scholarly journals Atmospheric bromoform at Cape Point, South Africa: a first time series on the African continent

2017 ◽  
Author(s):  
Brett Kuyper ◽  
Carl J. Palmer ◽  
Casper Labuschagne ◽  
Chris J. C. Reason
Keyword(s):  
South Africa ◽  
Austral Spring ◽  
Data Set ◽  
Air Masses ◽  
Mixing Ratios ◽  
Front End ◽  
Potential Source ◽  
High Concentrations ◽  
Marine Air ◽  
First Time

Abstract. Bromoform mixing ratios in marine air were measured at Cape Point Global Atmospheric Watch Station, South Africa. This represents the first ever bromoform data set recorded at this unique location. Manual daily measurements were made during a month long field campaign (austral spring 2011) using a GC-ECD with a custom built front end thermal desorption trap. The measured concentrations ranged between 2.3 ± 0.4 and 84.7 ± 10.8 ppt with a mean of 24.7 ± 3.1 ppt. Our analysis shows the concentration of bromform varies significantly according to wind direction and the trajectory of the air mass sampled. Air masses which had come into contact with multiple potential source of bromoform showed the highest average mixing ratios. The measurements reported here represent some of the highest recorded coastal bromoform concentrations globally. These high concentrations may be explained by the multiple local sources of bromoform around Cape Point.

scholarly journals Atmospheric bromoform at Cape Point, South Africa: an initial fixed-point data set on the African continent

2018 ◽  
Vol 18 (8) ◽  
pp. 5785-5797 ◽  
Author(s):  
Brett Kuyper ◽  
Carl J. Palmer ◽  
Casper Labuschagne ◽  
Chris J. C. Reason
Keyword(s):  
South Africa ◽  
Trajectory Analysis ◽  
Gas Chromatograph ◽  
Austral Spring ◽  
Data Set ◽  
Source Areas ◽  
Mixing Ratios ◽  
Point Data ◽  
St Helena ◽  
Marine Air

Abstract. Bromoform mixing ratios in marine air were measured at Cape Point Global Atmospheric Watch Station, South Africa. This represents the first such bromoform data set recorded at this location. Manual daily measurements were made during a month-long field campaign (austral spring 2011) using a gas chromatograph-electron capture detector (GC-ECD) with a custom-built front end thermal desorption trap. The measured concentrations ranged between 4.4 and 64.6 (± 22.2 %) ppt with a mean of 24.8 ± 14.8 ppt. The highest mixing ratios recorded here occurred at, or shortly after, low tide. The diurnal cycle exhibited a morning and evening maximum with lower concentrations throughout the rest of the day. Initial analysis of the data presented indicates that the local kelp beds were the dominant source of the bromoform reported. A concentration-weighted trajectory analysis of the bromoform measurements suggests that two offshore source areas may exist. These source areas appear to be centred on the Agulhas retroflection and extend from St Helena Bay to the southwest.

scholarly journals Characterization of Transport Regimes and the Polar Dome during Arctic Spring and Summer using in-situ Aircraft Measurements

2019 ◽  
Author(s):  
Heiko Bozem ◽  
Peter Hoor ◽  
Daniel Kunkel ◽  
Franziska Köllner ◽  
Johannes Schneider ◽  
...  
Keyword(s):  
Lower Troposphere ◽  
High Arctic ◽  
The Arctic ◽  
Trace Gas ◽  
Second Phase ◽  
Aerosol Formation ◽  
Transport Barrier ◽  
Data Set ◽  
Air Masses ◽  
Mixing Ratios

Abstract. The springtime composition of the Arctic lower troposphere is to a large extent controlled by transport of mid-latitude air masses into the Arctic, whereas during the summer precipitation and natural sources play the most important role. Within the Arctic region, there exists a transport barrier, known as the polar dome, which results from sloping isentropes. The polar dome, which varies in space and time, exhibits a strong influence on the transport of air masses from mid-latitudes, enhancing it during winter and inhibiting it during summer. Furthermore, a definition for the location of the polar dome boundary itself is quite sparse in the literature. We analyzed aircraft based trace gas measurements in the Arctic during two NETCARE airborne field camapigns (July 2014 and April 2015) with the Polar 6 aircraft of Alfred Wegener Institute Helmholtz Center for Polar and Marine Research (AWI), Bremerhaven, Germany, covering an area from Spitsbergen to Alaska (134° W to 17° W and 68° N to 83° N). For the spring (April 2015) and summer (July 2014) season we analyzed transport regimes of mid-latitude air masses travelling to the high Arctic based on CO and CO2 measurements as well as kinematic 10-day back trajectories. The dynamical isolation of the high Arctic lower troposphere caused by the transport barrier leads to gradients of chemical tracers reflecting different local chemical life times and sources and sinks. Particularly gradients of CO and CO2 allowed for a trace gas based definition of the polar dome boundary for the two measurement periods with pronounced seasonal differences. For both campaigns a transition zone rather than a sharp boundary was derived. For July 2014 the polar dome boundary was determined to be 73.5° N latitude and 299–303.5 K potential temperature, respectively. During April 2015 the polar dome boundary was on average located at 66–68.5° N and 283.5–287.5 K. Tracer-tracer scatter plots and probability density functions confirm different air mass properties inside and outside of the polar dome for the July 2014 and April 2015 data set. Using the tracer derived polar dome boundaries the analysis of aerosol data indicates secondary aerosol formation events in the clean summertime polar dome. Synoptic-scale weather systems frequently disturb this transport barrier and foster exchange between air masses from midlatitudes and polar regions. During the second phase of the NETCARE 2014 measurements a pronounced low pressure system south of Resolute Bay brought inflow from southern latitudes that pushed the polar dome northward and significantly affected trace gas mixing ratios in the measurement region. Mean CO mixing ratios increased from 77.9 ± 2.5 ppbv to 84.9 ± 4.7 ppbv from the first period to the second period. At the same time CO2 mixing ratios significantly dropped from 398.16 ± 1.01 ppmv to 393.81 ± 2.25 ppmv. We further analysed processes controlling the recent transport history of air masses within and outside the polar dome. Air masses within the spring time polar dome mainly experienced diabatic cooling while travelling over cold surfaces. In contrast air masses in the summertime polar dome were diabatically heated due to insolation. During both seasons air masses outside the polar dome slowly descended into the Arctic lower troposphere from above caused by radiative cooling. The ascent to the middle and upper troposphere mainly took place outside the Arctic, followed by a northward motion. Our results demonstrate the successful application of a tracer based diagnostic to determine the location of the polar dome boundary.

scholarly journals Classification of clouds sampled at the puy de Dôme (France) based on 10 yr of monitoring of their physicochemical properties

2014 ◽  
Vol 14 (3) ◽  
pp. 1485-1506 ◽  
Author(s):  
L. Deguillaume ◽  
T. Charbouillot ◽  
M. Joly ◽  
M. Vaïtilingom ◽  
M. Parazols ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Chemical Composition ◽  
Inorganic Compounds ◽  
Average Concentration ◽  
Anthropogenic Sources ◽  
Back Trajectory ◽  
Data Set ◽  
Air Masses ◽  
High Concentrations ◽  
Inorganic Constituents

Abstract. Long-term monitoring of the chemical composition of clouds (73 cloud events representing 199 individual samples) sampled at the puy de Dôme (pdD) station (France) was performed between 2001 and 2011. Physicochemical parameters, as well as the concentrations of the major organic and inorganic constituents, were measured and analyzed by multicomponent statistical analysis. Along with the corresponding back-trajectory plots, this allowed for distinguishing four different categories of air masses reaching the summit of the pdD: polluted, continental, marine and highly marine. The statistical analysis led to the determination of criteria (concentrations of inorganic compounds, pH) that differentiate each category of air masses. Highly marine clouds exhibited high concentrations of Na+ and Cl−; the marine category presented lower concentration of ions but more elevated pH. Finally, the two remaining clusters were classified as "continental" and "polluted"; these clusters had the second-highest and highest levels of NH4+, NO3−, and SO24−, respectively. This unique data set of cloud chemical composition is then discussed as a function of this classification. Total organic carbon (TOC) is significantly higher in polluted air masses than in the other categories, which suggests additional anthropogenic sources. Concentrations of carboxylic acids and carbonyls represent around 10% of the organic matter in all categories of air masses and are studied for their relative importance. Iron concentrations are significantly higher for polluted air masses and iron is mainly present in its oxidation state (+II) in all categories of air masses. Finally, H2O2 concentrations are much more varied in marine and highly marine clouds than in polluted clouds, which are characterized by the lowest average concentration of H2O2. This data set provides concentration ranges of main inorganic and organic compounds for modeling purposes on multiphase cloud chemistry.

scholarly journals Total OH reactivity measurements in Paris during the 2010 MEGAPOLI winter campaign

2012 ◽  
Vol 12 (4) ◽  
pp. 10937-10994 ◽  
Author(s):  
C. Dolgorouky ◽  
V. Gros ◽  
R. Sarda-Esteve ◽  
V. Sinha ◽  
J. Williams ◽  
...  
Keyword(s):  
Hydroxyl Radicals ◽  
Loss Rate ◽  
Trace Gases ◽  
Air Masses ◽  
Anthropogenic Origin ◽  
Inorganic Species ◽  
Surrounding Areas ◽  
Marine Air ◽  
First Time ◽  
Comparative Reactivity

Abstract. Hydroxyl radicals play a central role in the troposphere as they control the lifetime of many trace gases. Measurement of OH reactivity (OH loss rate) is important to better constrain the OH budget and also to evaluate the completeness of measured VOC budget. Total atmospheric OH reactivity was measured for the first time in an European Megacity: Paris and its surrounding areas with 12 million inhabitants, during the MEGAPOLI winter campaign 2010. The method deployed was the Comparative Reactivity Method (CRM). The measured dataset contains both measured and calculated OH reactivity from CO, NOx and VOCs measured via PTR-MS, GC-FID and GC-MS instruments. The reactivities observed in Paris covered a range from 10 s−1 to 130 s−1, indicating a large loading of chemical reactants. The present study showed that, when clean marine air masses influenced Paris, the purely local OH reactivity (20 s−1) is well explained by the measured species. Nevertheless, when there is a continental import of air masses, high levels of OH reactivity were obtained (120–130 s−1) and the missing OH reactivity measured in this case jumped to 75%. Using covariations of the missing OH reactivity to secondary inorganic species in fine aerosols, we suggest that the missing OH reactants were most likely highly oxidized compounds issued from photochemically processed air masses of anthropogenic origin.

scholarly journals Carbon Dioxide and Methane in the China Sea Shelf Boundary Layer Observed by Cavity Ring-Down Spectroscopy

2017 ◽  
Vol 34 (10) ◽  
pp. 2233-2244 ◽  
Author(s):  
Kun-Peng Zang ◽  
Ling-Xi Zhou ◽  
Ju-Ying Wang
Keyword(s):  
Carbon Dioxide ◽  
Boundary Layer ◽  
Measurement Data ◽  
Cavity Ring Down Spectroscopy ◽  
Trade Winds ◽  
Air Masses ◽  
China Sea ◽  
Mixing Ratios ◽  
First Time ◽  
Cavity Ring Down

AbstractHigh-accuracy continuous ship-based cavity ring-down spectroscopy was used to simultaneously measure the mixing ratios of the carbon dioxide and methane in the China Sea shelf boundary layer for the first time, from 22 March to 2 April 2013. The mixing ratios of CO2 and CH4 ranged from 397.40 to 432.40 µmol mol−1 and from 1812.8 to 2068.7 nmol mol−1, respectively. Measurement data showed latitudinal distributions, with a slight fluctuation between 35.52° and 22.00°N but a sharp decline from 22.00° to 20.50°N. This distribution was not only the result of airmass transport from the Asian continent and Pacific Ocean induced by winter monsoon and trade winds but also by air–sea exchange and atmospheric chemical processes. Moreover, mixing ratios of CO2 and CH4 showed a temporal and spatial correlation that was possibly due to the effects of multisource air masses and their mixed status.

scholarly journals Temporal variations of black carbon in Guangzhou, China, in summer 2006

2010 ◽  
Vol 10 (14) ◽  
pp. 6471-6485 ◽  
Author(s):  
R. L. Verma ◽  
L. K. Sahu ◽  
Y. Kondo ◽  
N. Takegawa ◽  
S. Han ◽  
...  
Keyword(s):  
Black Carbon ◽  
Temporal Variations ◽  
Back Trajectories ◽  
Air Masses ◽  
Mixing Ratios ◽  
Diurnal Patterns ◽  
Air Mass Types ◽  
The Pearl River ◽  
Carbon Dioxide Co2 ◽  
Marine Air

Abstract. In situ measurements of the mass concentration of black carbon (BC) and mixing ratios of carbon monoxide (CO) and carbon dioxide (CO2) were made at Guangzhou, an urban measurement site in the Pearl River Delta (PRD), China, in July 2006. The average ± standard deviation (SD) concentrations of BC, CO, and CO2 were 4.7± 2.3 μgC m−3, 798± 459 ppbv, and 400± 13 ppmv, respectively. The trends of these species were mainly controlled by synoptic-scale changes in meteorology during the campaign. Based on back trajectories, data are analyzed separately for two different air mass types representing northerly and southerly flows. The northerly air masses, which constituted ~25% of the campaign, originated mostly in the PRD and hence represent observations on regional scales. On the other hand, during southerly flow (~75%), the measurements were influenced by dilution due to cleaner marine air. The diurnal patterns of BC, CO, and CO2 exhibited peak concentrations during the morning and evening hours coinciding with rush-hour traffic. The ratios of OC/BC were lower during the morning hour peaks in the concentrations of primary pollutants due to their fresh emissions mainly from vehicular traffic in Guangzhou. The diurnal variations of BC observed in southerly air masses tended to follow the traffic patterns of heavy-duty vehicles (HDV) in Guangzhou, while the roles of other sources need to be investigated. The slopes of ΔBC/ΔCO, ΔBC/ΔCO2, and ΔCO/ΔCO2 observed during northerly flows were 0.0045 μgC m−3/ppbv, 0.13 μgC m−3/ppmv, and 49.4 ppbv/ppmv, respectively, agreeing reasonably with their respective emission ratios derived from regional emission inventories.

scholarly journals Temporal variation of elemental carbon in Guangzhou, China, in summer 2006

2009 ◽  
Vol 9 (6) ◽  
pp. 24629-24667 ◽  
Author(s):  
R. L. Verma ◽  
L. K. Sahu ◽  
Y. Kondo ◽  
N. Takegawa ◽  
S. Han ◽  
...  
Keyword(s):  
Elemental Carbon ◽  
Back Trajectories ◽  
Air Masses ◽  
Traffic Pattern ◽  
Mixing Ratios ◽  
Diurnal Patterns ◽  
Air Mass Types ◽  
The Pearl River ◽  
Carbon Dioxide Co2 ◽  
Marine Air

Abstract. In situ measurements of the mass concentration of elemental carbon (EC) and mixing ratios of carbon monoxide (CO) and carbon dioxide (CO2) were made at Guangzhou, an urban measurement site in the Pearl River Delta (PRD), China, in July 2006. The average±standard deviation (SD) concentrations of EC, CO, and CO2 were 4.7±2.3 μg C m−3, 798±459 ppbv and 400±13 ppmv, respectively. The trends of these species were mainly controlled by synoptic-scale changes in meteorology during the campaign. Based on back trajectories, data are analyzed separately for two different air mass types representing northerly and southerly flows. Northerly air masses, constituting about 25% of the campaign, were mainly impacted by stagnant conditions, resulting in elevated levels of pollutants. On the other hand, southerly air masses measured during most of the campaign were mostly influenced by clean marine air. The diurnal patterns of EC, CO, and CO2 exhibited peak concentrations during the morning and evening hours coinciding with rush-hour traffic. The diurnal variations of EC and ΔEC/ΔCO closely followed the traffic pattern of heavy-duty vehicles (HDV) in Guangzhou, similar to that observed in Beijing. The level of EC in this campaign was similar to values reported during previous studies at other sites surrounding Guangzhou. The average slopes of ΔEC/ΔCO, ΔEC/ΔCO2, and ΔCO/ΔCO2 were 0.0054 μg C m−3/ppbv, 0.15 μg C m−3/ppmv, and 46.4 ppbv/ppmv, respectively, agreeing reasonably well with their respective emission ratios derived from regional emission inventories.

scholarly journals Chemical transformations of Hg° during Arctic mercury depletion events sampled from the NASA DC-8

2010 ◽  
Vol 10 (4) ◽  
pp. 10077-10112 ◽  
Author(s):  
S. Y. Kim ◽  
R. Talbot ◽  
H. Mao ◽  
D. R. Blake ◽  
G. Huey ◽  
...  
Keyword(s):  
Atmospheric Mercury ◽  
Box Model ◽  
The Arctic ◽  
Chemical Transformations ◽  
Gas Phase Reactions ◽  
Air Masses ◽  
Airborne Measurements ◽  
Mixing Ratios ◽  
High Concentrations ◽  
Halogen Species

Abstract. Atmospheric Mercury Depletion Events (MDEs) in Arctic springtime were investigated utilizing a box model based on airborne measurements from the NASA DC-8 during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) field campaign. Measurements showed that MDEs occurred near the surface and always over the Arctic Ocean accompanied by concurrent ozone (O3) depletion, enhancement in Br2 mixing ratios, and decreases in ethyne and light weight alkanes. Backward trajectories indicated that most air masses inside the MDEs originated at low altitude over the ocean presumably generating a halogen-rich environment. We developed a box model which considered only gas phase reactions of mercury, halogen species, and O3 chemistry. We conducted a series of sensitivity simulations to determine the factors that are of most importance to MDE formation. The box model results suggested that continuous enhancement of Br2 mixing ratios, a high intensity of solar radiation, or a relatively high NOx regime expedited Hg° depletion. These environments generated high concentrations of Br radical, and thus the model results indicated that the Br radical was very important for Hg° depletion. Utilizing different rate constants for reaction of Hg° + Br produced times to reach Hg° depletion ranging from 22 to 32 h.

scholarly journals Chemical characteristics assigned to trajectory clusters during the MINOS campaign

2003 ◽  
Vol 3 (1) ◽  
pp. 107-134 ◽  
Author(s):  
M. Traub ◽  
H. Fischer ◽  
M. de Reus ◽  
R. Kormann ◽  
J. Heland ◽  
...  
Keyword(s):  
Western Europe ◽  
Source Region ◽  
Lower Troposphere ◽  
Mediterranean Area ◽  
Back Trajectories ◽  
Air Masses ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
The Mediterranean ◽  
High Concentrations

Abstract. During the Mediterranean Intensive Oxidant Study (MINOS) in August 2001 a total of 14 measurement flights were performed with the DLR Falcon aircraft from Heraklion, Crete. One objective of this campaign was to investigate the role of long-range transport of pollutants into the Mediterranean area. An analysis of 5-day back trajectories indicates that in the lower troposphere (0–4 km) air masses originated from eastern and western Europe, in the mid-troposphere (4–8 km) from the Atlantic Ocean region and in the upper troposphere (8–14 km) from North Artlantic Ocean/North America  (NAONA) as well as South Asia. We allocated all back trajectories to clusters based on their ending height and source region. The mixing ratios of ozone, nitrogen oxide, total reactive oxidized nitrogen (NOy), formaldehyde, methanol, acetonitrile, acetone, peroxyacetyl nitrate (PAN), carbon dioxide, carbon monoxide and methane measured along the flight tracks are examined in relation to the different cluster trajectories. In the lower troposphere the mean gas mixing ratios of the eastern Europe cluster trajectories were significantly higher than that from western Europe. Considering 2-day instead of 5-day trajectories the relative differences between the concentrations of these two clusters increased. In the upper troposphere relatively high concentrations of  O3 and NOy, combined with low CO of the NAONA trajectories indicate mixing with stratospheric air masses.

scholarly journals Trends and Emissions of Six Perfluorocarbons in the Northern and Southern Hemisphere

2019 ◽  
Author(s):  
Elise S. Droste ◽  
Karina E. Adcock ◽  
Matthew J. Ashfold ◽  
Charles Chou ◽  
Zoë Fleming ◽  
...  
Keyword(s):  
Time Series ◽  
Southern Hemisphere ◽  
Emission Rates ◽  
Data Set ◽  
Air Samples ◽  
Mixing Ratios ◽  
Co2 Equivalent ◽  
First Time ◽  
Global Emissions ◽  
Cape Grim

Abstract. Perfluorocarbons (PFCs) are potent greenhouse gases with Global Warming Potentials up to several thousand times greater than CO2 on a 100-year time horizon. The lack of any significant sinks for PFCs means that they have long atmospheric lifetimes on the order of thousands of years. Anthropogenic production is thought to be the only source for most PFCs. Here we report an update on the global atmospheric abundances of the following PFCs, most of which have for the first time been separated according to their isomers: c-octafluorobutane (c-C4F8), n-decafluorobutane (n-C4F10), n-dodecafluoropentane (n-C5F12), n-tetradecafluorohexane (n-C6F14), and n-hexadecafluoroheptane (n-C7F16). Additionally, we report the first data set on the atmospheric mixing ratios of perfluoro(2-methylpentane) (i-C6F14). The existence and significance of PFC isomers has not been reported before, due to the analytical challenges of separating them. The time series spans a period from 1978 to the present. Several datasets are used to investigate temporal and spatial trends of these PFCs: time series of air samples collected at Cape Grim, Australia, from 1978 to the start of 2018; a time series of air samples collected between July 2015 and April 2017 at Tacolneston, UK; and intensive campaign-based sampling collections from Taiwan. Although the remote background Southern Hemispheric Cape Grim time series indicates that recent growth rates of most of these PFCs are lower than in the 1990s, we continue to see significantly increasing mixing ratios that are between 6 % to 27 % higher by the end of 2017 compared to abundances measured in 2010. Air samples from Tacolneston show a positive offset in PFC mixing ratios compared to the Southern Hemisphere baseline. The highest mixing ratios and variability are seen in air samples from Taiwan, which is therefore likely situated much closer to PFC sources, confirming predominantly Northern Hemispheric emissions for most PFCs. Even though these PFCs occur in the atmosphere at levels of parts per trillion molar or less, their total cumulative global emissions translate into 833 million metric tonnes of CO2 equivalent by the end of 2017, 23 % of which has been emitted in the last eight years. Almost two-thirds of the CO2 equivalent emissions are attributable to c-C4F8, which currently also has the highest emission rates that continue to grow. Despite this, the sources of all PFCs covered in this work remain poorly constrained and reported emissions in global databases do not account for the abundances found in the atmosphere.

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