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.