Particulate organic carbon (POC) is critical to the coastal carbon cycle of the Yellow Sea (YS), a typical marginal sea, but its interannual-to-multiyear variability and driving mechanisms remain unclear due to the limitations of traditional linear or single-factor analyses. To address this gap, we employed model-derived surface POC data from 2003 to 2023 and wavelet coherence analysis to investigate POC variability and regulating mechanisms at multi-scales in the YS. The dominant spatiotemporal mode of surface POC exhibits pronounced seasonality, a consistent coastal-offshore gradient (higher in coastal waters), and a spring maximum, which is regulated by the seasonal alternation controlled by coastal production or input and offshore stratification or ventilation. Wavelet analysis reveals distinct subregional differences in driving mechanisms of POC variability at interannual-to-multiyear scales. Colored dissolved organic matter (CDOM) is the optimal single driver in most subregions, while sea surface temperature (SST) dominates in the Southern Yellow Sea Cold Water Mass (SYSCWM). Specific optimal multi-factor combinations include CDOM+sea surface wind speed (SSW) in the Northern Yellow Sea Cold Water Mass (NYSCWM), chlorophyll a (Chl a)+Photosynthetically Available Radiation (PAR)+partial pressure of carbon dioxide (pCO2) in the SYSCWM, CDOM+Chl a+suspended matter (SPM) in the Jiangsu Shoal (JSS) and CDOM+sea surface salinity (SSS) in the Changjiang River estuary (CRE). These findings clarify the subregional heterogeneity of POC variability and its driving mechanisms in the YS at interannual-to-multiyear scales, and provide a robust scientific basis for accurate regional carbon budget assessments and the optimization of marine numerical models.

Phytoplankton blooms represent a typical ecological process in marine systems. Climate change drives shifts in its phenology, both directly via impacts on physiology and indirectly by modifying stratification intensity, nutrients, light availability, and grazing pressure. Using satellite remote sensing and reanalysis data from 2000 to 2022, this study partitions the Yellow Sea based on interannual variability in the Yellow Sea Cold Water Mass (YSCWM). Clear spatial differences in autumn bloom phenology are observed within the YSCWM. Earlier initiation dominates the Southern YSCWM (SYSCWM), while delayed later initiation concentrates in the Northern YSCWM (NYSCWM) and along the SYSCWM’s eastern margins. This pattern can be explained by the differences in regional hydrodynamics, i.e., the Yellow Sea Warm Current (YSWC) enhances upwelling and convergence in some YSCWM areas, boosting nutrient supply and earlier blooms, whereas weaker circulation-driven nutrient supply causes the bloom delay. Interannual variation analysis further reveals that the bloom timing is regulated by seasonal YSCWM dissipation since intensified autumn northerly winds accelerate dissipation and nutrient supply, thereby advancing blooms, while weaker northerly winds and stable circulation delay bloom progress by maintaining strong thermocline stability. These findings provide further insights into the underlying mechanisms driving autumn bloom dynamics and support ecosystem monitoring efforts in shelf seas.

Amines in fine particles influence atmospheric chemistry by promoting the formation of new particles and contributing to the growth of secondary aerosol mass through acid-base reactions and aminium salt formation. To investigate their abundance, seasonal dynamics, and sources of particulate amines in different environments in Pakistan, concurrent particulate matter (PM2.5) sampling campaigns were conducted at an urban site in Lahore and a rural site in Bhakkar, during the summer (southwest monsoon) and winter of 2022. We report an unexpected observation: the total mean concentrations of thirteen quantified amines are significantly higher in the rural area (60.52 ng m-3 in summer; 79.57 ng m-3 in winter) than in the urban area (1.88 ng m-3 in summer; 11.63 ng m-3 in winter), revealing a reversed urban-rural gradient. Both sites exhibited consistent wintertime enhancements. Dimethylamine was the most abundant species (17-48% of total amines), followed by diethyl-amine (7-23%) and ethylamine (1-17%). The concentrations of amines showed strong positive correlations with sulfur dioxide, PM2.5, and organic carbon, and were elevated during periods of low temperatures and weak winds, suggesting thermodynamic partitioning of haze in winter. The positive matrix factorization (PMF) receptor model identified distinct sources, with rural amines mainly contributed by proteinaceous waste emissions and agrochemical emissions (40.7% and 34.1% respectively). In contrast, urban amines were primarily contributed by waste and biomass burning, fugitive dust, and chemical manufacturing (60.2%, 19.1%, and 14.0% respectively). This study reveals a significant predominance of particulate amines in rural Pakistan, challenging the conventional view of urban-industrial dominance and highlighting the critical influence of localized agricultural and domestic sources on atmospheric chemistry.

Abstract. Nitro-aromatic compounds (NACs) are important atmospheric pollutants that impact air quality, atmospheric chemistry, and human health. Understanding the relationship between NACs formation and key environmental driving factors are crucial for mitigating their environmental and health impacts. In this work, we combined an ensemble machine learning (EML) model with the SHapley Additive exPlanation (SHAP) and positive matrix factorization (PMF) model to identify the key driving factors for ambient particulate NACs covering primary emissions, secondary formation, and meteorological conditions based on field observations at urban, rural, and mountain sites in eastern China. The EML model effectively reproduced ambient NACs and recognized that anthropogenic emissions (i.e., coal combustion, traffic emission, and biomass burning) were the most important driving factors, with the total contribution of 49.3 %, while significant influences from meteorology (27.4 %), and secondary formation (23.3 %) were also confirmed. Seasonal variations analysis showed that direct emissions presented positive responses to NACs concentrations in spring, summer, and autumn, while temperature had the largest impact in winter. By evaluating NACs formation and loss under various locations in winter, we found that anthropogenic sources played a dominant role in increasing NACs levels in urban and rural sites, while reduced ambient temperature along with secondary formation from gas-phase oxidation was the main reason for relatively high particulate NACs levels at the mountain site. This work provides a reliable modelling method for understanding the dominant sources and influencing factors for atmospheric NACs and highlights the necessity of strengthening emission sources controls to mitigate organic aerosol pollution.

Polycyclic aromatic hydrocarbons (PAHs) can be adsorbed onto particulate matter (PM) in the atmosphere. However, few studies have profiled and compared the distribution, sources, and health risks of PAHs associated with smaller particle sizes (i.e., PM1 and PM2.5). To address this gap, we collected ambient PM2.5 and PM1 samples from 89 schools across six cities in the Pearl River Delta region of Guangdong province, China, during April to June and October to December 2018. We characterized 18 PM-bound PAHs by means of gas chromatography-mass spectrometry. Diagnostic ratios and positive matrix factorization (PMF) were employed to identify source apportionment. We assessed the health risks of PAHs via incremental lifetime cancer risk (ILCR), carcinogenic loss of life expectancy (LLE), and non-carcinogenic hazard index (HI). Results showed that, in monitoring cities, the average concentration of 18 PM2.5-bound PAHs was 6.75 (range: 1.26-24.8) ng/m3 in winter and 3.59 (range: 0.6-16.3) ng/m3 in summer, while PM1-bound PAH concentration in winter was 5.39 (range: 1.05-21.9) ng/m3. High-molecular-weight PAHs predominated, with elevated levels observed in winter and in the central and western regions, particularly in PM1 samples. The primary source of PM-bound PAHs was petroleum combustion, mainly attributed to vehicle exhausts. Health risk assessment indicated that carcinogenic toxicity did not show significant differences between PM2.5 and PM1-bound PAHs. Finally, our study expands the existing knowledge of PM2.5 and PM1-bound PAH contamination in the atmospheric environment.

Nitro-aromatic compounds (NACs) are important atmospheric pollutants that impact air quality, atmospheric chemistry, and human health. Understanding the relationship between NAC formation and key environmental driving factors is crucial for mitigating their environmental and health impacts. In this work, we combined an ensemble machine learning (EML) model with the SHapley Additive exPlanation (SHAP) and positive matrix factorization (PMF) model to identify the key driving factors for ambient particulate NACs, covering primary emissions, secondary formation, and meteorological conditions based on field observations at urban, rural, and mountain sites in eastern China. The EML model effectively reproduced ambient NACs and recognized that anthropogenic emissions (i.e., coal combustion, traffic emission, and biomass burning) were the most important driving factors, with a total contribution of 49.3 %, while significant influences from meteorology (27.4 %) and secondary formation (23.3 %) were also confirmed. Seasonal variation analysis showed that direct emissions presented positive responses to NAC concentrations in spring, summer, and autumn, while lower temperatures had the largest positive impact in winter. By evaluating NAC formation and loss under various locations in winter, we found that anthropogenic sources played a dominant role in increasing NAC levels in urban and rural sites, while reduced ambient temperature, along with secondary formation from gas-phase oxidation, was the main reason for relatively high particulate NAC levels at the mountain site. This work provides a reliable modeling method for understanding the dominant sources and influencing factors for atmospheric NACs and highlights the necessity of strengthening emission source controls to mitigate organic aerosol pollution.

The k-median problem and fuzzy k-median problem belong to hard clustering and soft clustering, respectively. Hard clustering involves assigning each client to only one facility, while soft clustering means that there is no clear boundary between clusters; that is, each client can be served by multiple facilities. In our paper, we mainly discuss the seeding and bi-criteria algorithms for fuzzy k-median problem. Firstly, we propose the seeding algorithms, and present the complete analysis of the approximation factor of O(kln k) based on the initialization of the fuzzy k-median++ algorithm for fuzzy k-median problem. Secondly, we design a bi-criteria algorithm reducing the approximation ratio to O(k). Thirdly, we generalize these two kinds of algorithms to a general function. Finally, numerical experiments are carried out to demonstrate the effectiveness of these algorithms.

Amines have significant impacts on air quality, regional climate, and human health. To date, the emissions of amines from traffic sources remain unclear. In this study, we collected fine particulate matters from vehicle and ship exhausts, and subsequently characterized the emissions of 17 amines using ultra-performance liquid chromatography-mass spectrometry. The concentrations and composition of particulate amines vary depending on the types of vehicles and ships. Trimethylamine and 2-Amino-1-butanol were predominant in vehicle exhausts, whereas dimethylamine and diethylamine were prominent in ship exhausts. Diesel vehicles exhibited the highest levels of total amines, followed by gasoline vehicles and compressed natural gas vehicles. Small ships emitted significantly more amines than large ones, with amine concentrations decreasing as engine power increased. Amines emissions from vehicles and ship's exhausts were hypothesized to originate primarily from the three-way-catalyst, selective catalytic reduction, or exhaust gas recirculation systems in the presence of ammonia and organic compounds. Based on the determined emission factors, the annual emissions of fine particulate amines from vehicles and ships in China were approximately 312 kg and 534 kg, respectively. According to the gas particle partitioning coefficient from field measurements, the annual emissions of gaseous amines from vehicles and ships in China were estimated to be 4.2-12.0 Mg and 7.2-20.5 Mg, respectively. Overall, this study presents the unique emission characteristics of particulate amines from vehicle and ship exhausts and confirms the non-negligible emissions from traffic sources.

Ecology experiment is a crucial component of ecology courses. It is the most extensive and effective teaching link for cultivating students' comprehensive qualities such as practice ability, thinking ability and innovation ability, which plays an irreplaceable role in improving students' comprehensive quality. This study analyzed the problems existing in ecological experiments in northern Anhui Province, including the weak ecological knowledge base of students, the single regional habitat, insufficient experimental equipment, traditional teaching methods and single assessment system by taking Suzhou University as an example. This study expounded the practical methods of ecological experiment courses from the aspects of reforming the teaching content, teaching methods, teaching means and examination methods, and put forward some countermeasures. It aims at improving the quality of ecology experiment teaching, enhancing students' practical ability and innovation consciousness, and providing theoretical basis for the cultivation of ecology talents in local applied colleges and universities in northern Anhui Province. Furthermore, this study can also provides a reference for the reform of ecological experimental teaching in similar colleges and universities, which is helpful to promote the overall development of ecological education.

Urban areas exhibit significant gradients in Fine Particulate Matter (PM2.5) concentration variability. Understanding the spatiotemporal distribution and formation mechanisms of PM2.5 is crucial for public health, environmental justice, and air pollution mitigation strategies. Here, we utilized machine learning and integrated air quality sensor monitoring networks consisting of 200 mobile cruising vehicles and 614 fixed micro-stations to reconstruct PM2.5 pollution maps for Jinan's urban area with a high spatiotemporal resolution of 500 m and 1 h. Our study demonstrated that pollution mapping can effectively capture spatiotemporal variations at the urban microscale. By optimizing the spatial design of monitoring networks, we developed a cost-effective air quality monitoring strategy that reduces expenses by nearly 70% while maintaining high precision. The results of multi-model coupling indicated that secondary inorganic aerosols were the primary driving factors for PM2.5 pollution in Jinan. Our work offers a unique perspective on urban air quality monitoring and pollution attribution.

This study explores heterogeneous two-facility location mixed mechanisms, aiming to develop an approach for positioning two facilities that ensures agent strategyproofness while minimizing social costs. We introduce a mixed mechanism that achieves an approximation ratio of 25/8 , demonstrating a significant improvement over the latest deterministic mechanism, which has an approximation ratio of 17/4 .

Fluid interfaces are commonly observed in natural phenomena and industrial applications where heat and mass transfer behaviors as well as the associated energy conversions inevitably impact both material fabrication and chemical reactions. It is known that fluid interfaces, including both air-liquid and liquid-liquid interfaces, are proven to involve a series of spatiotemporal physicochemical effects that dominate the fluid-interface-involved processes, instead of being a simple medium. However, it remains a challenge to understand and utilize the underlying mechanisms of the interfacial effects. This perspective focuses on the latest progress in fluid-involved interfacial behaviors, emphasizing the fundamental "heat and mass transfer" and corresponding "energy transfer" on both liquid-air and liquid-liquid interfaces, which can be regulated by external fields, such as temperature fields, shear fields, acoustic fields, and electric fields. Additionally, we discuss the ongoing challenges and potential evolutionary influences of fluid interfaces, pointing out that by orchestrating various external fields, fluid interfaces can be harnessed to play more important roles in chemical reactions, material assemblies, crystal growth, and fluidic devices.

Nitro-aromatic compounds(NACs)are among the major components of brown carbon(BrC)in the atmosphere,causing negative impacts on regional climate,air quality,and ecologi-cal health.Due to the extensive origins,it is still a challenge to figure out the contributions and originating regions for different sources of atmospheric NACs.Here,field observations on fine particulate NACs were conducted at a coastal rural area in Qingdao,China in the winter of 2018 and 2019.The mean total concentrations of fine particulate nitro-aromatic compounds were 125.0±89.5 and 27.7±21.1 ng/m3 in the winter of 2018 and 2019,respec-tively.Among the measured eleven NACs,nitrophenols and nitrocatechols were the most abundant species.Variation characteristics and correlation analysis showed that humidity and anthropogenic primary emissions had significant influences on the NAC abundances.In this study,two tracing methods of the improved spatial concentration weighted trajectory(SCWT)model and the receptor model of positive matrix factorization(PMF)were combined to comprehensively understand the origins of NACs in fine particles at coastal Qingdao.Four major sources were identified,including coal combustion,biomass burning,vehicle exhaust,and secondary formation.Surprisingly,coal combustion was responsible for about half of the observed nitro-aromatic compounds,followed by biomass burning(～30％).The results by SCWT demonstrated that the coal combustion dominated NACs mainly originated from the Shandong peninsula and the areas to the north and southwest,while those dominated by biomass burning primarily came from local Qingdao and the areas to the west.

Nitrated phenolic compounds in the atmosphere are receiving increasing attention due to their light absorption and biological toxicity. In this study, particulate, gaseous, and cloud water samples were simultaneously collected during cloud events at the summit of Mount Tai in northern China in spring, summer, and winter and the contents of 11 nitrated phenolic compounds were determined. The seasonal average concentrations of the total nitrated phenolic compounds in particles were in the range of 7.3–27.1 ng m −3 , a little lower than those measured in the gas‐phase (18.3–70.6 ng m −3 ). Their concentrations in cloud water were at the levels of 168.4–438.5 μg L −1 . 4‐Nitrophenol and nitrosalicylic acids were the dominant compounds in particles, while 4‐nitrophenol and 2,4‐dinitrophenol were the most abundant in the gas phase and cloud water samples. During cloud events, most nitrated phenolic compounds were mainly distributed in the particle phase, except dinitrophenols which were mainly distributed in the gas phase in winter. The field‐derived effective Henry's law coefficients were several orders of magnitude higher than their theoretical values in pure water. Moreover, the measured concentrations of particulate nitrated phenolic compounds were substantially greater than the theoretical predictions, especially in spring. The above results indicate that nitrated phenolic compounds were partly formed via aqueous‐phase reactions inside the cloud droplets or on the wet particle surfaces, which changed their distribution patterns. The much higher ratios of 2,4‐dinitrophenol to the sum of 4‐nitrophenol and 5‐nitrosalicylic acid in cloud water than those in particles further confirm the enhanced formation via aqueous processes.

Particulate organic nitrates, among the major components of secondary organic aerosols and fine particles, play important roles in regional nitrogen cycle, ozone budget, and cloud condensation nuclei formation. However, the pollution characteristics of particulate organic nitrates at mountain areas and the effects of anthropogenic pollutant transport remain poorly understood. In this study, field sampling and measurements were conducted at a high-elevation mountain site over North China Plain in winter and spring. Total five kinds of particulate organic nitrates in fine particles were determined by ultra-high performance liquid chromatography-electrospray mass spectrometry. The average total concentrations of particulate organic nitrates were 330 ± 121 ng m-3 and 247 ± 63 ng m-3 in winter and spring. The monoterpene-derived organic nitrates were the dominant components in both seasons with their contribution higher than 70%, accounting for 1.2 ± 0.8% and 2.0 ± 1.0% in organic aerosols in winter and spring, respectively. The significantly higher levels of particulate organic nitrates in winter than spring was ascribed to the strong effects of mountain-valley breezes and coal combustion plumes. The increasing concentrations of NOx and particulate matters brought by the valley breeze at daytime facilitated the formation of MHN215, OAKN359, and OAHN361, while the rising SO2 abundance and the sulfate aerosols transported by elevated emission sources affected the formation of MDCN247 at nighttime.

Amines in fine particles constitute a significant fraction of secondary organic aerosols and have adverse effects on air quality and human health. To understand the chemical composition, variation characteristics, and potential sources of fine particulate amines in the coastal area in northern China, field sampling and chemical analysis were conducted in coastal Qingdao in the winter of 2018 and 2019. A total of 15 major amines were identified and quantified by using an ultra-high-performance liquid chromatography coupled with mass spectrometry. The average concentration of total amines in PM2.5 samples was approximately 130 ng m-3. Dimethylamine was the most abundant species with average fractions of 44.8% and 65.0% in the quantified amines during the two field campaigns, followed by triethylamine (22.9% and 8.7%) and methylamine (8.3% and 4.4%). The amines in PM2.5 usually exhibited elevated concentrations in the presence of high levels of SO2 and NOx or in the condition of high relative humidity. A receptor model of positive matrix factorization was employed and seven major sources were identified, including coal combustion, industrial production, vehicle exhaust, biomass burning, agricultural activities, secondary formation, and marine emission. Surprisingly, most of 15 amines in fine particles primarily originated from the primary emissions of anthropogenic activities particularly related to coal combustion and industrial productions, which should be given close concern to address the amine pollution.

Nitrated phenols in the atmosphere are receiving increasing attentions due to their light absorption and biological toxicity. However, the partitioning characteristics of nitrated phenols among gas, particle, and aqueous phases and the dominant influencing factors remain unclear. In this work, particulate, gaseous, and cloud water samples were simultaneously collected at the summit of Mt. Tai in North China in spring, summer and winter. The contents of 11 nitrated phenols in these samples were determined with an ultra-high-performance liquid chromatograph in tandem with a mass spectrometer. The total concentrations of nitrated phenols in PM2.5 were in the range of several to dozens of ng m-3, a little lower than those measured in gas phase. The total concentrations of nitrated phenols in cloud water were in the level of hundreds of µg L-1. Among the 11 nitrated phenols, 4-nitrophenol and nitrosalicylic acids were the most dominant compounds in PM2.5, while 4-nitrophenol and 2,4-dinitrophenol were the most abundant in gas-phase and cloud water samples. During cloud events, most nitrated phenols were mainly distributed in particle phase, except dinitrophenols which were mainly distributed in gas phase. The observed concentration ratios of aqueous nitrated phenols to those in gas phase were one to two orders higher than the theoretical Henry’s law coefficients in pure water. Moreover, the measured concentrations of particulate nitrated phenols were substantially greater than the theoretically predicted values. The above results indicate that nitrated phenols potentially formed via aqueous-phase reactions inside the cloud droplets or on the surface of particles. The much higher ratios of the sum of 4-nitrophenol and 5-nitrosalicylic acid to 2,4-dinitrophenol in cloud water than those in PM2.5 further confirms the enhanced formation via aqueous processes. Overall, aqueous-phase reactions were important sources of atmospheric nitrated phenols during cloud events and had significant influences on the abundance and distributions of nitrated phenols in different phases.

Particulate organic nitrates (PONs) are among the major components of organic aerosols and affect the reactive nitrogen budget and ozone formation on regional scale. Previous laboratory and field studies have shown some preliminary evidence for the effects of anthropogenic activities on the formation of PONs. In this study, the concentrations of six kinds of PONs in rural and urban areas in the North China Plain were determined, and the seasonal and diurnal difference and effects of anthropogenic activities on their formation were investigated. The average total concentration of PONs was in the range of 113? 415 ng m- 3, contributing 0.7% ?2.8% to organic matter during the observation periods. Distinct seasonal variation was observed, with higher concentrations appearing in summer than in winter due to the large emissions of precursor BVOCs and intensive photochemical activities in the hot season. The concentration and formation of some specific PONs exhibited diurnal differences in summer, while the differences were small in other seasons. The observations showed that PONs in the North China Plain were significantly influenced by open biomass burning and coal combustion. The formation of PONs was enhanced by increased BVOCs released from biomass burning and consequently elevated levels of ozone. Industrial and residential coal combustion contributed to the increased concentrations of PONs by providing related reactants and interfaces and facilitating the formation rates of PONs.

Nitrated aromatic compounds, the ubiquitous nitrogen-containing organic pollutants, impact the environment and organisms adversely. As industrial raw materials and intermediates, nitrated aromatic compounds and their aromatic precursors are widely employed in the industrial production activities. Nevertheless, their emission from industrial waste gases has so far not been studied extensively. In this study, the concentrations of 12 nitrated aromatic compounds in the particle and gas phases downwind of 16 factories encompassing eight industries (i.e., pharmaceutical, weaving and dyeing, herbicide, explosive, painting, phenolic resin, paper pulp and polystyrene foam industries), were determined by ultrahigh-performance liquid chromatography-mass spectrometry. Their concentrations in the particle and gas phases from different factories ranged from 114.7 +/- 63.5 to 296.6 +/- 62.5 ng m(-3) and 148.7 +/- 7.4 to 309.8 +/- 26.2 ng m(-3), respectively, thus, exhibiting significantly high concentrations as compared to the background sites. Among the 12 detected species, 4-nitrophenol, 5-nitrosalicylic acid, 3-nitrosalicylic acid and 4-methyl-2,6-dinitrophenol were observed to be the predominant species, with total fractions up to 47.9-72.3% and 63.1-70.3% in the particle and gas phases, respectively. Their emission profiles with respect to the industrial activities exhibited large discrepancies as compared to the combustion sources, thus, indicating different formation mechanisms. The emission ratios of particulate nitrated aromatic compounds owing to the industrial activities were estimated between 0.5 +/- 0.2 and 4.3 +/- 1.5 ng mu g(-1), which were higher than or comparable to those from various combustion sources. The findings from this study confirm the industrial emission to be an important source of nitrated aromatic compounds in the atmosphere. The substantial emissions of nitrated aromatic compounds from various industries reported in this study provide the fundamental basis for further emission estimation and pollution control. (C) 2021 Elsevier Ltd. All rights reserved.