Featured Research

from universities, journals, and other organizations

New Technique Monitors Chromium Contamination In Groundwater

Date:
March 18, 2002
Source:
University Of Illinois At Urbana-Champaign
Summary:
Widely used in electroplating, hexavalent chromium is a suspected carcinogen and a common contaminant in groundwater. Now, scientists have discovered a simple, but effective, method for monitoring this pollutant.

CHAMPAIGN, Ill. — Widely used in electroplating, hexavalent chromium is a suspected carcinogen and a common contaminant in groundwater. Now, scientists have discovered a simple, but effective, method for monitoring this pollutant.

“Under certain chemical conditions, hexavalent chromium will convert to trivalent chromium – a less toxic form which tends to precipitate out of the groundwater,” said Thomas Johnson, a geologist at the University of Illinois. “Knowing how fast the reaction is occurring within a contaminant plume would help investigators decide whether ‘natural attenuation’ is a viable approach at a site, or if active remediation is required.”

As reported in the March 15 issue of the journal Science, Johnson and his colleagues – graduate student Andre Ellis at the UI and hydrologist Thomas Bullen at the U.S. Geological Survey in Menlo Park, Calif. – have developed a means for measuring how fast, and to what extent, hexavalent chromium is changing to trivalent chromium at a given site. Chromium has four stable (non-radioactive) isotopes. By measuring the isotope fractionation in laboratory experiments and in natural waters, the researchers found that lighter isotopes reacted preferentially during the reduction reaction.

“This means that the trivalent chromium becomes enriched in lighter isotopes as the reduction proceeds, while the remaining hexavalent chromium becomes enriched in heavier isotopes,” Johnson said. “By measuring the relative abundances with an isotope-ratio mass spectrometer, we can determine how much reduction has taken place, and then estimate the long-term reduction rate.”

The partitioning of the lighter isotopes into the reduction product, trivalent chromium, provides a convenient and effective monitoring technique. As the reduction reaction proceeds, the ratio of heavier to lighter isotopes will change.

“A scientist or consultant working on a chromium contamination site can collect a few water samples, analyze them using our technique, and then determine rather directly how much hexavalent chromium reduction has occurred,” Johnson said. “That information can then be used to decide the best course of action – whether aggressively cleaning up the site or leaving it for nature to run its course.”

At some sites, there are naturally occurring reducing agents in the subsurface – such as iron-bearing minerals like magnetite – that will convert hexavalent chromium to trivalent chromium. If the reaction rate is fast enough, the contaminant can be naturally attenuated. Such an approach is much less expensive and disruptive than active remediation. At other sites, chemical reducing agents must be injected in the ground to mitigate the pollution, Johnson said. “In either case, we want to provide a technology to monitor whether the reduction is occurring, and if so, to what extent.”

Based on their measurements, the researchers suggest that all chromium plating waste, regardless of source or different industrial procedures, has nearly the same initial ratio of heavy to light isotopes as that found in naturally occurring igneous rocks and chromium ores. These findings could simplify the monitoring procedure.

“If all contaminant sources are nearly the same, then detection of hexavalent chromium reduction in groundwater systems would be relatively simple, as the initial ratio would be known and any shift would directly indicate the extent of reduction,” Johnson said. “But, if we find that various sources are indeed different, then we can use the unique isotopic ratios as chemical fingerprints to identify specific contaminant plumes.”

The National Science Foundation funded the research.


Story Source:

The above story is based on materials provided by University Of Illinois At Urbana-Champaign. Note: Materials may be edited for content and length.


Cite This Page:

University Of Illinois At Urbana-Champaign. "New Technique Monitors Chromium Contamination In Groundwater." ScienceDaily. ScienceDaily, 18 March 2002. <www.sciencedaily.com/releases/2002/03/020315072021.htm>.
University Of Illinois At Urbana-Champaign. (2002, March 18). New Technique Monitors Chromium Contamination In Groundwater. ScienceDaily. Retrieved October 20, 2014 from www.sciencedaily.com/releases/2002/03/020315072021.htm
University Of Illinois At Urbana-Champaign. "New Technique Monitors Chromium Contamination In Groundwater." ScienceDaily. www.sciencedaily.com/releases/2002/03/020315072021.htm (accessed October 20, 2014).

Share This



More Earth & Climate News

Monday, October 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Traditional Farming Methods Gaining Ground in Mali

Traditional Farming Methods Gaining Ground in Mali

AFP (Oct. 20, 2014) He is leading a one man agricultural revolution in Mali - Oumar Diatabe uses traditional farming methods to get the most out of his land and is teaching others across the country how to do the same. Duration: 01:44 Video provided by AFP
Powered by NewsLook.com
Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-Fuel Impala

Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-Fuel Impala

3BL Media (Oct. 20, 2014) Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-fuel Impala Video provided by 3BL
Powered by NewsLook.com
White Rhino's Death In Kenya Means Just 6 Are Left

White Rhino's Death In Kenya Means Just 6 Are Left

Newsy (Oct. 20, 2014) Suni, a rare northern white rhino at Ol Pejeta Conservancy, died Friday. This, as many media have pointed out, leaves people fearing extinction. Video provided by Newsy
Powered by NewsLook.com
Beijing Marathon Runners Brave Hazardous Air Pollution

Beijing Marathon Runners Brave Hazardous Air Pollution

AFP (Oct. 19, 2014) Tens of thousands of runners battled thick smog at the Beijing Marathon on Sunday, with some donning masks as the levels of PM2.5 small pollutant particles soared to 16 times the maximum recommended level. Duration: 00:54 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins