This study investigates the adsorption and migration of sulfadiazine (SDZ) in soda saline–alkali soils under Cu/Zn co-pollution using equilibrium adsorption and soil column experiments. Freundlich and Langmuir isothermal models, combined with Hydrus-1D two-site modeling, revealed concentration-dependent interactions. Low Cu (10–100 mg kg⁻¹) and Zn (10–100 mg kg⁻¹) enhanced SDZ adsorption via charge regulation and complexation, while high concentrations (300 mg kg⁻¹) suppressed adsorption through competitive adsorption and hydroxide precipitation. Synergistic Cu-Zn coexistence further reduced adsorption to 3.035 mg kg⁻¹. Freundlich modeling (R² = 0.922–0.995) outperformed Langmuir, confirming adsorption site heterogeneity. Column experiments showed Cu (300 mg kg⁻¹) and Zn (300 mg kg⁻¹) accelerated SDZ migration (peaks 0.93–0.94), delaying breakthrough versus Br⁻. Hydrus-1D simulations (R² ≥ 0.915, RMSE < 0.1) effectively quantified nonlinear dynamics between instantaneous adsorption sites (f = 0.101–0.554) and metal concentrations. Results demonstrate heavy metals critically regulate antibiotic fate via concentration-dependent mechanisms in saline–alkali ecosystems.

Black carbon (BC) and polycyclic aromatic hydrocarbons (PAHs) are potentially proxies of changes in natural and human activities during the past century. It is important to identify historical BC sources and differentiate human activities contribution to BC in the environment. In this study, a 30 cm peat profile from the Jiadengyu (JDY) peatland in Altay Mountain was dated by the 137Cs and 210Pb methods. BC, total PAHs content and δ13CBC in JDY peat were tested. The results showed that the TOC, BC and PAHS contents in JDY peat core were 17.09 ~ 47.16%, 1.14 ~ 67.138 mg/g and 260.58 ~ 950.98 ng/g, respectively. The value of δ13CBC ranged -31.5‰ ~ -27.43‰, with an average of -30.52‰. The range of total PAHs concentrations in JDY peat core were between 260.59 ng/g and 950.98 ng/g. The BC was significantly correlated with PAHs and regional population. The BC fluxes have slightly increased since 1900s with the increasing population and cultivate area, and more significantly in 1980s. The burning of biomass and yak dung, fossil fuels, and human activities (mining, coking coal) may have important effects on the BC emission of soil in the Altay region. The change of BC and δ13CBC reflected the change of local energy structure. With the regional reclamation increasing and environment- friendly industry developing, the BC source of JDY peatland is mainly the result of the interaction between biomass combustion and fossil fuel combustion.

In order to evaluate the utilization potential and environmental risk of iron tailings in ameliorating soda saline–alkali soil, a leaching experiment of iron tailings was carried out by simulating the soil acid–base environment and the saline–alkali stress environment of soda saline–alkali, and the basic physicochemical properties and the content and leaching characteristics of metal elements of iron tailings were analyzed to evaluate the environmental risk. The results showed that the iron tailings sand had a large specific surface area (0.66~0.91 m²·g⁻¹) and a rich pore structure (pore diameter 9.07~11.48 nm), which was conducive to the adsorption of salt-alkali by iron tailings sand. The main chemical composition of iron tailings is SiO₂ (33.39%~57.32%) and Fe₂O₃ (8.47%~14.94%), the content of plant nutrient elements in iron tailings is abundant, and the content of risk elements is far below the national standard limit. The leaching experiment results indicated that under acid or alkali conditions, the leaching amounts of various metal elements from the iron tailings met the national water quality standards for farmland irrigation, with Cd, Hg, Mn, Al, Ca, and others being more readily leached under acidic conditions. Under the same pH conditions, Cd, Hg, As, Al, and others were more readily leached under the soda saline–alkali environment. Unlike in the soil acid–base environment, the correlations between the leaching amounts of different metals were weaker under the combined soda saline–alkali stress, with only As and Al showing a positive correlation with the pH of the leachate, though the correlation was not significant. This study confirms that the environmental risk of using iron tailings for the improvement of soda saline–alkali soil is relatively low, and long-term changes in the contents of heavy metals such as As and Al in the soil should be given focused attention in future work.