Abstract
To compare heavy metal phytoavailability in paddy soils near five abandoned mining areas, 4 different soil extractants such as 0.1M-HCl, $0.1M-HNO_3$, 0.05M-EDTA, and 0.005M-DTPA were used. Total acid digestion method $(H_2SO_4:HClO_4:HNO_3)$ was also employed to analyze heavy metal content in 30 paddy soils and brown rice. The rates of extracted heavy metal to total content were in the range of $12.1{\sim}39.1%$ for Cd, $20.5{\sim}45.5%$ for Cu, $10.6{\sim}30.7%$ for Pb, and $6.7{\sim}13.0%$ for Zn. 0.1M-HCl and $0.1M-HNO_3$ extractable both Cu and Pb were relatively less extracted at the high soil pH and extractable calcium site(Mine D) whereas 0.05M-EDTA and 0.005M-DTPA extractable Pb were strongly extracted at the same soils. In case of Cd, Cu, and Zn in soil, 4 types of extractable heavy metals and total content were highly correlated with each other. However, there were positive correlations between 0.1 M-HCl and $0.1M-HNO_3$ extractable Pb as well as between 0.05M-EDTA and 0.005M-DTPA extractable Pb, which were relatively similar extractants in chemical properties. The rates of heavy metals in brown rice to total contents in soils were in the order Zn>Cd>Cu>Pb. Specially, the rate of Cd, Pb, and Zn were lower at the highest level of soil pH and Ex. Ca. Both Cd and Zn in brown rice were positively correlated with those of all soil extractants. It was estimated that the solubility following to the plant uptake of Cd and Zn were higher than those of Cu and Pb considering relationships between all kinds of heavy metal contents in soil and those in brown rice.
토양의 중금속 침출액간의 침출정도 및 유효도를 구명하기 위하여 휴${\cdot}$폐광산 인근 7개 지역 30개 지점 논토양을 대상으로 4종 단일침출법 및 총함량법에 의한 중금속함량 및 같은 지점에서 재배된 현미의 중금속함량을 분석하였다. 토양의 총 중금속에 대한 침출액별 함량비율은 $Cd\;12.1{\sim}39.1$, $Cu\;20.5{\sim}45.5$, $Pb\;10.6{\sim}30.7$, $Zn\;6.7{\sim}13.0%$였고, 특히 토양 pH 및 Ca함량이 높은 지역에서 0.1M-HCl 및 $0.1M-HNO_3$침출성 Cu, Pb의 함량비율이 매우 낮았고 0.005M-DTPA 및 0.05M-EDTA 침출성 Pb은 매우 높았다. Cd Cu 및 Zn의 토양 침출액 및 전함량간의 상호관계는 고도의 정의 상관을 보였으나 Pb은 비슷한 형태를 침출하는 0.1M-HCl과 $0.1M-HNO_3$, 0.05M-DTPA와 0.05M-EDTA만이 상관을 보였다. 토양의 총 중금속에 대한 현미 중 함량비율(Plant metal/Soil metal)은 Zn>Cd>Cu>Pb 순으로 각각 12.41, 10.92, 6.60, 0.06%였고, 특히 토양 pH 및 Ca함량이 높은 지역에서 Cd, Pb 및 Zn의 함량비율이 매우 낮게 나타났다. 토양의 Cd과 Zn함량은 모든 침출액에서 현미와 정의 상관을 보였고, 특히 침출액중 0.1M-HCl이 다른 침출액보다 상관성이 높은 것으로 나타났다. 토양 침출엑별 중금속과 현미와의 관계 및 토양의 총 중금속에 대한 현미중 함량비율로 볼 때 토양내 유효도와 식물로의 흡수이행성은 Cu, Pb보다 Cd, Zn가 높은 것으로 생각되었다.
(National Institute of Agricultural Science and Technology, RDA.)
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