 |
| Titel |
Photo-lability of deep ocean dissolved black carbon |
| VerfasserIn |
A. Stubbins, J. Niggemann, T. Dittmar |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 5 ; Nr. 9, no. 5 (2012-05-09), S.1661-1670 |
| Datensatznummer |
250007022
|
| Publikation (Nr.) |
 copernicus.org/bg-9-1661-2012.pdf |
|
|
|
|
|
| Zusammenfassung |
| Dissolved black carbon (DBC), defined here as condensed aromatics isolated
from seawater via PPL solid phase extraction and quantified as
benzenepolycarboxylic acid (BPCA) oxidation products, is a significant
component of the oceanic dissolved organic carbon (DOC) pool. These
condensed aromatics are widely distributed in the open ocean and appear to
be tens of thousands of years old. As such DBC is regarded as highly
refractory. In the current study, the photo-lability of DBC, DOC and
coloured dissolved organic matter (CDOM; ultraviolet-visible absorbance)
were determined over the course of a 28 day irradiation of North Atlantic
Deep Water under a solar simulator. During the irradiation DBC fell from
1044 ± 164 nM-C to 55 ± 15 nM-C, a 20-fold decrease in concentration.
Dissolved black carbon photo-degradation was more rapid and more extensive
than for bulk CDOM and DOC. The concentration of DBC correlated with CDOM
absorbance and the quality of DBC indicated by the ratios of different BPCAs
correlated with CDOM absorbance spectral slope, suggesting the optical
properties of CDOM may provide a proxy for both DBC concentrations and
quality in natural waters. Further, the photo-lability of components of the
DBC pool increased with their degree of aromatic condensation. These trends
indicate that a continuum of compounds of varying photo-lability exists
within the marine DOC pool. In this continuum, photo-lability scales with
aromatic character, specifically the degree of condensation. Scaling the
rapid photo-degradation of DBC to rates of DOC photo-mineralisation for the
global ocean leads to an estimated photo-chemical half-life for oceanic DBC
of less than 800 years. This is more than an order of magnitude shorter than
the apparent age of DBC in the ocean. Consequently, photo-degradation is posited as the
primary sink for oceanic DBC and the apparent survival of DBC molecules in
the oceans for millennia appears to be facilitated not by their inherent
inertness but by the rate at which they are cycled through the surface
ocean's photic zone. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|