Natural Breakdown of Petroleum Underground Can Lace Arsenic into Groundwater plus 1 more |
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Natural Breakdown of Petroleum Underground Can Lace Arsenic into Groundwater Posted: 26 Jan 2015 05:36 AM PST
Summary: In a long-term field study, U.S. Geological Survey (USGS) and Virginia Tech scientists have found that changes in geochemistry from the natural breakdown of petroleum hydrocarbons underground can promote the chemical release (mobilization) of naturally occurring arsenic into groundwater
Contact Information: Jon Campbell ( Phone: 703-648-4180 ); Isabelle Cozzarelli ( Phone: 703-648-5899 ); In a long-term field study, U.S. Geological Survey (USGS) and Virginia Tech scientists have found that changes in geochemistry from the natural breakdown of petroleum hydrocarbons underground can promote the chemical release (mobilization) of naturally occurring arsenic into groundwater. This geochemical change can result in potentially significant arsenic groundwater contamination. While arsenic is naturally present in most soils and sediments at various concentrations, it is not commonly a health concern until it is mobilized by a chemical reaction and dissolves into groundwater. Elevated arsenic levels in groundwater used for drinking water is a significant public health concern since arsenic, a toxin and carcinogen, is linked to numerous forms of skin, bladder, and lung cancer. For the past 32 years, a collaborative group of government, academic, and industry-supported scientists have studied the natural attenuation (biodegradation over time) of a 1979 petroleum spill in the shallow, glacial aquifer at the National Crude Oil Spill Fate and Natural Attenuation Research Site, near Bemidji, Minnesota. Working at this intensively surveyed site, the researchers in this USGS-led investigation focused on a specific question: whether naturally occurring arsenic found in the glacial aquifers in this area might be mobilized in the presence of hydrocarbons because of chemical interactions involving iron hydroxides which also occur naturally. To address this question, arsenic concentrations were measured for several years in groundwater and in sediment up-gradient, within, and down-gradient from the hydrocarbon plume at Bemidji. Carefully measured samples from the field reveal that arsenic concentrations in the hydrocarbon plume can reach 230 micrograms per liter — 23 times the current drinking water standard of 10 micrograms per liter. Arsenic concentrations fall below 10 micrograms per liter both up-gradient and down-gradient from the plume. The scientists attributed the elevated arsenic in the hydrocarbon plume to a series of interrelated geochemical and biochemical processes that involve arsenic and iron oxides (both are commonly found in sediments across the country) and the metabolization of carbon–rich petroleum by microbes in anoxic (low oxygen) conditions. The complex chemical process is explained further at this USGS website and in the published research article. The results from this work also suggest that the arsenic released in the plume may reattach to aquifer sediments down-gradient from the plume. This reattachment could be considered good news for limiting the extent of the arsenic contamination in the groundwater. However, the chemical reattachment process may also be reversible, highlighting the need for long–term monitoring of arsenic and other chemicals that pose a water quality concern in areas associated with petroleum hydrocarbon leaks and spills. The presence and amount of naturally occurring arsenic and iron oxides and the condition of the groundwater in the study area are fairly typical of many geologic settings across the nation, suggesting that the process of arsenic mobilization that was observed in the presence of hydrocarbons is not geographically limited. This research was supported by the USGS Toxic Substances Hydrology Program and Hydrologic Research and Development Program, the Virginia Polytechnic Institute and State University, and the National Crude Oil Spill Fate and Natural Attenuation Research Site, a collaborative venture of the USGS, the Enbridge Energy Limited Partnership, the Minnesota Pollution Control Agency, and Beltrami County, Minnesota. By law, the USGS, a science bureau of the U.S. Department of the Interior, does not have any regulatory authority or responsibility. Learn more USGS Toxic Substances Hydrology Program USGS National Research Program (Water) |
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More Global Topographic Data to Aid Climate Change Research Posted: 26 Jan 2015 05:00 AM PST
Summary: Improved global topographic (elevation) data are now publicly available for most of Asia (India, China, southern Siberia, Japan, Indonesia), Oceania (Australia, New Zealand), and western Pacific Islands
Enhanced elevation data for most of Asia and Oceania; third of four releasesContact Information: Jon Campbell ( Phone: 703-648-4180 ); Improved global topographic (elevation) data are now publicly available for most of Asia (India, China, southern Siberia, Japan, Indonesia), Oceania (Australia, New Zealand), and western Pacific Islands. See diagram below for geographic coverage. Similar data were previously released by USGS for most of Africa (in September 2014) and the Western Hemisphere (December). The data are being released following the President’s commitment at the United Nations to provide assistance for global efforts to combat climate change. The broad availability of more detailed elevation data across the globe through the Shuttle Radar Topography Mission (SRTM) will improve baseline information that is crucial to investigating the impacts of climate change on specific regions and communities. “We are pleased to offer improved elevation data to scientists, educators, and students worldwide. It’s free to whomever can use it,” said Suzette Kimball, acting USGS Director, at the initial release of SRTM30 data for Africa in September. “Elevation, the third dimension of maps, is critical in understanding so many aspects of how nature works. Easy access to reliable data like this advances the mutual understanding of environmental challenges by citizens, researchers, and decision makers around the globe.” The SRTM30 datasets resolve to 30-meters and can be used worldwide to improve environmental monitoring, advance climate change research, and promote local decision support. The previous global resolution for this data was 90-meters. SRTM30 elevation data are increasingly being used to supplement other satellite imagery. In India, for example, SRTM30 elevation data can be used to track changes to the Gangotri Glacier, a major source of water for the Ganges River. Changes to this glacier, which has retreated 345 meters over the past 25 years, directly affect the water resources for hundreds of millions of people on the Indian subcontinent. USGS online poster of the Gangotori Glacier The National Aeronautics and Space Administration (NASA) and the National Geospatial-Intelligence Agency (NGA) worked collaboratively to produce the enhanced SRTM data, which have been extensively reviewed by relevant government agencies and deemed suitable for public release. SRTM flew aboard the Space Shuttle Endeavour in February 2000, mapping Earth's topography between 56 degrees south and 60 degrees north of the equator. During the 11-day mission, SRTM used imaging radar to map the surface of Earth numerous times from different perspectives. The USGS, a bureau of the U.S. Department of the Interior, distributes SRTM30 data free of charge via its user-friendly Earth Explorer website. NASA also distributes SRTM data versions through the Land Processes Distributed Active Archive Center (LPDAAC) operated by USGS along with descriptions of the various versions and processing options. Enhanced 30-meter resolution SRTM data for the remainder of the globe (at less than 60 deg. latitude) are scheduled to be released in the last of four releases in August 2015. NASA press release on SRTM data
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