Browsing by Author "Griffith, DWT"
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- ItemAbsolute calibration of the intramolecular site preference of N-15 fractionation in tropospheric N2O by FT-IR spectroscopy(American Chemical Society, 2009-03-15) Griffith, DWT; Parkes, SD; Haverd, V; Paton-Walsh, C; Wilson, SRNitrous oxide (N2O) plays important roles in atmospheric chemistry both as a greenhouse gas and in stratospheric ozone depletion. Isotopic measurements of N2O have provided an invaluable insight into understanding its atmospheric sources and sinks. The preference for N-15 fractionation between the central and terminal positions (the "site preference") is particularly valuable because it depends principally on the processes involved in N2O production or consumption, rather than the N-15 content of the substrate from which it is formed. Despite the value of measurements of the site preference, there is no internationally recognized standard reference material of accurately known and accepted site preference, and there has been some lack of agreement in published studies aimed at providing such a standard. Previous work has been based on isotope ratio mass spectrometry (IRMS); in this work we provide an absolute calibration for the intramolecular site preference of N-15 fractionation of working standard gases used in our laboratory by a completely independent technique-high-resolution Fourier transform infrared (FT-IR) spectroscopy. By reference to this absolute calibration, we determine the site preference for 25 samples of tropospheric N2O collected under clean air conditions to be 19.8 parts per thousand +/- 2.1 parts per thousand. This result is in agreement with that based on the earlier absolute calibration of Toyoda and Yoshida (Toyoda, S.; Yoshida, N. Anal. Chem. 1999, 71, 4711-4718) who found an average tropospheric site preference of 18.7 parts per thousand +/- 2.2 parts per thousand. We now recommend an interlaboratory exchange of working standard N2O gases as the next step to providing an international reference standard. © 2009, American Chemical Society
- ItemCave atmosphere; a guide to calcification and a methane sink(Elsevier; Cambridge Publications, 2009-06-23) Waring, CL; Griffith, DWT; Wilson, SR; Hurry, SStudies of cave environments and speleothem growth are an important step towards quantitative speleothem palaeoclimate interpretation. Net accumulation of CaCO3 (speleothem growth) requires a perturbation to Gas-Aqueous-Solid equilibrium conditions in the cave environment (Aq. chem., T, P, pCO2). The largest equilibrium change in a ventilated cave environment causing speleothem growth is fluctuating pCO2 as a response to the cave air exchange, driven by external temperature. An intense 3-week field campaign in May 2008 (winter) using an FTIR spectrometer continuously measured (5 min) trace gases (CO2, CH4, N2O) H2O and δ13CCO2. Simultaneous drip-water pH, air flow, temperature, pressure, and relative humidity was logged by sensors in the cave together with external rainfall, temperature, pressure, and relative humidity. Drip water was sampled twice daily, coinciding with CO2 maxima and minima, for dissolved inorganic carbonate DIC, δ13CDIC, dissolved organic carbonate DOC, δ13CDOC, alkalinity, anions, and cations. Further spot samples were taken for drip-water stable isotopes, 14CDIC, and 3H. Low pCO2 in the morning cave air causes rapid speleothem growth with CO2 exsolved to the cave atmosphere lowering drip-water pH. pCO2 increases to an evening maxima and slows speleothem growth before early morning T induced ventilation decreases pCO2. δ13CCO2 has an antithetic relationship with CO2, with low pCO2 morning air the highest δ13CCO2 at -8 ‰ PDB. A Keeling analysis of end-member component mixing reveals the proportion of external air drawn into the cave and CO2 produced from speleothem formation through the diurnal cycle. Methane concentration in cave air also cycles through a diurnal pattern, negatively correlated with CO2. The methane concentration ranges from normal atmospheric 1700 ppb to <200 ppb and cycles 1000 ppb in only a few hours. Methane consumption is very rapid, suggesting a biogeochemical mechanism.
- ItemComparison of in-situ water vapour isotope analysers(American Geophysical Union, 2011-12-05) Element, A; Parkes, SD; Griffith, DWT; Wang, L; McCabe, MFRecently there have been a number of spectroscopic based in-situ water vapour isotope analysers developed. These analysers are capable of providing datasets that are useful for a range studies including interpreting rapid fluctuations associated with land atmosphere exchange processes, and validation of process based models that work on different spatial and temporal scales. Here we present a comparison of three spectroscopic analysers that provide in-situ analysis of water vapour isotopes. These include a Fourier Transform InfraRed (FTIR) spectroscopy based system (broad band technique), a system based on Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS), and a Wavelength-Scanned Cavity Ring-Down Spectroscopy (WS-CRDS) system. Using a continuous flow calibration system, liquid isotopic standards were vaporised and used to determine the response of the three analysers to changes isotopic composition and the water vapour mixing ratio. Based on these experiments it was shown that all three analysers required significant corrections to move the raw data onto the Standard Mean Ocean Water (SMOW) scale. We then deployed the three analysers at a coastal location near Sydney, Australia where diurnal temperature variations are relatively small and high mixing ratios are generally observed. The WS-CRDS and OA-ICOS were then deployed in central NSW, Australia where large diurnal temperature variations and relatively low mixing ratios were observed. The in-situ isotope data collected from the three analysers is then compared between these two locations.
- ItemComposition of clean marine air and biogenic influences on VOCs during the MUMBA campaign(MDPI AG, 2019-07-10) Guérette, ÉA; Paton-Walsh, C; Galbally, IE; Molloy, SB; Lawson, S; Kubistin, D; Buchholz, R; Griffith, DWT; Langenfelds, RL; Krummel, PB; Loh, Z; Chambers, SD; Griffiths, AD; Keywood, MD; Selleck, PW; Dorminick, D; Humphries, R; Wilson, SRVolatile organic compounds (VOCs) are important precursors to the formation of ozone and fine particulate matter, the two pollutants of most concern in Sydney, Australia. Despite this importance, there are very few published measurements of ambient VOC concentrations in Australia. In this paper, we present mole fractions of several important VOCs measured during the campaign known as MUMBA (Measurements of Urban, Marine and Biogenic Air) in the Australian city of Wollongong (34°S). We particularly focus on measurements made during periods when clean marine air impacted the measurement site and on VOCs of biogenic origin. Typical unpolluted marine air mole fractions during austral summer 2012-2013 at latitude 34°S were established for CO2 (391.0 ± 0.6 ppm), CH4 (1760.1 ± 0.4 ppb), N2O (325.04 ± 0.08 ppb), CO (52.4 ± 1.7 ppb), O3 (20.5 ± 1.1 ppb), acetaldehyde (190 ± 40 ppt), acetone (260 ± 30 ppt), dimethyl sulphide (50 ± 10 ppt), benzene (20 ± 10 ppt), toluene (30 ± 20 ppt), C8H10 aromatics (23 ± 6 ppt) and C9H12 aromatics (36 ± 7 ppt). The MUMBA site was frequently influenced by VOCs of biogenic origin from a nearby strip of forested parkland to the east due to the dominant north-easterly afternoon sea breeze. VOCs from the more distant densely forested escarpment to the west also impacted the site, especially during two days of extreme heat and strong westerly winds. The relative amounts of different biogenic VOCs observed for these two biomes differed, with much larger increases of isoprene than of monoterpenes or methanol during the hot westerly winds from the escarpment than with cooler winds from the east. However, whether this was due to different vegetation types or was solely the result of the extreme temperatures is not entirely clear. We conclude that the clean marine air and biogenic signatures measured during the MUMBA campaign provide useful information about the typical abundance of several key VOCs and can be used to constrain chemical transport model simulations of the atmosphere in this poorly sampled region of the world. © 2019 The Authors
- ItemIn-situ measurements of the stable isotopic composition of atmospheric water vapour using FTIR spectroscopy(Université Pierre et Marie Curie, 2010-04-27) Parkes, SD; Griffith, DWT; Williams, AG; Element, A; Chambers, SD; McCabe, MFThe stable isotopic composition of atmospheric water vapour is related to the hydrological processes that occur along the back trajectory of an air mass, including evaporation at the moisture source, atmospheric mixing and precipitation. Thus, by collecting continuous measurements of the stable isotopes in water vapour a record of the hydrological history of air passing a site can be compiled. To collect such a record a FTIR instrument capable of making real‐time in‐situ measurements of the stable isotopes in water vapour has been developed. The instrument has been deployed at a site near Sydney, Australia for approximately 18 months. During this time we have shown that the FTIR instrument compares well with laser based analysers that are capable of making similar real‐time measurements. In addition to the comparison between the different analysers, we have been investigating some of the large signals that are observed in the time series of isotopic measurements. The analysis of the dataset indicates that the lowest isotope values are generally associated with cold fronts that pass over the South East of the Australian Continent and then over the Sydney region. When a cold front passes over or near the measurement site, the deuterium isotope value can be observed to change by up to 100 per mille within the space of a few hours. In addition, cold frontal passages with contrasting moisture source and precipitation histories exhibit systematic differences in water vapour stable isotope signals as they pass over Sydney. On the other hand, higher and more slowly changing isotope values are generally associated with anticyclonic conditions. The study shows that for our site the variations in the stable isotope values are strongly influenced by the hydrological history of air parcels at a synoptic scale.
- ItemMeasured deuterium in water vapour concentration does not improve the constraint on the partitioning of evapotranspiration in a tall forest canopy, as estimated using a soil vegetation atmosphere transfer model(Elsevier, 2011-06-15) Haverd, V; Cuntz, M; Griffith, DWT; Keitel, C; Tadros, CV; Twining, JRPartitioning the evapotanspiration (ET) flux in a forest into its component fluxes is important for understanding the water and carbon budgets of the ecosystem. We use non-linear parameter estimation to determine the vertical profile of the Lagrangian timescale (T(L)) and partitioning of ET that simultaneously optimise agreement between modelled and measured vertical profiles of temperature, water vapour, carbon dioxide concentrations, and deuterated water vapour for a two-week period in November 2006. High precision real-time trace gas measurements were obtained by FTIR spectroscopy. Modelled temperature and concentration profiles are generated using a Lagrangian dispersion theory combined with source/sink distributions of HDO, H(2)O, sensible heat, and CO(2). These distributions are derived from an isotopically enabled multilayer Soil Vegetation Atmospheric Transfer (SVAT) model subject to multiple constraints. The soil component of the model was tested in isolation using measured deuterium content of soil chamber evaporate, while the leaf component was tested using isotopic analyses of leaf and xylem water, combined with leaf-level gas exchange measurements. Optimisation of T(L) and the partition of ET was performed twice: once using only temperature, H(2)O and CO(2) profiles and a second time including HDO as well. The modelled vertical concentration profiles resulting from inclusion of HDO in the cost function demonstrate our ability to make consistent estimates of both the scalar source distributions and the deuterium content of the water vapour sources. However, introducing measurements of deuterium in water vapour does not significantly alter resulting estimates of normalised T(L) (0.4 +/- 0.1 at canopy top) and the partition of ET(85 +/- 2% transpiration), suggesting that the additional data and modelling required to use deuterium are not warranted for the purpose of partitioning ET using the framework presented here. Crown Copyright (C) 2011 Published by Elsevier B.V.
- ItemThe MUMBA campaign: measurements of urban, marine and biogenic air(Copernicus Publications, 2017-06-06) Paton-Walsh, C; Guérette, ÉA; Kubistin, D; Humphries, R; Wilson, SR; Dominick, D; Galbally, IE; Buchholz, R; Bhujel, M; Chambers, SD; Cheng, M; Cope, M; Davy, P; Emmerson, K; Griffith, DWT; Griffiths, AD; Keywood, MD; Lawson, S; Molloy, SB; Rea, G; Selleck, PW; Shi, X; Simmons, J; Velazco, VThe Measurements of Urban, Marine and Biogenic Air (MUMBA) campaign took place in Wollongong, New South Wales (a small coastal city approximately 80 km south of Sydney, Australia) from 21 December 2012 to 15 February 2013. Like many Australian cities, Wollongong is surrounded by dense eucalyptus forest, so the urban airshed is heavily influenced by biogenic emissions. Instruments were deployed during MUMBA to measure the gaseous and aerosol composition of the atmosphere with the aim of providing a detailed characterisation of the complex environment of the ocean–forest–urban interface that could be used to test the skill of atmospheric models. The gases measured included ozone, oxides of nitrogen, carbon monoxide, carbon dioxide, methane and many of the most abundant volatile organic compounds. The aerosol characterisation included total particle counts above 3 nm, total cloud condensation nuclei counts, mass concentration, number concentration size distribution, aerosol chemical analyses and elemental analysis. The campaign captured varied meteorological conditions, including two extreme heat events, providing a potentially valuable test for models of future air quality in a warmer climate. There was also an episode when the site sampled clean marine air for many hours, providing a useful additional measure of the background concentrations of these trace gases within this poorly sampled region of the globe. In this paper we describe the campaign, the meteorology and the resulting observations of atmospheric composition in general terms in order to equip the reader with a sufficient understanding of the Wollongong regional influences to use the MUMBA datasets as a case study for testing a chemical transport model. © Author(s) 2017.
- ItemRadon tracer flux measurements of CO2, N2O and CH4 at Wagga Wagga: OASIS revisited?(Australian Government Bureau of Meteorology, 2017-11-12) Griffith, DWT; Wilson, SR; Griffiths, AD; Chambers, SD; Williams, AG; Werczynski, S; Sisoutham, O; Howitt, JA; Reardon, D; Leuning, RVertical profiles and suitably-conditioned surface time histories of the natural radioactive noble gas radon-222 (radon) have long been demonstrated to be useful as quantitative indicators of diurnal- to synoptic-scale mixing processes within the continental lower troposphere. Radon’s well-characterised and slowly-varying source function over (ice-free)terrestrial surfaces, together with its short half-life of 3.8 days, makes it a particularly suitable passive scalar for the evaluation of boundary layer and convective mixing parameterisation schemes in a range of regional and global climate and pollution transport models. We provide a brief overview of ANSTO measurement programs using radon to characterise vertical mixing in the lower atmosphere, together with examples of their applications in modelling and pollution studies. We then present preliminary results from recent field campaigns collecting high resolution vertical radon profiles in the terrestrial boundary layer over rural New South Wales, using a radon sampler mounted on an instrumented motor-glider. The flights were conducted in the lowest 1000m of the atmosphere and, together with simultaneous ground-based and tower measurements, document the dispersion of radon emissions accumulated below the nocturnal stable inversion into the developing daytime convective boundary layer during the important morning transition period.
- ItemSeasonal total methane depletion in limestone caves(Springer Nature, 2017-08-16) Waring, CL; Hankin, SI; Griffith, DWT; Kertesz, MA; Kobylski, V; Wilson, NL; Coleman, NV; Kettlewell, G; Zlot, R; Bosse, M; Bell, GMethane concentration in caves is commonly much lower than the external atmosphere, yet the cave CH4 depletion causal mechanism is contested and dynamic links to external diurnal and seasonal temperature cycles unknown. Here, we report a continuous 3-year record of cave methane and other trace gases in Jenolan Caves, Australia which shows a seasonal cycle of extreme CH4 depletion, from ambient ~1,775 ppb to near zero during summer and to ~800 ppb in winter. Methanotrophic bacteria, some newly-discovered, rapidly consume methane on cave surfaces and in external karst soils with lifetimes in the cave of a few hours. Extreme bacterial selection due to the absence of alternate carbon sources for growth in the cave environment has resulted in an extremely high proportion 2–12% of methanotrophs in the total bacteria present. Unexpected seasonal bias in our cave CH4 depletion record is explained by a three-step process involving methanotrophy in aerobic karst soil above the cave, summer transport of soil-gas into the cave through epikarst, followed by further cave CH4 depletion. Disentangling cause and effect of cave gas variations by tracing sources and sinks has identified seasonal speleothem growth bias, with implied palaeo-climate record bias. © 2017, The Author(s)
- ItemUpdate on the MUMBA campaign: measurements of urban, marine and biogenic air(Atmospheric Composition & Chemistry Observations & Modelling Conference, 2014-09-22) Paton-Walsh, C; Guérette, ÉA; Rea, G; Kubistin, D; Humphries, R; Wilson, SR; Griffith, DWT; Buchholz, R; Velazco, V; Shi, X; Galbally, IE; Keywood, MD; Lawson, S; Selleck, PW; Cheng, M; Molloy, SB; Bhujel, M; Griffiths, AD; Chambers, SD; Davy, PThe Measurements of Urban, Marine and Biogenic Air (MUMBA) campaign took place in Wollongong, New South Wales (a small coastal city approximately 80 km south of Sydney, Australia), from 21st December 2012 to 15th February 2013. Like many Australian cities, Wollongong is surrounded by dense eucalyptus forest and so the urban air-shed is heavily influenced by biogenic emissions. Instruments were deployed during MUMBA to measure the gaseous and aerosol composition of the atmosphere with the aim of providing a detailed characterisation of the complex environment of the ocean/forest/urban interface that could be used to test the skill of atmospheric models. Gases measured included ozone, oxides of nitrogen, carbon monoxide, carbon dioxide, methane and many of the most abundant volatile organic compounds. Aerosol characterisation included total particle counts above 3 nm, total cloud condensation nuclei counts; mass concentration, number concentration size distribution, aerosol chemical analyses and elemental analysis. The campaign captured varied meteorological conditions, including two extreme heat events, providing a potentially valuable test for models of future air quality in a warmer climate. There was also an episode when the site sampled clean marine air for many hours, providing a useful additional measure of background concentrations of these trace gases within this poorly sampled region of the globe. In this paper we describe the campaign, the meteorology and the resulting observations of atmospheric composition in general terms, in order to equip the reader with sufficient understanding of the Wollongong regional influences to use the MUMBA datasets as a case study for testing a chemical transport model. The data is available from PANGAEA (see https://doi.pangaea.de/10.1594/PANGAEA.871982).