Radiochlorine concentration ratios for agricultural plants in various soil conditions

Long-term field experiments have been carried out in the Chernobyl exclusion zone in order to determine the parameters governing radiochlorine ( 36Cl) transfer to plants from four types of soil, namely, Podzoluvisol, Greyzem, Phaeozem and Chernozem. Radiochlorine concentration ratios (CR = concentration of 36Cl in the fresh plant material divided by its concentration in the dried soil in the upper 20 cm layer) were obtained in green peas (2.6 ± 0.4), onions (1.5 ± 0.5), potatoes (8 ± 1), clover (90 ± 26) and ryegrass (158 ± 88) hay, oat seeds (36 ± 23) and straw (305 ± 159), wheat seeds (35 ± 10) and straw (222 ± 82). These values correlate with the stable chlorine values for the same plants. It was shown that 36Cl plant/soil CR in radish roots (CR = 9.7 ± 1.4) does not depend on the stable chlorine content in the soil (up to 150 mg kg −1), soil type and thus, that stable chlorine CR values (9.4 ± 1.2) can also be used for 36Cl. Injection of additional quantities of stable chlorine into the soil (100 mg kg −1 of dry soil) with fertilizer does not change the soil-to-plant transfer of 36Cl. The results from a batch experiment showed that chlorine is retained in the investigated soils only by live biota and transfers quickly (in just a few hours) into the soil solution from dry vegetation even without decomposition of dead plants and is integrated in the migration processes in soil.