Selenium in a shore bird,the dunlin,from the Dutch Waddenzee

The hypothesis that Se is secreted by birds via the preen gland or salt glands, thus contaminating the feathers, has been investigated. It is concluded that the feather vanes show indirectly in this way the birds' e?posure to Se. Therefore they can be used as an indicator tissue for this element.     

A geologist’s shining path

Chronicle

A geologist’s shining path     

In-well time-of-travel approach to evaluate optimal purge duration during low-flow sampling of monitoring wells

A common assumption with groundwater sampling is that low (<0.5 L/min) pumping rates during well purging and sampling captures primarily lateral flow from the formation through the well-screened interval at a depth coincident with the pump intake. However, if the intake is adjacent to a low hydraulic conductivity part of the screened formation, this scenario will induce vertical groundwater flow to the pump intake from parts of the screened interval with high hydraulic conductivity. Because less formation water will initially be captured during pumping, a substantial volume of water already in the well (preexisting screen water or screen storage) will be captured during this initial time until inflow from the high hydraulic conductivity part of the screened formation can travel vertically in the well to the pump intake. Therefore, the length of the time needed for adequate purging prior to sample collection (called optimal purge duration) is controlled by the in-well, vertical travel times. A preliminary, simple analytical model was used to provide information on the relation between purge duration and capture of formation water for different gross levels of heterogeneity (contrast between low and high hydraulic conductivity layers). The model was then used to compare these time–volume relations to purge data (pumping rates and drawdown) collected at several representative monitoring wells from multiple sites. Results showed that computation of time-dependent capture of formation water (as opposed to capture of preexisting screen water), which were based on vertical travel times in the well, compares favorably with the time required to achieve field parameter stabilization. If field parameter stabilization is an indicator of arrival time of formation water, which has been postulated, then in-well, vertical flow may be an important factor at wells where low-flow sampling is the sample method of choice.     

Soils and stratigraphy of the laddie creek site (48BH345), an altithermal-age occupation in the big horn mountains,wyoming

Haploborolls and Ustifluvents with A-C horizonation characterize Holocene soil development in alluvium and colluvium of the Laddie Creek valley. Cumulic soils with overthickened A horizons, including those of Altithermal age, have formed along the valley walls under the influence of spring activity from the Amsden Formation (Mississippian-Pennsylvanian). Soil texture, mineralogy, and to some extent color, are inherited largely from sediment derived from the Amsden and Tensleep (Pennsylvanian) Formations. The valley was able to support human occupation during Altithermal time (ca. 7500-4000 B.P.) because of springs emanating from the valley walls. Past spring locations are identified from soil morphology and stratigraphy. Springs are still active along the valley, although they have shifted positions many times in the past. The association of spring soils with Altithermal-age occupation at the site (ca. 6600-5700 B.P.) does not coincide with the caliche concept of the Altithermal paleosol in Holocene alluvial valleys in Wyoming basins as identified by Leopold and Miller. Nevertheless, early man of Altithermal time probably sought higher elevations within mountains of the region where springs offered water and the environs provided food and shelter—thus enabling human groups to survive the drought, and possible high temperatures, which seemingly prevailed in the basins and plains.     

Botswana gravity reference net

Gravity reference stations for the National Gravity Survey of Botswana have been established at twenty-three sites throughout the country in a net linked to existing bases in South Africa, Kenya and Zambia with an internal accuracy of better than 0.5 gravity units (one gravity unit, gu, equals an acceleration of 10⁻⁶ m.s⁻²). The field procedure and reduction of data are explained and a list is given of the gravity values.