No description available.

No description available.

No description available.

No description available.

Graduation date: 1968

Radioactive chromium-51, a waste byproduct from operation of nuclear reactors at Hanford, Washington, has been followed down the Columbia River and into the Pacific Ocean. Chemical factors influencing the partitioning of ⁵¹Cr between solution and sediment have been considered. Chromium-5l, in a hexavalent oxyanion when introduced into the Columbia River, largely remains in solution in a hexavalent anion during its passage through the lower river and after its entrance into the Pacific Ocean. A minor fraction of Hanford-induced ⁵¹Cr becomes attached to suspended particles and bottom sediments. Reduction of Cr(VI) to Cr(III) apparently precedes or accompanies sorption. Iron oxides appear to be the most important sorption substrate. Sediment organic matter acts both as a reducing agent, making ⁵¹Cr less soluble, and as a sorption substrate. Ion exchange on sediment particles is not important in retention of ⁵¹Cr by Columbia River sediment. Chromium-51 is a sensitive and unique tracer for Columbia River water at sea and has been used to trace the Columbia River plume up to 525 km away from the mouth of the river. Dispersion of ⁵¹Cr by the Columbia River system would be adversely affected by: 1) lowered pH; 2) presence of particulate organic wastes; 3) increased temperature; 4) increased biological oxygen demand. These factors would increase the rate of uptake of ⁵¹Cr by sediments and thus increase the steady-state inventory of ⁵¹Cr on the bottom of the river. / Graduation date: 1967

Graduation date: 1970

Graduation date: 1970

Graduation date: 1999

Mass-independent fractionation (MIF) of Hg isotopes has the potential to track the environmental transport and fate of Hg. Herein we demonstrate that reducing both the frequency and intensity of light have a large effect on the expression and magnitude of MIF. This strongly supports the magnetic isotope effect as the mechanism behind MIF observed during aqueous photo-reduction of Hg(II) and MeHg. The ratios of MIF, KapDelta199Hg/KapDelta201Hg, were 1.00 ± 0.04 (2SE) for Hg(II) and 1.35 ± 0.16 (2SE) for MeHg respectively and did not change as incident radiation energy and magnitude of MIF diminished, suggesting the respective MIF pathways remained constant regardless of experimental conditions. Comparable amounts of total photo-reduction were shown to coincide with different magnitudes of MIF depending the wavelength light available for photo-reduction. This confirms there are multiple pathways for photo-reduction in freshwater reservoirs and indicates that quantitatively relating photo-reduction and MIF will be challenging.