FIELD EXPERIMENTS IN A FRACTURED CLAY TILL .2. SOLUTE AND COLLOID TRANSPORT

被引：159
作者：
MCKAY, LD [1 ]
GILLHAM, RW [1 ]
CHERRY, JA [1 ]
机构：
[1] UNIV WATERLOO,WATERLOO CTR GROUNDWATER RES,WATERLOO N2L 3G1,ONTARIO,CANADA
来源：
WATER RESOURCES RESEARCH | 1993年 / 29卷 / 12期
关键词：
D O I：
10.1029/93WR02069
中图分类号：
X [环境科学、安全科学];
学科分类号：
08 ; 0830 ;
摘要：
A field tracer experiment was conducted in a lateral flow field in the weathered and highly fractured upper 6 m of a 40-m-thick clay-rich till plain in southwestern Ontario. In the upper 3 m where fractures are closely spaced (<0.13 m) the advancing front (C/C0 = 0.01) of the nonreactive solute tracers, bromide and O-18, migrated at rates of 0.01 to 0.07 m/d, over distances of 4 and 6 m and under a lateral hydraulic gradient of 0.24. In this same zone, two strains of colloid-sized bacteriophage tracers migrated at rates of 2 to > 5 m/d. Simulations with a discrete fracture/porous matrix flow and transport model, which used the cubic law for flow in fractures, showed that diffusion of the solutes, but not the much larger colloids, into the matrix pore water between fractures is sufficient to cause the observed difference in solute and colloid transport rates. Transport-derived and hydraulic conductivity-derived fracture aperture values were similar, within a factor of 3 and falling mainly within a range of 5-40 mum. In the upper 3 m the solute tracers were evenly distributed between pore water in the fractures and the matrix, and as a result, solute transport can be closely approximated with an equivalent porous medium (EPM) approach. Below this depth, fractures are more widely spaced (0.13 to > 1 m) with concentration peaks tending to occur near visible fractures, and solute transport cannot be adequately described with an EPM approach.
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页码：3879 / 3890
页数：12
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