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<p>Extending unfrozen water availability is critical for stress-tolerant bioremediation of contaminated soils in cold climates. This study employs the soil-freezing characteristic curves (SFCCs) of biostimulated, hydrocarbon-contaminated cold-climate soils to efficiently address the coupled effects of unfrozen water retention and freezing soil temperature on sub-zero soil respiration activity. Freezing-induced soil respiration experiments were conducted under the site-relevant freezing regime, programmed from 4 to − 10 °C at a seasonal soil-freezing rate of − 1 °C/day. The effects of unfrozen water retention on extending soil respiration activity emerged at the onset of soil-freezing. The unfrozen water effect became significant below 0 °C (correlation <i>r</i> = 0.83–0.94) and comparable to the temperature effect (correlation <i>r</i> = 0.82–0.90), successfully demonstrating the coupled effects on sub-zero respiration activity. Soil CO<sub>2</sub> respiration modelling based on the temperature dependency only (Arrhenius and Q<sub>10</sub> models) did not accurately describe sub-zero respiration activity associated with increased unfrozen water retention in treated contaminated soils. The shifted SFCCs of the treated soils, expressed as a function of soil temperature (<i>T</i>) and unfrozen water content (<i>θ</i>), served as a key framework for efficiently developing the sub-zero respiration model (SFCC-RESP). The developed SFCC-RESP model closely approximated the changes in soil respiration rates influenced by <i>T</i> and <i>θ</i> in the treated soils (<i>R</i><sup>2</sup> = 0.94–0.98) and described the abrupt decrease and subsequent stabilization in CO<sub>2</sub> production during the transition to the deeply frozen soil phase. The SFCC-RESP model integrated with soil thermal models (TEMP/W) can be used to produce spatial distributions of <i>T</i>, <i>θ</i>, and CO<sub>2</sub> production in the treated soil matrix, providing a tool to approximate the abundance of unfrozen habitable niches when developing cold-tolerant bioremediation strategies.</p> Graphical abstract <p></p>

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Sub-zero soil CO2 respiration in biostimulated hydrocarbon-contaminated cold-climate soil can be linked to the soil-freezing characteristic curve

  • 期刊论文

  • 发表日期：

    2025年1月2日

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  • Tasnim Nayeema,
  • Aslan Hwanhwi Lee,
  • Amy Richter,
  • Kelvin Tsun Wai Ng,
  • Wonjae Chang

摘要

Extending unfrozen water availability is critical for stress-tolerant bioremediation of contaminated soils in cold climates. This study employs the soil-freezing characteristic curves (SFCCs) of biostimulated, hydrocarbon-contaminated cold-climate soils to efficiently address the coupled effects of unfrozen water retention and freezing soil temperature on sub-zero soil respiration activity. Freezing-induced soil respiration experiments were conducted under the site-relevant freezing regime, programmed from 4 to − 10 °C at a seasonal soil-freezing rate of − 1 °C/day. The effects of unfrozen water retention on extending soil respiration activity emerged at the onset of soil-freezing. The unfrozen water effect became significant below 0 °C (correlation r = 0.83–0.94) and comparable to the temperature effect (correlation r = 0.82–0.90), successfully demonstrating the coupled effects on sub-zero respiration activity. Soil CO2 respiration modelling based on the temperature dependency only (Arrhenius and Q10 models) did not accurately describe sub-zero respiration activity associated with increased unfrozen water retention in treated contaminated soils. The shifted SFCCs of the treated soils, expressed as a function of soil temperature (T) and unfrozen water content (θ), served as a key framework for efficiently developing the sub-zero respiration model (SFCC-RESP). The developed SFCC-RESP model closely approximated the changes in soil respiration rates influenced by T and θ in the treated soils (R2 = 0.94–0.98) and described the abrupt decrease and subsequent stabilization in CO2 production during the transition to the deeply frozen soil phase. The SFCC-RESP model integrated with soil thermal models (TEMP/W) can be used to produce spatial distributions of T, θ, and CO2 production in the treated soil matrix, providing a tool to approximate the abundance of unfrozen habitable niches when developing cold-tolerant bioremediation strategies.

Graphical abstract