Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Study finds tungsten in aquifer groundwater controlled by pH, oxygen

01.10.2013
Two Kansas geologists are helping shed new light on how tungsten metal is leached from the sediment surrounding aquifers into the groundwater. The findings may have implications for human health.

Tungsten is a naturally occurring metal that is primarily used for incandescent light bulb filaments, drill bits and an alternative to lead in bullets. Though it is thought to be nonhazardous to the environment and nontoxic to humans, it can be poisonous if ingested in large amounts. In recent years, tungsten has been tentatively linked to cases of childhood leukemia in the Western U.S.


Chad Hobson, master's student in geology, Lavonia, Ga., collects sediment samples from Cheyenne Bottoms in Hoisington, Kan.

"Very little is known about the biogeochemistry of tungsten in the environment," said Saugata Datta, professor of geology at Kansas State University. "We need to understand how this metal is leached from the soils into groundwater because humans can be exposed to tungsten through multiple pathways."

Datta, along with Chad Hobson, master's student in geology, Lavonia, Ga., and colleagues at Tulane University and the University of Texas, Arlington, found that the likelihood that tungsten will seep into an aquifer's groundwater depends on the groundwater's pH level, the amount of oxygen in the aquifer and the number of oxidized particles in the water and sediment. Analysis also showed that tungsten-VI is the most common form of tungsten in natural sediments.

These latest findings appear in the study "Controls on tungsten concentrations in groundwater flow systems: The role of adsorption, aquifer sediment Fe(III) oxide/oxyhydroxide content, and thiotungstate formation," published in the journal Chemical Geology.

In addition to the publication, Datta and Hobson presented the findings at the International Conference on Biogeochemistry of Trace Elements.

For the study, researchers looked at Fallon, Nev.; Sierra Vista, Ariz.; and at the Cheyenne Bottoms Refuge near Hoisington, Kan. The sites were chosen based on previous studies analyzing plants and dust collected on trees in the locations. Additionally, these areas have natural tungsten mineral deposits, nearby military bases, and mining and smelting operations in the area, Datta said.

In 2002, the Centers for Disease Control investigated several clusters of acute lymphatic leukemia in both Nevada and Arizona. The investigation found that residents' urine had tungsten levels above the 95th percentile.

"This was important for us to know because the goal is to clarify valuable information about tungsten's geochemistry," Datta said. "So, we needed sites that had tungsten -- and enough tungsten to measure easily. The benefit of this study is that tungsten's geochemistry has been overlooked and until recently, largely unknown. This work will help fill the gaps in the knowledge of tungsten, which is possibly carcinogenic, and help determine its future use."

Datta and Hobson analyzed sediment samples lining the aquifers while researchers at Tulane University and the University of Texas, Arlington analyzed the groundwater samples. The National Synchrotron Light Source was used for spectroscopic analysis of the individual particles. This helped researchers understand the speciation of tungsten in natural sediments in the environment and helped them detect why tungsten forms organosulphur complexes that can be soluble in groundwater, Datta said. Analysis also showed that tungsten-VI is the most common form of tungsten in natural sediments.

Analysis of the sediment and groundwater showed that iron oxide and oxyhydroxide particles in both substances play a key role in regulating how much tungsten is in the groundwater. The fewer iron oxides or oxyhydroxide particles, the higher the amount of tungsten, Datta said.

Similarly, the team found that the number of tungsten-regulating iron oxide particles is controlled by the pH in the groundwater. A higher pH results in more tungsten entering the water.

"Tungsten is specifically bound to these iron oxides and oxyhydroxides," Datta said. "One of the major factors controlling tungsten's mobility and bioavailability is pH. Ranging values of pH can affect how tungsten behaves or transforms between different tungsten species, which have different properties and factors controlling mobility."

When tungsten is in the water it is surrounded by oxygen atoms and forms an anion, Datta said. When in the presence of phosphates, this anion tends to bind with other transition metals, commonly iron, to form poloyoxometalates. In this form, tungsten can become more soluble in water.

Researchers also found that aquifers with less dissolved oxygen had greater traces of tungsten in the groundwater than aquifers with high dissolved oxygen levels.

The process of tungsten being leached from the surrounding sediment into the groundwater can be reduced if the ironoxides are in the water and the water has a neutral pH level, according to Datta.

The study is part of a three-year, $515,000 National Science Foundation-funded project between Kansas State University and Karen Johannesson at Tulane University that is titled "Collaborative Research: Chemical Hydrogeologic Investigations of Tungsten: Field, Laboratory, and Modeling Studies of an Emerging Environmental Contaminant." It focuses on biogeochemistry of tungsten's reaction to the environment and how it is transported from sediments into groundwaters once it becomes geochemically mobilized.

Saugata Datta | EurekAlert!
Further information:
http://www.k-state.edu

More articles from Earth Sciences:

nachricht New Study Will Help Find the Best Locations for Thermal Power Stations in Iceland
19.01.2017 | University of Gothenburg

nachricht Water - as the underlying driver of the Earth’s carbon cycle
17.01.2017 | Max-Planck-Institut für Biogeochemie

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

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...

Im Focus: Studying fundamental particles in materials

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...

Im Focus: Designing Architecture with Solar Building Envelopes

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...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>