Brünjes, Jonas

PhD Project: Degradation of complex petroleum hydrocarbons in the marine environment

I am investigating the degradation of complex organic matter from natural marine petroleum seeps, in particular the transformation from insoluble oil to polar, water-soluble compounds and their environmental significance.

Research Interests

• Water-soluble petroleum compounds at natural marine hydrocarbon seeps
• Characterization of petroleum-derived dissolved organic matter (DOM) and its transformation in the water phase
• Ultra-high resolution mass spectrometry (FT-ICR-MS) and optical spectroscopy with PARAFAC modeling

Project Description

Natural oil seepage is an important contributor to the input of petroleum into the marine environment, which is estimated to be about half of the global annual input. At marine petroleum seepage sites specialized ecosystems readily utilize hydrocarbons as an energy and carbon source. However, radiocarbon dating of dissolved organic carbon (DOC) imply that a fraction of seeped hydrocarbons remain in the marine dissolved organic matter (DOM) pool (Wang et al., 2001, Geophysical Research Letters 28). The molecular composition and bioavailability of this petroleum-derived DOM is poorly understood. Polycondensed aromatic compounds (PCAs), such as dissolved black carbon (DBC) in marine DOM, are thought to be mainly derived from incomplete combustion of terrestrial organic matter on land (Dittmar and Paeng, 2009, Nature Geoscience 2). These thermogenic compounds accumulate in the oceanic carbon reservoir over thousands of years and are thus considered to be recalcitrant. Recent research, however, points to additional sources with a marine isotopic signature, such as petrogenic carbon (Wagner et al., 2019, Nature Communications 10). Investigating the potential long-term fate of petroleum-derived DOM and contribution to deep-sea elemental cycling from natural seepage is the overall aim of this project.

Two contrasting natural oil seepage sites are studied: The Chapopote asphalt volcano, a deep-sea heavy-oil seep site in the southern Gulf of Mexico, and the petroleum-laden sediments of the Guaymas Basin in the Gulf of California. The Guaymas Basin distinguishes itself from typical hydrocarbon seeps in that the sedimentary organic matter is hydrothermally altered to complex petroleum compounds on geologically very short timescales.

Environmental porewater and bottom water samples are compared with laboratory experiments such as incubation studies and simulated hot-water discharge events. DOM is characterized by optical spectroscopy and ultra-high-resolution mass spectrometry (FT-ICR-MS) in collaboration with the marine geochemistry group at ICBM Oldenburg. This qualitative analysis is accompanied by quantitative methods to assess the potential impact of petroleum-derived DOM from natural seepage in the deep sea.

Participation in Research Cruises

Thesis Committee