Nitrogen (N) transformation in soil directly determines the effectiveness of N for plant growth. Biochar has received evermore attention because of its significant ability to improve soil. However, the effects of biochar on N-related microorganisms (Lycopersicon esculentum Mill.) in tomato cultivation soil, N transformation, utilisation of water and N fertiliser, and tomato yield remain unclear. The objective of this study was to investigate the responses of N-related microorganisms to biochar and N fertilisation in soil, along with the implications of biochar for altering N transformation, N uptake by tomatoes, and utilisation of water and N fertiliser. A two-year greenhouse experiment containing six biochar levels under drip irrigation (0, 10, 30, 50, 70, and 90 t ha⁻¹) and two N fertiliser application rates (190 and 250 kg ha⁻¹) was conducted in the northwest of China. The results showed that adding biochar significantly promoted urease activity, microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and the number of amoA-type nitrifiers in the soil. The MBC:N ratio and the number of nirS-type denitrifiers were significantly inhibited when the added amount of biochar was greater than or equal to 30 t ha⁻¹. Moreover, biochar can increase the water content in the soil and can reduce the N lost to leaching. The inorganic N (NO₃⁻ and NH₄⁺) in the soil could be better maintained in the rootzone and better absorbed by tomato plants when adding 30, 50, and 70 t ha⁻¹ of biochar. The amount of N fertiliser could be reduced by 24% without a significant loss of tomato yield when the amount of biochar added was over 30 t ha⁻¹. It was indicated that the yield of tomatoes and the net profits were quadratically related to the application rate of biochar. In the test area, 53 t ha⁻¹ of biochar with 190 kg ha⁻¹ of N and 44.6 t ha⁻¹ of biochar with 190 kg ha⁻¹ of N were calculated to be the best amounts from the perspectives of tomato yield and net profit, respectively. Thus, biochar promotes N transformation by regulating N-related microorganisms; hence, it increases the inorganic N in the roots of the plants, reduces N lost to leaching, and significantly promotes the N absorption of tomatoes. The results in this research are of great significance for the development of management strategies for tomato maintenance, environmental protection, and resource conservation.

With the advances in engine technology, the exhaust gas temperature of automobiles has further reduced, which in turn leads to an increase in the emissions of carbon monoxide (CO) and hydrocarbons (HCs). In order to understand the influence of CeO₂-based catalysts loaded with different noble metals on the catalytic oxidation activity of CO and HCs, this study constructed catalyst models of Ce_0.875Zr_0.125O₂ (100) surfaces loaded with Pt, Pd, Ag, and Au. The electronic density and state density structures of the catalysts were analyzed, and the reaction energy barriers for CO oxidation and C₃H₆ dehydrogenation oxidation on the catalyst surfaces were also calculated. Furthermore, the activity sequences of the catalysts were explored. The results revealed that after loading Pt, Pd, Ag, and Au atoms onto the catalyst surfaces, these noble metal atoms exhibited strong interactions with the catalyst surfaces, and electron transfer occurred between the noble metal atoms and the catalyst surfaces. Loading with noble metals can enhance the catalytic activity of CO oxidation, but it has little effect on the dehydrogenation oxidation of C₃H₆. Of the different noble metals, loading with Pd exhibits the best catalytic activity for both CO and C₃H₆ oxidation. This study elucidated the influence of noble metal doping on the catalytic activity of catalysts at the molecular level, providing theoretical guidance for the design of a new generation of green and efficient catalysts.