Tag Archives: soil

In discussion: paper on ecosystem H2 flux measurement techniques

A manuscript I’ve been working on for a good chunk of time now, entitled “Ecosystem fluxes of hydrogen: a comparison of flux-gradient methods,” was just published to Atmospheric Measurement Techniques Discussions (view paper online). Our goal was to present a detailed experimental approach for measuring ecosystem fluxes of H2 and to test different so-called “flux-gradient methods” for calculating the H2 fluxes. Some common trace gas flux methods, e.g. eddy covariance, are not available for species like H2 that cannot be measured precisely at high frequencies (<1Hz). We hope this paper will help inform the design of future studies for which flux-gradient methods might be the best option for measuring trace gas fluxes.

Here are a couple videos on the instrument deployment(1) and design(2) for more information.

H2 flux measurements at Harvard Forest, MA

H2 fluxes were measured at Harvard Forest, MA

 

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Consumption of atmospheric hydrogen during the life cycle of soil-dwelling actinobacteria

The presence (left) or absence (right) of aerial hyphae in Streptomyces may influence their atmospheric H2 consumption

The presence (left) or absence (right) of aerial hyphae in Streptomyces may be linked to atmospheric H2 consumption

Microbe-mediated soil uptake is the largest and most uncertain variable in the budget of atmospheric hydrogen (H2). In a recent study (early view in Environmental Microbiology Reports), we probed the advantage of atmospheric H2 consumption to microbes and relationship between environmental conditions, physiology of soil microbes, and H2. First, we were interested in whether environmental isolates and culture collection strains with the genetic potential for atmospheric H2 uptake (a specific NiFe-hydrogenase gene) actually exhibit atmospheric H2 uptake. To expand the library of atmospheric H2-oxidizing bacteria, we quantify H2 uptake rates by novel Streptomyces soil isolates that contain the hhyL and by three previously isolated and sequenced strains of actinobacteria whose hhyL sequences span the known hhyL diversity. Second, we investigated how H2 uptake varies over organismal life cycle in one sporulating and one non-sporulating microorganism, Streptomyces sp. HFI8 and Rhodococcus equi, respectively. Our observations suggest that conditions favoring H2 uptake by actinobacteria are associated with energy and nutrient limitation. Thus, H2 may be an important energy source for soil microorganisms inhabiting systems in which nutrients are frequently limited.

Much of this work was done with the help of Deepa Rao, an undergraduate researcher at MIT at the time who wrote an award-winning senior thesis on the topic and presented results in a number of venues, including at AGU 2012.

 

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I survived the AGU 2011 Fall meeting

I just returned to Boston after the six weeks of travelling. My two weeks in California, filled with conferences and colleagues, was quite different from the intensive and somewhat isolated period spent in India.

Presenting my poster at AGU - one of 12,000+ posters

First stop was San Diego, where I attended the 44th Meeting of Advanced Global  Atmospheric Gases Experiment (AGAGE) Scientists and Cooperating Networks at the Scripps Institute of Oceanography in La Jolla. Anita Ganesan’s instrument in Darjeeling may pave the way for the first AGAGE site in India, so the crowd was eager to hear her describe our success in deploying her instrument. Her dedicated and diligent work is paying off as she is collecting some of the first high precision direct greenhouse gas measurements in India.

I gave a talk at the AGAGE meeting on my recent work on the flux of H2, CO2 and COS between the soil and atmosphere at Harvard Forest. I focus on the persistence of soil-atmosphere exchange of trace gases across snowpack, which insulates the soil microbial community from freezing air temperatures while allowing trace gases  to diffuse through the porous snow matrix. I’m interested in how strongly the biogeochemical cycling continues throughout the winter and in comparing the behavior of the different cycles in the low temperature ‘incubator’ beneath the snow. Continue reading

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