Application of Relaxed Eddy Accumulation Technique to Quantify Hg0 Fluxes Over Modified Soil Surfaces

Olofsson, Marcus; Sommar, Jonas; Ljungström, Evert; Andersson, Maria; Wängberg, Ingvar

doi:10.1007/s11270-005-0012-8

Cited by 24 publications

(28 citation statements)

References 44 publications

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“…precision (1σ ) is contrastingly elevated, likely due to the generally higher level of ambient Hg 0 concentration in this study (Zhu et al, 2015). The limited information existing in the literature regarding measurement of Hg 0 flux by the REA technique (Bash and Miller, 2008;Cobos et al, 2002;Bash and Miller, 2009;Olofsson et al, 2005) excludes a rudimentary analysis and discussion of uncertainty and bias associated with conditionally sampled concentration differences. Table 1 summarizes the uncertainty in MM and DFC flux methods in our inter-comparison.…”

Section: Turbulent Flux Measurements Under Varying Experimental Condimentioning

confidence: 77%

“…Hence, there exists a moderate bias between the channels, which is corrected in Table 1. Such regular performance tests are very infrequently reported in the REA literature (Arnts et al, 2013;Hensen et al, 2009;Park et al, 2010;Schade and Goldstein, 2001). Significant and variable REA channel biases were occasionally detected (Nemitz et al, 2001;Schade and Goldstein, 2001).…”

Section: Bias and Uncertainty In Rea-derived Hg 0 Fluxesmentioning

confidence: 99%

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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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Section: Turbulent Flux Measurements Under Varying Experimental Condimentioning

confidence: 77%

Section: Bias and Uncertainty In Rea-derived Hg 0 Fluxesmentioning

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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“…Here we focus on the developments, advantages and disadvantages and comparability and uncertainties of different flux quantification techniques. DFCs, micrometeorological techniques (MM) and bulk methods (e.g., the Hg 0 / 222 Rn flux ratio, enriched isotope tracers) are the mostly widely applied approaches for surface-atmosphere Hg 0 flux quantification (Schroeder et al, 1989;Xiao et al, 1991;Cobos et al, 2002;Amyot et al, 2004;Olofsson et al, 2005;Obrist et al, 2006;Bash and Miller, 2008;Lin et al, 2012;Slemr et al, 2013;Zhu et al, 2013c), of which DFCs and MM techniques account for > 95 % of all observations documented to date (cf. Sect.…”

Section: Advances In Hg 0 Flux Quantification Methodsmentioning

confidence: 99%

“…The REA method has been deployed for flux measurements for agricultural lands, forest canopies, wetlands and urban settings (Cobos et al, 2002;Olofsson et al, 2005;Bash and Miller, 2009;Osterwalder et al, 2016;Sommar et al, 2013b). The AGM method has been used over grasslands, agricultural lands, salt marshes, landfills and snow (Lee et al, 2000;Kim et al, , 2003Fritsche et al, 2008b, c;Baya and Van Heyst, 2010).…”

Section: Micrometeorological Methodsmentioning

confidence: 99%

Global observations and modeling of atmosphere–surface exchange of elemental mercury: a critical review

et al. 2016

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Abstract. Reliable quantification of air-surface fluxes of elemental Hg vapor (Hg 0 ) is crucial for understanding mercury (Hg) global biogeochemical cycles. There have been extensive measurements and modeling efforts devoted to estimating the exchange fluxes between the atmosphere and various surfaces (e.g., soil, canopies, water, snow, etc.) in the past three decades. However, large uncertainties remain due to the complexity of Hg 0 bidirectional exchange, limitations of flux quantification techniques and challenges in model parameterization. In this study, we provide a critical review on the state of science in the atmosphere-surface exchange of Hg 0 . Specifically, the advancement of flux quantification techniques, mechanisms in driving the air-surface Hg exchange and modeling efforts are presented. Due to the semi-volatile nature of Hg 0 and redox transformation of Hg in environmental media, Hg deposition and evasion are influenced by multiple environmental variables including seasonality, vegetative coverage and its life cycle, temperature, light, moisture, atmospheric turbulence and the presence of reactants (e.g., O 3 , radicals, etc.). However, the effects of these processes on flux have not been fundamentally and quantitatively determined, which limits the accuracy of flux modeling.We compile an up-to-date global observational flux database and discuss the implication of flux data on the global Hg budget. Mean Hg 0 fluxes obtained by micrometeorological measurements do not appear to be significantly greater than the fluxes measured by dynamic flux chamber methods over unpolluted surfaces (p = 0.16, one-tailed, Mann-Whitney U test). The spatiotemporal coverage of existing Hg 0 flux measurements is highly heterogeneous with large data gaps existing in multiple continents (Africa, South Asia, Middle East, South America and Australia). The magnitude of the evasion flux is strongly enhanced by human activities, particularly at contaminated sites. Hg 0 flux observations in East Asia are comparatively larger in magnitude than the rest of the world, suggesting substantial re-emission of previously deposited mercury from anthropogenic sources. The Hg 0 exchange over pristine surfaces (e.g., background soil and water) and vegetation needs better constraints for global analyses of the atmospheric Hg budget. The existing knowledge gap and the associated research needs for future measurements and modeling efforts for the air-surface exchange of Hg 0 are discussed.

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“…In REA, the vertical flux of target analyte (F REA Hg 0 ) is calculated over a suitable averaging time using: , 13 CO 2 (Bowling et al, 2003;Ruppert, 2008), CH 4 and N 2 O (Beverland et al, 1996), NH 3 (Zhu et al, 2000;Sutton et al, 2001), O 3 (Katul et al, 1996;Ammann, 1998), HNO 3 (Pryor et al, 2002), HONO (Ren et al, 2011), various classes of biogenic and anthropogenic volatile organic compounds (Guenther et al, 1996;Valentini et al, 1997;Christensen et al, 2000;Goldstein and Schade, 2000;Olofsson et al, 2003;Hornsby et al, 2009;Park et al, 2010), COS and CS 2 (Xu et al, 2002), (CH 3 ) 2 S (Zemmelink et al, 2002). REA technique has also been applied to measure fluxes of size-segregated aerosols (Schery et al, 1998;Gaman et al, 2004) and sulphate in particulates , chemically reactive compounds such as H 2 O 2 and organic peroxides (Valverde-Canossa et al, 2006) and toxic trace substances, such as pesticides (Majewski et al, 1993;Pattey et al, 1995;Zhu et al, 1998;Leistra et al, 2006) and mercury (Hg 0 , Cobos et al, 2002;Olofsson et al, 2005;Bash and Miller, 2008) and (GOM, Skov et al, 2006).…”

Section: Hgmentioning

confidence: 99%

A whole-air relaxed eddy accumulation measurement system for sampling vertical vapour exchange of elemental mercury

Sommar

Zhu

Shang

et al. 2013

Tellus B: Chemical and Physical Meteorology

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Application of Relaxed Eddy Accumulation Technique to Quantify Hg0 Fluxes Over Modified Soil Surfaces

Cited by 24 publications

References 44 publications

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

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

Global observations and modeling of atmosphere–surface exchange of elemental mercury: a critical review

A whole-air relaxed eddy accumulation measurement system for sampling vertical vapour exchange of elemental mercury

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