A carbonate-mineralizing bacterial strain C7-1was isolated from karst soil and identified as Serratia marcescens. Through single factor test combined with characterization technology, the cadmium (Cd) removal efficiency and underlyingmechanism of S. marcescens were analyzed, along with its ability toremove Cd, lead (Pb), zinc (Zn), and copper (Cu) from soil. The results indicated that the urea concentration was the main factor controlling Cd²⁺ removal.The maximum Cd2⁺ removal rate reached 74%, which was primarily via extracellular precipitation (42%) followed by surface adsorption (27%). Cd2⁺ may bind to CO₃^2- to form CdCO₃ based on scanning electron microscope-energy dispersive spectroscopy (SEM-EDS), fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The removal efficiencies of strain C7-1for Cd2⁺, Pb2⁺, Zn2⁺ and Cu2⁺ achieved 22.9%~65.9% in soil filtrates. The heavy metal ions were found to form amorphous mineral precipitates through co-precipitation and were adsorbed onthe bacterial surfaces via functional groups, including hydroxyl, carboxyl, carbonate, phosphoric acid, and sulfuric acid groups.

To investigate the synoptic mechanisms underlying a rare, widespread floating dust weather process in Guangdong Province during 12~16 April 2025, analyses were conducted using multi-source integrated observational data and reanalysis data. The results reveal:The cold front guided by the East Asian trough generated a dust area in southwestern Mongolia and drove it southward into Guangdong Province. Under the influence of dust, PM₁₀ concentrations exceeded standards across all 21 cities in Guangdong, resulting in a total of 54 polluted cities (Including 6heavy pollution). On April 13, provincial average PM₁₀ concentration reached 305.2μg/m³, 2.4 times the magnitude of the second-highest concentration since 2014. Notably, Guangzhou registered the highest daily average PM₁₀ concentration (400μg/m³), significantly exceeding levels observed during the dust intrusion event affecting Guangdong in 2009. Climate analysis of the dust source region revealed that influenced by northwesterly flow ahead of a ridge, the cumulative precipitation in most parts of western Mongolia from February to March was below 10mm, significantly lower than the historical average for the same period. This resulted in soil moisture dropping to the fourth lowest level in the past 30 years, creating conducive underlying surface conditions for dust emission. Analysis of the dust transport process identified that the cold front generated the strongest northerly winds in the Nanling Mountains region in the past three decades. Driven by extreme winds, dust particles were carried directly across the Nanling Mountains andtransported southwards into Guangdong Province. Backward trajectory analysis indicated that dust particles reaching the four major regions of Guangdong were initially transported southward from Inner Mongolia to Hubei Province. Subsequently, they followed three distinct pathways (northern, northeastern, and northwestern routes) southward, traversing mountainous terrain of varying elevations to enter Guangdong, ultimately causing the extensive floating dust event.

A two-month observation of atmospheric PM₁ in suburban Guangzhou in autumn 2022 was conducted using a Soot-Particle High Resolution Time-of-Flight Aerosol Mass Spectrometer (SP-AMS). Sources apportionment of organic aerosol (OA) was performed using Positive Matrix Factorization (PMF). OA's characteristic component particulate organic nitrates (pON) were quantified and explored. During the observation period, PM[(15.90 ± 12.28) μg/m³] was dominated by organics (57.8%), with major components (excluding sulfate) exhibiting higher nocturnal concentrations than diurnal concentrations. OA was mainly contributedby local secondary formation (28.3%), long-range transport (23.9%), and primary emissions such as cooking, vehicle exhaust, and biomass burning (collectively 47.8%). pON contributed significantly to OA (24.7%), increasing markedly under low total nitrate concentrations. Its nocturnal increase may enhance next-day atmospheric oxidation capacity. pON mainly derived from local secondary formation (51.5%) and vehicle exhaust (39.8%). During high PM events, OA was dominated by local secondary formation and vehicle emissions; during high ozone conditions, organics and sulfate showed pronounced midday peaks (photochemical oxidation), secondary OA contribution rose to 59.8%, and pON was primarily from local secondary formation (60.8%).

To investigate changes in the emission characteristics of key pollutants following the transition from household coal-burning to biomass clean heating in the Fenwei Plain, field measurements were conducted in rural areas of Xianyang using a variety of residential biomass-burning devices. Results showed that, in automatically fed pellet stoves, particulate emissions were dominated by PM_2.5, with emission factors for PM_2.5 and PM₁₀ of 1.14g/kg and 1.28g/kg, respectively, significantly lower than those of traditional stoves. Water-soluble ions in PM_2.5 were dominated by K⁺ and Cl^-, accounting for 81.5 %~94.3 % of total ionic mass, which was 25.9 %~69.6 % higher than that in traditional stoves. Due to the use of cleaner fuels and more efficient combustion, the total carbon (TC) emission factor in PM_2.5 from pellet stoves ranged from 0.1 to 0.4g/kg, in contrast to 0.6~3.6g/kg for traditional stoves. Levoglucosan (LG) in PM_2.5 from pellet stoves showed the lowest emission factor, with a lower LG/OC ratio than that of traditional stoves, indicating a reduced contribution of advanced stoves to organic carbon aerosol emissions. By integrating the experimentally derived LG emission factors into an established empirical model, we estimated that the clean-heating transition had reduced the contribution of residential biomass burning to organic carbon aerosol by approximately 6.4 %.

Based on the civil aviation emission inventory for China in 2019, the impacts of aviation emissions on the atmospheric environment were quantified using the CAMx model. Furthermore, the contributions of various flight phases to ground-level pollutant concentrations and their vertical distribution characteristics were explored. The results showed that aviation emissions were found to contribute 0.045 and 0.26μg/m³ to the annual average ground-level PM_2.5 and O₃ concentrations in China in 2019, respectively, with significant regional and seasonal variations being exhibited. The impact of aviation emissions on PM_2.5 was observed to be greater in winter than in summer, while the higher photochemical reaction efficiency in summer was found to facilitate the generation of O₃. The influence of aviation emissions on ground-level PM_2.5 concentrations was mainly concentrated during the landing and take-off cycles, whereas O₃ formation was primarily attributed to emissions during the cruise phase. The vertical distribution of the contributions of aviation emissions to PM_2.5 and O₃ concentrations was observed to exhibit pronounced seasonal variations. In summer, the contribution ratios in East China, Central South, and Southwest regions were found to peak at the 5~9km altitude layer (4.7% for PM_2.5 and 10.6% for O₃), whereas in winter, they were concentrated in the lower 0~2km layer (6.9% for PM_2.5 and 10.8% for O₃). In contrast, in regions such as Northwest China and Xinjiang, the peak contribution of aviation emissions to PM_2.5 concentrations during winter was primarily concentrated in the lower altitude layer below 1km (9.1% for PM_2.5 and 5.9% for O₃). However, in summer, influenced by dust storms, the peak contribution of PM_2.5 concentration in the northwest region was observed at an altitude of approximately 4km (8.1%).

This study investigated cold and hot start processes of diesel vehicles under different load conditions in summer using a heavy-duty chassis dynamometer, with a focus on analyzing NO_x and NH₃ emission characteristics and influencing factors. The results showed that during cold starts, the exhaust gas temperature and coolant temperature rose slowly, and the NO_x sensor was delayed in activation, with over 82% of NO_x emissions occurring before the sensor became operational. During hot starts, the SCR system and sensor entered operation rapidly due to higher system temperatures, leading to significantly lower NO_x emissions. NH₃ emissions were significantly affected by the start condition and simulated load. In the initial phase of cold starts, the NH₃ emission factor was higher than average because of low SCR temperatures. During hot starts, rapid urea hydrolysis without sufficient reaction with NO_x resulted in increased NH₃ emissions. Micro-scale operational modal analysis revealed that the difference in NO_x emissions was mainly determined by engine and SCR temperatures, whereas the difference in NH₃ emissions was associated with SCR temperature and urea injection quantity. The study emphasizes the need to address pollutant emissions during summer cold-start processes and proposes synergistic optimization of temperature control and SCR urea injection strategies to reduce the environmental impact.

Based on the International Civil Aviation Organization (ICAO) standard emission model, combined with statistical data from the Civil Aviation Administration of China (CAAC), an updated 2023~2024 air pollutant and carbon fusion emission inventory for the landing and take-off (LTO) cycles of civil aviation airports in mainland China was constructed, and the accuracy of the emission inventory was verified using the CHAP dataset. The results showed that in 2023, NO_x, CO, HC, SO₂, PM, and CO₂ emissions from LTO cycles at Chinese civil aviation airports were 1.277×10⁵, 1.010×10⁵, 0.084×10⁵, 0.037×10⁵, 0.010×10⁵, and 176.739×10⁵t, respectively. In 2024, the corresponding emissions were 1.353×10⁵, 1.070×10⁵, 0.089×10⁵, 0.039×10⁵, 0.010×10⁵, and 187.189×10⁵t, with a total LTO phase emission increase of 5.91% compared to 2023. The spatial and temporal characteristics of emissions in 2023 and 2024 indicated that economically developed eastern regions (such as Beijing, Shanghai, and Guangzhou) had CO₂ emissions accounting for more than 26% of the national total due to dense flight operations, whereas emissions were lower in western regions due to the limited number of regional airports. Empirical models showed a strong correlation between NO_x emissions and CHAP concentration data (r=0.50), validating the reliability of the inventory.

Taking the typical urban tunnel (Jinhua Tunnel) in Xi'an as the research object, the light-absorption characteristics, molecular composition, and impact on visibility of brown carbon (BrC)from vehicle emissionswere investigatedby employing aerosol size distribution measurements, PM_2.5 chemical speciation, combined withUV-vis spectrophotometry, and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The results showed that aerosols within the tunnel were predominantly ultrafine particles (0.3~0.6μm), with the highest number concentration (2.38×10⁵#/cm³) observed in the internal section, consistent with traffic flow patterns.OC (31.11μg/m³) and EC (7.97μg/m³)concentrations in PM_2.5 were significantly higher than those in the open atmosphere.Elevated levelsof SO₄^2- and Ca²⁺ indicated the synergistic effect of primary vehicle emissions and secondary aerosol formation. Optical analysis revealed a high BrC absorption coefficient of 329.2Mm^-1 in the UV region (200nm) during weekends. At 550nm, the absorption contribution to total extinction was 0.32%. However, this contribution might be underestimated because the full visible spectrum and particle size effects were not considered. At the molecular level, 12548 molecular formulas were identified, primarily categorized as CHO (57.7%), CHOS (19.6%), and CHON (17.3%) compounds. CHON compounds exhibited strong light absorption (34.5% with DBE/C>0.5), while CHONS compounds, characterized by extremely low volatility (91.3% identified as ELVOCs), were more likely to accumulate in the particle phase. This study elucidated the relationships between molecular conjugation, heteroatom interactions, and the light-absorbing capacity of BrC within the tunnel. The visibility effects were quantified, providing a data basis for the refined management of traffic-related BrC, and for improving tunnel air quality and optimizing ventilation and lighting conditions.

Ammonia (NH₃), a cornerstone chemical for sustaining modern society, is traditionally produced via the energy-intensive and carbon-emissive Haber-Bosch process. In light of growing sustainability demands, the electrocatalytic nitrate reduction reaction (NO₃RR), powered by intermittent renewable energy, has recently emerged as a multidisciplinary research frontier. This reaction not only enables ammonia synthesis under ambient conditions but also offers the dual benefit of wastewater remediation and value-added chemical production. This Review highlights recent advances in single-atom site catalysts for NO₃RR. We first discuss the reaction mechanisms underlying nitrate-to-ammonia conversion, with an emphasis on in situ characterization techniques essential for mechanistic insights. We then provide a comprehensive overview of atomically dispersed catalysts in NO₃RR, focusing on the structure-activity relationships that inform the rational design of efficient systems. Finally, we summarize key findings and offer perspectives on current challenges and future directions. This Review aims to inform the development of environmentally benign ammonia synthesis strategies and nitrate valorization technologies, contributing to the advancement of green catalysis in the context of carbon neutrality.

Addressing the challenge of nitrogen-containing wastewater treatment, the photocatalytic-microbial coupled denitrification technology has emerged as a new research hotspot due to its advantages of high efficiency, cost-effectiveness, and environmental friendliness. After a comparative analysis of the advantages and disadvantages of different photocatalytic denitrification technologies, a detailed introduction to the current research status of domestic and international photocatalytic-microbial coupled denitrification processes is provided. The review emphasizes three major forms of the coupled system, including indirect sequential coupling of photocatalytic and microbial, direct coupling, as well as bioelectrochemical-photocatalytic coupling systems. The intrinsic interaction mechanisms within the coupled system are deeply explored, such as the physiological and ecological responses of microorganisms to photocatalysts, the optimization of microbial communities by the photocatalytic process, the migration and transformation mechanisms of photocatalysts within biofilms, and the electron transfer processes between photocatalysts and microorganisms. Finally, the article points out the existing bottlenecks in this technology, such as the development of visible-light materials, the safety of nanomaterials, the long-term stability of the system, and the scaling up for engineering applications. Suggestions are made for deepening the mechanism research, developing new coupled processes, optimizing materials, and promoting engineering applications, with the aim of providing a reference for the efficient and green treatment of nitrogen-containing wastewater.