本研究藉由環境友善的地球化學調控手法，於受到重金屬鎘污染之稻作農業用地土壤中添加零價鐵與硫酸鹽，希望可以降低鎘對於稻作植體的生物有效性，並且達到降低鎘累積至食米濃度的目的。試驗結果顯示，在稻作栽種覆水期間的孔隙水中所含有之親硫重金屬濃度包含鎘、銅、鋅等皆有顯著的降低趨勢，並會隨鐵濃度添加量而降低，但硫酸鹽的添加並沒有依照預期的模式將重金屬轉化為金屬硫化物沉澱；在試驗最終所收成的糙米中所檢驗出的鎘的濃度時，鐵的添加確實可以使鎘累積至糙米中的濃度降低在食米標準以內，但硫酸鹽的添加卻仍然有鎘累積的現象產生，表示降低孔隙水中重金屬的濃度仍然無法降低糙米累積吸收鎘的量。土壤中的菌相組成豐富度除了低鐵組比控制組低之外，其餘組別均比控制組高，表示本試驗中所使用的地化調控手法對於環境為友善的；由低鐵組的菌相豐富度比控制組低的結果可知而土壤中菌相組成豐富度會受到金屬壓力的影響使菌相豐富度降低。最後，由土壤中菌群對於鎘的抗性基因czcA 表現量可知在本研究所使用的地球化學調控手法確實能降低重金屬鎘具生物有效性的潛勢；但czcA 的表現量多寡也會受到地化參數的影響。;In this study, zero-valent iron and sulfate were added to the agricultural land of rice contaminated with heavy metal cadmium by eco-friendly geochemical amendments. Expected that the bioavailability of cadmium to rice plants can be mitigated and the accumulation of cadmium could be reduced. The results show that the concentration of cadmium in porewater was significantly reduced with the addition of iron concentration, but the addition of sulfate did not convert to the sulfide in the soil system. Such decreases in the phytoavailability of metals to rice roots did not significantly lead to mitigating the accumulation of Cd in the harvested brown rice. The richness of bacterial communities in the soil was lower than that of the control group except for the addition of the low Fe group, and the other groups were higher than the control group. These results also showed that bacterial communities in the soil were affected by the metal pressure of cadmium, which reduced the bacterial richness. From the amount of cadmium resistance gene czcA in the soil, it is known that the geochemical regulation techniques used in this study can indeed reduce the bioavailability of heavy metal cadmium, but the amount of czcA expression will also be affected by the geochemical parameters. In summary, the geochemical amendments in this study are eco-friendly to the environment. The addition of the valent-iron amendment has a better effect to stabilize the cadmium in the soil, reduce the phytoavailability of cadmium.
