Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

River delta areas can provide clue to environmental changes

13.05.2009
Sediments released by many of the world's largest river deltas to the global oceans have been changed drastically in the last 50 years, largely as a result of human activity, says a Texas A&M University researcher who emphasizes that the historical information that can be gathered from sediment cores collected in and around these large deltaic regions is critical for a better understanding of environmental changes in the 21st century.

Thomas Bianchi, a professor in the Department of Oceanography who specializes in estuarine and marine systems, and colleague Mead Allison of the University of Texas have examined sediments from delta areas around the world, most notably the Mississippi in the United States and the (Huanghe) Yellow and Yangtze in China.

These sediments contain information that can provide data on past changes in nitrogen application in the drainage basin from agricultural fertilizers, records of past flooding and hurricane events, to name a few, Bianchi says.

Their work is published in the current issue of the "Proceedings of the National Academy of Sciences."

"These deltaic sediments can serve as a history book of sorts on land-use change in these large drainage basins which is useful for upland and coastal management decisions as related to climate change issues," Bianchi explains.

"Although the information stored in these sediments can be altered during its transport from the upper drainage basin to the coast, we still find very stable tracers, both organic and inorganic, that can be used to document changes induced by natural and human forces."

Such sediments are ever-present, the authors say, noting that 87 percent of the Earth's land surface is connected to the ocean by river systems. They also explain that 61 percent of the world's population lives along a coastal boundary, and that number is expected to climb to 75 percent by 2025.

Much of the sediment from rivers forms into what are called large river delta-front estuaries, or LDEs, and human activity in some of these can be traced back more than 5,000 years ago to some of the first cities in Mesopotamia, along the Nile and in regions of China.

The knowledge learned from these delta areas tell about the history of the region from how the land was used – or not used – through time, the authors say. The world's largest 25 rivers drain about one-half of the Earth's surface and transport 50 percent of the fresh water and 40 percent of particulate materials into the ocean, they confirm.

The Mississippi River, the largest in the U.S., drains about 40 percent of the country's total land mass, plus parts of two Canadian provinces, the authors say, and we can learn critical information from its delta regions.

In the U.S., hypoxic areas – where there is little or no oxygen – can in some cases be linked with deltaic regions that are releasing large amounts of water and nutrients, Bianchi explains. "Low oxygen in aquatic systems is clearly not good for the organisms in those systems, but not all aquatic systems respond in the same way," he notes. "It affects marine life in some areas severely, while other areas seem unchanged. We need to find out why.

"Some LDE areas such as the Mississippi/Atchafalaya River system have had significant increases in the nutrient loading from fertilizers" Bianchi adds. "We know we need to reduce the amount of these nutrients from draining into our rivers, but by how much? In this particular case, the linkages between excessive nutrients, hypoxia and their affects on aquatic life are not well understood.

"It's a big problem that China is facing right now as it attempts to manage severe water shortages, over-grazing and desertification issues for a growing population by manipulating natural water sources from their major rivers through damming and diversions. Over the last 20 years, China has become the world's largest consumer of fertilizers and two of its rivers, the Yellow and the Yangtze, are among the top five in the world in terms of sediment discharge.

"Also, many scientists are expecting global temperatures to rise over the next 50 years due to climate changes, and how will these changes affect precipitation and soil erosion issues? We really don't know now because in many cases, land-use change by growing populations can be very short-term and unpredictable, making modeling very difficult. These deltaic sediments might be able to give us some clues about what is ahead for us."

Their work was funded by NASA, the Department of Energy, the Office of Naval Research and the National Science Foundation.

Contact: Thomas Bianchi at (979) 845-5137 or email at tbianchi@tamu.edu or Keith Randall at (979) 845-4644 or email at keith-randall@tamu.edu.

About research at Texas A&M University: As one of the world's leading research institutions, Texas A&M is in the vanguard in making significant contributions to the storehouse of knowledge, including that of science and technology. Research conducted at Texas A&M represents an annual investment of more than $582 million, which ranks third nationally for universities without a medical school, and underwrites approximately 3,500 sponsored projects. That research creates new knowledge that provides basic, fundamental and applied contributions resulting in many cases in economic benefits to the state, nation and world.

Thomas Bianchi | EurekAlert!
Further information:
http://www.tamu.edu
http://tamunews.tamu.edu

More articles from Earth Sciences:

nachricht Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center

nachricht NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science Foundation

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Future electronic components to be printed like newspapers

A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.

The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes

20.07.2018 | Power and Electrical Engineering

Reversing cause and effect is no trouble for quantum computers

20.07.2018 | Information Technology

Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern

20.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>