 |
| Titel |
Hydrologic controls on DOC, As and Pb export from a polluted peatland – the importance of heavy rain events, antecedent moisture conditions and hydrological connectivity |
| VerfasserIn |
T. Broder, H. Biester |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 15 ; Nr. 12, no. 15 (2015-08-06), S.4651-4664 |
| Datensatznummer |
250118051
|
| Publikation (Nr.) |
 copernicus.org/bg-12-4651-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
| Bogs can store large amounts of lead (Pb) and arsenic (As) from
atmospheric deposition of anthropogenic emissions. Pb and As are exported
along with dissolved organic carbon (DOC) from these organic-rich systems,
but it is not yet clear which hydrological (pre)conditions favor their
export. This study combines a 1-year monitoring of precipitation, bog
water level and pore water concentration changes with bog discharge and DOC,
iron, As and Pb stream concentrations. From these data, annual DOC, As, and Pb
exports were calculated. Concentrations ranged from 5 to 30 mg L−1 for DOC, 0.2 to 1.9 μg L−1 for As,
and 1.3 to 12 μg L−1 for Pb, with highest
concentrations in late summer. As and Pb concentrations significantly
correlated with DOC concentrations. Fluxes depended strongly on discharge,
as 40 % of As and 43 % of Pb were exported during 10 % of the time with
the highest discharge, pointing out the over-proportional contribution of
short-time, high-discharge events to annual As, Pb and DOC export.
Exponential increase in element export from the bog is explained by
connection of additional DOC, As and Pb pools in the acrotelm during water
table rise, which is most pronounced after drought. Pb, As and DOC
concentrations in pore water provide evidence of an increase in the soluble
Pb pool as soon as the peat layer becomes hydrologically connected, while DOC
and As peak concentrations in runoff lag behind in comparison to Pb. Our
data indicate a distinct bog-specific discharge threshold of 8 L s−1,
which is thought to depend mainly on the bogs size and drainage conditions.
Above this threshold, element concentrations do not further increase and
discharge becomes diluted. Combining pore water and discharge data shows that
As and Pb exports are dependent on not only the amount of precipitation and
discharge but also on the frequency and depth of water table fluctuations.
Comparing the annual bog As and Pb export with element inventories indicates
that As is much more mobilized than Pb, with annual fluxes accounting for
0.85 and 0.27 ‰ of total As and Pb
inventory, respectively. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|