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 firstname.lastname@example.org or Keith Randall at (979) 845-4644 or email at email@example.com.
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.
Further reports about: > Earth's surface > LDE > Mesopotamia > Mississippi > River > River delta areas > Yangtze River > agricultural fertilizers > aquatic systems > drainage basins > environmental changes > global temperature > hurricane events > land-use change > marine systems > nitrogen application > past flooding > sediments > water source
Water - as the underlying driver of the Earth’s carbon cycle
17.01.2017 | Max-Planck-Institut für Biogeochemie
Modeling magma to find copper
13.01.2017 | Université de Genève
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
18.01.2017 | Materials Sciences
18.01.2017 | Information Technology
18.01.2017 | Ecology, The Environment and Conservation