包气带中轻非水相流体运移速率的研究

Study on migration rate of LNAPL in vadose zone

轻非水相流体(LNAPL)从地表入渗至饱水带污染地下水的过程中,其运移速率及包气带厚度决定了污染物到达饱水带的时间。全面地了解LNAPL的分布,可为修复土壤污染提供参考。本文通过三组室内试验,研究了不同入渗压力及不同入渗方式对LNAPL运移速率的影响。试验结果表明,同等入渗方式下入渗压力越大,LNAPL入渗速率越大,到达饱水带的时间越短;同等入渗压力下,点状自由入渗到达饱水带的时间较长;点状自由入渗在未到达毛细带时,其竖直方向运移速率较大且稳定,到达毛细带一定深度后,LNAPL的运移速率急速下降;面状压渗过程中,LNAPL入渗速率上下浮动,速率曲线呈波浪式,入渗方式呈现"活塞"式下渗,但总体上入渗速率呈现下降趋势。

The time of arriving at saturated zone in the course of LNAPL（ light nonaqueous phase liquid）infiltration from surface to saturation zone is determined by the migration rate of LNAPL and thickness of vadose zone. Enhanced understanding of the distribution of LNAPL could provide a reference for restoration of soil contamination. The impact of infitration pressure and the infiltration pattern on the LNAPL migration rate is studied through three different laboratory experiments in this paper. The results show that the LNAPL migration rate different laboratory experiments in this paper. The results show that the migration rate of LNAPL under the same infiltration pattern is more fast under a highter infiltration pressure,and the time of arriving at saturation zone is shorter; free point infiltration took a longer time to arrive at the saturation zone under the same infiltration pressure; the vertical migration rate will be high and steady under free point infiltration before the LNAPL arriving at the capillary fringe,but will decline rapidly after infiltration to a certain depth in capillary fringe; in the process of planar pressure infiltration,the infiltration rate of LNAPL is fluctuate in a wave-shaped curve and the trend is decrease in general.