氮肥及重金屬對水稻幼苗生長及反射光譜之影響

隨著人類活動日益頻繁，土壤中重金屬快速累積，加上重金屬具有不可分解性，使土壤重金屬污染日趨嚴重。由於影響土壤中重金屬有效性之因子及重金屬污染來源眾多，並非土壤重金屬濃度未達管制標準該農地所生產之農作物重金屬含量即符合標準，因此本研究希望能建立即時且非破壞性之監測方式以預估土壤有效性重金屬污染物濃度與植體累積重金屬含量。本研究以水稻 (Oryza sativa L.)幼苗(台南11號TN11及台稉14號TK14)為材料，以50、100及200 ppm之氮素濃度分別與鎳 (0、10、20及40 μM)、鎘 (0、50、100及200 μM)、銅 (0、10、20及40 μM)、鋅 (0、1000、2000及4000 μM)、鉻 (0、100、200及500 μM)及鉛 (0、100、200及500 μM)六種重金屬進行複因子水耕栽培試驗，模擬在田間不同濃度氮肥管理下，土壤溶液中有效性重金屬對水稻幼苗造成之影響，並測定葉片反射光譜，以反射率計算植生指數(vegetation index)，計算植生指數與重金屬處理濃度及植生指數與地上部重金屬含量之預測模型。結果顯示受重金屬逆境之植株普遍地上部生長受抑制且在葉片反射光譜上，受重金屬逆境植株在紅光及綠光反射率普遍增加，而在較高濃度氮處理下反射率較氮濃度50 ppm處理組低。此外，675 nm以上之波段中，各重金屬處理組合之反射光譜一次微分波峰在高氮濃度下普遍往長波長方向位移，產生紅光臨界紅移 (red shift of red edge)，而受重金屬逆境植株之波峰則普遍往短波長方向位移，產生紅光臨界之藍移 (blue shift of red edge)，可做為植株是否受逆境之參考。以常用波段或敏感波段計算之植生指數分別與植體重金屬濃度或重金屬處理濃度間建構線性及多項式模型，其中又以多項式模型較佳且具顯著相關性。因此利用反射光譜計算植生指數，非破壞性預估土壤有效性重金屬污染物濃度與植體累積重金屬含量，可能為有效可行之方法。

關鍵字

重金屬；反射光譜；水稻幼苗；氮素；植生指數；遙感探測

並列摘要

Heavy metal Contamination of soils has been a widespread occurrence since anthropogenic activities began. Because heavy metals are non-degradable, their concentrations in soils significantly go beyond regulatory standards. Due to many factors affecting heavy metal availability in the soil, and many sources of heavy metal pollution, heavy metal content in crop may be excessive even though heavy metal concentration in soils meets the regulatory standard. Thus, we would like to create indices using reflectance spectra to perform non-destructive estimation of bioavailable heavy metal concentrations in soils and accumulation concentration in shoots. In this research, hydroponic rice (Oryza sativa L. cv. Tainan 11 and Taiken 14) seedlings were treated with treatment combinations of three nitrogen concentrations (50,100, and 200 ppm) and six heavy metal concentrations (Ni: 0, 10, 20 and 40 μM; Cd: 0, 50, 100 and 200 μM; Cu: 0, 10, 20 and 40 μM; Zn: 0, 1000, 2000 and 4000 μM; Cr: 0, 100, 200 and 500 μM; Pb: 0, 100, 200 and 500 μM) to simulate the effects of heavy metals in soil solution on rice seedlings under different nitrogen management in the field. The reflectance spectra of leaves were recorded and used to calculate vegetation indices to observe the relation between vegetation index and the heavy metal treatment concentration or the relation between vegetation index and heavy metal concentration in shoots. The result indicated that heavy metal stress inhibited shoot length of rice seedlings. In high heavy metal concentration, the reflectivity in green light and red light increased and blue shift of red edge happened at the same time. In addition, the reflectivity in green light and red light decreased in high nitrogen concentration, and red shift of red edge happened at the same time. The linear model and quadratic model were constructed from the relation between heavy metal concentration of shoots and vegetation index or the relation between heavy metal treatment concentration and vegetation index. The result showed that quadratic model has more significant correlation in both sets of variables. Therefore, it appears possible to create indices using reflectance spectra for non-destructive estimation of bioavailable heavy metal concentration in soils and accumulation concentration in shoots.

並列關鍵字

heavy metal ； reflectance spectra ； rice seedlings ； nitrogen ； vegetation index ； remote sensing

參考文獻

郭鴻裕、劉滄棽、江志峰。2010。作物 (水稻) 吸收土壤重金屬鎘機制與農產品安全之影響。技術服務，21(3)，頁12-14。

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氮肥及重金屬對水稻幼苗生長及反射光譜之影響

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