- 期刊
關渡平原水田土壤砷種類與水稻植體濃度關係探討
The Relationship between Arsenic Species in Paddy Soils and Arsenic Content of Rice Tissues at Guandu Plain
摘要
水稻值體砷含量多寡受灌溉水，土壤砷濃度與形式影響，然而水稻根部吸收土壤中砷的機轉尚無一致定諭。本研究係針對關渡平原機地水稻植體進行砷含量與其對應土壤砷濃度和土壤溶液砷種類(As(上標 Ⅲ)與As(上標 V)關係之探討。水稻植體與對應根部土壤分別利用分析儀器爲原子吸收光譜儀(AAS)外掛自動化連續流動式氫化物産生裝置(HFS-3)以及手持式X-光螢光分析儀(FPXRF)分析總砷：水稻根部土壤溶液則是使用感應耦合電漿質譜儀(ICP-MS)外掛Octopole collision/reaction system檢測。研究區域水稻植體根部、莖葉與稻穀的含砷量平均分別爲98.7、3.49與0.074 mg kg^(-1)（n=10，乾重），顯示砷含量會隨著稻根－莖葉－稻穀而呈現處減的現象。土壤樣品總砷濃度平均值爲135 mg kg^(-1)（25至272 mg kg^(-1)）：土壤溶液抽出液砷濃度（As(上標 Ⅲ)與As(上標 v)）的平均值爲30.1 μg L^(-1)（1.5至100.5 μg L^(-1)）。其中，第一與第二高值分別爲100.5與68.1 μg L^(-1)，其餘皆低於50 μg L^(-1)。初步調查得知水田在浸水條件下，砷在土壤溶液係以亞砷酸鹽(As(上標 Ⅲ))的形式存在爲主，平均約佔89%。土壤砷濃度與水稻根部砷含量的線性相關性高於與莖葉和稻穀砷含量的線性相關性：土壤溶液砷濃度（As(上標 Ⅲ)與As(上標 v)）與水稻植體砷含量的關係也與上述現象一致。未來工作將著眼於土壤砷含量偏高的農田，研究不同型態的砷在土壤系統與水稻根部之間的傳輸模式。
並列摘要
Although arsenic content of rice tissues apparently depended on the irrigated water arsenic quantity and the forms of arsenic in soil solution, the mechanism of adsorbed arsenic in rice root was obscurely unclear. The objective of the present study is to measure arsenic content in different parts of rice, paddy soils and soil solution, and eventually try to explain the relationship between arsenic species in paddy soils and arsenic content of rice tissues at Gaudan Plain, including its relationship to the soil. Soil samples and rice tissues were collected and analyzed separately using field portable X-ray fluoresce (FPXRF) and Atomic Absorption Spectrophotometer (AAS) with automatic hydride generator (HFS-3). The arsenic speciation of soil solution in the rhizosphere was determined by the Inductively-Coupled plasma Mass Spectrometer (ICP-MS) with the Octopole collision/reaction system. The mean arsenic contents in root, straw and grain were measured at 98.7, 3.49 and 0.074 mg kg^(-1) (n=10, dry weight), respectively and the arsenic level in rice from toot to grain was shown to have a decreasing trend. The mean arsenic levels were 135 mg kg^(-1) (25-272 mg kg^(-1)) in soil samples via FPXRF and 30.1 μg L^(-1) (1.5-100.5 μg L^(-1)) in soil solution (covering only arsenite and arsenate) analyzed by ICP-MS. In soil solution samples, its first and second high value of arsenic content were separately 100.5 and 68.1 μg L^(-1)) and the others were below 50 μg L^(-1). The results of this study initially indicated that the arsenite (As(superscript Ⅲ) predominates (about 89%) under anaerobic conditions of paddy soils. In comparison, regression of soil arsenic levels with rice grains and straws were less significant compared to that with rice roots and so did soil solution arsenic content. To figure out the fact regarding arsenic poisoning in rice tissues through these soil-plant pathways in the extremely polluted soil by arsenic, intensive investigation on a complete transformation mechanism is needed, which is our future interest.