scholarly journals Application of an online ion-chromatography-based instrument for gradient flux measurements of speciated nitrogen and sulfur

2016 ◽  
Vol 9 (6) ◽  
pp. 2581-2592 ◽  
Author(s):  
Ian C. Rumsey ◽  
John T. Walker
Keyword(s):  
Ion Chromatography ◽  
Concentration Gradient ◽  
Sampling Site ◽  
Measurement Techniques ◽  
Ambient Air ◽  
Chemical Concentration ◽  
Concentration Gradients ◽  
Transfer Velocity ◽  
Surface Exchange ◽  
Chemical Concentration Gradient

Abstract. The dry component of total nitrogen and sulfur atmospheric deposition remains uncertain. The lack of measurements of sufficient chemical speciation and temporal extent make it difficult to develop accurate mass budgets and sufficient process level detail is not available to improve current air–surface exchange models. Over the past decade, significant advances have been made in the development of continuous air sampling measurement techniques, resulting with instruments of sufficient sensitivity and temporal resolution to directly quantify air–surface exchange of nitrogen and sulfur compounds. However, their applicability is generally restricted to only one or a few of the compounds within the deposition budget. Here, the performance of the Monitor for AeRosols and GAses in ambient air (MARGA 2S), a commercially available online ion-chromatography-based analyzer is characterized for the first time as applied for air–surface exchange measurements of HNO3, NH3, NH4+, NO3−, SO2 and SO42−. Analytical accuracy and precision are assessed under field conditions. Chemical concentrations gradient precision are determined at the same sampling site. Flux uncertainty measured by the aerodynamic gradient method is determined for a representative 3-week period in fall 2012 over a grass field. Analytical precision and chemical concentration gradient precision were found to compare favorably in comparison to previous studies. During the 3-week period, percentages of hourly chemical concentration gradients greater than the corresponding chemical concentration gradient detection limit were 86, 42, 82, 73, 74 and 69 % for NH3, NH4+, HNO3, NO3−, SO2 and SO42−, respectively. As expected, percentages were lowest for aerosol species, owing to their relatively low deposition velocities and correspondingly smaller gradients relative to gas phase species. Relative hourly median flux uncertainties were 31, 121, 42, 43, 67 and 56 % for NH3, NH4+, HNO3, NO3−, SO2 and SO42−, respectively. Flux uncertainty is dominated by uncertainty in the chemical concentrations gradients during the day but uncertainty in the chemical concentration gradients and transfer velocity are of the same order at night. Results show the instrument is sufficiently precise for flux gradient applications.

scholarly journals Application of an online ion chromatography-based instrument for gradient flux measurements of speciated nitrogen and sulfur

2016 ◽  
Author(s):  
Ian C. Rumsey ◽  
John T. Walker
Keyword(s):  
Ion Chromatography ◽  
Concentration Gradient ◽  
Sampling Site ◽  
Measurement Techniques ◽  
Ambient Air ◽  
Chemical Concentration ◽  
Concentration Gradients ◽  
Transfer Velocity ◽  
Surface Exchange ◽  
Chemical Concentration Gradient

Abstract. The dry component of total nitrogen and sulfur atmospheric deposition remains uncertain. The lack of measurements of sufficient chemical speciation and temporal extent make it difficult to develop accurate mass budgets and sufficient process level detail is not available to improve current air-surface exchange models. Over the past decade, significant advances have been made in the development of continuous air sampling measurement techniques, resulting with instruments of sufficient sensitivity and temporal resolution to directly quantify air-surface exchange of nitrogen and sulfur compounds. However, their applicability is generally restricted to only one or a few of the compounds within the de position budget. Here, the performance of the Monitor for AeRosols and GAses in ambient air (MARGA 2S), an commercially available on-line ion chromatography-based analyzer is characterized for the first time as applied for air-surface exchange measurements of HNO3, NH3, NH4+, NO3−, SO2 and SO42−. Analytical accuracy and precision are assessed under field conditions. Chemical concentrations gradient precision are determined at the same sampling site. Flux uncertainty measured by the aerodynamic gradient method is determined for a representative 3-week period in fall 2012 over a grass field. Analytical precision and chemical concentration gradient precision were found to compare favorably in comparison to previous studies. During the 3-week period, percentages of hourly chemical concentration gradients greater than the corresponding chemical concentration gradient detection limit were 86 %, 42 %, 82 %, 73 %, 74 %, and 69 % for NH3, NH4+, HNO3, NO3−, SO2, and SO42−, respectively. As expected, percentages were lowest for aerosol species, owing to their relatively low deposition velocities and correspondingly smaller gradients relative to gas phase species. Relative hourly median flux uncertainties were 31 %, 121 %, 42 %, 43 %, 67 %, and 56 % for NH3, NH4+, HNO3, NO3−, SO2, and SO42−, respectively. Flux uncertainty is dominated by uncertainty in the chemical concentrations gradients during the day but uncertainty in the chemical concentration gradients and transfer velocity are of the same order at night. Results show the instrument is sufficiently precise for flux gradient applications.

scholarly journals Brazil Nut Effect Drives Pattern Formation in Early Mammalian Embryos

2021 ◽  
Author(s):  
Zheng Guo ◽  
Jie Yao ◽  
Xu Zheng ◽  
Jialing Cao ◽  
Zheng Gao ◽  
...  
Keyword(s):  
Pattern Formation ◽  
Embryonic Development ◽  
Concentration Gradient ◽  
Mechanical Energy ◽  
Chemical Concentration ◽  
Brazil Nut ◽  
Cavity Structure ◽  
Mammalian Embryos ◽  
Brazil Nut Effect ◽  
Chemical Concentration Gradient

ABSTRACTThe formation of three-dimensional ordered spatial patterns, which is essential for embryonic development, tissue regeneration, and cancer metastasis, is mainly guided by the chemical concentration gradient of morphogens. However, since no chemical concentration gradient has been observed in the early embryonic development (pre-implantation) of mammals, the pattern formation mechanism has been unsolved for a long time. During the second cell fate decision of mouse embryos, the inner cell mass (ICM) segregates into topographically regionalized epiblast (EPI) and primitive endoderm (PrE) layers. Here, we report that the segregation process of PrE/EPI precursors coincides with an emerged periodic expansion-contraction vibration of the blastocyst cavity, which induces phase transition in the ICM compartment to a higher fluidity state and generates directional tissue flows. By experiments and modeling, we demonstrate that the spatial segregation of PrE and EPI precursors is mediated by a “Brazil nut effect”-like viscous segregation mechanism in which PrE precursors with low affinity gradually migrate to the surface of ICM along with the tissue flow, while EPI precursors with high affinity remains inside ICM under cavity vibration. Artificially manipulation of the frequency and amplitude of cavity vibration could control the process of spatial separation as well as lineage specification of PrE/EPI. Furthermore, disruption of the cavity vibration in the initial stage after segregation could reverse the ICM cells back to a mixed state. Therefore, this study reveals a fundamental mechanism that guarantees the robustness of cell segregation and pattern formation without specific morphogens in early mammalian embryos. Our model also emphasizes a conserved function of cavity structure that widely exists in organisms as an energy reservoir and converter between different forms, such as chemical and mechanical energy.

Field intercomparison of measurement techniques for total NH4+ and total NO3− in ambient air

1988 ◽  
Vol 22 (10) ◽  
pp. 2275-2281 ◽  
Author(s):  
M. Ferm ◽  
H. Areskoug ◽  
J.-E. Hanssen ◽  
G. Hilbert ◽  
H. Lättilä
Keyword(s):  
Measurement Techniques ◽  
Ambient Air ◽  
Field Intercomparison

scholarly journals Comparison of continuous in-situ CO<sub>2</sub> observations at Jungfraujoch using two different measurement techniques

2014 ◽  
Vol 7 (7) ◽  
pp. 7053-7084
Author(s):  
M. F. Schibig ◽  
M. Steinbacher ◽  
B. Buchmann ◽  
I. T. van der Laan-Luijkx ◽  
S. van der Laan ◽  
...  
Keyword(s):  
Materials Science ◽  
Measurement Techniques ◽  
Ambient Air ◽  
Pollution Monitoring ◽  
Smooth Transition ◽  
Research Station ◽  
Short Term ◽  
Technical Problems ◽  
Two Systems ◽  
Data Coverage

Abstract. Since 2004, atmospheric carbon dioxide (CO2) is measured at the High Altitude Research Station Jungfraujoch by the division of Climate and Environmental Physics at the University of Bern (KUP) using a nondispersive infrared gas analyzer (NDIR) in combination with a paramagnetic O2 analyzer. In January 2010, CO2 measurements based on cavity ring down spectroscopy (CRDS) as part of the Swiss National Air Pollution Monitoring Network have been added by the Swiss Federal Laboratories for Materials Science and Technology (Empa). To ensure a smooth transition – a prerequisite when merging two datasets e.g. for trend determinations – the two measurement systems run in parallel for several years. Such a long-term intercomparison also allows identifying potential offsets between the two datasets and getting information about the compatibility of the two systems on different time scales. A good agreement of the seasonality as well as for the short-term variations was observed and to a lesser extent for trend calculations mainly due to the short common period. However, the comparison revealed some issues related to the stability of the calibration gases of the KUP system and their assigned CO2 mole fraction. It was possible to adapt an improved calibration strategy based on standard gas determinations, which lead to better agreement between the two data sets. By excluding periods with technical problems and bad calibration gas cylinders, the average hourly difference (CRDS − NDIR) of the two systems is −0.03 ppm ± 0.25 ppm. Although the difference of the two datasets is in line with the compatibility goal of ±0.1 ppm of the World Meteorological Organization (WMO), the standard deviation is still too high. A significant part of this uncertainty originates from the necessity to switch the KUP system frequently (every 12 min) for 6 min from ambient air to a working gas in order to correct short-term variations of the O2 measurement system. Allowing additionally for signal stabilization after switching the sample, an effective data coverage of only 1/6 for the KUP system is achieved while the Empa system has a nearly complete data coverage. Additionally, different internal volumes and flow rates between the two systems may affect observed differences.

Air of the Anthropocene

2021 ◽  
Author(s):  
Francis Pope ◽  
Robin Price
Keyword(s):  
Air Pollution ◽  
Los Angeles ◽  
Low Cost ◽  
Measurement Techniques ◽  
Transformational Change ◽  
Ambient Air ◽  
Expert Advice ◽  
Light Sources ◽  
Anthropogenic Contamination ◽  
Science Collaboration

&lt;p&gt;Anthropogenic contamination of the atmosphere is causing both climate change and air pollution, which respectively represent the greatest long term and short term environmental risks to human and planetary health. The contamination is largely invisible and hence difficult to contextualise for non-expert audiences. This can lead to the problem being ignored; or where it is acknowledged, leading to feelings of helplessness and a lack of agency.&lt;/p&gt;&lt;p&gt;This project uses digital light painting to visualise and explore responses to particulate matter (PM) air pollution, in a variety of global locations, as a method for both public engagement and campaign work. This photographic technique combines long exposure with light sources digitally controlled by sensors, it builds upon the prior work of electronic pioneer Steve Mann (e.g. Mann et al. 2019) and more recent work visualising wifi strength (Arnall et al. 2013).&lt;/p&gt;&lt;p&gt;The five year art-science collaboration between Price and Pope has been highly successful. The Air of the Anthropocene project resulted in multiple gallery shows (including Los Angeles, Belfast and Birmingham). The media publicized it heavily, including Source Magazine, New Scientist and the Guardian. The physical art works were acquired by the Arts Council of Northern Ireland&amp;#8217;s public collection.&lt;/p&gt;&lt;p&gt;In this presentation, we will highlight the scientific and aesthetic underpinnings of the use of low cost air pollution sensors for data visualisation through light painting. Locations for visualizations were guided by expert advice from environmental scientists in global locations, including those in Europe, Africa, Asia and South America. In this sense the science informed the art. Also, since the code from the project ended being used by scientists, the art informed the science (e.g. Crilley et al. 2018).&lt;/p&gt;&lt;p&gt;We will highlight the efficacy of this image making approach as an engagement and advocacy tool, through case studies of its use in field campaigns in Ethiopia (2020) and Kampala (2018), investigating both indoor and outdoor air pollution.&amp;#160; Future possibilities of the approach to air pollution visualization will be discussed. This will include expanding the approach through open sourcing the project and its adaptation beyond lens based techniques into augmented reality camera phone use.&lt;/p&gt;&lt;p&gt;The projected next phase of the collaboration will work towards empowering interested citizens of the world to make their own creative, aesthetic representations of their environment and use these images as citizen activists to affect transformational change in their own localities. Through adopting open source methodologies it is hoped that sustainability beyond the timescale and budget of the initial project with lasting legacy will be achieved.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Arnall et al, 2013. Immaterials: light painting WiFi. Significance, 10(4). https://doi.org/10.1111/j.1740-9713.2013.00683.x&amp;#160;&lt;/p&gt;&lt;p&gt;Crilley et al, 2018. Evaluation of a low-cost optical particle counter (Alphasense OPC-N2) for ambient air monitoring. Atmospheric Measurement Techniques. https://doi.org/10.5194/amt-11-709-2018&amp;#160;&lt;/p&gt;&lt;p&gt;Mann et al 2019, June. Making Sensors Tangible with Long-exposure Photography. In The 5th ACM Workshop on Wearable Systems and Applications. https://doi.org/10.1145/3325424.3329668&lt;/p&gt;

scholarly journals Evaluating the measurement interference of wet rotating-denuder–ion chromatography in measuring atmospheric HONO in a highly polluted area

2019 ◽  
Vol 12 (12) ◽  
pp. 6737-6748 ◽  
Author(s):  
Zheng Xu ◽  
Yuliang Liu ◽  
Wei Nie ◽  
Peng Sun ◽  
Xuguang Chi ◽  
...  
Keyword(s):  
Ion Chromatography ◽  
Atmospheric Chemistry ◽  
Eastern China ◽  
Ambient Air ◽  
Absorption Efficiency ◽  
Water Soluble ◽  
East China ◽  
Oh Radicals ◽  
Ambient Atmosphere ◽  
High Concentrations

Abstract. Due to the important contribution of nitrous acid (HONO) to OH radicals in the atmosphere, various technologies have been developed to measure HONO. Among them, wet-denuder–ion-chromatography (WD/IC) is a widely used measurement method. Here, we found interferences with HONO measurements by WD/IC based on a comparison study of concurrent observations of HONO concentrations using a WD/IC instrument (Monitor for AeRosols and Gases in ambient Air, MARGA) and long-path absorption photometer (LOPAP) at the Station for Observing Regional Processes of the Earth System (SORPES) in eastern China. The measurement deviation of the HONO concentration with the MARGA instrument, as a typical instrument for WD/IC, is affected by two factors. One is the change in denuder pH influenced by acidic and alkaline gases in the ambient atmosphere, which can affect the absorption efficiency of HONO by the wet denuder to underestimate the HONO concentration by up to 200 % at the lowest pH. The other is the reaction of NO2 oxidizing SO2 to form HONO in the denuder solution to overestimate the HONO concentration, which can be increased by to 400 % in denuder solutions with the highest pH values due to ambient NH3. These processes are in particularly important in polluted east China, which suffers from high concentrations of SO2, NH3, and NO2. The overestimation induced by the reaction of NO2 and SO2 is expected to be of growing importance with the potentially increased denuder pH due to the decrease in SO2. We further established a method to correct the HONO data measured by a WD/IC instrument such as the MARGA. In case a large amount WD/IC-technique-based instruments are deployed with the main target of monitoring the water-soluble composition of PM2.5, our study can help to obtain a long-term multi-sites database of HONO to assess the role of HONO in atmospheric chemistry and air pollution in east China.

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