重金屬污染農地整治暨土壤肥力提升

Abstract

全世界每一年產生上百萬噸的有害廢棄物，而在過去由於不當廢棄物處理及其滲漏造成相當多的地區遭受重金屬、有機化合物及其他有害物質污染，並嚴重影響地下水、土壤及相關的生態。雖然，過去十幾年間已有實驗室試驗研究出多種有效解決這些問題的方法，但對於現地處理方法及相關資料仍相當缺乏。因此，本模場試驗乃以現地處理方式期能建立相關的現地資料，以提供未來大面積施行之參考。 電動力復育技術為一極具潛力土壤復育技術，尤其是對於低滲透性的土壤。本現場模場試驗主要為應用電動力復育技術現地移除坋質壤土農地之鎘、鉛及鉻污染物，並探討復育過程中鎘、鉛及鉻污染物之移除效率與土壤肥力之提昇效果。本試驗以檸檬酸及界面活性劑為處理液，藉由施加直流電，配合土壤化性的改善證實能同時改善坋質壤土農地之鎘、鉛及鉻污染及提昇自身土壤肥力。 本試驗於重金屬污染農地設置長3公尺，寬3公尺，高約0.5公尺的A、B二個處理槽，於A槽中以檸檬酸及界面活性劑為處理液，另B槽除以檸檬酸及界面活性劑為處理液另多添加食品級脫附劑於處理液中，經過92天的處理，結果指出B槽最終鎘、鉛及鉻之平均去除效率分別為76.59%、62.25%及50.40%；而A槽最終鎘、鉛及鉻之平均去除效率分別69.74%、58.02%及58.68%，顯見電動力復育技術對於重金屬去除有其良好的成效，另對於土壤中的有機質、全氮、Bray-1磷、交換性鉀及交換性鎂亦皆有相對程度之提昇，且在適當的操作環境下，電動力復育技術未來可作為全面土壤污染現地復育時整治工作之參考。

There are millions of tons of hazardous wastes generated every year in the world. Due to improper waste handling techniques causing hazardous waste release in the past, thousands of sites were contaminated by heavy metals, organics and other hazardous materials, which posed an enormous impact on quality of groundwater, soil, and the associated ecosystems. During past decades, several new, innovative solutions for efficient removal of contaminants from soil have been studied to help correct environmental pollution. Despite numerous promising laboratory experiments conducted, there are still not many techniques successfully implemented on in situ soil treatment. Therefore, results from this in situ pilot-scale testing can be used to establish useful data for field-scale implementation in the future. Electrokinetic treatment process is of a useful remedial technology, particularly on the soil with low permeability. The purposes of this pilot test is to implements electrokinetic technology to remove heavy metals Cd, Pb, and Cr from the silty loam in the rice field, to evaluate the removal efficiency of Cd, Pb, and Cr, and to promote soil fertility enhancement during treatment process. The test used citric acid-surfactant mixtures as treatment solution under an implied electrical field to enhance the removal of Cd, Pb, and Cr and fertility of the silty farm soil simultaneously. The test soil of this pilot test was stockpiled into two cells, Cell A and Cell B, and both with dimensions of 3 m long, 3 m wide, and 0.5 m high. This test used citric acid as the main reactive agent and a biodegradable liquid surfactant as the metal chelating agent in both Cell A and Cell B. Additional food grade surfactant was added in Cell B. The test was conducted over a period of 92 days. The test results revealed that electrokinectic process in Cell A gained an average removal efficiency of 76.59%, 62.25% and 50.40% for Cd, Pb and Cr, respectively. Electrokinectic process in Cell B gained an average removal efficiency of 69.74%, 58.02% and 58.68% for Cd, Pb and Cr, respectively. According to the test results, Eelectrokinetic process is proven as a successful technology to remove heavy metals from contaminated soil. In addition, the content of total nitrogen, Bray-1 phosphorus, and exchangeable potassium and magnesium, were relatively elevated after 92 days of treatment duration. It concludes that electrokinectic treatment technology is capable of mitigating soil contaminated with not only heavy metals but also organic compounds, and thus is a potential in situ treatment technology in the future.