Stanford Synchrotron Radiation Lightsource

As part of a larger, DOE-funded investigation into bioremediation of uranium in contaminated aquifers, a group of SSRL scientists made a surprising discovery about how uranium ions behave in the environment. In addition to overturning current scientific models, this research will lead to more efficient, less costly methods for uranium cleanup and mining.

Recent work at SSRL has helped reveal a previously unrecognized wealth of bromine chemistry in the environment, where bromine in seawater has long been thought to exist as inorganic bromide, while bromides in soil were considered so unreactive that they've routinely been used as a hydrological tracer.

The reality bromine chemistry in the environment is much more complex. X-ray absorption spectroscopic (XAS) studies conducted by Leri, et al. at SSRL Beam Lines 2-3 and 4-3, as well as at the ALS and NSLS, reveal a complicated association between bromine and organic carbon in both sea water and soil.

Manganese oxides form in the oceanic water column as a result of the bacterially catalyzed oxidation of a relatively abundant form of dissolved manganese. As they settle through the water column, manganese oxides participate in myriad chemical reactions important to sea life and to maintaining the trace-metal composition of sea water. These reactions profoundly impact the geochemical cycling of carbon, nitrogen, sulfur, nutrients and containments.

Mercury (Hg) is a naturally occurring element that poses considerable health risks to humans, with high exposure levels resulting in damage to the brain, heart, kidneys, lungs, and immune system. Young children and unborn babies are particularly vulnerable to mercury, which can affect their nervous systems and impair their neurological development. As a result, mercury is one of the most strictly regulated pollutants by the Environmental Protection Agency (EPA), which controls mercury emissions from coal-fired power plants and issues consumption advisory warnings for various types of fish, the primary route of mercury exposure to humans

A new technology that acts like a giant underground filter is successfully beginning to clean up the uranium contaminating an aquifer in a remote Utah canyon. Uranium contamination in groundwater is a serious problem because the toxic metal can travel long distances in underground aquifers, which are vital sources of fresh water for people, animals and agriculture. Recent research at SSRL showed that the filters-called PRBs (permeable reactive barrier) do intercept uranium, but in an unexpected way that has important implications for monitoring, costs, and future technology selection.

Rice, the grain that provides more than one-fifth of the world population's calories, can become a health hazard if contaminated with arsenic. Such contamination, a surprisingly widespread occurrence, takes place in areas where soil or irrigation water is tainted by naturally occurring arsenic--including broad swaths of south and southeastern Asia. Studies have suggested that the natural iron coating around the roots of rice plants may serve as an important barrier to arsenic uptake because arsenic in its oxidized form has an affinity for iron. A team of Stanford and SSRL researchers recently sought to learn just how significant a barrier iron provides.

The element chromium is found in the environment in two common forms: Cr(VI), which is easily absorbed by the human body, and Cr(III), which is not. The first of these in the form of chromates can have severe adverse effects on the human body, including cancerous tumor formation and gene damage.  Normally Cr(VI) forms are not present in the approximately one billion tons of coal used annually for electricity generation in the U.S., however, a fraction of the Cr(III) in coal can become oxidized during coal combustion ending up as a Cr(VI) component in fly-ash, the major waste product from coal combustion. 

Iron, one of the most abundant metals on Earth’s surface, often dominates the reactivity of rocks, soils and sediments, and is important in many biogeochemical processes.  A great challenge for biogeochemists is to identify the iron species in these natural materials at very small scales and to track changes in the iron species as these materials react with water.

The Rocky Flats Environmental Technology Site (RFETS) is an environmental cleanup site located about 16 miles northwest of downtown Denver (Fig 1).  Two decades of routine monitoring have shown that the environment around RFETS is contaminated with actinide elements (U, Pu, Am) from site operations, [1] and RFETS has been designated by the U.S. Environmental Protection Agency (EPA) as a Superfund cleanup site.  Until December 1989, the Rocky Flats Plant made components for nuclear weapons using various radioactive and hazardous materials, including plutonium, uranium and beryllium. Nearly 40 years of nuclear weapons production left behind a legacy of contaminated facilities, soils, and ground water.  More than 2.5 million people live within a 50 mile radius of the site; 300,000 of those live in the Rocky Flats watershed.

When we think of chlorine, we often relate it to the salt used in food preparation, chloride in the oceans, chlorine gas from swimming pools, and gaseous chlorofluorocarbons that have close links to the depletion of stratospheric ozone. We rarely think of thousands of chlorinated hydrocarbons that exist in the natural systems, several of which are highly toxic to humans (1). The C-Cl bond, common to all organo-Cl compounds, is strong and gives high stability to organo-Cl compounds. For this reason, several organo-Cl compounds have been synthesized and used extensively for years in agricultural and industrial applications.