Stable Isotope Techniques for Assessing Labile Cu in Soils:Development of an L-Value Procedure,Its Application,and Reconciliation with E Values

摘要

Isotopic techniques have become a valuable tool for assessing the lability or potential availability of elements in soil.Until now,work on soil Cu has been limited to E-value methods where soil solution extracts are obtained by physical means due to the very short (12.4 h)half-life of the radio isotope ~(64)Cu.However,a stable isotope method has recently been developed for determining soil Cu E values that utilizes enhancement of the ~(65)Cu isotope in soil and measurement of the subsequent ratio with ~(65)Cu.We have developed an L.-value technique for soil Cu,where plants are used to sample the soil solution and therefore give a direct measure of the plant available Cu.The L.-value technique developed was then compared,and found to be equivalent,with E values using equilibration periods up to and including the growth period of plants in the L.-value method.