在現地土壤與地下水污染整治技術中,化學氧化法是成本較低廉的方法之一,其中以Fenton-like法所使用之過氧化氫,由於具有強氧化力且處理後無毒性等特性,受到國內外學者的重視,但施以過氧化氫處理可能造成土壤中之重金屬溶出與氧化問題少有提及,本研究將以台灣花東地區鉻及鎳高背景值之蛇紋岩土壤製備柴油污染土壤,以過氧化氫溶液做為氧化劑,添加至供試土壤中,並以反應時間1 min、2 min、5 min、10 min、30 min,探討Fenton-like處理程序,是否會造成Cr(Ⅲ)氧化成Cr(Ⅵ)現象。研究結果發現蛇紋岩土壤中高濃度之鉻主要以三價鉻形式存在環境中,且經過氧化處理後仍然有高濃度之三價鉻存在土壤中,顯示蛇紋岩土壤中之鉻不容易因外在環境因素而完全溶出並釋放至環境中。其次,Fenton-like程序確實導致重金屬鐵、錳、鉻、鎳及鈷之溶出,當使用酸化Fenton-like處理時,其酸化程序明顯造成重金屬溶出增加。當研究模擬柴油污染土壤之氧化試驗時,柴油降解率最高可達86.6 %,顯示Fenton-like能有效解決土壤中柴油污染問題,而柴油污染土壤在氧化過程中,比非柴油污染土壤具有更高之重金屬溶出濃度,其中鉻(11.6 - 80.0 mg/kg)及鎳(2.80 - 512 mg/kg),故於高背景值重金屬土壤施以Fenton-like處理時,應審慎評估溶出重金屬的疑慮,避免二次污染情形。
In situ chemical oxidation (ISCO) is commonly used as a remediation method of contamination of petroleum hydrocarbons. Fenton-like is one of ISCO technology, and it used hydrogen peroxide in the soil and ground water. The Fenton-like method is cost-effective, but the major drawback is probably the release of heavy metals from the treated soils. In this study, several serpentinitic soils from the east of Taiwan with abundant background levels of Cr and Ni were spiked with diesel (10000 mg/kg). Moreover, the soils were treated by hydrogen peroxide, to investigate the dissolution of heavy metals and the oxidation of Cr(Ⅲ) to Cr(Ⅵ). The experimental results show that total Cr concentration was very high and is over the Soil Pollution Control Standard of Taiwan. After the treatment of Fenton reagent, the concentrations of Cr and Ni in the soil ranged from 11.6 to 80.0 mg/kg and from 2.80 to 512 mg/kg. The study indicated that application of Fenton-like and pre-acidification Fenton-like treatments caused Cr and Ni dissolution and generate Cr(VI). Dealing with the dissolution problem of Cr and Ni, the soil properties should be carefully concerned when using these chemical oxidation methods to remediate the diesel contaminated soils.