Stagnant Conditions Research Articles

Photochemical Mechanism and Control Strategy Optimization for Summertime Ozone Pollution in an Industrial City in the North China Plain

To investigate the characteristics and formation mechanism of ozone (O3) pollution in an industrial city, an extensive one-month field campaign focusing on O3 and its precursors (e.g., volatile organic compounds[VOC] and nitrogen oxides[NOx]) was conducted in Zibo City, a highly industrializd city in the North China Plain, in June 2021. The 0-D box model incorporating the latest explicit chemical mechanism (MCMv3.3.1) was applied using an observation dataset (e.g., VOC, NOx, HONO, and PAN) as model contraints to explore the optimal reduction strategy for O3 and its precursors. The results showed that ① during high-O3 episodes, stagnant weather conditions with high temperature and solar radiation as well as low relative humidity were observed, and oxygenated VOCs and alkenes from anthropogenic VOCs contributed the most to the total ozone formation potential and OH reactivity (k·OH). ② The in-situ O3 variation was primarily affected by local photochemical production and export process horizontal to downwind areas or vertical to the upper layer. The reduction in local emissions was essential to alleviate O3 pollution in this region. ③ During high-O3 episodes, high concentrations of ·OH (10×106 cm-3) and HO2· (14×108 cm-3) radical drove and generated a high O3 production rate (daytime peak value reached 36×10-9 h-1). The reaction pathways of HO2·+NO and ·OH+NO2 contributed the most to the in-situ gross Ox photochemical production (63%) and photochemical destruction (50%), respectively. ④ Compared to those during low-O3 episodes, the photochemical regimes during high-O3 episodes were more inclined to be considered as the NOx-limited regime. Detailed mechanism modeling based on multiple scenarios further suggested that the synergic emission reduction strategy of NOx and VOC, while focusing on NOx emission alleviation, would be practical options for controlling local O3 pollutions. This method could also provide policy-related guidance for the precise O3 pollution prevention and control in other industrialized Chinese cities.

An improved microfluidic device to enhance the enrichment factors in liquid phase microextraction: application to the simultaneous extraction of polar and non-polar acids in biological samples

A new microfluidic device to enhance the enrichment factor in miniaturized systems is proposed. The microfluidic system was design for liquid phase microextractions, and it was applied to the simultaneous extraction of acidic compounds of a wide range of polarity (0.5 < log P < 3). The device operated under stagnant acceptor phase conditions and all the operational parameters involved were optimized. Tributyl phosphate was found to be a new highly efficient supported liquid membrane to simultaneously extract analytes of very different polarities. The optimal donor and acceptor phase were pH 2 and pH 13, respectively. The donor flow rate and the extraction time were investigated simultaneously, offering great versatility with high enrichment factors (EFs). Limits of quantitation were within 0.02 and 0.09 µg mL−1 for all compounds at 10 µL min−1 as donor flow rate and 20-min extractions, offering EFs between 11 and 18 with only 200-µL sample volume consumption. The method was successfully applied to human urine samples, observing recoveries between 47 and 90% for all compounds. This new proposed microfluidic system increases the wide range of applications, especially when the analytes are present in lower concentrations in the sample.Graphical

Sandstone-hosted uranium deposits of the Colorado Plateau, USA

More than 4,000 sandstone-hosted uranium occurrences host over 1.2 billion pounds of mined and in situ U3O8 throughout the Colorado Plateau. Most of the resources are in two distinct mineral systems with deposits hosted in the Triassic Chinle and Jurassic Morrison Formations. In the Chinle mineral system, base metal sulfides typically accompany mineralization. The Morrison mineral system is characterized by V/U ratios up to 20. The uranium source was likely volcanic ash preserved as bentonitic mudstones in the Brushy Basin Member of the Morrison Formation, and lithic volcanic clasts, ash shards, and bentonitic clay in the lower part of the Chinle Formation. Vanadium originated from two possible sources: iron–titanium oxides that are extensively altered in bleached rock near deposits or from similar minerals in variably bleached red beds interbedded with and beneath the Morrison. In Chinle-hosted deposits, in addition to volcanic ash, a contributing source of both vanadium and uranium is proposed here for the first time to be underlying red beds in the Moenkopi and Cutler Formations that have undergone a cycle of reddening-bleaching-reoxidation. Transport in both systems was likely in groundwater through the more permeable sandstones and conglomerate units. The association of uranium minerals with carbonate and more rarely apatite, suggests that transport of uranium was as a carbonate or phosphate complex. The first comprehensive examination of paleoclimate, paleotopography, and subsurface structure of aquifers coupled with analysis of the geochronology of deposits suggests that that there were distinct pulses of uranium mineralization/redistribution during the period from about 259 Ma to 12 Ma when oxidized mineralizing fluids were intermittently rejuvenated in the Plateau in response to changes in tectonic regime and climate. Multiple lines of evidence indicate that deposits formed at ambient temperatures of about 25 °C to no greater than about 140 °C. In both systems, deposits formed where groundwater flow slowed and was subject to evaporative concentration. Stagnant conditions allowed for prolonged interaction of U- and V-enriched groundwater with ferrous iron-bearing reductants, such as illite and iron–titanium oxides, and more rarely organic material such as plant debris. Paragenetically late in the sequence, reducing fluids introduced additional organic matter to some deposits. Reducing fluids and introduced organic matter (now amorphous and altered by radiolysis) may originate from regional petroleum systems where peak oil and gas generation was from ∼ 82 to ∼ 5 Ma. Our novel analysis indicates that these reducing fluids bleached rock and protected affected deposits from remobilization during exposure and weathering that followed uplift of the Plateau (∼80 to 40 Ma).

Influences of meteorology on emission sources and physicochemical properties of particulate matter in Seoul, Korea during the heating period

Chemical properties of particulate matter (PM), organic aerosol (OA) properties, sources and the volatility distribution were investigated during autumn in Seoul, Korea using aerodyne high resolution time of flight aerosol mass spectrometer (HR-ToF-AMS) with a thermodenuder (TD) combined system (TD-AMS). Overall, the average PM1 + black carbon (BC) concentration was 21.49 μg/m3, ranging from 7.85 μg/m3 to 48.36 μg/m3, and the largest proportion of PM1 components was organic (54%), followed by NO3− (17%), SO42− (12%), NH4+ (9%) and BC (6%). During this period, the O/C and H/C ratios were similar to those in other studies (0.45 and 1.70, respectively), but the N/C ratio was slightly higher than that in other studies. Five organic aerosol (OA) sources were identified through positive matrix factorization (PMF) analysis, where four POAs (HOA, COA, SFOA1 and SFOA2) and one SOA (LVOOA) were identified. A distinct feature during this study was that two different combustion-related sources, SFOA1 and SFOA2 were observed. Two different SFOAs showed time-dependent features and different chemical compositions. SFOA2, which was dominant during the higher-temperature period (16.3 °C (5.1–26.6)) showed less O/C (0.41 vs 0.57) and N/C (0.033 vs 0.059) and more volatile feature than the one of SFOA1 during colder period (10.1 °C (−1.8-19.4)). It might be due to different heating activities and more intensive gas to particle parting and oxidizing processing under colder condition. Haze is also influenced by heating activities. When stagnant conditions occur with high heating activities, enhanced emission sources (SFOA1), enhanced gas-to-particle partitioning (nitrate) and the accumulation of primary OA result in severe haze conditions in urban air. This result suggests that controlling emission sources during heating seasons is still required for haze control in urban environments.

Internal corrosion of seabed ‘parked’ steel oil and gas pipelines

Seabed ‘parking’ of steel pipelines is a common practice in the oil and gas industry. For ‘wet parking’ severe internal corrosion, often at the 6 o'clock position, remains an issue, despite the use of corrosion inhibitors and biocides ostensibly to control microbiologically influenced corrosion. Biocides may have undesirable environmental consequences if eventually or accidently released. Recent findings for internal corrosion inside water injection pipelines are reviewed as these have implications for managing the internal corrosion of parked pipelines. After initial oxygen controlled corrosion longer term corrosion can occur under anaerobic conditions. This has implications for corrosion during periods of stagnant conditions and for corrosion under deposits of rusts and other debris. Microbiologically influenced corrosion can increase internal corrosion but only if the nutrients necessary for bacterial metabolism are available. Acceptably low levels of corrosion can be achieved inside ‘wet’ parked pipelines with the use of seawater with low concentrations of particulate matter and low concentrations of microbiologically-critical nutrients.

Intra- and inter-city variability of PM2.5 concentrations in Greece as determined with a low-cost sensor network

Measurements of PM2.5 concentrations in five major Greek cities over a two-year period using calibrated low-cost sensor-based particulate matter (PM) monitors (Purple Air PA-II) were combined with local meteorological parameters, synoptic patterns and air mass residence time models to investigate the factors controlling PM2.5 spatiotemporal variability over continental Greece. Fourteen sensors nodes in Athens, Patras, Ioannina, Xanthi, and Thermi (in the Metropolitan Area of Thessaloniki) were selected out of more than 100 of a countrywide network for detailed analysis. The cities have populations ranging from 65k to 3M inhabitants and cover different latitudes along the South-North axis. High correlations between the daily average PM2.5 levels were observed among all sites, indicating strong intra- and inter-city covariance of concentrations, both in cold and warm periods. Higher PM2.5 concentrations in all cities during the cold period were primarily associated with low temperatures and stagnant anticyclonic conditions, favoring the entrapment of residential heating emissions from biomass burning. Anticyclonic conditions were also connected to an increased frequency of PM2.5 episodes, exceeding the updated daily guideline value (15 μg m−3) of the World Health Organization (WHO). During the warm period, nearly uniform PM2.5 levels were encountered across continental Greece, independently of their population size. This uniformity strongly suggests the importance of long-range transport and regional secondary aerosol formation for PM2.5 during this period. Peak concentrations were associated mainly with regional northern air flows over Greece and the Balkan Peninsula. The use of the measurements from dense air quality sensor networks, provided that a robust calibration protocol and continuous data quality assurance practices are followed, appears to be an efficient tool to gain insights on the levels and variability of PM2.5 concentrations, underpinning the characterization of spatial and seasonal particularities and supporting real-time public information and warning.

Secondary aerosol formation drives atmospheric particulate matter pollution over megacities (Beijing and Seoul) in East Asia

Atmospheric particulate matter (PM) pollution in Beijing and Seoul is an urgent concern because of the dense population and the role of the capital city. This study aimed to understand haze formation over East Asia during winter by simultaneously measuring the in situ aerosol chemical composition in the two megacities. During the sampling period, a similar pollution situation characterized by extremely low SO2 (approximately 1 ppbv) and high NOx (approximately 20 ppbv) concentrations and secondary inorganic aerosol (SIA)-dominated PM was found in both cities. Nitrate dominated the inorganic components in the submicron particles in both cities and was more pronounced in Seoul than in Beijing. The enhanced SIA mass concentrations during pollution episodes were observed to be associated with an increased local atmospheric oxidation capacity (indicated by O3+NO2=Ox concentration) and ambient relative humidity under similar stagnant weather conditions. Regarding the thermodynamic equilibrium, abundant aerosol liquid water promoted the partitioning of gaseous HNO3 into its particle phase when pollution events occurred. This result emphasized the importance of local secondary aerosol formation for atmospheric PM pollution in East Asian megacities. The box model simulation of nitrate formation indicated that the homogeneous oxidation of NO2 by OH radicals was the major nitrate formation pathway in both megacities. The downward transport of nitrate from the residual layer also significantly contributed to nitrate concentrations. NOx and volatile organic compounds (VOCs) exhibited a non-linear relationship with nitrate formation. Reducing VOCs concentrations was an efficient approach to mitigate nitrate in both megacities. A reduction of more than 50% in NOx concentrations was required for the effective reduction of nitrate. This study highlighted that Beijing and Seoul were experiencing similar PM pollution situations, and nitrate reduction should be considered to improve their air quality.

Effects of tropical cyclones with different tracks on ozone pollution over the Pearl River Delta region

Tropical cyclone's activities can affect the ozone pollution characteristics to a certain extent over the Pearl River Delta (PRD) region based on different track types of tropical cyclones. In this study, we utilize the Finite Mixture Model algorithm to classify tropical cyclones which land on the South China coastal area between 2009 and 2018 into 6 track's types, and those types are land on the PRD region directly (A1 type), the east of the PRD region (B1 and B2 types) and the west of the PRD region (C1, C2 and C3 types) respectively. Combined with observation data, the results indicate that the A1 type, B1 type and B2 type tropical cyclones can increase the ozone concentration about 44.9% ∼ 65.3% in the PRD region before landfall accompanied with stagnant meteorological conditions usually, such as high temperature (>27 °C), low humidity (<80%) or weak wind (<3 m/s). And it should be emphasized that, due to the northward or northeastward deflection of the tracks, the ozone concentration in the PRD region does not decrease obviously (<10%) on the landing-day under B1 and B2 types, and ozone pollution maybe persistent longer than other types. By simulating typical cases of each track's type within WRF-Chem model coupled with process analysis method, and the results indicate that tropical cyclone's peripheral subsidence airflow is more obvious over the PRD region under A1, B1 and B2 cases before landfall, and it maybe an external condition which can limit the development of boundary layer and vertical diffusion of ozone, rather than transporting ozone downward from the upper atmosphere to the near surface level. In addition, based on process analysis result, the chemical reaction with strong radiation condition maybe the essential cause of ozone production and pollution, and the physical process can cause the ozone consumption.

Secondary Formation of Submicron and Supermicron Organic and Inorganic Aerosols in a Highly Polluted Urban Area

AbstractDifferent adverse health effects of submicron (PM1) and fine particles (PM2.5) may be attributed to their chemical differences, requiring a better understanding of size‐resolved composition. Herein, extensive online measurements were conducted across seasons in Beijing by two aerosol mass spectrometers, one of which alternately sampled PM1 and PM2.5. Source apportionment of organic aerosol (OA) indicated that traffic‐ and cooking‐related OA together accounted for ∼20%−30% of the OA mass in PM2.5, showing insignificant seasonal variations. Coal‐combustion and biomass‐burning‐related OA had minor contributions. The two secondary OA (SOA) factors together accounted for 59%−73% of the OA mass in PM2.5. The mass distributions of particulate components in PM1 and PM2.5 varied greatly across seasons. Secondary formation played a key role in particle size growth during cold seasons. During severe hazes with high aerosol liquid water content (ALWC), the supermicron mass fraction (MF1−2.5) of secondary components reached ∼40%−50% while those for primary OA remained at ∼20%. Heterogeneous uptake, aqueous processing, and dissolution likely all contributed to the enhanced concentration of secondary components, and the former two were perhaps more important. The increase of MF1−2.5 for secondary components with increasing ALWC in spring was less than that in winter, possibly due to the shorter duration of stagnant conditions limiting secondary formation. Early autumn showed higher MF1−2.5 values than cold seasons with insignificant changes as ALWC varied, plausibly explained by intensive new particle formation hindering persistent particle growth. Our results highlight the importance of heterogeneous uptake and aqueous processing in distributing SOA in supermicron mode in polluted areas.

Study on antibacterial properties of heated oyster shell particle against Bacillus subtilis spores in rainwater by response surface methodology based on central composite design.

Taiwan's oyster industry produces shell waste in abundant quantities every year. This study explored the feasibility of applying this resource as a simple and low-cost disinfectant to improve the microbial quality of harvested rainwater. Critical parameters affecting the disinfection efficacy of calcined oyster shell particles, i.e., heating temperature and duration, dosage, and contact time of the calcined shell material against Bacillus subtilis endospores in rainwater, were investigated. A central composite design of response surface methodology was employed to study the relative effects. As estimated from R2 coefficients, a quadratic model was identified to predict the response variable satisfactorily. Results indicated that the heating temperature, dosage, and contact time of the calcined material in the rainwater significantly influenced (p < 0.05) the sporicidal effect, consistent with the prior literature on calcined shells of similar nature. However, heating time had a relatively low influence on the sporicidal impact, suggesting that the rate of shell activation, i.e., conversion of the carbonate compound in the shell material to oxide, occurs rapidly at high calcination temperatures. In addition, the sterilization kinetics for heated oyster shell particles in aqueous media under stagnant storage conditions were investigated and found to be in good agreement with Hom's model.

A Study of Urban Haze and Its Association with Cold Surge and Sea Breeze for Greater Bangkok.

This study deals with haze characteristics under the influence of the cold surge and sea breeze for Greater Bangkok (GBK) in 2017-2022, including haze intensity and duration, meteorological classification for haze, and the potential effects of secondary aerosols and biomass burning. A total of 38 haze episodes and 159 haze days were identified. The episode duration varies from a single day to up to 14 days, suggesting different pathways of its formation and evolution. Short-duration episodes of 1-2 days are the most frequent with 18 episodes, and the frequency of haze episodes decreases as the haze duration increases. The increase in complexity in the formation of relatively longer episodes is suggested by a relatively higher coefficient of variation for PM2.5. Four meteorology-based types of haze episodes were classified. Type I is caused by the arrival of the cold surge in GBK, which leads to the development of stagnant conditions favorable for haze formation. Type II is induced by sea breeze, which leads to the accumulation of air pollutants due to its local recirculation and development of the thermal internal boundary layer. Type III consists of the haze episodes caused by the synergetic effect of the cold surge and sea breeze while Type IV consists of short haze episodes that are not affected by either the cold surge or sea breeze. Type II is the most frequent (15 episodes), while Type III is the most persistent and most polluted haze type. The spread of haze or region of relatively higher aerosol optical depth outside GBK in Type III is potentially due to advection and dispersion, while that in Type IV is due to short 1-day episodes potentially affected by biomass burning. Due to cold surge, the coolest and driest weather condition is found under Type I, while Type II has the most humid condition and highest recirculation factor due to the highest average sea breeze duration and penetration. The precursor ratio method suggests the potential effect of secondary aerosols on 34% of the total haze episodes. Additionally, biomass burning is found to potentially affect half of the total episodes as suggested by the examination of back trajectories and fire hotspots. Based on these results, some policy implications and future work are also suggested.

Chemical composition and potential sources of PM2.5 in Hanoi

The chemical composition of PM2.5 was monitored simultaneously at two sites, one in a general area of the city center and one at a roadside, in Hanoi, Vietnam, during August 2019–July 2020 using 220 daily (24 h) filter samples. PM mass, water soluble ions, trace elements, organic and elemental carbon and sugar anhydrides were measured. The annual average PM2.5 concentrations, 49 and 46 μg m−3 at the traffic and the general urban site, respectively, exceeded the national (25 μg m−3) and 2021 WHO limit values (5 μg m−3). Daily PM2.5 concentrations were the highest in winter when stagnant meteorological conditions prevailed. On average, half of the resolved mass was organic matter, of which about 40% was attributable to biomass burning, most likely rice straw field burning and domestic fuel combustion. One third of PM2.5 was secondary inorganic aerosol which was dominated by sulphate hence indicating a high contribution of stationary sources like coal combustion. The elemental carbon level was higher at the traffic site, except in April 2020 during the COVID-19 restrictions. Zinc was the most common trace element with high daily variations and large differences between the sites, and it often peaked with Cd, Cl− and Pb indicating contribution of industrial sources and/or coal combustion. The highest zinc concentrations appeared on a few days and likely originated from open burning of municipal solid waste. It appeared that scattered open waste and biomass burning, as well as coal combustion, are important sources causing spikes of PM2.5 pollution in Hanoi above the general levels caused by routine industrial and traffic sources, especially during stagnant winter days. Source contributions were further studied with positive matrix factorization producing six source factors: traffic (12%), local secondary inorganic aerosol (SIA, 18%), biomass burning (19%), industry (9%), long-range transported SIA (25%) and dust (17%).

Exploring the formation mechanism of fine particles in an ex-heavily polluted Northwestern city, China

Fine particle pollution is still a severe issue in the northwestern region of China where the formation mechanism of which remains ambiguous due to the limited studies there. In this study, a comprehensive study on the chemical composition and sources of PM2.5 at an ex-heavily polluted northwestern city was conducted, based on filter sampling data obtained from three consecutive winter campaigns during 2020–2022. The average PM2.5 during the three winter campaigns were 170.9 ± 66.4, 249.0 ± 75.7, and 200.9 ± 47.6 μg/m3, respectively, with the daily maximum value of PM2.5 exceeds 400 μg/m3 under stagnant meteorological conditions charactered by high relative humidity (>60 %) and low wind speed (<1 m/s). The major chemical components in PM2.5 were found to be inorganic aerosol (55.2 %) that mainly constituted by sulfate (24.2 %), and mineral dust (14.9 %); while the carbonous species contributed a minor fraction (∼13 %). In addition, (NH4)2SO4 and NH4NO3 were the dominate contributors to appearance of low visibility (<3 km) which together accounting for over 85 % of light extinction coefficient (bext) during heavy polluted period. Source appointment of fine particles was then conducted by applying the positive matrix factorization method, and the primary sources were resolved to be coal combustion (27.7 %) and biomass burning (18.6 %), followed by industrial dust (16.2 %), residential combustion (15.3 %), traffic emissions (11.9 %) and dust aerosol (10.4 %). To explore the potential formation mechanism of fine particle pollution, the chemical evolution pattern combined with gaseous pollutants and meteorological parameters were further analyzed, which refine the important role of primary emissions in the forming of high sulfate aerosol loading, while secondary formation was largely suppressed during the winter period that totally different from those reported in the developed regions of China, thus indicating more effort should be paid on the reduction of primary particles emissions in the northwestern cities than on its gaseous percussors.

Flooding tolerance in Rice: adaptive mechanism and marker-assisted selection breeding approaches.

Natural and man-made ecosystems worldwide are subjected to flooding, which is a form of environmental stress. Genetic variability in the plant response to flooding involves variations in metabolism, architecture, and elongation development that are related with a low oxygen escape strategy and an opposing quiescence scheme that enables prolonged submergence endurance. Flooding is typically associated with a decrease in O2 in the cells, which is especially severe when photosynthesis is absent or limited, leading to significant annual yield losses globally. Over the past two decades, considerable advancements have been made in understanding of mechanisms of rice adaptation and tolerance to flooding/submergence. The mapping and identification of Sub1 QTL have led to the development of marker-assisted selection (MAS) breeding approach to improve flooding-tolerant rice varieties in submergence-prone ecosystems. The Sub1 incorporated in rice varieties showed tolerance during flash flood, but not during stagnant conditions. Hence, gene pyramiding techniques can be applied to combine/stack multiple resistant genes for developing flood-resilient rice varieties for different types of flooding stresses. This review contains an update on the latest advances in understanding the molecular mechanisms, metabolic adaptions, and genetic factors governing rice flooding tolerance. A better understanding of molecular genetics and adaptation mechanisms that enhance flood-tolerant varieties under different flooding regimes was also discussed.

Leaching of microplastics from PVC pipes under stagnant conditions

Leaching of microplastics from PVC pipes under stagnant conditions

Heavy metal, organic matter, and disinfection byproduct release from drinking water pipe scales under stagnant conditions

Physico-chemical and microbiological processes occurring in water distribution systems (WDSs) can result in the formation of pipe scales which accumulate harmful metals.

Peran Latar Belakang Keluarga Terhadap Keberlangsungan Usaha dan Kesejahteraan Pengrajin Perak di Kabupaten Gianyar

The silver industry in Gianyar Regency is a business that has been carried out for generations, so it is not surprising that Gianyar Regency is known as a center for silver crafts. However, currently the condition of silver handicraft SMEs is in a stagnant condition and even tends to decline, especially with the Covid-19 pandemic so that it can have an impact on business continuity and the welfare of craftsmen. The purpose of this study was to examine the effect of family background on business continuity and the welfare of silver craftsmen in Gianyar Regency. The population in this study is 235 silver handicraft IKM. The research sample was determined using a purposive sampling method resulting in a total sample of 95 silver handicraft IKM. This study uses descriptive analysis techniques and quantitative analysis techniques with structural equation models or Structural Equation Modeling (SEM), especially Partial Least Square (PLS) with an analytical tool, namely SmartPLS. The results showed that (1) family background had a significant positive direct effect on the sustainability of the silver craftsmen's business in Gianyar Regency; (2) Family background and business continuity have a significant positive direct effect on the welfare of silver craftsmen in Gianyar Regency; and (3) business continuity mediating the influence of family background on the welfare of silver craftsmen in Gianyar Regency.

Tropospheric ozone and its natural precursors impacted by climatic changes in emission and dynamics

Climate change plus ozone pollution is a lethal combination that adversely affects human health, agriculture productivity, ecosystems, and the world economy. Currently, there is a growing concern that climate change may aggravate ozone pollution even after reducing anthropogenic precursor source activities. Part of it may be due to temperature-enhanced natural precursor emissions of ozone, increased stratospheric–tropospheric exchange of ozone, more frequent periods with meteorologically stagnant conditions favouring pollution build-up, changes in wetland methane emissions, and enhanced concentrations of atmospheric carbon dioxide. The quantification of climate change and ozone levels involves complex chemical, radiative, biogenic, and transport processes and feedback that are difficult to fully comprehend. Further, the fact that ozone is a short-lived climate forcer and a potent greenhouse gas provides a feedback loop and makes climate-ozone links even more multifaceted. This review examines the up-to-date understanding of the processes regulating tropospheric ozone from regional to global scales and the associated climate connections. We explore the recent findings in ozone precursor emissions from natural sources, ozone formation chemistry, its transport on hemispheric scales, future plausible ozone concentrations in different shared socioeconomic pathways, and changes in the radiative forcing of ozone. The review demonstrates the challenges and limitations associated with climate-ozone linkages and their incorporation in models, which are due to uncertainties in magnitude and signs of projected precursor emissions in response to future climate change and also due to the difference in models.

Modeling volatilization emissions of soil-applied pesticides under agricultural field conditions

Pesticides can volatilize from treated soil to the atmosphere causing increased environmental pollution and human exposure. Exposure assessment to airborne pesticides requires reasonable predictions of pesticide emissions. Understanding the volatilization behavior due to changes in environmental conditions can help in assessing the risk uncertainty and designing better mitigation strategies. In this study, we developed a mechanistic model that can be used to predict the hourly volatilization emissions from pesticide-treated soil at different environmental conditions. Pesticide properties and local environmental conditions drive the transport processes at the soil-air interface within the model.The numerical model simultaneously calculates the soil fluxes of heat, moisture, and pesticide at the soil-air interface with inputs of hourly meteorological data. The initial condition of pesticide concentration in soil is obtained from the applied mass during treatment. The numerical model was compared with an analytical model and with field observations for a soil injected fumigant and two surface applied pesticides.The model performance of 14 pesticides under stagnant conditions against the Jury's analytical model showed reasonable agreement with values for the coefficient of determination (R2) ranging from 0.76 to 0.99. The model was a good predictor of the field-scale volatilization of a fumigant (1,3-dichloropropene) application when compared to observations (R=20.8). Both the timing of the peak and the temporal variability of the measured volatilization of the fumigant were captured by the model when the fumigant was incorporated at a depth of 46 cm in the soil column. The model also showed reasonable agreement with the measured volatilization of two surface-treated pesticides, though site-specific meteorological data was unavailable for these observations.The results indicate that the modeling approach could be a useful tool to evaluate the impact of location-specific meteorological conditions on the field volatility of pesticides and determine the emissions for risk assessment.

How interfacial dynamics controls drainage pore-invasion patterns in porous media

Immiscible two-phase flow through porous media is composed of a series of pore invasions; however, the consequences of pore-scale processes on macroscopic fluid front behavior remain to be clarified. In this work, we perform an analytical and experimental investigation of front behavior and pore invasions dynamics during drainage for various viscosity ratios and capillary numbers. We use a microfluidic setup that includes a fully controlled pore-doublet geometry to isolate and explore pore-invasion mechanisms. We apply a model based on volume-averaged Navier–Stokes equations to capture interface dynamics. Different invasion mechanisms are characterized and correlated with front behavior for various flow conditions. For the viscous flow regime, a succession of continuous pore invasions is observed, leaving a thick layer of wetting phase behind at pore curvatures. Abrupt interfacial jumps, followed by an apparent stagnant condition, are observed for the capillary flow regime. We identified a new regime, called crossover flow regime, for which pore invasion shows a mixed behavior between capillary and viscous dominated regimes. The global front behavior is predicted based on the numerical simulation and experimental results for all flow regimes.