scholarly journals A Simulation of Salt Transport in NaCl-Laden Soil Barrier to Control Subterranean Termites in an Earth Embankment

Water ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1204
Author(s):  
Ying Li ◽  
Dong-Zi Pan
Keyword(s):  
Hydraulic Conductivity ◽  
Saturated Hydraulic Conductivity ◽  
Rainfall Infiltration ◽  
Salt Transport ◽  
Subterranean Termite ◽  
Water Level Fluctuations ◽  
Subterranean Termites ◽  
Promising Alternative ◽  
Earth Embankment

Subterranean termite activity can increase the hydraulic conductivity and water infiltration of filling soil, and therefore affects the stability of an earth embankment and subsequent safety. As a physical barrier for sustainable termite management, NaCl-laden soil barrier (NLSB) is a promising alternative for subterranean termite control in earth embankments. This novel technology can prevent tunneling and penetration of subterranean termites into the interior of an embankment and has been widely employed for more than 20 years in Zhejiang Province, China. The efficacy and longevity of NLSB depend on the long-term presence of NaCl concentration in soil barriers. The aim of this study is to develop an understanding of water flow and salt transport in NLSB based on the two-dimensional Richards’ equation and convection dispersion equation using the HYDRUS software package. Conceptual and numerical models of NLSB are modeled using scenario analysis according to water level fluctuations, saturated hydraulic conductivity, and rainfall infiltration conditions. Furthermore, the center and spread variance of a solute mass over a 100-year period are quantified using moment analysis. As flood frequency, saturated hydraulic conductivity, and rainfall infiltration flux increase, salt desalination in NLSB significantly increases. When the rainfall infiltration flux is 1% of the annual average rainfall, the total amount of salt transport and leaching can increase by 55%. Moreover, these results facilitate better long-term sustainable management of existing sites and optimal design of future NLSBs.

scholarly journals Barrier Longevity of NaCl-Laden Soil against Subterranean Termites in an Earth Embankment

2021 ◽  
Vol 13 (23) ◽  
pp. 13360
Author(s):  
Ying Li ◽  
Dong-Zi Pan
Keyword(s):  
Control Method ◽  
Salt Transport ◽  
Subterranean Termite ◽  
Richards Equation ◽  
Subterranean Termites ◽  
Environmentally Sustainable ◽  
Nacl Concentration ◽  
Field Efficacy ◽  
Earth Embankment ◽  
Good Potential

Subterranean termite-induced damage to earth embankments in agricultural systems occurs globally. NaCl-laden soil barriers (NLSBs) are an environmentally sustainable termite control method, and have exhibited good potential in preventing termite-related tunneling damage in Zhejiang Province, China. The persistence of the NaCl concentration in NLSBs is a key characteristic for the long-term prevention of subterranean termite infestations. This study is a scientific attempt to estimate the field efficacy and barrier longevity of NLSBs in reservoir embankments based on the Richards equation and the convection–dispersion equation using HYDRUS (2D/3D). The observed and simulated NaCl concentrations at the end of a 1915-day simulation were compared. The results indicated that the proposed model performed well and can effectively characterize the water flow and salt transport in NLSBs. The salt desalination rate of the NLSB in the upstream slope was higher than that in the downstream slope, both of which were significantly higher than that at the embankment axis. Regardless of the type of embankment (homogeneous or core-wall), the barrier longevity of NaCl-laden soil against subterranean termites can reach 50 years with an optimized NaCl/soil ratio in different parts of the embankment.

Performance of two small experimental bioretention cells during the first year of operation

2021 ◽  
Author(s):  
Petra Hečková ◽  
Michal Sněhota ◽  
Vojtěch Bareš ◽  
David Stránský
Keyword(s):  
Hydraulic Conductivity ◽  
Growing Season ◽  
Time Domain Reflectometry ◽  
Saturated Hydraulic Conductivity ◽  
Runoff Coefficient ◽  
Rainfall Runoff ◽  
Bioretention Cell ◽  
Gravel Mulch ◽  
Peak Outflow

<p>Due to increasing urbanization, bioretention cells are becoming an increasingly popular solution for stormwater management. The data on long term performance bioretention are still sparse. The aim of this study was to set-up two experimental bioretention cells designed for long-term monitoring and to evaluate the rainfall-runoff characteristics, assess the development of properties of the biofilter, and dynamics of plant growth during the first growing season.</p><p>Two identical experimental bioretention cells were established. The first collects water from the roof and the second is supplied from the tank for simulating artificial rainfall. The 30 cm thick biofilter soil mixture is composed of 50% sand, 30% compost, and 20% topsoil. Bioretention cells are isolated from the surrounding soil by a waterproof membrane. Both bioretention cells are instrumented by an identical system of sensors. Four time-domain reflectometry probes monitor soil water contents 20 cm below the surface. Five tensiometers record the water potential in a biofilter. The amount of a discharge from each bioretention cell is determined by a tipping bucket flowmeter. A ponding depth is recorded by an ultrasonic sensor.</p><p>Rainfall-runoff episodes were evaluated for the period from 18.6. 2018 to the 22.11.2018. 17 episodes were evaluated for bioretention cell with the inflow of stormwater from the roof. Six ponding experiments were done in the bioretention cell with an artificial supply. Rainfall depth, maximal rainfall intensity, episode duration, runoff coefficient, and maximal peak outflow rate from both bioretention cells were determined for each episode. The effective saturated hydraulic conductivity was determined using Darcy’s law under the assumption of one-dimensional, vertical flow. The estimation method was verified by simulating two-dimensional variably saturated flow using HYDRUS-2D. Outflow water quality was measured from one bioretention cell during ponding experiments.</p><p>The runoff coefficient for the entire period of the growing season was 0.72, while the peak outflow reduction for individual rainfall events ranged between 75% to 95% for the bioretention cell connected to the roof. The runoff coefficient determined from artificial ponding events was 0.86 for the event started in the partially saturated biofilter, while it was nearly 1.0 for all subsequent artificial ponding events. The peak flow reduction ranged from 19% to 30%. The saturated hydraulic conductivity of biofilter with a natural rainfall supply ranged between 1.6·10<sup>-6</sup> to 8.6∙10<sup>-6</sup> m·s<sup>-1</sup>, which is significantly less than hydraulic conductivity 1.3∙10<sup>-4</sup> m·s<sup>-1</sup> measured in the laboratory on packed samples. Perennials Aster, Hemerocallis and Molinia have shown good growth and adaptation to conditions in bioretention cells. In the case of the current experiment, the gravel mulch layer has proven to be an effective barrier to reducing evaporation. The values of total suspended solids and turbidity were highly correlated and generally high, especially at the beginning of outflow in artificial ponding experiments. The value of electrical conductivity reached up to 2200 µS·cm<sup>-1</sup>, this may be due to the higher compost content in the soil. The monitoring of bioretention cells continues in order to record long term changes in the performance of the bioretention cells.</p>

scholarly journals Rainfall Infiltration Process of a Rock Slope with Considering the Heterogeneity of Saturated Hydraulic Conductivity

2022 ◽  
Vol 9 ◽  
Author(s):  
Qingqing Zhang ◽  
Laigui Wang ◽  
Huabin Zhang
Keyword(s):  
Hydraulic Conductivity ◽  
Safety Factor ◽  
Rock Slope ◽  
Rainfall Intensity ◽  
Saturated Hydraulic Conductivity ◽  
Rainfall Infiltration ◽  
Infiltration Depth ◽  
Infiltration Process ◽  
Rainfall Duration ◽  
Unsaturated Seepage

In order to analyze the effects of rainfall events on the stability of an open-pit rock slope, with considering the spatial variability of saturated hydraulic conductivity, based on the unsaturated seepage theory and the random filed theory, modified functions of the unit saturation, the hydraulic conductivity (k), and the shear strength parameters are established for unsaturated slope, by using FISH and the non-intrusive stochastic method. A saturated-unsaturated seepage random field model is proposed. And then the impacts of the rainfall intensity, the rainfall duration, and the spatial variability of saturated hydraulic conductivity (ks) on the infiltration process and stability of the unsaturated rock slope are analyzed. The results show that the proposed model can estimate rainfall infiltration of rock slope accurately. Rainfall mainly affects the seepage field in the shallow layer of the slope, where a transient saturated zone can be formed. With the development of the rainfall duration, the weight of the rock mass increased, the matric suction reduced, the negative pore pressure, the degree of saturation, and the infiltration depth of the rock slope increased, and the water in the slope root connects with the initial water table gradually, the unsaturated zone shrinks, which causes the safety factor of the model decreases, but the trend of change slows down gradually. As the rainfall intensity strengthened, the infiltration depth increased and the safety factor of the slope reduced, while the changing rate increases first and then decreases. Increasing the correlation length of k can reduces the infiltration depth and safety factor of the slope. Increasing the variation coefficient of k will increase the infiltration depth, while the safety factor of the slope decreases. The infiltration depth and safety factor of the slope are most affected by rainfall duration, but its sensitivity to the variability coefficient of k will be strengthened when the rainfall intensity exceeds the infiltration capacity. This conclusion can provide reference significance for the risk estimation of slope geological hazards, which are induced by the rainfall infiltration.

The long-term effects of silvicultural thinning and partial cutting on soil compaction in red pine (Pinus resinosa Ait.) and northern hardwood stands in the northern Great Lakes Region of the United States

2008 ◽  
Vol 88 (5) ◽  
pp. 849-857 ◽  
Author(s):  
R A Tarpey ◽  
M F Jurgensen ◽  
B J Palik ◽  
R K Kolka
Keyword(s):  
Hydraulic Conductivity ◽  
Bulk Density ◽  
Soil Compaction ◽  
Basal Area ◽  
Penetration Resistance ◽  
Saturated Hydraulic Conductivity ◽  
Red Pine ◽  
North Central ◽  
Soil Penetration Resistance

Periodic silvicultural thinnings (23.0, 27.6, 32.1 m2 ha-1 residual basal area) in a red pine stand growing on a sandy soil in north-central Minnesota over a 57-yr period increased soil compaction as the intensity of the thinning treatment increased. Of the three different methods used to measure soil compaction (bulk density, penetration resistance, and saturated hydraulic conductivity), saturated hydraulic conductivity was the most sensitive, decreasing by 60% in the 23.0 m2 ha-1 basal area thinning treatment, as compared with the uncut control. Soil bulk density measurements were more variable, but generally increased with increased thinning intensity. Few differences in soil penetration resistance were found among the three thinning treatments. In contrast, no evidence of soil compaction was detected in a northern hardwoods stand growing on a rocky loam soil in north-central Wisconsin that had three thinning treatments (13.8, 17.2, 20.6 m2 ha-1 residual basal area), a two- stage shelterwood harvest, and a 20-cm-diameter limit cut over a 50-yr period. With the increased demand for forest products, fuel reduction operations in high fire-risk stands, and biomass removal for energy production, more information is needed on the impact of multiple stand entries on soil compaction, and if compaction occurs, whether it will affect long-term soil productivity. Key words: Soil physical properties, bulk density, soil penetration resistance, hydraulic conductivity

Saturated Hydraulic Conductivity of Clayey Tills and the Role of Fractures

1990 ◽  
Vol 21 (2) ◽  
pp. 119-132 ◽  
Author(s):  
Johnny Fredericia
Keyword(s):  
Hydraulic Conductivity ◽  
American Studies ◽  
Field Measurements ◽  
Present Knowledge ◽  
Saturated Hydraulic Conductivity ◽  
Field Observations ◽  
Laboratory Measurements ◽  
Vertical Hydraulic Conductivity ◽  
Data Field

The background for the present knowledge about hydraulic conductivity of clayey till in Denmark is summarized. The data show a difference of 1-2 orders of magnitude in the vertical hydraulic conductivity between values from laboratory measurements and field measurements. This difference is discussed and based on new data, field observations and comparison with North American studies, it is concluded to be primarily due to fractures in the till.

Changes over time in near‐saturated hydraulic conductivity of peat soil following reclamation for agriculture

2019 ◽  
Vol 34 (2) ◽  
pp. 237-243
Author(s):  
Jari Hyväluoma ◽  
Mari Räty ◽  
Janne Kaseva ◽  
Riikka Keskinen
Keyword(s):  
Hydraulic Conductivity ◽  
Peat Soil ◽  
Saturated Hydraulic Conductivity ◽  
Changes Over Time ◽  
Over Time
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