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DEVELOPMENT OF A METHOD FOR REMOVING NITRATE DIRECTLY FROM SOIL PERCOLATE BY INTRODUCING LOW-PERMEABLITY-LAYER AND SULFUR.

开发通过引入低渗透层和硫直接从土壤渗滤液中去除硝酸盐的方法。

基本信息

批准号：
11558074
负责人：
KAWANISHI Takuya
金额：
$ 6.21万
依托单位：
KANAZAWA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

项目摘要

The objective of this research is to develop a method for removing nitrate directly from soil percolate. We construct a low permeability layer (LPL) below the level where nitrogen is sufficiently nitrified. By "low permeability layer" we mean the soil layer whose saturated hydraulic conductivity is approximately equal to the infiltration rate of the site. As the water percolates in the soil, LPL becomes saturated and acts as a barrier to oxygen supply. In addition, we put electron donor for denitrification, such as sulfur, etc. below the LPL. Thus, below LPL, oxygen concentration will be suppressed and there exist electron donors, then denitrification will occur. Two soil columns of 0.15 m in diameter and 0.8 m in height are prepared. For the one column (LPL column) we set LPL whose saturated hydraulic conductivity is approximately 0.1 m d^<-1>(20℃) at depth from 0.16 to 0.32 m. Below the LPL, sulfur (electron donor) and calcium carbonate was added to the soil in a (mass) ratio of S : CaC0_3 : soil = 5 : 5 : 90, at depths from 0.32 to 0.48 m. For the other (control) column, LPL is not prepared but sulfur and calcium carbonate was added to the soil in the same ratio at the same depths. Potassium nitrate solution of 20 mg-N∫^1 was supplied from the top of the column continuously at several different rates.In a 3-month experiment, LPL column revealed apparent nitrate removal efficiency of 0.79, 0.84 and 0.94 for the water feed rates of 0.025, 0.05 and 0.1 m d^<-1>, respectively. Thus, we concluded this Low Permeability Layer Oxygen Barrier method really works.

本研究旨在建立一种直接去除土壤渗滤液中硝酸盐的方法。我们在氮充分硝化的水平以下构建低渗透层（LPL）。所谓“低渗透层”，是指饱和导水率近似等于场地入渗率的土层。随着水渗入土壤，LPL变得饱和，并成为氧气供应的屏障。此外，我们将用于反硝化的电子供体，如硫等置于LPL下方。因此，在低于LPL时，氧浓度将被抑制，并且存在电子供体，然后将发生反硝化。准备两个直径为0.15 m、高为0.8 m的土柱。对于一个柱（LPL柱），我们设置LPL，其饱和导水率<-1>在0.16 - 0.32 m深度处约为0.1 m d^（20℃）。在LPL以下，将硫（电子供体）和碳酸钙以S：CaCO_3：土壤= 5：5：90的（质量）比添加到土壤中，深度为0.32至0.48 m。对于另一个（对照）柱，不制备LPL，但在相同深度以相同比例将硫和碳酸钙添加到土壤中。在3个月的试验中，LPL柱在进水量为0.025、0.05和0.1 m·d·^-1时的表观硝酸盐去除率分别为0.79、0.84和0.94<-1>。因此，我们得出结论，这种低渗透层氧气屏障方法确实有效。