all over the country and the world, and they are eager to start their academic and personal lives at MIT.

How much energy does H2 supply to soil microbes?

I presented a poster at the at the Ecology of Soil Microorganisms conference in Prague, 2011 on the role of soil microorganisms in dominating the fate of atmospheric molecular hydrogen (H2). Recent work has linked atmospheric H2 uptake to a novel high-affinity [NiFe]-hydrogenase expressed in active Streptomyces sp. cells, and is perhaps not driven by abiotic hydrogenases as was previously thought. Consequently, atmospheric hydrogen may be a 60-85 Tg yr-1 energetic supplement to microbes in Earth’s uppermost soil horizon. To understand the role of this supplement to the soil microbial ecology, this work explores the following questions:

  1. What is the importance of atmospheric H2 energy to soil microbial communities relative to carbon substrates?
  2. How might this energetic supplement change with changes in anthropogenic H2 emissions?
Ecology of Soil Microorganisms poster
Ecology of Soil Microorganisms

Is H2 an upper atmospheric tracer?

I presented a poster at the 2010 American Geophysical Union General Assembly on H2 as a “mesotracer.” A rare glimpse into the chemical and dynamical evolution of the Arctic polar vortex is provided by a suite of in situ balloonborne measurements. A set of mesospheric tracers observed in the late vortex validate theoretical mesospheric chemical profiles, which is especially valuable for the case of mesospheric H2. Early vortex mesospheric profiles are constructed to explain mixing in tracer-tracer space. Expanding a model to incorporate three mesotracers, H2, CO, and SF6, instead of only one, will increase our ability to constrain estimates of the amount of mesospheric air that descended to stratospheric altitudes by vortex end.

AGU 2010 - Chemical tracers in the upper atmosphere
AGU 2010 Poster – Chemical tracers in the upper atmosphere

MBL microbial diversity course

Anabaena heterocyst and associated epibiont
Anabaena heterocyst and associated epibiont

In the summer of 2010, I spent six inspiring, challenging, and chaotic weeks at the Marine Biological Laboratory Microbial Diversity Course in Woods Hole, MA. I hoped to take full advantage of the opportunity granted by course directors Steve Zinder and Dan Buckley of Cornell to plunge head on into the world of microbiology. I was eager to learn the theory and hands-on methods to study the microbial world, which has such a profound impact on atmospheric composition, and this course gave me a chance to explore my interests in a way not offered anywhere else. Continue reading “MBL microbial diversity course”

Instrument deployment at Harvard Forest

Instrument deployment to Harvard Forest
Instrument deployment – Harvard Forest

After over a year of designing, building, and testing a custom instrument system to measure fluxes of molecular hydrogen (H2), I deployed the system to the Harvard Forest Long Term Ecological Research site in Petersham, Massachusetts (http://harvardforest.fas.harvard.edu/). With the instrument installed, I will measure hydrogen fluxes for a year to determine the seasonal dynamics of H2 cycling in this mixed deciduous forest, and in particular, to characterize the strong soil sink for atmospheric H2.

The instrument shed was tight, and I was packing a lot of equipment. But the move in day was a successful and fun experience thanks to the help of colleagues at Harvard University.

This short documentary created by fellow PhD student Ryan Abernathey highlights the challenges and excitement of move-in day. But the work has only just begun…

Laura at Harvard Forest from Ryan Abernathey on Vimeo.