DOI: 10.5194/hess-18-5255-2014
Scopus记录号: 2-s2.0-84919338135
论文题名: Relations between macropore network characteristics and the degree of preferential solute transport
作者: Larsbo M ; , Koestel J ; , Jarvis N
刊名: Hydrology and Earth System Sciences
ISSN: 10275606
出版年: 2014
卷: 18, 期: 12 起始页码: 5255
结束页码: 5269
语种: 英语
Scopus关键词: Agricultural chemicals
; Experiments
; Flow of water
; Flow rate
; Soils
; Solute transport
; Agricultural topsoils
; Degree of saturations
; Hydraulic properties
; Network characteristics
; Saturated conditions
; Saturated hydraulic conductivity
; Tension disc infiltrometer
; Undisturbed columns
; Hydraulic conductivity
; agricultural soil
; breakthrough curve
; hydraulic conductivity
; macropore
; preferential flow
; solute transport
; topsoil
; water flow
英文摘要: The characteristics of the soil macropore network determine the potential for fast transport of agrochemicals and contaminants through the soil. The objective of this study was to examine the relationships between macropore network characteristics, hydraulic properties and state variables and measures of preferential transport. Experiments were carried out under near-saturated conditions on undisturbed columns sampled from four agricultural topsoils of contrasting texture and structure. Macropore network characteristics were computed from 3-D X-ray tomography images of the soil pore system. Non-reactive solute transport experiments were carried out at five steady-state water flow rates from 2 to 12 mm hg'1. The degree of preferential transport was evaluated by the normalised 5% solute arrival time and the apparent dispersivity calculated from the resulting breakthrough curves. Near-saturated hydraulic conductivities were measured on the same samples using a tension disc infiltrometer placed on top of the columns. Results showed that many of the macropore network characteristics were inter-correlated. For example, large macroporosities were associated with larger specific macropore surface areas and better local connectivity of the macropore network. Generally, an increased flow rate resulted in earlier solute breakthrough and a shifting of the arrival of peak concentration towards smaller drained volumes. Columns with smaller macroporosities, poorer local connectivity of the macropore network and smaller near-saturated hydraulic conductivities exhibited a greater degree of preferential transport. This can be explained by the fact that, with only two exceptions, global (i.e. sample scale) continuity of the macropore network was still preserved at low macroporosities. Thus, for any given flow rate, pores of larger diameter were actively conducting solute in soils of smaller near-saturated hydraulic conductivity. This was associated with larger local transport velocities and, hence, less time for equilibration between the macropores and the surrounding matrix which made the transport more preferential. Conversely, the large specific macropore surface area and well-connected macropore networks associated with columns with large macroporosities limit the degree of preferential transport because they increase the diffusive flux between macropores and the soil matrix and they increase the near-saturated hydraulic conductivity. The normalised 5% arrival times were most strongly correlated with the estimated hydraulic state variables (e.g. with the degree of saturation in the macropores R 2 Combining double low line 0.589), since these combine into one measure the effects of irrigation rate and the near-saturated hydraulic conductivity function, which in turn implicitly depends on the volume, size distribution, global continuity, local connectivity and tortuosity of the macropore network. © Author(s) 2014. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/78035
Appears in Collections: 气候变化事实与影响
There are no files associated with this item.
作者单位: Department of Soil and Environment, Swedish University of Agricultural Sciences (SLU), P.O. Box 7014, Uppsala, Sweden
Recommended Citation:
Larsbo M,, Koestel J,, Jarvis N. Relations between macropore network characteristics and the degree of preferential solute transport[J]. Hydrology and Earth System Sciences,2014-01-01,18(12)