The salinization of sulfate saline soil in frozen regions can lead to severe potential environmental hazards, such as increased salt heaving and collapsibility. Corn stalk ash (CSA), a typical agricultural waste that is non-polluting to soil, groundwater, and the environment, possesses high pozzolanic activity and is a potential amendment for sulfate saline soil. To verify the feasibility of using CSA to improve sulfate saline soil, a series of experiments were conducted to study the effects of CSA content, salt content, and freeze-thaw cycles on the mechanical properties of the improved soils. A statistical damage constitutive model was established that comprehensively considers the coupled effects of freeze-thaw, salinity, moisture, and loading to more accurately describe the improvement effects of CSA. The study shows that CSA is highly effective in improving sulfate saline soil. The application of this method can significantly increase the unconfined compressive strength (UCS) of sulfate saline soil and greatly enhance their freeze-thaw resistance. The best improvement effect was observed with a CSA content of 15%. Furthermore, the coupled statistical damage constitutive model more accurately and intuitively analyzed the entire deformation and failure process of the improved soil under coupled effects, showing that the addition of CSA enhances the brittle characteristics of the improved soil while reducing its plastic deformation and ductile failure characteristics. In summary, the method of using CSA to improve sulfate saline soil is highly effective and environmentally friendly, providing a theoretical basis for improving sulfate saline soil in seasonally frozen regions.

Organic aerosol (OA) can absorb solar radiation in the low-visible and ultra-violet wavelengths thereby modifying radiative forcing. Agricultural waste burning emits a large quantity of organic carbon in many developing countries. In this work, we improved the extraction and analysis method developed by Chen and Bond, and extended the spectral range of OC absorption. We examined light absorbing properties of primary OA from pyrolysis of corn stalk, which is a major type of agricultural wastes. Light absorption of bulk liquid extracts of OA was measured using a UV vis recording spectrophotometer. OA can be extracted by methanol at 95%, close to full extent, and shows polar character. Light absorption of organic aerosol has strong spectral dependence (Absorption Angstrom exponent = 7.7) and is not negligible at ultra-violet and low-visible regions. Higher pyrolysis temperature produced OA with higher absorption. Imaginary refractive index of organic aerosol (k(OA)) is 0.041 at 400 nm wavelength and 0.005 at 550 nm wavelength, respectively. (C) 2016 Elsevier Ltd. All rights reserved.