LONG-TERM RECONSTRUCTION OF WATER LEVEL CHANGES FOR LAKE ATHABASCA BY ANALYSIS OF TREE RINGS1

ABSTRACT: The fact that dendrochronology can be a useful tool in water resources management is demonstrated by a study of past changes in lake levels. The study was necessitated by the recent (1967) closure of the gates on the W.A.C. Bennett Dam on the Peace River in British Columbia, causing a drop in water levels of Lake Athabasca, the lake levels control water level undulations in a series of smaller lakes which lie in the 1.5 million acre delta area along its western edge in Alberta. The W.A.C. Bennett Dam has by its regulation of the Peace River affected the river's historical role of creating a hydraulic dam during early summer flood stages thereby preventing outflow from Lake Athabasca and inducing annual inundation of the delta area. Because the ecololgy of the lake and adjacent delta region has depended on the now attenuated snow-melt flooding from the Upper Peace River Basin, it became necessary to consider some means of artificially inducing this annual inundation. It was not known, however, what the long-term water level changes were around which the present ecology had developed. Continuous historical lake level records exist only for the period 1935–1967. Was this period one of anomalously high or low water levels? Relatively old white spruce trees growing along natural levees of the channels in the delta region were found to contain tree-ring records that reflected the water stages in the channels. Because the water levels in the channels could be correlated with lake levels, it was possible to use the three-ring series to extend the known 33-year record of lake level changes to 158 years. By using canonical analysis and 10-day mean lake levels for three different subperiods in the 33-year period of calibration, along with tree-ring series from appropriately chosen stands of white spruce, reconstructions were made of the long-term record for late May, early July, and late September. The reconstructed record shows that the May 21–30 lake levels have been three times as variable in the past as in the period of historical record (1935–1967), the July 11–20 levels twice as variable, and the September 21–30 levels 10% less variable. However, the mean water level for each of the three subperiods for the long-term record is very close to the means for the period of historical record. The reconstructed record shows that, before the dam gates were closed, there was only one three-year period (1866–1868) in which the lake levels were as low as they have been since closure of the gates (that is, 1967–1970). (Levels were nearly as low, however, during the period 1942–1945.     

Transport of coliphage PRD1 in a surface flow constructed wetland.

A tracer study was conducted in a 3-ha surface flow constructed wetland to analyze transport performance of PRD1, an enteric virus model. The convection-dispersion equation (CDE), including a first-order reaction model, adequately simulated transport performance of PRD1 in the wetland under an average hydraulic loading rate of 82 mm/d. Convective velocity (v) and longitudinal dispersion coefficient (D) were estimated by modeling a conservative tracer (bromide) pulse through the wetland. Both PRD1 and bromide were simultaneously added to the entering secondary treated wastewater effluent. The mass of bromide and PRD1 recovered was 76 and 16%, respectively. The PRD1 decay rate was calculated to be 0.3/day. The findings of this study suggest that the CDE model and analytical moment equations represent a suitable option to characterize virus transport performance in surface flow constructed wetlands.     

Nuclear waste disposition and site remediation: U.S. department of energy,state governments,and other stakeholders dialogue

Remediation responsibilities of the U.S. Department of Energy (DOE) encompass a vast national complex of highly contaminated former weapons facilities. During the mid‐1990s, DOE announced its intentions to consolidate some waste types at specific sites. At about the same time, organizations and public officials around DOE sites urged a National Dialogue, designed to develop comprehensive solutions to the Department's needs for waste disposition ( transportation, treatment, and storage). Recent opposition from citizens and elected officials in Nevada and Washington State has presented obstacles to DOE's plans. Additionally, chairs of nine site‐specific advisory boards recommended that DOE support a National Stakeholder Forum, similarly designed to develop solutions to disposition needs. This article reviews the chronology of DOE's disposition efforts, along with public and state reactions and recommendations. © 2006 Wiley Periodicals, Inc.     

The DNA damage activity (DDA) assay and its application to river waters and diesel exhausts

An extremely sensitive assay has been developed for DNA-damaging chemicals using a DNA repair-deficient strain of Escherichia coli. Considerable DNA-damaging activity has been demonstrated by this assay in natural surface-water samples and in diesel-exhaust particulate extracts.     

In situ uranium stabilization by microbial metabolites

Microbial melanin production by autochthonous bacteria was explored in this study as a means to increase U immobilization in U contaminated soil. This article demonstrates the application of bacterial physiology and soil ecology for enhanced U immobilization in order to develop an in situ, U bio-immobilization technology. We have demonstrated microbial production of a metal chelating biopolymer, pyomelanin, in U contaminated soil from the Tims Branch area of the Department of Energy (DOE), Savannah River Site (SRS), South Carolina, as a result of tyrosine amendments. Bacterial densities of pyomelanin producers were >10(6) cells per g wet soil. Pyomelanin demonstrated U complexing and mineral binding capacities at pH 4 and 7. In laboratory studies, in the presence of goethite or illite, pyomelanin enhanced U sequestration by these minerals. Tyrosine amended soils in a field test demonstrated increased U sequestration capacity following pyomelanin production up to 13 months after tyrosine treatments.