Abstract
This study was conducted to compare fractionations and availability of heavy metal in paddy soils near five abandoned mining areas. The sequential extraction procedure was used to fractionate the heavy metals in soils into the designated from water $soluble(H_2O)$, $exchangeable(0.5M\;KNO_3)$, organically bound(0.5M NaOH), $oxide/carbonate(0.05M\;Na_2-EDTA)$, and $sulfide/residual(4M\;HNO_3)$. EDTA and $HNO_3$ extractable of Cd, Pb, and Zn, and NaOH and $HNO_3$, extractable of Cu were predominant chemical forms. The ratio of $H_2O+KNO_3$ extractable of Cd, Zn, Cu, and Pb were 25.1, 8.7, 4.0, and 0.4%, respectively. The ratio of $H_2O+KNO_3$ extractable heavy metal were negatively correlated with soil pH, while $EDTA+HNO_3$ extractable heavy metal were positively correlated. The most consistent distribution patterns were found when the soil samples were grouped according to their total contents. Specially, the ratio of $H_2O+KNO_3$ extractable heavy metal were higher as total contents of heavy metal were increased. The ratio of $H_2O+KNO_3$ extractable heavy metal(Cd 1.06, Cu 0.15, Pb 0.01, and Zn 0.05%) were lower at the high soil pH than those(Cd 31.31, Cu 4.06, Pb 1.75, and Zn 10.16%) at the low level. Compared to other chemical forms, the degree of contribution for $KNO_3$ extractable form to the Cd uptake to brown rice was high, whereas that for EDTA and $HNO_3$ extractable forms were high to the Zn.
광산인근 논토양의 형태별 중금속 함량[수용태$(H_2O)$, 치환태 $(0.5M\;KNO_3)$, 유기복합태(0.5M NaOH), 탄산염태$(0.05M\;Na_2-EDTA)$, 황화잔류태$(4M\;HNO_3)$] 과 현미에 흡수 이행된 중금속과의 관계를 구명하기 위하여 5개 광산지역에서 30개 지점 논토양 및 현미를 대상으로 분석 검토한 결과는 다음과 같다. 광산인근 논토양의 Cd, Pb 및 Zn의 주된 형태는 EDTA 및 $HNO_3$ 침출태, Cu는 NaOH 및 $HNO_3$침출태였고, 식물에 흡수이행이 용이한 것으로 알려진 $H_2O\;+KNO_3$침출태의 함량비율은 Cd 25.1, Zn 8.7, Cu 4.0, Pb 0.4% 순으로 나타났다. 토양 pH와 $H_2O+KNO_3$침출태 중금속 함량비율은 고도의 부의 상관, $EDTA+HNO_3$침출태 중금속과는 고도의 정의 상관을 보였다. 토양의 총 중금속함량 수준에 따라 형태별 중금속함량의 분포비율은 다르게 나타났고, 특히 높은 함량수준에서 $H_2O+KNO_3$침출태 Cd, Cu, Pb 및 Zn의 분포비율이 높게 나타났다. 토양의 $H_2O+KNO_3$침출태 Cd, Cu, Pb 및 Zn함량비율은 토양 pH가 높은 지역(D site)에서 각각 1.06, 0.15, 0.008, 0.05%로 나타나 pH가 낮은 지역의 평균치 30.31, 4.06, 1.75, 10.16%보다 매우 낮게 나타났다. 현미중 Cd 및 Zn흡수이행과 관련이 큰 토양의 존재형태는 각각 $KNO_3$침출태, EDTA 및 $HNO_3$침출태로 나타났다.
(National Institute of Agricultural Science and Technology, RDA.)
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