Biochar modification can enhance the properties associated with porosity and functional groups and has been identified as an effective way to improve adsorption capacity. Modified corncob biochars pretreated by different contents of MgCl₂ are obtained through slow pyrolysis; then, this work explores the adsorption abilities towards heavy metals. After modification, biochars mainly impregnate carbon surface with Mg(OH)₂ and MgO particles. The best mass ratio of magnesium (Mg)/feedback is 15% for modified biochar, and 15%Mg-BC has much higher (2.36–9.34 times) metal sorption capacity than pristine biochar. Batch adsorption experiments show that copper (Cu(II)) and lead (Pb(II)) on adsorbents follow a pseudo-second-order model and cadmium (Cd(II)) follows an intraparticle diffusion model. The adsorption isotherm of Cu(II) fits well with the Langmuir model, and Pb(II) and Cd(II) fit with the Freundlich model. In the binary system, modified biochar still effectively removes metals, but the sorption capacity of metals decreases rapidly because of competitive sorption. The main adsorption mechanisms of metals include surface precipitation, cation π-banding, complexation, and ion exchange. The results show that Mg-modified biochar may be an environmentally friendly material for reducing the water pollution of heavy metals.

To consummate watershed data and better quantify the impact of climate changes and human activities on runoff, we examined the changes and response mechanisms of runoff in the Min–Tuo River Basin, China. In the examination, the Soil and Water Assessment Tool (SWAT) model was used to simulate possible evapotranspiration, actual evapotranspiration, and runoff in 1980, 1990, 1995, 2000, 2005, 2010, and 2015 under different land-use conditions. SWAT weather generator was used to supplement the missing meteorological data. This study presents a quantitative analysis of the climatic and anthropogenic factors contributing to the runoff alteration in the Min–Tuo River Basin using the Budyko methods. The results suggested that the reduced precipitation was the main cause of runoff reduction. The contributions of precipitation, possible evapotranspiration, and underlying surface alterationsof runoff were 56.18%, 37.08%, and 6.74%, respectively. Sensitivity analysis indicated that the runoff alteration was most sensitive to changes of landscape parameters. The aridity index and all the elasticities showed a spatial variations in the Min–Tuo River Basin. The influence of the three factors on runoff reduction varied with seasons. During the high-flow period, changes of the precipitation and possible evapotranspiration and underlying surface had the greatest effect on runoff reduction, while changes of underlying surfaces had the least effect.

In the face of escalating global warming and intensified human activities, it is crucial to quantitatively assess the combined impacts of future climate change (CC) and land use change (LUCC) on runoff. This study employed simulation results of future CC and LUCC in the Min-Tuo River Basin, utilizing the CMIP6 and CA-Markov models in conjunction with the SWAT model to project runoff changes under various scenarios. The findings indicate an anticipated increase in both precipitation and average temperature in the future. Projected LUCC involves a reduction in arable land and grassland, alongside expansion of other land cover types. Changes in basin runoff are predominantly influenced by precipitation, with a higher likelihood of extreme events as CO2 emissions increase. Across four emission scenarios, the impact of future CC on basin runoff varies from −5.21% to +6.09%, while future LUCC's contribution ranges from +0.05% to +0.07%. When both factors are considered, the overall trend indicates a decrease in future runoff changes, ranging from −0.27% to +0.17%. These findings underscore the greater influence of CC on runoff compared to LUCC, thereby providing a scientific foundation for ecological conservation and water resources management in the basin.