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Environmental Geosciences Article

5780
 
We use sediment ages and mercury (Hg) concentrations to estimate past and future concentrations in the South River, Virginia, where Hg was released between 1930 and 1950 from a manufacturing process related to nylon production. In a previous study, along a 40 km (25 mi) reach, samples were collected from 26 of 54 fine-grained deposits that formed in the lee of large wood obstructions in the channel and analyzed for grain size, Hg concentration, and organic content. We also obtained radiometric dates from six deposits. To create a history that reflects the full concentration distribution (which contains concentrations as high as 900 mg/kg [900 ppm]), here, we treat the deposits as a single reservoir exchanging contaminated sediments with the overlying water column, and assume that the total sediment mass in storage and the distribution of sediment ages are time invariant. We use reservoir theory to reconstruct the annual history of Hg concentration on suspended sediment using data from our previous study and new results presented here. Many different reconstructed histories fit our data. To constrain results, we use information from a well-preserved core (and our estimate of the total mass of Hg stored in 2007) to specify the years associated with the peak concentration of 900 mg/kg. Our results indicate that around 850 kg (1874 lb) of Hg was stored in the deposits between 1955 and 1961, compared to only 80 kg (176 lb) today. Simulations of future Hg remediation suggest that 100-yr timescales will be needed for the South River to remove Hg-contaminated sediments from the channel perimeter through natural processes.
5779
 

 SONAR, historical and aerial photographs, and vibracoring were used to assess the type and thickness distribution of sediments impounded by Gold Ray Dam on the Rogue River in southern Oregon. From these data, a volume of about 400,000 cubic yards (

Equation EG13006eq1

) of sediment was determined for the inundated area of the reservoir.

Overall, sediment volumes in the impounded part of the reservoir were less than expected. There are three possibilities that may explain the perceived absence of sediment: (1) the gradient of the Rogue River in this stretch is less, and therefore sediment yields are less; (2) the extraction of gravels and/or other impediments upstream decreased the availability of sediments delivered into the reservoir; and/or (3) sediment was deposited by a prograding delta that filled in the inundated area of the floodplain upstream from Gold Ray Dam. The amount of sediment deposited on this inundated floodplain may have been as much as 1,800,000 cubic yards (Equation EG13006eq2), bringing the total amount of sediment impounded by Gold Ray Dam to Equation EG13006eq3 yards (Equation EG13006eq4).

Applied sedimentology is not only vital to developing a depositional model for the filling of a reservoir, but also providing insights into depositional and erosional changes that will occur upon the removal of a dam. In particular, the processes of delta formation, reoccupation of abandoned channels, and avulsion are paramount in determining sediment accumulation and distribution in reservoirs.

Explorer Article

3786
 

The Indian state of West Bengal, located in eastern India and stretching from the Himalayas to the Bay of Bengal, is a cultural hub where art and literacy flourished. This landscape is dominated by winding rivers and luscious fields of spices, rice and other crops. The Bengal Basin region, however, is confronted with some of the highest levels of naturally occurring arsenic (As) in drinking water, which poses a major health-related environmental threat to the 70-100 million people living in the area.

3785
 

Energy is required to secure, treat and distribute water; conversely, energy production depends on an abundant and reliable source of water.

Explorer Division Column DEG

8079
 

A look at three main environmental issues that must be considered in the utilization of natural gas as a primary fuel source for the next several decades.

Explorer Emphasis

8052
 

Winning Hearts and Minds: Colombia and Latin American prospects offer high promise and difficult hurdles in the form of local political and public resistance.

3792
 

Oil spills are a potential challenge in any corner of the world, but the Arctic brings its own set of challenges to oil production and transportation, and so it needs its own dedicated technologies for meeting them.

Explorer Policy Watch

8589
 

Congressional Republicans want greater public access to scientific data used as a basis for determining the need for air pollution regulations.

8066
 

The first seismic surveys of the Atlantic Outer Continental Shelf (OCS) since 1988 could happen in the next two years – if the Bureau of Ocean Energy Management (BOEM) finalizes the required environmental impact statement (EIS) in the next few months.

3803
 

Oil and natural gas production continued to grow in the United States in 2013 even as progress on new federal laws and regulations stalled – but local opposition to shale gas and oil development increased.

Field Seminar

Las Vegas Nevada United States 31 May, 2014 06 June, 2014 101
 
Las Vegas, Nevada, United States
31 May - 6 June 2014

For those who have not visited the region previously (or have not had the chance to tour it in depth), this field seminar will provide a comprehensive journey into the geological story of this fascinating landscape.

Short Course

Austin Texas United States 29 April, 2014 01 May, 2014 1518
 
Austin, Texas, United States
29 April - 1 May 2014

The overall goal of this course is to provide tools for efficient and effective re-exploration and development. It uses a two-part approach. First it uses petrophysical analysis to understand all that can be derived from examination of standard open-hole logs. This is followed by integrated approaches to discover key factors controlling oil and gas distribution in carbonate reservoirs in the greater Midcontinent USA. Methodologies and workflows reviewed include geosteering and evaluation of horizontal wells and optimizing carbon storage utilization and management.

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