scholarly journals Oxidation pathways and emission sources of atmospheric particulate nitrate in Seoul: based on δ<sup>15</sup>N and Δ <sup>17</sup>O of PM<sub>2.5</sub>

2021 ◽  
Author(s):  
Saehee Lim ◽  
Meehye Lee ◽  
Joel Savarino ◽  
Paolo Laj
Keyword(s):  
Critical Role ◽  
Liquid Water Content ◽  
Nox Emission ◽  
Photochemical Oxidation ◽  
Biomass Combustion ◽  
Emission Sources ◽  
Relative Contribution ◽  
Haze Pollution ◽  
The Mean ◽  
Oxidation Ratio

Abstract. PM2.5 haze pollution driven by secondary inorganic NO3− has been a great concern in East Asia. It is, therefore, imperative to identify its sources and oxidation processes, for which nitrogen and oxygen stable isotopes are powerful tracers. Here, we determined the δ15N (NO3−) and Δ17O (NO3−) of PM2.5 in Seoul from 2018 to 2019, and estimated quantitatively the relative contribution of oxidation pathways for particulate NO3− and major NOx emission sources. In the range of PM2.5 mass concentration from 7.5 g m−3 (summer) to 139.0 g m−3 (winter), the mean δ15N was −0.7 ± 3.3 ‰ and 3.8 ± 3.7 ‰, and the mean Δ17O was 23.2 ± 2.2 ‰ and 27.7 ± 2.2 ‰ in the summer and winter, respectively. While OH oxidation was the dominant pathway for NO3− during the summer (87 %), nighttime formation via N2O5 and NO3 was more important (38 %) during the winter, when aerosol liquid water content (AWLC) and nitrogen oxidation ratio (NOR) were higher. Interestingly, the highest Δ17O was coupled with the lowest δ 15N and highest NOR in record-breaking winter PM2.5 episodes, revealing the critical role of photochemical oxidation process in severe winter haze development. For NOx sources, vehicle emissions were confirmed as a main contributor, followed by biomass combustion from various activities. The contribution from biogenic soil and coal combustion was slightly increased in summer and winter, respectively. Our results built on multiple-isotope approach provide the first explicit evidence for NO3− formation processes and major NOx emission sources in Seoul megacity and suggest an effective mitigation measure to improve PM2.5 pollution.

scholarly journals Speciated atmospheric mercury on haze and non-haze days in an inland city in China

2016 ◽  
Vol 16 (21) ◽  
pp. 13807-13821 ◽  
Author(s):  
Qianqian Hong ◽  
Zhouqing Xie ◽  
Cheng Liu ◽  
Feiyue Wang ◽  
Pinhua Xie ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Central China ◽  
Photochemical Oxidation ◽  
Model Calculations ◽  
Enhanced Production ◽  
Haze Pollution ◽  
The Mean ◽  
Haze Days

Abstract. Long-term continuous measurements of speciated atmospheric mercury were conducted from July 2013 to June 2014 in Hefei, a midlatitude inland city in eastern central China that experiences frequent haze pollution. The mean concentrations (±standard deviation) of gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM) and particle-bound mercury (PBM) were 3.95 ± 1.93 ng m−3, 2.49 ± 2.41 and 23.3 ± 90.8 pg m−3, respectively, on non-haze days, and 4.74 ± 1.62 ng m−3, 4.32 ± 8.36 and 60.2 ± 131.4 pg m−3, respectively, on haze days. Potential source contribution function (PSCF) analysis suggested that atmospheric mercury pollution on haze days was caused primarily by local emissions, instead of via long-range transport. The poorer mixing conditions on haze days also favored the accumulation of atmospheric mercury. Compared to GEM and GOM, PBM was especially sensitive to haze pollution. The mean PBM concentration on haze days was 2.5 times that on non-haze days due to elevated concentrations of particulate matter. PBM also showed a clear seasonal trend; its concentration was the highest in fall and winter, decreased rapidly in spring and was the lowest in summer, following the same order in the frequency of haze days in different seasons. On both non-haze and haze days, GOM concentrations remained low at night, but increased rapidly just before sunrise, which could be due to diurnal variation in air exchange between the boundary layer and free troposphere. However, non-haze and haze days showed different trends in daytime GEM and GOM concentrations. On non-haze days, GEM and GOM declined synchronously through the afternoon, probably due to the retreat of the free tropospheric air as the height of the atmospheric boundary layer increases. In contrast, on haze days, GOM and GEM showed opposite trends with the highest GOM and lowest GEM observed in the afternoon, suggesting the occurrence of photochemical oxidation. This is supported by simple box-model calculations, which showed that oxidation of GEM to GOM does occur and that the transport of free tropospheric GOM alone is not large enough to account for the observed increase in daytime GOM. Our results further postulate that NO2 aggregation with the HgOH intermediate may be a potential mechanism for the enhanced production of GOM during daytime.

scholarly journals Dome effect of black carbon and its key influencing factors: A one-dimensional modelling study

2017 ◽  
Author(s):  
Zilin Wang ◽  
Xin Huang ◽  
Aijun Ding
Keyword(s):  
Boundary Layer ◽  
Air Pollution ◽  
Black Carbon ◽  
Rural Areas ◽  
Land Surface ◽  
Critical Role ◽  
Aerosol Layer ◽  
Near Surface ◽  
Haze Pollution ◽  
The Impact

Abstract. Black carbon (BC) has been identified to play a critical role in aerosol-planet boundary layer (PBL) interaction and further deterioration of near-surface air pollution in megacities, which has been named as its dome effect. However, the impacts of key factors that influence this effect, such as the vertical distribution and aging processes of BC, and also the underlying land surface, have not been quantitatively explored yet. Here, based on available in-situ measurements of meteorology and atmospheric aerosols together with the meteorology-chemistry online coupled model, WRF-Chem, we conduct a set of parallel simulations to quantify the roles of these factors in influencing the BC's dome effect and surface haze pollution, and discuss the main implications of the results to air pollution mitigation in China. We found that the impact of BC on PBL is very sensitive to the altitude of aerosol layer. The upper level BC, especially those near the capping inversion, is more essential in suppressing the PBL height and weakening the turbulence mixing. The dome effect of BC tends to be significantly intensified as BC aerosol mixed with scattering aerosols during winter haze events, resulting in a decrease of PBL height by more than 25 %. In addition, the dome effect is more substantial (up to 15 %) in rural areas than that in the urban areas with the same BC loading, indicating an unexpected regional impact of such kind of effect to air quality in countryside. This study suggests that China's regional air pollution would greatly benefit from BC emission reductions, especially those from the elevated sources from the chimneys and also the domestic combustions in rural areas, through weakening the aerosol-boundary layer interactions that triggered by BC.

scholarly journals Speciated Atmospheric Mercury during Haze and Non-haze Days in an Inland City in China

2016 ◽  
Author(s):  
Qianqian Hong ◽  
Zhouqing Xie ◽  
Cheng Liu ◽  
Feiyue Wang ◽  
Pinhua Xie ◽  
...  
Keyword(s):  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Central China ◽  
Mercury Emissions ◽  
Gaseous Elemental Mercury ◽  
Enhanced Production ◽  
Mercury Transport ◽  
Haze Pollution ◽  
The Mean ◽  
Haze Days

Abstract. Long-term continuous measurements of speciated atmospheric mercury were conducted at Hefei, a mid-latitude inland city in east central China, from July 2013 to June 2014. The mean concentrations (± standard deviation) of gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and particle-bound mercury (PBM) were 3.95 ± 1.93 ng m−3, 2.49 ± 2.41 pg m−3 and 23.3 ± 90.8 pg m−3, respectively, during non-haze days, and 4.74 ± 1.62 ng m−3, 4.32 ± 8.36 pg m−3 and 60.2 ± 131.4 pg m−3, respectively, during haze days. Potential source contribution function (PSCF) analysis suggested that the atmospheric mercury pollution during haze days was caused primarily by local mercury emissions, instead of via long-range mercury transport. In addition, the disadvantageous diffussion during haze days will also enhance the level of atmospheric mercury. Compared to the GEM and RGM, change in PBM was more sensitive to the haze pollution. The mean PBM concentration during haze days was 2.5 times that during non-haze days due to elevated concentrations of particulate matter. A remarkable seasonal trend in PBM was observed with concentration decreasing in the following order in response to the frequency of haze days: autumn, winter, spring, summer. A distinct diurnal relationship was found between GEM and RGM during haze days, with the peak values of RGM coinciding with the decline in GEM. Using HgOH as an intermediate product during GEM oxidation, our results suggest that NO2 aggregation with HgOH could explain the enhanced production of RGM during the daytime in haze days. Increasing level of NOx will potentially accelerate the oxidation of GEM despite the decrease of solar radiation.

Distribution and Heritability of Recurrent Ear Infections

1997 ◽  
Vol 106 (8) ◽  
pp. 624-632 ◽  
Author(s):  
Kari J. Kvaerner ◽  
Jennifer R. Harris ◽  
Kristian Tambs ◽  
Per Magnus
Keyword(s):  
Structural Equation ◽  
Genetic Factors ◽  
Age Of Onset ◽  
Population Based ◽  
Equation Modeling ◽  
Relative Contribution ◽  
Genes And Environment ◽  
Ear Infections ◽  
The Mean ◽  
Familial Environment

The distribution of recurrent ear infections was obtained from a population-based sample of 2,750 pairs of Norwegian twins born between 1967 and 1974. The lifetime prevalence of self-reported recurrent ear infections was 8.9%, with a significant predominance of female cases. The mean age of onset was 4.2 years, with a gradual decrease in occurrence from 2 to 7 years of age. Among monozygotic pairs, the rate of tetrachoric correlation between co-twins was almost identical in males (0.73, SE 0.08) and females (0.74, SE 0.06), but among the dizygotic pairs the correlation was clearly higher in males (0.53, SE 0.12) than in females (0.20, SE 0.12). The value in the unlike-sexed dizygotic twins (0.25, SE 0.05) was intermediate to that of the like-sexed male and female dizygotic pairs. The relative contribution of genes and environment to variability in the predisposition to develop otitis media was estimated by means of structural equation modeling. Variation in liability to ear infections was mainly explained by additive genetic and dominance factors in females, for whom heritability was estimated at 74%. The remaining 26% of the variation in liability was explained by individual environmental factors. In males, 45% of the variation could be accounted for by genetic factors, 29% by common familial environment, and the remaining 26% by individual environmental effects.

Seasonal and Geographic Variation in the Species Composition and Size of Prey Consumed by Grey Seals (Halichoerus grypus) on the Scotian Shelf

1993 ◽  
Vol 50 (8) ◽  
pp. 1768-1778 ◽  
Author(s):  
W. D. Bowen ◽  
J. W. Lawson ◽  
B. Beck
Keyword(s):  
Atlantic Cod ◽  
Halichoerus Grypus ◽  
Scotian Shelf ◽  
Sand Lance ◽  
Atlantic Mackerel ◽  
Relative Contribution ◽  
Wet Weight ◽  
The Mean ◽  
Silver Hake ◽  
Commercial Size

The grey seal (Halichoerus grypus) population on the Scotian Shelf has grown significantly over the past 20 yr, thus increasing the potential for competitive interactions between grey seals and fisheries. The relative contribution (percent wet weight) and size of prey eaten were estimated from otoliths and squid beaks recovered from 143 stomachs that contained food of the 528 collected from 1988 to 1990. Although 22 taxa were found, only four species (Atlantic herring, silver hake, Atlantic cod, and squid) accounted for 80% of the estimated weight of food eaten. The mean length of prey eaten ranged from 19 to 35 cm for six species. Only 17% of the cod and none of the pollock and squid eaten were of the length taken in commercial fisheries. However, about 80% of the silver hake and herring eaten were of commercial size. Offshore at Sable Island, northern sand lance, silver hake, and squid (in order of importance) accounted for 86.1% of the wet weight ingested by seals during summer; sand lance and cod accounted for 96.1% of prey eaten in winter. At inshore locations, herring, cod, and pollock made up 90% of the diet in summer; Atlantic mackerel, cod, squid, and herring made up 83% of the diet in winter.

scholarly journals Relative contribution of non-structural protein 1 in dengue pathogenesis

2020 ◽  
Author(s):  
Pei Xuan Lee ◽  
Donald Heng Rong Ting ◽  
Clement Peng Hee Boey ◽  
Eunice Tze Xin Tan ◽  
Janice Zuo Hui Chia ◽  
...  
Keyword(s):  
Critical Role ◽  
Health Concern ◽  
Structural Protein ◽  
Promising Candidate ◽  
Relative Contribution ◽  
Structural Region ◽  
Strain Dependent ◽  
Pro Inflammatory Cytokines

AbstractDengue is a major public health concern in the tropical and sub-tropical world with no effective treatment. The controversial live attenuated virus vaccine Dengvaxia has boosted the pursuit of sub-unit vaccine approaches, and the non-structural protein 1 (NS1) has recently emerged as a promising candidate. However, we found that NS1 immunization or passive transfer of NS1 antibodies failed to confer protection in symptomatic dengue mouse models using two non mouse-adapted DENV2 strains from the Cosmopolitan genotype that currently circulates in South-East Asia. Furthermore, exogenous administration of purified NS1 did not worsen in vivo vascular leakage in sub-lethally infected mice, thereby supporting that NS1 does not play a critical role in the pathogenesis of these DENV2 strains. Virus chimerization approaches indicated that the prME structural region, but not NS1, plays a critical role in driving in vivo fitness and virulence of the virus, through induction of key pro-inflammatory cytokines. This work highlights that the pathogenic role of NS1 is DENV strain-dependent, which warrants re-evaluation of NS1 as a universal dengue vaccine candidate.

scholarly journals Verifying Operational Forecasts of Land–Sea-Breeze and Boundary Layer Mixing Processes

2020 ◽  
Vol 35 (4) ◽  
pp. 1427-1445
Author(s):  
Ewan Short
Keyword(s):  
Boundary Layer ◽  
Diurnal Cycle ◽  
Spatial Scales ◽  
Sea Breeze ◽  
Absolute Error ◽  
Wind Fields ◽  
Mixing Processes ◽  
Relative Contribution ◽  
The Mean ◽  
Diurnal Wind

AbstractForecasters working for Australia’s Bureau of Meteorology (BoM) produce a 7-day forecast in two key steps: first they choose a model guidance dataset to base the forecast on, and then they use graphical software to manually edit these data. Two types of edits are commonly made to the wind fields that aim to improve how the influences of boundary layer mixing and land–sea-breeze processes are represented in the forecast. In this study the diurnally varying component of the BoM’s official wind forecast is compared with that of station observations and unedited model guidance datasets. Coastal locations across Australia over June, July, and August 2018 are considered, with data aggregated over three spatial scales. The edited forecast produces a lower mean absolute error than model guidance at the coarsest spatial scale (over 50 000 km2), and achieves lower seasonal biases over all spatial scales. However, the edited forecast only reduces errors or biases at particular times and locations, and rarely produces lower errors or biases than all model guidance products simultaneously. To better understand physical reasons for biases in the mean diurnal wind cycles, modified ellipses are fitted to the seasonally averaged diurnal wind temporal hodographs. Biases in the official forecast diurnal cycle vary with location for multiple reasons, including biases in the directions that sea breezes approach coastlines, amplitude biases, and disagreement in the relative contribution of sea-breeze and boundary layer mixing processes to the mean diurnal cycle.

scholarly journals Zinc deficiency may play a crucial role in dialysis-associated bacterial infections

2020 ◽  
Vol 11 (1) ◽  
pp. e9-e9
Author(s):  
Zahra Lotfi ◽  
Abbas Ali Zeraati ◽  
Elaheh Dashti ◽  
Tina Zeraati ◽  
Maryam Arghiany ◽  
...  
Keyword(s):  
Zinc Deficiency ◽  
Bacterial Infections ◽  
Critical Role ◽  
Serum Zinc ◽  
Zinc Level ◽  
Healthy Individuals ◽  
Mortality And Morbidity ◽  
Increased Risk ◽  
The Mean

Introduction: Systemic bacterial infections are a common cause of mortality and morbidity in hemodialysis patients. Zinc has a critical role in several immune system functions. Patients who have enough amounts of zinc are able to better face infections caused by various pathogens in comparison to those with zinc insufficiency Objective We sought to assess the role of zinc deficiency in dialysis-associated bacterial infections. Patients and Methods: Eighty-Three adult patients with end-stage renal disease (ESRD) on hemodialysis including 43 patients with bacterial infectious complications and 40 non-infected patients as well as 41 healthy individuals were enrolled. Clinical data, laboratory values including serum zinc level and imaging findings were collected. SPSS was utilized to analyze the data with a significance cutoff set at P < 0.05. Results: Out of 124 participants, 80 (64.51%) were males and 44 (35.49%) were females. The mean age of infected hemodialysis group, non-infected hemodialysis group, and healthy controls were 50.8 ± 16.25, 49.1 ± 18.1, and 56.3 ± 18.2 years, respectively. Catheter site infection (37.3%) and urinary tract infection (30.2%) were the most common infections. The mean serum zinc concentration was significantly lower in the infected patients, compared to non-infected patients and healthy individuals (P < 0.001). Conclusion: The ESRD patients on hemodialysis have lower serum zinc levels which are associated with increased risk of bacterial infection. The role of screening for zinc deficiency and use of supplemental zinc in these patients need to be studied.

scholarly journals Assessing the Contribution of Seasonality, Tides, and Microbial Processing to Dissolved Organic Matter Composition Variability in a Southeastern U.S. Estuary

2021 ◽  
Vol 8 ◽  
Author(s):  
Rachel P. Martineac ◽  
Alexey V. Vorobev ◽  
Mary Ann Moran ◽  
Patricia M. Medeiros
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Critical Role ◽  
Bacterial Cells ◽  
Secondary Importance ◽  
Relative Contribution ◽  
Doc Concentration ◽  
Compositional Changes ◽  
Dom Composition

Uncovering which biogeochemical processes have a critical role controlling dissolved organic matter (DOM) compositional changes in complex estuarine environments remains a challenge. In this context, the aim of this study is to characterize the dominant patterns of variability modifying the DOM composition in an estuary off the Southeastern U.S. We collected water samples during three seasons (July and October 2014 and April 2015) at both high and low tides and conducted short- (1 day) and long-term (60 days) dark incubations. Samples were analyzed for bulk DOC concentration, and optical (CDOM) and molecular (FT-ICR MS) compositions and bacterial cells were collected for metatranscriptomics. Results show that the dominant pattern of variability in DOM composition occurs at seasonal scales, likely associated with the seasonality of river discharge. After seasonal variations, long-term biodegradation was found to be comparatively more important in the fall, while tidal variability was the second most important factor correlated to DOM composition in spring, when the freshwater content in the estuary was high. Over shorter time scales, however, the influence of microbial processing was small. Microbial data revealed a similar pattern, with variability in gene expression occurring primarily at the seasonal scale and tidal influence being of secondary importance. Our analyses suggest that future changes in the seasonal delivery of freshwater to this system have the potential to significantly impact DOM composition. Changes in residence time may also be important, helping control the relative contribution of tides and long-term biodegradation to DOM compositional changes in the estuary.

Experimental study on NOx emission characteristics of oxy-biomass combustion

2018 ◽  
Vol 199 ◽  
pp. 400-410 ◽  
Author(s):  
Imran Ali Shah ◽  
Xiang Gou ◽  
Qiyan Zhang ◽  
Jinxiang Wu ◽  
Enyu Wang ◽  
...  
Keyword(s):  
Experimental Study ◽  
Nox Emission ◽  
Biomass Combustion ◽  
Emission Characteristics
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