以不同消化方法探討本省南部及東部農業區與都會區數種土壤中重金屬含量及其存在形態的差異

Study on Soil Heavy Metal Digestions and Formal Distribution in Farmland and Metropolitan Soils in Southern and Eastern Taiwan

薩支高(J. G. Sah)

《土壤與環境》 1卷1期 (1998/03) Pp. 31-41

https://doi.org/10.30058/SE.199803.0004

摘要

土壤重金屬消化方法的代表性一直是專家討論的方向，多年來本省土壤調查都以0.1M鹽酸萃取法為主，近來都會區與工業區土壤品質監測計畫則以王水消化法為標準，另外常被討論的尚有利用硫酸－硝酸－氫氟酸－過氯酸的Jackson消化法及氫氟酸－過氯酸消化法。本研究以本省南部的高雄都會區、嘉南農業區及東部農業區部分具代表性土壤為樣品，並與桃園鎘、鉛污染土壤及高雄地區廢五金灰燼堆置土壤二處已被重金屬污染的土壤樣品做比較，來探討上述四種消化／萃取方法間的差異性。同時並利用連續性化學萃取程序進行該等土壤中重金屬五種形態分佈的分析，期以建立爾後土壤污染預防與復育之基礎。研究結果顯示以四種萃取或消化法所測得重金屬濃度在不同地區土壤及不同重金屬元素二項變數間均有差異，利用0.1M鹽酸萃取及王水消化法所測得重金屬濃度間有一定的比例關係。利用氫氟酸－過氯酸消化法測得土壤重金屬濃度與王水消化法最接近。連續性化學萃取結果發現所有供試土壤中鉛的回收率最佳，除銅之外其他金屬的平均回收率差異亦均在100±10%之內。不同地區土壤中六種重金屬的五種形態分佈多不相同，鋅在都會區及已被污染現地土壤中是以非殘餘態為主，不同於嘉南及東部農業區土壤。殘餘態鎘在所有土壤中均未被發現，都會區及被污染土壤中鎘僅以可交換態、碳酸鹽態及有機態存在，被污染土壤樣品可交換態鎘的量及比例均高。鉛、銅及鎳在已被污染土壤中的分佈亦與其他土壤的不同。土壤中重金屬形態分佈及全量濃度的差異可以用來說明該土壤過去及現在使用方式的異同，及判斷潛在危害的嚴重性。

關鍵字

土壤重金屬 ； 消化方法 ； 連續性化學萃取程序

並列摘要

Soil and environmental scientists are always interested in the representatives of soil digestions. In this study, three digestions and one extraction, i.e. aqua regia, Jackson's, HF-HClO4 digestions and 0.1M HCl extraction, are used to examine heavy metals in soils from Taiwan's farmland and metropolitan areas. Soils from two well-known heavy metal contaminated areas in Taiwan are also compared. Sequential extracting procedure (SEP) was also applied to investigate the formal distribution of six heavy metals. According to those results, differences arise between methods owing to the metals and locations' variation. There are definite ratios between aqua regia total and 0.1M HCl extractable concentration. For most of the metals examined herein, the total concentration from aqua regia digestion somewhat resembles the one from HF-HClO4 digestion. Not including Cu, the SEP recovery rates of five other metals in the soils are nearly 100%. Soils from both metropolitan area and contaminated sites have high Zn ratios in non-residual forms, which are not the same as the soils from farmlands. None of the residual Cd can be found in soil samples. In soils from metropolitan areas and contaminated sites, Cd exists primarily in exchangeable, carbonate and organic forms. The existing ratios and contents of exchangeable Cd in contaminated soils are both highs. The formal distributions of Pb, Cu and Ni in contaminated soils differ from those in soils for the other three normal locations. Both soil heavy metals' total contents as well as formal distribution are critical factors for identifying the pollution impacts and predicting the potential risk.

並列關鍵字

digestion ； sequential extraction procedure ； soil heavy metals