scholarly journals Technical Note: The application of an improved gas and aerosol collector for ambient air pollutants in China

2012 ◽  
Vol 12 (3) ◽  
pp. 7753-7791 ◽  
Author(s):  
H.-B. Dong ◽  
L.-M. Zeng ◽  
M. Hu ◽  
Y.-S. Wu ◽  
Y.-H. Zhang ◽  
...  
Keyword(s):  
Collection Efficiency ◽  
Ambient Air ◽  
Field Studies ◽  
Technical Note ◽  
Quality Data ◽  
Rural Site ◽  
Filter Method ◽  
Ambient Conditions ◽  
Wide Range ◽  
Haze Formation

Abstract. An improved Gas and Aerosol Collector (GAC) equipped with a newly designed aerosol collector and a set of dull-polished wet annular denuder (WAD) was developed based on a Steam Jet Aerosol Collector (SJAC) sampler. Combined with Ion Chromatography (IC) the new sampler performed well in laboratory tests with high collection efficiencies for SO2 (above 98%) and particulate sulfate (as high as 99.5%). When applied in two major field campaigns (rural and coastal sites) in China, the GAC-IC system provided high-quality data in ambient conditions even under high loadings of pollutants. Its measurements were highly correlated with data by other commercial instruments such as the SO2 analyzer (43c, Thermo-Fisher, USA; R2 as 0.96), the HONO analyzer (LOPAP, Germany; R2 as 0.91 for nighttime samples), a filter sampler (Tianhong, China; R2 as 0.86 for SO42−), and Aerosol Mass Spectrometer (AMS, Aerodyne, USA; R2 above 0.77 for major species) over a wide range of concentrations. Through the application of the GAC-IC system, it was identified that 70% of chloride and nitrate by the filter method could be lost during daytime sampling due to high temperature in the rural site of Kaiping. In Changdao field campaign (coastal site) the comparison with the measurements by the GAC-IC suggested that the collection efficiency of AMS might be greatly influenced by high relative humidity (RH) especially in coastal or marine environment. Through laboratory and field studies, this instrument is proved highly reliable, which is particularly useful in future intensive campaigns or long-term monitoring stations to study various environmental issues such as secondary aerosol and haze formation, as well as climate change.

scholarly journals Technical Note: The application of an improved gas and aerosol collector for ambient air pollutants in China

2012 ◽  
Vol 12 (21) ◽  
pp. 10519-10533 ◽  
Author(s):  
H.-B. Dong ◽  
L.-M. Zeng ◽  
M. Hu ◽  
Y.-S. Wu ◽  
Y.-H. Zhang ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Collection Efficiency ◽  
Ambient Air ◽  
Technical Note ◽  
Quality Data ◽  
Rural Site ◽  
Filter Method ◽  
Ambient Conditions ◽  
Major Species ◽  
Wide Range

Abstract. An improved Gas and Aerosol Collector (GAC) equipped with a newly designed aerosol collector and a set of dull-polished wet annular denuder (WAD) was developed based on a Steam Jet Aerosol Collector (SJAC) sampler. Combined with Ion Chromatography (IC) the new sampler performed well in laboratory tests with high collection efficiencies for SO2 (above 98%) and particulate sulfate (as high as 99.5%). An inter-comparison between the GAC-IC system and the filter-pack method was performed and the results indicated that the GAC-IC system could supply reliable particulate sulfate, nitrate, chloride, and ammonium data in field measurement with a much wider range of ambient concentrations. When applied in two major field campaigns (rural and coastal sites) in China, the GAC-IC system provided high-quality data in ambient conditions even under high loadings of pollutants. Its measurements were highly correlated with data by other commercial instruments such as the SO2 analyzer (43c, Thermo-Fisher, USA; R2 as 0.96), the HONO analyzer (LOPAP, Germany; R2 as 0.91 for samples from 15:00 to 07:00), a filter sampler (Tianhong, China; R2 as 0.86 for SO42−), and Aerosol Mass Spectrometer (AMS, Aerodyne, USA; R2 above 0.77 for major species) over a wide range of concentrations. Through the application of the GAC-IC system, it was identified that 70% of chloride and nitrate by the filter method could be lost during daytime sampling due to high temperature in the rural site of Kaiping. In Changdao field campaign (coastal site), though a particle dryer was applied, its drying efficiency was not well considered for the collection efficiency of AMS seemed still interfered a bit by local high relative humidity. If the inter-comparison was done with relative humidity below 50%, the correlations ranged from 0.81 to 0.94 for major species. Through laboratory and field studies, this instrument is proved particularly useful in future intensive campaigns or long-term monitoring stations to study various environmental issues such as secondary aerosol and haze formation, as well as climate change.

Ambient Condition Effects on NOx and CO Emissions From Process Heaters

2008 ◽  
Author(s):  
Wesley R. Bussman ◽  
Charles E. Baukal
Keyword(s):  
Atmospheric Pressure ◽  
Ambient Air ◽  
Operating Conditions ◽  
Nox Emissions ◽  
Ambient Conditions ◽  
Fuel Gas ◽  
Natural Draft ◽  
Actual Operating ◽  
Wide Range ◽  
Pollution Emissions

Because process heaters are typically located outside, their operation is subject to the weather. Heaters are typically tuned at a given set of conditions; however, the actual operating conditions may vary dramatically from season to season and sometimes even within a given day. Wind, ambient air temperature, ambient air humidity, and atmospheric pressure can all significantly impact the O2 level, which impacts both the thermal efficiency and the pollution emissions from a process heater. Unfortunately, most natural draft process burners are manually controlled on an infrequent basis. This paper shows how changing ambient conditions can considerably impact both CO and NOx emissions if proper adjustments are not made as the ambient conditions change. Data will be presented for a wide range of operating conditions to show how much the CO and NOx emissions can be affected by changes in the ambient conditions for fuel gas fired natural draft process heaters, which are the most common type used in the hydrocarbon and petrochemical industries. Some type of automated burner control, which is virtually non-existent today in this application, is recommended to adjust for the variations in ambient conditions.

scholarly journals Wintertime aerosol chemical composition, volatility, and spatial variability in the greater London area

2016 ◽  
Vol 16 (2) ◽  
pp. 1139-1160 ◽  
Author(s):  
L. Xu ◽  
L. R. Williams ◽  
D. E. Young ◽  
J. D. Allan ◽  
H. Coe ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Solid Fuel ◽  
Field Studies ◽  
Rural Site ◽  
Urban Site ◽  
High Temporal Resolution ◽  
Volatile Organics ◽  
Aerosol Mass ◽  
Rural And Urban ◽  
Wide Range

Abstract. The composition of PM1 (particulate matter with diameter less than 1 µm) in the greater London area was characterized during the Clean Air for London (ClearfLo) project in winter 2012. Two high-resolution time-of-flight aerosol mass spectrometers (HR-ToF-AMS) were deployed at a rural site (Detling, Kent) and an urban site (North Kensington, London). The simultaneous and high-temporal resolution measurements at the two sites provide a unique opportunity to investigate the spatial distribution of PM1. We find that the organic aerosol (OA) concentration is comparable between the rural and urban sites, but the contribution from different sources is distinctly different between the two sites. The concentration of solid fuel OA at the urban site is about twice as high as at the rural site, due to elevated domestic heating in the urban area. While the concentrations of oxygenated OA (OOA) are well-correlated between the two sites, the OOA concentration at the rural site is almost twice that of the urban site. At the rural site, more than 70 % of the carbon in OOA is estimated to be non-fossil, which suggests that OOA is likely related to aged biomass burning considering the small amount of biogenic SOA in winter. Thus, it is possible that the biomass burning OA contributes a larger fraction of ambient OA in wintertime than what previous field studies have suggested. A suite of instruments was deployed downstream of a thermal denuder (TD) to investigate the volatility of PM1 species at the rural Detling site. After heating at 250 °C in the TD, 40 % of the residual mass is OA, indicating the presence of non-volatile organics in the aerosol. Although the OA associated with refractory black carbon (rBC; measured by a soot-particle aerosol mass spectrometer) only accounts for < 10 % of the total OA (measured by a HR-ToF-AMS) at 250 °C, the two measurements are well-correlated, suggesting that the non-volatile organics have similar sources or have undergone similar chemical processing as rBC in the atmosphere. Although the atomic O : C ratio of OOA is substantially larger than that of solid fuel OA and hydrocarbon-like OA, these three factors have similar volatility, which is inferred from the change in mass concentration after heating at 120 °C. Finally, we discuss the relationship between the mass fraction remaining (MFR) of OA after heating in the TD and atomic O : C of OA and find that particles with a wide range of O : C could have similar MFR after heating. This analysis emphasizes the importance of understanding the distribution of volatility and O : C in bulk OA.

scholarly journals The improved comparative reactivity method (ICRM): measurements of OH reactivity under high-NO<sub><i>x</i></sub> conditions in ambient air

2021 ◽  
Vol 14 (3) ◽  
pp. 2285-2298
Author(s):  
Wenjie Wang ◽  
Jipeng Qi ◽  
Jun Zhou ◽  
Bin Yuan ◽  
Yuwen Peng ◽  
...  
Keyword(s):  
Operation Mode ◽  
Original System ◽  
Ambient Air ◽  
Field Studies ◽  
Oh Radicals ◽  
Ambient Conditions ◽  
Crm System ◽  
Maximum Decrease ◽  
Order Of Magnitude ◽  
Comparative Reactivity

Abstract. The comparative reactivity method (CRM) was developed more than a decade to measure OH reactivity (i.e., OH loss frequency) in both laboratory and field studies. However, accurate OH reactivity quantification remains challenging under real ambient conditions, especially for OH reactivity measurements in high-NOx (e.g., > 10 ppbv) environments, as ambient NO enhances the regeneration of OH radicals in the CRM reactor. To solve this problem, we design a new and improved CRM reactor (ICRM) and add NO into the system continuously so that the HO2 radical concentration is suppressed. We confirmed the appropriate level of NO by determining the maximum decrease in the pyrrole level caused by regenerated OH radicals from NO + HO2. RO2 radicals induced by volatile organic compounds (VOCs) in the ICRM reactor were also found to react with NO, which led to the regeneration of OH radicals and thus the underestimation of OH reactivity. This effect was quantified by the calibration of representative VOC species at different NO levels, and the correction coefficients obtained were used to correct the measured OH reactivity. All these efforts resulted in reducing the uncertainty of the NO-artifact correction by at least an order of magnitude compared to the original CRM system. Additionally, these technological improvements also considerably reduced the systematic errors from pyrrole photolysis in the original system. A new operation mode was proposed for the ICRM, which is able to avoid the interference resulting from OH radicals produced by photolysis of residual humidity and save time for ambient measurement. The ICRM system was employed in a field campaign to measure OH reactivity and performed well with ambient NO levels ranging from 0 to 50 ppbv, which are typically observed in the urban and suburban atmosphere.

The Challenges of Turbocharger Matching for North American Freight Locomotives

2019 ◽  
Author(s):  
Thomas Lavertu ◽  
Matthew Hart ◽  
Christopher Homison ◽  
Preeti Vaidya
Keyword(s):  
North American ◽  
Engine Performance ◽  
Ambient Air ◽  
Ambient Conditions ◽  
Efficient Operation ◽  
Engine Efficiency ◽  
Air Temperatures ◽  
Wide Range ◽  
The Impact ◽  
Operating Points

Abstract Engine development is centered on developing a solution for best performance while meeting emissions and operational requirements. This will lead to a tradeoff between engine efficiency and emissions across a wide range of load and ambient operating points. Proper airflow to the engine through turbocharger matching is critical to ensure efficient operation and to meet emissions. This study addresses the challenges of turbocharger matching for vehicle advanced emissions control using a North American freight locomotive application as an example. The airflow trends in moving across the various operating points will be shown along with the impact on both the turbocharger and engine performance. First, the airflow trends across the locomotive load set points will be discussed along with the performance and emissions tradeoffs to meet required airflows. Results on the impact on turbocharger performance such as speed will be shown along with the engine efficiency and emissions implications. Next, the ambient operating requirements for a locomotive will be reviewed and the impact on turbocharger matching. Locomotives operate in a wide range of ambient conditions, including altitudes up to 3,050 meters and across ambient air temperatures ranging from −40 °C to well over 38 °C (including higher temperature operation). This thermal swing provides stress on the turbocharger to efficiently deliver the necessary airflow across all conditions. Trends in turbocharger performance will be reviewed and discussed across this range of ambient conditions. In addition, challenges unique to locomotive applications, such as unventilated tunnel operation and vibrational loading, will be reviewed. Finally, potential for advanced technologies such as variable geometry turbines and their applicability to locomotive operation will be discussed.

scholarly journals Femtosecond Laser Nano-Fabrication And Its Biomedical Applications

2021 ◽  
Author(s):  
Amirhossein Tavangar
Keyword(s):  
Laser Ablation ◽  
Femtosecond Laser ◽  
Biomedical Application ◽  
Femtosecond Laser Ablation ◽  
Ambient Air ◽  
Femtosecond Laser Pulses ◽  
Device Fabrication ◽  
Ambient Conditions ◽  
Wide Range ◽  
Multiple Pulses

This dissertation aims to develop a new technique for fabrication of three-dimensional (3-D) interwoven nanofibrous platforms using femtosecond laser ablation of solids in ambient conditions. In the first part, the mechanism of ablation of solids by multiple femtosecond laser pulses in ambient air is described in an explicit analytical form. The formulas for evaporation rates and the number of ablated particles for laser ablation by multiple pulses as a function of laser parameters, background gas, and material properties are predicted and compared to experimental results. Later, the formation mechanism of the nanofibrous structures during laser ablation of targets in the presence of air is discussed. The results indicate that femtosecond laser ablation of solids at air background yields crystalline nanostructures. It’s also shown that this technique allows synthesis of 3-D nanostructures on a wide range of materials including synthetic and natural materials. Later, potential practice of the proposed technique for integration of nanostructures on transparent platforms as well as inside microstructures toward device fabrication is investigated. Presented studies show that integrated nanostructure inside microchannels can be fabricated in one single step using this technique. Finally, to address the potential use of the nanostructures for biomedical application, several studies are performed to evaluate the bioactivity and biocompatibility of the nanostructures. The fabricated nanostructures incorporate the functions of 3-D nano-scaled topography and modified chemical properties to improve osseointegration, while at the same time leaving space for delivering other functional agents.

scholarly journals Femtosecond Laser Nano-Fabrication And Its Biomedical Applications

2021 ◽  
Author(s):  
Amirhossein Tavangar
Keyword(s):  
Laser Ablation ◽  
Femtosecond Laser ◽  
Biomedical Application ◽  
Femtosecond Laser Ablation ◽  
Ambient Air ◽  
Femtosecond Laser Pulses ◽  
Device Fabrication ◽  
Ambient Conditions ◽  
Wide Range ◽  
Multiple Pulses

This dissertation aims to develop a new technique for fabrication of three-dimensional (3-D) interwoven nanofibrous platforms using femtosecond laser ablation of solids in ambient conditions. In the first part, the mechanism of ablation of solids by multiple femtosecond laser pulses in ambient air is described in an explicit analytical form. The formulas for evaporation rates and the number of ablated particles for laser ablation by multiple pulses as a function of laser parameters, background gas, and material properties are predicted and compared to experimental results. Later, the formation mechanism of the nanofibrous structures during laser ablation of targets in the presence of air is discussed. The results indicate that femtosecond laser ablation of solids at air background yields crystalline nanostructures. It’s also shown that this technique allows synthesis of 3-D nanostructures on a wide range of materials including synthetic and natural materials. Later, potential practice of the proposed technique for integration of nanostructures on transparent platforms as well as inside microstructures toward device fabrication is investigated. Presented studies show that integrated nanostructure inside microchannels can be fabricated in one single step using this technique. Finally, to address the potential use of the nanostructures for biomedical application, several studies are performed to evaluate the bioactivity and biocompatibility of the nanostructures. The fabricated nanostructures incorporate the functions of 3-D nano-scaled topography and modified chemical properties to improve osseointegration, while at the same time leaving space for delivering other functional agents.

MOPGA/Make Air Quality Great Again: Filling in the air quality data gap in Africa using lower-cost RAMP monitors

2020 ◽  
Author(s):  
Ramachandran Subramanian ◽  
Matthias Beekmann ◽  
Carl Malings ◽  
Anais Feron ◽  
Paola Formenti ◽  
...  
Keyword(s):  
Air Pollution ◽  
Air Quality ◽  
Electrochemical Sensors ◽  
Low Cost ◽  
Fine Particulate Matter ◽  
Ambient Air ◽  
Ambient Air Pollution ◽  
Quality Data ◽  
Rural Site ◽  
Data Gap

&lt;p&gt;Ambient air pollution is a leading cause of premature mortality across the world, with an estimated 258,000 deaths in Africa (UNICEF/GBD 2017). These estimated impacts have large uncertainties as many major cities in Africa do not have any ground-based air quality monitoring. The lack of data is due in part to the high cost of traditional monitoring equipment and the lack of trained personnel. As part of the &amp;#8220;Make Air Quality Great Again&amp;#8221; project under the &amp;#8220;Make Our Planet Great Again&amp;#8221; framework (MOPGA), we propose filling this data gap with low-cost sensors carefully calibrated against reference monitors.&lt;/p&gt;&lt;p&gt;Fifteen real-time affordable multi-pollutant (RAMP) monitors have been deployed in Abidjan, C&amp;#244;te d'Ivoire; Accra, Ghana; Kigali, Rwanda; Nairobi, Kenya; Niamey, Niger; and Zamdela, South Africa (near Johannesburg). The RAMPs use Plantower optical nephelometers to measure fine particulate matter mass (PM&lt;sub&gt;2.5&lt;/sub&gt;) and four Alphasense electrochemical sensors to detect pollutant gases including nitrogen dioxide (NO&lt;sub&gt;2&lt;/sub&gt;) and ozone (O&lt;sub&gt;3&lt;/sub&gt;).&lt;/p&gt;&lt;p&gt;Using a calibration developed in Cr&amp;#233;teil, France, the deployments thus far reveal morning and evening spikes in combustion-related air pollution. The median hourly NO&lt;sub&gt;2&lt;/sub&gt; in Accra and Nairobi for September-October 2019 was about 11 ppb; a similar value was observed across November-December 2019 in Zamdela. However, a previous long-term deployment of the RAMPs in Rwanda showed that, for robust data quality, low-cost sensors must be collocated with traditional reference monitors to develop localized calibration models. Hence, we acquired regulatory-grade PM&lt;sub&gt;2.5&lt;/sub&gt;, NO&lt;sub&gt;2&lt;/sub&gt;, and O&lt;sub&gt;3&lt;/sub&gt; monitors for Abidjan and Accra. We also collocated RAMPs with existing reference monitors in Zamdela, Kigali, Abidjan, and Lamto (a rural site in C&amp;#244;te d'Ivoire). In this talk, we will present results on spatio-temporal variability of collocation-based sensor calibrations across these different cities, source identification, and challenges and plans for future expansion.&lt;/p&gt;

scholarly journals Wintertime aerosol chemical composition, volatility, and spatial variability in the greater London area

2015 ◽  
Vol 15 (16) ◽  
pp. 23173-23229
Author(s):  
L. Xu ◽  
L. R. Williams ◽  
D. E. Young ◽  
J. D. Allan ◽  
H. Coe ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Field Studies ◽  
Rural Site ◽  
Urban Site ◽  
High Temporal Resolution ◽  
Volatile Organics ◽  
Mass Spectrometers ◽  
Aerosol Mass ◽  
Rural And Urban ◽  
Wide Range

Abstract. The composition of PM1 (particulate matter with diameter less than 1 μm) in the greater London area was characterized during the Clean Air for London (ClearfLo) project in winter 2012. Two High-Resolution Time-of-Flight Aerosol Mass Spectrometers (HR-ToF-AMS) were deployed at a rural site (Detling, Kent) and an urban site (North Kensington, London). The simultaneous and high-temporal resolution measurements at the two sites provide a unique opportunity to investigate the spatial distribution of PM1. We find that the organic aerosol (OA) concentration is comparable between the rural and urban sites, but the sources of OA are distinctly different. The concentration of solid fuel OA at the urban site is about twice as high as at the rural site, due to elevated domestic heating in the urban area. While the concentrations of oxygenated OA (OOA) are well-correlated between the two sites, the OOA concentration at the rural site is almost twice that of the urban site. At the rural site, more than 70 % of the carbon in OOA is estimated to be non-fossil, which suggests that OOA is likely related to aged biomass burning considering the small amount of biogenic SOA in winter. Thus, it is possible that the biomass burning OA contributes a larger fraction of ambient OA in wintertime than what previous field studies have suggested. A suite of instruments was deployed downstream of a thermal denuder (TD) to investigate the volatility of PM1 species at the rural Detling site. After heating at 250 °C in the TD, 40 % of the residual mass is OA, indicating the presence of non-volatile organics in the aerosol. Although the OA associated with refractory black carbon (rBC, measured by a soot-particle aerosol mass spectrometer) only accounts for < 10 % of the total OA (measured by a HR-ToF-AMS) at 250 °C, the two measurements are well-correlated, suggesting that the non-volatile organics have similar sources or have undergone similar chemical processing as rBC in the atmosphere. Finally, we discuss the relationship between the OA volatility and atomic O : C and find that particles with a wide range of O : C could have similar mass fraction remaining after heating. This analysis emphasizes the importance of understanding the distribution of volatility and O : C in bulk OA.

Visible-light-initiated Catalyst-free Oxidative Cleavage of Triaryl-Substituted Alkenes C=C Bonds under Ambient Conditions

2021 ◽  
Author(s):  
Wenjing Li ◽  
Shun Li ◽  
Lihua Luo ◽  
Yichen Ge ◽  
Jiaqi Xu ◽  
...  
Keyword(s):  
Visible Light ◽  
Room Temperature ◽  
Ambient Air ◽  
Oxidative Cleavage ◽  
Ambient Conditions ◽  
Blue Led ◽  
Catalyst Free

The catalyst-free oxidative cleavage of (Z)-triaryl-substituted alkenes bearing pyridyl motif with ambient air under irradiation of blue LED at room temperature has been developed. The reaction was facile and scalable,...

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