Photo-Induced Heterogeneous Chemistry of Reactive Species on Aerosol Surfaces: Using Photo-Fragmentation Laser Induced Fluorescence for the Measurement of Nitrous Acid Production from Titanium Dioxide Aerosols

2020 ◽  
Author(s):  
Joanna Dyson ◽  
Graham Boustead ◽  
Lauren Fleming ◽  
Mark Blitz ◽  
Daniel Stone ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Nitrous Acid ◽  
Laser Induced Fluorescence ◽  
Heterogeneous Chemistry ◽  
Sources And Sinks ◽  
Atmospheric Species ◽  
Highly Sensitive ◽  
Secondary Pollutants ◽  
Reactive Uptake Coefficient

<p>The hydroxyl radical (OH) is the main oxidant in the troposphere and is vitally important for its role in the removal of greenhouse gases such as methane from the atmosphere. Moreover, the OH radical also has a role in the formation of secondary pollutants such as tropospheric ozone and secondary organic aerosols (SOAs), formed via the oxidation of volatile organic compounds (VOCs). Understanding the sources and sinks of OH within the atmosphere is therefore crucial in order to fully understand the concentration and distribution of trace atmospheric species associated with climate change and poor air quality.</p><p>In polluted environments the dominant source of OH to initiate oxidation is the photolysis of nitrous acid (HONO). Current atmospheric chemistry models underestimate the concentration of HONO indicating a potential missing tropospheric source of HONO. There is a large uncertainty in the production of HONO from the contribution and role of aerosols and heterogeneous chemistry both under light and dark conditions.</p><p>In order to investigate the missing source of HONO from illuminated aerosols and determine its atmospheric relevance, a photo-fragmentation laser induced fluorescence (PF-LIF) instrument coupled to an aerosol flow tube system has been constructed. The PF-LIF instrument provides a highly sensitive measurement of HONO by fragmenting it into OH which is then detected in a low pressure cell by LIF. The aim of this system is to measure the rate of production of HONO from illuminated aerosol surfaces.</p><p>We will present an overview of the PF-LIF instrument and results from experiments investigating the reactive uptake of NO<sub>2</sub> by TiO<sub>2</sub> aerosols to produce HONO. The change in the reactive uptake coefficient as a function of NO<sub>2</sub> concentration and the dependence of HONO production on relative humidity and light intensity will also be discussed.   </p>

Key Role of Equilibrium HONO Concentration over the Soil 

2021 ◽  
Author(s):  
Fengxia Bao ◽  
Hang Su ◽  
Uwe Kuhn ◽  
Yafang Cheng
Keyword(s):  
Gas Phase ◽  
Hydroxyl Radicals ◽  
Nitrous Acid ◽  
Measurement Method ◽  
Oxidative Capacity ◽  
Sources And Sinks ◽  
Dynamic Chamber ◽  
Open Question ◽  
Actinic Radiation

<p>Nitrous acid (HONO) is an important component of the nitrogen cycle. HONO can also be rapidly photolyzed by actinic radiation to form hydroxyl radicals (OH) and exerts a primary influence on the oxidative capacity of the atmosphere. The sources and sinks of HONO, however, are not fully understood. Soil nitrite, produced via nitrification or denitrification, is an important source for the atmospheric HONO production. [HONO]*, the equilibrium gas phase HONO concentration over the soil, has been suggested as key to understanding the environmental effects of soil fluxes of HONO (Su et al., 2011). But if and how [HONO]* may exist and vary remains an open question. In this project, a measurement method using a dynamic chamber has been developed to derive [HONO]* and the atmospheric soil fluxes of HONO can accordingly be quantified. We demonstrate the existence of [HONO]* and determine its variation in the course of soil drying processes. We show that when [HONO]* is higher than the atmospheric HONO concentration, HONO will be released from soil; otherwise, HONO will be deposited on soil. This work advances the understanding of soil HONO emissions, and the evaluation of its impact on the atmospheric oxidizing capacity and the nitrogen cycling.</p>

Corrigendum to: Atmospheric variation of nitrous acid at different sites in Europe

2007 ◽  
Vol 4 (5) ◽  
pp. 364 ◽  
Author(s):  
Karin Acker ◽  
Detlev Möller
Keyword(s):  
Hydroxyl Radical ◽  
Nitrous Acid ◽  
Field Experiments ◽  
Early Morning ◽  
Mixing Ratio ◽  
Gas Phase Reactions ◽  
Sources And Sinks ◽  
Mixing Ratios ◽  
Secondary Pollutants ◽  
Rural Sites

Environmental context. Nitrous acid (HNO2) is an important source of the hydroxyl radical (OH.), the most important daytime oxidising species that contributes to the formation of ozone as well as of other secondary pollutants in the troposphere. Understanding the sources and sinks of HNO2 is of crucial interest for accurately modelling the chemical composition of the troposphere and predicting future trace gas concentrations. Abstract. Nitrous acid and several other atmospheric components and variables were continuously measured during complex field experiments at seven different suburban and rural sites in Europe. HNO2 is mainly formed by heterogeneous processes and is often accumulated in the nighttime boundary layer. Our results confirm that the photolysis of HNO2 is an important source of the hydroxyl radical, not only in the early morning hours but also throughout the entire day, and is often comparable with the contribution of ozone and formaldehyde photolysis. At all research sites unexpectedly high HNO2 mixing ratios were observed during the daytime (up to several hundred ppt, or pmol mol-1). Moreover, surprisingly, the HNO2 mixing ratio at the three mountain sites often showed a broad maximum or several distinct peaks at midday and lower mixing ratios during the night. Assuming a quickly established photo-equilibrium between the known significant gas phase reactions, only a few ppt HNO2 should be present around noon. The ratio of known sources to sinks indicates a missing daytime HNO2 source of 160-2600 ppt h-1 to make up the balance. Based on these values and on production mechanisms proposed in the literature we hypothesise that the daytime mixing ratio levels may only be explained by a fast electron transfer onto adsorbed NO2.

Atmospheric variation of nitrous acid at different sites in Europe

2007 ◽  
Vol 4 (4) ◽  
pp. 242 ◽  
Author(s):  
Karin Acker ◽  
Detlev Möller
Keyword(s):  
Hydroxyl Radical ◽  
Nitrous Acid ◽  
Field Experiments ◽  
Early Morning ◽  
Mixing Ratio ◽  
Gas Phase Reactions ◽  
Sources And Sinks ◽  
Mixing Ratios ◽  
Secondary Pollutants ◽  
Rural Sites

Environmental context. Nitrous acid (HNO2) is an important source of the hydroxyl radical (OH•), the most important daytime oxidising species that contributes to the formation of ozone as well as of other secondary pollutants in the troposphere. Understanding the sources and sinks of HNO2 is of crucial interest for accurately modelling the chemical composition of the troposphere and predicting future trace gas concentrations. Abstract. Nitrous acid and several other atmospheric components and variables were continuously measured during complex field experiments at seven different suburban and rural sites in Europe. HNO2 is mainly formed by heterogeneous processes and is often accumulated in the nighttime boundary layer. Our results confirm that the photolysis of HNO2 is an important source of the hydroxyl radical, not only in the early morning hours but also throughout the entire day, and is often comparable with the contribution of ozone and formaldehyde photolysis. At all research sites unexpectedly high HNO2 mixing ratios were observed during the daytime (up to several hundred ppt, or pmol mol–1). Moreover, surprisingly, the HNO2 mixing ratio at the three mountain sites often showed a broad maximum or several distinct peaks at midday and lower mixing ratios during the night. Assuming a quickly established photo-equilibrium between the known significant gas phase reactions, only a few ppt HNO2 should be present around noon. The ratio of known sources to sinks indicates a missing daytime HNO2 source of 160–2600 ppt h–1 to make up the balance. Based on these values and on production mechanisms proposed in the literature we hypothesise that the daytime mixing ratio levels may only be explained by a fast electron transfer onto adsorbed NO2.

scholarly journals Measurement of atmospheric nitrous acid at Blodgett Forest during BEARPEX2007

2010 ◽  
Vol 10 (3) ◽  
pp. 7383-7419 ◽  
Author(s):  
X. Ren ◽  
H. Gao ◽  
X. Zhou ◽  
J. D. Crounse ◽  
P. O. Wennberg ◽  
...  
Keyword(s):  
Nitrous Acid ◽  
Chemical Ionization ◽  
Lower Troposphere ◽  
Late Summer ◽  
Atmospheric Oxidation ◽  
Ionization Mass ◽  
Oxidation Processes ◽  
Highly Sensitive ◽  
Good Agreement

Abstract. Nitrous acid (HONO) is an important precursor of the hydroxyl radical (OH) in the lower troposphere. Understanding HONO chemistry, particularly its sources and contribution to HOx (=OH+HO2) production, is very important for understanding atmospheric oxidation processes. A highly sensitive instrument for detecting atmospheric HONO based on aqueous long path absorption photometry (LOPAP) was deployed in the Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX) at Blodgett Forest, California in late summer 2007. The median diurnal variation shows minimum HONO levels of about 20–30 pptv during the day and maximum levels of about 60–70 pptv at night, a diurnal pattern quite different from the results at various other forested sites. Measured HONO/NO2 ratios for a 24-h period ranged from 0.05 to 0.13 with a mean ratio of 0.07. Speciation of reactive nitrogen compounds (NOy) indicates that HONO accounted for only ~3% of total NOy. However, due to the fast HONO loss through photolysis, a strong HONO source (1.59 ppbv day−1) existed in this environment in order to sustain the observed HONO levels, indicating the significant role of HONO in NOy cycling. The LOPAP HONO measurements were compared to the HONO measurements made with a Chemical Ionization Mass Spectrometer (CIMS) over a three-day period. Good agreement was obtained between the measurements from the two different techniques. Using the expansive suite of photochemical and meteorological measurements, the contribution of HONO photolysis to HOx budget was calculated to be relatively small (6%) compared to results from other forested sites. The lower HONO mixing ratio and thus its smaller contribution to HOx production are attributed to the unique meteorological conditions and low acid precipitation at Blodgett Forest. Further studies of HONO in this kind of environment are needed to test this hypothesis and to improve our understanding of atmospheric oxidation and nitrogen budget.

scholarly journals Measurement of atmospheric nitrous acid at Bodgett Forest during BEARPEX2007

2010 ◽  
Vol 10 (13) ◽  
pp. 6283-6294 ◽  
Author(s):  
X. Ren ◽  
H. Gao ◽  
X. Zhou ◽  
J. D. Crounse ◽  
P. O. Wennberg ◽  
...  
Keyword(s):  
Nitrous Acid ◽  
Chemical Ionization ◽  
Lower Troposphere ◽  
Late Summer ◽  
Atmospheric Oxidation ◽  
Ionization Mass ◽  
Wet Chemistry ◽  
Highly Sensitive ◽  
Good Agreement

Abstract. Nitrous acid (HONO) is an important precursor of the hydroxyl radical (OH) in the lower troposphere. Understanding HONO chemistry, particularly its sources and contribution to HOx (=OH+HO2) production, is very important for understanding atmospheric oxidation processes. A highly sensitive instrument for detecting atmospheric HONO based on wet chemistry followed by liquid waveguide long path absorption photometry was deployed in the Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX) at Blodgett Forest, California in late summer 2007. The median diurnal variation shows minimum HONO levels of about 20–30 pptv during the day and maximum levels of about 60–70 pptv at night, a diurnal pattern quite different from the results at various other forested sites. Measured HONO/NO2 ratios for a 24-h period ranged from 0.05 to 0.13 with a mean ratio of 0.07. Speciation of reactive nitrogen compounds (NOy) indicates that HONO accounted for only ~3% of total NOy. However, due to the fast HONO loss through photolysis, a strong HONO source (1.59 ppbv day−1) existed in this environment in order to sustain the observed HONO levels, indicating the significant role of HONO in NOy cycling. The wet chemistry HONO measurements were compared to the HONO measurements made with a Chemical Ionization Mass Spectrometer (CIMS) over a three-day period. Good agreement was obtained between the measurements from the two different techniques. Using the expansive suite of photochemical and meteorological measurements, the contribution of HONO photolysis to HOx budget was calculated to be relatively small (6%) compared to results from other forested sites. The lower HONO mixing ratio and thus its smaller contribution to HOx production are attributed to the unique meteorological conditions and low acid precipitation at Blodgett Forest. Further studies of HONO in this kind of environment are needed to test this hypothesis and to improve our understanding of atmospheric oxidation and nitrogen budget.

Highly sensitive adolescent benefits in positive school transitions: Evidence for vantage sensitivity in Japanese high-schoolers

2020 ◽  
Author(s):  
Shuhei Iimura
Keyword(s):  
High School ◽  
Statistical Power ◽  
Environmental Influences ◽  
Differential Susceptibility ◽  
School Transition ◽  
Well Being ◽  
Crossover Point ◽  
Japanese Adolescents ◽  
Highly Sensitive

Some researchers indicate that the transition to high school deflects adolescent developmental trajectories. Others assert it provides a new possibility for the promotion of adolescents’ socioemotional well-being. One critical view missing in such claims is that individual variabilities interact with environmental influences. We employed the framework of Differential Susceptibility Theory, which postulates that individual susceptibilities moderate external influences for better and for worse. In order to clarify the mechanism of adolescents’ differential adjustments, this paper investigated the role of sensory-processing sensitivity using the Japanese version of Highly Sensitive Child Scale for Adolescence (J-HSCS), and tested whether the diathesis-stress model or the differential susceptibility model best describes students’ socioemotional adjustment across their high school transition. The current paper used the two-wave data collected from Japanese adolescents aged from 14 to 15 years (n = 412, 50% girls). In Study 1, we investigated the replicability of psychometric properties of J-HSCS. The results supported previous findings, indicating its validity for the bifactor model. In Study 2, we utilized confirmatory competitive model testing, which maximizes statistical power by parameterizing the crossover point to allow a direct comparison of alternative models. The results indicated that neither the diathesis-stress nor the differential susceptibility models fitted the data. Rather, a strong vantage sensitivity model was revealed, suggesting that highly susceptible adolescents disproportionately benefitted from a positive school transition over their counterparts. This finding signified the role of adolescents’ sensitivity to environmental influences and the importance of considering its moderation under person x environment interactions.

scholarly journals Role of MRI evaluation in acute secondary inability to walk in children

2021 ◽  
Vol 52 (1) ◽  
Author(s):  
K. H. Sedeek ◽  
K. Aboualfotouh ◽  
S. M. Hassanein ◽  
N. M. Osman ◽  
M. H. Shalaby
Keyword(s):  
Transverse Myelitis ◽  
High Sensitivity ◽  
Acute Disseminated Encephalomyelitis ◽  
Limb Weakness ◽  
Non Invasive ◽  
Highly Sensitive ◽  
Common Causes ◽  
Bilateral Lower Limb ◽  
Severity Of The Disease

Abstract Background Acute bilateral lower limb weakness is a common problem in children which necessitates a rapid method for diagnosis. MRI is a non-invasive imaging technique that produces high-quality images of the internal structure of the brain and spinal cord. Results MRI was very helpful in reaching rapid and prompt diagnosis in children with acute inability to walk. Acute disseminated encephalomyelitis (ADEM), Guillain–Barré syndrome (GBS), and acute transverse myelitis (ATM) were the most common causes in our study. MRI proved to be of high sensitivity in detecting the lesions and reaching the diagnosis in ADEM and GBS; however, there was no significant relation between the lesions’ size, enhancement pattern, and severity of the disease or prognosis, yet in ATM the site of the lesion and number of cord segment affection were significantly related to the severity of the disease and prognosis. Conclusion MRI is a quick tool to reach the diagnosis of children with acute secondary inability to walk, and to eliminate other differential diagnosis which is essential for proper treatment and rapid full recovery. It is highly sensitive in detecting the lesions, their site and size.

scholarly journals Interphotoreceptor coupling: an evolutionary perspective

2021 ◽  
Author(s):  
Lorenzo Cangiano ◽  
Sabrina Asteriti
Keyword(s):  
Visual Information ◽  
Signal To Noise Ratio ◽  
Electrical Coupling ◽  
Physiological Role ◽  
Cellular Processes ◽  
Contact Points ◽  
Highly Sensitive ◽  
The Many ◽  
The Impact

AbstractIn the vertebrate retina, signals generated by cones of different spectral preference and by highly sensitive rod photoreceptors interact at various levels to extract salient visual information. The first opportunity for such interaction is offered by electrical coupling of the photoreceptors themselves, which is mediated by gap junctions located at the contact points of specialised cellular processes: synaptic terminals, telodendria and radial fins. Here, we examine the evolutionary pressures for and against interphotoreceptor coupling, which are likely to have shaped how coupling is deployed in different species. The impact of coupling on signal to noise ratio, spatial acuity, contrast sensitivity, absolute and increment threshold, retinal signal flow and colour discrimination is discussed while emphasising available data from a variety of vertebrate models spanning from lampreys to primates. We highlight the many gaps in our knowledge, persisting discrepancies in the literature, as well as some major unanswered questions on the actual extent and physiological role of cone-cone, rod-cone and rod-rod communication. Lastly, we point toward limited but intriguing evidence suggestive of the ancestral form of coupling among ciliary photoreceptors.

Atmospheric Chemistry of Perfluoroaldehydes (CxF2x+1CHO) and Fluorotelomer Aldehydes (CxF2x+1CH2CHO):  Quantification of the Important Role of Photolysis

2006 ◽  
Vol 110 (43) ◽  
pp. 11944-11953 ◽  
Author(s):  
Malisa S. Chiappero ◽  
Fabio E. Malanca ◽  
Gustavo A. Argüello ◽  
Steven T. Wooldridge ◽  
Michael D. Hurley ◽  
...  
Keyword(s):  
Atmospheric Chemistry
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