Emission characteristics and air–surface exchange of gaseous mercury at the largest active landfill in Asia

Zhu, Wei; Li, Zhonggen; Chai, Xin‐Sheng; Hao, Yongxia; Lin, Che‐Jen; Sommar, Jonas; Feng, Xinbin

doi:10.1016/j.atmosenv.2013.05.083

Cited by 33 publications

(21 citation statements)

References 39 publications

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“…For the DFCs, the observed Hg 0 flux peaked within the period P2 (Fig. 10, IC#1) in concert with soil temperature, which is consistent with diurnal cycles reported for chamber measurements in the literature (Fu et al, 2008(Fu et al, , 2012Gustin, 2011;Zhu et al, 2013a). The smoothed mean diurnal cycle derived by the gradientbased methods over the same period exhibits peaking Hg 0 fluxes shortly before midday (P1 in Fig.…”

Section: Diel Variationssupporting

confidence: 74%

“…It has been shown that the air-surface exchange of Hg can be influenced by solar irradiation, temperature, humidity, moisture, wind shear condition, and biotic processes (Choi and Holsen, 2009;Eckley et al, 2010;Fu et al, 2008;Gustin, 2011;Zhu et al, 2013a;Lin et al, 2010), as also observed in our field (Figs. 9 and 10).…”

Section: Correlation Between Hg 0 Flux Observation and Environmental supporting

confidence: 59%

“…of 0.06 m 2 has been used extensively in our group and elsewhere Fu et al, 2008Fu et al, , 2010Fu et al, , 2012Li et al, 2010;Wang et al, 2005Wang et al, , 2007Zhu et al, 2013a). The NDFC was fabricated of thin polycarbonate sections and enclosed a soil surface of 0.09 m 2 (for details, see Lin et al, 2012).…”

Section: W Zhu Et Al: Mercury Flux Data Comparability and Methods Chmentioning

confidence: 99%

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Mercury vapor air–surface exchange measured by collocated micrometeorological and enclosure methods – Part I: Data comparability and method characteristics

et al. 2015

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Abstract. Reliable quantification of air-biosphere exchange flux of elemental mercury vapor (Hg 0 ) is crucial for understanding the global biogeochemical cycle of mercury. However, there has not been a standard analytical protocol for flux quantification, and little attention has been devoted to characterize the temporal variability and comparability of fluxes measured by different methods. In this study, we deployed a collocated set of micrometeorological (MM) and dynamic flux chamber (DFC) measurement systems to quantify Hg 0 flux over bare soil and low standing crop in an agricultural field. The techniques include relaxed eddy accumulation (REA), modified Bowen ratio (MBR), aerodynamic gradient (AGM) as well as dynamic flux chambers of traditional (TDFC) and novel (NDFC) designs. The five systems and their measured fluxes were cross-examined with respect to magnitude, temporal trend and correlation with environmental variables.Fluxes measured by the MM and DFC methods showed distinct temporal trends. The former exhibited a highly dynamic temporal variability while the latter had much more gradual temporal features. The diurnal characteristics reflected the difference in the fundamental processes driving the measurements. The correlations between NDFC and TDFC fluxes and between MBR and AGM fluxes were significant (R>0.8, p<0.05), but the correlation between DFC and MM fluxes were from weak to moderate (R = 0.1-0.5). Statistical analysis indicated that the median of turbulent fluxes estimated by the three independent MM techniques were not significantly different. Cumulative flux measured by TDFC is considerably lower (42 % of AGM and 31 % of MBR fluxes) while those measured by NDFC, AGM and MBR were similar (<10 % difference). This suggests that incorporating an atmospheric turbulence property such as friction velocity for correcting the DFC-measured flux effectively bridged the gap between the Hg 0 fluxes measured by enclosure and MM techniques. Cumulated flux measured by REA was ∼ 60 % higher than the gradient-based fluxes. Environmental factors have different degrees of impacts on the fluxes observed by different techniques, possibly caused by the underlying assumptions specific to each individual method. Recommendations regarding the application of flux quantification methods were made based on the data obtained in this study.

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Section: Diel Variationssupporting

confidence: 74%

Section: Correlation Between Hg 0 Flux Observation and Environmental supporting

confidence: 59%

Section: W Zhu Et Al: Mercury Flux Data Comparability and Methods Chmentioning

confidence: 99%

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Mercury vapor air–surface exchange measured by collocated micrometeorological and enclosure methods – Part I: Data comparability and method characteristics

et al. 2015

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“…Possible reasons for the data disparity include (1) the difference in the light transmission properties of the two chamber materials, and (2) the difference in soil temperature inside the chamber. The TDFC was manufactured from quartz glass, while the NDFC was assembled from polycarbonate (PC) sheets (Lin et al, 2012;Zhu et al, 2013bZhu et al, , 2015. Quartz has exceptional transmission properties for UV light down to 250 nm, while PC does not allow transmission of UV light that plays an important role in promoting Hg II photo-reduction in the substrate Lin et al, 2012).…”

Section: Bias and Uncertainty In Dfc-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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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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“…Up until now in China, solely flowthrough dynamic flux chambers (DFCs) covering a small plot of 50.1 m 2 have been employed for such studies (e.g. Feng et al, 2004Feng et al, , 2005Wang et al, 2005Wang et al, , 2006Wang et al, , 2007aWang et al, , 2007bFu et al, 2008Fu et al, , 2012aFu et al, , 2012bZhu et al, 2011;Zhu et al, 2013). Enclosure methods are of relatively low cost, easy to operate and straightforward.…”

Section: Introductionmentioning

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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Emission characteristics and air–surface exchange of gaseous mercury at the largest active landfill in Asia

Cited by 33 publications

References 39 publications

Mercury vapor air–surface exchange measured by collocated micrometeorological and enclosure methods – Part I: Data comparability and method characteristics

Mercury vapor air–surface exchange measured by collocated micrometeorological and enclosure methods – Part I: Data comparability and method characteristics

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

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

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