影響台灣烏腳病疫區含砷地下水砷移動因素之探討

地下水中砷的汙染，在世界各地皆造成嚴重的人體危害，而導致地下水中砷濃度升高的因素，仍有待探討。台灣等許多國家的研究發現，砷汙染案例多位於農業用地，然而農業行為中肥料的施用對地下水中砷移動性的影響，尚未明確。本研究的主要目的有二，一為調查台灣烏腳病疫區與非烏腳病疫區間微生物族群的差異；二為研究烏腳病疫區土壤樣品中，肥料的施用與微生物，對於砷由底泥釋放至地下水之影響。本研究分別使用烏腳病疫區與非烏腳病疫區之底泥，添加無機氮肥與磷肥後，並培養於好氧與厭氧環境2及4個月。研究結果顯示，經過2個月的培養，烏腳病疫區與非烏腳病疫區之樣品，顯示相當不同的微生物群相。當添加25與100 mg/L磷肥並培養於厭氧環境4個月，人工地下水中的砷濃度明顯的增加，其中三價砷的濃度由66.4 ± 4.6 μg/L (未添加磷肥的未滅菌樣品) 上升至 81.6 ± 8.6 (添加25 mg/L磷肥的未滅菌樣品) 及110.5 ± 6.0 μg/L (添加100 mg/L 磷肥的未滅菌樣品)。相反的，添加氮肥的樣品並未顯示出砷移動性的增加。本研究同時也發現，在高砷濃度的磷肥樣品中，鐵、錳、鉀、納、鈣與鎂的濃度也相對增加，說明上述元素極有可能參與砷的釋出反應。除此之外，透過微生物群相的分析，本研究發現隨著人工地下水樣品中砷濃度的上升，優勢物種由α-Proteobacteria 轉變成β-及γ-Proteobacteria。本研究提供直接的證據，顯示磷肥與微生物的存在皆可調控烏腳病疫區中的砷由底泥釋出至地下水，故本研究建議，農業上肥料的施用行為須顧及其導致地下水砷汙染之潛在可能。

關鍵字

砷；移動性；烏腳病；肥料；地下水；微生物群相

並列摘要

Arsenic (As) contamination of groundwater is a worldwide public health concern. Arsenic affected areas in Taiwan were reported mostly in farmland, yet the factors of arsenic mobilization in aquifer remain uncharacterized. This study investigated microbial communities between sediments from the blackfoot disease (BFD) and non-BFD endemic area. The results showed that after 2 months incubation, the microbial community showed significantly different in the BFD and non-BFD endemic area. In addition, the effects of fertilizers and microorganisms on arsenic mobilization in the sediments of the BFD endemic area were examined. Microcosm experiments were performed amending with inorganic nitrogenous or phosphorus fertilizers for 2 and 4 months under aerobic and anaerobic conditions. The results showed that microcosms amended with 25 and 100 mg/L phosphorus fertilizers (dipotassium phosphate) showed significant increases in arsenic concentrations in aqueous phases, with an arsenite (As(III)) concentration increase from 66.4 ± 4.6 μg/L (original non-sterilized sediments) to 81.6 ± 8.6 (25 mg/L dipotassium phosphate, non-sterilized sediments) and 110.5 ± 6.0 μg/L (100 mg/L dipotassium phosphate, non-sterilized sediments) under anaerobic condition. However, the addition of nitrogenous fertilizers (ammonium sulfate) showed little effect on the arsenic mobility. Moreover, concentrations of iron, manganese, potassium, sodium, calcium, and magnesium were increased in the aqueous amended with dipotassium phosphate, suggesting that multiple metal elements may take part in the arsenic release process. Furthermore, microbial analysis indicated that the dominant microbial phylum was shifted from α-Proteobacteria to β- and γ-Proteobacteria when the As(III) was increased and phosphate was added in the aquifer. Our results provide evidence that both phosphorus fertilizers and microorganisms can mediate the release of sedimentary arsenic to groundwater in the BFD region, suggesting that agricultural activity such as usage of fertilizers should be taken into consideration.

並列關鍵字

arsenic ； mobilization ； blackfoot disease ； fertilizers ； groundwater ； microbial community

參考文獻

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影響台灣烏腳病疫區含砷地下水砷移動因素之探討

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