土壤性質會影響砷的有效性，且不同水稻品種吸收砷的能力會有差異。水稻根部鐵膜對影響水稻吸收砷的相關研究越來越多，但土壤性質、水稻品種與鐵膜三者的關係仍不清楚。因此本研究目的為將四種品種水稻種植於人為添加砷之三種土壤及一種現地砷污染土壤中，研究土壤性質與水稻品種對鐵膜生成與水稻幼苗吸收砷之影響。將四種水稻品種 (梗稻:高雄145號、台中192號; 秈稻:中秈育837號、台中在來一號) 種植於三種土壤性質差異性大的土壤。在此三種土壤中添加0、120和200 mg kg-1之As(V)；另取三種不同砷濃度之關渡平原現地砷污染土壤，以土水比1:1進行50天浸水孵育與盆栽試驗。
結果顯示由於平鎮系土壤為風化程度高的土壤，土壤pH低且游離態鐵鋁氧化物含量高，對砷與磷的吸附能力強，因此浸水孵育後土壤溶液中砷和磷的有效性很低。將軍系與太康系土壤pH值高、黏粒含量低、游離鐵鋁氧化物含量低，導致浸水孵育期間溶液中砷濃度可高達3 mg L-1，且砷的劃分結果顯示土壤的砷主要為非特異性鍵結砷，因此砷有效性高，水稻易吸收累積高濃度的砷。具有豐富鐵氧化物與有機質的關渡土壤，在浸水之後土壤溶液中鐵還原導致砷溶出增加。
在平鎮、將軍、太康系土壤中水稻生成的鐵膜量皆很少，富含鐵氧化物與有機質的關渡土壤生成的鐵膜量較多；水稻品種間鐵膜生成量有明顯差異，比較鐵膜的生成量發現梗稻多於秈稻，其中以台中192號 (梗稻) 較多，中秈育837號 (秈稻) 較少；土壤性質對鐵膜生成的影響較水稻品種大。研究結果顯示，鐵膜能阻隔土壤溶液中大部分的砷，形成砷進入植體之屏障，但是，當土壤溶液中砷過量時，如：將軍系土壤，即使鐵膜吸持的砷量多，仍無法完全阻隔砷進入植體。
水稻植體分析結果顯示不同品種對水稻吸收砷的影響有所差異，比較砷吸收量發現秈稻多於梗稻，當土壤溶液中含有高濃度的砷，秈稻品種台中在來一號地上部吸收的砷量多於其他水稻品種；台中192號相較於其他品種有較低的砷吸收量。因此，若於高濃度砷污染地區種植水稻，建議種植梗稻品種台中192號。The As availability can be influenced by soil properties. Futhermore, effects of As uptake by rice is dependent on rice genotypes. In recent years, the effects of formation of iron plaque on As uptake by rice have been studied. But the interactions among of soil properties, rice genotypes, and iron plaque are not clear. In this study, four different rice genotypes (Joponica: KS145 and TC192; Indica: TCSY837 and TCN1) grown in three As-contaminated Guandu soils containing different levels of As and three soils spiked with various levels of As(V) were investigated. The objective is to clarify the effects of soil properties and genotytes of paddy rice on iron plaque formation and As uptake by rice seedlings.
The soils were incubated at a water-soil ratio of 1:1 for 50 days. The Fe and As concentrations of soil solutions were determined. The results showed that soils with low pH values and high contents of free iron and aluminum oxides had high affinity for As and P, resulting in low the As and P availability during incubation period. The soils which have high pH, low clay and iron and aluminum oxides content (i.e. Chengchung and Taikang soils) were found to have low affinity for As and thus resulting in high concentration of As in soil solutions during the flooding incubation period. The results of sequential extraction procedure (SEP) also showed that the major fraction of As in Chengchung and Taikang soils was the form of non-specifically sorbed As which is regard to be easily uptaken by rice seedlings. The Guandu soils had high contents of iron and aluminum oxides and organic matter, thus the As was released into the soil solutions due to Fe or Al oxides reduction and dissolution.
The effects of soil properties on iron plaque formation were more important than that of rice genotypes. The iron plaque formation was higher in Guandu soil than in the three As(V)-spiked soils. The main factors of controlling iron plaque formation were the contents of iron oxides and organic matter. Iron plaque formation capability of Japonica rice was much higher than that of Indica rice. The TC192 formed the highest amount of iron plaque in the four rice genotypes, and TCSY837 formed the least. Iron plaque formed on rice roots seqestrated As and reduced As content in rice seedlings. However, it was incapable of blocking off As uptake by rice plants at high As concentrations in soil solution, particularly in alkaline soils.
The concentration of As in Japonica rice was lower than in Indican rice. TCN1 accumulated the highest concentration of As in the four rice genotypes. Generally, TC192 of Japonica rice had low As uptake in rice plant and hence could be grown on As contaminated soils in order to reduce the risk of As entering the food chain
