Migration and chemical availability of ¹³⁷Cs and⁹⁰Sr in the long-term was studied on a36-yr-old deposition experiment on pastureconsisting of a sandy soil and a clay soil,contaminated in 1961 with radionuclides in aqueoussolution. Comparisons were made with a study of thesame soils in 1967. Soil samples to 55 cm depth wereanalysed for ¹³⁷Cs and ⁹⁰Sr to establish thevertical distribution. Chemical availability wasstudied using sequential extractions with H₂O,NH₄Ac, NH₂OH·HCl, H₂O₂ andHNO₃. Both ¹³⁷Cs and ⁹⁰Sr were found atall depths in both soil types. Cs-137 waspredominantly retained within the upper 10 cm (70%)in both soils. For ⁹⁰Sr, the soils differedsignificantly, retention within the upper 10 cm was27% in sandy soil and 47% in clay soil. Migrationsince 1967 was faster in the sandy soil for bothnuclides. More than 95% of ¹³⁷Cs was bound inthe acid-digestible and residual fractions in bothsoils. The residual fraction was larger in clay soil.⁹⁰Sr was highly available in both soils. Noresidual fraction was found, and the easilyexchangeable fraction was 63–75%.

To compare the soil remediation effectiveness of saltsof weak organic acids with strongchelating agents, three soils of different textures,all polluted by heavy metals, were washed in a column,at optimum pH, with salts of weak organic acids,namely, citrate, tartarate or oxalate + citrate orchelating agents (EDTA or DTPA). For the clay loam,Cr, Mn, Hg and Pb were removed by citrate andtartarate at levels of 43 to 45, 37 to 41, 91 to 92and 75%, respectively. EDTA and DTPA effectivelyleached only Pb after 20 pore volumes. For the loam,citrate leached 98 and 89% of Cd and Pb after 20 porevolumes, respectively, while tartarate leached out 91and 87% of Cd and Pb. EDTA and DTPA removed 93 to97% of these metals after 20 pore volumes. For thesandy clay loam, 84 to 91, 73 to 84, 56 to 70 and 72to 81% of Cd, Cu, Pb and Zn were removedrespectively, by citrate and tartarate. EDTA and DTPAremoved 93 to 97% of these metals after 20 porevolumes. An in situ soil remediation simulation wasalso tested using the sandy clay loam in a tub. After12 hr of retention, the citrate solution washed 81, 82,73 and 90%, of Cd, Cu, Pb and Zn, respectively, aftersix pore volumes. EDTA and DTPA effectively removedall heavy metals, except for Hg, but also extractedlarge quantities of soil nutrients and pollute thesoil by being adsorbed on the soil particles. Thesalts of citrate and tartarate effectively removed theheavy metals from the three polluted soils whileleaching little macro-nutrients and improving soilstructure. Each soil reached C and B levels ofsoil-clean-up criteria after 10 to 20 pore volumes andwithin 10 to 15 hr of flushing.