評估氯化鐵清洗法對含鎘水稻田土壤鎘移除、土壤性質及稻作生長之影響

Assessing the Effects of Soil Washing with Ferric Chloride on Cadmium Removal, Soil Properties and Rice Growth in Cd-containing Paddy Fields

許健輝(Chien-Hui Syu) ； 林毓雯(Yu-Wen Lin) ； 鄭佳怡(Chia-Yi Cheng) ； 何雅婷(Ya-Ting Ho) ； 陳柱中(Chu-Chung Chen) ； 劉滄棽(Tsang-Sen Liu) ； 郭鴻裕(Horng-Yuh Guo)

《台灣農業研究》 67卷4期 (2018/12) Pp. 365-376

https://doi.org/10.6156/JTAR.201812_67(4).0005

摘要

水稻田鎘汙染為嚴重的問題，因為攝食稻米為亞洲地區暴露鎘的主要途徑，所以降低水稻吸收土壤中的鎘對於減少人體暴露鎘的風險是相當重要的。土壤清洗法被認為是鎘移除效率高的土壤復育技術，然而目前較少研究評估現地氯化鐵清洗後的土壤鎘移除效率及作物生長狀況。因此，本研究目的為評估現地氯化鐵土壤清洗法對土壤鎘移除、土壤性質及稻作生長的影響。本研究試驗田位於台灣台中市后里地區，三塊含鎘水稻田（試驗田A、B、C）土壤鎘濃度分別為2.13、1.58及1.90 mg kg^(-1)，土壤清洗前後以網格方式採集土壤樣本，並分析其土壤鎘濃度及土壤性質。此外，在土壤清洗後之試驗田種植水稻，測定其生長指標及植株中的鎘濃度。試驗結果指出，氯化鐵清洗後三塊試驗田土壤平均鎘濃度分別降低36.8、46.3 及61.0%。相較於清洗前之土壤性質，清洗後土壤pH值、電導度（electrical conductivity; EC）及有效性磷有顯著變化，土壤總氮、總碳及陽離子交換容量（cation exchange capacity; CEC）則沒有顯著差異。稻作生長的結果指出，相較於對照組，氯化鐵清洗後水稻地上部高度、地上部生質量及稻穀產量未顯著下降，並且發現植體鎘濃度有下降的趨勢。總結本研究結果，現地氯化鐵清洗法可有效降低土壤的鎘濃度，並且對稻作的生長及稻穀產量影響不顯著。儘管此方法會些微影響土壤性質，但可透過石灰及肥料的供應回復地力。因此，本研究建議現地氯化鐵清洗法對於移除水稻田土壤鎘為可行的復育技術。

關鍵字

鎘 ； 土壤清洗 ； 氯化鐵 ； 水稻 ； 現地試驗

並列摘要

Cadmium (Cd) polluted in paddy field is the serious problem, and rice consumption is the major exposure pathway for Cd in many Asia area, thereby reducing Cd uptake by rice from soils is very important for lowering the exposure risk of Cd to human. Soil washing is recognized as a high efficient remedial technology for Cd removal. However, limited information is available for assessing the Cd removal and crop growth after on-site soil washing. Therefore, the objective of this study is to evaluate the effects of on-site soil washing with ferric chloride (FeCl_3) on the Cd removal, soil properties, and rice growth in paddy fields. Three Cd-containing paddy fields were selected for this study (Cd concentration in soil of fields A, B, and C are 2.13, 1.58, and 1.90 mg kg^(-1), respectively), which located in Houli Dist., Taichung City, Taiwan. The Cd concentrations and soil properties were measured before and after soil washing, and the soil samples were collected by grid sampling method. In addition, it also measured the growth indices and Cd concentrations in plant tissues of paddy rice grown in tested field after soil washing. The results indicated that the average Cd concentrations in soils of three tested fields were significant decreased after soil washing with FeCl_3, and the extents of decrease in Cd concentrations of tested fields were 36.8, 46.3, and 61.0%, respectively. It observed that the pH, electrical conductivity (EC) and available phosphorus (P) of soils were changed after soil washing, but there were no significant differences in total nitrogen (N), organic carbon (C), and cation exchange capacity (CEC) of soils between before and after soil washing. From the results of rice growth, compared with control treatment, it indicated that there was no significant decrease in shoot height, shoot biomass and grain yield of paddy rice grown in soils after soil washing. It also found that the concentration of Cd accumulated in rice plants were reduced. In conclusion, the results of this study indicated that the on-site soil washing with FeCl_3 could reduce the Cd concentration in soils effectively, and it has no significant effect on the plant growth and grain yield of paddy rice. In spite of the soil washing had slightly effect on the soil properties, it could be restored through lime and fertilizer supplied. Therefore, it suggests that the on-site soil washing with FeCl_3 may be a feasible remedial technology for Cd removal in Cd-contaminated paddy soils.

並列關鍵字

Cadmium ； Soil washing ； Ferric chloride ； Paddy rice ； On-site trial