ISMC2021-4

Modelling of soil contamination, transport of pollutants and evaluation of soil functions at all scales

Human society during the past several centuries has created a large number of chemical substances that often find their way into the environment. Since many of these chemicals represent a significant health risk when they enter the food chain, contamination of both surface and subsurface water supplies has become a major issue. Modern agriculture uses an unprecedented number of chemicals, both in plant and animal production. A broad range of fertilizers, pesticides, and fumigants are now routinely applied to agricultural lands, thus making agriculture one of the most important sources for non-point source pollution. Agriculture also increasingly uses a variety of pharmaceuticals and hormones in animal production many of which, along with pathogenic microorganisms, are being released to the environment through animal waste. Meanwhile, modern industrial and mining activities are releasing varieties of pollutants to surrounding environments. Environmental behaviors of these chemicals from industrial contamination sites are complicated and their risks are hard to regulate.

Mathematical models are critical components of any effort to optimally understand and quantify site-specific subsurface water flow and solute transport processes. Models can be helpful tools for designing, testing, and implementing soil, water, and crop management practices that minimize soil and water pollution. Models are equally needed for designing or remediating industrial contamination sites, waste disposal sites, and landfills, or for long-term risk management of nuclear waste repositories, mining areas, and groundwater polluted by industrial activities. A large number of specialized numerical models now exist to simulate the different processes at various levels of approximation and for different applications.

This session welcomes contributions on recent advances in numerical modeling of the physicochemical (hydrogeological, geochemical, and microbiological) processes affecting the fate and transport of subsurface pollutants (ranging from organic pollutants, heavy metals, and radionuclides to pathogens and nanoparticles). Investigations of emerging contaminants are especially welcome. We encourage broad participation bridging traditional research areas, including groundwater, vadose zone, groundwater-surface water interactions, biology, chemistry, and soil physics.

Conveners: Diederik Jacques, Jiri Simunek, Ulrich Weller | Co-Conveners: Weiping Chen, Guanhua Huang
Oral
| Thu, 20 May, 11:00–12:30 (CEST)
Interactive
| Thu, 20 May, 12:30–14:00 (CEST)

Oral: Thu, 20 May

Chairpersons: Diederik Jacques, Ulrich Weller
Modelling soil contamination and transport of pollutant
11:00–11:15
|
ISMC2021-95
Joachim Tremosa, Mathieu Debure, Diederik Jacques, and Francis Claret

A HPx model that jointly considered the flow, transport, gas diffusion and reactivity processes induced by exposure to the atmosphere of a recently excavated shale was used for the interpretation of a weathering experiment in a lysimeter. The lysimeter was filled with a mechanically disaggregated shale presenting preferential pathways for water and a hydraulic conductivity at saturation of 100 cm/day. The water content and the seasonal saturation and desaturation cycles were identified as the main driving mechanisms of shale alteration. The water content determined the diffusion of gaseous oxygen in the shale’s unsaturated porosity, which gave rise to a zonation of the oxidation of pyrite, contained at 1 wt% in the shale. The oxidation of pyrite induces a release of sulphates, cations, iron and trace metals (Pb, Ni, Zn, Co, Cu and As). The acidification due to pyrite oxidation is buffered by calcite dissolution. While the formation of iron (oxy-)hydroxide is efficient for sorbing trace metals, whose content remained at low concentrations in the drainage water. Seasonal precipitation of gypsum during the summer desaturation at the top of the lysimeter was also identified. The hydraulic, chemical and mineralogical observations made in the lysimeters were reproduced using HPx reactive transport code under unsaturated conditions. It was possible to account for the gas diffusion where O2 availability controlled the reactivity with the shale, depending on the meteorological conditions and the drainage at the base of the lysimeter.

How to cite: Tremosa, J., Debure, M., Jacques, D., and Claret, F.: Simulation of shale weathering by seasonal O2 diffusion in a variably saturated soil, 3rd ISMC Conference ─ Advances in Modeling Soil Systems, online, 18–22 May 2021, ISMC2021-95, https://doi.org/10.5194/ismc2021-95, 2021.

11:15–11:30
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ISMC2021-11
Daniel McKay Flecher, Siul Ruiz, Tiago Dias, Katherine Williams, Chiara Petroselli, Davey Jones, David Chadwick, and Tiina Roose

Half of the nitrogen applied to arable-fields is lost through several processes linked to soil moisture. Low soil moisture limits nitrogen mobility reducing nitrogen-uptake while wetter conditions can increase nitrogen leaching. Rainfall ultimately governs soil moisture and the fate of nitrogen in soil. However, the interaction between rainfall and nitrogen use efficiency (NUE) remains poorly understood.

We developed a field-scale modelling platform that describes coupled water and nitrogen transport, root growth and uptake, rainfall, the nitrogen-cycle and leaching to assess the NUE of split fertilisations with realistic rainfall patterns. The model was solved for every possible split fertilisation timing in 200+ growing seasons to determine optimal timings. Two previous field trials regarding rainfall and NUE had contrasting results: wetter years have enhanced fertiliser loss and drier years reduced plant nitrogen uptake. By choosing appropriate fertilisation timings in the model we could recreate the two contrasting trends and maintain variability in the data. However, we found by choosing other fertilisation timings we could mitigate the leaching in wetter years. Optimised timings could increase plant nitrogen uptake by up to 35% compared to the mean in dry years. Plant uptake was greatest under drier conditions due to mitigated leaching, but less likely to occur due to low nitrogen mobility. Optimal fertilisation timings varied dramatically depending on the rainfall patterns. Historic and projected rainfall patterns from 1950-2069 were used in the model. We found optimal NUE has a decrease from 2022-2040 due to increased heavy rainfall events and optimal fertilisation timings are later in the season but varied largely on a season-to-season basis.

The results are a step towards achieving improved nitrogen efficiency in agriculture by using the ‘at the right time’ agronomic-strategy in the ‘4Rs’ of improved nitrogen fertilisation. Our results can help determine nitrogen fertilisation timings in changing climates.

How to cite: McKay Flecher, D., Ruiz, S., Dias, T., Williams, K., Petroselli, C., Jones, D., Chadwick, D., and Roose, T.: A computational history and outlook of nitrogen use efficiency and precipitation-optimal fertilisation timings in agriculture, 3rd ISMC Conference ─ Advances in Modeling Soil Systems, online, 18–22 May 2021, ISMC2021-11, https://doi.org/10.5194/ismc2021-11, 2021.

11:30–11:45
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ISMC2021-22
Marialaura Bancheri, Antonio Coppola, Annachiara Colombi, and Angelo Basile

The scope of this work is to present the extended transfer function model (TFM-ext) that allows to simulate the spatio-temporal distribution of nonpoint-source pollutants, e.g., pesticides, along the unsaturated zone, till the groundwater table depth.

The model is based on the transfer functions approach, i.e., on the travel time probability density functions (TT pdfs), which describe the leaching behavior in a given soil profile. The strength of the model, despite the important assumptions on time-invariant TT pdfs and steady-state input fluxes, is that it derives the TT pdfs from a physical quantity, i.e., the unsaturated hydraulic conductivity function k(θ).  Moreover, the model extends the transport process to the generic depth z, where information on hydraulic properties could not be available, assuming a lognormal travel time pdf, whose parameters are scaled according to the generalized transfer function model. In the case of reactive solutes, the model considers both the mass decay and the retardation factor.

The TFM-ext was validated in Valle Telesina, a hilly area of around 200 km2 in Italy. Forty-six soil profiles, completely characterized from the hydrological point of view, were used to evaluate the mean travel times and the breakthrough curves at the groundwater depth and then compared with the results of a physically based model, Hydrus 1D. Results gave very high correlation coefficients (above 0.8), a mean absolute error of around 40 days and a percent bias of -16%.

Moreover, a comprehensive sensitivity analysis to evaluate to which parameters the TFM-ext is more sensitive, was performed. Results shown that τ anf θs parameters related to the slope of the k(θ) are those affecting more the travel time.

The model was implemented as an operative tool for the specific groundwater vulnerability assessment within the geospatial Decision Support System developed for LANDSUPPORT H2020 project.

How to cite: Bancheri, M., Coppola, A., Colombi, A., and Basile, A.: The extended transfer function model for the simulation of pesticides transport along the unsaturated zone, 3rd ISMC Conference ─ Advances in Modeling Soil Systems, online, 18–22 May 2021, ISMC2021-22, https://doi.org/10.5194/ismc2021-22, 2021.

Modelling and evaluation of soil functions at all scales
11:45–12:00
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ISMC2021-24
Laura Poggio, Niels Batjes, Luis de Sousa, Bas Kempen, Andre Kooiman, Gerard Heuvelink, David Rossiter, and Rik van den Bosch

Soils provide a variety of goods and services and are key natural resource, non-renewable on the time scale of a human life-span, to realise several UN-Sustainable-DevelopmentGoals, including zero hunger (SDG2), climate action (SDG13) and life on land (SDG15). Consistent soil information is required to underpin a large range of global assessments, such as soil and land degradation, sustainable land management, and environmental conservation. In this study, we present an application addressing the modelling of soil functions at global scaleusing erosivity risk and soil carbon sequestration potential as examples. We used SoilGridsv2.0, as set of soil property maps at 250m resolution, derived from a large set of standardized soil profile observations (WoSIS), an updated set of environmental covariates, and improved machine learning models. It provides global assessments of prediction uncertainty, quantified with 90% prediction interval, and considers an evaluation procedure that provides more realistic metrics of map accuracy. We used simplified models to derive soil functions (e.g. erosivity or carbon sequestration potential) from basic soil properties, meaningful for different pedo-climatic regions. We providan indication of areas of low/high risk of soil degradation to support sustainable soil management planning. The uncertainty limits of the input soil layers were used to provide a preliminary assessment of the uncertainty of the derived layers. The present modelling framework, using soil properties maps to derive soil functions, offers great flexibility and may be applied to a diverse set of models to generate soil information products tailored to specific applications. We highlight some of the challenges of assessing soil functions at global scale. 

How to cite: Poggio, L., Batjes, N., de Sousa, L., Kempen, B., Kooiman, A., Heuvelink, G., Rossiter, D., and van den Bosch, R.: Soil functions modelling at global scale using SoilGrids 2.0 , 3rd ISMC Conference ─ Advances in Modeling Soil Systems, online, 18–22 May 2021, ISMC2021-24, https://doi.org/10.5194/ismc2021-24, 2021.

12:00–12:15
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ISMC2021-80
Khadiza Begum, Raul Zornoza, Roberta Farina, Riitta Lemola, and Marianna Cerasuolo

Sustainable agriculture has been identified as key to achieve the 2030 Agenda for Sustainable Development Goal aiming at ending poverty and hunger, and addressing climate change, while maintaining natural resources. Soil organic carbon (SOC) sequestration is an important soil functions for the ecosystems service, and storing carbon (C) in soil by changing traditional management practices can represent an important step towards the development of more sustainable agricultural systems in Europe. Within the European project Diverfarming, the process-based ecosystem model ECOSSE was modified and evaluated in three long term experiments to assess the impact of crop diversification and agricultural management in SOC dynamics. ECOSSE was able to simulate SOC under Mediterranean regions in Spain and Italy after changing the minimum value of the decomposition rate modifying factor for soil moisture and allowing a higher soil moisture deficit. In Spain the addition of manure and cover crop in the diversified systems produced an increase in SOC compared to the conventional management (6% in simulations, 2% in measurement) in eight years. The effect of tillage on SOC stock in the Italian dry soil was also modelled, and a positive impact on SOC was predicted when no tillage is practised. Finally, ECOSSE was used to understand the impact of diversifications in Finland where different proportions of legumes and grass were considered in four-year crop rotations compared to conventional cereal rotations. Experiments and modelling showed that the loss of SOC in conventional cereal was compensated when grass was introduced in the rotations. A good agreement (RMSE <10%) and a non-significant bias were observed between model and data for all sites. The modified ECOSSE was able to predict SOC under diverse cropping systems and farming management in contrasting climatic regions. Further studies linking SOC simulations to indicator of sustainability across various European pedoclimatic regions is ongoing.

How to cite: Begum, K., Zornoza, R., Farina, R., Lemola, R., and Cerasuolo, M.: Modelling soil carbon under diverse cropping systems and farming management in contrasting climatic regions in Europe, 3rd ISMC Conference ─ Advances in Modeling Soil Systems, online, 18–22 May 2021, ISMC2021-80, https://doi.org/10.5194/ismc2021-80, 2021.

12:15–12:30
|
ISMC2021-68
Luke Mosley, Diederik Jacques, and Joel Rahman

Under changing climate conditions with expected higher risks on long periods of severe drought events, acid sulfate soils have a higher risk for acidification when exposed to oxygen under a falling water table. A regional or continental risk map for acidification under possible future climate scenarios is one of the tools for evaluating agricultural, economic and environmental impacts of acidification. The starting point is a simulation model with the relevant processes accounting for (i) the effect of changing meteorological boundary conditions on the water dynamics inside the soil and the ground water depth, (ii) diffusion of oxygen inside the soil profile, and (iii) kinetic dissolution of pyrite and geochemical alterations. The simulation tool HPx (Jacques et al., 2018) couples all these processes and enables to evaluation of different model structures. Numerical results were compared to an extreme drought event in the lower Murray River region, Murray-Darling Basin South Australia, between 2007 and 2010. A second step was the implementation of the mechanistic model in a spatial framework using python. As a proof of principle, we started with 5 x 5 km grid in areas with high probability of acid sulfate soils. Soil spatial data was pre-processed to determine model hydraulic parameters using pedotransfer functions. Climate and soil data were defined for each grid cell and formatted at run time for input into HPx. HPx simulations are controlled for the specific data for each grid cell. The final step is to perform the simulations on large spatial and temporal scales using supercomputing for which a linux-version of HP1 was developed. These developments open up new opportunities for coupled soil-climate modelling.

Jacques, D., Simunek, J., Mallants, D. and van Genuchten, M.T. (2018). JOURNAL OF HYDROLOGY AND HYDROMECHANICS 66, 211-226

How to cite: Mosley, L., Jacques, D., and Rahman, J.: Regional risk assessment of acid sulfate soil acidification under climate change based on mechanistic modelling of pyrite oxidation during prolonged drought events, 3rd ISMC Conference ─ Advances in Modeling Soil Systems, online, 18–22 May 2021, ISMC2021-68, https://doi.org/10.5194/ismc2021-68, 2021.

Interactive: Thu, 20 May, 12:30–14:00<

Chairpersons: Diederik Jacques, Ulrich Weller
Modelling soil contamination and transport of pollutant
P1
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ISMC2021-8
Chiara Petroselli, Katherine A. Williams, Arpan Ghosh, Daniel McKay Fletcher, Siul A. Ruiz, Tiago Gerheim Sousa Dias, Callum P. Scotson, and Tiina Roose

Phosphorus (P) is a limiting nutrient for crops and it is therefore highly managed in human activities such as agriculture. Not only the global phosphate rock reserves are going to be exhausted in a century, but P can also be lost from fields with the runoff ending up contaminating water bodies and causing eutrophication.

This study is aimed at investigating P release from a fertiliser granule at high spatial and temporal resolution to optimise fertilisation timing, match crop requirements and reduce runoff. Experimental data consist of time-resolved P concentration in the soil solution at three different depths and total P concentration profile determined via total soil digestion. We observed a rapid, single-pulse release of P from the fertiliser granule shortly after soil wetting (<2h). The pulse reaches the furthest probe (3 cm) within the same timeframe, then P concentration in the soil solution gradually decreases over the following 150 hours due to adsorption.

As the experimental data did not match the model-predicted P diffusion behaviour, a new modelling approach was used to reproduce the data. The model accounts for P diffusion and adsorption onto soil particles, resulting in the temporal evolution of P concentrations both in the soil solution and adsorbed onto soil particles. As the final total P concentration in soil reflects the initial P concentration profile in the soil solution, the model shows that adsorption onto soil particles happens faster than diffusion. Additionally, the model gives an estimate of diffusion, adsorption and desorption rates, as well as the maximum distance that P can travel from the source.

Combining high-resolution experiments with modelling provided a new insight into P release and diffusion from a fertiliser granule. The results can inform optimal fertilisation timings to improve crop yields while reducing P application rates and undesirable side effects such as eutrophication.

How to cite: Petroselli, C., Williams, K. A., Ghosh, A., McKay Fletcher, D., Ruiz, S. A., Gerheim Sousa Dias, T., Scotson, C. P., and Roose, T.: Spatiotemporal assessment of phosphorus release from a fertiliser granule and its diffusion into bulk soil: a combined experimental and modelling study, 3rd ISMC Conference ─ Advances in Modeling Soil Systems, online, 18–22 May 2021, ISMC2021-8, https://doi.org/10.5194/ismc2021-8, 2021.

P2
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ISMC2021-29
Liu Shuyi and Gao Bingbo

Source apportionment of soil heavy metals is an challenge and urgent work as the result of the rapid development of industrialization and urbanization. The common approach is multivariate statistical analysis, such as PCA and APCS/MLR, which infers only a single pattern of sources of heavy metals in entire study area. Due to complicated pathways and processes, patterns of pollution sources in a whole region may include two or more. Hence, we developed an analytical framework based on GWPCA to explore multiple patterns of sources of soil heavy metals on a regional scale. Xiangtan county, an important grain-producing area in China, was taken as a case study, which suffers the problem of heavy metal pollutions. Our results revealed the pollution situations of five soil heavy metals(Pb, Cd, As, Cr and Hg) in farmland soils and suggested that there exists various pollution patterns of these heavy metals in Xiangtan county. In each pattern, the structure of contamination sources is different. Our study also indicates that the analytical framework considering the spatial heterogeneity of pollution sources can help take more precise practices to solve this vital problem.

 

How to cite: Shuyi, L. and Bingbo, G.: Source apportionment of heavy metal pollution in farmland soils on a regional scale using geographically weighted PCA, 3rd ISMC Conference ─ Advances in Modeling Soil Systems, online, 18–22 May 2021, ISMC2021-29, https://doi.org/10.5194/ismc2021-29, 2021.

P3
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ISMC2021-67
Diederik Jacques, Jirka Simunek, Bertrand Leterme, Hans Meeussen, and Eric Laloy

Coupled reactive transport codes are indispensable tools for simulating the fate of solutes in porous media for both environmental and engineering applications. HP1 and HP2/3 are some of the most versatile tools for coupled processes of variably-saturated water flow, multicomponent solute transport, heat transfer, and equilibrium-kinetic chemical reaction networks (Jacques et al., 2018). To date, multiple extensions are included that significantly increase the flexibility of the HPx codes. In addition to the default PHREEQC geochemical solver, HPx provides alternatives for the geochemical step: the geochemical solver ORCHESTRA (Meeussen, 2003) or direct scripting. The ORCHESTRA solver is relatively small and efficient and comes with a large set of user definable adsorption models, including the NICA-Donnan model. The choice of the scripting language has been extended from the classical BASIC scripting language to the structured, prototype-based programming variant of BASIC and Python. The latter gives the possibility to include several libraries of Python immediately in the HPx based models. For example, machine learning techniques can replace computationally expensive geochemical calculations to speed up the calculations. The HPx code is also coupled to the MT3D-USGS code, the groundwater solute transport simulator for MODFLOW. Via the MODFLOW-HYDRUS1D integration, soil flow and transport processes can be integrated as an unsaturated zone component into MODFLOW and MT3D-USGS. The last change is the updated graphical user interface (GUI) for the geochemical model input and post-processing output, incorporated in the standard HYDRUS GUI. Besides, a stand-alone GUI version is available as an advanced interface for geochemical calculations with PHREEQC.

 

Jacques, D., J. Simunek, D. Mallants and M. T. van Genuchten (2018).  JOURNAL OF HYDROLOGY AND HYDROMECHANICS 66(2): 211-226.

Meeussen, J. C. L. (2003). Environmental Science & Technology 37(6): 1175-1182.

How to cite: Jacques, D., Simunek, J., Leterme, B., Meeussen, H., and Laloy, E.: Recent developments in the HPx-codes for coupled reactive transport in porous media, 3rd ISMC Conference ─ Advances in Modeling Soil Systems, online, 18–22 May 2021, ISMC2021-67, https://doi.org/10.5194/ismc2021-67, 2021.

P4
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ISMC2021-70
Bertrand Leterme, Diederik Jacques, and Cas Neyens

MTHP stands for Modflow Transport Hydrus PhreeqC and aims to provide an effective coupling tool for simulating reactive transport in the unsaturated and saturated zones. It builds upon the existing codes HYDRUS-1D (Šimůnek et al., 2013) / HP1 (Jacques et al., 2018), MODFLOW (Harbaugh, 2005), MT3D-USGS (Bedekar et al., 2016) and PhreeqC (Parkhurst and Appelo, 2013).

Two-way coupling between HYDRUS 1-D and MT3D-USGS has been implemented. HYDRUS-1D provides a mass flux of solute to the topmost saturated cell in MT3D-USGS. After one time step of solute transport has been solved in groundwater, the resulting solute concentration profile in the saturated zone is updated in HYDRUS. The code has been benchmarked against HYDRUS for a 1-D case but still requires to be adapted for 2 and 3-D cases when solute concentrations change in the unsaturated zone following lateral transport in groundwater.

Coupling PhreeqC to HYDRUS 1-D was already implemented within HP1. Simulating geochemical reactions in the aquifer required coupling MT3D-USGS to PhreeqC. This has been implemented by adding a new module MCP (MultiComponent Package) to the MT3D-USGS code using a similar versatile approach as in HPx. MCP has been successfully benchmarked against examples from the similar PHT3D code (Prommer and Post, 2010).

An application of this new module MCP for the simulation of redox plume development from a landfill, is presented. In this case study, reactive transport in the unsaturated zone is not included (i.e. only the MT3D-USGS – PhreeqC coupling is used), as the contamination source is suitably conceptualized to be at the water table surface. Kinetic degradation of dissolved organic carbon (DOC) in the presence of several electron acceptors is simulated. Observations of ion concentrations at different points in space and time are used to calibrate the MTHP simulations and investigate what is the acceptable level of process and parameter simplification.

This research is part of the RESPONSE project, funded by the Belgian Science Policy within the framework of the BRAIN-be programme (contract BR/165/A2/RESPONSE).

References

Bedekar, V., Morway, E.D., Langevin, C.D., and Tonkin, M., 2016, MT3D-USGS version 1: A U.S. Geological Survey release of MT3DMS updated with new and expanded transport capabilities for use with MODFLOW: U.S. Geological Survey Techniques and Methods 6-A53, 69 p.

Harbaugh, A.W., 2005, MODFLOW-2005, The U.S. Geological Survey Modular Ground-Water Model — the Ground-Water Flow Process, U.S. Geological Survey Techniques and Methods.

Jacques, D., Šimůnek, J., Mallants, D., and van Genuchten, M. T., 2018, The HPx software for multicomponent reactive transport during variably-saturated flow: Recent developments and applications. J. Hydrol. Hydromech, 66(2), 211-226.

Parkhurst, D.L. and Appelo, C.A.J., 2013, Description of input and examples for PHREEQC version 3--A computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations: U.S. Geological Survey Techniques and Methods, book 6, chap. A43, 497 p.

Prommer, H., and Post, V., 2010, PHT3D: A Reactive Multicomponent Transport Model for Saturated Porous Media, Version 2.10 User’s Manual.

Šimůnek, J., Šejna, M., Saito, H., Sakai, M., and van Genuchten, M. Th., 2013, The Hydrus-1D Software Package for Simulating the Movement of Water, Heat, and Multiple Solutes in Variably Saturated Media, Version 4.17, HYDRUS Software Series 3, Department of Environmental Sciences, University of California Riverside, Riverside, California, USA, 342 p. 

How to cite: Leterme, B., Jacques, D., and Neyens, C.: Coupling unsaturated and saturated zone reactive transport : Development and benchmarking of the MTHP tool, 3rd ISMC Conference ─ Advances in Modeling Soil Systems, online, 18–22 May 2021, ISMC2021-70, https://doi.org/10.5194/ismc2021-70, 2021.

Modelling and evaluation of soil functions at all scales
P5
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ISMC2021-53
Juan José Martín Sotoca, Antonio Saa-Requejo, Sergio Zubelzu, and Ana M. Tarquis

The study of the spatial characteristics of soil pore networks is essential to obtain different parameters that will be useful in developing simulation models for a range of physical, chemical, and biological processes in soils. Over the last decade, major technological advances in X-ray computed tomography (CT) have allowed for the investigation and reconstruction of natural porous soils at very fine scales. Delimiting the pore network (pore space) from the CT soil images applying image binarization methods is a critical step. Different binarization methods can result in different spatial distributions of pores influencing the connectivity metrics used in the models.

A combined global & local 2D segmentation method called “Combining Singularity-CA method” was successfully applied improving pore space detection. This method combines a local scaling method (Singularity-CA method) with a global one (Maximum Entropy method). The Singularity-CA method, based on fractal concepts, creates singularity maps, and the CA (Concentration Area) method is used to define local thresholds that can be applied to binarize CT soil images. Combining Singularity-CA (2D) method obtains better performance than the Singularity-CA and the Maximum Entropy method applied individually to the soil images.

A new three dimensional binarization method is presented in this work. It combines the 3D Singularity-CV (Concentration Volume) method and a global one to improve 3D pore space detection. Porosity and connectivity metrics of soil pore spaces are calculated and compared to other segmentation methods.

 

Acknowledgements:

The authors acknowledge the support from Project No. PGC2018-093854-B-I00 of the "Ministerio de Ciencia, Innovación y Universidades" of Spain and the funding from the "Comunidad de Madrid" (Spain), Structural Funds 2014-2020 512 (ERDF and ESF), through project AGRISOST-CM S2018/BAA-4330.

How to cite: Martín Sotoca, J. J., Saa-Requejo, A., Zubelzu, S., and Tarquis, A. M.: Using a combined global and local scaling 3D segmentation method to calculate pore connectivity measures in CT soil images, 3rd ISMC Conference ─ Advances in Modeling Soil Systems, online, 18–22 May 2021, ISMC2021-53, https://doi.org/10.5194/ismc2021-53, 2021.

P6
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ISMC2021-72
Ying Zhao

Preferential flow (PF) processes are controlled by subsurface structures with a hierarchical organization across scales, but there is a lack of multiscale model validation using field data. In this study, a comprehensive dataset collected in the forested Shale Hills catchment was used to test and validate PF simulations with the 2-dimensional HYDRUS-2D model at the hillslope scale. The simulations were also compared with the 1-dimensional results at the pedon scale (HYDRUS-1D) and 3-dimensional results at the catchment scale (HYDRUS-3D). There was a good agreement between the 1D simulations and soil moisture measurements, which were mainly affected by the vertical change in porosity/permeability with depth and precipitation characteristics. However, short-term fluctuations due to PF were poorly captured. Notably, 2D and 3D simulations, accounting for PF controlled by slope position and shallow fractured bedrock, provided better results than the 1D simulations. The dual-porosity or anisotropic model provided more accurate soil moisture predictions than the single-porosity or isotropic model due to the more realistic representation of local soil and fractured shale. Consequently, our study shows the importance of multi-dimensional model approaches and the need to adequately represent the bedrocks' soil structure and fractured nature for the PF simulation. The multi-dimensional modeling approaches can represent PF pathways to the first-order stream and shows the benefits of the 3D simulation with detailed information to identify the dominant hydrological process.

How to cite: Zhao, Y.: Simulating Preferential Flow by A Multi-dimensional Process-based HYDRUS Model, 3rd ISMC Conference ─ Advances in Modeling Soil Systems, online, 18–22 May 2021, ISMC2021-72, https://doi.org/10.5194/ismc2021-72, 2021.

P7
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ISMC2021-93
Haojie Liu, Franziska Tanneberger, and Bernd Lennartz

In Germany, more than 95% of peatlands have been drained for agriculture and forestry leading to water as well as carbon storage loss, soil degradation, and water eutrophication. Soil available water capacity (AWC) is one of the most important soil properties regulating the water balance and plays a pivotal role in plant growth. Compared with that of mineral substrates, our understanding of the impact of land management on water storage and the AWC of peat is limited. In this study, we aimed to deduce possible alterations of the AWC and water storage of peat following land drainage and rewetting. We analyzed a comprehensive database (674 measurements from boreal and temperate peatlands) to seek relations between bulk density (BD), field capacity, wilting point, and AWC. Bulk density was used as a proxy for soil degradation. The AWC increases with BD up to a value of 0.2 g cm−3; a further increase in BD leads to a considerable decrease in AWC. The derived function between BD and AWC enables us to upscale the AWC to a regional scale. The average AWC of agricultural peatlands in Germany is estimated to be 37 ± 11 vol% (mean ± standard deviation). Currently, the water storage of agricultural peatlands in Germany is approximately 1.0 m3 per m2. We estimated that water storage in the natural peatlands in Germany was 33.8 km3 prior to drainage. Converting natural peatlands into agricultural land resulted in a water storage loss of approximately 18.6 km3. Several decades of peatland rewetting have a limited effect on water storage recovery due to a substantial loss of peat thickness because of former drainage and a low porosity of degraded peat.

How to cite: Liu, H., Tanneberger, F., and Lennartz, B.: Impact of Land Management on Available Water Capacity and Water Storage of Peat, 3rd ISMC Conference ─ Advances in Modeling Soil Systems, online, 18–22 May 2021, ISMC2021-93, https://doi.org/10.5194/ismc2021-93, 2021.

P8
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ISMC2021-46
Ana R. Oliveira, Ana Horta, and Tiago Ramos

Modelling of soil physical, chemical, and biological processes is critical to improve the understanding of soil functions, the effect of agricultural practices on soil degradation, and appropriate soil management strategies. However, the use of such tools at the regional scale is largely limited by the lack of accurate mapping of soil texture and soil hydraulic properties (SHP). To overcome this limitation, SHP digital maps were obtained using two modelling approaches. One used a national harmonized soil texture database and geostatistical simulation to create soil texture maps which were further used as input data to derive SHP maps using local pedotransfer functions (PTFs). The other approach used SHP maps produced by Tóth et al (2017) using soil texture from the product SoilsGrids (Hengl et al, 2017). The SHP maps from both approaches were produced at two spatial resolutions: 250 m and 1000 m. This study aims to evaluate the usefulness of such SHP maps to simulate soil water dynamics and biomass growth at the regional scale using the MOHID-Land model. This model describes the movement of water in the porous medium based on mass and momentum conservation equations that are computed in a 3D grid domain using a finite volume approach. Crop development is simulated using a modified version of the EPIC model. The SHP maps produced using the two modelling approaches and considering two spatial resolutions (250 and 1000 m) were used as inputs for the hydraulic characteristics of soils. Simulations were compared for an irrigation area (Roxo Irrigation District), located in southern Portugal. Results revealed the differences in the components of the soil water balance, with soil inputs from local data being able to better portray landscape heterogeneity.

How to cite: Oliveira, A. R., Horta, A., and Ramos, T.: Using digital soil hydraulic maps to simulate water balance at the regional scale (southern Portugal) - impact of spatial resolution and modelling approach, 3rd ISMC Conference ─ Advances in Modeling Soil Systems, online, 18–22 May 2021, ISMC2021-46, https://doi.org/10.5194/ismc2021-46, 2021.

P9
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ISMC2021-100
Andis Kalvans

It is hypothesized that northern nemoral forests on hydromorphic soils in lowland settings can enter a feedback loop were enhanced evapotranspiration led to better soil aeration enhancing root water uptake and further increase of evapotranspiration. Opposite feedback could be possible as well – poor soil aeration due to water saturation hinders the root water uptake, resulting in overall decreased evapotranspiration and preservation of waterlogged state of the soil. The feasibility of the feedback loop is explored by a Hydrus-1D simulation using artificial climate forcing. It is suggested that wet or dry years can shift the vegetation-soil water system from wet to dry state and back. The research is supported by project No. 1.1.1.2/VIAA/3/19/524.

How to cite: Kalvans, A.: Simulation of vegetation-soil water feedback in nemoral forests on hydromorphic soils with Hydrus-1D, 3rd ISMC Conference ─ Advances in Modeling Soil Systems, online, 18–22 May 2021, ISMC2021-100, https://doi.org/10.5194/ismc2021-100, 2021.