Cow dung (CD) is a waste product of livestock production. Improper disposal of a large amount of CD will cause environmental pollution. In this work, three biochar materials based on CD (BMCD) were prepared by using three types of base, including KOH, NaOH, and mixed base (MB, a mixture of equal mass NaOH and KOH) as activators to investigate the different physicochemical properties of BMCDs (BMCD-K, BMCD-Na, and BMCD-MB). The objective was to verify the effectiveness of MB activation in the preparation of biochar materials. The results show that MB has an effect on the structural characteristics of BMCDs. In particular, the surface area and total pore volume, the specific surface area, and the total pore volume of BMCD-MB (4081.1 m² g⁻¹ and 3.0118 cm³ g⁻¹) are significantly larger than those of BMCD-K (1784.6 m² g⁻¹ and 1.1142 cm³ g⁻¹) and BMCD-Na (1446.1 m² g⁻¹ and 1.0788 cm³ g⁻¹). While synthetic dye rhodamine B (RhB) and antibiotic tetracycline hydrochloride (TH) were selected as organic pollutant models to explore the adsorption performances, the maximum adsorption capacities of BMCD-K, BMCD-NA and BMCD-MB were 951, 770, and 1241 mg g⁻¹ for RhB, 975, 1051, and 1105 mg g⁻¹ for TH, respectively, which were higher than those of most adsorbents. This study demonstrated that MB can be used as an effective activator for the preparation of biochar materials with enhanced performance.

Hydrothermal carbonization is a promising strategy for the resource utilization of agricultural wastes. However, the effect of hydrochar on ameliorating saline–sodic soil remains unclear. In the present study, a novel hydrochar amendment was prepared from spent mushroom substrate (SMSHC), followed by an incubation study of saline–sodic soil samples with different pH values (A, pH 9.83; B, pH 8.98; C, pH 8.21). The results demonstrated that SMSHC reduced the adverse effects of saline–sodic soil effectively, and the best effect was obtained when 6% SMSHC was added. Soil pH and ESP decreased by 0.34–0.75 units and 1.0–13.0% at 6% SMSHC loading, respectively. The maximum percentage increase in the soil’s available N, available P, and DOC was 72.3, 221, and 408%, respectively. In the subsequent rice pot seedling experiment, decreased malondialdehyde (MDA) content and increased K⁺/Na⁺ ratio, proline, soluble sugar, total N, and total P in plant samples were observed. This study verifies hydrothermal carbonization as an alternative method, except for the widely used pyrolysis, to recycle biomass wastes into valuable products for soil remediation.

The burning of straw is a very destructive process that threatens people’s livelihoods and property and causes irreparable environmental damage. It is therefore essential to detect and control the burning of straw. In this study, we analyzed Sentinel-2 data to select the best separation bands based on the response characteristics of clouds, smoke, water bodies, and background (vegetation and bare soil) to the different bands. The selected bands were added to the red, green, and blue bands (RGB) as training sample data. The band that featured the highest detection accuracy, RGB_Band6, was finally selected, having an accuracy of 82.90%. The existing object detection model cannot directly handle multi-band images. This study modified the input layer structure based on the YOLOv5s model to build an object detection network suitable for multi-band remote sensing images. The Squeeze-and-Excitation (SE) network attention mechanism was introduced based on the YOLOv5s model so that the delicate features of smoke were enhanced, and the Convolution + Batch normalization + Leaky ReLU (CBL) module was replaced with the Convolution + Batch normalization + Mish (CBM) module. The accuracy of the model was improved to 75.63%, which was 1.81% better than before. We also discussed the effect of spatial resolution on model detection and where accuracies of 84.18%, 73.13%, and 45.05% for images of 60-, 20-, and 10-m resolution, respectively, were realized. The experimental results demonstrated that the accuracy of the model only sometimes improved with increasing spatial resolution. This study provides a technical reference for the monitoring of straw burning, which is vital for both the control of straw burning and ways to improve ambient air quality.