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SLAC National Accelerator Laboratory

The Chemistry of Bromine in Terrestrial and Marine Environments
SSRL Science Summary - November 2012

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. One study measured absolute organobromine concentrations in sediment samples by combining XAS measurements of bromine speciation with x-ray fluorescence measurements of bromine concentration. The resulting data show that organobromine correlates strongly to total organic carbon, and both parameters decrease with sediment depth in most locations. The second study looked at decaying plant material on the forest floor, and showed that all bromine present in humic substances and soil organic matter is covalently bonded to carbon. Common halogenating enzymes were shown to readily brominate healthy plant material, illuminating an environmentally feasible mechanism of organobromine production. The results suggest that inorganic bromide functions as a limiting reagent in the natural bromination of soil organic matter.

These XAS studies have dramatically changed the view of bromine in the environment. Where this element was once believed to exist as an unreactive inorganic species, it is now clear that it participates in dynamic biogeochemical cycling between inorganic and organic forms. The large-scale bromination of natural organic matter may have far-reaching consequences for the preservation and degradation of organic carbon in soils and sediments. The natural bromine cycling identified in these studies may also have implications for the fate of brominated environmental pollutants, such as polybrominated diphenyl ether (PBDE) flame retardants.

This investigation was funded by the U.S. Department of Energy, Office of Basic Energy Sciences (DOE-BES) Chemical and Geosciences Programs, the National Science Foundation (NSF) Chemical Sciences Program, and an NSF Graduate Research Fellowship (ACL).


Primary Citations

A. Leri, J. Hakala, M. Marcus, A. Lanzirotti, C. Reddy, and S. Myneni (2010), Natural organobromine in marine sediments: New evidence of biogeochemical Br cycling, Global Biogeochemical Cycles, 24, GB4017.
[DOI: 10.1029/2010GB003794]

A. Leri and S. Myneni (2012). Natural organobromine in terrestrial ecosystems, Geochimica et Cosmochimica Acta, 77, 1-10.
[DOI: 10.1016/j.gca.2011.11.012]

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Alessandra C. Leri (Marymount Manhattan College) and Satish C.B. Myneni (Princeton University)

2575 Sand Hill Road, MS: 99, Menlo Park, California, 94025, USA Tel: 650-926-4000 | Fax: 650-926-4100