請用此 Handle URI 來引用此文件:
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/74239
標題: | 釋氧劑施用與其施用時機對砷污染水田土壤中水稻砷累積之影響 Effects of oxygen releasing compound application and its application timing on arsenic accumulation in paddy rice grown in arsenic-elevated paddy soils |
作者: | Zhi-Xun Lai 賴致勳 |
指導教授: | 李達源(Dar-Yuan Lee) |
關鍵字: | 砷,水稻,釋氧劑,過氧化鈣,鐵(氫)氧化物, arsenic,paddy rice,oxygen releasing compound,calcium peroxide,iron (oxy)hydroxide, |
出版年 : | 2019 |
學位: | 碩士 |
摘要: | 水稻為亞洲區域人民主要糧食作物,但由於其生長特性須栽植於水田環境方有穩定且較高產量,如此一來當地土壤若含有較高砷濃度可能導致水稻穀粒累積過量砷,進而提高人體健康風險。國際水稻研究機構 (IRRI) 曾為解決種植水稻耗水問題,建議採取乾溼交替法 (AWD),該法亦被證實能有效降低水稻穀粒砷累積,但進行該操作未必符合水稻生長期中需要大量水分的時機,加上氣候變遷之故,要兼顧穀粒產量及降低穀粒砷累積量存在相當程度的技術門檻。因此本研究立論於維持水稻土壤氧化環境,能降低砷釋出的原理,嘗試施用釋氧劑於兩處因引用含砷灌溉水源造成砷污染之水田土壤,分別是嘉南平原菜公厝系土壤及關渡平原關渡系土壤,再分別於兩地各採集高砷及低砷土壤進行盆栽試驗,探討施用釋氧劑對水稻糙米砷累積量的影響。有鑑於先前研究結果顯示釋氧劑施用時機與劑量相當重要,本試驗選定單一釋氧劑劑量 (60 g kg-1 soil) 施用於兩個被認為是水稻穀粒砷累積的主要時期,分別是水稻孕穗期及開花後兩週。水稻種植期間監測Eh、pH、土壤孔隙水鐵與砷(物種)濃度,穀粒成熟後採收植體,針對水稻根部鐵膜與吸附其上的砷含量、植體砷濃度與穀粒砷(物種)濃度進行分析。結果顯示於該兩時期施用釋氧劑能降低土壤孔隙水的砷與鐵濃度,但關渡低砷與菜公厝高砷土壤在孕穗期施用釋氧劑後,孔隙水砷濃度有上升之現象,推測為本體土壤pH上升造成砷脫附所致。水稻根部鐵膜生成量並未因為施用釋氧劑而增加,應為土壤孔隙水鐵濃度因為鐵(氫)氧化物還原溶解的程度趨緩而下降,以至於較少鐵元素移動至根表形成鐵膜之故。關渡系土壤的糙米砷(物種)濃度在水稻孕穗期及開花後兩週施用釋氧劑後皆有顯著下降,但菜公厝系土壤處理則無此趨勢,其中關渡系土壤與菜公厝系土壤差異在於有較多的黏粒、有機質及游離型鐵(氫)氧化物,推論這些性質與施用劑量及時機應同為釋氧劑施用成效的影響因子。 Inorganic arsenic (As) is a highly toxic and carcinogenic metalloid which widely distributed in the environment. There is a fact that the serious health risk to human through the intake of rice grain grown in As-contaminated paddy soil, due to the high mobility and bioavailability of As in flooding conditions. In this study, we attempted to use oxygen releasing compound (ORC, calcium peroxide) to supply the oxygen in flooded soil, and further avoid iron (Fe) oxides reductive dissolution, arsenate reduction and dissolution. Therefore, the objectives of this study were to investigate the effects of ORC application and its application timing on As accumulation in rice grains. Two geogenic As-elevated soils including Gd [high organic carbon (OC) and iron (Fe) oxides contents] and Ms (relatively low OC and Fe oxides contents) were collected, and both soils have two distinct levels of As expressed as H (high) and L (low). Two ORC application timing [booting stage (B) and the two weeks after flowering stage (F)] were adopted in this study, and the dosage of ORC applications is 60g/kg soil. The results showed that the concentrations of As and Fe in pore water were obviously lessened after ORC application inferring that ORC might alleviate iron (oxy)hydroxide reductive dissolution through keeping soil environment oxygenated. The above phenomenon could be validated by observation of no significantly more iron plaque formation in ORC application treatments. In addition, results revealed that some ORC treatments contributed to increment of As concentration in pore water which might due to desorption of As in high pH range. The results unveiled that the concentrations in brown rice of ORC applications at booting stage and the two weeks after flowering stage were significantly lower than control treatments in Gd-H and Gd-L soils. However, it was found that there were no significant differences in As concentration in brown rice between ORC and control treatments in Ms soils, predicting it mainly caused by the low contents of clay fraction, iron (oxy)hydroxides and organic matter in these soils leading to fewer chances of the oxidized-As being adsorbed by de novo soil iron (oxy)hydroxides. Therefore, it is crucial that there is not any soil types suitable for As remediation by ORC application. It must be considered thoroughly before applying ORC as soil As contamination renovation strategy especially for low contents of clay fraction, iron (oxy)hydroxides and organic matter soils. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/74239 |
DOI: | 10.6342/NTU201902782 |
全文授權: | 有償授權 |
顯示於系所單位: | 農業化學系 |
文件中的檔案:
檔案 | 大小 | 格式 | |
---|---|---|---|
ntu-108-1.pdf 目前未授權公開取用 | 6.88 MB | Adobe PDF |
系統中的文件,除了特別指名其著作權條款之外,均受到著作權保護,並且保留所有的權利。