Project Alma Mater

Absorption of Light, Macro algae and Atmosphere

 

Marie Curie Intra European Fellowship (IEF)

 

Project No: 3012109

 

Persons in Charge: Dr. Ranjini Raghunandan, Dr. Andy Ruth

 

 

 

Background Methodology Outreach Project Output

 

 

 

Project Output

 

  • Conference presentations:

     

    • Climate change workshop, UCC Ireland (May 29, 2013) Talk
    • International Meeting and Summer School on Cavity Enhanced Spectroscopy, Naples, Italy (June 10-13, 2013) Poster
    • Conference on Analytical Sciences, UCC Ireland (July 1-2 2013) Poster
  • Co-authored book chapter: A. A. Ruth, S. Dixneuf, R. Raghunandan: Broadband cavity-enhanced absorption spectroscopy, chapter 11 of Cavity-enhanced spectroscopy and Sensing. Edited by H.P. Loock and G. Gagliardi for Springer (2013).

 

Experiments conducted

 

Promising brown macroalgae (such as the laminaria species digitata, saccharina or hyperborea) of the genus 'kelp' were harvested from the Irish coast and studied using the highly-sensitive fourier transform incoherent broadband cavity enhanced spectroscopic technique (FTIBBCEAS) in the near IR wavelength region. In this context, a new water cooled chamber was integrated to the existing IBBCEAS setup to introduce the algae efficiently to the cavity. Efforts were also made to introduce various oxidative stress levels to the macro algae, for example, ultraviolet irradiation of the algae for production of ozone. In addition to laminaria digitata, we also conducted experiments on various other algae species like laminaria hyperborea, fucus and ulva. However we failed to detect in situ release of iodocarbons (CH3I, CH2I2, CHBr3..) from the algae in the NIR.

 

 

During the project time period, experiments were carried out simultaneously on other molecules which have direct impact on ozone depletion and are spectroscopically relevant. These included the NIR spectroscopy of DONO and simultaneous detection of HONO, HNO3 and NO2 by FTIBBCEAS. Nitrous acid, HONO, has been a subject of numerous spectroscopic studies. One of the main reasons for interest in this species, and its deuterated counterpart DONO, is its role in atmospheric chemistry. It has been established by now that HONO is a precursor of the hydroxyl (OH) radical in polluted urban areas, which in turn leads to the formation of ozone. The hydrolysis of NO2 on heterogeneous surfaces is a well-known mechanism for formation of nitrous acid, resulting in HNO3 as a by-product. Simultaneous measurement of these species can thus help understand the production of the molecule and the reaction chemistry better.

 

 

 

We measured for the first time the 2ν1+ν3 and the 3ν1 bands of the cis and trans isomers of DONO in the near infrared region between 5500 and 8000 cm-1 using Fourier Transform Incoherent broadband cavity enhanced absorption spectroscopy (FT-IBBCEAS). All bands were rotationally resolved, yielding spectroscopic constants with good accuracy. Additionally, several bands of HONO, HNO3 and NO2 have been detected simultaneously across the NIR spectral range, demonstrating the potential of the method to detect multiple trace gases simultaneously through their known line positions.