結合電動力法與植生復育法整治重金屬污染農地之可行性探討

Study on the Remediation Feasibility of Combining Electrokinetics and Phytoremediation for Heavy Metal-Contaminated Agricultural Land

沈善鎰(Shan-Yi Shen) ； 章日行(Jih-Hsing Chang)

《土壤及地下水污染整治》 4卷2期 (2017/04) Pp. 85-95

https://doi.org/10.6499/JSGR.2017.0402.001

摘要

重金屬進入土壤中會長期殘留於土壤，當土壤中含高濃度重金屬時，會使得植物和微生物的生長受到抑制，土壤肥力無法有效發揮作用，導致作物受到毒害使產量減少或死亡。以電動力法整治受重金屬污染農地已逐步發展，發展初期大多以電動力法搭配pH緩衝劑與螯合劑加速移除土壤的重金屬，雖然經過一段時間的整治的確能降低土壤重金濃度符合管制標準，被整治農地也能維持相當的肥力，但電動力法整治重金屬污染農地的成本仍大幅超過目前台灣慣用的排客土法。因此，發展電動力法於重金屬污染農地的整治，勢必面臨降低整治成本及處理效率的雙重挑戰。本研究結合電動力法與植生復育法整治重金屬污染農地，以南投市某污染場址為整治對象，整治面積為1.0平方公尺，以含有0.01 M Na_2CO_3及EDTA-2Na的配製溶液為電解液，於0.8 V/cm電壓下進行電動力試驗一段時間後，接著栽種玉米進行植生復育，再以電動力法整治。試驗結果顯示，經過32天電動力法操作下，鉛濃度從平均5,672 mg/kg降至約4,309 mg/kg，平均去除效率約達到25%。後經玉米整治復育60天，農地鉛去除效率約7%，當再以電動力法操作7天，土壤鉛濃度快速下降至鉛管制標準值約2,000 mg/kg。本整治方法的成本即可接近排客土法且同時達到管制標準。

關鍵字

重金屬 ； 污染土壤 ； 電動力法 ； 植生復育

並列摘要

Heavy metals will exist in soils for a long period of time, and at a certain concentration the growth of plants and bacteria will be dramatically inhibited. The crops grown in such land will be toxic under such conditions, which results in a lower or even no harvest. The electrokinetics (EK) technique has been developed to remediate heavy-metal contaminated soils. Nowadays, most EK techniques use pH buffer solution and chelating agents to facilitate the removal of heavy metals. Although the concentration of heavy metals can thus be reduced to meet the soil control standards and the fertility of the treated soils could be maintained after EK remediation, the cost of this approach is far more than that of soil dumping in Taiwan. In this study, an integrated technique of EK and phytoremediation was thus applied to lead-contaminated agricultural land located in Nantou City, Taiwan. The treated area is 1.0 m^2, and the EK operation solution contains 0.01 M Na_2CO_3 and EDTA-2Na. After a certain period of time under EK treatment at 0.8 V/cm voltage gradient, the land was phytoremediated by corn planting, and the EK process was then applied again. The results indicate that the lead concentration of soils decreased from 5,672 mg/kg to 4,309 mg/kg after a 32-day EK treatment. The lead removal efficiency was thus around 25%. Moreover, about a further 7% of lead can be removed after 60-day corn phytoremediation. The lead concentration of the soils then fell to around 2,000 mg/kg after a 7-day EK treatment. This integration technique can achieve the goals of low cost and high removal.

並列關鍵字

heavy metal ； contaminated soil ； electrokinetics ； phytoremediation