砷累積於水稻生長在含洛克沙砷之土壤

Arsenic accumulation by rice grown in soil treated with roxarsone

林清傑(Ching-Chieh Lin)

指導教授 ： 劉振宇

國立臺灣大學/生物資源暨農學院/生物環境系統工程學研究所/博士(2009年)

https://doi.org/10.6342/NTU.2009.00783

摘要

洛克沙砷(Roxarsone,3-nitro-4- hydroxyphenyl)是有機砷劑被廣泛添加於飼料中藉以控制家禽腸道內球蟲病及促進家禽生長，因此導致家禽糞普遍含砷，家禽糞肥通常施用於農田當作肥料使用，一般用於旱田居多，但是中國華南地區將家禽糞肥施用水稻田當作氮肥使用，目前也在推廣水稻田有機栽培，而家禽糞肥為有機肥料之一，家禽糞肥中含砷進入農田後能被作物吸收而導致農產品砷污染可能嚴重危害人體健康，本研究利用水稻(Oryza sativa L.)盆栽試驗於土壤中添加不同含量洛克沙砷(0,25,50,100,200mg/kg)及乾雞糞肥(4t/ha及8t/ha)，以評估洛克沙砷對於水稻農藝參數影響(株高、分蘗數、產量及千粒重)、水稻植物體各部位(根、莖、葉、稻殼及稻米)中砷累積及砷物種含量，實驗結果顯示水稻株高、分蘗數、產量及千粒重隨土壤中洛克沙砷含量增加而明顯減少，土壤中含洛克沙砷200mg/kg導致水稻枯萎，根、莖、葉、稻殼及稻米(糙米)中砷含量隨土壤中洛克沙砷含量增加而顯著增加(P＜0.01)且以無機砷型態存在，土壤中含洛克沙砷100mg/kg之稻米中總砷含量已超過澳洲食品衛生最大容許限值1.0mg/kg標準，土壤中含洛克沙砷25mg/kg之稻米中無機砷含量已中國最大容許限值0.15mg/kg標準。水稻植物體各部位砷累積差異大，在所有處理別之水稻植物體各部位砷含量大小依序為：根＞莖＞葉＞稻殼＞稻米(糙米)。稻根及莖中含As(Ⅲ)(亞砷酸鹽)及As(V)(砷酸鹽)且以As(Ⅲ)為優勢物種，稻葉中含As(Ⅲ)及As(V)但是以As(V)為優勢物，稻殼僅偵測As(V)及稻米(糙米)僅偵測As(Ⅲ)，雞糞肥施用量與稻根中As(Ⅲ)及As(V)無顯著相關。本研究結果顯示土壤中含洛克沙砷25mg/kg以上不僅毒害水稻且造成稻米中無機砷累積經由攝取稻米而提高人體砷暴露風險。

關鍵字

亞砷酸鹽 ； 砷酸鹽 ； 水稻(Oryza sativa L.) ； 雞糞肥 ； 臺灣

並列摘要

Poultry litter is widely used as a fertilizer for lowland rice in Taiwan and China. However, the organic-arsenic compound roxarsone (additive of poultry feed) in poultry litter can be absorbed by the plants and the resulting arsenic (As) contamination may pose a serious threat to human health. This study used various amounts of poultry litter contaminated with roxarsone in pot experiments to evaluate the effect of roxarsone on rice agronomic parameters and the bioaccumulation of total and inorganic As in rice plant tissues. Rice grain yield decreased significantly with increasing As content of the soil, and the critical threshold that killed rice was 200 mg roxarsone kg-1 soil. The As concentrations in root, straw, leaf, husk, and grain increased with increasing soil As (P < 1%). At 100 mg roxarsone kg-1 of soil, the As concentration in the rice grain exceeded the statutory permissible limit of 1.0 mg As kg-1 dry weight and at 25 mg roxarsone kg-1 of soil, the inorganic As concentrations in grains exceeded the statutory limit of 0.15 mg of inorganic As kg-1 in China. For all treatments, the As concentrations in various plant tissues at maturity follow the order: root > stem > leaf > husk > grain. Arsenite was the predominant species in root, straw, and grain, while arsenate was the predominant species in leaf and husk. No significant difference existed between the amounts of arsenite and arsenate when various amounts of poultry litter were applied. This result illustrates that large amounts of added roxarsone are not only toxic to rice but also accumulate in grains in the inorganic As forms, potentially posing a threat to human health via the food chain.

並列關鍵字

arsenate ； arsenite ； Oryza sativa L. ； poultry manure ； Taiwan

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