Hexavalent chromium sensor for real-time In situ measurement of ground water contamination - 15433

Conference · Wed Jul 01 00:00:00 EDT 2015

OSTI ID:22824337

Rod, Kenton; Schuyler, Kimberly A.; Hall, Stephen H. ^[1]

---

1. Freestone Environmental Services, Inc (United States)

Hexavalent chromium (Cr{sup 6+}) is a contaminant of concern at multiple Department of Energy (DOE) and industrial sites across the United States. It is used in stainless steel production, textile dyes, tanning, wood preservation, and in conversion coatings. It was used at DOE sites, such as the Hanford Nuclear Reservation in Washington state, in the form sodium dichromate (Na{sub 2}Cr{sub 2}O{sub 7}) to inhibit corrosion. This has resulted in the release of chromate (CrO{sub 4}{sup 2-}) to groundwater. Chromate is anionic and is readily transported with ground water through the subsurface to receptors such as river biota at Hanford, and in some regions to potable water wells. To improve Cr{sup 6+} groundwater plume monitoring while reducing monitoring cost, a cable-deployed, submersible sensor was developed for direct measurements of Cr{sup 6+} in natural groundwater. With a diameter of 3.8 cm (1.5 inch) the sensor could be deployed in 5 cm (2 inch) diameter screened wells. The sensor uses ultra violet (UV) photo-spectroscopy to measure Cr{sup 6+} at concentrations as low as 5 to 10 μg L{sup -1} (as hexavalent chromium, Cr{sup +6}) in natural water. Turbidity, caused by colloidal material suspended in natural water, can interfere with the chromate measurement but was automatically compensated within the instrument. Because the instrument had some temperature sensitivity, a correction was also applied based on in situ temperature measurements in the sensor. The sensor has been tested in the laboratory and was deployed to the field with encouraging results. Laboratory calibrations consistently yielded concentration measurements that correlate well with standard analytical methods (r{sup 2} = 0.99). (authors)

• Research Organization: WM Symposia, Inc., PO Box 27646, 85285-7646 Tempe, AZ (United States)
• OSTI ID: 22824337
• Report Number(s): INIS-US--19-WM-15433
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
54 ENVIRONMENTAL SCIENCES
ANALYTICAL SOLUTION
CHROMATES
CHROMIUM IONS
COATINGS
CONCENTRATION RATIO
CONTAMINATION
CORROSION
DICHROMATES
DRINKING WATER
DYES
EXPERIMENT RESULTS
GROUND WATER
MONITORING
RECEPTORS
RIVERS
SENSORS
SODIUM
SPECTROSCOPY
STAINLESS STEELS
TEMPERATURE MEASUREMENT
WATER WELLS