scholarly journals Effects of Infiltration Amounts on Preferential Flow Characteristics and Solute Transport in the Protection Forest Soil of Southwestern China

Water ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1301
Author(s):  
Mingfeng Li ◽  
Jingjing Yao ◽  
Ru Yan ◽  
Jinhua Cheng
Keyword(s):  
Solute Transport ◽  
Forest Soil ◽  
Preferential Flow ◽  
Soil Depth ◽  
Flow Characteristics ◽  
Solute Concentration ◽  
Southwestern China ◽  
Deep Soil ◽  
Protection Forest ◽  
Dye Tracer

Preferential flow has an important role as it strongly influences solute transport in forest soil. The quick passage of water and solutes through preferential flow paths without soil absorption results in considerable water loss and groundwater pollution. However, preferential flow and solute transport under different infiltration volumes in southwestern China remain unclear. Three plots, named P20, P40 and P60, were subjected to precipitation amounts of 20, 40 and 60 mm, respectively, to investigate preferential flow and solute transport characteristics via field multiple-tracer experiments. Stained soils were collected to measure Br− and NO3− concentrations. This study demonstrated that precipitation could promote dye tracer infiltration into deep soils. The dye tracer reached the maximum depth of 40 cm in P60. Dye coverage generally reduced with greater depth, and sharp reductions were observed at the boundary of matrix flow and preferential flow. Dye coverage peaked at the soil depth of 15 cm in P40. This result demonstrated that lateral infiltration was enhanced. The long and narrow dye coverage pattern observed in P60 indicated the occurrence of macropore flow. Br− and NO3− were found at each soil depth where preferential flow had moved. Increasing precipitation amounts increased Br− and NO3− concentration and promoted solute movement into deep soil layers. Solute concentration peaked at near the end of the preferential flow path and when preferential flow underwent lateral movement. These results indicated that the infiltration volume and transport capacity of preferential flow had important effects on the distribution of Br− and NO3− concentrations. The results of this study could help expand our understanding of the effects of preferential flow on solute transport and provide some suggestions for protection forest management in southwestern China.

Effects of stemflow on infiltration flux of rainwater and dissolved Cs-137 to forest soil

2020 ◽  
Author(s):  
Hikaru Iida ◽  
Hiroaki Kato ◽  
Tomoki Shinozuka ◽  
Satoru Akaiwa ◽  
Tatsuya Yokoyama ◽  
...  
Keyword(s):  
Forest Soil ◽  
Soil Water ◽  
Preferential Flow ◽  
Water Infiltration ◽  
Soil Horizon ◽  
Water Volume ◽  
Deep Soil ◽  
Tree Roots ◽  
Rainwater Infiltration ◽  
Tracer Techniques

<p>Stemflow takes important role on the hydrological and chemical cycling in the rhizosphere because it brings intensive rainwater input to forest soil and enhances downward infiltration of rainwater along tree root network to deep soil horizon. However, there are few studies on the effects of stemflow in rainwater infiltration mechanisms by collecting of soil water. In this study, stemflow and soil water near the tree roots (Rd : root downslope) and far from the trunk (Bt : between trees) are collected from a cedar forest in Namie Town, Fukushima Prefecture, Japan. Samples were collected from June 24 to December 11, 2019 with a total precipitation of 1100 mm during the period. Water volume and dissolved <sup>137</sup>Cs concentration drived from the Fukushima Dai-ichi Nuclear Power Plant accident were measured. As a result, Rd which is located in neighbor of the trunk showed greater water infiltration flux and high dissolved <sup>137</sup>Cs concentration. The average amount of infiltration water which was normalized for open rainfall depth during the whole sampling period was 1.4 times and 3.0 times larger at 5 cm and 20 cm depth for the Rd than the Bt, the average dissolved <sup>137</sup>Cs concentration was 1.3 times and 1.7 times larger at 5 cm and 20 cm depth, respectively. This suggests that infiltration water flux and dissolved <sup>137</sup>Cs concentration can be increased due to contribution of stemflow input at the base of tree trunk. To determine the role of stemflow on rainwater infiltration flux and the concentration of dissolved elements in the rhzosphere, further analysis is required to clarify detailed infiltration mechanisms by using multiple tracer techniques such as stable isotopic composition of water and by collecting root oriented preferential flow.</p>

scholarly journals Study on the Preferential Flow Characteristics under Different Precipitation Amounts in Simian Mountain Grassland of China

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3489
Author(s):  
Mingfeng Li ◽  
Jingjing Yao ◽  
Jinhua Cheng
Keyword(s):  
Preferential Flow ◽  
Water Movement ◽  
Flow Characteristics ◽  
Distribution Patterns ◽  
Soil Hydrology ◽  
Flow Paths ◽  
Mountain Grassland ◽  
Dye Tracer ◽  
Preferential Flow Paths ◽  
Spatial Distribution Characteristics

Understanding the response of preferential flow paths to water movement is an important topic in soil hydrology. However, quantification of the complicated distribution patterns of preferential flow paths remains poorly understood. Therefore, dye experiments were conducted to investigate preferential flow characteristics under three different precipitation amounts (20, 40 and 60 mm, numbered as the G20, G40 and G60, respectively) in Simian Mountain grassland, Chongqing province, China. O-ring statistics were used to analyze the spatial distribution characteristics and the spatial correlation of preferential flow paths. Results revealed that precipitation could promote dye tracer infiltration into deeper soils, reaching the maximum depth of 55 cm in G60. The number of preferential flow paths in G60 plots was 3.0 and 7.4 times greater than those of G40 and G20, respectively. Structural distribution of the preferential flow paths showed a gradually clumped pattern with the increase of precipitation, which was conducive to enhancing the correlation between preferential flow paths in each pore size range. These results could expand our understanding of the effects of precipitation on the characteristic of preferential flow paths in grassland, which is helpful to evaluate the water movement in the study area.

scholarly journals Non-Fickian Solute Transport in Rough-Walled Fractures: The Effect of Contact Area

Water ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 2049 ◽  
Author(s):  
Yingtao Hu ◽  
Wenjie Xu ◽  
Liangtong Zhan ◽  
Zuyang Ye ◽  
Yunmin Chen
Keyword(s):  
Solute Transport ◽  
Contact Area ◽  
Concentration Distribution ◽  
Preferential Flow ◽  
Three Dimensional ◽  
Solute Concentration ◽  
Breakthrough Curves ◽  
Contact Areas ◽  
Fracture Surfaces ◽  
Early Arrival

The influence of contact area, caused by normal deformation, on fluid flow and solute transport through three-dimensional (3D) rock fractures is investigated. Fracture surfaces with different Hurst exponents (H) were generated numerically using the modified successive random addition (SRA) method. By applying deformations normal to the fracture surface (Δu), a series of fracture models with different aperture distributions and contact area ratios (c) were simulated. The results show that the contact area between the two fracture surfaces increases and more void spaces are reduced as deformation (Δu) increases. The streamlines in the rough-walled fractures show that the contact areas result in preferential flow paths and fingering type transport. The non-Fickian characteristics of the “early arrival” and “long tail” in all of the breakthrough curves (BTCs) for fractures with different deformation (Δu) and Hurst parameters (H) were determined. The solute concentration distribution index (CDI), which quantifies the uniformity of the concentration distribution within the fracture, decreases exponential as deformation (Δu) and/or contact area ratios (c) increase, indicating that increased contact area can result in a larger delay rate of mass exchange between the immobile zone around the contact areas and the main flow channel, thus, resulting in a longer time for the solute to fill the entire fracture. The BTCs were analyzed using the continuous time random walk (CTRW) inverse model. The inverse modeling results show that the dispersion exponent β decreases from 1.92 to 0.81 as c increases and H decreases, suggesting that the increase in contact area and fracture surfaces enhance the magnitude of the non-Fickian transport.

scholarly journals Predicting subsurface storm flow response of a forested hillslope: the role of connected flow paths and bedrock topography

2013 ◽  
Vol 10 (5) ◽  
pp. 6473-6514 ◽  
Author(s):  
J. Wienhöfer ◽  
E. Zehe
Keyword(s):  
Solute Transport ◽  
Preferential Flow ◽  
Soil Depth ◽  
Quantitative Description ◽  
Flow Simulation ◽  
Tracer Experiment ◽  
Lateral Flow ◽  
Retention Capacity ◽  
Flow Paths ◽  
Preferential Flow Paths

Abstract. Rapid flow processes in connected preferential flow paths are widely accepted to play a key role for rainfall-runoff response at the hillslope scale, but a quantitative description of these processes is still a major challenge in hydrological research. This paper investigates the approach of incorporating preferential flow paths explicitly in a process-based model for modelling water flows and solute transport at a steep forested hillslope. We conceptualise preferential flow paths as spatially explicit structures with high conductivity and low retention capacity, and evaluate simulations with different combinations of vertical and lateral flow paths against measured discharge and tracer breakthrough. Out of 122 tested realisations, five setups fulfilled our selection criteria for the water flow simulation. These setups successfully simulated infiltration, vertical and lateral subsurface flow in structures, and allowed predicting the magnitude, dynamics and water balance of the hydrological response of the hillslope during subsequent periods of steady-state sprinkling on selected plots and intermittent rainfall on the entire hillslope area. The solute transport simulations with these setups matched spread and shape of the observed breakthrough curve well, indicating that macrodispersion induced by preferential flow was captured well by the topology of the preferential flow network. The model, however, could not match the very fast breakthrough times observed in the tracer experiment. This can readily be attributed to the simplified representation of the spatial dimensions of the implemented distinctive structures in the 2-D cross-section, which led to an underestimation of effective transport velocities in comparison to the correctly modelled flux densities. The configurations of successful model setups suggest that preferential flow bound to connected vertical and lateral flow paths is a first-order control on the hydrology of the study hillslope, whereas spatial variability of soil depth is secondary. Virtual experiments for investigating hillslope controls on subsurface processes should thus explicitly consider distinctive flow paths as a potential determinant.

scholarly journals A simple model for predicting solute concentration in agricultural tile lines shortly after application

1997 ◽  
Vol 1 (4) ◽  
pp. 823-833 ◽  
Author(s):  
T. S. Steenhuis ◽  
M. Bodnar ◽  
L. D. Geohring ◽  
S.-A. Aburime ◽  
R. Wallach
Keyword(s):  
Simple Model ◽  
Field Experiments ◽  
Preferential Flow ◽  
Flow Characteristics ◽  
Chloride Concentration ◽  
Soil Surface ◽  
Solute Concentration ◽  
Flow Paths ◽  
Soil Matrix ◽  
Preferential Flow Paths

Abstract. Agricultural tile drainage lines have been implicated as a source of pesticide contamination of surface waters. Field experiments were conducted and a simple model was developed to examine preferential transport of applied chemicals to agricultural tile lines. The conceptual model consists of two linear reservoirs, one near the soil surface and one near the tile drain. The connection between the two reservoirs is via preferential flow paths with very little interaction with the soil matrix. The model assumes that only part of the field contributes solutes to the tile drain. The model was evaluated with data from the field experiments in which chloride, 2,4-D, and atrazine concentrations were measured on eight tile-drained plots that were irrigated twice. Atrazine was applied two months prior to the experiment, 2,4-D was sprayed just before the first irrigation, and chloride before the second irrigation. All three chemicals were found in the tile effluent shortly after the rainfall began. Generally, the concentration increased with increased flow rates and decreased exponentially after the rainfall ceased. Although the simple model could simulate the observed chloride concentration patterns in the tile outflow for six of the eight plots, strict validation was not possible because of the difficulty with independent measurement of the data needed for a preferential flow model applied to field conditions. The results show that, to simulate pesticide concentration in tile lines, methods that can measure field averaged preferential flow characteristics need to be developed.

Equation for Describing Solute Transport in Field Soils with Preferential Flow Paths

2005 ◽  
Vol 69 (2) ◽  
pp. 291-300 ◽  
Author(s):  
Young-Jin Kim ◽  
Christophe J. G. Darnault ◽  
Nathan O. Bailey ◽  
J.-Yves Parlange ◽  
Tammo S. Steenhuis
Keyword(s):  
Solute Transport ◽  
Preferential Flow ◽  
Flow Paths ◽  
Preferential Flow Paths ◽  
Field Soils

scholarly journals Comparison of Drivers of Soil Microbial Communities Developed in Karst Ecosystems with Shallow and Deep Soil Depths

Agronomy ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 173
Author(s):  
Huiling Guan ◽  
Jiangwen Fan ◽  
Haiyan Zhang ◽  
Warwick Harris
Keyword(s):  
Microbial Community ◽  
Microbial Communities ◽  
Soil Depth ◽  
Phospholipid Fatty Acid ◽  
Soil Microbial Communities ◽  
Deep Soil ◽  
Soil System ◽  
Soil Microbial ◽  
Total Soil ◽  
Karst Ecosystems

Soil erosion is prevalent in karst areas, but few studies have compared the differences in the drivers for soil microbial communities among karst ecosystems with different soil depths, and most studies have focused on the local scale. To fill this research gap, we investigated the upper 20 cm soil layers of 10 shallow–soil depth (shallow–SDC, total soil depth less than 100 cm) and 11 deep–soil depth communities (deep–SDC, total soil depth more than 100 cm), covering a broad range of vegetation types, soils, and climates. The microbial community characteristics of both the shallow–SDC and deep–SDC soils were tested by phospholipid fatty acid (PLFAs) analysis, and the key drivers of the microbial communities were illustrated by forward selection and variance partitioning analysis. Our findings demonstrated that more abundant soil nutrients supported higher fungal PLFA in shallow–SDC than in deep–SDC (p < 0.05). Furthermore, stronger correlation between the microbial community and the plant–soil system was found in shallow–SDC: the pure plant effect explained the 43.2% of variance in microbial biomass and 57.8% of the variance in the ratio of Gram–positive bacteria to Gram–negative bacteria (G+/G−), and the ratio of fungi to total bacteria (F/B); the pure soil effect accounted for 68.6% variance in the microbial diversity. The ratio of microbial PLFA cyclopropyl to precursors (Cy/Pr) and the ratio of saturated PLFA to monounsaturated PLFA (S/M) as indicators of microbial stress were controlled by pH, but high pH was not conducive to microorganisms in this area. Meanwhile, Cy/Pr in all communities was >0.1, indicating that microorganisms were under environmental stress. Therefore, the further ecological restoration of degraded karst communities is needed to improve their microbial communities.

scholarly journals Prediction of leaching and groundwater contamination by pesticides

2006 ◽  
Vol 78 (5) ◽  
pp. 1081-1090 ◽  
Author(s):  
Werner Kördel ◽  
Michael Klein
Keyword(s):  
Maximum Concentration ◽  
Management Practices ◽  
Preferential Flow ◽  
Soil Depth ◽  
Sandy Soils ◽  
Field Studies ◽  
Macropore Flow ◽  
Eu Directive ◽  
Present Information ◽  
Silty Soils

Herein, we describe how pesticide leaching is assessed in Europe in order to fulfill EU Directive 91/414. The assessment schemes were developed to protect groundwater from unacceptable effects caused by pesticide use. They presently focus on chromatographic flow processes, which are dominant in sandy soils. Nevertheless, important regions in Europe are characterized by structured soils where transport through macropores is most relevant.Comparison of parallel field studies with isoproturon performed in sandy and silty soils showed that maximum concentration in the structured soil at a soil depth of 1 m may exceed respective concentrations in sandy soils by a factor of 60. Similar results were obtained by lysimeter studies using silty soil cores with maximum concentration of 40 μg/l at the soil bottom. These results demonstrate that preferential flow is more the rule than the exception in well-structured fine-textured soils, and pesticide losses via macropore flow may exceed losses via matrix transport considerably. All present information available for macropore flow suggest the need for greater regional assessments. Other recommendations include analysis of the influence of different soil management practices on the formation of macropores.

scholarly journals Dye staining and excavation of a lateral preferential flow network

2009 ◽  
Vol 13 (6) ◽  
pp. 935-944 ◽  
Author(s):  
A. E. Anderson ◽  
M. Weiler ◽  
Y. Alila ◽  
R. O. Hudson
Keyword(s):  
Slope Stability ◽  
Solute Transport ◽  
Preferential Flow ◽  
Runoff Generation ◽  
Flow Paths ◽  
Soil Matrix ◽  
Preferential Flow Paths ◽  
Dye Staining ◽  
Hillslope Scale ◽  
Surrounding Soil

Abstract. Preferential flow paths have been found to be important for runoff generation, solute transport, and slope stability in many areas around the world. Although many studies have identified the particular characteristics of individual features and measured the runoff generation and solute transport within hillslopes, very few studies have determined how individual features are hydraulically connected at a hillslope scale. In this study, we used dye staining and excavation to determine the morphology and spatial pattern of a preferential flow network over a large scale (30 m). We explore the feasibility of extending small-scale dye staining techniques to the hillslope scale. We determine the lateral preferential flow paths that are active during the steady-state flow conditions and their interaction with the surrounding soil matrix. We also calculate the velocities of the flow through each cross-section of the hillslope and compare them to hillslope scale applied tracer measurements. Finally, we investigate the relationship between the contributing area and the characteristics of the preferential flow paths. The experiment revealed that larger contributing areas coincided with highly developed and hydraulically connected preferential flow paths that had flow with little interaction with the surrounding soil matrix. We found evidence of subsurface erosion and deposition of soil and organic material laterally and vertically within the soil. These results are important because they add to the understanding of the runoff generation, solute transport, and slope stability of preferential flow-dominated hillslopes.

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