Uncertainty in ammonia flux measurement systems

2004 ◽  
Author(s):  
Cale N Boriack ◽  
S.C. Capareda ◽  
R.E. Lacey ◽  
A Mutlu ◽  
S Mukhtar ◽  
...  
Keyword(s):  
Flux Measurement ◽  
Measurement Systems ◽  
Ammonia Flux

scholarly journals Measurements of ambient HONO concentrations and vertical HONO flux above a northern Michigan forest canopy

2012 ◽  
Vol 12 (17) ◽  
pp. 8285-8296 ◽  
Author(s):  
N. Zhang ◽  
X. Zhou ◽  
S. Bertman ◽  
D. Tang ◽  
M. Alaghmand ◽  
...  
Keyword(s):  
Measurement Technique ◽  
Forest Canopy ◽  
Sonic Anemometer ◽  
Flux Measurement ◽  
Measurement Systems ◽  
Ambient Concentration ◽  
Solar Noon ◽  
Absorption Photometer ◽  
Upward Flux ◽  
Northern Michigan

Abstract. Systems have been developed and deployed at a North Michigan forested site to measure ambient HONO and vertical HONO flux. The modified HONO measurement technique is based on aqueous scrubbing of HONO using a coil sampler, followed by azo dye derivatization and detection using a long-path absorption photometer (LPAP). A Na2CO3-coated denuder is used to generate "zero HONO" air for background correction. The lower detection limit of the method, defined by 3 times of the standard deviation of the signal, is 1 pptv for 1-min averages, with an overall uncertainty of ±(1 + 0.05 [HONO]) pptv. The HONO flux measurement technique has been developed based on the relaxed eddy accumulation approach, deploying a 3-D sonic anemometer and two HONO measurement systems. The overall uncertainty is estimated to be within ±(8 × 10−8 + 0.15 FHONO) mol m−2 h−1, with a 20-min averaged data point per 30 min. Ambient HONO and vertical HONO flux were measured simultaneously at the PROPHET site from 17 July to 7 August 2008. The forest canopy was found to be a net HONO source, with a mean upward flux of 0.37 × 10−6 moles m−2 h−1. The HONO flux reached a maximal mean of ~0.7 × 10−6 moles m−2 h−1 around solar noon, contributing a major fraction to the HONO source strength required to sustain the observed ambient concentration of ~70 pptv. There were no significant correlations between [NOx] and daytime HONO flux and between JNO2 × [NO2] and HONO flux, suggesting that NOx was not an important precursor responsible for HONO daytime production on the forest canopy surface in this low-NOx rural environment. Evidence supports the hypothesis that photolysis of HNO3 deposited on the forest canopy surface is a major daytime HONO source.

scholarly journals Measurements of ambient HONO concentrations and vertical HONO flux above a northern Michigan forest canopy

2012 ◽  
Vol 12 (3) ◽  
pp. 7273-7304 ◽  
Author(s):  
N. Zhang ◽  
X. Zhou ◽  
S. Bertman ◽  
D. Tang ◽  
M. Alaghmand ◽  
...  
Keyword(s):  
Measurement Technique ◽  
Forest Canopy ◽  
Sonic Anemometer ◽  
Flux Measurement ◽  
Rural Environment ◽  
Measurement Systems ◽  
Ambient Concentration ◽  
Solar Noon ◽  
Upward Flux ◽  
Northern Michigan

Abstract. Systems have been developed and deployed at a North Michigan forested site to measure ambient HONO and vertical HONO flux. The modified HONO measurement technique is based on aqueous scrubbing of HONO using a coil sampler, followed by azo dye derivatization and detection using an optical fiber spectrometer with a 1-m long path flow cell. A Na2CO3-coated denuder is used to generate "zero HONO" air for background correction. The lower detection limit of the method, defined by 3 times of the standard deviation of the signal, is 1 pptv for 2-min averages, with an overall uncertainty of ±(1 + 0.05 [HONO]) pptv. The HONO flux measurement technique has been developed based on the relaxed eddy accumulation approach, deploying a 3-D sonic anemometer and two HONO measurement systems. The overall uncertainty is estimated to be within ±(8 × 10−8 + 0.15 FHONO) mol m−2 h−1, with a 20-min averaged data point per 30 min. Ambient HONO and vertical HONO flux were measured simultaneously at the PROPHET site from 17 July to 7 August 2008. The forest canopy was found to be a net HONO source, with a mean upward flux of 0.37 × 10−6 moles m−2 h−1. The HONO flux reached a maximum mean of ~0.7 × 10−6 moles m−2 h−1 around solar noon, contributing a major fraction (~60%) to the HONO source strength required to sustain the observed ambient concentration of ~70 pptv. There was no significant correlation between NOx and daytime HONO flux, suggesting that NOx was not an important precursor responsible for HONO daytime production on the forest canopy surface in the low-NOx rural environment. Evidence suggests that photolysis of HNO3 deposited on the forest canopy surface is a major daytime HONO source.

Comparisons of surface flux measurement systems used in FIFE 1989

1992 ◽  
Vol 97 (D17) ◽  
pp. 18697 ◽  
Author(s):  
L. J. Fritschen ◽  
P. Qian ◽  
E. T. Kanemasu ◽  
D. Nie ◽  
E. A. Smith ◽  
...  
Keyword(s):  
Flux Measurement ◽  
Surface Flux ◽  
Measurement Systems

scholarly journals An intercomparison of surface energy flux measurement systems used during FIFE 1987

1992 ◽  
Vol 97 (D17) ◽  
pp. 18715 ◽  
Author(s):  
D. Nie ◽  
E. T. Kanemasu ◽  
L. J. Fritschen ◽  
H. L. Weaver ◽  
E. A. Smith ◽  
...  
Keyword(s):  
Surface Energy ◽  
Energy Flux ◽  
Flux Measurement ◽  
Measurement Systems ◽  
Surface Energy Flux

Intercomparison of surface energy flux measurement systems used during the HiWATER-MUSOEXE

2013 ◽  
Vol 118 (23) ◽  
pp. 13,140-13,157 ◽  
Author(s):  
Ziwei Xu ◽  
Shaomin Liu ◽  
Xin Li ◽  
Shengjin Shi ◽  
Jiemin Wang ◽  
...  
Keyword(s):  
Surface Energy ◽  
Energy Flux ◽  
Flux Measurement ◽  
Measurement Systems ◽  
Surface Energy Flux

Food Safety Security: A new Concept for Enhancing Food Safety Measures

2012 ◽  
Vol 82 (3) ◽  
pp. 216-222 ◽  
Author(s):  
Venkatesh Iyengar ◽  
Ibrahim Elmadfa
Keyword(s):  
Food Safety ◽  
Hazard Analysis ◽  
Warning System ◽  
Shared Responsibility ◽  
Fine Tuning ◽  
Strategic Action ◽  
Surveillance Network ◽  
Measurement Systems ◽  
Critical Control Points ◽  
The Impact

The food safety security (FSS) concept is perceived as an early warning system for minimizing food safety (FS) breaches, and it functions in conjunction with existing FS measures. Essentially, the function of FS and FSS measures can be visualized in two parts: (i) the FS preventive measures as actions taken at the stem level, and (ii) the FSS interventions as actions taken at the root level, to enhance the impact of the implemented safety steps. In practice, along with FS, FSS also draws its support from (i) legislative directives and regulatory measures for enforcing verifiable, timely, and effective compliance; (ii) measurement systems in place for sustained quality assurance; and (iii) shared responsibility to ensure cohesion among all the stakeholders namely, policy makers, regulators, food producers, processors and distributors, and consumers. However, the functional framework of FSS differs from that of FS by way of: (i) retooling the vulnerable segments of the preventive features of existing FS measures; (ii) fine-tuning response systems to efficiently preempt the FS breaches; (iii) building a long-term nutrient and toxicant surveillance network based on validated measurement systems functioning in real time; (iv) focusing on crisp, clear, and correct communication that resonates among all the stakeholders; and (v) developing inter-disciplinary human resources to meet ever-increasing FS challenges. Important determinants of FSS include: (i) strengthening international dialogue for refining regulatory reforms and addressing emerging risks; (ii) developing innovative and strategic action points for intervention {in addition to Hazard Analysis and Critical Control Points (HACCP) procedures]; and (iii) introducing additional science-based tools such as metrology-based measurement systems.

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