Impact of the Capillary Fringe on Local Flow, Chemical Migration, and Microbiology

Abstract

We critically examine historical and recent studies of flow and transport at the local scale within the capillary fringe (CF). The characterization of subsurface pathways traveled by water—and the impact of these pathways on the movement of chemicals and the viability of subsurface microbial populations—has been the subject of intensive investigation in the last 50 yr in the fields of soil science and hydrology. However, consideration of the complexity of local pathways within the CF has been largely ignored. Recent studies, as well as some historical ones, have reported observations of fluid flow and chemical transport within the CF, emphasizing the impact of physical heterogeneity and exchange of water and chemicals between the CF and the region below the water table. These observations lead to the conclusion that the CF may affect, at the local scale, the natural geochemical and microbial conditions present in the region of transition from unsaturated to saturated groundwater flow far more significantly than is usually assumed. Here, we examine underlying physical factors that control local flow and transport behaviors in and across the CF and illustrate these factors through examination of images collected in the laboratory. We also provide a brief survey of the literature on the CF. It is argued that existing definitions of the CF are inadequate to describe flow and transport behavior in the vicinity of the water table. We suggest replacing the concept of the CF with the concept of a partially saturated fringe, which involves multiphase transport in the immediate vicinity of (both above and below) the water table.

Soil Water and Shallow Groundwater Relations in an Agricultural Hillslope

“…Th is interaction could be important for increased plant available water (Van Bavel et al, 1968;Allmaras et al, 1975;Van Bavel and Ahmed, 1976;Stuff and Dale, 1978), solute transport back into the root zone (Berkowitz et al, 2004;Logsdon, 2007;Abit et al, 2008), soil water variation at diff erent landscape positions (Logsdon et al, 1999), possible evapotranspiration variation at diff erent landscape positions (Chen and Hu, 2004), and surface and lateral redistribution of soil water and eff ect on tile drainage (James and Fenton, 1993;Khan and Fenton, 1994;Kohne and Gerke, 2005). Further study is needed to quantify these eff ects in agricultural landscapes.…”

Evidence for microbial mediated nitrate cycling within floodplain sediments during groundwater fluctuations

“…S6). Under these conditions, the relative importance of anammox as a pathway for nitrogen loss declines, however, anammox biomass does not decline (data not shown), 15 and in many cases increases as more NH 4 + becomes available.…”

Ascensão capilar de água em substratos de coco e de pinus

“…Segundo esse autor, a capilaridade também está presente na retenção de água de solos devido aos microporos, determinando nas camadas superficiais do solo um fluxo ascensional de água devido aos processos de evapotranspiração (Berkowitz et al, 2004). No entanto, a atuação da capilaridade é dependente da interação de outros fatores, tais como das características das partículas de solo ao molhamento (Goebel et al, 2002) e seu envolvimento com produtos hidrofóbicos que geram maiores de ângulo de contato na interface do colóide com a água (Bachmann et al, 2000).…”