Communication Dans Un Congrès Année : 2023

Quantification and Compound Specific Stable Carbon Isotope Analysis of Dissolved Black Carbon in the Atlantic Ocean

Résumé

Black carbon is a by-product of biomass burning and a major component of the global carbon cycle. A portion of the produced black carbon subsequently enters aquatic systems as dissolved black carbon (DBC) and thus becomes part of the dissolved organic carbon (DOC). Radiocarbon measurements of oceanic DBC revealed ages inconsistent with the estimated oceanic DBC turnover rate assuming a riverine source (from 4800 to 23,000 14C years versus roughly 500 years). Compound specific stable carbon isotope measurements of oceanic DBC confirmed its non-riverine source (δ13C of roughly −29‰ in rivers versus roughly −23‰ in oceans). However, only a few oceanic water column profiles were sampled for DBC measurements, so the main source of oceanic DBC remains poorly constrained. Indeed, benzene polycarboxylic acids (BPCAs), which are obtained by oxidizing the polycondensed aromatic fraction of DBC, may have other sources than pyrogenic DBC, such as humic acids. Here we measured for the first time DBC in the water column along several transects within the Atlantic Ocean (Figure 1). We sampled DBC along both longitudinal and latitudinal transects, which cover several Atlantic Ocean regions with contrasting environmental contexts, notably the trophic regime and biomass burning aerosol inputs related to atmospheric circulation within the tropics. We also sampled DBC within several specific water masses along all transects. We then processed DBC for quantification using an in-house BPCA method and high-performance liquid chromatography coupled to diode-array detection, followed by compound specific stable carbon isotope analysis. We also did complementary bulk measurements for DOC quantification and stable carbon isotope analysis. All samples yielded measurable amounts of BPCAs, which are mostly B6CA and B5CA, the BPCA molecular markers presumed to have an exclusive pyrogenic origin. The different water masses had similar DBC abundances within analytical uncertainties, which suggests homogenous oceanic DBC profiles. Similarly, DBC abundances showed little spatial variability despite the contrasts in biomass burning aerosol inputs. The stable carbon isotope composition of BPCAs suggests a marine source of DBC.

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Dates et versions

hal-04222608 , version 1 (29-09-2023)

Identifiants

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Nina Davtian, Nuria Penalva-Arias, Oriol Teruel-Cabello, Pau Comes-Bordas, Antoni Rosell-Melé, et al.. Quantification and Compound Specific Stable Carbon Isotope Analysis of Dissolved Black Carbon in the Atlantic Ocean. 31st International Meeting on Organic Geochemistry (IMOG 2023), Sep 2023, Montpellier, France. pp.1-2, ⟨10.3997/2214-4609.202333159⟩. ⟨hal-04222608⟩
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