A new method for measuring air temperature profiles in the atmospheric boundary layer at high spatial and temporal resolution is presented. The measurements are based on Raman scattering distributed ...temperature sensing (DTS) with a fiber optic cable attached to a tethered balloon. These data were used to estimate the height of the stable nocturnal boundary layer. The experiment was successfully deployed during a two-day campaign in September 2009, providing evidence that DTS is well suited for this atmospheric application. Observed stable temperature profiles exhibit an exponential shape confirming similarity concepts of the temperature inversion close to the surface. The atmospheric mixing height (MH) was estimated to vary between 5 m and 50 m as a result of the nocturnal boundary layer evolution. This value is in good agreement with the MH derived from concurrent Radon-222 (222Rn) measurements and in previous studies.
Molecular hydrogen (H2 ), its isotopic signature (deuterium/hydrogen, δD), carbon monoxide (CO), and other compounds were studied in the exhaust of a passenger car engine fuelled with gasoline or ...methane and run under variable air-fuel ratios and operating modes. H2 and CO concentrations were largely reduced downstream of the three-way catalytic converter (TWC) compared to levels upstream, and showed a strong dependence on the air-fuel ratio (expressed as lambda, λ). The isotopic composition of H2 ranged from δD = -140per thousand to δD = -195per thousand upstream of the TWC but these values decreased to -270per thousand to -370per thousand after passing through the TWC. Post-TWC δD values for the fuel-rich range showed a strong dependence on TWC temperature with more negative δD for lower temperatures. These effects are attributed to a rapid temperature-dependent H-D isotope equilibration between H2 and water (H2 O). In addition, post TWC δD in H2 showed a strong dependence on the fraction of removed H2 , suggesting isotopic enrichment during catalytic removal of H2 with enrichment factors (straight epsilon) ranging from -39.8per thousand to -15.5per thousand depending on the operating mode. Our results imply that there may be considerable variability in real-world δD emissions from vehicle exhaust, which may mainly depend on TWC technology and exhaust temperature regime. This variability is suggestive of a δD from traffic that varies over time, by season, and by geographical location. An earlier-derived integrated pure (end-member) δD from anthropogenic activities of -270per thousand (Rahn et al., 2002) can be explained as a mixture of mainly vehicle emissions from cold starts and fully functional TWCs, but enhanced δD values by >50per thousand are likely for regions where TWC technology is not fully implemented. Our results also suggest that a full hydrogen isotope analysis on fuel and exhaust gas may greatly aid at understanding process-level reactions in the exhaust gas, in particular in the TWC.
Heavy metals which accumulate in soils may be harmful to soil and its boundary ecosystems. In this paper a unified risk assessment and risk management concept is proposed followed by a discussion on ...its practical implementation. To assess and manage risk, the application of a three-level evaluation system is presented, incorporating the degree of metal contamination. Levels for guide values, trigger values and clean up values are used. In order to assess exposure to heavy metals, three metal fractions like mobile, mobilisable and pseudo total metal fractions are introduced. Exceeding trigger and guide values at a site may be harmful to the risk receptors. Adequate site-specific mild remediation measures aim to diminish or eliminate risk without adversely affecting basic functions of soil. The importance of mobile and mobilisable metal concentrations is discussed in relation to the development of ecological and economical sound remediation techniques.
The International Halocarbons in Air Comparison Experiment (IHALACE) was conducted to document relationships between calibration scales among various laboratories that measure atmospheric greenhouse ...and ozone depleting gases. This study included trace gases such as chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs), as well as nitrous oxide, methane, sulfur hexafluoride, very short-lived halocompounds, and carbonyl sulfide. Many of these gases are present in the unpolluted atmosphere at pmol mol−1 (parts per trillion) or nmol mol−1 (parts per billion) levels. Six stainless steel cylinders containing natural and modified natural air samples were circulated among 19 laboratories. Results from this experiment reveal relatively good agreement (within a few percent) among commonly used calibration scales. Scale relationships for some gases, such as CFC-12 and CCl4, were found to be consistent with those derived from estimates of global mean mole fractions, while others, such as halon-1211 and CH3Br, revealed discrepancies. The transfer of calibration scales among laboratories was problematic in many cases, meaning that measurements tied to a particular scale may not, in fact, be compatible. Large scale transfer errors were observed for CH3CCl3 (10–100%) and CCl4 (2–30%), while much smaller scale transfer errors (< 1%) were observed for halon-1211, HCFC-22, and HCFC-142b. These results reveal substantial improvements in calibration over previous comparisons. However, there is room for improvement in communication and coordination of calibration activities with respect to the measurement of halogenated and related trace gases.
High frequency measurements of trifluoromethane (HFC-23, CHF3), a potent hydrofluorocarbon greenhouse gas, largely emitted to the atmosphere as a by-product of the production of the ...hydrochlorofluorocarbon HCFC-22 (CHClF2), at five core stations of the Advanced Global Atmospheric Gases Experiment (AGAGE) network, combined with measurements on firn air, old Northern Hemisphere air samples and Cape Grim Air Archive (CGAA) air samples, are used to explore the current and historic changes in the atmospheric abundance of HFC-23. These measurements are used in combination with the AGAGE 2-D atmospheric 12-box model and a Bayesian inversion methodology to determine model atmospheric mole fractions and the history of global HFC-23 emissions. The global modelled annual mole fraction of HFC-23 in the background atmosphere was 28.9 ± 0.6 pmol mol−1 at the end of 2016, representing a 28 % increase from 22.6 ± 0.4 pmol mol−1 in 2009. Over the same time frame, the modelled mole fraction of HCFC-22 increased by 19 % from 199 ± 2 to 237 ± 2 pmol mol−1. However, unlike HFC-23, the annual average HCFC-22 growth rate slowed from 2009 to 2016 at an annual average rate of −0.5 pmol mol−1 yr−2. This slowing atmospheric growth is consistent with HCFC-22 moving from dispersive (high fractional emissions) to feedstock (low fractional emissions) uses, with HFC-23 emissions remaining as a consequence of incomplete mitigation from all HCFC-22 production.Our results demonstrate that, following a minimum in HFC-23 global emissions in 2009 of 9.6 ± 0.6, emissions increased to a maximum in 2014 of 14.5 ± 0.6 Gg yr−1 and then declined to 12.7 ± 0.6 Gg yr−1 (157 Mt CO2 eq. yr−1) in 2016. The 2009 emissions minimum is consistent with estimates based on national reports and is likely a response to the implementation of the Clean Development Mechanism (CDM) to mitigate HFC-23 emissions by incineration in developing (non-Annex 1) countries under the Kyoto Protocol. Our derived cumulative emissions of HFC-23 during 2010–2016 were 89 ± 2 Gg (1.1 ± 0.2 Gt CO2 eq.), which led to an increase in radiative forcing of 1.0 ± 0.1 mW m−2 over the same period. Although the CDM had reduced global HFC-23 emissions, it cannot now offset the higher emissions from increasing HCFC-22 production in non-Annex 1 countries, as the CDM was closed to new entrants in 2009. We also find that the cumulative European HFC-23 emissions from 2010 to 2016 were ∼ 1.3 Gg, corresponding to just 1.5 % of cumulative global HFC-23 emissions over this same period. The majority of the increase in global HFC-23 emissions since 2010 is attributed to a delay in the adoption of mitigation technologies, predominantly in China and East Asia. However, a reduction in emissions is anticipated, when the Kigali 2016 amendment to the Montreal Protocol, requiring HCFC and HFC production facilities to introduce destruction of HFC-23, is fully implemented.
Hydrochlorofluorocarbons (HCFCs) are the first, but
temporary, substitution products for the strong ozone-depleting
chlorofluorocarbons (CFCs). HCFC consumption and production are currently
regulated ...under the Montreal Protocol on Substances that Deplete the Ozone
Layer and their emissions have started to stabilize or even decrease. As
HCFC-22 (CHClF2) is by far the most abundant HCFC in today's
atmosphere, it is crucial to continue to monitor the evolution of its
atmospheric concentration. In this study, we describe an improved HCFC-22
retrieval strategy from ground-based high-resolution Fourier transform
infrared (FTIR) solar spectra recorded at the high-altitude scientific
station of Jungfraujoch, the Swiss Alps, 3580 m a.m.s.l. (above mean sea level). This new
strategy distinguishes tropospheric and lower-stratospheric partial columns.
Comparisons with independent datasets, such as the Advanced Global Atmospheric Gases
Experiment (AGAGE) and the Michelson Interferometer for Passive Atmospheric
Sounding (MIPAS), supported by models, such as the Belgian Assimilation System for
Chemical ObErvation (BASCOE) and the Whole Atmosphere Community Climate
Model (WACCM), demonstrate the validity of our tropospheric and lower-stratospheric long-term time series. A trend analysis on the datasets used
here, now spanning 30 years, confirms the last decade's decline in
the HCFC-22 growth rate. This updated retrieval strategy can be adapted for
other ozone-depleting substances (ODSs), such as CFC-12. Measuring or
retrieving ODS atmospheric concentrations is essential for scrutinizing the
fulfilment of the globally ratified Montreal Protocol.
Measurements of H
2
at the high-altitude site of Jungfraujoch, Switzerland are reported upon for the period of August, 2005-November, 2009. The time series consists of measurements that are primarily ...representative of free tropospheric background conditions. Highest background H
2
mixing ratios were observed in May, while the lowest were observed in November. The mean seasonal H
2
peak-to-trough amplitude of 21 parts per billion (ppb, 10
-9
dry air mixing ratio) at Jungfraujoch was considerably less than at other stations at similar latitudes and the seasonal minimum in November was comparatively delayed. These differences are primarily attributed to a dampening and delay of the surface soil sink signal during its vertical propagation to the free troposphere. Excess (mixing ratio minus corresponding baseline value) H
2
(
2
) and excess CO (CO) displayed no significant correlation. This lacking correlation is attributed to H
2
removal by soil during transport to Jungfraujoch, thereby significantly altering the H
2
CO ratio from traffic combustion sources, which is the largest source of anthropogenic H
2
influencing measurements at Jungfraujoch.
The performance of 18 European institutions involved in long-term non-methane hydrocarbon (NMHC) measurements in ambient air within the framework of the Global Atmosphere Watch (GAW) and the European ...Monitoring and Evaluation Programme (EMEP) was assessed with respect to data quality objectives (DQOs) of ACTRIS (Aerosols, Clouds, and Trace gases Research InfraStructure Network) and GAW. Compared to previous intercomparison studies the DQOs define a novel approach to assess and ensure a high quality of the measurements. Having already been adopted by GAW, the ACTRIS DQOs are demanding with deviations to a reference value of less than 5 % and a repeatability of better than 2 % for NMHC mole fractions above 0.1 nmol mol−1. The participants of the intercomparison analysed two dry gas mixtures in pressurised cylinders, a 30-component NMHC mixture in nitrogen (NMHC_N2) at approximately 1 nmol mol−1 and a whole air sample (NMHC_air), following a standardised operation procedure including zero- and calibration gas measurements. Furthermore, participants had to report details on their instruments and assess their measurement uncertainties. The NMHCs were analysed either by gas chromatography–flame ionisation detection (GC-FID) or by gas chromatography–mass spectrometry (GC-MS). For the NMHC_N2 measurements, 62 % of the reported values were within the 5 % deviation class corresponding to the ACTRIS DQOs. For NMHC_air, generally more frequent and larger deviations to the assigned values were observed, with 50 % of the reported values within the 5 % deviation class. Important contributors to the poorer performance in NMHC_air compared to NMHC_N2 were a more complex matrix and a larger span of NMHC mole fractions (0.03–2.5 nmol mol−1). The performance of the participating laboratories were affected by the different measurement procedures such as the usage of a two-step vs. a one-step calibration, breakthroughs of C2–C3 hydrocarbons in the focussing trap, blank values in zero-gas measurements (especially for those systems using a Nafion® Dryer), adsorptive losses of aromatic compounds, and insufficient chromatographic separation.
Semi-continuous measurements of atmospheric molecular hydrogen
(
H
2
)
and carbon monoxide (CO) were performed at a suburban sampling site in Switzerland from November 2002 to February 2005. The ...presented data provide information about time series, seasonal and diurnal cycles as well as sources and sinks in a suburban environment. Such records become increasingly important for the assessment of the effects of a possible future hydrogen economy on the environment. No significant trend of background
H
2
concentrations could be observed for the considered period. Seasonal cycles show the expected pattern with maxima in winter and minima in summer and autumn. When extracting the background
H
2
mixing ratios, the absolute levels as well as the seasonal amplitude agree well with literature data from semi-rural and remote sites. The
H
2
dry deposition velocity for summer days with low winds is estimated to be between
0.5
×
10
-
4
to
1
×
10
-
4
m
s
-
1
. Diurnal cycles are dominated by
H
2
emissions from nearby traffic. The influence of traffic-related emissions is also corroborated by a high
H
2
to CO correlation. Typical molar
H
2
to CO ratios from traffic were found to be 0.33 on a molar basis (ppb/ppb). A reduction of 37–62% in European anthropogenic
H
2
emissions is estimated for a period covering the last 25 years. Since the ambient
H
2
concentration did not decline during the same period, other simultaneous changes of sinks or sources of
H
2
must have compensated this reduction.
Our three academic institutions, Indiana University, Northwestern Memorial Hospital, and Wake Forest, were among the first in the United States to implement the Beckman Coulter AU5822 series ...chemistry analyzers. We undertook this post-hoc multi-center study by merging our data to determine performance characteristics and the impact of methodology changes on analyte measurement.
We independently completed performance validation studies including precision, linearity/analytical measurement range, method comparison, and reference range verification. Complete data sets were available from at least one institution for 66 analytes with the following groups: 51 from all three institutions, and 15 from 1 or 2 institutions for a total sample size of 12,064.
Precision was similar among institutions. Coefficients of variation (CV) were <10% for 97%. Analytes with CVs >10% included direct bilirubin and digoxin. All analytes exhibited linearity over the analytical measurement range. Method comparison data showed slopes between 0.900-1.100 for 87.9% of the analytes. Slopes for amylase, tobramycin and urine amylase were <0.8; the slope for lipase was >1.5, due to known methodology or standardization differences. Consequently, reference ranges of amylase, urine amylase and lipase required only minor or no modification.
The four AU5822 analyzers independently evaluated at three sites showed consistent precision, linearity, and correlation results. Since installations, the test results had been well received by clinicians from all three institutions.
•Objectives - Our three academic institutions, Indiana University, Northwestern Memorial Hospital, and Wake Forest, were among the first in the United States to implement the Beckman Coulter AU5822 series chemistry analyzers. We undertook this post-hoc multi-center study by merging our data to determine performance characteristics and the impact of methodology changes on analyte measurement.•Design and Methods: We independently completed performance validation studies including precision, linearity/analytical measurement range, method comparison, and reference range verification. Complete data sets were available from at least one institution for 66 analytes with the following groups: 51 from all three institutions., and 15 from 1 or 2 institutions for a total sample size of 12,064.•Results: Precision was similar among institutions. Coefficients of variation (CV) were <10% for 97%. Analytes with CVs >10% included direct bilirubin and digoxin. All analytes exhibited linearity over the analytical measurement range. Method comparison data showed slopes between 0.900-1.100 for 87.9% of the analytes. Slopes for amylase, tobramycin and urine amylase were <0.8; the slope for lipase was >1.5, due to known methodology or standardization differences. Consequently, reference ranges required only minor or no modification with the expected exceptions of amylase, urine amylase and lipase.•Conclusion: The four AU5822 analyzers independently evaluated at three sites showed consistent precision, linearity, and correlation results. Since installations, the test results had been well received by clinicians from all three institutions.
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