High Levels Of NO Research Articles

Recent increase in NO2 levels in the southeast of the Iberian Peninsula

We report the evolution of tropospheric NO2 over the south-east of the Iberian Peninsula from 2005 to 2017. We have used hourly NO2 levels measured at air-quality stations in urban and suburban environments. Annual averages ranged between 14 and 45 μg m−3, with peaks above 200 μg m−3. A monthly variation was observed, with higher concentrations in cold months (40–60 μg m−3) and lower levels in the warm season (13–17 μg m−3). A diurnal pattern was found in urban and suburban areas. The upward trend in NO2 observed during the whole period contrasts with the upward trend reported in 2013–2017. The NO2 tropospheric column levels measured by the Ozone Monitoring Instrument over the Iberian Peninsula indicated a similar behaviour; nevertheless, the largest Spanish metropolitan areas did not show this increase. The mean sea level pressure and wind field data of ERA5 (European Centre for Medium-Range Weather Forecasts) were used to investigate the weather conditions, the NO2 outputs of the Copernicus Monitoring Services being used for the assessment of the NO2 spatial distribution. NO2 regional events, with concentrations in the range 140–150 μg m−3, and which occurred both in the winter and summer season under anticyclonic conditions, are also described. A local origin is identified in winter, whereas in summer, they are associated with a high-pressure system that blocks Mediterranean outflows towards the Atlantic Ocean. The high NO2 levels are attributed mainly to two factors: i) local emissions, rather than contributions from the western Mediterranean (or even North Africa), and ii) an increase in the pressure gradient between the Atlantic and the Mediterranean pressure systems, associated with a decrease in wind speed, was found during the last five years compared with the previous eight. Meteorological and chemical changes in mid-latitudes associated with global warming should also be investigated in the future.

Associations of gestational and the first year of life exposure to ambient air pollution with childhood eczema in Hubei, China.

Whether exposure to air pollution is associated with the increased incidence of childhood eczema is controversial. Only a few previous researches about the relationship between gestational and early-life exposures to ambient air pollutants and childhood eczema were conducted in China, and there is a lack of studies in Hubei province. This study aimed to explore the associations between air pollution exposure in gestation and the first year of life and childhood eczema. From November to December 2017, a total of 3383 children aged 3-6years were recruited from 12 kindergartens in Hubei, China; 3167 were included in the final analysis. Parent-reported data involved with childhood eczema was inquired by questionnaire, and the concentrations of NO2, PM2.5, and PM10 were acquired from air quality monitoring stations which were the nearest to the twelve kindergartens. A binary logistic regression model was used to evaluate the associations of period-mean concentrations of individual pollutant exposure with childhood eczema. Of the 3167 children, 848 (26.8%) had a history of doctor-diagnosed eczema. After adjusting for the covariates, high levels of NO2, PM2.5, and PM10 exposures were significantly associated with a positive increase in risk of childhood eczema during the gestational period and the first year of life. In the gestational period, the estimate OR in the 3rd and 4th quartiles of NO2 was 1.256 and 1.496, respectively. During the first year of life, the estimate OR in the 3rd and 4th quartiles of NO2 was 1.371 and 1.335, respectively. Our study indicated that the gestational period and the first year of life exposures to high levels of ambient NO2, PM2.5, and PM10 were significantly associated with increased eczema among preschool children. Some effective measures of prevention and intervention could be developed for preschool children.

Burial practice and its effect on groundwater pollution in Maiduguri, Nigeria.

Cemeteries in Nigeria have never been perceived as having a significant potential contamination to the environment and are often located within residential setups. This work presents a study of special interest, because up till now, there are no known publications in the north-eastern states of Nigeria that investigated the relationship between cemeteries and the natural environment. The objective was to investigate whether burial practices affect the groundwater within the vicinity of an active municipal cemetery in the Gwange area of the Maiduguri metropolis, Borno State, Nigeria. Groundwater quality measurement from boreholes located at varying radial distances from the cemetery was also conducted. The result was compared with that of WHO and showed evidence of attenuation with distance. The method of burial is a chemical-free method and dictated by local culture in the area. The site is underlain by a sedimentary rock of the Chad Formation and is characterized by coarse-grained soils of high permeability coefficient (1.04 × 10-4-2.38 × 10-4cm/s). The soil sample was composed of 3.2 to 8.4% fines which fall beneath the standard of 30% that is considered adequate for natural attenuation of contaminants. The soils were poorly graded and exhibit non-plastic properties. The grave invert, being predominantly higher than 1m, seems to have significantly influenced the low levels or the absence of contaminants especially cations in the groundwater sample. The high levels of pH (9.5), EC (1874μs/cm), NO3 (67.4mg/l), NO2 (0.92mg/l), PO4 (344.5mg/l), and NH4 (1.03mg/l) in groundwater samples (especially the cemetery borehole) are an indication that higher interment density over time presents a significant threat to groundwater quality.

Reduction of GHG emissions by utilizing biomass co-firing in a swirl-stabilized furnace

This study presents the numerical investigation of co-firing behaviour of pulverized straw particles with coal in air and O2/CO2 mixtures. Validation is conducted in a semi-technical once-through 30 kW swirl-stabilized furnace. Reference air-fuel (21% O2) and oxy-fuel (30% O2) cases were considered for four different coal/straw ratios (100% coal, 20% straw, 50% straw and 100% straw). AVL Fire is used as a CFD modelling tool. A comprehensive grid independency test was conducted considering three different grid sizes. Ignition performance, emission characteristics, heating profile, residence time were evaluated for different fuel ratios under air and oxy-fuel conditions. This work has shown that no significant changes occur to the fundamental combustion characteristics for straw compared to coal when burned in the O2/CO2 atmosphere to air firing case. It was found that with 20% straw sharing, sensible performances were observed similar to that of 100% coal combustion. Also a critical analytical analysis was conducted to investigate the heating performance for straw particle of different sizes (100 μm, 330 μm and 1000 μm). The heating profiles show significant differences between the three particle sizes assuming isothermal temperature gradient and heating by both radiation and convection. It is seen that the variation of the level of SO2 is not significant between air and oxy-firing cases. However, slightly less amount of SO2 is predicted in oxy-firing case. The reduction in NO is due to the effects of higher NO levels in the flue gas promoting gas-phase reduction, significantly higher levels of CO in the flame zone and the usage of a high-NOx burner in combination. The heating profiles for different size of straw particle suggest that there is a definite influence on the overall performance of the furnace. Larger particle do not ignite properly due to lower residence time leading to lower burnout. The possibility of burnout of the larger straw particle size is less due to less residence time in air-firing compared to oxy-firing case.

Investigation of NO2 Formation Kinetics in Dual-Fuel Engines With Lean Premixed Methane–Air Charge

A dual fuel engine concept with lean premixed methane–air charge ignited by a diesel pilot flame is highly promising for reducing NOx and soot emissions. One drawback of this combustion method, however, is the high nitric dioxide (NO2) emissions observed at certain operating points. The conditions leading to increased NO2 formation have been investigated using a batch reactor model in cantera. It has been found that the high emission levels of NO2 can be traced back to the mixing of small amounts of quenched CH4 with NO from the hot combustion zones followed by postoxidation in the presence of O2, requiring that the temperatures are within a certain range. NO2 formation in the exhaust duct of a test engine has been modeled and compared to the experimental results. The well-stirred reactor model has been used that calculates the steady-state of a uniform composition for a certain residence time. An appropriate reaction mechanism that considers the effect of NO/NO2 on methane oxidation at low temperature levels has been used. The numerical results of NO–NO2 conversion in the duct at low temperature levels show good agreement with the experimental results. The partial oxidation of CH4 can be predicted well. It can be shown that methane oxidation in the presence of NO/NO2 at low temperature levels is enhanced via the reaction steps CH3+NO2⇌CH3O+NO and CH3O2+NO⇌CH3O+NO2. In addition, the elementary reaction HO2+NO⇌NO2+OH is the important NO oxidizing step.

Association between air pollution and asthma exacerbations in Badalona, Barcelona (Spain), 2008–2016

Introduction and objectiveAir pollution has been widely associated with respiratory diseases. Nevertheless, association between air pollution and exacerbations of asthma in our area has been less studied. To analyse the effect of air pollution on exacerbations of asthma in Badalona. Material and methodsThis was an observational study conducted in Badalona. The number of daily hospital admissions and accident and emergency visits related to exacerbation of asthma between 2008 and 2016 was obtained. We used simple Poisson regressions to test the effects of daily mean temperature, atmospheric pressure, relative humidity, and NO2, SO2 and CO levels on asthma-related emergencies and hospitalisations the same day and 1–4 days after. All p-values were corrected for multiple comparisons. ResultsThe number of hospitalisations was associated with low temperature (lags 0–4) and higher levels of NO2 (lags 0, 1, 2 and 4) and atmospheric pressure (lags 2 and 3). The number of accident and emergency visits was associated with low temperature (lags 0–4) and higher levels of NO2 (lags 2, 3 and 4). ConclusionsThe number of accident and emergency visits and hospitalisations for exacerbation of asthma is associated with higher levels of NO2 and with lower temperatures.

Yersinia pseudotuberculosis Thermostable Toxin Dysregulates the Functional Activity of Two Types of Phagocytes in the Holothurian Eupentacta fraudatrix

The effect of a thermostable toxin of Yersinia pseudotuberculosis (in comparison with that of dexamethasone) on the functional activities of two types of phagocytes (P1 and P2) was studied in the holothurian Eupentacta fraudatrix. A high level of NO was shown to be a marker of intact P1 cells, while the high activity of arginase was a marker of P2 cells. The antioxidant defense in the P1 type was more pronounced than that of the P2 type. At the same time, the toxin inhibited the functional activity (generation of reactive oxygen species) of P1 phagocytes after 1 h of incubation and induced primarily the activity of P2 phagocytes, compared to that of P1 cells, after 24 h. In contrast to dexamethasone, which induced the transformation of the P1 phenotype into the P2 phenotype, the toxin promoted the mutual acquisition of the phenotype features by these two types of phagocytes. An analogy between the P1 and P2 phagocytes of the holothurian and M1 and M2 macrophages is discussed.

Cyclic NO2:NOx ratio from a diesel engine undergoing transient load steps

As the control of real driving emissions continues to increase in importance, the importance of understanding emission formation mechanisms during engine transients similarly increases. Knowledge of the NO2/NOx ratio emitted from a diesel engine is necessary, particularly for ensuring optimum performance of NOx aftertreatment systems. In this work, cycle-to-cycle NO and NOx emissions have been measured using a Cambustion CLD500, and the cyclic NO2/NOx ratio calculated as a high-speed light-duty diesel engine undergoes transient steps in load, while all other engine parameters are held constant across a wide range of operating conditions with and without exhaust gas recirculation. The results show that changes in NO and NOx, and hence NO2/NOx ratio, are instantaneous upon a step change in engine load. NO2/NOx ratios have been observed in line with previously reported results, although at the lightest engine loads and at high levels of exhaust gas recirculation, higher levels of NO2 than have been previously reported in the literature are observed.

Intradermal Application of Crotamine Induces Inflammatory and Immunological Changes In Vivo.

Crotamine is a single-chain polypeptide with cell-penetrating properties, which is considered a promising molecule for clinical use. Nevertheless, its biosafety data are still scarce. Herein, we assessed the in vivo proinflammatory properties of crotamine, including its local effect and systemic serum parameters. Sixty male Wistar rats were intradermically injected with 200, 400 and 800 µg crotamine and analyzed after 1, 3 and 7 days. Local effect of crotamine was assessed by determination of MPO and NAG activities, NO levels and angiogenesis. Systemic inflammatory response was assessed by determination of IL-10, TNF-α, CRP, NO, TBARS and SH groups. Crotamine induced macrophages and neutrophils chemotaxis as evidenced by the upregulation of both NAG (0.5–0.6 OD/mg) and MPO (0.1–0.2 OD/mg) activities, on the first and third day of analysis, respectively. High levels of NO were observed for all concentrations and time-points. Moreover, 800 μg crotamine resulted in serum NO (64.7 μM) and local tissue NO (58.5 μM) levels higher or equivalent to those recorded for their respective histamine controls (55.7 μM and 59.0 μM). Crotamine also induced a significant angiogenic response compared to histamine. Systemically, crotamine induced a progressive increase in serum CRP levels up to the third day of analysis (22.4–45.8 mg/mL), which was significantly greater than control values. Crotamine (400 μg) also caused an increase in serum TNF-α, in the first day of analysis (1095.4 pg/mL), however a significant increase in IL-10 (122.2 pg/mL) was also recorded for the same time-point, suggesting the induction of an anti-inflammatory effect. Finally, crotamine changed the systemic redox state by inducing gradual increase in serum levels of TBARS (1.0–1.8 μM/mL) and decrease in SH levels (124.7–19.5 μM/mL) throughout the experimental period of analysis. In summary, rats intradermally injected with crotamine presented local and systemic acute inflammatory responses similarly to histamine, which limits crotamine therapeutic use on its original form.

Oxidative stress in ryegrass growing under different air pollution levels and its likely effects on pollen allergenicity

In the present work, for the first time in the literature, the relationship between the degree of air pollution, the physiological state of the plants and the allergenic capacity of the pollen they produce has been studied. The physiological state of Lolium perenne plants growing in two cities with a high degree of traffic, but with different levels of air pollution, Madrid and Ciudad Real, have been explored. The photosynthetic efficiency of the plants through the emission of fluorescence of PSII, the degree of oxidative stress (enzymatic activities related to the ascorbate-glutathione cycle), the redox state (reduced and oxidized forms of ascorbate and glutathione) and the concentration of malondialdehyde have been evaluated. During the development period of the plants, Madrid had higher levels of NO2 and SO2 than Ciudad Real. The greater degree of air pollution suffered by Madrid plants was reflected on a lower photosynthetic efficiency and a greater degree of oxidative stress. In addition, NADPH oxidase activity and H2O2 levels in pollen from Madrid were significantly higher, suggesting a likely higher allergenic capacity of this pollen associated to a higher air pollution.

In vitro differentiation of tracheary elements is induced by suppression of Arabidopsis phytoglobins

Differentiation of tracheary elements (TEs) in vitro was affected by the expression level of the Arabidopsis thaliana Col-0 phytoglobins (Pgbs). Over-expression of Pgb1 or Pgb2 (35S:Pgb1 or 35S:Pgb2 lines) reduced the differentiation process while suppression of either Pgb (Pgb1-RNAi or pgb2 lines) enhanced the production of TEs. The inductive effect of Pgb suppression on TE differentiation was linked to the reduced expression of the transcription factor MYC2. Suppression of this gene, observed under conditions of high NO levels or low Pgb expression, was sufficient to promote TE differentiation, while its over-expression abolished the promotive effect of Pgb suppression on the differentiation process. Cells in which MYC2 was mutated accumulated ethylene which induced the expression of the homeodomain-leucine zipper (HD-Zip) III ATHB8. Production of ethylene was reduced in cells over-expressing MYC2 in a WT or a pgb mutant background. While stabilizing procambial cell specification, ATHB8 in known to activate downstream components triggering programmed cell death (PCD) and modifications of cell wall components, required steps of the TE differentiation process. Collectively, we provide evidence that in addition to their recognised participation in stress responses, Pgbs may play a key role in the specification of cell fate during development.

Impact of precursor gases and meteorological variables on satellite-estimated near-surface sulfate and nitrate concentrations over the North China Plain

Previous studies exploring the impact of precursor emissions and meteorological variables on PM2.5 concentrations were typically conducted over a short period and in urban environments. In this analysis, near-surface sulfate and nitrate mass concentrations at a 10-km resolution over the North China Plain (NCP) from 2006 to 2014 were first obtained based on satellite aerosol optical depth (AOD) data and the global 3D chemical transport model (GEOS-Chem) in combination with vertical profiles from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). Using ground-based PM2.5 component concentrations, our satellite-based model yielded correlation coefficients (r) of 0.72 for sulfate and 0.70 for nitrate. Second, the spatiotemporal patterns of the chemical composition and corresponding precursor gases collected from the Ozone Monitoring Instrument (OMI) during the study period were analyzed. The highest levels of nitrate (∼30 μg/m3) and sulfate (∼25 μg/m3) were concentrated in Hebei, Shandong, Henan and Beijing, and the monthly variations of nitrate and NO2 presented a strong correlation coefficient (0.67). Inter-annual changes of nitrate and NO2 exhibited increasing trends of 1.43%/yr and 1.60%/yr, respectively. In contrast, sulfate and SO2 decreased at rates of 3.5%/yr and 0.76%/yr, respectively, and presented a negative correlation (−0.54). Third, the relationships between the components or precursor gases and relative humidity (RH), planetary boundary layer height (PBLH), temperature (TEM) and wind speed (WS) were compared. The results showed that high levels of NO2 were usually accompanied by stable atmospheric conditions (i.e., low TEM, shallow PBLH, low RH and mild WS). Moreover, the nitrate concentration was often dependent on NO2, and they showed similar characteristics with meteorological factors. PBLH and WS had the greatest influence on nitrate concentrations, whereas the effects of RH and WS varied seasonally. Under beneficial conditions, i.e., high TEM, RH and PBLH and low WS, SO2 rapidly converted to sulfate and fluctuated inversely with the sulfate concentration. Overall, high nitrate levels were primarily associated with anthropogenic causes (i.e., extensive emissions), whereas meteorological conditions have a greater effect on the formation of sulfate concentrations than emissions.

Comparison of secondary organic aerosol (SOA) formation during o-, m-, and p-xylene photooxidation

Despite extensive effort to characterize xylene-isomer-derived secondary organic aerosols (SOAs) over the past decade, differences in SOA composition among xylene isomers, and their relative contributions to SOA formation remain poorly understood. Herein, we reinvestigated the photooxidation of o-, m-, and p-xylene under two limiting NO conditions. Dicarbonyls, TBM (the acronym of C3-trione, 2,3-butanedione, and 3-methyl-2-oxiranecarbaldehyde with the same [M+H]+m/z value of 87), and highly oxidized species (HOS), based on the m/z 61 fragment, were determined to be the predominant SOA components arising from xylene photooxidation; however, their relative contributions to SOA formation appear to depend on the xylene substitution pattern. In the initial stages of the reaction, dicarbonyls present in the SOA from m- and p-xylene, and TBM in the SOA from o-xylene, were the main contributors to new particle formation (NPF). Based on their significant levels of formation, HOS and TBM were characterized to be critical components that enhance SOA growth. High NO levels were noted to inhibit the formation of C3-trione and 2,3-butanedione in the SOA from m- and o-xylene, whereas the formation of 3-methyl-2-oxiranecarbaldehyde during p-xylene photooxidation was significantly promoted. These results reveal that the substitution pattern of the xylene isomer is a significant factor that determines these differences. In addition, decreases in the levels of dicarbonyls and TBM during NPF and the formation of HOS in the presence of high levels of NO may be important factors that lead to lower SOA yields compared to those obtained under low-NO conditions. This work contributes to a better understanding of the formation mechanism of xylene-derived SOAs.

An in situ flow tube system for direct measurement of N<sub>2</sub>O<sub>5</sub> heterogeneous uptake coefficients in polluted environments

Abstract. The heterogeneous reactivity of dinitrogen pentoxide (N2O5) on ambient aerosols plays a key role in the atmospheric fate of NOx and formation of secondary pollutants. To better understand the reactive uptake of N2O5 on complex ambient aerosols, an in situ experimental approach to direct measurement of N2O5 uptake coefficient (γN2O5) was developed for application in environments with high, variable ambient precursors. The method utilizes an aerosol flow tube reactor coupled with an iterative chemical box model to derive γN2O5 from the depletion of synthetically generated N2O5 when mixed with ambient aerosols. Laboratory tests and model simulations were performed to characterize the system and the factors affecting γN2O5, including mean residence time, wall loss variability with relative humidity (RH), and N2O5 formation and titration with high levels of NO, NOx, and O3. The overall uncertainty was estimated to be 37 %–40 % at γN2O5 of 0.03 for RH varying from 20 % to 70 %. The results indicate that this flow tube coupled with the iterative model method could be buffered to NO concentrations below 8 ppbv and against air mass fluctuations switching between aerosol and non-aerosol modes. The system was then deployed in the field to test its applicability under conditions of high ambient NO2 and O3 and fresh NO emission. The results demonstrate that the iterative model improved the accuracy of γN2O5 calculations in polluted environments and thus support the further field deployment of the system to study the impacts of heterogeneous N2O5 reactivity on photochemistry and aerosol formation.

Tyrosine residues of bovine serum albumin play an important role in protecting SH-SY5Y cells against heme/H2O2/NO2--induced damage.

Serum albumin (SA) has been shown to act as a heme scavenger in hemolysis and can protect cell against the toxic effect of heme. However, the mechanism of SA in heme detoxification is not well understood. Interestingly, increasing studies indicate that heme/H2O2-dependent reaction is unlikely to be the principal cause of heme toxicity in excessive intravascular hemolysis conditions. Moreover, high levels of NO2- and NO3- were also found in patients with severe hemolytic diseases, which seem to involve in heme toxic effect as well. Therefore, we proposed that studying the protection mechanism of SA against the heme/H2O2/NO2--induced cytotoxicity may be more consistent with free heme-associated disorder pathologies. In this study, we tested the hypotheses that tyrosine residues of bovine serum albumin (BSA) play a prominent role in detoxifying heme in SH-SY5Y cells. Both BSA and tyrosine modified BSA (BSA-T) were used to explore this protective mechanism. Most of cellular injury (oxidative and nitrative damage) induced by heme/H2O2/NO2- were prevented by pretreatment with an equimolar concentration of BSA or BSA-T, and BSA was found more efficient than BSA-T. Meanwhile, BSA or BSA-T binding to heme is not accompanied by a decrease of heme's peroxidase activity. Collectively, these data suggest that the protecting effect of BSA against heme-induced damage in the intravascular hemolysis diseases is not accomplished by preventing the primary reactivity of heme with H2O2, but by trapping radical through special residues such as tyrosine to render other important protein less damaged.

Developmental toxicity assessment of thalidomide and its derivatives lenalidomide and pomalidomide in zebrafish embryos

Herein, we reported the cytotoxicity, NO-releasing property, and apoptosis induced ability of two series of novel nitric oxide-releasing spirolactone-type diterpenoid derivatives (10a–f and 15a–f). All the title compounds were more potent than oridonin (7) and parent compound (9 or 14) against human tumor Bel-7402, K562, MGC-803 and CaEs-17 cells. SARs were concluded based on above data. Compound 15d exhibited the strongest antiproliferative activity with the IC50 of 0.86, 1.74, 1.16 and 3.75 μM, respectively, and could produce high level (above 25 μM) of NO at the time point of 60 min. Further mechanism evaluation showed that 15d could induce S phase cell cycle arrest and apoptosis at low micromolar concentrations in Bel-7402 cells via mitochondria-related pathways. It was expected that the remarkable biological profile of the synthetic NO-releasing spirolactone-type diterpenoid analogs make them possible as promising candidates for the development of anticancer agents.

Asociación entre la contaminación ambiental y las agudizaciones de asma bronquial en Badalona (Barcelona), 2008-2016

Introduction and objectiveAir pollution has been widely associated with respiratory diseases. Nevertheless, association between air pollution and exacerbations of asthma in our area has been less studied. To analyse the effect of air pollution on exacerbations of asthma in Badalona. Material and methodsThis was an observational study conducted in Badalona. The number of daily hospital admissions and accident and emergency visits related to exacerbation of asthma between 2008 and 2016 was obtained. We used simple Poisson regressions to test the effects of daily mean temperature, atmospheric pressure, relative humidity, and NO2, SO2 and CO levels on asthma-related emergencies and hospitalisations the same day and 1-4 days after. All p-values were corrected for multiple comparisons. ResultsThe number of hospitalisations was associated with low temperature (lags 0 to 4) and higher levels of NO2 (lags 0, 1, 2 and 4) and atmospheric pressure (lags 2 and 3). The number of accident and emergency visits was associated with low temperature (lags 0 to 4) and higher levels of NO2 (lags 2, 3 and 4). ConclusionsThe number of accident and emergency visits and hospitalisations for exacerbation of asthma is associated with higher levels of NO2 and with lower temperatures.

Association between early prenatal exposure to ambient air pollution and birth defects: evidence from newborns in Xi'an, China.

The aim of this study was to investigate an association between birth defects and exposure to sulfur dioxide (SO2), nitrogen dioxide (NO2) and particles ≤10 μm in an aerodynamic diameter (PM10) during early pregnancy in Xi'an, China. Birth defect data were from the Birth Defects Monitoring System of Xi'an, and data on ambient air pollutants during 2010-15 were from the Xi'an Environmental Protection Bureau. A generalized additive model (GAM) was used to investigate the relationship between birth defects and ambient air pollutants. Among the 8865 cases with birth defects analyzed, the overall incidence of birth defects was 117.33 per 10 000 infants. Ambient air pollutant exposure during the first trimester increased the risk of birth defects by 10.3% per 10 μg/m3 increment of NO2 and 3.4% per 10 μg/m3 increment of PM10. No significant association was found between birth defects and SO2. Moreover, NO2 increased risk of neural tube defects, congenital heart disease, congenital polydactyly, cleft palate, digestive system abnormalities and gastroschisis, and PM10 was associated with congenital heart disease and cleft lip with or without cleft palate. Chinese women should avoid exposure to high levels of NO2 and PM10 during the first 3 months of pregnancy.

Variations and sources of nitrous acid (HONO) during a severe pollution episode in Beijing in winter 2016

HONO is an important precursor of OH radical and plays a key role in atmospheric chemistry, but its source and formation mechanism remain uncertain, especially during complex atmospheric pollution processes. In this study, HONO mixing ratios were measured by a custom-made instrument during a severe pollution event from 16 to 23 December 2016, at an urban area of Beijing. The measurement was divided into three periods: I (haze), II (severe haze) and III (clean), according to the levels of PM2.5. This pollution episode was characterized by high levels of NO (75 ± 39 and 94 ± 40 ppbV during periods I and II, respectively) and HONO (up to 10.7 ppbV). During the nighttime, the average heterogeneous conversion frequency during the two haze periods were estimated to be 0.0058 and 0.0146 h−1, and it was not the important way to form HONO. Vehicle emissions contributed 52% (±16)% and 40% (±18)% to ambient HONO at nighttime during periods I and II. The contribution of homogeneous reaction of NO with OH should be reconsidered under high-NOx conditions and could be noticeable to HONO sources during this pollution event. Furthermore, HONO was positively correlated with PM2.5 during periods I and II, suggesting a potential chemical link between HONO and haze particles.

Assessment of a high-resolution NOX emission inventory using satellite observations: A case study of southern Jiangsu, China

To evaluate the bottom-up NOX emission inventories with different data sources and spatial scales, an updated product of tropospheric NO2 vertical column densities (VCDs) from Ozone Monitoring Instrument (OMI), POMINO, was applied in chemistry transport modeling (CTM) and Gaussian function model for southern Jiangsu, a typical developed and polluted region in eastern China. Compared to the national emission inventory (MEIC), better correlation was found between spatial distributions of the high-resolution provincial inventory (JS) and POMINO VCDs. When applied in CTM, the simulated VCDs using JS were closer to POMINO data than those using MEIC, indicating the advantage of the provincial inventory that incorporated detailed information of individual plants. The simulated VCDs, however, were generally larger than observed ones, particularly for regions with high NO2 levels, partly because the improved NOX control measures for power sector were not fully considered in both national and provincial inventories. The “top-down” NOX emissions were estimated for four cities/city combinations in southern Jiangsu, using a Gaussian function model based on POMINO NO2 VCDs. The results were found to be most consistent with the estimates in JS among bottom-up inventories with different data sources. To further harmonize emissions and satellite observations at relatively small spatial scale, the on-line emission measurement data for individual plants are recommended for emission inventory development, and the products of satellite observation data with finer horizontal resolution are encouraged.