Showing items related by title, author, creator and subject.

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  Radiocarbon Sample Preparation at the Circe AMS Laboratory in Caserta, Italy

  Passariello, Isabella; Marzaioli, Fabio; Lubritto, Carmine; Rubino, Mauro; D'Onofrio, Antonio; De Cesare, Nicola; Borriello, Gianluca; Casa, Giovanni; Palmieri, Antonio; Rogalla, Detlef; et al. (Department of Geosciences, The University of Arizona, 2007-01-01)

  A system with several lines for the preparation of graphite targets for radiocarbon analysis has been built at the new accelerator mass spectrometry (AMS facility in Caserta, Italy. Special attention has been paid in the design to the reduction of background contamination during sample preparation. Here, we describe the main characteristics of these preparation lines. Results of tests performed to measure 14C background levels and isotope fractionation in several blank samples with the Caserta AMS system are presented and discussed.
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  Radiocarbon Dating Recent Volcanic Activity on Faial Island (Azores)

  Madeira, José; Monge Soares, A. M.; Brum da Silveira, António; Serralheiro, António (Department of Geosciences, The University of Arizona, 1995-01-01)

  Recent fieldwork on the island of Faial (Azores) led to the establishment of a detailed volcanic stratigraphic sequence, which is composed of five main geological formations. One of them, the Caldeira Formation, comprising mainly pumice fall and flow deposits, was judged to be Holocene in age. Organic materials were found preserved in or below some of the pyroclastic deposits from this formation. Wood, charcoal, peat and soil samples were radiocarbon dated, permitting correlation of deposits from different sequences and the establishment of a chronological framework for the Caldeira volcanic activity. These materials yielded ages from ca. 10-1 ka BP. The average dormant interval in the Caldeira pyroclastic activity from 4-1 ka ago is ca. 400 yr, with eruptions approximately every 200-800 yr. This frequency of activity indicates that the Caldeira volcano is an active, dangerous structure that should be closely monitored.
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  Fertilization with nitrogen and potassium on pastures in temperate areas

  Mosquera-Losada, María Rosa; González-Rodriguez, Antonio; Rigueiro-Rodríguez, Antonio (Society for Range Management, 2004-05-01)

  Fertilizer application enable producers to influence pasture production. The effect of N fertilization on grass production and leguminous plant content of pasture and strategic N application has received much attention. Changing agricultural policies suggest that chemical fertilizer inputs may be diminished and that alternative sources of nutrients are desired. The aim of this study was to evaluate the effect of N and K fertilization on production, botanical composition, and forage mineral composition to gain some insight into what influence changing fertilization practices would have on pasture productivity. Three K and 3 N application rates were applied in a factorial design on a white clover (Trifolium repens L.)—perennial ryegrass (Lolium perenne L.) sward. Potassium and nitrogen application increased herbage production and had differential influences on botanical composition. Nitrogen decreased clover content in the pasture, whereas K increased the proportion and production of white clover. The effects of K application appeared later in the experiment than those associated with N. We concluded that K is very important for development and maintenance of white clover in pasture, which increases herbage and protein production. Nitrogen was associated with lesser amounts of N, P, K, and Mg in pasture, because of lesser amounts of clover in the sward. Changing fertilization practices will have definite influences on sward composition and pasture productivity. Any interpretation of pasture mineral content should take botanical composition changes into account.