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Papers by Carol-ann Craig

Plant and Soil, 2013

Background and aims The sustainability of forest ecosystems may be at stake especially in forests... more Background and aims The sustainability of forest ecosystems may be at stake especially in forests on basepoor soils due to reduced nutrient deposition and intensified silvicultural practices. Understanding nutrient availability and cycling is therefore essential to manage forest soil fertility. This study aims to assess in a beech plot Mg and Ca vertical transfer in soil and root uptake using an isotopic tracing experiment. Methods A simulated rainfall containing a small amount (960 gMg.ha −1 ; 530 g Ca.ha −1 ) of highly enriched 26 Mg and 44 Ca was sprayed on the forest floor of a 35-yr-old beech plot. The isotopic composition of fine roots and of the soil exchangeable Mg and Ca pool was monitored during 1 year. A pool and flux model (IsoMod) was developed to predict the labeling of the soil and vertical transfer of tracers. Results Tracers ( 44 Ca and 26 Mg) were immediately retained in the thin litter layer. During the following year, Mg and to a lesser extent Ca were progressively released. After 1 year, the exchangeable Mg and Ca pools of the upper mineral layer (0-5 cm) were strongly labeled (~660‰, representing~55 % of the tracer input and~370‰,~41 % of the tracer input respectively). A significant proportion (~8 % 26 Mg,~2 % 44 Ca) of tracer was leached through the soil, below 10 cm. This amount was much larger than what was predicted using a simple mixing model. The Ca and Plant Soil

Journal of Analytical Atomic Spectrometry, 2003

We present an advanced method to produce accurate and reproducible U and Th isotope data for carb... more We present an advanced method to produce accurate and reproducible U and Th isotope data for carbonate geochronology using very small sample sizes. We analysed speleothem, marine calcite and coral samples by MC-ICP-MS and compared the data and its precision to U and Th data obtained by TIMS using the same samples. MC-ICP-MS needs between 0.05 and 0.34 ng of Th compared with 0.3-1.4 ng Th for TIMS analyses to obtain comparable precision. No separation of Th and U is necessary because of U and Th recoveries of circa 100% and 75-100%, respectively. Th and U analyses are carried out for a range from masses 228 to 238 in two separate runs, with mass 230 Th on the Daly detector for measuring Th isotope ratios and 234 U on the Daly detector for measuring U isotope ratios. Silicate rock standard '' Latite'' (TML) 235 U/ 238 U ratios are used to correct for instrumental mass bias. For calibrating the gain of the Daly and Faraday detectors (Daly-Faraday gain), a 1 ppt Aldrich U solution spiked with 233 U-236 U double spike is measured with mass 235 U in the Daly detector. We demonstrate the accuracy and precision of our analytical data obtained for standard solution UCSC-Th-A, the TML and eleven spiked TML samples over the past 10 months. Literature data obtained by both TIMS and MC-ICP-MS lie well within the error of our UCSC-Th-A 230 Th/ 232 Th value of 0.000 005 85 ¡ 5 (2 sd, n~29). Our ( 234 U/ 238 U) and ( 230 Th/ 238 U) activity ratios for the TML compare well with results of other MC-ICP-MS studies. Our external precision of 230 Th/ 232 Th and 234 U/ 238 U ratios for the unspiked TML is slightly worse than other MC-ICP-MS studies, but reflects either significantly smaller sample sizes or much shorter time for measurement.

Journal of Analytical Atomic Spectrometry, 2000