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چکیده
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Heavy metal bioaccumulation in earthworms can be used as an ecological indicator forheavy metal contamination in soils. In this study, the levels of Pb and Cd were analyzed in the body tissues of two endogeicearthworm species:Aporrectodeacaliginosaand A. roseacollected from three agricultural soils (turnip cabbage, beet, and fallow).At each system, soil samples for earthworm hand-sorting (quadrats of 5050×25 cm) and analyses of organic matter and metal contents together with those of edible parts of agricultural plants were randomly collected at each field. The amounts of heavy metals were measured using flame atomic absorption spectrophotometry, organic matter content by loss on ignition (at 550 ºC for 4h) and soil Ca concentrationsby Systronics Flame Photometer.The results showed that A. caliginosa was the dominant species in the turnip cabbage cropland, whereas A. rosea was dominant in the beet farmland; however, in the fallow system, both species had similar densities. The concentrations of Cd and Pb in earthworms were higher in the croplands than in the fallow. The concentrations of both Cd and Pb were significantly higher in the A. caliginosaspecimens collected fromtheturnip cabbage and fallow lands, than in the soil samples from the same sites. By contrast, no significant differences were observed in the metal accumulations of the earthworm speciescollected from the fallow, although higher levels of Pb and Cd were measured in A. rosea and A. caliginosa, respectively. In addition, we found that the Pb concentration in earthworms was negatively correlated to calcium concentration in the soils, whereas the significant increase inorganic matter contents observed inthe soils withturnip cabbage (compared to the fallow) led to a higher accumulation of Cd in A. rosea; the opposite trend was observed for Pb accumulation in A. caliginosa. These results suggest that crop identity, calcium concentrations and organic matter contentsplay a key role in the uptake of heavy
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