N. TongtaveeJ. ShiowatanaRonald G. McLarenColin W. GrayMahidol UniversityLincoln University, New Zealand2018-06-212018-06-212005-09-15Science of the Total Environment. Vol.348, No.1-3 (2005), 244-256004896972-s2.0-24644509350https://repository.li.mahidol.ac.th/handle/20.500.14594/16515Isotope dilution methods using a stable isotope tracer (207Pb) were developed for the determination of Pb availability in contaminated soils. The methods included determination of E values (isotopically exchangeable pool), L values (plant labile pool) and isotopic exchange kinetics (IEK). Isotopically exchangeable Pb was monitored at different exchange times based on measurement of the207Pb/208Pb ratio in soil solution following addition of the tracer. The rate of decrease in the207Pb/208Pb ratio in solution could be described by using the same IEK equation as used previously with radioisotope tracers. The amounts of isotopically exchangeable Pb in Pb-contaminated soils estimated from long-term IEK parameters were in good agreement with directly determined E values up to 15 days. However, values of some of the fitted IEK parameters cast doubts on the validity of using the IEK approach with207Pb, most probably as a result of irreversible fixation of some of the spike by reactive surfaces in the soils. Estimation of isotopically exchangeable Pb using short-term kinetics data was unsuccessful, substantially underestimating E values. Results for the control (uncontaminated) soil were highly variable, most probably as a result of fixation of tracer by the soil and poor analytical precision due to low solution Pb concentrations. A compartmental analysis of the variation in E values with time indicates a good potential for estimating bioavailable Pb in contaminated soils. The amounts of available Pb obtained from summation of the E1minand E1 min-24 hpools (E(available)), accounting for an average of 57.62% of total soil Pb, were significantly correlated with both the L values and with Pb extracted from soil with EDTA. © 2005 Elsevier B.V. All rights reserved.Mahidol UniversityEnvironmental ScienceArticleSCOPUS10.1016/j.scitotenv.2004.12.066