土壤六價鉻快篩與還原技術

本研究之目的為探索適合快速篩測土壤中所含Cr(Ⅵ)濃度之方法，使得現場調查能較為簡便快速。本研究先選用六種土壤(屏科大淺層、屏科大深層、桃園、演藝廳、吊雞林及赤山巖)，與不同濃度Cr(Ⅵ)溶液混合配製受污染土壤，以鹼性消化法及快篩法分別進行Cr(Ⅵ)濃度檢測，試比較並建立關係。次為瞭解使土壤中六價鉻轉變為三價鉻的條件，以建構易操作之還原技術，試驗中使用亞鐵Fe(Ⅱ)作為還原劑與受污染土壤反應，並輔以不同參數進行模擬。在製備均質污染土的過程中，六價鉻會與供試土壤原有之還原物質產生作用，因此以鹼性消化法測得土壤中實際六價鉻濃度均低於其理論配製濃度。前人報告指出，土壤所含之天然有機質即具有還原六價鉻的能力(Nakayasu et al.,1999 ; Bartlett and Kimble,1976)，初步結果也顯示回收率與土壤有機質含量相關，高有機質含量之組別回收率較差，反之則有較良好的回收率。快篩法測得之六價鉻濃度與鹼性消化法具有同樣趨勢，測得濃度同樣與理論配製濃度因土壤而異，然而可能由於萃取法差異所致，回收率優劣排序與鹼性消化不盡相同。前人研究顯示pH值越高六價鉻之吸附率則越低(Heike ,2005)，依結果推測主要可能受pH值影響。在還原試驗中，使用亞鐵溶液可有效還原本研究配製之1,000mg/kg六價鉻污染土壤。高濃度之亞鐵溶液還原效果皆優於低濃度之亞鐵溶液，但本研究並未發現不同pH組別之還原效果有明顯的關係。

關鍵字

六價鉻；三價鉻；快速篩測；化學還原

並列摘要

The purpose of this study was to explore a method suitable for rapid screening of Cr (Ⅵ) concentrations in soil, making field investigations easier and faster. In this study, six kinds of soils were mixed with different concentrations of Cr (Ⅵ) solutions to prepare contaminated soils. Detect Cr (Ⅵ) concentration by alkaline digestion method and Quick test, try to compare and establish the relationship. In order to understand the conditions for transforming hexavalent chromium into trivalent chromium in the soil, in order to construct an easy-to-operate reduction technology. In the experiment, ferrous Fe (Ⅱ) was used as a reducing agent to react with the contaminated soil and supplemented with different parameters for simulation. In the process of preparing homogeneous contaminated soil, hexavalent chromium will interact with the original reducing substances of the tested soil. Therefore, the actual hexavalent chromium concentration in the soil measured by alkaline digestion method is lower than its theoretical preparation concentration. Previous reports have pointed out that the natural organic matter contained in the soil has the ability to reduce hexavalent chromium (Nakayasu et al., 1999; Bartlett and Kimble, 1976). Preliminary results also show that recovery is related to soil organic matter content. The recovery rate of the group with high organic matter content is worse, otherwise it has a better recovery rate. The hexavalent chromium concentration measured by the Quick test has the same trend as the alkaline digestion method. The measured theoretical concentration is different from the actual concentration in different soils. However, it may be due to the difference in extraction methods. The order of recovery is not the same as that of alkaline digestion. Previous studies have shown that the higher the pH value, the lower the adsorption rate of hexavalent chromium (Heike, 2005). According to the results, it is speculated that it may be mainly affected by pH. In the reduction test, the use of ferrous solution can effectively reduce the 1,000 mg / kg hexavalent chromium contaminated soil prepared in this study. The reduction effect of high concentration ferrous solution is better than low concentration ferrous solution. However, this study did not find a significant relationship between the reduction effects of different pH groups.