 |
| Titel |
Trace analysis of short-lived iodine-containing volatiles emitted by different types of algae |
| VerfasserIn |
U. R. Thorenz, M. Kundel, R.-J. Huang, T. Hoffmann |
| Konferenz |
EGU General Assembly 2012
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250066602
|
|
|
|
|
|
| Zusammenfassung |
| Atmospheric iodine chemistry in the lower troposphere gained more attention in the last
decade, because of its role in depleting tropospheric ozone and accelerating the ozone
destroying capacity of other halogen species [1]. The iodine oxides formed during this
reaction may also undergo further oxidation and form polyoxides which then can act as cloud
condensation nuclei [2]. Precursors of both reactions are gaseous molecular iodine (I2) and
volatile iodocarbons. Both I2 and iodocarbons are emitted by different kinds of
macroalgae, whereby the emission of I2 dominates [3]. Iodocarbons are also released
by different kinds of microalgaeand itis assumed that also I2 is released by these
algae.
Here we present the results of the measurement of iodine containing volatiles emitted by
eight different macroalgae found in the intertidal zone and microalgae, two pure cultures and
two net samples. To measure I2 emissionfrom macroalgae an on-line time-of-flight aerosol
mass spectrometric method was used[4] to determine the emission rates and to investigate
temporally resolved emission profiles. The molecular iodine emissions from microalgae were
measured using a recently developed denuder sampling technique and GC-MS method [5].
Iodocarbons were preconcentrated on solid adsorbent tubes and measured using
thermodesorption-GC-MS.
The results of the macroalgae experiments showed that Laminariales were found to be the
strongest I2 emitters. Time series of the iodine release of L. digitata and L. hyperborea
showed a strong I2 emission when first exposed to air followed by an exponential decline of
the release rate. For both species I2 emission bursts were observed. For L. saccharina und F.
serratus a more continuous I2 release profile was detected, however, F. serratus released
much less I2. For A. nodosum and F. vesiculosus the I2 emission rates were slowly increasing
with time (1h-2h) until a more or less stable I2 emission rate was reached. The lowest
I2 emission rates were detected for the red algae C. Crispus and D. sanguienea.
Total iodocarbon emission rates showed almost the same general trend, however,
the total iodocarbon emission rates were about one to two orders of magnitude
lower than those of molecular iodine, demonstrating that I2 is the major iodine
containing volatile released by the investigated seaweed species. The dependency
of I2 and iodocarbon emission on the ozone level was investigated, the interplant
variability in I2 emission was to high to see a trend for this compound, but a clear
dependency of iodocarbon emission from the ozone level (0-150 ppb O3) was found for L.
digitata.
The results of the microalgae experiments showed that the pure cultures of
mediopyxis helysia and coscinodiscus wailesii and the net samples of microalgae
emitted iodocarbons (iodomethane, iodochloromethane, iodobromomethane and
diiodomethane). Although no ozone dependency was found for the halocarbons, the ozone
measurements showed that the depletion of ozone was quite different for the different algae
species.
References
[1] Read et al. (2008) Nature 453, 1232–1235. [2] O’Dowed C. et al. (2002) Nature 417,
632–636. [3] Carpenter L. et al. (2005) Environ. Sci. Technol. 39, 8812–8816. [4] Kundel M.
et al. (2011) Anal. Chem. DOI: 10.1021/ac202527a. [5] Huang R.-J. et al.(2009) Anal. Chem.
81, 1777–1783 |
|
|
|
|
|
|