To improve the substandard engineering properties of saline soil in cold regions and to mitigate the environmental pollution caused by conventional calcium-based stabilization materials, ionic soil stabilizer (ISS) along with lime and fly ash are added to saline soil. Triaxial tests and discrete element numerical simulations are employed to investigate the macro-microscopic mechanical properties of the ISS stabilized saline soil in a frozen state. The results demonstrate that adding ISS significantly improves the mechanical properties of lime and fly ash-stabilized saline soil under frozen conditions. The strength of the ISS stabilized soil reaches its peak at an ISS content of 3 %, but further increase in ISS content leads to a decrease in strength. The discrete element method (DEM) indicates that a failure surface forms an angle of approximately 55 degrees degrees to the horizontal plane, with particle displacement symmetrical about the failure surface. The pore structure is significantly influenced by confining pressure during loading, and a quantitative analysis is conducted on the changes in porosity and coordination number. This research offers valuable insights for improving the undesirable engineering properties of saline soil in seasonal frozen regions using ISS and for studying its macro-microscopic mechanical characteristics. Additionally, it contributes to reducing the use of inorganic materials, thereby promoting environmental protection.

Organic material plays an essential role in the ecological restoration of different types of surfaces with engineering damage in extremely fragile environments. An outdoor mesocosm experiment was conducted to explore the effects of modified organic material on chemical, physical properties and microbial communities of reconstructed soil in ecologically restored engineering slopes of the Qinghai-Tibetan plateau. The physical and chemical properties of the soil indicate that the addition of modified organic materials significantly improves soil nutrients. In this area, organic carbon increased by 1.87 g.kg(-1) in the frame beam slopes compared with the control area, and the potassium content doubled. In addition, modified organic material effectively induced soil metabolism responses, mainly promoting the activities of soil enzymes like amylase, cellulase, urease, sucrase, and alkaline phosphatase. Moreover, addition of modified organic material noticeably changed the abundance and structure of microbial communities in soils. The enhanced concentrations of the signal molecules N-acylated-L-homoserine lactone and auto inductor peptide indicated that addition of modified organic materials significantly influenced quorumsensing in soil microbial communities. There are differences in the soil improvement effects of different types of slopes, among which the frame grid beam has the best effect. These findings demonstrate the effect and underlying mechanisms of the addition of incorporating modified organic materials, primarily sodium carboxymethyl cellulose and anionic polyacrylamide, into the soil of engineering slopes. These results have extensive application prospects for ecological restoration in strict environments.

In order to improve carrot quality and soil nutrition and reduce the environmental pollution caused by intensive carrot production, more comprehensive combined water-fertilizer management strategies are necessary. This study hypothesizes that optimal management of water and fertilizer can improve carrot yield and quality and reduce greenhouse gas emissions and soil nutrient residues. Thus, coordinated water-fertilizer management strategies were tested for carrot production on the North China Plain over two consecutive growing seasons. Four treatments were tested: local standard fertilization and irrigation practices (FNP); optimized irrigation and chemical nitrogen, phosphorus, and potassium fertilizer (OPT); OPT treatment with partial replacement of chemical fertilizer with peanut shell (PS); and OPT treatment with partial replacement of chemical fertilizer with mushroom residue (M). Compared to the FNP treatment, there were statistically significant increases in soluble sugars (12-27%) and free amino acids (14-26%), and decreases in the nitrate content (7-17%) of fleshy root in the OPT, PS, and M treatments. In autumn carrots, the OPT and M treatments decreased yield, whereas PS increased yield; spring carrot yield was significantly decreased in the OPT, PS, and M groups compared to the FNP group. There were no significant effects of the treatment group on carrot growth rates, nutrient accumulation, or nutrient distribution. However, the OPT, PS, and M treatments were associated with significantly increased partial productivity of phosphate fertilizer (233-363%), reduced residual levels of nitrate and available phosphorus in the top 80 cm of soil, and decreased greenhouse gas emissions by 8-18% compared to the FNP treatment. These results highlight the effectiveness of partial organic fertilizer substitution and integrated water-fertilizer management to produce high-quality carrots with minimal environmental damage.