Distribution of polycyclic aromatic hydrocarbons in eolian and eolian-deluvial sediments from the North Iceland

This work considers results of a study of Holocene cover sediments in Iceland. They are largely composed of wind-transported palagonitized hyaloclastite particles and coeval horizons of acid and basic tephras. It is established that polyciclic aromatic hydrocarbons (PAH) are released from basaltic glass in natural environments only in case of intense physicochemical alteration and destruction of its structure. This process does not influence PAH composition and their quantitative proportions. No new PAH formed during several thousands of years in Holocene section. Hydrocarbons are transferred from fixed state in basaltic glass into free state in palagonites practically without any changes. PAH were mainly redeposited by winds, derived together with palagonite from weathered hyaloclastites, and precipitated from atmosphere with tephra during eruptions.

Sources and seasonality of polycyclic aromatic hydrocarbons transported to Alert, Canadian Arctic

A probabilistic function (integrated source contribution function, ISCF) based on backward air mass trajectory calculation was developed to track sources and atmospheric pathways of polycyclic aromatic hydrocarbons (PAHs) to the Canadian High Arctic station of Alert. In addition to the movement of air masses, the emission intensities at the sources and the major processes of partition, indirect photolysis, and deposition occurring on the way to the Arctic were incorporated into the ISCF. The predicted temporal trend of PAHs at Alert was validated by measured PAH concentrations throughout 2004. The PAH levels in the summer are orders of magnitude lower than those in the winter and spring when long-range atmospheric transport events occur more frequently. PAHs observed at Alert are mostly from East Asia (including Russia Far East), North Europe (including European Russia), and North America. These sources account for 25, 45, and 27% of PAHs atmospheric level at Alert, respectively. Source regions and transport pathways contributing to the PAHs contamination in the Canadian High Arctic vary seasonally. In the winter, Russia and Europe are the major sources. PAHs from these sources travel eastward and turn to the north at approximately 120°E before reaching Alert, in conjunction with the well- known Arctic haze events. In the spring, PAHs from Russia and Europe first migrate to the west and then turn to the north at 60°W toward Alert. The majority of PAHs in the summer are from northern Canada where they are carried to Alert via low- level transport pathways. In the fall, 70% of PAHs arriving at Alert are delivered from North American sources.

Low-molecular-weight hydrocarbons in sediments of Broken Ridge and Ninetyeast Ridge

Core samples taken during Leg 121 drilling aboard the JOIDES Resolution in the central Indian Ocean were analyzed for their low-molecular-weight hydrocarbon contents. Forty-three samples from the Broken Ridge and 39 samples from the Ninetyeast Ridge drill sites, deep-frozen on board immediately after recovery, were studied by a dynamic headspace technique (hydrogen-stripping/thermovaporization). Light hydrocarbons (saturated and olefinic) with two to four carbon atoms, and toluene as a selected aromatic compound, were identified. Total C2-C4 saturated hydrocarbon yields vary considerably from virtually zero in a Paleogene calcareous ooze from Hole 757B to nearly 600 nanogram/gram of dry-weight sediment (parts per billion) in a Cretaceous claystone from Hole 758A. An increase of light-hydrocarbon yields with depth, and hence with sediment temperature, was observed from Hole 758A samples down to a depth of about 500 meters below seafloor. Despite extreme data scatter due to lithological changes over this depth interval, this increased yield indicates the onset of temperature-controlled hydrocarbon formation reactions. Toluene contents are also extremely variable (generally between 10 and 100 ppb) and reach more than 300 ppb in two samples of tuffaceous lithology (Sections 121-755A-17R-4 and 121-758A-48R-4). As for the saturated hydrocarbons, there was also an increase of toluene yields with increasing depth in Hole 758A.

Studies of the microbial diversity on analyzed samples from from Peru Margin, Equatorial Pacific, Hydrate Ridge, and Juan de Fuca Ridge

Marine sediments harbor an enormous quantity of microorganisms, including a multitude of novel species. The habitable zone of the marine sediment column begins at the sediment-water interface and probably extends to depths of several thousands of meters. Studies of the microbial diversity in this ecosystem have mostly relied on molecular biological techniques. We used a complementary method - analysis of intact polar membrane lipids - to characterize the in-situ microbial community in sediments covering a wide range of environmental conditions from Peru Margin, Equatorial Pacific, Hydrate Ridge, and Juan de Fuca Ridge. Bacterial and eukaryotic phospholipids were only detected in surface sediments from the Peru Margin. In contrast, deeply buried sediments, independent of their geographic location, were dominated by archaeal diether and tetraether lipids with various polar head groups and core lipids. We compared ring distributions of archaeal tetraether lipids derived from polar glycosidic precursors with those that are present as core lipids. The distributions of these related compound pools were distinct, suggestive of different archaeal sources, i.e., the polar compounds derive from sedimentary communities and the core lipids are fossil remnants from planktonic communities with possible admixtures of decayed sedimentary archaea. This in-situ production of distinct archaeal lipid populations potentially affects applications of the TEX86 paleotemperature proxy as demonstrated by offsets in reconstructed temperatures between both pools. We evaluated how varying cell and lipid stabilities will influence the sedimentary pool by using a box-model. The results are consistent with (i) a requirement of continuous inputs of freshly synthesized lipids in subsurface sediments for explaining the observed distribution of intact polar lipids, and (ii) decreasing lipid inputs with increasing burial depth.