Impact of Nitrate Fluxes to Water from Seasonally Frozen Soils under Climate Warming
Lead Research Organisation:
University of Sheffield
Department Name: Civil and Structural Engineering
Abstract
Present climate models predict an increase in the average air temperature of 1.5C and average soil temperature within 8m soil depth of 1.2-3.3C, by the end of this century. Increasing temperatures during winter can have a significant impact on soil biogeochemical cycles, increasing the production of nitrate in the soil. It is also likely to increase the number of snow-free days, reduce soil freezing depth and increase the frequency of freeze-thaw cycles in soil. Due to the lack of sufficient vegetation or biomass to utilize the excess soil nitrate during winter, nitrate may move in soil moisture towards the soil surface or migrate to groundwater, influenced by the ambient temperature gradient. The transport of excess nitrate in this way can lead to both surface water and groundwater contamination. This research will study the impacts of rising winter temperatures on the soil nitrogen cycle, the direction of movement of soil nitrate produced during winter, and quantify the amount of soil nitrate produced for a given temperature regime. The research will use soil column experiments to study the production of nitrate under different soil freezing depths and soil temperature variations. The experimental results will be interpreted using numerical models and machine learning algorithms to develop transfer functions that describe the production and release of nitrate from soil under various conditions. The outcomes of this study will help scientists understand the effects of climate warming on the release of nitrate from soil to water resources and develop best management practices to mitigate this impact.
Organisations
Publications
Sahoo M
(2025)
A laboratory-scale physical model for freeze-thaw studies in soil columns under simulated climate change conditions.
in Environmental science and pollution research international
| Description | The research is ongoing and the experiments will be completed, with an update on the results and key findings from these. The main achievements to date are the development and experimental validation of a novel laboratory-scale physical model which provides the foundation for the column experiments that assess soil nitrogen dynamics under different freeze-thaw cycle scenarios. The physical model is designed to reproduce conditions that develop within soil profiles at field-scale due to freeze thaw cycles and to characterise the resultant biogeochemical processes within the soil that release nitrogen compounds to water bodies. The experimental design can (i) induce cyclical freezing of soil down to desirable and realistic depths, (ii) maintain vertical temperature gradients, (iii) ensure the column remains unfrozen below the freezing interface for pore water sampling, and (iv) enable reproducible and precise low-volume sampling of the soil pore water chemistry. The rate of freezing is suitable for quick freeze-thaw cycles (0.19 C/min), thereby enabling a wide range of temperature-cycling scenarios to be considered. A paper describing this research methodology has been published and can be downloaded from https://doi.org/10.1007/s11356-025-36053-8. The publication describes the design, construction and experimental testing of the laboratory-scale physical model used to undertake the column studies. It includes detailed discussion of the experimental apparatus and its operation, with example test data used to verify the performance under conditions which simulate real world scenarios. |
| Exploitation Route | The laboratory-scale physical model developed in this research can be further developed to examine the transport and behaviour of a wide range of chemicals in variably-saturated soil, and soil moisture status for different freeze-thaw regimes under simulated climate change scenarios. This versatile and flexible experimental testing platform therefore offers the opportunity to explore the impact of climate change-induced warming on other soil processes that affect nutrient or contaminant cycling. The outcomes of this research will help environmental managers and regulatory bodies understand the potential impact of climate warming on nitrogen releases from soil to water bodies, via seasonal freeze-thaw processes, and inform the development of nutrient management strategies for catchments. More generally, the experimental design can be used in many other studies where precise control of soil temperature and moisture saturation in vertical profile under freeze-thaw cycles is required. |
| Sectors | Agriculture Food and Drink Environment |