引用含砷灌溉水後對砷在水田土壤及水稻之累積

The accumulation of arsenic in paddy soils and rice plants with arsenic-containing irrigation water

柯雅婷(Ya-Ting Ko)

指導教授 ： 許正一

國立屏東科技大學/工學院/環境工程與科學系所/碩士(2014年)

https://doi.org/10.6346/NPUST.2014.00165

摘要

臺灣西南沿海地區由於地質因素造成地下水含砷物質，引用含砷地下水作為灌溉用水，砷可能在水田土壤及稻米累積，對糧食安全性產生影響。本研究針對長期使用含砷地下水作為灌溉用水之農地，探討高灌水量及低灌水量對土壤累積砷及水稻吸收砷能力的影響。試驗田位於臺南市將軍區兩個相鄰之農田土壤，使用相同一地下水源。於102年2月17日種植臺農84號水稻，102年6月18日採收。在水稻分化期及成熟期採集水樣、土壤及植體，分析地下水、土壤及植體的砷濃度。
高灌水區田間用水量為1580 mm，低灌水區為1270 mm。102年1月及4-6月地下水中砷濃度分別為3.78、5.78、8.42及10.0 μg/L。由於地下水之EC值高於灌溉水質標準2倍，導致部分土層pH值高達8.0以上。本研究區土壤中砷含量與其他文獻相比，屬偏低的範圍。砂質壤土特性使得水稻在成熟期時，高灌水區土壤中砷含量1.03-2.58 mg/kg，而低灌水區砷含量1.20-3.54 mg/kg，因此不同灌水量對於土壤中砷含量無明顯影響，且與入水口距離無明顯的相關性。分析四種不同深度土壤(0-15、15-30、30-45及45-60 cm)中砷含量，發現表土砂粒含量高，導致砷主要累積在30 - 45 cm的壓實層中。高灌水區鐵膜中砷含量115-933 mg/kg，低灌水區52.3-385 mg/kg，顯示砷主要累積在根部鐵膜，且灌水量多寡會影響鐵膜中砷含量，但在根部及地上部(莖葉、稻殼及稻米)無明顯差異。砷在水稻各部位之累積量高低依序為鐵膜 > 根部 > 莖葉 > 稻殼 > 穀粒。

關鍵字

砷 ； 地下水 ； 水田土壤 ； 水稻 ； 鐵膜

並列摘要

The accumulation of arsenic in soils and food crops due to the use of arsenic containing groundwater for irrigation has created worldwide concern. The aims of this study are to compare the accumulation of arsenic in paddy soils by different amounts of irrigation, to understand the vertical and horizontal distribution of As content in the soils, and to measure As content in different organs of rice (Oryza sativa L.). Two plots (high irrigation, H; low irrigation, L) in the study area were located in Jiangjun District, Tainan City, Taiwan, used the same groundwater source. Rice was cultivated in the paddy fields in February 17, 2013. After 122 days, it was harvested. In the jointing stage (April and May, 2013) and the maturing stage of rice growth, we collected the groundwater, soils and rice samples and analyzed arsenic concentration by HG-AA.
The concentrations of As in groundwater in January, April, May, and June, 2013 were 3.78, 5.78, 8.42 and 10 μg/L respectively. The pH values in some soil samples were higher than 8.0 corresponding to their high ECs . The rhizosphere soils showed total As content in the range of 1.03-3.54 mg/kg. In the maturing stage, total As concentrations in the H and L fields were 1.03-2.58 and 1.02-3.54 mg/kg, showing no As difference of soil between different amounts of irrigation. As was concentrated in the plow layers of the paddy soils. Ferrous iron, which is mobilized in the bulk soil solution, was oxidized to ferric iron and precipitated as iron oxides/hydroxides on the root surface, the so called iron plaque. The accumulation of As in iron plaque in H field and L field were 114.8-933.0 and 52.29-384.8 mg/kg, this difference was not correlated with As content in the roots. The arsenic content in different parts of rice are found in the order of iron plaque > root > straw > husk > grain.

並列關鍵字

arsenic ； groundwater ； paddy soil ； rice ； iron plaque

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