The soil locally referred to as a purplish clayey soil(PCS)

which was sampled in Deqing County

Zhejiang Province. Both laboratory and greenhouse pot experiments were conducted to investigate availability of soil Hg to crop plants in a rice-cabbage-radish rotation system. Four extractants including 0.1 M hy-drochloric acid(HC1)

1 M ammonium acetate(NH4OAc

pH=7.0)

0. 005 M Diethylenetriaminepentaacetic acid(DTPA)

and 0.1 M calcium chloride(CaC12

pH=5.0) were compared for their adequacy in estimating mercury(Hg) availability to crop plants. The results show that the amounts of Hg extracted by each of the four procedures increased with extraction time. The optimal time required for extraction of soil Hg was ap-proximately 30 min the time

however

varied slightly among the four extractants. The amounts of extrac-ted Hg increased with decreasing soil/solution ratio

and a soil/solution ratio of 1~5 appeared to be adequate for soil Hg availability tests. The amounts of extracted Hg decreased in the order of used extraetants as CaC12＞HCl＞NH4OAc＞DTPA. Extractable soil Hg determined using the four extractants were correlated with each other positively significantly

especially between CaC12 and NH4OAc. Significant correlations were also found between extractable Hg in the soil and total Hg concentrations in edible tissues of rice and radish

except for cabbage. Overall

the 0.1 M CaC12 extraction provided the best estimation of available Hg in the soil and could be used to estimate phytoavailability of Hg in the rice-cabbage-radish rotation system.