Geochemical Characterization of Chromate Contamination in the 100 Area Vadose Zone at the Hanford Site - Part 2
At the Hanford Site, chromate was used throughout the 100 Areas (100-B, 100-C, 100-D/DR, 100-F, 100-H, and 100 K) as a corrosion inhibitor in reactor cooling water. Chromate was delivered in rail cars, tanker trucks, barrels, and local pipelines as dichromate granular solid or stock solution. In many occasions, chromate was inevitably discharged to surface or near-surface ground through spills during handling, pipeline leaks, or during disposal to cribs. The composition of the liquids that were discharged is not known and it is quite possible that Cr(VI) fate and transport in the contaminated sediments would be a function of the chemical composition of the waste fluids. The major objectives of this investigation which was limited in scope by the financial resources available, were to 1) determine the leaching characteristics of hexavalent chromium [Cr(VI)] from contaminated sediments collected from 100-D Area spill sites; 2) elucidate possible Cr(VI) mineral and/or chemical associations that may be responsible for Cr(VI) retention in the Hanford Site 100 Areas through the use of macroscopic leaching studies, and microscale characterization of contaminated sediments; and 3) provide information to construct a conceptual model of Cr(VI) geochemistry in the Hanford 100 Area vadose zone that can be used for developing options for environmental remediation. The information gathered from this research effort will help to further improve our understanding of Cr(VI) behavior in the vadose zone and will also help in accelerating the 100 Area Columbia River Corridor cleanup by providing valuable information to develop remedial action based on a fundamental understanding of Cr(VI) vadose zone geochemistry. A series of column experiments were conducted with contaminated sediments to study Cr(VI) desorption patterns. Column experiments used the field size fraction of the sediment samples and a simulated Hanford Site groundwater solution. Periodic stop flow events were applied to evaluate the change in elemental concentration during time periods of no flow and greater fluid residence time. Sediments were characterized for the spatial and mineralogical associations of the contamination using some microscale techniques such as X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and Mössbauer spectroscopy.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1004807
- Report Number(s):
- PNNL-17865; 830403000; TRN: US201112%%133
- Country of Publication:
- United States
- Language:
- English
Similar Records
Project Work Plan Chromium Vadose Zone Characterization and Geochemistry
Persistence of Chromate in Vadose Zone and Aquifer Sediments in Hanford, Washington
Related Subjects
CHEMICAL COMPOSITION
CHROMATES
CHROMIUM
COLUMBIA RIVER
CONTAMINATION
CORROSION INHIBITORS
DESORPTION
DICHROMATES
GEOCHEMISTRY
LEACHING
MOESSBAUER EFFECT
PIPELINES
REMEDIAL ACTION
RETENTION
SCANNING ELECTRON MICROSCOPY
SEDIMENTS
SPECTROSCOPY
WASTES
X-RAY DIFFRACTION
X-RAY PHOTOELECTRON SPECTROSCOPY