RESUMEN
Ammonia, a significant precursor for secondary inorganic aerosols, plays a pivotal role in new particle formation. Inventories and source apportionment studies have identified vehicular exhaust as a primary source of atmospheric ammonia in urban regions. Existing research on the factors influencing ammonia emissions from gasoline vehicles exhibits substantial inconsistencies in both test results and analyses. The lack of a uniform pattern in ammonia emissions across different standard vehicles and the significant overlap in test results across diverse operational conditions highlight the complexities in this field of study. While individual results can be interpreted through a mechanistic lens, disparate studies often lack a common explanatory framework. To address this gap, our study leverages the robust and comprehensive approach of meta-analysis to reconcile these inconsistencies and provide a more precise understanding of the factors influencing ammonia emissions from gasoline vehicles. A large number (N = 537) of ammonia emission factors were extracted after screening >1628 publications. The combined ammonia emission factor was 23.57 ± 24.94 mg/km. Emission standards, engine type, ambient temperatures, mileage, vehicle speed, and engine displacement have a significant impact on ammonia emission factors, explaining the ammonia emission factor by up to 50.63 %, with speed being the most significant factor. All these factors are attributed to the interplay of catalyst properties, lambda, and residence time (space velocity). In the current fleet, ammonia emission control is relatively insufficient under low-speed and ultra-high speed, low temperature, and ultra-high mileage conditions. Since ammonia emission factors do not monotonically decrease with the upgrading of motor vehicle emission standards, it is called for the addition of ammonia emission factors indicators in motor vehicle emission standards, and stipulation of targeted testing procedures and testing instruments.
RESUMEN
Tea anthracnose is a prevalent disease in China that can lead to reduced tea production and lower quality, yet there is currently a lack of effective means for controlling this disease. In this study, we identified 46 phenolamides (including 27 isomers) in different tissues and organs of tea plants based on a developed workflow, and the secondary mass spectra of all these compounds have been documented. It was revealed that tea plants predominantly accumulate protonated aliphatic phenolamides, rather than aromatic phenolamides. The profile of phenolamides indicate that their buildup in tea plants is specific to certain tissues and acyl-acceptors, and this distribution is associated with the extent of phenolamide acyl-modification. Additionally, it was observed that N-Feruloylputrescine (Fer-Put, a type of phenolamides) was responsive to the stimulated accumulation of the tea anthracnose pathogen. The findings of anti-anthracnose experiments in vitro and on tea leaf demonstrated that Fer-Put was capable of significantly inhibiting the growth of anthracnose pathogen colony, effectively prevented tea leaf disease. Furthermore, it was observed that Fer-Put treatment can enhance the antioxidant enzyme activity of tea leaves. TEA002780.1 and TEA013165.1 gene may be responsible for the biosynthesis of Fer-Put in the disease resistance process in tea plants. Through these studies, the types and distribution of phenolamides in tea plants have been elucidated, and Fer-Put's ability to resist anthracnose has been established, providing new insights into the resistance of tea anthracnose.
RESUMEN
Road dust, a significant contributor to non-exhaust particulate matter emissions in urban transport, poses considerable health risks, necessitating accurate and high-resolution data for effective control. The traditional AP-42 method offers data on point-specific dust emissions, while vehicle-based testing ascertains the relative emission intensity in the road network. However, a clear mathematical relationship between these measurements has been elusive, limiting efficiency in emission control. By integrating the On-board Conventional Pollutant Monitoring System with the AP-42 method, we devised a dynamic link between the concentration of particles in vehicle plumes and actual road dust emissions. This relationship is substantiated by a notable correlation (R2 = 0.91) between our emission factors and those calculated using the AP-42 method. Significant variations emerged in dust emission factors across road types, with changes between -30.1 % to +57.79 % from the average (0.05 g·vehicle-1·km-1), in tandem with traffic flow fluctuations of approximately ±90 %. Meteorological factors, except for continuous rainfall, showed minimal impact on dust emissions. However, our findings revealed a significant underestimation (58.87 %) of road dust PM10 emissions by the AP-42 method. Intriguingly, we found that short-range emission hotspots substantially contribute to total emissions, suggesting a potential 50 % reduction by controlling merely 8.8 % ± 2.5 % of the total road length. Our research elucidates the interplay between road dust emissions, road types, and human activities. The application of a dynamic, high-resolution assessment method enhances our understanding of the impacts of road dust on urban particulate pollution, allows accurate hotspot identification, and aids in developing efficacious strategies for air quality enhancement.