Freeze-thaw cycles in seasonally frozen soil affect the boundary conditions of aqueducts with pile foundations, consequently impacting their seismic performance. To explore the damage characteristics and seismic behaviour of aqueduct bent frames in such regions, a custom testing apparatus with an integrated cooling system was developed. Two 1/15 scale models of reinforced concrete aqueduct bent frames with pile foundations were constructed and subjected to pseudo-static testing under both unfrozen and frozen soil conditions. The findings revealed that ground soil freezing has minimal impact on the ultimate bearing capacity and energy dissipation of the bent frame-pile-soil system, but significantly enhances its initial stiffness. Additionally, the frozen soil layer exerts a stronger embedding effect on the pile cap, ensuring the stability of the pile foundation during earthquakes. However, under large seismic loads, aqueduct bent frames experience greater damage and residual deformation in frozen soil compared to unfrozen soil conditions. Therefore, the presence of a seasonally frozen soil layer somewhat compromises the seismic performance of aqueduct bent frames. Subsequently, a finite element model considering pile-soil interaction (PSI) and frozen soil hydro-thermal effects was developed for aqueduct bent frames and validated against experimental results. This provides an effective method for predicting their seismic behaviors in seasonally frozen soil regions. Furthermore, based on the seismic damage characteristics of aqueduct bent frame with pile foundations observed in pseudo-static tests, a novel selfadaptive aqueduct bent frame system was designed to mitigate the adverse effects of seasonally frozen soil layer on seismic performance. This system is rooted in the principle of balancing resistance with adaptability, rather than solely depending on resistance. The seismic performance of this innovative system was then discussed, providing valuable insights for future seismic design of reinforced concrete aqueduct bent frames with pile foundations in seasonally frozen soil regions.

Peat soil is a significant global carbon storage pool, accounting for one-third of the global soil carbon pool. Its greenhouse gas emissions have a significant impact on climate change. Seasonal freeze-thaw cycles are common natural phenomena in high-latitude and high-altitude regions. They significantly affect the mineralization of soil organic carbon and greenhouse gas emissions by altering the physical structure, moisture conditions, and microbial communities of the soil. In this study, through the construction of an indoor simulation experiment of the typical freeze-thaw cycle models in spring and autumn in the Greater Xing'an Range region of China and the Jinchuan peatland of Jilin Longwan National Nature Reserve, the physicochemical properties, greenhouse gas emission fluxes, microbial community structure characteristics, and key metabolic pathways of peat soils in permafrost and seasonally frozen ground areas were determined. The characteristics of greenhouse gas emissions and their influencing mechanisms for peat soil in northern regions under different freeze-thaw conditions were explored. The research found that the freeze-thaw cycle significantly changed the chemical properties of peat soil and significantly affected the emission rates of CO2, CH4, and N2O. It also clarified the interaction relationship between soil's physicochemical properties (such as dissolved organic carbon (DOC), dissolved organic nitrogen (DON), ammonium nitrogen (NH4+), soil organic carbon (SOC), etc.) and the structure and metabolic function of microbial communities. It is of great significance for accurately assessing the role of peatlands in the global carbon cycle and formulating effective ecological protection and management strategies.

The seasonal freeze-thaw cycle of frozen soil regulates soil hydrothermal processes and serves as a crucial indicator of climate change in high-latitude cold regions. Monitoring the dynamic evolution of frozen soil structure and composition is essential for infrastructure development, soil conservation and carbon storage regulation. Compared to in-situ borehole measurements and remote sensing, near-surface geophysical methods offer spatially resolved insights into freeze-thaw processes at different depths. In this study, we applied electrical resistivity tomography and ambient noise seismic monitoring to investigate seasonal freeze-thaw cycles at a frozen soil test site in Northeast China. Geophysical data collected over a complete freeze-thaw cycle reveal the coupling between soil structure and hydrothermal properties, with strong consistency observed between physical parameters and hydrological information. Resistivity variations correlate with temperature, water content, and solute concentration across different freeze-thaw stages. Seismic relative velocity changes (dv/v) and surface wave phase velocity changes (dc/c) were negatively correlated with accumulated temperature and groundwater levels, reflecting soil pore freezing and the hydrothermal state of the deep subsurface environment. Meanwhile, the measured data verify that dc/c offers higher spatiotemporal resolution than dv/v. Sensitivity analysis indicate that resistivity is more responsive to shallow thermal exchange, while seismic velocity changes are more sensitive to deep hydrological variations. Integrating pore geometry and water-ice phase mechanisms, we construct a freeze-thaw evolution model for seasonally frozen soil based on combined hydrological and geophysical data. The results validate the effectiveness of geophysical methods for detecting and monitoring frozen soil, and provide technical support for quantifying phase transition mechanisms in freeze-thaw processes.

This study investigates the effects of aerosol-radiation interactions on subseasonal prediction using the Unified Forecast System, which includes atmosphere, ocean, sea ice, and wave components, coupled with an aerosol module. The aerosol module is from the current NOAA operational GEFSv12-Aerosols model, which is based on the WRF-Chem GOCART with updates to the dust scheme and the biomass burning plume rise module. It simulates five aerosol species: sulfate, dust, black carbon, organic carbon, and sea salt. The modeled aerosol optical depth (AOD) is compared to MERRA-2 reanalysis, MODIS satellite retrievals, and ATom aircraft measurements. Despite biases primarily in dust and sea salt, the AOD shows good agreement globally. The simulated radiative forcing (RF) at the top of the atmosphere (TOA) from the total aerosols is approximately -2.6 W/m2 or -16 W/m2 per unit AOD globally. In subsequent simulations, the prognostic aerosol module is replaced with climatological aerosol concentrations derived from the preceding experiments. While regional differences in RF at TOA between these two experiments are noticeable in specific events, the multi-year subseasonal simulations reveal consistent patterns in RF at TOA, surface temperature, geopotential height at 500 hPa, and precipitation. These results suggest that given the current capacities of aerosol modeling, adopting a climatology of aerosol concentrations as a cost-effective alternative to a complex aerosol module may be a practical approach for subseasonal applications.

Vast deserts and sandy lands in the mid-latitudes cover an area of 17.64 x 106 km2, with 6.98 x 106 km2 experiencing seasonal frozen soil (SFG). Freeze-thaw cycles of SFG significantly influence local surface processes in deserts, impacting meteorological disasters such as infrastructure failures and sandstorms. This study investigates the freeze-thaw dynamics of SFG in crescent dunes from three deserts in northern China: the Tengger Desert, Mu Us Sandy Land, and Ulan Buh Desert, over the period from 2019 to 2024.Freezing occurs from November to January, followed by thawing from January to March. The thawing rate (2.72 cm/day) was 1.8 times higher than the freezing rate (1.48 cm/day). The maximum seasonal freezing depth (MSFD) exceeded 0.80 mat all dune slopes, with depths surpassing 1.10 mat the leeward slope and lower slope positions. Soil moisture content, ranging from 1 % to 1.6 %, is critical for freezing, and this threshold varies depending on the dune's mechanical composition. The hardness of frozen desert soil is primarily controlled by moisture, along with temperature and particle size.Temperature initiates freezing, while moisture and particle size control the resulting hardness.These findings shed light on the seasonal freeze-thaw processes in desert soils and have practical implications for agricultural management, engineering design, and environmental hazard mitigation in arid regions.

Background: With growing concern during the COVID-19 pandemic, indoor environmental quality has received significant attention. Radon, a radioactive gas produced from the decay of radium found in soil, rocks, and building materials, can accumulate indoors, posing serious health risks such as lung cancer. University environments, where occupants spend significant time indoors, are particularly susceptible to prolonged radon exposure. Method: This study focused on the estimation of indoor radon concentrations from multiple university buildings in Shanghai. A field investigation was conducted between June 2020 and August 2022. Continuous radon measurements were conducted in the dormitories and classroom buildings. Environmental factors include indoor air temperature and relative humidity. Results: Radon concentrations were influenced by season, floor level, and measurement period, with the highest concentrations recorded during summer and on lower floors due to reduced ventilation. The mean radon concentration in dormitories was 14.8 +/- 9.2 Bq/m3, and in classrooms 12.6 +/- 6.7 Bq/m3, both below national safety limits and lower than those in the pre-pandemic era. Seasonal effect, floor level, and time of measurement were the significant factors for indoor radon concentrations. Conclusion: This study has identified the main factors that affect indoor radon concentration in university campus. The radon concentrations at the lower floor levels remain the highest in the building. The results provide evidence for conducting refined radon monitoring and risk assessment in campus environment, especially during the summer.

Late frost is a major challenge to stone and pome fruit production in northern New Mexico. In this study, we planted three cultivars of peach (Prunus persica L.)-Challenger, China Pearl, and Contender-on three rootstocks-Nemaguard (P. persica), GF677 (P. persica 3 P. dulcis), and RootpacVR R (P. cerasifera 3 P. dulcis)-in a high tunnel outfitted with thermostat-controlled propane heaters and fans to assess the feasibility of frost protection during bloom and fruitlet stage. In 2017, we planted the trees on Nemaguard rootstocks at 4 3 10 ft spacing and trained them in an open vase system. Due to severe leaf chlorosis, two rows of trees were removed and tissue cultured GF677 and RootpacVR R were planted in May 2018 and budded onsite in Aug 2018. In 2021, we began securing the sidewalls and the doors of the high tunnel and setting up heaters, which we continued until 2023. In 2021, it appeared that buds were damaged by extreme cold sometime in February, before the high tunnel was closed. In 2022 and 2023, the high tunnel system was sufficient to protect blooms and fruitlets from frost and yielded an average of 15.8 kg/tree in 2022 and 12.3 kg/tree in 2023. There was no significant difference between the cultivars in either year. There were, however, significant differences between rootstocks in 2022, with Nemaguard averaging 24.3 kg/tree across cultivars, whereas GF677 and RootpacVR R averaged 11.2 and 11.8 kg/tree, respectively, across cultivars because trees on Nemaguard rootstock were planted almost 2 years earlier than the rest. Comparing peach rootstocks, GF677 and RootpacVR R were more suitable for high pH soil in New Mexico than Nemaguard. Cherry had limited fruit set during this study. In 2022 and 2023, we observed blackened pistils and deformed flowers without petals, stamens, and pistils. More research is needed for cherry high tunnel production in northern New Mexico.

Geohazards such as slope failures and retaining wall collapses have been observed during thawing season, typically in early spring. These geohazards are often attributed to changes in the engineering properties of soil through changes in soil phase with moisture condition. This study investigates the impact of freezing and thawing on soil stiffness by addressing shear wave velocity (Vs) and compressional wave velocity (Vp). An experimental testing program with a temperature control system for freezing and thawing was prepared, and a series of bender and piezo disk element tests were conducted. The changes in Vs and Vp were evaluated across different phases: unfrozen to frozen; frozen to thawed; and unfrozen to thawed. Results indicated different patterns of changes in Vs and Vp during these transitions. Vs showed an 8% to 19% decrease for fully saturated soil after thawing, suggesting higher vulnerability to shear failure-related geohazards in thawing condition. Vp showed no notable change after thawing compared to initial unfrozen condition. Based on the test results in this study, correlation models for Vs and Vp with changes in soil phase of unfrozen, frozen, and thawed conditions were established. From computed tomography (CT) image analysis, it was shown that the decrease in Vs was attributed to changes in bulk volume and microscopic soil structure.

This study presents experimental results from scale model tests on laterally loaded bridge pile foundations in soils subjected to seasonal freezing. A refined finite-element model (FEM) was established and calibrated based on data obtained from the experiments. Furthermore, the model was utilized to investigate the impact of soil scouring depth on the lateral behavior of bridge pile foundations embedded in seasonally frozen soils. The findings indicate that soil freezing significantly enhances the lateral bearing capacity of the pile-soil interaction (PSI) system while reducing lateral deflection of the pile foundation. However, soil freezing results in increased damage to the pile foundation and upward movement of the plastic zone toward the ground surface. Under unfrozen conditions, significant plastic deformations occur on the ground surface and even inside the piles due to the extrusion effect. Additionally, increasing soil scouring depth significantly reduces the lateral bearing capacity of the PSI system while also increasing lateral deflection of the pile foundation for a given load level. Notably, when the scouring depth exceeds 2 m in unfrozen soils, the entire pile experiences obvious deformation and inclination, exhibiting a short-pile behavior that negatively affects the lateral stability of the pile under lateral loads.

The damage caused by soil-borne diseases in Cunninghamia lanceolata (Lamb.) Hook (Cupressaceae), commonly called the Chinese fir, has become increasingly severe in China in recent years. Due to the strong seasonal dependence of the occurrence and severity of these diseases, the ecological processes influencing changes in the composition and function of the plant microbiome during different seasons of pathogen infection have been rarely studied. This study compared the seasonal variations in soil physicochemical properties between the rhizosphere soils of healthy and diseased C. lanceolata in major production areas in China. It further explored the effects of root rot on the composition, structure, and ecological functions of rhizosphere microorganisms. The results demonstrated that seasonal variations significantly influenced the physicochemical properties and microbial composition of the rhizosphere soil in C. lanceolata affected by root rot. Microbiome analysis further confirmed that, within the same season, healthy C. lanceolata contained a greater abundance of ecologically beneficial microbial taxa in the rhizosphere soil compared to diseased trees. These microorganisms may function as bioprotectants. This study enhances our understanding of the structural and functional changes in the rhizosphere soil microbiome associated with soil-borne diseases and provides potential ecological management strategies to improve plant resistance to root rot.