scholarly journals Improved chloride quantification in quadrupole aerosol chemical speciation monitors (Q-ACSMs)

2020 ◽  
Author(s):  
Anna K. Tobler ◽  
Alicja Skiba ◽  
Dongyu S. Wang ◽  
Philip Croteau ◽  
Katarzyna Styszko ◽  
...  
Keyword(s):  
Chemical Speciation ◽  
Anthropogenic Activities ◽  
Chloride Concentration ◽  
Ambient Air ◽  
Aerosol Composition ◽  
Total Chloride ◽  
Ambient Aerosol ◽  
Positive Difference ◽  
The Difference

Abstract. Particulate chloride is an important component of fine particulate matter in marine air masses. Recent field studies also report elevated concentrations of gas-phase reactive chlorine species and particulate chloride related to anthropogenic activities. This work focuses on particulate chloride detection and quantification issues observed for some quadrupole aerosol chemical speciation monitors (Q-ACSM), which are designed for long-term measurement of ambient aerosol composition. The ACSM reports particle concentrations based on the difference between measurements of ambient air (sample mode) and particle-free ambient air (filter mode). For our long-term campaign in Krakow, Poland, the Q-ACSM reports apparent negative total chloride concentration for most of the campaign when analyzed with the default fragmentation table. This is the result of the difference signal from m/z 35 (35Cl+) being negative which dominates over the positive difference signal from m/z 36 (H35Cl+). Highly time-resolved experiments with NH4Cl, NaCl and KCl particles show that the signal response of m/z 35 is non-ideal, where the signal builds up and decreases slowly for all three salts, leading to a negative difference measurement. In contrast, the m/z 36 signal exhibits a near step-change response for NH4Cl during sampling and filter period, resulting in a positive difference signal. The response of m/z 36 for NaCl and KCl is not as prompt as for NH4Cl but still fast enough to have a positive difference signal. Furthermore, it is shown that this behavior is mostly temperature-independent. Based on these observations, this work presents an approach to correct the chloride concentration time series by adapting the standard fragmentation table coupled with a calibration of NH4Cl to obtain a relative ionization efficiency (RIE) based on the signal at m/z 36 (H35Cl+). This correction can be applied for measurements in environments where chloride is dominated by NH4Cl. Caution should be exercised when other chloride salts dominate the ambient aerosol.

scholarly journals Improved chloride quantification in quadrupole aerosol chemical speciation monitors (Q-ACSMs)

2020 ◽  
Vol 13 (10) ◽  
pp. 5293-5301
Author(s):  
Anna K. Tobler ◽  
Alicja Skiba ◽  
Dongyu S. Wang ◽  
Philip Croteau ◽  
Katarzyna Styszko ◽  
...  
Keyword(s):  
Chemical Speciation ◽  
Anthropogenic Activities ◽  
Fine Particulate Matter ◽  
Chloride Concentration ◽  
Ambient Air ◽  
Aerosol Composition ◽  
Total Chloride ◽  
Positive Difference ◽  
The Difference

Abstract. Particulate chloride is an important component of fine particulate matter in marine air masses. Recent field studies also report elevated concentrations of gas-phase reactive chlorine species and particulate chloride related to anthropogenic activities. This work focuses on particulate chloride detection and quantification issues observed for some quadrupole aerosol chemical speciation monitors (Q-ACSMs) which are designed for the long-term measurement of ambient aerosol composition. The ACSM reports particle concentrations based on the difference between measurements of ambient air (sample mode) and particle-free ambient air (filter mode). For our long-term campaign in Krakow, Poland, the Q-ACSM reports apparent negative total chloride concentration for most of the campaign when analyzed with the default fragmentation table. This is the result of the difference signal from m∕z 35 (35Cl+) being negative, which dominates over the positive difference signal from m∕z 36 (H35Cl+). Highly time-resolved experiments with NH4Cl, NaCl and KCl particles show that the signal response of m∕z 35 is non-ideal when the signal builds up and decreases slowly for all three salts, leading to a negative difference measurement. In contrast, the m∕z 36 signal exhibits a near step-change response for NH4Cl during the sampling and filter period, resulting in a positive difference signal. The response of m∕z 36 for NaCl and KCl is not as prompt as for NH4Cl but still fast enough to have a positive difference signal. Furthermore, it is shown that this behavior is mostly independent of vaporizer temperature. Based on these observations, this work presents an approach to correct the chloride concentration time series by adapting the standard fragmentation table coupled with a calibration of NH4Cl to obtain a relative ionization efficiency (RIE) based on the signal at m∕z 36 (H35Cl+). This correction can be applied to measurements in environments where chloride is dominated by NH4Cl. Caution should be exercised when other chloride salts dominate the ambient particulate chloride.

scholarly journals The ToF-ACSM: a portable aerosol chemical speciation monitor with TOFMS detection

2013 ◽  
Vol 6 (11) ◽  
pp. 3225-3241 ◽  
Author(s):  
R. Fröhlich ◽  
M. J. Cubison ◽  
J. G. Slowik ◽  
N. Bukowiecki ◽  
A. S. H. Prévôt ◽  
...  
Keyword(s):  
Chemical Speciation ◽  
Time Of Flight ◽  
Mass Resolution ◽  
Remote Access ◽  
Swiss Alps ◽  
Scanning Mobility Particle Sizer ◽  
Aerosol Composition ◽  
Flight Mass Spectrometry ◽  
New Instrument

Abstract. We present a new instrument for monitoring aerosol composition, the time-of-flight aerosol chemical speciation monitor (ToF-ACSM), combining precision state-of-the-art time-of-flight mass spectrometry with stability, reliability, and easy handling, which are necessities for long-term monitoring operations on the scale of months to years. Based on Aerodyne aerosol mass spectrometer (AMS) technology, the ToF-ACSM provides continuous online measurements of chemical composition and mass of non-refractory submicron aerosol particles. In contrast to the larger AMS, the compact-sized and lower-priced ToF-ACSM does not feature particle sizing, similar to the widely-used quadrupole-ACSM (Q-ACSM). Compared to the Q-ACSM, the ToF-ACSM features a better mass resolution of M/ΔM = 600 and better detection limits on the order of < 30 ng m−3 for a time resolution of 30 min. With simple upgrades these limits can be brought down by another factor of ~ 8. This allows for operation at higher time resolutions and in low concentration environments. The associated software packages (single packages for integrated operation and calibration and analysis) provide a high degree of automation and remote access, minimising the need for trained personnel on site. Intercomparisons with Q-ACSM, C-ToF-AMS, nephelometer and scanning mobility particle sizer (SMPS) measurements, performed during a first long-term deployment (> 10 months) on the Jungfraujoch mountain ridge (3580 m a.s.l.) in the Swiss Alps, agree quantitatively. Additionally, the mass resolution of the ToF-ACSM is sufficient for basic mass defect resolved peak fitting of the recorded spectra, providing a data stream not accessible to the Q-ACSM. This allows for quantification of certain hydrocarbon and oxygenated fragments (e.g. C3H7+ and C2H3O+, both occurring at m/Q = 43 Th), as well as improving inorganic/organic separation.

scholarly journals The ToF-ACSM: a portable aerosol chemical speciation monitor with TOFMS detection

2013 ◽  
Vol 6 (4) ◽  
pp. 6767-6814 ◽  
Author(s):  
R. Fröhlich ◽  
M. J. Cubison ◽  
J. G. Slowik ◽  
N. Bukowiecki ◽  
A. S. H. Prévôt ◽  
...  
Keyword(s):  
Chemical Speciation ◽  
Time Of Flight ◽  
Mass Resolution ◽  
Remote Access ◽  
Swiss Alps ◽  
Scanning Mobility Particle Sizer ◽  
Aerosol Composition ◽  
Flight Mass Spectrometry ◽  
New Instrument

Abstract. We present a new instrument for monitoring aerosol composition, the economy time-of-flight-aerosol chemical speciation monitor (ToF-ACSM), combining precision of state-of-the-art time-of-flight mass spectrometry with stability, reliability, and easy handling, which are necessities for long-term monitoring operations on the scale of months to years. Based on Aerodyne aerosol mass spectrometer (AMS) technology, the ToF-ACSM provides continuous online measurements of chemical composition and mass of non-refractory submicron aerosol particles. In contrast to the larger AMS, the compact-sized and lower-priced ToF-ACSM does not feature particle sizing, similar to the widely-used quadrupole-ACSM (Q-ACSM). Compared to the Q-ACSM, the ToF-ACSM features a better mass resolution of M/ΔM = 600 and better detection limits on the order of <30 ng m−3 for a time resolution of 30 min. With simple upgrades these limits can be brought down by another factor of ~8. This allows for operation at higher time resolutions and in low concentration environments. The associated software packages (single packages for integrated operation &amp; calibration and analysis) provide a high degree of automation and remote access, minimising the need for trained personnel on site. Intercomparisons with Q-ACSM, C-ToF-AMS, nephelometer and scanning mobility particle sizer (SMPS) measurements, performed during a first long-term deployment (>6 months) on the Jungfraujoch mountain ridge (3580 m a.s.l.) in the Swiss Alps agree quantitatively. Additionally, the mass resolution of the ToF-ACSM is sufficient for basic mass defect resolved peak fitting of the recorded spectra, providing a data stream not accessible to the Q-ACSM. This allows for quantification of certain hydrocarbon and oxygenated fragments (e.g. C3H7+ and C2H3O+, both occurring at m/Q = 43 Th), as well as improving inorganic/organic separation.

The Expression of Surface Chloride Concentration in Ecological Concrete and Service Life Prediction

2011 ◽  
Vol 368-373 ◽  
pp. 2204-2210 ◽  
Author(s):  
Si Feng Liu
Keyword(s):  
Fly Ash ◽  
Service Life ◽  
Life Prediction ◽  
Chloride Concentration ◽  
Total Chloride ◽  
One Dimensional ◽  
Dimensional Diffusion ◽  
Diffusion Depth ◽  
Chloride Concentrations

The total chloride concentrations of concrete with 0.51 of water to cementitous from three contents of Fly ash, GGBS, two kinds of corrosion solution for one dimensional diffusion at different diffusion depth and time were measured by chemical titration. The influence of Fly ash and GGBS content on total chloride concentration and the surface chloride concentration were analyzed. The expressions of the surface chloride concentration were discussed in terms of the experimental results related with content of Fly ash, GGBS and solution. The numerical analysis results indicated that the expression of the surface chloride concentration has a significant impact on the long-term service life of concrete in chloride environments.

scholarly journals Long-term steady state <sup>13</sup>C labelling to investigate carbon turnover in plant soil systems

2007 ◽  
Vol 4 (2) ◽  
pp. 797-821 ◽  
Author(s):  
K. Klumpp ◽  
J. F. Soussana ◽  
R. Falcimagne
Keyword(s):  
Steady State ◽  
Urban Areas ◽  
Co2 Concentration ◽  
Ambient Air ◽  
Organic C ◽  
Plant Soil ◽  
Soil Systems ◽  
The Mean ◽  
The Difference

Abstract. We have set up a facility allowing steady state 13CO2 labeling of short stature vegetation (12 m2) for several years. 13C labelling is obtained by scrubbing the CO2 from outdoors air with a self-regenerating molecular sieve and by replacing it with 13C depleted (−34.7±0.03‰) fossil-fuel derived CO2 The facility, which comprises 16 replicate mesocosms, allows tracing the fate of photosynthetic carbon in plant-soil systems in natural light and at outdoors temperature. This method was applied during 2 yrs to temperate grassland monoliths (0.5×0.5×0.4 m) sampled in a long term grazing experiment. During daytime, the canopy enclosure in each mesocosm was supplied in an open flow (0.67–0.88 volume per minute) with modified air (43% scrubbed air and 57% cooled and humidified ambient air) at mean CO2 concentration of 425 µmol mol−1 and δ13C of −21.5±0.27‰. Above and belowground CO2 fluxes were continuously monitored. The difference in δ13C between the CO2 at the outlet and at the inlet of each canopy enclosure was not significant (−0.35±0.39‰). Due to mixing with outdoors air, the CO2 concentration at enclosure inlet followed a seasonal cycle, often found in urban areas, where δ13C of CO2 is lower in winter than in summer. Mature C3 grass leaves were sampled monthly in each mesocosm, as well as leave from pot-grown control C4 (Paspalum dilatatum). The mean δ13C of fully labelled C3 and C4 leaves reached −41.4±0.67 and −28.7±0.39‰ respectively. On average, the labelling reduced by 12.7‰ the δ13C of C3 grass leaves. The isotope mass balance technique was used to calculate the fraction of "new" C in the soil organic matter (SOM) above 0.2 mm. A first order exponential decay model fitted to "old" C data showed that reducing aboveground disturbance by cutting increased from 22 to 31 months the mean residence time of belowground organic C (>0.2 mm) in the top soil.

41. Diffusion Badges as a Long-Term, Low-Level Method of Ambient Air Analysis

2005 ◽  
Author(s):  
K. Parker ◽  
S. Rose-Pehrsson ◽  
D. Kidwell
Keyword(s):  
Ambient Air ◽  
Air Analysis ◽  
Low Level ◽  
Level Method

A Problem of Long - Term Digital Preservation: Difference in Humanities and Natural Sciences

2014 ◽  
Vol 3 ◽  
pp. 183-195
Author(s):  
Elena Macevičiūtė
Keyword(s):  
Social Sciences ◽  
Digital Preservation ◽  
Dynamic Activity ◽  
Private Companies ◽  
Time Line ◽  
Digital Documents ◽  
Whole Process ◽  
The Difference ◽  
Technological Science

The article deals with the requirements and needs for long-term digital preservation in different areas of scholarly work. The concept of long-term digital preservation is introduced by comparing it to digitization and archiving concepts and defined with the emphasis on dynamic activity within a certain time line. The structure of digital preservation is presented with regard to the elements of the activity as understood in Activity Theory. The life-cycle of digitization processes forms the basis of the main processing of preserved data in preservation archival system.The author draws on the differences between humanities and social sciences on one hand and natural and technological science on the other. The empirical data characterizing the needs for digital preservation within different areas of scholarship are presented and show the difference in approaches to long-term digital preservation, as well as differences in selecting the items and implementing the projects of digital preservation. Institutions and organizations can also develop different understanding of preservation requirements for digital documents and other objects.The final part of the paper is devoted to some general problems pertaining to the longterm digital preservation with the emphasis of the responsibility for the whole process of safe-guarding the cultural and scholarly heritage for the re-use of the posterior generations. It is suggested that the longevity of the libraries in comparison with much shorter life-span of private companies strengthens the claim of memory institutions to playing the central role in the long-term digital preservation.

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