DIAZINON ABSORPTION AND BIOACCUMULATION IN THE GARDEN RADISH (RAPHANUS RAPHANISTRUM SSP. SATIVUS)

Abstract

In order to evaluate the absorption and bioconcentration profiles for diazinon (DZN) in the garden radish, radishes were grown in DZN-containing soil under two sets of conditions: early exposure and late exposure. In early exposure, seeds were planted in contaminated soil that DZN levels immediately after seeding ranged from 843-6650 ng/g-ww. DZN levels during growing period ranged from 2.11-2050 ng/g-ww in soil and from undetectable to 360 ng/g-ww in radish. In late exposure, seeds were planted in normal soil, to which DZN was added 28 days later. DZN levels in soil and radish ranged from 1480-9080 ng/g-ww and 110-3280 ng/g-ww. The levels of DZN in the roots and leaves were higher than those in the stems. The relationship between DZN levels in soil and radishes observed in these experiments were strongly positive, with radishes taking up greater quantities of DZN the higher its concentration in soil. The concentration factor (radish-to-soil; Cr/Cs) decreased at an exponential rate with days elapsed since DZN addition. This suggests that the degree of DZN taken up by radishes is influenced by exposure time. Based on the findings for the time course of tissue-specific DZN concentration ratios and DZN contents, it seems that DZN in the soil were absorbed through the roots, and then transported through the stem into the leaves: after this, DZN primarily bioaccumulates in the garden radish in its roots and leaves circulating within the plant.