Large-flow waste gas generated from the pharmaceutical and chemical industry usually contains low concentrations of VOCs (volatile organic compounds), and it is also the key factor that presents challenges in terms of disposal. To date, due to the limitations of mass transfer rate and microbial degradation ability, the degradation performance of VOCs using the biological method has not been ideal. Therefore, in this study, the sludge from a chlorobenzene-containing wastewater treatment plant was inoculated into our experimental bio-trickling filter (BTF) to explore the feasibility of domestication and degradation of gaseous chlorobenzene by highly active microorganisms. The kinetics of its mass transfer reaction and microbial community dynamics were also discussed. Moreover, the main process parameters of BTF for chlorobenzene degradation were optimized. The results showed that the degradation effect of chlorobenzene reached more than 85% at an inlet concentration of chlorobenzene 700 mg·m⁻³, oxygen concentration of 10%, and an empty bed retention time (EBRT) of 80 s. The mass transfer kinetic analysis indicated that the process of chlorobenzene degradation in the BTF occurred between the zero-stage reaction and the first-stage reaction. This BTF contributed significantly to the biodegradability of chlorobenzene, overcoming the limitation of gas-to-liquid/solid mass transfer of chlorobenzene. The analysis of the species diversity showed that Thermomonas, Petrimona, Comana, and Ottowia were typical organic-matter-degrading bacteria that degraded chlorobenzene efficiently with xylene present.

The absorption of atmospheric particulate matter lead (APM-Pb) by wheat leaves is the primary source of Pb in wheat grains, yet the mechanisms of how wheat leaves absorb Pb remain unclear. In this study, spraying Pb(NO₃)₂ (Treatment T1) and spraying PbS (Treatment T2) were used as soluble and insoluble Pb, respectively, to evaluate the primary pathways of APM-Pb absorption by wheat leaves, as well as the translocation and accumulation patterns of Pb within the wheat plant. The results showed that both soluble and insoluble Pb can be absorbed by wheat leaves. Compared to the control group (CK), the treatment of T1 and T2 significantly increased Pb concentration in both leaves and grains, as well as the Pb accumulation rate in grains (p < 0.05). Scanning electron microscopy–energy dispersive spectrometry (SEM-EDS) technology visually confirmed the distribution of particulate Pb in the stomatal region, demonstrating that solid-state Pb can penetrate the leaves through stomata. From the greening stage (GS) to the late filling stage (FS2), the leaves’ cell sap contained the highest proportion of Pb, indicating that Pb within the cell sap possesses the greatest capacity for translocation. Concurrently, a significant increase in grain Pb concentration during this period indicated that the migration of Pb to cell sap after penetrating the leaves is subsequently translocated to the grains (p < 0.05). Compared to the jointing stage (JS), the proportion of the ethanol and water extraction states of Pb significantly decreased in FS2 (p < 0.05), indicating that Pb is more readily translocated to the grains during this period. Moreover, in FS2, Pb concentration in leaves and grains in the T2 treatment reached 76.5% and 63.9% that of T1, respectively. Since PbS can only be absorbed through stomata, it can be inferred that stomata are the primary pathway for wheat leaves to absorb APM-Pb. Therefore, Pb absorbed through the stomatal pathway and accumulated in the cell sap fraction is most likely to be translocated to the grains during the filling stage. This study provides new insights into the mechanisms of Pb absorption and translocation in wheat, emphasizing the critical role of stomata in the uptake of APM-Pb. It offers a new direction for breeding wheat varieties resistant to APM-Pb pollution, which is of significant importance in agricultural practices aimed at reducing heavy metal contamination in crops.

The study of the effect of the mechanism of urea addition to sewage sludge and sawdust-composting substrates on methane production is still limited. In the present study, the systematic investigation of the effect of urea addition (0.18, 0.9 and 1.8 kg) on methane production is discussed through the dynamics of physical properties, enzymes, and the microbial community during composting. The results showed that high urea addition (1.8 kg) suppressed methane production, with a lower rate and a shorter duration of warming in the thermophilic phase, but significantly enhanced cellulase activity, urease, and peroxidase, and promoted the degradation of organic carbon, as well as the loss of nitrogen. A high addition of urea stimulated the growth and reproduction of Sinibacillus, Pseudogracilibacillus, Sporosarcina, and Oceanobacillus. The random forest model indicated that the top six independent determinants of CH₄ emissions were Methanobacterium, temperature, organic matter (OM), Methanospirillum, and NH₄⁺-N. Furthermore, structural equation modeling displayed that NH₄⁺-N, O₂, and pH were the main physicochemical properties affecting CH₄ emissions. Methanobacterium, Methanosarcina, and Methanosphaera were the main archaea, and Bacillaceae were the main bacteria affecting CH₄ emissions. This study provides new insights and a theoretical basis for optimizing urea addition strategies during composting.