鉻、鎳高濃度土壤中生物可及性、移動性與土壤性質相關性探討

土壤重金屬污染對健康和生態造成不可忽視的影響，兒童因手口行為誤食重金屬污染塵土是值得關切的重要暴露途徑，然而目前風險評估以重金屬總量進行評估時有高估之虞，若以動物實驗模擬重金屬污染物進入人體循環系統之實際吸收劑量過於耗時和耗費，遂發展體外實驗方法評估生物可及性（Bioaccessibility, BA）。本研究採集7個鉻、鎳高濃度表土，污染來源包括地質因素、非法棄置和工業廢水，以生理萃取試驗法（Physiologically Based Extraction Test, PBET）和簡化生物可及性萃取法（Simplified Bioaccessibility Extraction Test, SBET）分析其生物可及性，調查土壤基本性質和鉻、鎳的化學相態，進一步探討生物可及性與土壤基本性質和BCR序列萃取相態（分為F1: 酸可溶及交換態；F2: 可還原結合態；F3: 可氧化結合態；F4: 殘餘態）的相關性。實驗結果顯示，7個污染場址的表土濃度皆超過管制或監測標準（鉻：205.6‒3095 mg kg-1；鎳：168.7‒2596 mg kg-1）；鉻主要為殘餘態，而鎳的移動性較鉻高，依污染來源和污染齡使相態分佈有所差異；生物可及性方面，胃相分別為SBET（鉻：5.164%；鎳：12.01%）和PBET（鉻：2.955%；鎳：10.43%），約比腸相（鉻：0.5159%；鎳：1.057%）高10倍，鎳不論胃相或腸相均比鉻高。以SBET之生物可及性結果做線性迴歸相關性分析，鉻生物可及性與土壤pH值、Clay（%）、Total content(TC)和F1+F2相關，最佳複迴歸模式為Cr-BASBET(%)=-25.214+0.008 TC+0.122 Clay + 1.201 (F1+F2)，R2為64.6％（p<0.001）；鎳生物可及性與土壤pH值Clay（%）、F2、F1+F2和 F1+F2＋F3相關，最佳複迴歸模式為Ni-BASBET(%)=-11.630+0.614Clay+0.312 (F1+F2)，R2為69.2％（p<0.001）。本研究所得之生物可及性和土壤特性等資訊，可提供相關主管單位在鉻、鎳污染場址的基線資料。

關鍵字

鉻；鎳；生物可及性；序列萃取法；蛇紋岩土壤；污染土壤

並列摘要

Heavy metal contaminations are detrimental to both ecosystem and human health. Children are exposed to contaminated soils via hand-to-mouth behavior. Polluted soil ingestion is a risk to health. Most current risk assessment is based on total metal content; however, only a fraction of total content are available for uptake. Performing animal experiments on bioavailability are highly costy and time-consuming. Therefore, in-vitro experiments on bioaccessibility are conducted in preference to in-vivo assays. In this study, we collected 7 high-concentration Cr and Ni-containing soils, from geogenic and anthropogenic sources, and investigated the bioaccessibility via PBET and SBET, mobility via BCR sequential extration (F1: Acid-exchangeable fraction; F2: Fe-Mn oxide bounded fraction; F3: Oxidation fraction; F4: Residual fraction), and correlation of bioaccessibility, mobility and soil property. The results indicated that, all aqua regia extractable concentractions of Cr (205.6‒3095 mg kg-1) and Ni (168.7‒2596 mg kg-1) were higher than the guideline values. High percentage of Cr was in residual fractions. The mobility of Ni was higher than Cr and affected by pollutant sources and age. Bioaccessibilities in gastric phase, SBET (Cr: 5.164%；Ni: 12.01%) and PBET (Cr: 2.955%；Ni: 10.43%), were about 10 times than those in intestinal phase (Cr: 0.5159%；Ni: 1.057%). Cr bioaccessibility was lower than Ni. Linear regression analysis was carried out on correlation of SBET bioaccessibility, BCR results, and soil property. Trend in bioaccessible Cr related on soil pH value, clay (%), total content (TC) and F1+F2. The best regression model was Cr-BASBET(%)=-25.214+0.008 TC+0.122 Clay + 1.201 (F1+F2), R2=64.6％ (p<0.001). In Ni bioaccessibility, soil pH value, Clay (%), F1+F2 and F1+F2+F3 affected available extractions. The best regression model was Ni-BASBET(%)=-11.630+0.614Clay+0.312 (F1+F2)，R2=69.2％（p<0.001）. This study provides baseline information for government on management strategies formulated.

並列關鍵字

Cr ； Ni ； Bioaccessibility ； Sequential extraction ； Serpentine soils ； Anthropogenic sources

參考文獻

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Alloway, B. J. (2013). Heavy Metals in Soils, Springer. London. doi. org/10.1007/978-94-007-4470-7.

Bakircioglu, D., Kurtulus, Y. B., & Ibar, H. (2011). Investigation of trace elements in agricultural soils by BCR sequential extraction method and its transfer to wheat plants. Environmental Monitoring and Assessment, 175(1), 303-314.

Basta, N., & Gradwohl, R. (2000). Estimation of Cd, Pb, and Zn bioavailability in smelter-contaminated soils by a sequential extraction procedure. Journal of Soil Contamination, 9(2), 149-164.

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鉻、鎳高濃度土壤中生物可及性、移動性與土壤性質相關性探討

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