scholarly journals Global evaluation and calibration of a passive air sampler for gaseous mercury

2018 ◽  
Author(s):  
David S. McLagan ◽  
Carl P. J. Mitchell ◽  
Alexandra Steffen ◽  
Hayley Hung ◽  
Cecilia Shin ◽  
...  
Keyword(s):  
Sampling Rate ◽  
Ease Of Use ◽  
Global Evaluation ◽  
Data Set ◽  
Wind Speeds ◽  
Industry Standard ◽  
Gaseous Mercury ◽  
Wide Range ◽  
The Difference ◽  
Very High

Abstract. Passive air samplers (PASs) for gaseous mercury (Hg) were deployed for time periods between 1 month and 1 year at 20 sites across the globe with continuous atmospheric Hg monitoring using active Tekran instruments. The purpose was to evaluate the accuracy of the PAS vis-à-vis the industry standard active instruments and to determine a sampling rate (SR; the volume of air stripped of gaseous Hg per unit of time) that is applicable across a broad variety of conditions. The sites spanned a wide range of latitudes, altitudes, meteorological conditions, and gaseous Hg concentrations. Precision, based on 378 replicated deployments performed by numerous personnel at multiple sites, is 3.6 ± 3.0 %*, confirming the PAS's excellent reproducibility and ease-of-use. Using a SR previously determined at a single site, gaseous Hg concentrations derived from the globally distributed PASs deviate from Tekran-based concentrations by 14.2 ± 10 %. A recalibration using the entire new data set yields a slightly higher SR of 0.1354 ± 0.016 m3 day−1. When concentrations are derived from the PAS using this revised SR the difference is reduced to 8.8 ± 7.5 %. At the mean gaseous Hg concentration across the study sites of 1.54 ng m−3, this represents an ability to resolve concentrations to within 0.13 ng m−3. Adjusting the sampling rate to deployment specific temperatures and wind speeds does not decrease the difference in active–passive concentration further (8.7 ± 5.7 %), but reduces its variability by leading to better agreement in Hg concentrations measured at sites with very high and very low temperatures and very high wind speeds. This value (8.7 ± 5.7 %) represents a conservative assessment of the overall uncertainty of the PAS due to inherent uncertainties of the Tekran instruments. Going forward, the recalibrated SR adjusted for temperature and wind speed should be used, especially if conditions are highly variable or deviate considerably from the average of the deployments in this study (9.89 °C, 3.41 m s−1). Overall, the study demonstrates that the sampler is capable of recording background gaseous Hg concentrations across a wide range of environmental conditions with accuracy similar to that of industry standard active sampling instruments. Results at sites with active speciation units were inconclusive on whether the PASs take up total gaseous Hg or solely gaseous elemental Hg primarily because gaseous oxidized Hg concentrations were in a similar range as the uncertainty of the PAS.

scholarly journals Global evaluation and calibration of a passive air sampler for gaseous mercury

2018 ◽  
Vol 18 (8) ◽  
pp. 5905-5919 ◽  
Author(s):  
David S. McLagan ◽  
Carl P. J. Mitchell ◽  
Alexandra Steffen ◽  
Hayley Hung ◽  
Cecilia Shin ◽  
...  
Keyword(s):  
Sampling Rate ◽  
Ease Of Use ◽  
Global Evaluation ◽  
Data Set ◽  
Wind Speeds ◽  
Industry Standard ◽  
Gaseous Mercury ◽  
Wide Range ◽  
The Difference ◽  
Very High

Abstract. Passive air samplers (PASs) for gaseous mercury (Hg) were deployed for time periods between 1 month and 1 year at 20 sites across the globe with continuous atmospheric Hg monitoring using active Tekran instruments. The purpose was to evaluate the accuracy of the PAS vis-à-vis the industry standard active instruments and to determine a sampling rate (SR; the volume of air stripped of gaseous Hg per unit of time) that is applicable across a wide range of conditions. The sites spanned a wide range of latitudes, altitudes, meteorological conditions, and gaseous Hg concentrations. Precision, based on 378 replicated deployments performed by numerous personnel at multiple sites, is 3.6 ± 3.0 %1, confirming the PAS's excellent reproducibility and ease of use. Using a SR previously determined at a single site, gaseous Hg concentrations derived from the globally distributed PASs deviate from Tekran-based concentrations by 14.2 ± 10 %. A recalibration using the entire new data set yields a slightly higher SR of 0.1354 ± 0.016 m3 day−1. When concentrations are derived from the PAS using this revised SR the difference between concentrations from active and passive sampling is reduced to 8.8 ± 7.5 %. At the mean gaseous Hg concentration across the study sites of 1.54 ng m−3, this represents an ability to resolve concentrations to within 0.13 ng m−3. Adjusting the sampling rate to deployment specific temperatures and wind speeds does not decrease the difference in active–passive concentration further (8.7 ± 5.7 %), but reduces its variability by leading to better agreement in Hg concentrations measured at sites with very high and very low temperatures and very high wind speeds. This value (8.7 ± 5.7 %) represents a conservative assessment of the overall uncertainty of the PAS due to inherent uncertainties of the Tekran instruments. Going forward, the recalibrated SR adjusted for temperature and wind speed should be used, especially if conditions are highly variable or deviate considerably from the average of the deployments in this study (9.89 ∘C, 3.41 m s−1). Overall, the study demonstrates that the sampler is capable of recording background gaseous Hg concentrations across a wide range of environmental conditions with accuracy similar to that of industry standard active sampling instruments. Results at sites with active speciation units were inconclusive on whether the PASs take up total gaseous Hg or solely gaseous elemental Hg primarily because gaseous oxidized Hg concentrations were in a similar range as the uncertainty of the PAS.

scholarly journals The effects of meteorological parameters and diffusive barrier reuse on the sampling rate of a passive air sampler for gaseous mercury

2017 ◽  
Author(s):  
David S. McLagan ◽  
Carl P. J. Mitchell ◽  
Haiyong Huang ◽  
Batual Abdul Hussain ◽  
Ying Duan Lei ◽  
...  
Keyword(s):  
Wind Speed ◽  
Meteorological Parameters ◽  
Sampling Rate ◽  
Effect Of Temperature ◽  
Wind Speeds ◽  
Passive Air Sampler ◽  
Molecular Diffusivity ◽  
Air Sampler ◽  
Gaseous Mercury ◽  
High Level

Abstract. Passive air sampling of gaseous mercury (Hg) requires a high level of accuracy to discriminate small differences in atmospheric concentrations. Meteorological parameters have the potential to decrease this accuracy by impacting the sampling rate (SR), i.e., the volume of air that is effectively stripped of gaseous mercury per unit of time. We measured the SR of a recently calibrated passive air sampler for gaseous Hg in the laboratory under varying wind speeds (wind-still – 6 m s−1), temperatures (−15–35 °C), and relative humidities (44–80 %). While relative humidity has no impact on SR, SR increases slightly with both wind speed (0.003 m3 day−1 increase in SR or 2.5 % of the previously calibrated SR for every m s−1 increase for wind speeds > 1 m s−1, typical of outdoor deployments) and temperature (0.001 m3 day−1 increase in SR or 0.7 % for every 1 °C increase). The temperature dependence can be fully explained by the effect of temperature on the molecular diffusivity of gaseous mercury in air. Although these effects are relatively small, accuracy can be improved by adjusting SRs using measured or estimated temperature and wind speed data at or near sampling sites. We also assessed the possibility of reusing Radiello® diffusive barriers previously used in the passive air samplers. The mean rate of gaseous Hg uptake was not significantly different between new and previously used diffusive barriers in both lab and outdoor deployments, irrespective of the applied cleaning procedure. No memory effect from Radiellos® previously deployed in a high Hg atmosphere was observed. However, a loss in replicate precision for the dirtiest Radiellos® in the indoor experiment suggests that cleaning is advisable prior to reuse.

scholarly journals A global historical data set of tropical cyclone exposure (TCE-DAT)

2017 ◽  
Author(s):  
Tobias Geiger ◽  
Katja Frieler ◽  
David N. Bresch
Keyword(s):  
Tropical Cyclone ◽  
Tropical Cyclones ◽  
The United States ◽  
Long Term Effects ◽  
Wind Fields ◽  
Damage Functions ◽  
Data Set ◽  
Wind Field Model ◽  
Wind Speeds ◽  
The Difference

Abstract. Tropical cyclones pose a major risk to societies worldwide with about 22 million directly-affected people and damages of $29 billion on average per year over the last 20 years. While data on observed cyclones tracks (location of the center) and wind speeds is publically available these data sets do not contain information about the spatial extent of the storm and people or assets exposed. Here, we apply a simplified wind field model to estimate the areas exposed to wind speeds above 34, 64, and 96 knots. Based on available spatially-explicit data on population densities and Gross Domestic Product (GDP) we estimate 1) the number of people and 2) the sum of assets exposed to wind speeds above these thresholds accounting for temporal changes in historical distribution of population and assets (TCE-hist) and assuming fixed 2015 patterns (TCE-2015). The associated country-event level exposure data (TCE-DAT) covers the period 1950 to 2015 and is freely available at http://doi.org/10.5880/pik.2017.005. It is considered key information to 1) assess the contribution of climatological versus socio-economic drivers of changes in exposure to tropical cyclones, 2) estimate changes in vulnerability from the difference in exposure and reported damages and calibrate associated damage functions, and 3) build improved exposure-based predictors to estimate higher-level societal impacts such as long-term effects on GDP, employment, or migration. We validate the adequateness of our methodology by comparing our exposure estimate to estimated exposure obtained from reported wind fields available since 1988 for the United States. We expect that the free availability of the underlying model and TCE-DAT will make research on tropical cyclone risks more accessible to non-experts and stakeholders.

scholarly journals Year-to-year correlation, record length, and overconfidence in wind resource assessment

2016 ◽  
Vol 1 (2) ◽  
pp. 115-128 ◽  
Author(s):  
Nicola Bodini ◽  
Julie K. Lundquist ◽  
Dino Zardi ◽  
Mark Handschy
Keyword(s):  
Interannual Variability ◽  
Resource Assessment ◽  
Energy Estimates ◽  
Data Set ◽  
Wind Speeds ◽  
Wind Resource Assessment ◽  
Wide Range ◽  
Serial Correlations ◽  
Resource Levels ◽  
Wind Resource

Abstract. Interannual variability of wind speeds presents a fundamental source of uncertainty in preconstruction energy estimates. Our analysis of one of the longest and geographically most widespread extant sets of instrumental wind-speed observations (62-year records from 60 stations in Canada) shows that deviations from mean resource levels persist over many decades, substantially increasing uncertainty. As a result of this persistence, the performance of each site's last 20 years diverges more widely than expected from the P50 level estimated from its first 42 years: half the sites have either fewer than 5 or more than 15 years exceeding the P50 estimate. In contrast to this 10-year-wide interquartile range, a 4-year-wide range (2.5 times narrower) was found for "control" records where statistical independence was enforced by randomly permuting each station's historical values. Similarly, for sites with capacity factor of 0.35 and interannual variability of 6  %, one would expect 9 years in 10 to fall in the range 0.32–0.38; we find the actual 90  % range to be 0.27–0.43, or three times wider. The previously un-quantified effect of serial correlations favors a shift in resource-assessment thinking from a climatology-focused approach to a persistence-focused approach: for this data set, no improvement in P50 error is gained by using records longer than 4–5 years, and use of records longer than 20 years actually degrades accuracy.

scholarly journals Estimation of bubble-mediated air–sea gas exchange from concurrent DMS and CO<sub>2</sub> transfer velocities at intermediate–high wind speeds

2017 ◽  
Vol 17 (14) ◽  
pp. 9019-9033 ◽  
Author(s):  
Thomas G. Bell ◽  
Sebastian Landwehr ◽  
Scott D. Miller ◽  
Warren J. de Bruyn ◽  
Adrian H. Callaghan ◽  
...  
Keyword(s):  
Wind Speed ◽  
Gas Exchange ◽  
North Atlantic ◽  
Gas Transfer ◽  
Data Set ◽  
Wind Speeds ◽  
Wide Range ◽  
Carbon Dioxide Co2 ◽  
The Impact

Abstract. Simultaneous air–sea fluxes and concentration differences of dimethylsulfide (DMS) and carbon dioxide (CO2) were measured during a summertime North Atlantic cruise in 2011. This data set reveals significant differences between the gas transfer velocities of these two gases (Δkw) over a range of wind speeds up to 21 m s−1. These differences occur at and above the approximate wind speed threshold when waves begin breaking. Whitecap fraction (a proxy for bubbles) was also measured and has a positive relationship with Δkw, consistent with enhanced bubble-mediated transfer of the less soluble CO2 relative to that of the more soluble DMS. However, the correlation of Δkw with whitecap fraction is no stronger than with wind speed. Models used to estimate bubble-mediated transfer from in situ whitecap fraction underpredict the observations, particularly at intermediate wind speeds. Examining the differences between gas transfer velocities of gases with different solubilities is a useful way to detect the impact of bubble-mediated exchange. More simultaneous gas transfer measurements of different solubility gases across a wide range of oceanic conditions are needed to understand the factors controlling the magnitude and scaling of bubble-mediated gas exchange.

Decomposition Analyses for COD Discharges in China’s Industrial Sub-Sectors: Which is the Superior Method?

2012 ◽  
Vol 518-523 ◽  
pp. 168-177 ◽  
Author(s):  
Xun Feng Xia ◽  
Hong Jun Lei ◽  
Chang Jia Li ◽  
Bei Dou Xi
Keyword(s):  
Industrial Wastewater ◽  
Decomposition Analysis ◽  
Oxygen Demand ◽  
Structural Effect ◽  
Ease Of Use ◽  
Data Set ◽  
Total Contribution ◽  
Intensity Effect ◽  
Production Effect ◽  
Wide Range

Numerous index decomposition analysis approaches have been reported in the past 30 years. However, the selection of different methods appears to be arbitrary, and little consensus has been reached on which is the superior method. Between 2001 and 2009, 10 different methods have been used to identify the factors (i.e. production effect, structural effect and intensity effect) influencing on China’s industrial wastewater pollutant (Chemical Oxygen Demand, COD) discharges. From the aspect of theoretical foundation, adaptability, ease of use, and ease of result interpretation, these methods are compared. Results show that: (1) LMDI 1 is a superior approach because of zero residual error in decomposition, no zero values problem in data set, simplicity in formula, and wide range in usage situations. (2) the average effect changes of industrial wastewater changes of COD discharges in China is 14.89 ×104 t with production effect, structural effect, and intensity effect were 72.97×104 t, -6.93×104 t and -80.94×104 t, respectively. (3) production effect was the major factor responsible for the rise of COD discharges, accounting for 45% of the total contribution. (4) structural effect contributed to the decrease of COD discharges with a small effect of 4% in total contribution. (5) intensity effect had an dominant decremental effect in COD discharges.

scholarly journals Cattle stratified on genetic merit segregate on carcass characteristics, but there is scope for improvement1

2019 ◽  
Vol 3 (2) ◽  
pp. 893-902 ◽  
Author(s):  
Donagh P Berry ◽  
Thierry Pabiou ◽  
Denis Brennan ◽  
Patrick J Hegarthy ◽  
Michelle M Judge
Keyword(s):  
Carcass Weight ◽  
Data Set ◽  
Study Objective ◽  
Positive Weight ◽  
Association Analyses ◽  
Genetic Merit ◽  
The Difference ◽  
Fat Score ◽  
Using Data ◽  
Very High

Abstract The study objective was to quantify the ability of genetic merit for a generated carcass index to differentiate animals on primal carcass cut weights using data from 1,446 herds on 9,414 heifers and 22,413 steers with weights for 14 different primal carcass cuts (plus 3 generated groups of cuts). The carcass genetic merit index was compromised of carcass weight (positive weight), conformation (positive weight), and fat score (negative weight), each equally weighted within the index. The association analyses were undertaken using linear mixed models; models were run with or without carcass weight as a covariate. In a further series of analyses, carcass weight and carcass fat score were both included as covariates in the models. Whether the association between primal cut yield and carcass weight differed by genetic merit stratum was also investigated. Genetic merit was associated (P &lt; 0.001) with the weight of all cuts evaluated even when adjusted to a common carcass weight (P &lt; 0.01); when simultaneously adjusted to a common carcass weight and fat score, genetic merit was not associated with the weight of the cuberoll or the group cuts termed minced-meat. The weight of the different primal cuts increased almost linearly within increasing genetic merit, with the exception of the rump and bavette. The difference in mean primal cut weight between the very low and very high genetic merit strata, as a proportion of the overall mean weight of that cut in the entire data set, varied from 0.05 (bavette) to 0.28 (eye of round); the average was 0.17. Following adjustment for differences in carcass weight, there was no difference in cut weight between the very low and very high strata for the rump, chuck tender, and mince cut group; the remaining cuts were heavier in the higher index animals with the exception of the cuberoll and bavette, which were lighter in the very high index animals. The association between carcass weight and the weight of each of the evaluated primal cuts differed (P &lt; 0.05) by genetic merit stratum for all cuts evaluated with the exception of the rump, striploin, and brisket as well as the group cuts of frying and mincing. With the exception of these 5 primal (group) cuts, the regression coefficients of primal cut weight on carcass weight increased consistently for all traits with increasing genetic merit stratum, other than for the fillet, cuberoll, bavette, chuck and neck, and heel and shank.

scholarly journals The effects of meteorological parameters and diffusive barrier reuse on the sampling rate of a passive air sampler for gaseous mercury

2017 ◽  
Vol 10 (10) ◽  
pp. 3651-3660 ◽  
Author(s):  
David S. McLagan ◽  
Carl P. J. Mitchell ◽  
Haiyong Huang ◽  
Batual Abdul Hussain ◽  
Ying Duan Lei ◽  
...  
Keyword(s):  
Wind Speed ◽  
Meteorological Parameters ◽  
Sampling Rate ◽  
Effect Of Temperature ◽  
Wind Speeds ◽  
Passive Air Sampler ◽  
Molecular Diffusivity ◽  
Air Sampler ◽  
Gaseous Mercury ◽  
High Level

Abstract. Passive air sampling of gaseous mercury (Hg) requires a high level of accuracy to discriminate small differences in atmospheric concentrations. Meteorological parameters have the potential to decrease this accuracy by impacting the sampling rate (SR), i.e., the volume of air that is effectively stripped of gaseous mercury per unit of time. We measured the SR of a recently calibrated passive air sampler for gaseous Hg in the laboratory under varying wind speeds (wind still to 6 m s−1), temperatures (−15 to +35 °C), and relative humidities (44 to 80 %). While relative humidity has no impact on SR, SR increases slightly with both wind speed (0.003 m3 day−1 increase in SR or 2.5 % of the previously calibrated SR for every m s−1 increase for wind speeds  > 1 m s−1, typical of outdoor deployments) and temperature (0.001 m3 day−1 increase in SR or 0.7 % for every 1 °C increase). The temperature dependence can be fully explained by the effect of temperature on the molecular diffusivity of gaseous mercury in air. Although these effects are relatively small, accuracy can be improved by adjusting SRs using measured or estimated temperature and wind speed data at or near sampling sites. We also assessed the possibility of reusing Radiello® diffusive barriers previously used in the passive air samplers. The mean rate of gaseous Hg uptake was not significantly different between new and previously used diffusive barriers in both lab and outdoor deployments, irrespective of the applied cleaning procedure. No memory effect from Radiellos® previously deployed in a high Hg atmosphere was observed. However, a loss in replicate precision for the dirtiest Radiellos® in the indoor experiment suggests that cleaning is advisable prior to reuse.

LINEAGE BASED DIFFERENCES IN GRANDPARENTAL INVESTMENT: EVIDENCE FROM A LARGE BRITISH COHORT STUDY

2009 ◽  
Vol 41 (3) ◽  
pp. 355-379 ◽  
Author(s):  
THOMAS V. POLLET ◽  
MARK NELISSEN ◽  
DANIEL NETTLE
Keyword(s):  
Large Scale ◽  
Multiple Correspondence Analysis ◽  
Data Set ◽  
Paternity Uncertainty ◽  
Wide Range ◽  
Proxy Measure ◽  
British Cohort Study ◽  
The Difference ◽  
The Uk ◽  
Grandparental Investment

SummaryEvolutionary theory suggests that maternal grandparents will invest more in their grandchildren than paternal grandparents, due to the difference between the certainty of maternity and the uncertainty of paternity. Most tests of this prediction have tended to use retrospective ratings by grandchildren rather than examining grandparental behaviour. Using a large-scale data set from the UK (n>7000), significant differences are shown between maternal and paternal grandparents in terms of frequencies of contact with their newborn grandchildren, while controlling for a wide range of other variables. Maternal grandparents also provided a significantly wider range of financial benefits than paternal grandparents. Maternal grandparents were also more likely to provide essentials and gifts and extras for the baby. Multiple correspondence analysis showed that contact frequencies systematically related to other measures of grandparental investment, indicating that contact frequencies are a useful proxy measure to examine overall investment. Findings are discussed with reference to the paternity uncertainty hypothesis.

Difference Fourier Analysis of Glucose Embedded and Frozen Hydrated Purple Membrane

1982 ◽  
Vol 40 ◽  
pp. 74-75
Author(s):  
Jules S. Jaffe ◽  
Robert M. Glaeser
Keyword(s):  
Purple Membrane ◽  
Data Set ◽  
High Resolution Data ◽  
X Ray ◽  
X Ray Crystallography ◽  
Fourier Techniques ◽  
Versus Protein ◽  
The Difference ◽  
Difference Fourier ◽  
Ideal Method

Although difference Fourier techniques are standard in X-ray crystallography it has only been very recently that electron crystallographers have been able to take advantage of this method. We have combined a high resolution data set for frozen glucose embedded Purple Membrane (PM) with a data set collected from PM prepared in the frozen hydrated state in order to visualize any differences in structure due to the different methods of preparation. The increased contrast between protein-ice versus protein-glucose may prove to be an advantage of the frozen hydrated technique for visualizing those parts of bacteriorhodopsin that are embedded in glucose. In addition, surface groups of the protein may be disordered in glucose and ordered in the frozen state. The sensitivity of the difference Fourier technique to small changes in structure provides an ideal method for testing this hypothesis.

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