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| Titel |
Vertical fluxes of organic contaminants in the Ligurian Sea. |
| VerfasserIn |
Remi Deyme, Ioanna Bouloubassi, Marie-Helene Taphanel-Valt, Juan-Carlos Miquel, Anne Lorre, Jean-Claude Marty, Laurence Méjanelle |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250040408
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| Zusammenfassung |
| High resolution temporal series of hydrological and biogeochemical parameters have been
monitored throughout the SO-DYFAMED program, aiming at better understanding the
response of the ocean to anthropic and climatic disturbance.
The present contribution addresses fluxes of organic semi-volatile contaminants and of
biogenic lipids associated with marine sinking particles. Sediment trap samples were
collected at the DYFAMED station (Ligurian Sea, NW Mediterranean Sea) from December
2000 to July 2002, at a depth of 200m and 1000m, and with a time step of 2 to 3 weeks.
Polycyclic Aromatic Hydrocarbons (PAHs) and Non-Aromatic Hydrocarbons (NAHs) were
investigated to characterize the levels of contamination and the fluxes of contaminants
transferred from the upper marine waters to intermediate waters. Specific lipids of
phytoplankton, terrigeneous matter and faecal pellets were also determined, aiming at better
understanding biogeochemical processes that may impact on pollutant transfer toward deeper
marine horizons.
Up to 36 PAHs were identified. The 13 parent compound levels (-
PAH13) varied from
564 to 4156 ng.g-1, with highest concentrations corresponding to winter months. The
molecular profile was dominated by low molecular weight PAHs and higher abundance of
alkylated homologues over parent compounds. This characteristic, together with diagnostic
molecular ratios attribute the main part of PAHs to a petrogenic origin. Aliphatic
hydrocarbons were largely dominated by an UCM (Unresolved Complex Mixture),
accounting for ca. 91 % of NAHs, which further confirms the dominant petrogenic origin of
hydrocarbons.
Fluxes of PAHs13 and NAHs varied from 0.29 to 0.422 and from 0.4 to 19.0 μg.m2.d-1,
respectively. Alike concentrations, PAH fluxes were higher than those reported in other open
Mediterranean locations, revealing that the study site is under a stronger anthropogenic
influence. Various inputs of contaminants at the study site may be pointed out: riverine inputs,
ship traffic and likely ship ballasting.
Temporal variations of PAH and NAH fluxes show highest values in late winter - spring.
Mass fluxes appear to exert the main control on the downward transfer of PAH/NAH
contaminants. High fluxes in late winter-spring months are linked to intense mixing and onset
of primary production. Fluxes and concentrations of long-chain alkenones and unsaturated
alkenes, biomarkers of Haptophyte algae, showed higher values in April-May and
July-October, reflecting the seasonal variation of Haptophyte productivity. Organic carbon
(OC) flux, describing the overall productivity of the ecosystem, also described spring and fall
maxima.
OC and biogenic lipid fluxes decreased between 200m and 1000m deep samples. Surface
spring and fall maxima of OC fluxes were poorly recorded at 1000m, revealing strong
mineralization of the biogenic material during sinking. In contrast, PAHs and NAHs
fluxes recorded at both depths were of the same order, suggesting no significant
degradation and/or desorption of contaminants from sinking particles. Thus, despite
consistent changes in the nature and composition of the particles during sinking, the
pollutant load originating from the surface is efficiently transferred to the deep
marine environment, which may act as a sink of organic semi-volatile pollutants. |
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