Development and evaluation of a sampling system to determine gaseous Mercury fluxes using an aerodynamic micrometeorological gradient method

Edwards, Grant C.; Rasmussen, Pat E.; Schroeder, W. H.; Wallace, Danielle; Halfpenny-Mitchell, L.; Dias, Goretty; Kemp, R. J.; Ausma, Sandra

doi:10.1029/2004jd005187

Cited by 57 publications

(62 citation statements)

References 30 publications

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“…GEM fluxes were determined using the method and assumptions outlined in Edwards et al (2005). Flux calculations were undertaken according to Eq.…”

Section: Flux Instrumentation and Methodsmentioning

confidence: 99%

“…Following the application of quality control protocols, GEM flux values were obtained for 87 % of the study period; 39 % of flux values fell below the theoretical detection limit (Eq. 8, Edwards et al, 2005). These were not removed as doing so would have resulted in an artificial increase of the observed mean (see also Fritsche et al, 2008a;Converse et al, 2010).…”

Section: Gem Fluxes 321 Quality Controlmentioning

confidence: 99%

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Mercury fluxes over an Australian alpine grassland and observation of nocturnal atmospheric mercury depletion events

Howard

Edwards

2018

Atmos. Chem. Phys.

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Abstract. Aerodynamic gradient measurements of the airsurface exchange of gaseous elemental mercury (GEM) were undertaken over a 40 ha alpine grassland in Australia's Snowy Mountains region across a 3-week period during the late austral summer. Bi-directional GEM fluxes were observed throughout the study, with overall mean value of 0.2 ± 14.5 ng m −2 h −1 and mean nocturnal fluxes of −1.5 ± 7.8 ng m −2 h −1 compared to diurnal fluxes of 1.8 ± 18.6 ng m −2 h −1 . Deposition velocities ranged from −2.2 to 2.9 cm s −1 , whilst ambient GEM concentrations throughout the study were 0.59 ± 0.10 ng m −3 . Cumulative GEM fluxes correlated well with 24 h running mean soil temperatures, and one precipitation event was shown to have a positive impact on diurnal emission fluxes. The underlying vegetation had largely senesced and showed little stomatal control on fluxes. Nocturnal atmospheric mercury depletion events (NAMDEs) were observed concomitant with O 3 depletion and dew formation under shallow, stable nocturnal boundary layers. A mass balance box model was able to reproduce ambient GEM concentration patterns during NAMDE and non-NAMDE nights without invoking chemical oxidation of GEM throughout the column, indicating a significant role of surface processes controlling deposition in these events. Surface deposition was enhanced under NAMDE nights, though uptake to dew likely represents less than one-fifth of this enhanced deposition. Instead, enhancement of the surface GEM gradient as a result of oxidation at the surface in the presence of dew is hypothesised to be responsible for a large portion of GEM depletion during these particular events. GEM emission pulses following nights with significant deposition provide evidence for the prompt recycling of 17 % of deposited mercury, with the remaining portion retained in surface sinks. The long-term impacts of any sinks are however likely to be minimal, as cumulative GEM flux across the study period was close to zero.

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“…GEM fluxes were determined using the method and assumptions outlined in Edwards et al (2005). Flux calculations were undertaken according to Eq.…”

Section: Flux Instrumentation and Methodsmentioning

confidence: 99%

Section: Gem Fluxes 321 Quality Controlmentioning

confidence: 99%

Mercury fluxes over an Australian alpine grassland and observation of nocturnal atmospheric mercury depletion events

Howard

Edwards

2018

Atmos. Chem. Phys.

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“…The level of the detection limit obtained in this study (0.064 ng m −3 ) compares favorably with the 0.072 ng m −3 reported by Converse et al (2010) using gradient-based MM techniques. Compared to other studies deriving Hg 0 gas exchange flux from concentration profile measurements (Edwards et al, 2005;Fritsche et al, 2008;Lee et al, 2000;Goodrow et al, 2005), our C grad. precision (1σ ) is contrastingly elevated, likely due to the generally higher level of ambient Hg 0 concentration in this study (Zhu et al, 2015).…”

Section: Turbulent Flux Measurements Under Varying Experimental Condimentioning

confidence: 99%

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

et al. 2015

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Abstract. Dynamic flux chambers (DFCs) and micrometeorological (MM) methods are extensively deployed for gauging air-surface Hg 0 gas exchange. However, a systematic evaluation of the precision of the contemporary Hg 0 flux quantification methods is not available. In this study, the uncertainty in Hg 0 flux measured by the relaxed eddy accumulation (REA) method, the aerodynamic gradient method (AGM), the modified Bowen ratio (MBR) method, as well as DFC of traditional (TDFC) and novel (NDFC) designs, are assessed using a robust data set from two field intercomparison campaigns.The absolute precision in Hg 0 concentration difference ( C) measurements is estimated at 0.064 ng m −3 for the gradient-based MBR and AGM systems. For the REA system, the parameter is Hg 0 concentration (C) dependent at 0.069 + 0.022C. During the campaigns, 57 and 62 % of the individual vertical gradient measurements are found to be significantly different from 0, while for the REA technique, the percentage of significant observations is lower. For the chambers, non-significant fluxes are confined to a few nighttime periods with varying ambient Hg 0 concentrations. Relative bias for DFC-derived fluxes is estimated to be ∼ ±10, and ∼ 85 % of the flux bias is within ±2 ng m −2 h −1 in absolute terms. The DFC flux bias follows a diurnal cycle, which is largely affected by the forced temperature and irradiation bias in the chambers. Due to contrasting prevailing micrometeorological conditions, the relative uncertainty (median) in turbulent exchange parameters differs by nearly a factor of 2 between the campaigns, while that in C measurement is fairly consistent. 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 methods, respectively. This study indicates that flux-gradient-based techniques (MBR and AGM) are preferable to REA in quantifying Hg 0 flux over ecosystems with low vegetation height. A limitation of all Hg 0 flux measurement systems investigated is their inability to obtain synchronous samples for the calculation of C. This reduces the precision of flux quantification, particularly in the MM systems under non-stationarity of ambient Hg 0 concentration. For future applications, it is recommended to accomplish C derivation from simultaneous collected samples.

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“…GEM fluxes were measured using the methods outlined in Edwards et al (2005). Air samples were drawn at heights of 5.2 and 8.0 m through 46.4 m of nylon tubing using a PTFE diaphragm pump operating at 10 L min −1 .…”

Section: Mercurymentioning

confidence: 99%

Biomass burning emissions in north Australia during the early dry season: an overview of the 2014 SAFIRED campaign

et al. 2017

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Abstract. The SAFIRED (Savannah Fires in the Early Dry Season) campaign took place from 29 May until 30 June 2014 at the Australian Tropical Atmospheric Research Station (ATARS) in the Northern Territory, Australia. The purpose of this campaign was to investigate emissions from fires in the early dry season in northern Australia. Measurements were made of biomass burning aerosols, volatile organic compounds, polycyclic aromatic carbons, greenhouse gases, radon, speciated atmospheric mercury and trace metals. Aspects of the biomass burning aerosol emissions investigated included; emission factors of various species, physical and chemical aerosol properties, aerosol aging, micronutrient supply to the ocean, nucleation, and aerosol water uptake. Over the course of the month-long campaign, biomass burning signals were prevalent and emissions from several large single burning events were observed at ATARS.Biomass burning emissions dominated the gas and aerosol concentrations in this region. Dry season fires are extremely frequent and widespread across the northern region of Australia, which suggests that the measured aerosol and gaseous emissions at ATARS are likely representative of signals across the entire region of north Australia. Air mass forward trajectories show that these biomass burning emissions are carried north-west over the Timor Sea and could influence the atmosphere over Indonesia and the tropical atmosphere over the Indian Ocean. Here we present characteristics of the biomass burning observed at the sampling site and provide an overview of the more specific outcomes of the SAFIRED campaign.

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Development and evaluation of a sampling system to determine gaseous Mercury fluxes using an aerodynamic micrometeorological gradient method

Cited by 57 publications

References 30 publications

Mercury fluxes over an Australian alpine grassland and observation of nocturnal atmospheric mercury depletion events

Mercury fluxes over an Australian alpine grassland and observation of nocturnal atmospheric mercury depletion events

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

Biomass burning emissions in north Australia during the early dry season: an overview of the 2014 SAFIRED campaign

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