Universal spatial correlation functions for describing and reconstructing soil microstructure

PLoS One. 2015 May 26;10(5):e0126515. doi: 10.1371/journal.pone.0126515. eCollection 2015.

Abstract

Structural features of porous materials such as soil define the majority of its physical properties, including water infiltration and redistribution, multi-phase flow (e.g. simultaneous water/air flow, or gas exchange between biologically active soil root zone and atmosphere) and solute transport. To characterize soil microstructure, conventional soil science uses such metrics as pore size and pore-size distributions and thin section-derived morphological indicators. However, these descriptors provide only limited amount of information about the complex arrangement of soil structure and have limited capability to reconstruct structural features or predict physical properties. We introduce three different spatial correlation functions as a comprehensive tool to characterize soil microstructure: 1) two-point probability functions, 2) linear functions, and 3) two-point cluster functions. This novel approach was tested on thin-sections (2.21×2.21 cm2) representing eight soils with different pore space configurations. The two-point probability and linear correlation functions were subsequently used as a part of simulated annealing optimization procedures to reconstruct soil structure. Comparison of original and reconstructed images was based on morphological characteristics, cluster correlation functions, total number of pores and pore-size distribution. Results showed excellent agreement for soils with isolated pores, but relatively poor correspondence for soils exhibiting dual-porosity features (i.e. superposition of pores and micro-cracks). Insufficient information content in the correlation function sets used for reconstruction may have contributed to the observed discrepancies. Improved reconstructions may be obtained by adding cluster and other correlation functions into reconstruction sets. Correlation functions and the associated stochastic reconstruction algorithms introduced here are universally applicable in soil science, such as for soil classification, pore-scale modelling of soil properties, soil degradation monitoring, and description of spatial dynamics of soil microbial activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Algorithms*
  • Cluster Analysis
  • Image Processing, Computer-Assisted*
  • Models, Theoretical
  • Porosity
  • Soil / chemistry*

Substances

  • Soil

Grants and funding

1) Russian Scientific Foundation (http://www.rscf.ru/), grant number 14-17-00658 (developing optimized computation of diagonal correlation functions), MVK, KMG. 2) Russian Foundation for Basic Reserach (www.rfbr.ru), grants 12-05-01130-а, 13-04-00409-a, 12-04-32264_мол_a and 13-05-01176-a (soil tin-sections, expendables), MVK, EBS. AIR Technology provided support in the form of salaries for author Marina V. Karsanina, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.