Incubation experiments to examine the production and loss of CH3I in surface seawater


In order to investigate production pathways of methyl iodide and controls on emissions from the surface ocean, a set of repeated in-vitro incubation experiments were performed over an annual cycle in the context of a time-series of in-situ measurements in Kiel Fjord (54.3 N, 10.1E). The incubation experiments revealed a diurnal variation of methyl iodide in samples exposed to natural light, with maxima during day time and losses during night hours. The amplitude of the daily accumulation varied seasonally and was not affected by filtration (0.2µm), consistent with a photochemical pathway for CH3I production. The methyl iodide loss rate during night time correlated with the concentration accumulated during daytime. Daily (24 hour) net production (Pnet) was similar in magnitude between in vitro and in situ mass balances. However, the estimated gross production (Pgross) of methyl iodide ranged from -0.07 to 2.24 pmol/day and were 5 times higher in summer than Pnet calculated from the in-situ study [Shi et al., 2014]. The large excess of Pgross over Pnet revealed by the in-vitro (incubation) experiments in summer is a consequence of large losses of CH3I by as-yet uncharacterized processes (e.g. biological degradation or chemical pathways other than Cl- substitution).

Supplement to: Shi, Qiang; Marandino, Christa A; Petrick, Gert; Quack, Birgit; Wallace, Douglas WR (2014): A time series of incubation experiments to examine the production and loss of CH3I in surface seawater. Journal of Geophysical Research: Oceans, 119(12), 8242-8254

Related Identifier
Metadata Access
Creator Shi, Qiang; Marandino, Christa A ; Petrick, Gert; Quack, Birgit; Wallace, Douglas WR
Publisher PANGAEA
Publication Year 2014
Rights Creative Commons Attribution 3.0 Unported;
OpenAccess true
Language English
Resource Type Supplementary Dataset; Dataset
Format text/tab-separated-values
Size 1584 data points
Discipline Earth System Research
Temporal Coverage Begin 2009-08-13T00:00:00Z
Temporal Coverage End 2010-11-15T00:00:00Z