Short-chain alkanes play a substantial role in carbon and sulfur cycling at hydrocarbon-rich environments globally, yet few studies have examined the metabolism of ethane (C2), propane (C3), and butane (C4) in anoxic sediments in contrast to methane (C1). In hydrothermal vent systems, short-chain alkanes are formed over relatively short geological time scales via thermogenic processes and often...

A model for the high-frequency backscatter angular response of gassy sediments is proposed. For the interface backscatter contribution we adopted the model developed by Jackson et al. [J. Acoust. Soc. Am. 79, 1410-1422 (1986)], but added modifications to accommodate gas bubbles. The model parameters that are affected by gas content are the density ratio, the sound speed ratio, and the loss para...

Thick, late Quaternary sediment sections were recovered at several sites on the leeward slope of Great Bahama Bank during Leg 166 of the Ocean Drilling Program. These sections have paleoceanographic records with potentially high temporal resolution. To make an initial assessment of the records corresponding to the Holocene highstand of sea level, we have identified and dated the sediments from ...

Organic-rich subsurface marine sediments were taken by gravity coring up to a depth of 10 m below seafloor at six stations from the anoxic Black Sea and the Benguela upwelling system off Namibia during the research cruises Meteor 72-5 and 76-1, respectively. The quantitative microbial community composition at various sediment depths was analyzed using total cell counting, catalyzed reporter dep...

Molar organic carbon to total nitrogen to organic phosphorus (OC:TN:OP) ratios are used in tandem with carbon isotopic values to constrain sources of organic matter (OM) to marine sediments in a tropical coastal embayment. Analysis of end-members specific to the study site indicates that the bulk OM pool cannot be modeled as a simple mixture of two end-members (terrestrial vs. marine OM), but r...

Much of the row crop production agriculture in the Midwest occurs on soils developed from glacial till, but little research has addressed herbicide biodegradation in subsurface till. This study investigated the ability of indigenous microorganisms to mineralize the herbicide 2,4-D (2,4-dichlorophenoxyacetic acid) at sites in Iowa and Indiana. Microorganisms were able to mineralize 2,4-D, with r...

Pockmarks are geological features that are found on the bottom of lakes and oceans all over the globe. Some are active, seeping oil or methane, while others are inactive. Active pockmarks are well studied since they harbor specialized microbial communities that proliferate on the seeping compounds. Such communities are not found in inactive pockmarks. Interestingly, inactive pockmarks are known...

Soot black carbon (here expressed as GBC) is present in sediments of Central Park and Prospect Park Lakes, New York City (NYC), and peaks in the middle of the 20th Century at the highest values (1-3% dry weight) ever reported in urban lakes. During that period (approximately 1940-1970), the GBC represents up to 28% of the total organic carbon (OC). Radionuclide-normalized whole core inventories...

Arsenic contamination of groundwater is a problem worldwide, and the Terai Basin in the southern plains of Nepal is no exception. The Department of Water Supply and Sanitation of Nepal, with assistance from the World Health Organization (WHO), surveyed three districts of eastern Terai for the first time in 1999, and found that arsenic concentration exceeded the 10 ppb guideline recommended by W...