LONG-TERM COLLOID MOBILIZATION AND COLLOID-FACILITATED TRANSPORT OF RADIONUCLIDES IN A SEMI-ARID VADOSE ZONE

doi:10.2172/1060990

GSTDTAP > 地球科学

DOI	10.2172/1060990
报告编号	INL/EXT-12-27568
来源ID	OSTI ID: 1060990
	LONG-TERM COLLOID MOBILIZATION AND COLLOID-FACILITATED TRANSPORT OF RADIONUCLIDES IN A SEMI-ARID VADOSE ZONE
	Markus Flury; James B. Harsh; Fred Zhang; Glendon W. Gee; Earl D. Mattson; Peter C. L
	2012-08-01
出版年	2012
语种	英语
国家	美国
领域	地球科学
英文摘要	The main purpose of this project was to improve the fundamental mechanistic understanding and quantification of long-term colloid mobilization and colloid-facilitated transport of radionuclides in the vadose zone, with special emphasis on the semi-arid Hanford site. While we focused some of the experiments on hydrogeological and geochemical conditions of the Hanford site, many of our results apply to colloid and colloid-facilitated transport in general. Specific objectives were (1) to determine the mechanisms of colloid mobilization and colloid-facilitated radionuclide transport in undisturbed Hanford sediments under unsaturated flow, (2) to quantify in situ colloid mobilization and colloid-facilitated radionuclidetransport from Hanford sediments under field conditions, and (3) to develop a field-scale conceptual and numerical model for colloid mobilization and transport at the Hanford vadose zone, and use that model to predict long-term colloid and colloid- facilitated radionuclide transport. To achieve these goals and objectives, we have used a combination of experimental, theoretical, and numerical methods at different spatial scales, ranging from microscopic investigationsof single particle attachment and detachment to larger-scale field experiments using outdoor lysimeters at the Hanford site. Microscopic and single particle investigations provided fundamental insight into mechanisms of colloid interactions with the air-water interface. We could show that a moving air water interface (such as a moving water front during infiltration and drainage) is very effective in removing and mobilizing particles from a stationary surface. We further demonstrated that it is particularly the advancing air-water interface which is mainly responsible for colloid mobilization. Forces acting on the colloids calculated from theory corroborated our experimental results, and confirm that the detachment forces (surface tension forces) during the advancing air-water interface movement were stronger than during the receding movement. Theory indicates that, for hydrophilic colloids, the advancing interface movement generally exerts a stronger detachment force than the receding, except when the hysteresis of the colloid-air-water contact angle is small. These results of our study are particularly relevant for colloid mobilization and transport related to three process in the vadose zone at Hanford: (1) water infiltration into sediments during rainfall or snowmelt events, (2) groundwater fluctuations as caused by river stage fluctuations, and (3) steady-state, low-flow recharge in deep vadose zone sediments. Transient water flow, like during infiltration or groundwater level fluctuations, are most conducive for colloid mobilization, but even during steady-state, low-flow recharge, colloids can be mobile, although to a much lesser extent. The results of this project have led to a comprehensive and fundamental understanding of colloid transport and mobilization under unsaturated flow conditions at the Hanford site.
英文关键词	colloids vadose zone
URL	查看原文
来源平台	US Department of Energy (DOE)
引用统计
文献类型	科技报告
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/5772
专题	地球科学
推荐引用方式 GB/T 7714	Markus Flury,James B. Harsh,Fred Zhang,et al. LONG-TERM COLLOID MOBILIZATION AND COLLOID-FACILITATED TRANSPORT OF RADIONUCLIDES IN A SEMI-ARID VADOSE ZONE,2012.