The global reserve of sand has significantly decreased, and sand washing is predominantly favored due to its simplicity and low operational costs, but this method poses significant environmental risks like landslides, making its reuse essential for sustainability. In view of this challenge, based on the composite preparation method, an innovative approach was proposed to prepare an artificial soil substrate from sand-washing slurry. The physical and vegetative feasibility performance, including strength, density, water absorption, retention, electrical conductivity (EC), and pH; and microstructural characteristics, including X-ray diffraction (XRD), scanning electron microscopy (SEM), and nuclear magnetic resonance (NMR) of the artificial soil substrate with different proportions of cement and foaming agent were measured. Increasing the cement content to 30% of un-crushed artificial soil substrate specimens improved strength, whereas 40% reduced it due to the diminished pore-filling effect. Water absorption rates ranged from 29.22% to 36.68%, increasing with more foaming agent and decreasing with more cement, while the water retention time was 12-14 days, and incorporating foaming agent significantly increased water absorption. Leachate pH ranged from 11.99 to 12.18, and reduced to 7.82-8.28 with 5% phosphoric acid. The EC of the artificial soil substrate decreased by 88.64% to 93.59% after 10 wet-dry cycles, aligning with the standard. Artificial-soil-substrate-predominant products include calcite, quartz, and dolomite, with a pronounced silica content and soil substrate porosity ranging from 27.96% to 51.80%. From the microstructural test, calcium silicate hydrate gel, produced by cement hydration, effectively bound the sand-washing slurry, thereby improving strength.

Peatland is a key component of terrestrial ecosystems in permafrost regions and have important effects on climate warming. Soil enzymes are involved in biogeochemical cycle of soil carbon (C), nitrogen (N) and phosphorus (P), which can be used as early sensitive indicators of soil nutrient changes caused by climate change. To predict the possible effects of permafrost degradation on soil enzymes in peatlands, ten peatlands from three types of permafrost regions along the permafrost degradation sequence (predominantly continuous permafrost region-predominantly continuous and island permafrost region-sparsely island permafrost region) in northeast China were selected to examine the activities of soil invertase, beta-glucosidase, urease and acid phosphatase and their relationships with soil physicochemical properties. The results demonstrated that permafrost type had significant effect on soil enzyme activities. Soil enzyme activities in predominantly continuous and island permafrost region were significantly higher than those in sparsely island permafrost region and predominantly continuous permafrost region. The activities of four soil enzymes were higher in 0-15 cm than 15-30 cm soil layer. Soil enzymes activities were positively correlated with soil ammonia nitrogen (NH4+-N), soil moisture content (SMC), total phosphorus (TP) and total nitrogen (TN), but negatively correlated with soil nitrate nitrogen (NO3--N). Soil inorganic nitrogen and moisture contents were the main factors affecting soil enzyme activities, with NH4+-N accounted for 41.6% of the variance, SMC 29.6%, and NO3--N 11.0%. These results suggested that permafrost degradation may change soil enzyme activities by changing soil physicochemical properties. In this study, only 0-30 cm peat soil in permafrost regions was collected during the complete thawing period of permafrost active layer, further studies should be placed on the change of soil enzyme activities in active layer and permafrost layer during freezing and thawing process in the southernmost location of northeast China in the Eurasia permafrost body and boreal forest belt.