Pedophysics: an open-source python package for soil geophysics

This study introduces Pedophysics, an open-source Python package designed to facilitate solutions for users who work in the field of soil assessment using near-surface geophysical electromagnetic techniques. At the core of this software is the ability to translate geophysical data into specific soil properties (and vice-versa) using pedophysical models (PM). Pedophysical modelling techniques offer valuable insights into various realms including precision agriculture, soil health, resource prospecting, nutrient and land management, hydrogeology, and heritage conservation. In developing a tool for pedophysical modelling, some challenges emerged: selecting suitable PMs from the extensive literature, adapting these to specific conditions, and ensuring adequate data availability. While addressing these, we designed an automated workflow that implements robust PMs (selected after a throughout review), apply different modelling approaches based on soil characteristics and targeted properties, and employs pedotransfer functions and assumptions to integrate missing soil data into PMs. The capabilities of Pedophysics extend to handling complex scenarios such as fusing data from different instruments, incorporating continuous monitoring measurements, and soil calibration data. With these solutions, Pedophysics automates the process of deriving targeted soil and geophysical properties with state-of-art accuracy. Hereby, users can rely on Pedophysics to implement specific knowledge about pedophysical modeling. The software promotes global access to advanced soil geophysical solutions by being open-source and encouraging community contributions. Pedophysics is written in pure Python and has minimal dependencies. It can be easily installed from the Python Package Index (PyPI).Comment: Submitted to a Q1 journal, awaiting review and further publicatio

Developing a geophysical framework for Neolithic land-use studies: in situ monitoring and forward modelling of electrical properties at "Valther-Tweeling" (NL)

Boosting Neolithic land-use studies in the Low Countries requires optimal geophysical survey. Hereby, forward modeling such subtle soil features in a sandy soil could support survey design. The models are parametrized through soil sample analyses and in situ data collection over a feature. Supplemented by long term in situ monitoring, these results reveal variable detectability. This approach enables a quantitative approach for geophysical survey design

Combining teaching and research: a BIP on geophysical and archaeological prospection of North Frisian medieval settlement patterns

We performed a research-oriented EU Erasmus+ Blended Intensive Program (BIP) with participants from four countries focused on North Frisian terp settlements from Roman Iron Age and medieval times. We show that the complex terp structure and environment can be efficiently prospected using combined magnetic and EMI mapping, and seismic and geoelectric profiling and drilling. We found evidence of multiple terp phases and a harbor at the Roman Iron Age terp of Tofting. In contrast, the medieval terp of Stolthusen is more simply constructed, probably uni-phase. The BIP proved to be a suitable tool for high-level hands-on education adding value to the research conducted in on-going projects

Pedophysics : a python package for soil geophysics

Near surface geophysical electromagnetic techniques are proven tools to support ecosystem services such as agriculture, soil remediation, nutrient management, and heritage conservation. Key influencing geophysical properties are electrical conductivity (σ, or resistivity (ρ)), dielectric permittivity () or magnetic susceptibility (μ), that are targeted to model soil properties and state variables such as texture, bulk density, cation exchange capacity (CEC) or water content. To translate geophysical properties into quantitative information on the targeted soil properties, relationships between these have to be considered in appropriate models. These so-called pedophysical models can then be integrated into interpretation schemes (e.g., after inversion, or through incorporating this into forward modelling procedures). This modelling step, translating geophysical properties into soil properties (and vice versa), thus constitutes a key aspect of near surface exploration. While hundreds of pedophysical models exist to perform this task, these often depend on many properties and parameters defined within a specific range e.g., electromagnetic frequency, texture, and salinity; impeding applications to cases where information about the studied soil is scarce. Therefore, selecting an appropriate pedophysical model for a given scenario is often a very complex task. To facilitate solutions for pedophysical modelling we present pedophysics, an open source python package for soil geophysical characterization. The package implements up-to-date models from the literature and, based on the user’s needs, automatically provides an optimal solution given a set of input parameters and the targeted output. First, a virtual soil is defined by inputting any of its available properties. This soil can be defined in discrete states to simulate the evolution of its properties over time. Secondly, a module (predict) is called to predict the target property of interest. Following this workflow, for example, a soil with a given texture and changing water content could be defined to obtain its or σ at a predefined frequency, or, inversely, its water content could be predicted based on changing σ. However, as soil properties required as input parameters for pedophysical models are often unknown, it can, in such cases, be impossible to obtain a viable prediction outcome. The pedophysics package accounts for such limitations by implementing pedotransfer functions, that allow obtaining the missing properties from the available ones. For example, if CEC is unknown, it is determined based on soil texture and a location. In summary, the package synthesizes specific pedophysical modeling knowledge. Time-varying properties can be calculated in a straightforward way, and, through the integration of pedotransfer functions, target properties can be predicted with a minimum of information about the studied soil. Thus, by translating known properties to targeted ones, pedophysics is contributing to improve interpretability of near surface modeling schemes; enhancing soil electromagnetic geophysical exploration techniques in ecosystem services applications

Soil dielectric permittivity modelling for 50 MHz instrumentation

Near surface electromagnetic geophysical techniques are proven tools to support soil ecosystem services and soil exploration. Such geophysical techniques provide electromagnetic properties that are useful to characterize the studied soil. The link between relevant soil characteristics and geophysical properties, such as dielectric permittivity (ε), is commonly expressed by pedophysical models. However, some weaknesses remain in their application, such as the requirement of parameters that are difficult to measure or calculate. Therefore, these parameters are frequently fixed, but this oversimplifies the complexity of the investigated soils. Moreover, the validity of ε pedophysical models in the frequency range of operating soil moisture sensors (normally < 100 MHz) remains poorly investigated.In this study, the accuracy and adaptability of ε pedophysical models at different electromagnetic frequency ranges was tested and improved using newly collected laboratory and field data. Such data was collected on soils over a wide range of textures, physical and chemical properties.To achieve this, we review the measurement methods and characteristics of ε pedophysical models, soil phases and geometric parameters. Subsequently, we show how geometric parameters can explain the dependance of soil texture on ε by implementing pedotransfer functions. Then, drawing on a broad experimental basis of common soil types in Europe, we develop novel ε pedophysical models at 50 MHz. These models are not only easy to evaluate but also capture most of the soil’s complexity. Additionally, these new ε pedophysical models eliminate the need for calibration data due to the introduction of novel pedotransfer functions based on soil cation exchange capacity. An extensive model test shows an unprecedented decrease in the RMSE of the newly proposed models of up to 412%.In conclusion, despite it is unlikely to characterize soil structure, bulk density, or temperature at 50 MHz, these updated PPMs are useful for highly accurate water content and ε predictions, in both laboratory and field conditions, without the need for calibration data. As the developed modelling procedures are valid for a wide range of electromagnetic frequencies, these can be applied to soil exploration with TDR and GPR instrumentation.For reproducibility, all collected soil data are provided, alongside open-source Python code that contains the presented modelling procedures

A theoretical approach to near surface pedophysical permittivity models

Despite well-established knowledge about the relationships between the electrical conductivity or relative permittivity of rocks, ambiguity remains as to how these relationships and knowledge can be transferred to soils. In general, there are three problems that hinder the robust application of available pedophysical models. First, these models often rely on soil properties and attributes that cannot be directly quantified in the laboratory or in the field, such as pore connectivity and depolarisation factor, which reduces their applicability. Secondly, the introduction of tuning parameters (such as the cementation exponent and Roth's exponent) tends to reduce the theoretical significance of the physical process in question. Finally, oversimplifying pedophysical relationships by considering only one soil attribute (such as moisture content) effectively ignores the effect of other relevant properties (clay content or bulk density). Here we present a theoretical approach that shows how to sort out this issues while both fitting parameters and anisotropy indicators can be derived from soil properties that are easy to measure in the laboratory

Working the land, searching the soil : developing a geophysical framework for Neolithic land-use studies : project introduction, -methodology, and preliminary results at ‘Valther Tweeling’

We are introducing the project ‘Working the land, searching the soil. A geophysical framework for diachronic land-use studies’ and present the first research results. By combining geophysical measurements with soil sampling and analysis on profiles of natural soils and archaeological features with long-term geophysical monitoring by sensors in the profile face, we aim to optimize the geophysical prospecting of subtly contrasting Neolithic (and other) soil features. The first results of the fieldwork on the cut of a Neolithic pit at ‘Valther Tweeling’ show the challenging conditions to register geophysical contrasts between soil traces and natural soils. The temporal changes in the electrical soil properties of the feature fill and the natural soil profile indicate that these react differently to precipitation, however. Therefore, subject to further data collection and analysis, an optimal contrast could be sought