以化學萃取及添加改良劑來評估受砷污染土壤之生物有效性

Assessment of bioavailability by chemical extraction and stabilizer addition on arsenic-contaminated soils

黃信融(Shin-Rung Huang)

指導教授 ： 薩支高

國立屏東科技大學/工學院/環境工程與科學系所/碩士(2010年)

https://doi.org/10.6346/NPUST.2010.00131

摘要

根據調查顯示，臺灣地區部分農地土壤之砷含量已達土壤污染管制標準，受砷污染之土壤可能造成環境及人體健康風險。本研究以人工配製含砷之污染土及採集現地污染土，進行序列萃取評估砷形態分布，並利用酸及改良劑萃取試驗，藉以評估不同萃取劑、改良劑及0.1 N HCl對砷之萃取成效與萃取形態。最後評估天然背景砷濃度偏高之農地成因，並利用時間與空間探討砷天然污染分布潛勢。
研究結果顯示，萃取劑以1 M H3PO4較佳萃取範圍為1.27-19.55 mg/kg；改良劑以1 %硫酸亞鐵較佳釋出範圍為0.43-10.24 μg/kg；模擬根系土壤pH之0.1 N HCl萃取範圍為3.2-65.6 μg/kg。根據不同序列萃取結果，顯示酸萃取可有效萃取土壤中弱鍵結態砷(交換態、碳酸鹽態及有機物態)及增加砷移動性，而改良劑添加處理後，可降低弱鍵結態砷之移動性，0.1 N HCl萃取效果近乎於砷之水溶態。
以不同農地水稻分蘗期根系土壤與植體(根、莖及葉)分析，砷含量皆隨著離出水口距離增加而降低，可判斷造成該農地自然背景砷含量偏高之原因可能為地質因素。深入探討自然背景砷含量偏高之農地，利用水稻黃熟期更多不同距離、深度及水稻作物之土壤與植體樣品分析，證實表土砷移動性會隨著離出水口距離增加而降低，植體各部位砷含量皆為根＞莖＞葉＞穀粒，而食用部位穀粒砷含量最高為0.26 mg/kg。水稻黃熟期植體於砷污染土之生物累積因子(Bioaccumulation Factor, BAF)皆低於轉移係數(Translocation Factor, TF)，表示水稻作物植生萃取能力低，但根部轉移到收穫部位能力較高。

關鍵字

砷 ； 土壤酸萃取 ； 序列萃取法 ； 改良劑

並列摘要

Some Taiwan farmland soil had been found to contain high arsenic concentration to the soil control standard. Soil arsenic contamination might cause environment and/or human health risks. In this study, arsenic spiked soils and high arsenic background soil samples were collected to carry out sequential extraction procedures (SEPs) assessment. Acid (0.1N HCl and other acids) extraction as well as stabilizers addition were used to evaluate the extraction/stabilization efficiency. Finally, a high arsenic background farmland was used to study the causes, arsenic space distribution and potential distribution in rice.
We found in this study that 1M H3PO4 is the best extracting solution which can remove 1.27-19.55 mg/kg of arsenic form soils. The difference of SEPs before and after acid extraction and stabilizer addition showed that acid extraction can effectively remove unstable (exchangeable, carbonate and organic) arsenic forms from soils, and also increase the mobility of soil arsenic. Stabilizers addition can reduce unstable arsenic forms releasing. Only 0.43-10.24 μg/kg of arsenic released while using the best stabilizer, 1% ferrous sulfate. 0.1N HCl was used to simulated rhizosphere pH that can extract 3.2-65.6 μg/kg of arsenic form soils. This is similar to the water soluble form.
In this study, we identified the high soil background arsenic was come from irrigation groundwater well. Arsenic concentration were lower as the distance from well were longer, and its mobility in topsoil is low. Arsenic in edible parts of grains was found to be high to 0.26 mg/kg, and its distribution in rice was as follow: roots> stems> leaves> grains. Bioaccumulation Factor (BAF) of arsenic on rice ripening stage were lower than the transfer coefficient, Translocation Factor (TF). It means that arsenic can be hardly absorbed from soil to roots, but easily transferred from roots to grains.

並列關鍵字

arsenic ； acid extraction ； sequential extraction ； stabilizer

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