The major problem in the remediation of contaminated sites and in the protection of ground-water quality is the lack of appropriate and reasonable standards for heavy metals in soils. There are no standards applicable to predict the potential for groundwater contamination by heavy metals in Taiwan. Lack these kind of soil standards may result in subjective Judgment regarding the remediation needed. The migration of heavy metals through the unsaturated zone to groundwater is controlled by sorption to the soil, a highly pH-dependent process, and the hydrological regime. SoiI sorption behavior is the criterion upon which to establish a standard based on a maximum permissible concentration in groundwater. The maximum level of metal in soil for which the equilibrium soluble metal does not violate the Drinking Water Standard can be computed, at any pH, from the measured adsorption coefficient for any metal and soil. These metal criteria can be used as soil standards that will be protective of ground water quality. Criteria for soil remediation are based on specific soil types and the effect of pH on metal sorption because the partitioning of trace metals is highly dependent on the solution pH and the chemical nature of the soil. Sorption has been used because large numbers of soil and pH values can be investigated. Based on these data, we can predict the maximum concentration of metal which would be expected to be in a solution that was in contact with a soil having a given metal concentratlon and pH. It is possible that this predicted concentration is greater than that which would actually be observed. The overprediction could result from such phenomena as slow desorption. In that cases, the overprediction would provide a measure of insurance when used as a soil standard. 土壤重金屬污染在土壤復育及地下水水質保護最主要的問題是缺乏適當合理的標準。台灣地區土壤重金屬污染防治，極需建立一套合理且適當的土壤重金屬含量標準以作為一切土壤污染防治管制策略的基礎。許多土壤遭受重金屬污染之後，常會使得地下水或農作物遭受污染，甚至被破壞至現有工程技術不可恢復之地步，縱使該地下水體可予以處理恢復，農地可恢復耕作，但其所耗之代價實在太高。尤其當地下水一旦受重金屬污染，通常造成不可彌補之嚴重問題。台灣目前尚缺乏此類標準以預測地下水受重金屬污染情形，而缺乏此類標準可能導致復育需求上的誤判。本研究係根據地下水水質標準，以數學統計方式建立一套土壤重金屬含量標準，其可作為土壤污染管制之警報值。一旦發現土壤樣品重金屬含量達到標準值，主管機關乃可立即採取適當措施予以清查汙染源及適當之管制，以免地下水及農地遭到不可恢復之破壞。重金屬於不飽和層的土壤中移動至地下水層之現象係受土壤的吸附作用及地下水中重金屬濃度影響，而此作用受pH值影響至鉅，故合理值的含量標準應與土壤的酸殮值與土壤的特性相結合。目前臺灣地區暫定的土壤重金屬調查資料甚豐，惟暫訂的含量標準為一單一標準，即不論土壤特性及pH值，皆以齊頭式之標準管制。然土壤對重金屬的吸附能力與其酸鹼值和特性有極大的關係。因此採用因地制宜的土壤重金屬含量標準將可增加土地利用的面積，同時亦可達到管制之目的。本研究即利用在不同酸鹼值下，重金屬在固相之土壤及液相之地下水中呈一平衡狀態，由地下水標準中重金屬之容許含量推導出土壤中重金屬之容許含量。
