scholarly journals Application of a GC-ECD for measurements of biosphere–atmosphere exchange fluxes of peroxyacetyl nitrate using the relaxed eddy accumulation and gradient method

2014 ◽  
Vol 7 (2) ◽  
pp. 1917-1974 ◽  
Author(s):  
A. Moravek ◽  
T. Foken ◽  
I. Trebs
Keyword(s):  
Measurement System ◽  
Current Knowledge ◽  
Flux Measurement ◽  
Bowen Ratio ◽  
Terrestrial Ecosystems ◽  
Fast Response ◽  
Electron Capture Detection ◽  
Mixing Ratio ◽  
Peroxyacetyl Nitrate ◽  
Relaxed Eddy Accumulation

Abstract. Peroxyacetyl nitrate (PAN) may constitute a significant fraction of reactive nitrogen in the atmosphere. Current knowledge about the biosphere–atmosphere exchange of PAN is limited and only few studies have investigated the deposition of PAN to terrestrial ecosystems. We developed a flux measurement system for the determination of biosphere–atmosphere exchange fluxes of PAN using both the hyperbolic relaxed eddy accumulation (HREA) method and the modified Bowen ratio (MBR) method. The system consists of a modified, commercially available gas chromatograph with electron capture detection (GC-ECD, Meteorologie Consult GmbH, Germany). Sampling was performed by trapping PAN onto two pre-concentration columns; during HREA operation one was used for updraft and one for downdraft events and during MBR operation the two columns allowed simultaneous sampling at two measurement heights. The performance of the PAN flux measurement system was tested at a natural grassland site, using fast response ozone (O3) measurements as a proxy for both methods. The measured PAN fluxes were comparatively small (daytime PAN deposition was on average −0.07 nmol m−2 s−1 and, thus, prone to significant uncertainties. A major challenge in the design of the system was the resolution of the small PAN mixing ratio differences. Consequently, the study focuses on the performance of the analytical unit and a detailed analysis of errors contributing to the overall uncertainty. The error of the PAN mixing ratio differences ranged from 4 to 15 ppt during the MBR and between 18 and 26 ppt during the HREA operation, while during daytime measured PAN mixing ratios were of similar magnitude. Choosing optimal settings for both the MBR and HREA method, the study shows that the HREA method did not have a significant advantage towards the MBR method under well mixed conditions as it was expected.

scholarly journals Application of a GC-ECD for measurements of biosphere–atmosphere exchange fluxes of peroxyacetyl nitrate using the relaxed eddy accumulation and gradient method

2014 ◽  
Vol 7 (7) ◽  
pp. 2097-2119 ◽  
Author(s):  
A. Moravek ◽  
T. Foken ◽  
I. Trebs
Keyword(s):  
Measurement System ◽  
Current Knowledge ◽  
Flux Measurement ◽  
Bowen Ratio ◽  
Terrestrial Ecosystems ◽  
Fast Response ◽  
Electron Capture Detection ◽  
Mixing Ratio ◽  
Peroxyacetyl Nitrate ◽  
Relaxed Eddy Accumulation

Abstract. Peroxyacetyl nitrate (PAN) may constitute a significant fraction of reactive nitrogen in the atmosphere. Current knowledge about the biosphere–atmosphere exchange of PAN is limited, and only few studies have investigated the deposition of PAN to terrestrial ecosystems. We developed a flux measurement system for the determination of biosphere–atmosphere exchange fluxes of PAN using both the hyperbolic relaxed eddy accumulation (HREA) method and the modified Bowen ratio (MBR) method. The system consists of a modified, commercially available gas chromatograph with electron capture detection (GC-ECD, Meteorologie Consult GmbH, Germany). Sampling was performed by trapping PAN onto two pre-concentration columns; during HREA operation one was used for updraft and one for downdraft events, and during MBR operation the two columns allowed simultaneous sampling at two measurement heights. The performance of the PAN flux measurement system was tested at a natural grassland site, using fast-response ozone (O3) measurements as a proxy for both methods. The measured PAN fluxes were comparatively small (daytime PAN deposition was on average −0.07 nmol m−2 s−1) and, thus, prone to significant uncertainties. A major challenge in the design of the system was the resolution of the small PAN mixing ratio differences. Consequently, the study focuses on the performance of the analytical unit and a detailed analysis of errors contributing to the overall uncertainty. The error of the PAN mixing ratio differences ranged from 4 to 15 ppt during the MBR and between 18 and 26 ppt during the HREA operation, while during daytime measured PAN mixing ratios were of similar magnitude. Choosing optimal settings for both the MBR and HREA method, the study shows that the HREA method did not have a significant advantage towards the MBR method under well-mixed conditions as was expected.

CCD flux measurement system PROHERMES

1999 ◽  
Vol 09 (PR3) ◽  
pp. Pr3-649-Pr3-654 ◽  
Author(s):  
A. Kröger-Vodde ◽  
A. Holländer
Keyword(s):  
Measurement System ◽  
Flux Measurement

scholarly journals Mercury vapor air–surface exchange measured by collocated micrometeorological and enclosure methods – Part II: Bias and uncertainty analysis

2015 ◽  
Vol 15 (4) ◽  
pp. 4627-4676
Author(s):  
W. Zhu ◽  
J. Sommar ◽  
C.-J. Lin ◽  
X. Feng
Keyword(s):  
Flux Measurement ◽  
Bowen Ratio ◽  
Vertical Gradient ◽  
Systematic Evaluation ◽  
Data Set ◽  
Surface Exchange ◽  
Concentration Difference ◽  
Vegetation Height ◽  
Gradient Based ◽  
Flux Quantification

Abstract. Dynamic flux chambers (DFCs) and micrometeorological (MM) methods are extensively deployed for gauging air–surface Hg0 gas exchange. However, a systematic evaluation of the precision of the contemporary Hg0 flux quantification methods is not available. In this study, the uncertainty in Hg0 flux measured by relaxed eddy accumulation (REA) method, aerodynamic gradient method (AGM), modified Bowen-ratio (MBR) method, as well as DFC of traditional (TDFC) and novel (NDFC) designs is assessed using a robust data-set from two field intercomparison campaigns. The absolute precision in Hg0 concentration difference (Δ C) measurements is estimated at 0.064 ng m−3 for the gradient-based MBR and AGM system. For the REA system, the parameter is Hg0 concentration (C) dependent at 0.069+0.022C. 57 and 62% of the individual vertical gradient measurements were found to be significantly different from zero during the campaigns, while for the REA-technique the percentage of significant observations was lower. For the chambers, non-significant fluxes are confined to a few nighttime periods with varying ambient Hg0 concentration. Relative bias for DFC-derived fluxes is estimated to be ~ ±10%, and ~ 85% of the flux bias are within ±2 ng m−2 h−1 in absolute term. The DFC flux bias follows a diurnal cycle, which is largely dictated by temperature controls on the enclosed volume. Due to contrasting prevailing micrometeorological conditions, the relative uncertainty (median) in turbulent exchange parameters differs by nearly a factor of two between the campaigns, while that in Δ C measurements is fairly stable. The estimated flux uncertainties for the triad of MM-techniques are 16–27, 12–23 and 19–31% (interquartile range) for the AGM, MBR and REA method, respectively. This study indicates that flux-gradient based techniques (MBR and AGM) are preferable to REA in quantifying Hg0 flux over ecosystems with low vegetation height. A limitation of all Hg0 flux measurement systems investigated is their incapability to obtain synchronous samples for the calculation of Δ C. This reduces the precision of flux quantification, particularly the MM-systems under non-stationarity of ambient Hg0 concentration. For future applications, it is recommended to accomplish Δ C derivation from simultaneous collected samples.

Possible Implementation of Ex-core Measurement in TEPLATOR Graphite Reflector

2021 ◽  
Author(s):  
Eva Vilimova ◽  
Tomas Peltan ◽  
Jana Jiricková
Keyword(s):  
Neutron Flux ◽  
District Heating ◽  
Flux Measurement ◽  
Heating System ◽  
Fast Response ◽  
Reactor Power ◽  
Measuring System ◽  
Monte Carlo Code ◽  
District Heating System ◽  
And Control

Abstract An ex-core neutron flux measurement is a crucial system for all common power reactors. It is necessary to monitor the neutron flux and control the chain reaction, therefore the ex-core neutron flux measurement is one of the main safety and control systems. The main advantage of this arrangement of detectors is a fast response to neutron flux change, which determines the reactor power change. Regarding to the new reactor concepts, it is important to deal with improved detection systems suitable for these reactors. Many of the modern reactor concepts are based on a graphite moderator or reflector, which is also the case of the TEPLATOR. The TEPLATOR is a solution of a district heating system based on heavy water as a moderator and graphite as a reflector. The TEPLATOR is designed to use irradiated fuel from the commercial PWR or BWR reactors, which has low to intermediate burnup. This article is focused on the verification of the possible use of the special neutron measuring system placed in the graphite reflector. The Monte Carlo code Serpent was used for the calculations performed in this article.

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