English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Radionuclides produced primarily by neutron activation of naturally occurring stable elements and chemical additives in nuclear-reactor coolant water are discharged into the Columbia River at the Hanford Reservation of the U.S. Atomic Energy Commission. In the river, the radionuclides associate with sediment and biota or remain in solution and subsequently are distributed downstream throughout the river system and the Columbia River estuary to the Pacific Ocean. To provide information on the distribution of radioactivity in the estuary, the physical and radiological character of the streambed was investigated in 1965. Gross gamma radiation was measured in situ, and surficial samples and cores were obtained with specially designed equipment at 14 cross sections between Longview, Wash., near Columbia River mile 65.8, and the estuary mouth. To facilitate data interpretation, the estuary is divided into geomorphic classes termed "channels," "slopes," and "flats" and into longitudinal divisions called fluvial, transitional, and marine. Grouping data obtained within the same class and division improves correlations significantly, but additional classes are necessary. In situ gross gamma radiation varies over a seventyfold range and generally correlates with the total concentration of individually measured radionuclides in surficial samples. The most abundant radionuclides measured in samples from the estuary are Cr51 , Zn<&, K4<>, Sc , Ru106, Mn^, Co«>, and Zr95-Nb95. Concentrations of Cr51 and Zn6° in surficial sediment are approximately 6.2 and 2.2 times, respectively, greater than the concentration of naturally occurring K40 , which averages about 14 picocuries per gram of sediment; the other measured radionuclides are substantially less abundant than K40 . Radionuclide concentrations vary greatly from place to place, and even when samples in common geomorphic classes and longitudinal divisions are grouped, standard deviations generally are so large that positive conclusions relative to changes in individual radionuclide concentrations along the estuary cannot be made with confidence. Chromium51, however, appears to increase relative to Zn65 toward the mouth of the estuary, and radionuclide concentrations are generally higher on slopes and flats than in channels. The stratigraphic distribution of radionuclides also varies considerably. Radionuclides tend to be distributed to the greatest depths in channels and on slopes and may extend more than 60 inches below the bed surface. However, on the average, 66 percent of the total amount of measured radionuclides (excluding K40 ) is contained in the upper 8 inches of the streambed. Ordinarily, highest concentrations are at the surface or a few inches below. The total amount of measured radioactivity (excluding K40 ) in the sediment column beneath the bed surface ranges from about 0.05 to 15 microcuries per square foot. In the estuary as a whole, sediments in the channels are coarsest, sediments on the flats are finest and have the most positively skewed distributions, and sediments on the slopes are intermediate in size and have the least skewed textural distributions. Within each longitudinal division these same trends exist; however, channel sediments are finest in the transitional division and coarsest in the fluvial division. Sediments on slopes tend to have the same textural characteristics throughout the estuary, but sediments on flats are finest in the fluvial and marine divisions. Cores indicate that estuary sediments are stratified, that a thin fine-grained layer caps many cores that otherwise are essentially sand, and that variations in sediment texture with depth are large at some locations. Sediment composition influences the level of radioactivity to a high degree. The total concentration of measured radionuclides (excluding K40 ) increases as the sediment decreases in size and becomes less well sorted and as the textural distribution of the sediment becomes more skewed toward fine material. Computations based on relations between mean particle size and radioactivity in surficial sediment samples indicate that Zn65 concentrations associated with individual size separates decrease in a downstream direction. An inventory of the amounts of radionuclides in the bed was computed using maps that divide the estuary into nine areas in which the level of radioactivity near the surface and the stratigraphic distribution of radionuclides are similar. In situ radioactivity and general relations among radionuclide content, geomorphic expression, and sediment composition were used in preparing the maps. The inventory shows that at the time of the survey (June 1965) the amount of measured radionuclides (excluding K40 ) was 8,700 curies and consisted of 5,300 curies of Cr51 , 2,100 curies of Zn<®, and 1,300 curies of other activation products and fallout. The estuary appears to contain about one-quarter of all the radionuclides in the reservoir (river, estuary, and ocean) below Vancouver, Wash. Approximately 15, 48, and 37 percent of the total amount of measured radionuclides is in the marine, transitional, and fluvial divisions, respectively, and

Distribution of radionuclides in bottom sediments of the Columbia River estuary