農田土壤中鉛移動性指數的探討

Exploring the mobility indicator of lead in arable soils

許晃綜(Huang-tsung Hsu)

指導教授 ： 余伍洲

國立屏東科技大學/工學院/環境工程與科學系所/碩士(2016年)

摘要

土壤中重金屬之理化性質影響它們之溶解度，而溶解度直接影響它們的移動性，因此，測定污染土壤中重金屬含量總量將不足以評估其對環境之影響，了解土壤中重金屬污染物在土壤中移動模式研究實為一環境重要之課題。本研究目的在以王水法測定全量後，再以0.1N HCl萃取法、0.005M DTPA萃取法及0.05M EDTA萃取法分別測定鉛的選擇性萃取濃度，以求取分佈係數（Coefficient of distribution, Kd），即Kd值乃選擇性萃取法與王水法濃度之比值。Kd值為鉛在土壤中移動性之重要指標，藉由分析土壤中理化性質與Kd值之相關性，探討鉛在不同理化性質土壤中的移動性對環境生物之危害，期能掌握土壤污染危害與有助於整治復育評估。研究結果顯示，三區鉛平均濃度依序為彰化縣 > 桃園市 > 台南市，在128組土壤濃度皆遠低於農地土壤重金屬之監測標準及管制標準，故本研究之農地重金屬鉛濃度應均可作為背景重金屬濃度之參考值。三種萃取法於三地區各土系之萃取效率為0.05 M EDTA萃取法 > 0.1 N HCl萃取法 > 0.005 M DTPA萃取法，0.05 M EDTA萃取法萃取效率最佳。當pH偏酸時，Kd值有下降之趨勢，鉛的移動性也相對減少；反之pH偏鹼時，Kd值有增加之趨勢，鉛的移動性相對增加，有機碳含量（OC）越高Kd值有增加之趨勢，鉛的移動性增加；反之有機碳含量（OC）越低Kd值有下降之趨勢，鉛的移動性相對減少。土壤黏粒越高時，鉛的濃度有增加之趨勢，選擇性萃取之鉛Kd值亦相對增加，鉛移動性增加，反之，土壤黏粒越低時，鉛的濃度有下降之趨勢，選擇性萃取之鉛Kd值亦相對減少，鉛移動性減少。選擇性萃取法萃取之鉛濃度及Kd值可作為鉛移動性指數參考值。

關鍵字

鉛 ； 王水消化法 ； 0.1 N鹽酸萃取法 ； 鉛移動性

並列摘要

The physicochemical properties of heavy metals in the soil influence their solubility which generates direct impact on their mobility. Thus, it is insufficient to evaluate the impact of heavy metals on the environment only based on their total amount in the soil. In this context, researches on the mobile mode of heavy metal pollutants in the soil become an important environmental topic. This research aims to calculate the coefficient of distribution (Kd value) by measuring the total amount of heavy metals in the soil with Aqua Regia Method followed by respective measurement of the selective extraction concentration of lead through 0.1N HCl Extraction, 0.005M DTPA Extraction and 0.05M EDTA Extraction. The Kd value represents the ratio of the concentration by selective extraction to the concentration by Aqua Regia Method which serves as a key indicator of lead mobility in the soil. This research explores the environmental and biological hazards of lead mobility in the soil with different physicochemical properties through correlation analysis of the physicochemical properties of soil and Kd value in order to learn about the soil pollution hazards and facilitate the control, restoration as well as evaluation. The research findings show that the average concentration of lead in the three areas in a descending order is Changhua County, Taoyuan City, Tainan City. The soil concentration in the total 128 groups of experiments is much lower than the monitoring and control standards for heavy metals in the agriculture field soil which certifies that the lead concentration in the agriculture field soil researched can be used as reference value to the heavy metal concentration in the soil. The extraction efficiency of the three extraction methods in the three areas in a descending order is 0.05 M EDTA Extraction, 0.1 N HCl Extraction, 0.005 M DTPA Extraction respectively, with 0.05 M EDTA Extraction being the most efficient extraction. There is a decrease in Kd value with an acid pH where lead mobility also relatively decrease and an increase in Kd value with an alkali pH where lead mobility also relatively increase. In addition, the more organic carbon content (OC), the higher the Kd value and lead mobility, and vice versa. Meanwhile, the more soil clay, the higher the lead concentration and Kd value through selective extraction, and vice versa. The lead concentration and Kd value through selective extraction can serve as reference value to lead mobility index. Besides, the particle size, pH and organic carbon content of the soil can also be used as reference to determine whether there are exogenous contaminants.

並列關鍵字

lead ； Aqua Regia Method ； 0.1 N HCl Extraction ； mobility index

參考文獻

張祐銓，2014，蛇紋岩土壤之鉻、鎳萃取濃度和土壤性質之探討，碩士論文，國立屏東科技大學，環境工程與科學系研究所，屏東。

曾元新，2013，王水消化法與X-射線螢光光譜儀快速篩選法測定土壤鉻、鎳之比較，碩士論文，國立屏東科技大學，環境工程與科學系研究所，屏東。

行政院環境保護署，2010，土壤及地下水污染整治法。

行政院環境保護署環境檢驗所，2003，土壤中重金屬檢測方法－王水消化法。

行政院環境保護署，2000，台灣地區土壤重金屬含量等級區分表工作內容說明。