 Subjects -> METEOROLOGY (Total: 106 journals)
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- Significant abundances of alkaline components in the fine and coarse
aerosols over a tropical rain shadow location in peninsular India-
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Abstract: This paper reports the chemistry of fine (PM2.5) and coarse (PM10) aerosols sampled over a period of three years during 2018–2021 at a semi -arid tropical location in the rain shadow region of the peninsular India. The data is classified in to dry (December to May) and wet (June to November) periods. Scavenging effect due to rains have culminated in to less concentrations of both fine and coarse aerosols and their ionic components in the wet period. Significantly high concentrations of the crustal components such as Ca, Na, K and Mg from the local dust resulted in the alkaline pH in both dry and wet periods with Ca and Mg emerging as major neutralizing components. Overall, < 20% samples of both fine and coarse aerosols depicted acidic pH. Concentration of SO4 was comparatively more than NO3 indicating towards more presence of stationary sources (industrial/domestic emissions) than mobile (vehicular emissions) sources. Combustion generated and highly absorbing black carbon aerosols showed high concentration during the dry period. Local activities comprising residential, agricultural, vehicular and industrial emissions were the major sources of aerosols at Solapur however, the contribution from the distant sources were also found to contribute as inferred from the cluster analysis and concentration weighted trajectories (CWT). The observed abundances of the alkaline dust aerosols that could act as cloud condensation nuclei or ice nuclei will have important implications on the studies related to cloud aerosol precipitation interaction over this region.
PubDate: 2023-05-27
- Fate of 1,3-dioxolane in the troposphere: kinetics, mechanism with
theoretical support, and atmospheric implications-
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Abstract: The atmospheric fate of 1,3-dioxolane is assessed by measuring the OH and Cl initiated gas-phase oxidation kinetics, and exploring their mechanistic pathways. Absolute OH reaction rate coefficient of 1,3-dioxolane using laser photolysis-laser induced fluorescence technique is found to be (1.27 ± 0.03) × 10–11 cm3 molecule−1 s−1 at 298 ± 2 K and it is in good agreement with the measured relative value of (1.13 ± 0.12) × 10–11 cm3 molecule−1 s−1, using gas-chromatography. Relative value of Cl reaction rate coefficient with 1,3-dioxolane is found to be (1.64 ± 0.60) × 10–10 cm3 molecule−1 s−1. The tropospheric lifetime of 1,3-dioxolane is calculated to be about 22 h under ambient conditions. Interestingly, it reduces to about 8 h near marine boundary layer, where Cl reaction takes over the OH reaction. Such a short lifetime with respect to reaction with OH and Cl suggests the atmospheric impact of 1,3-dioxolane to be local. Formic acid, ethylene carbonate, and 1,2-ethanediol monoformate are observed as stable products in OH as well as Cl oxidation. 1,3-dioxolane may contribute as one of the sources of formic acid in the atmosphere. Theoretical calculations for the OH-initiated hydrogen abstraction of 1,3-dioxolane revealed that the reaction follows an indirect path through the formation of pre- and post-reaction complexes at entrance and exit channels, respectively with the lowest barrier height of 3.5 kcal/mol. Photochemical ozone creation potential of 1,3-dioxolane is calculated.
PubDate: 2023-04-12
- Variations in mixing states of organic aerosol composition and formation
of secondary organic aerosol at background region-
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Abstract: Investigation on organic particles was limited in the background regions of Yangtze River Delta (YRD) and little information has been obtained on organic particles of Lin’an (LA). In the present study, the morphology, composition, mixing state, and size of organic aerosols with diameter less than 1 µm were characterized at Lin’an from 20 March 2019 to 20 April 2019. In all samples, irregular types of organic matter (OM) particles were high fraction during morning (72.4%), afternoon (59.1%), and evening (52%), and most of them were internally mixed. In our study, we identified a higher fraction of internally mixed particles in evenings (85%), followed by afternoon (81%), and fewer mixed particles in mornings (68%), indicating particle growth during afternoon and evening. Further, the results show that fraction of organic coating particles was higher in evening (27.4%) and afternoon (12%) indicates strong photochemical processes and formation of secondary organic aerosol on the inorganic particles and new particles formation. Our study reveals that biomass burning in the morning and coal burning from heavy industries, power plants, and vehicles in surrounding urban regions in the afternoon and evenings significantly affected background air quality.
PubDate: 2022-12-28
DOI: 10.1007/s10874-022-09445-0
- Remote sensing of aerosols due to biomass burning over Kanpur, Sao-Paulo,
Ilorin and Canberra-
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Abstract: Aerosol affect the climate in number of ways. In order to investigate these effects, we need a deep insight into aerosols optical, physical and radiative properties. So, to understand aerosols climatology, we investigate the properties of aerosols such as aerosol optical depth (AOD) (500 nm), Angstrom exponent (AE) (440–870 nm), single scattering albedo (SSA), refractive index (RI) and aerosols radiative forcing (ARF). For this purpose, we select four different AErosol RObotic NETwork (AERONET) sites located in four different continents; Kanpur, (India) Asia, Sao-Paulo, (Brazil) Southern America, IIorin, (Nigeria) Africa and Canberra, Australia. High AOD and AE is found (AOD = 0.90, AE = 1.31) in November at Kanpur and in September (AOD = 0.39, AE = 1.48) at Sao-Paulo. High AOD (1.06 and 1.12) over IIorin in January and February is found because of fog and haze. SSA shows decreasing trend with increasing wavelengths having minimum value (0.88 and 0.78 at 1020 nm) during the months of DJF and SON over Sao-Paulo and Canberra respectively. The highest value of SSA (~ 0.96) is found during the months of MAM over IIorin because of presence of coarse aerosols. The low value of SSA over Kanpur during DJF months shows dominance of fine urban/ biomass burning aerosols. Based on the values of AOD, AE and SSA, Canberra is the most pristine site. The estimated ARF values indicate that Kanpur and Ilorin sites exhibit higher TOA and BOA values as compared to Sao-Paulo. ARF at ATM is observed to be 7.4 Wm−2 higher during JJA months and 10.1 Wm−2 during SON months than MAM months over Kanpur. We have also observed lowest ARF efficiency (FeffBOA) of − 181 Wm−2 AOD−1550 nm during MAM months for Sao-Paulo while the highest value of − 297 Wm−2 AOD−1550 nm is observed during DJF months for Kanpur.
PubDate: 2022-10-13
DOI: 10.1007/s10874-022-09444-1
- Water-soluble dicarboxylic acids, oxoacids and α-dicarbonyls in the
tropical aerosols in coastal megacity Mumbai: molecular characteristics
and formation processes-
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Abstract: Daytime and nighttime PM10 samples were collected during summer (June) and winter (February) at a representative urban site in Mumbai, located on the western coast of Indian subcontinent. Samples were studied for molecular distribution of water-soluble dicarboxylic acids, oxoacids and dicarbonyls as well as total carbon (TC), water-soluble organic carbon (WSOC), inorganic ions along with specific markers (levoglucosan, K+) to better understand sources and formation processes of organic aerosols in Mumbai. The distribution of water-soluble organics was characterised by high abundance of oxalic acid (C2), followed by phthalic (Ph), terephthalic (tPh), azelaic (C9), malonic (C3), and succinic acids (C4). Positive correlations between C2, sulfate and glyoxal (ωC2) suggest secondary production of C2 predominantly via aqueous phase chemistry. C2 also showed positive correlation with K+ and levoglucosan indicating that biomass/biofuel burning is the potential source of diacids in the Mumbai aerosols. In addition, higher average contributions of total diacids to WSOC and OC in winter than in summer suggest that aerosols were aged i.e., photochemically well processed in winter in Mumbai. On the other hand, diurnal change in their ratios is observed with higher ratio in daytime samples than that of previous and succeeding nighttime samples, suggesting diacids are also influenced from local sources in both the seasons. This study demonstrates that biomass burning as well as biogenic sources are important sources influencing the distributions of aerosols in Mumbai.
PubDate: 2022-10-08
DOI: 10.1007/s10874-022-09442-3
- Surface ozone changes during the COVID-19 outbreak in China: An insight
into the pollution characteristics and formation regimes of ozone in the
cold season-
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Abstract: The countrywide lockdown in China during the COVID-19 pandemic provided a natural experiment to study the characteristics of surface ozone (O3). Based on statistical analysis of air quality across China before and during the lockdown, the tempo-spatial variations and site-specific formation regimes of wintertime O3 were analyzed. The results showed that the O3 pollution with concentrations higher than air quality standards could occur widely in winter, which had been aggravated by the emission reduction during the lockdown. On the national scale of China, with the significant decrease (54.03%) in NO2 level from pre-lockdown to COVID-19 lockdown, the maximum daily 8-h average concentration of O3 (MDA8h O3) increased by 39.43% from 49.05 to 64.22 μg/m3. This increase was comprehensively contributed by attenuated NOx suppression and favorable meteorological changes on O3 formation during the lockdown. As to the pollution states of different monitoring stations, surface O3 responded oppositely to the consistent decreased NO2 across China. The O3 levels were found to increase in the northern and central regions, but decrease in the southern region, where the changes in both meteorology (e.g. temperature drops) and precursors (reduced emissions) during the lockdown had diminished local O3 production. The spatial differences in NOx levels generally dictate the site-specific O3 formation regimes in winter, with NOx-titration/VOCs-sensitive regimes being dominant in northern and central China, while VOCs-sensitive/transition regimes being dominant in southern China. These findings highlight the influence of NOx saturation levels on winter O3 formation and the necessity of VOCs emission reductions on O3 pollution controls.
PubDate: 2022-10-07
DOI: 10.1007/s10874-022-09443-2
- Christian Junge – a pioneer in global atmospheric chemistry
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Abstract: Christian Junge (1912–1996) is considered by many to be the founder of the modern discipline of atmospheric chemistry. In studies from the 1950s through the 1970s, Junge was able to link chemical measurements in a few scattered locations around the earth and integrate them with meteorology to develop the first global view of the basic chemical and physical processes that control the sources, transport, transformations, and fate of particles and gases in the atmosphere. In this paper we summarize and comment upon a number of Junge’s seminal research contributions to atmospheric chemistry, including his discovery of the stratospheric sulfate layer (known as the Junge layer), his recognition of the relationship between the variability of the concentrations of trace gases and their atmospheric lifetimes, his studies of aerosol size and number distributions, his development of the first quantitative model of tropospheric ozone, and other significant scientific investigations. We also discuss Junge’s professional life, his many international leadership positions and honors, as well as some memories and reflections on his many abilities that led to his outstanding contributions to the science of atmospheric chemistry.
PubDate: 2022-08-24
DOI: 10.1007/s10874-022-09437-0
- Analysis of the seasonal and fractional variability of metals bearing
particles in an urban environment and their inhalability-
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Abstract: This study aimed to calculate size-fractionated PM-bound metals concentration (Co, V, Ni, Cu, Mn, As, Cd, Pb, Cr and Hg) in a European hot spot area in terms of PM air pollution (Zabrze, Poland) and to show their deposition ratios in human airways. Additionally, meteorological data was used to conclude the probable influence of atmospheric conditions on the variability of the PM mass concentrations in different periods of the year. Data regarding the elemental composition of size-fractionated PM in various regions of Poland was also presented. The determination of the selected metals in PM-fractionated samples (PM1, PM2.5, and PM10) was performed in two periods – the heating and non-heating season. It was found that metals were primarily associated with particles less than 1 µm, however, the PM size distribution had shown bi-modal characteristics and the maxima of metal mass distribution occurred in both submicron and fine modes. High PM1 mass loadings, observed especially in the non-heating season were probably due to an influx of fine and even smaller particles from traffic sources. Metals distributions as well as respiratory deposition ratios for PM-bound elements calculated using the MPPD V2.11 model favored nasal and head deposition. The overall mass deposition of metals in the respiratory tract of adults was: 0.39 (Head region, H); 0.07 (Tracheobronchial region, TB); 0.16 (Pulmonary region, P) respectively. No matter the season, the highest inhalable concentrations of metals were found for Cu, Mn, Cr and Pb. Only Cr and Pb are classified as carcinogenic and mutagenic (according to IARC classification).
PubDate: 2022-08-20
DOI: 10.1007/s10874-022-09438-z
- Temporary reduction in VOCs associated with health risk during and after
COVID-19 in Maharashtra, India-
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Abstract: A novel coronavirus has affected almost all countries and impacted the economy, environment, and social life. The short-term impact on the environment and human health needs attention to correlate the Volatile organic compounds (VOCs) and health assessment for pre-, during, and post lockdowns. Therefore, the current study demonstrates VOC changes and their effect on air quality during the lockdown. The findings of result, the levels of the mean for total VOC concentrations were found to be 15.45 ± 21.07, 2.48 ± 1.61, 19.25 ± 28.91 µg/m3 for all monitoring stations for pre-, during, and post lockdown periods. The highest value of TVOCs was observed at Thane, considered an industrial region (petroleum refinery), and the lowest at Bandra, which was considered a residential region, respectively. The VOC levels drastically decreased by 52%, 89%, 80%, and 97% for benzene, toluene, ethylbenzene, and m-xylene, respectively, during the lockdown period compared to the previous year. In the present study, the T/B ratio was found lower in the lockdown period as compared to the pre-lockdown period. This can be attributed to the complete closure of non-traffic sources such as industries and factories during the lockdown. The Lifetime Cancer Risk values for all monitoring stations for benzene for pre-and-post lockdown periods were higher than the prescribed value, except during the lockdown period.
PubDate: 2022-08-17
DOI: 10.1007/s10874-022-09440-5
- Ionic composition, source identification of rainwater, and its
contribution to nutrient deposition in monsoon, over Sundarban Mangrove
forest-
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Abstract: A detailed study on potential sources, variation, and environmental effects of the rainwater ions was carried out at Lothian Island, Sundarban mangrove forest, India, during the southwest monsoon (June–September) in 2019. On an event basis, the maximum rainwater precipitation was observed 17.65 mm Day −1 and a minimum of 1.02 mm Day −1. The maximum amount of total precipitation was recorded in the month of July (237 mm). The volume weighted mean (VWM) concentration shows that the total ionic composition was 93.7 μeq L−1, whereas the percentage contribution of the total ionic concentration is found to be 45.97% to anions and 54.02% to the cations. Temporal variation was observed between early (June- July) and late monsoon (August—September), which shows a high concentration of major ions in early monsoon and low concentration in late monsoon due to the washout of atmospheric particles with the frequent and increasing precipitation. The pH values of the 78% samples show neutral pH and neutralization factors (NF) followed a sequence of NFCa ˃NFMg ˃ NFNH4 with factors of 0.77, 0.34, and 0.14 indicating Ca2+ was the most potential species to balance the acidic ions (NO3−, SO42−) over the study area. Source apportionment study indicates the significant influence of marine actions (long-range transport by monsoonal wind from marine origin, Sea spray, salty soil profile of mangrove) as the major source of ions over Sundarban. The rate of nutrient wet deposition in the form of rainwater was estimated and average monsoonal nitrogen flux was observed 0.87 kg ha−1where NO3 contributes the most (0.60 kg ha−1). N and P deposition flux also showed a simultaneous pattern with the seasonal nutrient concentration of surrounding river water, which may be an indication of a possible contribution of atmospheric wet deposition in the spike of monsoonal nutrient concentration in river water.
PubDate: 2022-08-17
DOI: 10.1007/s10874-022-09441-4
- Air pollution trends measured from MODIS and TROPOMI: AOD and CO over
Pakistan-
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Abstract: The TROPOMI (TROPOspheric monitoring instrument) onboard Sentinel-5 Precursor (S5P) satellite provides high spatial resolution data of carbon monoxide (CO) while the MAIAC (Multiangle Implementation of Atmospheric Correction) is a newly developed algorithm applied to MODIS collection 6 observations to retrieve AOD (Aerosol Optical Depth) at a high spatial resolution of 1 km. The present study utilized the MAIAC AOD from MODIS Terra and Aqua polar-orbiting satellites between March 2000 to December 2021 and CO from Sentinel-5P during the available period July 2018-December 2021 over Pakistan. Moreover, we used three trend techniques (Linear regression, Mann–Kendall (MK), and Theil-Sen’s Slope) to examine the trends of AOD and CO over Pakistan. The results show that both AOD and CO have high values over central Punjab, western Balochistan, central Sindh, and Khyber Pakhtunkhwa. The mean annual high AOD of > 1.2 is observed in eastern Punjab because of an increase in urbanization, industrialization, and economical activities whereas the AOD of ~ 1.0 is observed over Balochistan, Sindh, and a few parts of Khyber Pakhtunkhwa. The highest mean annual CO of ˃0.03 mol/m^2 is seen over central Punjab, Sindh, and Khyber Pakhtunkhwa. The results show that seasonal mean MAIAC AOD ranging from 0.7 to > 0.9 was seen over Punjab and Sindh province during the monsoon season whereas the lowest AOD is detected in the winter season over few parts of Balochistan. In contrast, the highest mean seasonal CO ranging from 0.040 to > 0.055 mol/m^2 was seen in the winter season over Punjab. The lowest CO concentration is observed in the winter season over the northern region of Pakistan. Non-parametric analyses (MK and Theil-Sen’s slope) also show an increasing trend of CO over Pakistan from 2018 to 2021. Furthermore, we have also investigated the trends of AOD and CO over selected cities of Pakistan using linear regression, MK test, and Theil-Sen’s slope to reveal long-term air pollution trends.
PubDate: 2022-05-24
DOI: 10.1007/s10874-022-09436-1
- Elemental analysis of PM10 in southwest Mexico City and source
apportionment using positive matrix factorization-
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Abstract: The results of a study of the elemental concentrations in PM10 samples collected at a site in southwest Mexico City during 2016 and 2019, are presented. The concentrations of up to 19 elements were measured with X-ray fluorescence (XRF). These analyses were complemented with ion chromatography for eight ionic species (for the samples collected in 2016). The behaviors of the gravimetric mass and elemental concentrations are described for the morning, afternoon, and night-time periods in 2019. The elemental concentrations observed in the PM10 samples did not present significant changes as compared to those published in previous works. It was found that the gravimetric mass concentrations were always below the official standards, except during a contingency period in May 2019. The positive matrix factorization (PMF) receptor model was used to identify contaminating sources and their relative contributions to the concentrations of the detected elements. The soil-related factors were the most abundant contributors, with other components associated to traffic, biomass burning, fuel oil, secondary aerosol, and dust resuspension. The occurrence of episodes in 2019 is explained with the aid of PMF and back-trajectories, while the contingency period is due to other chemical species not detected in PM10 with XRF. A comparison with data collected in 2005 in downtown Mexico City is also carried out, as well as with urban areas in other countries.
PubDate: 2022-05-16
DOI: 10.1007/s10874-022-09435-2
- Characteristics of the chemical composition and source apportionment of
PM2.5 for a one-year period in Wuhan, China-
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Abstract: In this study, 123 PM2.5 filter samples were collected in Wuhan, Hubei province from December 2014 to November 2015. Water- soluble inorganic ions (WSIIs), elemental carbon (EC), organic carbon (OC) and inorganic elements were measured. Source apportionment and back trajectory was investigated by the positive matrix factorization (PMF) model and the hybrid single particle lagrangian integrated trajectory (HYSPLIT) model, respectively. The annual PM2.5 concentration was 80.5 ± 38.2 μg/m3, with higher PM2.5 in winter and lower in summer. WSIIs, OC, EC, as well as elements contributed 46.8%, 14.8%, 6.7% and 8% to PM2.5 mass concentration, respectively. SO42−, NO3− and NH4+ were the dominant components, accounting for 40.2% of PM2.5 concentrations. S, K, Cl, Ba, Fe, Ca and I were the main inorganic elements, and accounted for 65.2% of the elemental composition. The ratio of NO3−/SO42− was 0.86 ± 0.72, indicating that stationary sources play dominant role on PM2.5 concentration. The ratio of OC/EC was 2.9 ± 1.4, suggesting the existence of secondary organic carbon (SOC). Five sources were identified using PMF model, which included secondary inorganic aerosols (SIA), coal combustion, industry, vehicle emission, fugitive dust. SIA, coal combustion, as well as industry were the dominant contributors to PM2.5 pollution, accounting for 34.7%, 20.5%, 19.6%, respectively.
PubDate: 2022-03-31
DOI: 10.1007/s10874-022-09431-6
- Study of variation of aerosol optical properties over a high altitude
station in Indian Western Himalayan region, palampur using raman lidar
system-
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Abstract: A Raman lidar system was operated along with the Microtops sunphotometer measurements to carry out the study of the variation of the optical properties of aerosols over Palampur (32.11° N and 76.53° E), India from 17th April to 11th May 2019. The lidar system is furnished with Raman (N2) channel and depolarization channel allowing independent measurement of Lidar Ratio (LR) and linear depolarization ratio. The study reveals that the majority of the aerosols approximately were restricted within the planetary boundary layer (PBL) and very less loading was present in the free troposphere over the study location. The particle loading over the study period was found to be very less with aerosol backscatter coefficient (at 355 nm) ranging from ∼0.13 Mm−1sr−1 to ∼7.25 Mm−1sr−1 with mean value of 2.67 ± 0.82 Mm−1sr−1 and it is well supplemented by the mean aerosol optical depth (AOD) of 0.37 ± 0.13 obtained from Microtops Sunphotometer. The average lidar ratio values for 0-1 km altitude (L1) 72 ± 13sr, for 1-2 km (L2) altitude 55 ± 8sr, for 2-3 km (L3) 54 ± 15sr were observed as suggesting dominance of the biomass burning aerosols and anthropogenic aerosols. The particle depolarization ratio (355 nm) values were found from approximately 4.8 ± 2.7% to 11.5 ± 1.9% with the mean value of 7 ± 1.3% suggesting the presence of non-spherical particles. To trace the sources of the pollution, we derived the HYSPLIT trajectory which shows the majority of the movement was from local sources.
PubDate: 2022-03-21
DOI: 10.1007/s10874-022-09432-5
- Emission of volatile organic compounds by plants on the floor of boreal
and mid-latitude forests-
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Abstract: The forests of the boreal and mid-latitude zones of the Northern Hemisphere are the largest source of reactive volatile organic compounds (VOCs), which have an important impact on the processes occurring in the atmospheric boundary layer. However, the composition of biogenic emissions from them remains incompletely characterized, as evidenced by the significant excess OH radical concentrations predicted by models in comparison with those observed under the forest canopy. The missing OH sink in the models may be related to the fact that they do not take into account the emission of highly reactive VOCs by vegetation on the forest floor. In this work, we report the results of laboratory determinations of the composition of VOCs emitted by representatives of different groups of plants that form the living soil cover (LSC) in the forests of the boreal and mid-latitude zones: bryophytes, small shrubs, herbaceous plants, and ferns. In the chromatograms of volatile emissions of all 11 studied plant species, 254 compounds with carbon atoms ranging in number from two to 20 were registered. All plants were characterized by the emission of terpenes, accounting for 112 compounds, and the second largest group (35 substances) was formed by carbonyl compounds. Both groups of compounds are characterized by high reactivity and are easily included in the processes of gas-phase oxidation with the participation of radicals HO, NO3 and ozone. These data indicate the importance of a thorough study of the so far disregarded source of VOCs, that is, the LSC in forests.
PubDate: 2022-03-15
DOI: 10.1007/s10874-022-09434-3
- Estimation of aerosol acidity at a suburban site of Nanjing using machine
learning method-
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Abstract: Aerosol acidity is found to exert negative effects on ecosystem diversity and architectural appearance. Current analytical technology is unable to measure in-situ aerosol acidity (i.e., pH value) of ambient fine particle due to the absence of appropriate pH electrodes. Thermodynamic modeling methods including ISORROPIA II and Extended Aerosol Inorganics Model Version IV (E-AIM V) are mostly used in the estimation of in-situ aerosol acidity with the inputs of water soluble ions worldwide. This study proposes a flexible method with the aid of multilayer perceptron (MLP) neural network analysis to estimate in-situ aerosol acidity of ambient fine particle (< 2.5 μm in aerodynamic diameter or PM2.5) with the inputs of water soluble ions (i.e., Cl−, NO3−, SO42−, Na+, NH4+, K+, Mg2+, Ca2+), gaseous air pollutants (i.e., CO, NO2, SO2) and meteorological parameters (i.e., humidity and temperature). The dataset consists of ambient fine particles collected across four individual sampling periods in the autumn and winter of 2019 and 2020 at a suburban site of Nanjing. The pH values of ambient fine particle were found to be ranging from 2.0 to 4.0 estimated by E-AIM model. Levels of pH estimated by MLP neural network analysis agreed well with pH values estimated by E-AIM model with R2 value of 0.98.
PubDate: 2022-02-26
DOI: 10.1007/s10874-022-09433-4
- Long-range transport of Asian emissions to the West Pacific tropical
tropopause layer-
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Abstract: Rapid transport by deep convection is an important mechanism for delivering surface emissions of reactive halocarbons and other trace species to the tropical tropopause layer (TTL), a key region of transport to the stratosphere. Recent model studies have indicated that increased delivery of short-lived halocarbons to the TTL could delay stratospheric ozone recovery. We report here measurements in the TTL over the western Pacific Ocean of short-lived halocarbons and other trace gases that were transported eastward after convective lofting over Asia. Back-trajectories indicate the sampled air primarily originated from the Indian subcontinent. While short-lived organic bromine species show no measurable change over background mixing ratios, short-lived chlorinated organic species were elevated above background mixing ratios (dichloromethane (Δ48.2 ppt), 1,2-dichloroethane (Δ4.21 ppt), and chloroform (Δ4.85 ppt)), as well as longer-lived halogenated species, methyl chloride (Δ82.0 ppt) and methyl bromide (Δ1.91 ppt). This transported air mass thus contributed an excess equivalent effective chlorine burden of 316 ppt, with 119 ppt from short lived chlorinated species, to the TTL. Non-methane hydrocarbons (NMHC) were elevated 60 - 400% above background mixing ratios. The NMHC measurements were used to characterize the potential source regions, which are consistent with the convective influence analysis. The measurements indicate a chemical composition heavily impacted by biofuel/biomass burning and industrial emissions. This work shows that convection can loft Asian emissions, including short-lived chlorocarbons, and transport them to the remote TTL.
PubDate: 2022-02-23
DOI: 10.1007/s10874-022-09430-7
- Stable carbon and nitrogen isotopic characteristics of PM2.5 and PM10 in
Delhi, India-
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Abstract: This study presents the chemical composition (carbonaceous and nitrogenous components) of aerosols (PM2.5 and PM10) along with stable isotopic composition (δ13C and δ15N) collected during winter and the summer months of 2015–16 to explore the possible sources of aerosols in megacity Delhi, India. The mean concentrations (mean ± standard deviation at 1σ) of PM2.5 and PM10 were 223 ± 69 µg m−3 and 328 ± 65 µg m−3, respectively during winter season whereas the mean concentrations of PM2.5 and PM10 were 147 ± 22 µg m−3 and 236 ± 61 µg m−3, respectively during summer season. The mean value of δ13C (range: − 26.4 to − 23.4‰) and δ15N (range: 3.3 to 14.4‰) of PM2.5 were − 25.3 ± 0.5‰ and 8.9 ± 2.1‰, respectively during winter season whereas the mean value of δ13C (range: − 26.7 to − 25.3‰) and δ15N (range: 2.8 to 11.5‰) of PM2.5 were − 26.1 ± 0.4‰ and 6.4 ± 2.5‰, respectively during the summer season. Comparison of stable C and N isotopic fingerprints of major identical sources suggested that major portion of PM2.5 and PM10 at Delhi were mainly from fossil fuel combustion (FFC), biomass burning (BB) (C-3 and C-4 type vegitation), secondary aerosols (SAs) and road dust (SD). The correlation analysis of δ13C with other C (OC, TC, OC/EC and OC/WSOC) components and δ15N with other N components (TN, NH4+ and NO3−) are also support the source identification of isotopic signatures.
PubDate: 2022-01-23
DOI: 10.1007/s10874-022-09429-0
- Size distributions and dry deposition fluxes of water-soluble inorganic
nitrogen in atmospheric aerosols in Xiamen Bay, China-
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Abstract: Size-segregated aerosol particles were collected using a high volume MOUDI sampler at a coastal urban site in Xiamen Bay, China, from March 2018 to June 2020 to examine the seasonal characteristics of aerosol and water-soluble inorganic ions (WSIIs) and the dry deposition of nitrogen species. During the study period, the annual average concentrations of PM1, PM2.5, PM10, and TSP were 14.8 ± 5.6, 21.1 ± 9.0, 35.4 ± 14.2 μg m−3, and 45.2 ± 21.3 μg m−3, respectively. The seasonal variations of aerosol concentrations were impacted by the monsoon with the lowest value in summer and the higher values in other seasons. For WSIIs, the annual average concentrations were 6.3 ± 3.3, 2.1 ± 1.2, 3.3 ± 1.5, and 1.6 ± 0.8 μg m−3 in PM1, PM1-2.5, PM2.5–10, and PM>10, respectively. In addition, pronounced seasonal variations of WSIIs in PM1 and PM1-2.5 were observed, with the highest concentration in spring-winter and the lowest in summer. The size distribution showed that SO42−, NH4+ and K+ were consistently present in the submicron particles while Ca2+, Mg2+, Na+ and Cl− mainly accumulated in the size range of 2.5–10 μm, reflecting their different dominant sources. In spring, fall and winter, a bimodal distribution of NO3− was observed with one peak at 2.5–10 μm and another peak at 0.44–1 μm. In summer, however, the fine mode peak disappeared, likely due to the unfavorable conditions for the formation of NH4NO3. For NH4+ and SO42−, their dominant peak at 0.25–0.44 μm in summer and fall shifted to 0.44–1 μm in spring and winter. Although the concentration of NO3–N was lower than NH4–N, the dry deposition flux of NO3–N (35.77 ± 24.49 μmol N m−2 d−1) was much higher than that of NH4–N (10.95 ± 11.89 μmol N m−2 d−1), mainly due to the larger deposition velocities of NO3–N. The contribution of sea-salt particles to the total particulate inorganic N deposition was estimated to be 23.9—52.8%. Dry deposition of particulate inorganic N accounted for 0.95% of other terrestrial N influxes. The annual total N deposition can create a new productivity of 3.55 mgC m−2 d−1, accounting for 1.3–4.7% of the primary productivity in Xiamen Bay. In light of these results, atmospheric N deposition could have a significant influence on biogeochemistry cycle of nutrients with respect to projected increase of anthropogenic emissions from mobile sources in coastal region.
PubDate: 2021-10-11
DOI: 10.1007/s10874-021-09427-8
- Effects of light intensity on the production of VSLs from the marine
diatom Ditylum brightwellii-
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Abstract: Very short-lived substances (VSLs) are known to play an important role in ozone depletion in the troposphere and stratosphere. Environmental factors that influence the production of these compounds by marine phytoplankton, which is known to be the source of these compounds in open oceans, have not yet been well studied. Here we examined the effects of light intensity on the production of VSLs by the marine diatom Ditylum brightwellii. Bromodichloromethane (CHBrCl2), dibromochloromethane (CHBr2Cl), bromoform (CHBr3), chloroform (CHCl3), and dibromomethane (CH2Br2) in cultures incubated under full spectrum daylight intensities of 30, 60, and 120 µmol photons m− 2 s− 1 were measured using purge and trap gas chromatograph–mass spectrometry. Phytoplankton growth was monitored by measuring chlorophyll-a concentration and cell density. Both the chlorophyll-a concentration (the cell density) and the production rates of VSLs increased with increasing light intensity. The maximum production rates of CHBrCl2, CHBr2Cl, CHBr3, CHCl3, and CH2Br2 were observed during the exponential or stationary phase, with the exception of CH2Br2 incubated under 30 µmol photons m− 2 s− 1. The chlorophyll a-normalized (or cell-normalized) production rates of VSLs increased with increasing light intensity, e.g., the maximum of chlorophyll a-normalized production rates of CHCl3 under light intensities of 30, 60 and 120 µmol photons m− 2 s− 1 were 0.06, 0.46 and 1.84 µmol (g chlorophyll a) −1 day− 1, respectively. Our results suggest that marine diatoms are one of the significant sources of VSLs and that light intensity is a significant factor in estimating VSLs emissions from the open ocean.
PubDate: 2021-09-17
DOI: 10.1007/s10874-021-09426-9
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