CAICE Intensive 2011

Just the beginning in our quest to understand complex chemistry impacts on climate……

As I sit here on Thanksgiving morning thinking of all I am thankful for, I think of many things but the CAICE intensive, just completed a little more than one week ago, keeps springing to mind.  We ran a few days longer than we expected, but on November 15, we officially stopped sampling with all instruments.

Due to the dedication of the team of scientists involved in this project, we took full advantage of the suite of measurements to run experiments 24/7 for the final 10 days.  In the final 5 days, thanks to input (and samples) from our biology colleagues, we ran a complete mesocosm experiment, studying how a mixture of bacteria, viruses, and other ocean critters affect the chemistry of the seawater and in turn, these changes affect the chemistry of sea spray.  Our experiments went from “simple” filtered seawater to single “critter” additions covering a range of properties to the full complexity of a real mesocosm bloom. We did all that we set out to do and more with many exciting surprises along the way.  I will say that the one thing that sticks out in my mind is how much easier it is to see instantaneous changes and make sense of the chemical complexity when you know for a fact you are looking at one source, in this case, sea spray.  This study has already helped our group explain critical observations we have seen countless times in field studies but never been able to explain.  It reinforces exactly why we moved the real world to the lab to perform complex chemistry experiments.  I think

Chemical complexity...the soup of bacteria, viruses, protozoa, organics, salts...formed some very interesting aerosols...

we will be able to clearly show how this represents a new approach for  “integrating reductionist and complexity approaches to solve complicated problems”, one of the grand NSF challenges we set out to address.

Everyone is recovering now, but feeling extremely rewarded by all we have accomplished as a collective group.  The fruits of all of our labor will become evident in the coming weeks and months, as we merge all we have found into one set of stories.  I want to personally thank everyone who has been involved in this study, Hlab staff, grad, undergrad, postdocs, faculty, and advisors, for your dedication to this CAICE project.

It has been a wonderful experience, one of the best of my 20 year career, working with everyone involved and I look forward to digging more deeply into the results together.  Today, I am thankful for all we were able to accomplish together–but I can’t help feeling that this is just the beginning of a long and productive scientific journey….

Here’s to hoping everyone has a wonderful Thanksgiving…

Kimberly A. Prather, Director of CAICE (

CAICE Intensive 2011

A Unique Experience…

As I sit down to write this I have just started draining the water from the tank one final time…what an experience the last few weeks have been.  I feel privileged to be the last non-professor to be able to write about my experience during the CAICE intensive for this blog, as in my opinion it is an honor to be able to write the concluding remarks for the group of fantastic undergraduates, graduates and postdocs that took part in this amazing study.  As such though, it is difficult trying to narrow in on one topic to write about from the countless possibilities that have arisen over the intensive.

The author, postdoc Tim Guasco (back, UCSD), is examining single particle mass spectra as they are produced in real time by ATOFMS.

Some of these include:

-What it was like being a postdoc in a field of science that is different from my PhD and trying to learn on the fly, while also teaching about things in which I have more experience than the rest of the group.

– I could also write about how enriching it was to not only be taking part in my first “field” campaign, but also to be part of the group who was tasked with getting the logistics right before the intensive started and be part of the day-to-day running of the experiments.

-Another potential topic might be how amazing it was to be able to take part in such an awesome study with people from not just around the country, but around the world.  There are few chances in most young scientific careers to be able to work in one place with such a diverse group of people.  I was able to learn quite a bit in a rather short amount of time because of the discussions I had with people who all approach the same problem with a slightly different mindset.

The list of topics could go on, however, I am going to focus on how a unique a collaboration this truly was.  In my opinion, large scale collaborations of this type are often overrated.  The idea generally put forth is that big problems in science are now too vast for a scientist from just one field to be tackling on his or her own.  To overcome this, a lot of really great scientists from all different areas and work to conquer the dilemma together.   While this seems like the perfect solution, often times it fails for a variety of different reasons.  These might be difficulty in finding the perfect person for the task at hand, or maybe finding that person but at an institution that is across the country, or also that sometimes other people are just hard to work with.  That might seem like a strange thing to read on a blog that is about a large collaboration, but these feelings of mine are precisely why I feel like the intensive campaign, and CAICE in general, are so unique.

It is very rare to be at a place where there are wonderful atmospheric chemists, physical oceanographers, amazing marine microbiologists, etc.  Also, let us not forget the  40 meter long wave channel that made this all possible.  At a place like this, you can literally walk down the street, see someone from a different field and talk to them about what is going on.  That person might then be able to provide a whole new perspective on the experimental setup and change things drastically for the better.  I know, because a chance encounter just like this happened when our fearless leader, Prof. Kim Prather, happened upon Prof. Farooq Azam from the Marine Biology division at SIO.  Prof. Azam was able to attend one of our daily meetings and his keen and unique insight set us on a completely different and far better course than was originally planned.  Given the one-of-a-kind setting and resources, the only thing that could have doomed us to failure would be conflicts of personality.  Luckily, everyone involved was so excited and proud to be a part of this intensive study that each and every person was willing to help out their fellow colleagues.  Therefore, I am calling this one of those rare large scale collaborations that is actually a success.  And the fact is, what people tend to say is true, the big problems in science in general are too vast for just one field, as such, when large scale collaborations of this type are successful, the knowledge gained is plentiful.  This study made me realize why people hold these collaborations in such high regards, the rare times they work, they are fantastic.

Tim Guasco, Postdoctoral Researcher, Prather Research Group, UC San Diego

CAICE Intensive 2011

Thoughts on Education in the Pursuit of ‘Big Science’

Skip Pomeroy is taking the lead on the educational efforts of CAICE and organizing seawater analysis during the Intensive Campaign.

As the Intensive data collection period finishes its second week, I am struck by the dedication of the researchers and the interdisciplinary nature of the work.  Long hours are being logged.  The range of the instrumentation and techniques, both online and offline, is quite impressive as one enters the Hydraulics Lab.  I have yet to speak to anyone that doesn’t marvel at it a bit.  The interaction between the atmospheric scientists with the physical and biological oceanographers, the algae greenhouse staff, and the undergraduates and graduate students involved in the ocean water chemical analysis indicates the necessity of an interdisciplinary approach to solve complex chemical problems.  This observation then makes me reflect on a trend in our educational system of narrowing the breadth of the curriculum.  Starting with the query, do biologists need all that math or physics, or do biochemists need all of the physical chemistry, do atmospheric chemists need all of that wet chemistry — we have started to tailor the curriculum.  I think this works for some, but when I see the breadth of knowledge brought to bear by this group, I believe that a broad fundamental education creates the foundation upon which scientific inquiries like this can be supported.  I think the students and faculty engaged in this research have to be fearless when it comes to expanding their knowledge or skill sets.  Engineering, computer programming, electronics, fabrication (machining) are just some of the skills that these workers possess or are learning, over and above their expertise in their specific disciplines and areas of instrumental expertise. I am concluding it takes a broad range of people with a broad range of talents and the ability of these groups to successfully interact and communicate that leads to success in the pursuit of big science.

Skip Pomeroy, Department of Chemistry and Biochemistry, UC San Diego

CAICE Intensive 2011

It’s time to grow up!

The author poses with the DASH-SP, which measures particle growth factors at different relative humidities in parallel.

I’m a second-year graduate student on my first field mission and this experience has definitely made me realize how intense the CAICE “Intensive” mission is! I’m in charge of operating the Differential Aerosol Sizing and Hygroscopicity Spectrometer Probe (DASH-SP). The DASH-SP selects aerosol particles by size, splits the aerosol particles into several different channels, and exposes each channel to a different relative humidity. As a result of the humidification, the particles grow due to water uptake onto the particles, and their sizes are measured when they leave the channel. In summary, same-size particles go in, different-size particles come out (due to different relative humidities). The ratio between the size coming out after humidification and the size going in is called the growth factor. Growth factors can tell us how hydrophilic or hydrophobic particles are.

We’re interested in learning more about the properties of sea spray aerosol particles, especially when they are chemically affected by biology. Does the biology’s chemical influence make the sea spray aerosol particles more or less hydrophobic? As a result, do sea spray aerosol particles grow a lot or a little when the air is humid? The answer to these questions can help us in answering other questions about sea spray aerosol particles: How big do they get? How long do they stay in the atmosphere? How much light do they scatter? What does this mean for cloud formation? Ultimately, what does this mean for the Earth’s climate? Are there any feedbacks in the climate from our findings?

I spent the previous month learning about the operation and troubleshooting of the DASH-SP. My research mentor and I had repaired and calibrated the instrument so that it was in perfect condition for the CAICE Intensive mission. When I learned I was going on my first field mission without my research mentor, I was afraid – very afraid! My only source of solace was that the instrument was in tip-top shape and that the field mission only involved turning the DASH-SP on and off every few hours. Little did I know that Murphy’s Law would be in full force for the DASH-SP – after a brief harrowing period of repair, the DASH-SP was back up and running again!

I’m very excited about what my measurements reveal about how sea spray aerosol particles, especially when chemically affected by biology, grow in response to different relative humidities. The true-to-life wave flume and the questions posed by the mission make it unique and will yield important insights on sea spray aerosol.

Wilton Mui, Graduate Student, Environmental Science and Engineering, Seinfeld Research Group, Caltech

The SIO Hydraulics Lab amidst the CAICE Intensive campaign.
CAICE Intensive 2011

What can we learn about atmospheric aerosols from this “Ocean in a Lab”?

The author, Vicki Grassian, with postdoc Andy Ault, conferring about their sampling setup.

It is great to be here as part of the Center for Aerosol Impacts on Climate and the Environment (CAICE) intensive.  I visited this summer when some of the first measurements of the size distribution and size-resolved composition of sea spray aerosol were being made from the wave flume.  At that time, I was excited about the “ocean in the lab” setup to measure aerosol production from sea spray that Kim, Tim and their research groups along with experienced SIO scientists had achieved.  Now coming back for the intensive, I am even MORE excited about the possibilities of what can be learned from this highly unique opportunity for realistic measurements of the physicochemical properties of sea spray aerosol.  It is amazing to see all the different research groups and instruments that are involved in the intensive.  Some of these initial measurements show that the ocean generates a chemically diverse and complex mixture of components that depend on size and marine biogeochemistry.  This ocean mesocosm truly provides for an unprecedented opportunity to better understand the chemistry of sea spray aerosol.

Currently, there are on-line measurements being made of aerosol properties and off-line measurements of substrate deposited aerosols.  These off-line measurements allow us to further explore the chemistry and properties of sea spray aerosol with a wide variety of spectroscopic and microscopic probes.  Some of these off-line measurements are being done during the intensive, while others will be done after the intensive is over.  Dr. Defeng Zhao, postdoc at UCSD, has looked at some of these particles with Raman spectroscopy.  Some of the analysis of his data are straightforward for some inorganic components (e.g. the presence of CaSO4) but other data are more complex (e.g. some of the organics show very interesting spectra –perhaps amino acids?).  Today we will get together to brainstorm some more in analyzing some of these initial vibrational spectra of single particles generated from the wave flume. But even more is planned as Dr. Andrew Ault, a postdoc at the University of Iowa, has been part of setting up the intensive and will be bringing some of these samples back to Iowa for further analysis.

So after the last wave breaks and all the data are collected, assembled and further analyzed, I expect there to be MANY publications that arise providing insights into the chemistry of aerosols and their impact on climate and the environment that were not hitherto possible.

Vicki H. Grassian, F. Wendell Miller Professor of Chemistry, University of Iowa

CAICE Intensive 2011

Single Particle Microscopy and Spectroscopy

The author (back) and Carly Ebben prepare to collect aerosols on microscopy substrates

Many of us can remember looking through a microscope at a young age and being amazed. All sorts of objects and biological “critters” jumped to life when tiny images that were blown up that we had no clue existed when viewing with the naked eye. This feeling is no doubt similar to what physicist Robert Hooke felt in 1665 when he first identified cells with a microscope. At the University of Iowa we use state-of-the-art microscopes and spectroscopic measurements to analyze aerosols at magnifications far beyond what Robert Hooke could have imagined, and we feel a similar sense of awe as we observe the structure and properties of aerosols with these extremely powerful and sensitive techniques.

A scanning electron microscope (SEM) image of a salt particle generated in our ocean-atmosphere chamber this summer.

The microscopy and spectroscopy measurements that we specialize in in the laboratory of Prof. Vicki Grassian at the University of Iowa are providing a unique view of the aerosols being generated during the intensive measurements at CAICE. Techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive x-ray spectrometry (EDX), Raman microscopy, atomic force microscopy, and x-ray photoelectron microscopy, are allowing use to probe the chemical and physical properties of these marine aerosols in extraordinary detail. For example, our TEM measurements can observe details on the scale of less than 1 nm (for reference that is 40,000 times smaller the diameter of a human hair). The black and what image of a particle from preliminary measurements this summer shows the fine detail that can be obtained for our marine particles (in this case a sea spray particle).

In addition to information on the structure of sea spray particles, we can also learn about the chemical composition from EDX combined with both SEM and TEM. The image on the left shows an image of a particle from SEM and on the right we have mapped out the chemical composition of different features with EDX. From this we can see that a sea salt particle isn’t just NaCl, but that the rods and other features contain mixed cation sulfates. This structure of primary NaCl cube and rods of sulfate species has been shown previously by Wise et al. 2007 for samples of resuspended sea water and field collected aerosols. The similarity of our wave flume generated sea spray during background measurements with previous field measurements shows that we are recreating the ocean well in the wave flume. With the background looking good we are excited to see what the biological species we are adding do to the chemical composition of the aerosols we are seeing!

At left, a traditional image of a salt particle as observed using electron microscopy. At right, the same image, with an overlay of chemical composition obtained using an x-ray spectroscopy technique.

Beyond electron microscopy, we are also excited to be working with ambient characterization techniques that don’t rely on introducing the aerosols to vacuum. Confocal Raman microscopy is one such tool we are utilizing to study aerosol properties as they exist in the atmosphere. The Raman spectra will give us information on organic carbon, sulfate, and other species with characteristic vibrations. Taken together the detailed morphology and chemistry of single particles from microscopy, Raman, and other will provide a great complement to many of the online measurements, in particular single particle size and chemistry from the aerosol time-of-flight mass spectrometer (ATOFMS).

Of course, this is just a sneak peek of the analysis we will be doing on aerosols from the wave flume. Expect more exciting results as soon as we get the samples back to Iowa!

Andrew Ault, Postdoctoral Scholar, Department of Chemistry, University of Iowa

CAICE Intensive 2011

Biological Material and Ice in the Atmosphere

Paul DeMott (the author, Colorado State Univ.) had brought along his Continuous Flow Diffusion Chamber which measures how aerosol particles make ice crystals.

The few, the relatively unknown, but the powerful… I am talking about ice nuclei. These particles are special. How special? In air anywhere at any time, these can be the 1 in 100,000 to the 1 in 1 million of all particles. Ten ice nuclei in a liter of air is a relatively large number active particles at supercooled cloud temperatures. Measuring them is a special challenge, but that is what we are here to do – Ryan Sullivan (arrived yesterday to take over for me this week) and I.

Why do we care about particles present in such small numbers? Because it takes only a few ice nuclei per liter of air to initiate an ice-phase precipitation process efficient enough to lead to snow or rain at the surface.  If they transported in sufficient abundance to the upper troposphere, ice nuclei can alter the microphysical and optical properties of cirrus clouds. These particles are associated with some of the most uncertain indirect effects of aerosols on climate.

We know of the strong contribution of mineral and soil dusts as atmospheric ice nuclei. What about direct sources from the massive surfaces of Earth’s oceans? Sparse past data collected over oceans offer intriguing evidence that the oceanic source of ice nuclei can vary by orders of magnitude and may be linked closely to biological processes and biological organisms. The wave flume studies offer the opportunity to directly isolate the source of ice nuclei from sea spray particles (inorganic, organic, biological organisms?) as compared to air of unknown origin present in the oceanic boundary layer at any time, or as compared to what we know is in seawater.

Consequently, we are introducing particles into a flow through chamber that exposes them to conditions that they would encounter in clouds below 0 C, to measure their number concentrations in real-time. I have been surprised at the strength of the source from filtered seawater. We are collecting the activated nuclei onto electron microscopy grids for offline analyses of their elemental composition and morphology. Finally, we are collecting large volumes of air containing the particles for offline analyses of particle freezing spectra at the warmest temperatures below 0C where the real-time method loses sensitivity. My colleagues from the biological sciences, Drs. Tom Hill and Gary Franc of the University of Wyoming, will perform these measurements, as well as chemical and environmental sensitivity experiments to attempt to determine the relative contributions of bacteria, versus all biological, versus all organic particles to ice formation during the offline studies.

Who knows what other great ideas and collaborations will be spawned by the wonderful opportunity presented at this wave flume study?! We look forward to discussions with experimentalists and theoreticians alike.

Paul J. DeMott, Department of Atmospheric Science, Colorado State University

CAICE Intensive 2011

Bridging the gaps between atmospheric physics, chemistry and marine biology

The author, Darius Ceburnis (NUI Galway, at left), and Meilu He (Clarkson) discuss results in real-time.

Organic matter enrichment in sea spray particles was discovered few decades ago, but general wisdom did not recognise it largely due to poor instrumentation to study it. Oceans occupy nearly 70% of the Earth’s surface giving marine atmosphere its special status. Anything happening at ocean-atmosphere boundary has enormous global implications due to its sheer volume. Earth’s climate is dependant on marine atmosphere as is human welfare on marine life.

For a long time marine atmosphere particles were believed to consist only of sea salt and sulphate, both inorganic compounds easy to detect and quantify. Organic compounds in the atmosphere are as variable as the life on Earth making them particularly difficult to study. In a similar way that many bacteria, plant and animal species still remain unknown to science, organic matter in the air is no different.

A monoculture of Duneliella tertiolecta (green algae) is added to the wave tank on Nov 5th to imitate oceanic bloom conditions. This photo was taken before the algae was given time to mix in the tank, and so is highly concentrated.

Significant progress has been made in the last decade identifying organic compounds in the marine atmosphere mainly due to the progress of sophisticated analytical techniques making it possible to peek into individual particles in real time and to quantify the organic material in them. We know that organic particles are present in the air over the oceans and are seeding the marine clouds; we can sometimes generate organic particles in the laboratory, but so much more in unknown about their specific chemical composition, biological origin and ways they are produced and transformed. Quite clearly we have to bridge many gaps between biology, chemistry and physics of the ocean and the atmosphere to understand a coupled system.

MOUDIs and Berner Impactors are collecting samples for offline analysis using a variety of spectroscopic and microscopic techniques.

A unique CAICE facility is a perfect laboratory to study physical and biological processes together by joining forces of different scientific groups. The two groups I am representing are from Ireland (National University of Ireland Galway) and Italy (Institute of Atmospheric Sciences and Climate of the Italian National Research Council) who joined their forces a decade ago and I had a privilege to be part of. The two setups – an online High Resolution Time-of-Flight Aerosol Mass Spectrometer capable of quantifying particles smaller than 1 micrometer in real time and an off-line system consisting of low pressure impactors designed to quantify inorganic particle compounds, water soluble  and water insoluble organic matter as well as Proton Nuclear Magnetic Resonance method for resolution of organic matter species – will give the best quantitative measurement of organic compounds released by different algae species or present naturally in sea water. I am excited as everyone else here to use a wonderful facility and benefit from scientific discussions.

Today we started our first experiment by adding living algae into the huge wave channel which is the closest thing to the real ocean we can have. An exiting week is ahead to find out what those tiny plants of the ocean will reveal in the lab.

Darius Ceburnis, Centre for Climate and Air Pollution Studies, National University of Ireland, Galway

CAICE Intensive 2011

Shedding light on properties of ocean-wave generated particles

Professor Suresh Dhaniyala and Meilu He (Clarkson University) work on deploying their instrument to measure fast size distributions of sea spray particles generated in our ocean-atmosphere chamber.

An ancient Eastern parable describes the difficulty of identifying an elephant in a dark room if you are only able to feel one part of the animal and are unaware of what others in the room are “feeling”.  This parable has parallels in the study of atmospheric aerosol – analysis of small particles suspended in the atmosphere will reveal different stories when examined with different instruments, and scientists working in isolation cannot fully comprehend this system.  The study of atmospheric aerosol often requires scientists from different backgrounds working closely with each other using a wide variety of tools.   The current measurement campaign at the wave channel facility of UCSD provides for such collaboration.

Aerosol particles play a critical role in global climate because of their ability to reflect or absorb sunlight.  On one hand, the particle-light interaction is significantly enhanced when particles grow to become cloud droplets by taking up water vapor, while on the other hand the further growth of clouds droplets to form precipitation can remove aerosol from the atmosphere and significantly decrease aerosol interaction with sunlight.  Characterizing the properties of particles originating from different sources, particularly with respect to their ability to form clouds and precipitate, can help us stitch together a comprehensive picture of the role aerosol particles on global climate.

A replica of a breaking open ocean wave produced in the ocean-atmosphere chamber at the SIO Hydraulics Lab.

In this study, we concentrate on the contribution of one major natural global source of particles – ocean waves.  Particles produced from ocean waves, especially in the presence of biological material, may be especially active as cloud condensation nuclei and ice nuclei.  The wave channel facility at UCSD/SIO produces realistic and repeatable wave conditions that enable measurements at a range of time scales and with a wide variety of physical and chemical probes.  Our contribution to the experiment is in the form of two instruments that provide high time resolution sizing of particles smaller than 1 mm.   Particle size plays a critical role in determining the lifetime of particles, attractiveness to uptake of water vapor and other gas-phase species, and extent of interaction with light. Our measurements of size distributions, combined with data from other probes, will help establish the properties of particles from an important global source of aerosol and we are very excited to see what the data will tell us.

Suresh Dhaniyala, Department of Mechanical and Aeronautical Engineering, Clarkson University

CAICE Intensive 2011

From Molecular to Global Scales

Let’s try this for starters: This is such an amazing project!!! It is environmental molecular science at its best, it bridges the length scale of a molecular bond, which is ridiculously short, with the ocean and the atmosphere, which are ridiculously big, and it brings the real world into a chemist’s lab! You couldn’t have done this kind of stuff ten years ago, and it is beautiful to see it all unfold right in front of our eyes.

Our first spectra of organic molecules on sea spray produced by the breaking waves in the Scripps wave tank (top) and the spectra of organic molecules on the top surface of the Baltic sea (bottom) seem to point us into the right direction.

We are physical chemists from Northwestern University in Evanston, which is the first suburb just north of Chicago. It’s not nearly as nice in San Diego as it is in Chicago during the month of November, but then again … what? No, of course we enjoy it a lot! Franz Geiger is blogging – he is the Irving M. Klotz professor of physical chemistry at NU. What’s physical chemistry? well, it’s physics – and chemistry – combined! There’s even a journal named after it – go check it out at Carly Ebben is a third-year PhD student in the Geiger group  who is also a National Science Foundation Graduate Student Fellow. She  participated in a really cool large-scale study in Southern Finland just last year, and together with samples collected during an equally impressive study in the central Amazon, Carly is now managing the sample acquisition, data collection and analysis, and paper writing for three important field studies, which is the focus of her PhD thesis.

Seaweed on the beach near Scripps pier - can we find the signatures of life on sea spray particles?

Here at the tank, we are studying the chemical composition of sea spray particle surfaces – not the bulk, which contains many, many molecules – but the surface, which houses much fewer molecules. Try it out on a sheet of paper – sketch a cube and fill it with small circles, then count how many are at the surface vs. the interior. In fact, there are so few molecules on the surface of a particle compared to the particle interior that one needs some pretty nifty tools to detect them – that’s what we bring to the CAICE. A second motivation for our studies is that there is a high likelihood that our methods can distinguish surface molecules on sea spray particles prepared in the tank when bugs are absent and when bugs are present – like a signature of life, if you will. This is how it works: We all know that living things contain DNA and proteins, and that the walls of cells are made of phospholipids and sugars. These compounds have a particular handedness, which allows for key molecular processes to occur in the biological machinery that we call ‘life’. A core concept in these biochemical processes is that of molecular recognition – and the handedness we just mentioned plays a key role in it: Imagine the handshake between two people – it typically involves the right hand of one person shaking another person’s right hand – the same happens in molecular recognition. If you were to shake somebody’s right hand by extending your left hand, it’ll be really awkward to say the least – the same is true for proteins and DNA, for which handedness is a key requisite for proper function. But for us, handedness is also an intrinsic marker for the presence of biological material on the particles that are produced at the wave tank, and that is what we are here to study these two weeks. This is a tough problem, because we look for the footprints of life without having to destroy the particles. To do so, we combine particle sampling at the tank with ultrafast laser spectroscopy at Northwestern University – this approach has already allowed us to establish that the particles from the wave tank have organic species on them, and we didn’t have to destroy the particles to learn that.

Andy Ault (Iowa) and Carly Ebben (Northwestern) enjoy working on the samplers.

How do we do it? We began work at the tank one week ago by installing sampling systems that allow us to collect sea spray particles for a certain amount of time and in certain size ranges on Teflon filters – and yes, even though it’s common sense that ‘nothing sticks to Teflon (hence the famous pan)’, the samplers we use can do the job because of some pretty cool particle collection physics. Nevertheless, there are very few particles on the filters, and not many tools can be used to detect them. Our lasers can do it, though, because they are quite special: we can adjust their energies – i.e. colors – to match those of the molecules we are looking for, and  the pulses our laser produce are just one tenth of one millionth of a millionth of a second short, which means we don’t burn up our samples like Han Solo’s blaster did when he sat across Greedo, Jabba’s repo man. We detect the signals with a supersensitive camera chip that’s cooled to the surface temperature of the dark side of the moon – because it’s so cold, unlike the camera in your cell phone, ours picks up really little noise, so it’s perfect for the job (but also much more expensive). Still, the samples we are studying only produce a few photons each minute, and so we need to work carefully.

Assembling the Northwestern University Particle Sampler (NUPS).

So, what do we learn? We learn that while water is of course important in ocean spray, the surfaces of the sea spray particles contain organic molecules, and it is those molecules that interact with the external world and that are important for the climate system. The graphic on the left shows the spectral signature of those organic molecules on particles collected during the crashing of breaking waves inside the wave channel, and how that is in qualitative agreement with what professor Gernot Friedrichs, a colleague of Franz’ in Kiel, Germany, published recently when he applied a similar laser method to the sea surface microlayer he collected on the other side of the planet – the Baltic Sea in Northeastern Europe! Now, here at the wave tank in Southern California we looked at the organic molecules on the surfaces of the sea spray particles, and the Baltic sample was collected by skimming the ocean surface using a boat miles offshore, but doesn’t the good agreement between the data suggest that the organic molecules on the ocean surface are similar to the organic molecules we see on the sea spray? And wouldn’t that suggest that when phytoplankton is present in the ocean, the biomolecules associated with the bugs could be associated with the sea spray particles? And doesn’t that imply that there may be a possibility for a biosphere-atmosphere feedback cycle that would be awesome to understand if we want to understand the complexity of the climate system? That’s where our part of the CAICE project is going, and that is what we’ll be looking for when the wave tank is filled with critters tomorrow!

Franz Geiger, Irving M. Klotz Professor of Chemistry & Associate Chair, Department of Chemistry, Northwestern University