Browsing by Author "Keywood, MD"

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    40 years of atmospheric composition observations and research at Cape Grim – an overview
    (Australian Meteorological & Oceanographic Society, 2016-02-08) Krummel, PB; Keywood, MD; Fraser, PJ; Galbally, IE; Steele, PL; Lawson, S; van der Schoot, MV; Wilson, SR; Williams, AG; Cleland, S
    In 2016, the Cape Grim station located at the north-west tip of Tasmania, will celebrate 40 years of continuous operation. Commencing operations in 1976, and in its current facilities since 1981, the Baseline Air Pollution Station at Cape Grim is Australia’s contribution to international efforts for monitoring the global background atmosphere for trends due to human activities and natural variability. It is one of the three premier stations in the Global Atmosphere Watch (GAW) network of the World Meteorological Organization (WMO). Cape Grim observations thereby contribute very significantly to the GAW programme, and research outputs are published in peer-reviewed international journals of the highest quality, are very frequently cited, and feed into the international/global assessments, for example the IPCC. Cape Grim’s essential purpose has not changed since the program’s inception in 1976. National and global concern that human activity is having an impact on the composition of the global (and regional) atmosphere requires that the changes be observed and understood. Initially, this was the main focus, whereas now the data are also used for prediction, to guide development of remedial policies, and to verify the effectiveness of global mitigation actions. The critical, but too often unrecognised role of precise in-situ atmospheric observation programs underpinning our current understanding of atmospheric processes and ability to model future climate, is well summarised in a commentary in Nature, titled “Cinderella science” (Nature 450, p789, 2007). The Cape Grim station is operated and funded by the Aust. Bureau of Meteorology, with the Cape Grim Science Program jointly supervised by CSIRO, the Bureau of Met., Univ. of Wollongong and ANSTO. This presentation will give an overview of the past and present measurement programs at the station, show some of the iconic long-term datasets, and summarise some of the science highlights and impacts from the past 40 years.
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    Aerosol iron solubility: comparison between the Australian subtropics and Southern ocean
    (Bureau of Meteorology and CSIRO Oceans and Atmosphere Flagship, 2014-11) Winton, VHL; Edwards, R; Bowie, A; Chambers, SD; Keywood, MD; Werczynski, S; Williams, AG
    Past changes in the atmospheric deposition of soluble, or bioavailable, trace metals to high nutrient low chlorophyll (HNLC) and nitrogen replete tropical waters have been shown to modulate primary production, atmospheric CO2, and global climate. The deposition of soluble trace metals can also trigger toxic algal blooms, which impact Australia’s fisheries and coral reefs. An understanding of the sources (e.g. mineral dust and biomass emissions) and geochemistry of soluble trace metals in atmospheric aerosols is critical for determining the impact of trace metal deposition on ocean fertility in the past and the future. However, to date no trace metal solubility data exists for biomass emissions from Australian fires and there are very few estimates of soluble trace metal aerosols entering the Southern Ocean. Trace metal clean aerosols were collected during the early‐late dry season experiment at Gunn Point, Northern Territory to investigate the trace metal aerosol solubility associated with biomass burning. Previous studies have suggested that mineral dust is the dominant source of trace metal aerosol. However, mineral dust is relatively insoluble and a significant fraction of soluble trace metals in the atmosphere could originate from biomass burning rather than mineral dust. Here we use the combination of soluble aerosol chemistry, back trajectories and diurnal and advective radon components to identify trace metal source regions throughout the campaign duration. We compare aerosol iron solubility at Gunn Point in the subtropics, where biomass burning can dominate the aerosol load in the dry season, to iron solubility in baseline air at Cape Grim which is representative of the Southern Hemisphere background. In doing this we highlight the importance of aerosol source at different latitudes for the solubility and bioavailability of trace metals.
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    The citical role of observations in developing numerical representations of ice nucleating particles for southern ocean mixed phased clouds
    (American Meterological Society, 2020-01-31) McCluskey, CS; DeMott, PJ; Hill, TCJ; Kreidenweis, SM; Ovadnevaite, J; Rinaldi, M; Atkinson, J; Belosi, F; Ceburnis, D; Marullo, S; Lohmann, U; Kanji, ZA; O'Dowd, C; Humphries, R; Rauker, AM; Moreau, S; Strutton, PG; Chambers, SD; Williams, AG; McRobert, I; Ward, J; Keywood, MD; Harnwell, J; Pronsonby, W; Loh, Z; Krummell, P; Protat, A; Gettelman, A; Bardeen, CG; Twohy, CH; MA, PL; Burrows, SM
    The abundance of supercooled liquid clouds over the remote Southern Ocean (SO) region challenges the aerosol-cloud microphysical interactions that are currently represented in global climate models. In particular, most global climate models simulate SO clouds that are over-glaciated compared to satellite observations, leading to large radiative biases. Primary ice formation initiated by atmospheric ice nucleating particles (INPs) is a critical process in cloud glaciation and is augmented by additional processes, such as secondary ice production. Due to extremely high winds and large distances from land, the INP sources are likely dominated by locally produced sea spray aerosol (SSA) and long-range transported terrestrial aerosol (e.g., dust and pollution). However, a dearth of aerosol and INP observations in the remote SO have limited our ability to advance numerical representations of freezing processes until recent years. In this study, we demonstrate ways in which recent INP observations have improved our understanding of SO INP populations and how modeling studies can aid in developing hypotheses that can be tested by future observational studies. Coastal and ship observations were used to 1) characterize remote INP populations and 2) develop and test numerical representations of INPs relevant for remote oceanic regions. These observations revealed that INPs associated with SSA are up to a factor of 1000 less ice nucleation active compared to mineral dust. Extremely low INP concentrations observed over the SO support the prevalence of supercooled liquid clouds known to dominate the SO region. In a series of nudged simulations with the Community Earth System Model, Versions 1 and 2, we demonstrated that observed INP number concentrations in the marine boundary layer are successfully predicted using an approach that considers only SSA and dust INPs. This predictive tool was further used to estimate INP populations at higher altitudes over the SO study region, revealing that while SSA dominates the INP population below 3-5 km, mineral dust INPs may be critical for INP populations present above 5 km. Finally, an evaluation of model-estimated INPs present at higher altitudes using recent airborne measurements of INPs from the 2018 Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Study will be presented.
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    Composition 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, SR
    Volatile 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
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    Comprehensive aerosol and gas data set from the Sydney Particle Study
    (Copernicus Publications, 2019-12-02) Keywood, MD; Selleck, PW; Reisen, F; Cohen, DD; Chambers, SD; Cheng, M; Cope, M; Crumeyrolle, S; Dunne, E; Emmerson, K; Fedele, R; Galbally, IE; Gillett, R; Griffiths, AD; Guerette, EA; Harnwell, J; Humphries, R; Lawson, S; Miljevic, B; Molloy, SB; Powell, J; Simmons, J; Ristovksi, Z; Ward, J
    The Sydney Particle Study involved the comprehensive measurement of meteorology, particles and gases at a location in western Sydney during February–March 2011 and April–May 2012. The aim of this study was to increase scientific understanding of particle formation and transformations in the Sydney airshed. In this paper we describe the methods used to collect and analyse particle and gaseous samples, as well as the methods employed for the continuous measurement of particle concentrations, particle microphysical properties, and gaseous concentrations. This paper also provides a description of the data collected and is a metadata record for the data sets published in Keywood et al. (2016a, https://doi.org/10.4225/08/57903B83D6A5D) and Keywood et al. (2016b, https://doi.org/10.4225/08/5791B5528BD63). © Author(s) 2019. This work is distributed under the Creative Commons Attribution 4.0 Licence.
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    Investigation of OC and EC fractions of aerosol samples in Sydney area by radiocarbon analysis
    (Australian Nuclear Science and Technology Organisation, 2021-11-17) Yang, B; Keywood, MD; Reisen, F; Smith, AM; Levchenko, VA
    Secondary Organic Aerosols (SOA) can be a major component of atmospheric PM.2.5 pollution, emitted from natural and anthropogenic sources. SOA is formed by the oxidation of volatile organic compounds (VOC) which have biogenic and anthropogenic sources. Measurement of the radiocarbon activity of SOA allows to discriminate between these sources, as biogenic sources have a near-modern activity and anthropogenic sources are generally depleted in ¹⁴ C. As part of the Sydney Particle Study [1,2], aerosol samples were collected on quartz filters using a high volume sampler fitted with a PM2.5 size selective inlet during the summer months of 2011 and autumn months of 2012. In order to estimate the apportionment of the SOA sources, we measured the radiocarbon content of organic carbon (OC) and elemental carbon (EC) fractions, using the novel method described below. We combusted strips (90 × 35 mm) of the quartz filters strip inside a quartz tube filled with high purity oxygen at ~300 mbar at 375°C to collect the OC fraction and then at 780°C to collect the EC fraction. CO₂ gas produced during each combustion was collected in a cold trap at -170°C, volumetrically measured and transferred into a Micro Conventional Furnaces (MCF) [3] for graphitisation. This method was shown to be reproducible for EC and OC filter densities from the same filter. We processed 25 air filters in this way to produce 50 samples for Accelerator Mass Spectroscopy (AMS) measurement with an average of 58 μg carbon (range 10 μg to 220 μg). Our densities compared well with OC and EC densities obtained using a standard thermal desorption method at CSIRO [2]. We combined the measured radiocarbon activity with sophisticated chemical transport modelling, using the EC tracer method [4] to determine SOA. Levoglucosan was used as a tracer to allow for biomass burning events. Our results suggested that i) biogenic SOA comprised around 50% of the SOA in summer and autumn, ii) higher radiocarbon activities for OC are associated with higher SOA concentrations, supporting the model theory [1] that that biogenic VOCs are an important contributor to SOA in the Sydney airshed, iii) the formation of SOA involves both anthropogenic and biogenic VOC, iv) the lowest EC and OC radiocarbon activities were for summer mornings, indicating high fossil fuel carbon (i.e. vehicle emissions). Afternoons in summer and autumn displayed the highest ratios, indicating low fossil fuel carbon. © The Authors
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    Lower Hunter particle characterisation study - chemical speciation and positive matrix factorisation factor concentration data set
    (Office of Environment and Heritage and Environment Protection Authority, 2016-04-01) Hibberd, MF; Keywood, MD; Selleck, PW; Cohen, DD; Stelcer, E; Scrogie, Y; Chang, L
    The Lower Hunter Particle Characterisation Study was commissioned by the NSW Environment Protection Authority in 2013 to investigate the composition and major sources of particle pollution in the Lower Hunter. The study was conducted by scientists from the former Office of Environment and Heritage (OEH), CSIRO and the Australian Nuclear Science and Technology Organisation (ANSTO), with oversight from the NSW Ministry of Health, and completed in 2016. Focusing on very small particles, invisible to the human eye, which can be inhaled and can pass through the throat and nose and into the lungs, the study aimed to determine the composition and major sources of fine particles (PM2.5) and coarse particles (PM2.5-10). Fine particles were monitored at four sites, including two sites representative of regional population exposures (Newcastle, Beresfield) and two sites near the Port of Newcastle (Mayfield and Stockton). Coarse particles were monitored at Mayfield and Stockton, the two sites near the Port of Newcastle.
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    Lower Hunter particle characterisation study 1st progress report
    (Office of Environment and Heritage and Environment Protection Authority, 2014-07) Hibberd, MF; Keywood, MD; Cohen, DD; Stelcer, E; Scorgie, Y; Thompson, S; Rivett, K
    The Lower Hunter Particle Characterisation Study was commissioned by the NSW Environment Protection Authority in 2013 to investigate the composition and major sources of particle pollution in the Lower Hunter. The study was conducted by scientists from the former Office of Environment and Heritage (OEH), CSIRO and the Australian Nuclear Science and Technology Organisation (ANSTO), with oversight from the NSW Ministry of Health, and completed in 2016. Focusing on very small particles, invisible to the human eye, which can be inhaled and can pass through the throat and nose and into the lungs, the study aimed to determine the composition and major sources of fine particles (PM2.5) and coarse particles (PM2.5-10). Fine particles were monitored at four sites, including two sites representative of regional population exposures (Newcastle, Beresfield) and two sites near the Port of Newcastle (Mayfield and Stockton). Coarse particles were monitored at Mayfield and Stockton, the two sites near the Port of Newcastle.
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    Lower Hunter particle characterisation study 2nd progress report (Winter)
    (Office of Environment and Heritage and Environment Protection Authority, 2014-10-01) Hibberd, MF; Keywood, MD; Cohen, DD; Stelcer, E; Scoprgie, Y; Thompson, S
    The Lower Hunter Particle Characterisation Study was commissioned by the NSW Environment Protection Authority in 2013 to investigate the composition and major sources of particle pollution in the Lower Hunter. The study was conducted by scientists from the former Office of Environment and Heritage (OEH), CSIRO and the Australian Nuclear Science and Technology Organisation (ANSTO), with oversight from the NSW Ministry of Health, and completed in 2016. Focusing on very small particles, invisible to the human eye, which can be inhaled and can pass through the throat and nose and into the lungs, the study aimed to determine the composition and major sources of fine particles (PM2.5) and coarse particles (PM2.5-10). Fine particles were monitored at four sites, including two sites representative of regional population exposures (Newcastle, Beresfield) and two sites near the Port of Newcastle (Mayfield and Stockton). Coarse particles were monitored at Mayfield and Stockton, the two sites near the Port of Newcastle.
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    Lower Hunter particle characterisation study 3rd progress report (Spring)
    (Office of Environment and Heritage and Environment Protection Authority, 2015-01-01) Hibberd, MF; Keywood, MD; Cohen, DD; Stelcer, E; Scorgie, Y; Thompson, S
    The Lower Hunter Particle Characterisation Study was commissioned by the NSW Environment Protection Authority in 2013 to investigate the composition and major sources of particle pollution in the Lower Hunter. The study was conducted by scientists from the former Office of Environment and Heritage (OEH), CSIRO and the Australian Nuclear Science and Technology Organisation (ANSTO), with oversight from the NSW Ministry of Health, and completed in 2016. Focusing on very small particles, invisible to the human eye, which can be inhaled and can pass through the throat and nose and into the lungs, the study aimed to determine the composition and major sources of fine particles (PM2.5) and coarse particles (PM2.5-10). Fine particles were monitored at four sites, including two sites representative of regional population exposures (Newcastle, Beresfield) and two sites near the Port of Newcastle (Mayfield and Stockton). Coarse particles were monitored at Mayfield and Stockton, the two sites near the Port of Newcastle. © 2015 CSIRO and Office of Environment and Heritage
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    Lower Hunter particle characterisation study 4th progress report (Summer)
    (Office of Environment and Heritage and Environment Protection Authority, 2015-04) Hibberd, MF; Keywood, MD; Cohen, DD; Stelcer, E; Scrogie, Y; Thompson, S
    The Lower Hunter Particle Characterisation Study was commissioned by the NSW Environment Protection Authority in 2013 to investigate the composition and major sources of particle pollution in the Lower Hunter. The study was conducted by scientists from the former Office of Environment and Heritage (OEH), CSIRO and the Australian Nuclear Science and Technology Organisation (ANSTO), with oversight from the NSW Ministry of Health, and completed in 2016. Focusing on very small particles, invisible to the human eye, which can be inhaled and can pass through the throat and nose and into the lungs, the study aimed to determine the composition and major sources of fine particles (PM2.5) and coarse particles (PM2.5-10). Fine particles were monitored at four sites, including two sites representative of regional population exposures (Newcastle, Beresfield) and two sites near the Port of Newcastle (Mayfield and Stockton). Coarse particles were monitored at Mayfield and Stockton, the two sites near the Port of Newcastle.
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    Lower Hunter particle characterisation study appendices to the final report to the NSW Environment Protection Authority
    (Office of Environment and Heritage and Environment Protection Authority, 2016-04-01) Hibberd, MF; Keywood, MD; Selleck, PW; Cohen, DD; Stecler, E; Scorgie, Y; Chang, L
    The Lower Hunter Particle Characterisation Study was commissioned by the NSW Environment Protection Authority in 2013 to investigate the composition and major sources of particle pollution in the Lower Hunter. The study was conducted by scientists from the former Office of Environment and Heritage (OEH), CSIRO and the Australian Nuclear Science and Technology Organisation (ANSTO), with oversight from the NSW Ministry of Health, and completed in 2016. Focusing on very small particles, invisible to the human eye, which can be inhaled and can pass through the throat and nose and into the lungs, the study aimed to determine the composition and major sources of fine particles (PM2.5) and coarse particles (PM2.5-10). Fine particles were monitored at four sites, including two sites representative of regional population exposures (Newcastle, Beresfield) and two sites near the Port of Newcastle (Mayfield and Stockton). Coarse particles were monitored at Mayfield and Stockton, the two sites near the Port of Newcastle.
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    Lower Hunter particle characterisation study Final Report to the NSW Environment Protection Authority
    (Office of Environment and Heritage and Environment Protection Authority, 2016-04-01) Hibberd, MF; Keywood, MD; Selleck, PW; Cohen, DD; Stelcer, E; Scorgie, Y; Chang, L
    The Lower Hunter Particle Characterisation Study (LHPCS) provides details about the composition and major sources of PM2.5 (fine airborne particles)and PM2.5-10(coarse airborne particles). Measurements were made for one year from March 2014 to February 2015 at two air quality monitoring stations representative of regional population exposures (Newcastle and Beresfield) and two stations near the Port of Newcastle (Mayfield and Stockton). Annual average PM2.5 concentrations were very similar at Newcastle, Mayfield and Beresfield (6.4–6.7 μg m-3) but about 40% higher at Stockton (9.1 μg m-3). The higher levels at Stockton were mainly due to both more sea salt and to the primary ammonium nitrate, which was only detected at Stockton. The ammonium nitrate, which contributed on average 19% of the PM2.5 mass (and ~40% in winter), was identified as very likely to be due to primary emissions from Orica’s ammonium nitrate manufacturing facility on Kooragang Island. Other than the ammonium nitrate, PM2.5 composition and sources were found to be fairly similar across the four sites. Key results on the sources and their contributions are: fresh sea salt particles: 24% at Newcastle, decreasing to 13% at Beresfield; pollutant-aged sea salt: ~23% at all sites; this is sea salt reacted with industrial, commercial, road and non-road transport emissions from local and regional sources; wood smoke: 15% at Beresfield, decreasing to 6% at Stockton; secondary ammonium sulfate: ~10% at all sites; soil dust: ~10% at all sites; vehicles: ~10% at three sites, but only 5% at Stockton; industry factors: ~12% at three sites but 24% at Stockton; mixed shipping/industry: ~3% at all sites; nitrate: 19% ammonium nitrate at Stockton and secondary nitrate at other sites (6-11%). On an annual average basis, there is an approximately 50:50 split between primary and secondary particles at three sites (Newcastle, Beresfield and Mayfield) and a 65:35 split at Stockton because of the significant contribution from the primary ammonium nitrate. PM2.5-10 composition and sources were only determined at the stations near the Port of Newcastle. The 2½ times higher annual average PM2.5-10 concentration at Stockton (21.5 μg m-3) than at Mayfield (8.3 μg m-3) was found to be mainly due to a much higher contribution by fresh sea salt particles at Stockton. The PM2.5-10 factors and their contributions were identified as:  fresh sea salt: 13.6 μg m-3 at Stockton, 3.3 μg m-3 at Mayfield  industry plus pollutant-aged sea salt: 2.4 μg m-3 at both sites  light-absorbing carbon: 2.2 μg m-3 at Stockton, 0.9 μg m-3 at Mayfield  soil: 2.3 μg m-3 at Stockton, 1.2 μg m-3 at Mayfield  bioaerosol: 1.1 μg m-3 at Stockton, 0.5 μg m-3 at Mayfield. Most PM2.5-10 particles are primary particles or physical combinations of primary emissions, but there is evidence of chemical reactions in the pollutant-aged sea salt factor. Coal particles could contribute up to 10% of PM2.5-10 particles. Further investigations are needed to clarify the contribution of coal.
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    Marine productivity and synoptic meteorology drive summer-time variability in Southern Ocean aerosols
    (Copernicus Publications, 2020-07-10) Alroe, J; Cravigan, LT; Miljevic, B; Johnson, GR; Selleck, PW; Humphries, RS; Keywood, MD; Chambers, SD; Williams, AG; Ristovski, ZD
    Cloud–radiation interactions over the Southern Ocean are not well constrained in climate models, in part due to uncertainties in the sources, concentrations, and cloud-forming potential of aerosol in this region. To date, most studies in this region have reported measurements from fixed terrestrial stations or a limited set of instrumentation and often present findings as broad seasonal or latitudinal trends. Here, we present an extensive set of aerosol and meteorological observations obtained during an austral summer cruise across the full width of the Southern Ocean south of Australia. Three episodes of continental-influenced air masses were identified, including an apparent transition between the Ferrel atmospheric cell and the polar cell at approximately 64∘ S, and accompanied by the highest median cloud condensation nuclei (CCN) concentrations, at 252 cm−3. During the other two episodes, synoptic-scale weather patterns diverted air masses across distances greater than 1000 km from the Australian and Antarctic coastlines, respectively, indicating that a large proportion of the Southern Ocean may be periodically influenced by continental air masses. In all three cases, a highly cloud-active accumulation mode dominated the size distribution, with up to 93 % of the total number concentration activating as CCN. Frequent cyclonic weather conditions were observed at high latitudes and the associated strong wind speeds led to predictions of high concentrations of sea spray aerosol. However, these modelled concentrations were not achieved due to increased aerosol scavenging rates from precipitation and convective transport into the free troposphere, which decoupled the air mass from the sea spray flux at the ocean surface. CCN concentrations were more strongly impacted by high concentrations of large-diameter Aitken mode aerosol in air masses which passed over regions of elevated marine biological productivity, potentially contributing up to 56 % of the cloud condensation nuclei concentration. Weather systems were vital for aerosol growth in biologically influenced air masses and in their absence ultrafine aerosol diameters were less than 30 nm. These results demonstrate that air mass meteorological history must be considered when modelling sea spray concentrations and highlight the potential importance of sub-grid-scale variability when modelling atmospheric conditions in the remote Southern Ocean. © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License.
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    The 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, V
    The 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.
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    A new pilot Australian tropical atmospheric research station (ATARS)
    (CSIRO Marine and Atmospheric Research, 2014-01-01) van der Schoot, MV; Fraser, PJ; Krummel, PB; Spencer, DA; Loh, ZM; Langenfelds, RL; Steele, LP; Gregory, RL; Meyer, CP; Keywood, MD; Lawson, S; Fedele, R; Atkinson, B; Klau, D; Zahorowski, W
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    Optical, physical and chemical characteristics of Australian desert dust aerosols: results from a field experiment
    (European Geosciences Union, 2009-11-25) Radhi, M; Box, A; Box, GP; Mitchell, RM; Cohen, DD; Stelcer, E; Keywood, MD
    Mineral dust is one of the major components of the world's aerosol mix, having a number of impacts within the Earth system. However, the climate forcing impact of mineral dust is currently poorly constrained, with even its sign uncertain. As Australian deserts are more reddish than those in the northern hemisphere, it is important to better understand the physical, chemical and optical properties of this important aerosol. We have investigated the properties of Australian desert dust at a site in SW Queensland, which is strongly influenced by both dust and biomass burning aerosol. Three years of ground-based monitoring of spectral optical thickness has provided a statistical picture of gross aerosol properties. In November 2006 we undertook a field campaign which collected 4 sets of size-resolved aerosol samples for laboratory analysis – both ion beam analysis and ion chromatography. © 2009, European Geosciences Union
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    Physical, chemical and optical properties of Australian desert dust: a multiple analysis from several sites
    (3rd International Workshop on Mineral Dust, 2008-09) Radhi, M; Box, MA; Box, GP; Mitchell, RM; Keywood, MD; French, D; Cohen, DD; Stelcer, E
    Australian dust aerosol was sampled at two desert locations, Birdsville (25.54 S, 139.20 E) and Muloorina (29.14 S, 137.64 E), using a 12-stage MOUDI sampler. Backgound TSP levels were 15.8 ± 3 μg/m3 at Birdsville, and 244 ± 10 μg/m3 at Muloorina. Ion beam analysis shows that the following elements are dominant at both sites: Na, Al, Si, Cl, K, Ca, Ti and Fe. Sulphur is the only pollutant element that occurred in the Muloorina analysis due to local vegetation burning. Weather conditions during sampling at Birdsville were classified as non-dusty to weak dust. At Muloorina we had different weather conditions: non-dust, weak dust and dust storm. The concentrations of the element loading in the atmosphere varied with weather conditions. The mass ratio of the other elements to Al also varied with the weather conditions. For both sites Fe occurred in fine and coarse size ranges, appearing strongly in the size range 1.8 to 10 μm in all events. The Fe/Al mass ratio was 1.97, 2.5, 0.96 and 1.02 for non dust, weak dust and north and south dust storm respectively at Muloorina, while at Birdsville the value was in the range 0.45 to 0.65, indicating Muloorina is rich in Fe. Both Na and Cl demonstrated a good correlation with Al as Australian desert dust also contains a mixture of salts from dry saline lakes. Selected filters are currently undergoing electron microscopy analysis in order to determine the mineralogical content, especially hematite vs. goethite. The monthly mean of the aerosol optical depth at Birdsville shows maximum values during summer (Feb. 0.06 ± 0.05) and spring (Oct. 0.11 ± 0.05), and minimum values in June (0.02 ± 0.001). The Ångström exponent was low (suggesting coarse particles) during summer and spring. The relationship between AOD and Ångström exponent shows a good pattern of decreasing α with increasing AOD, indicating the effects of dust particles.
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    Size-resolved mass and chemical properties of dust aerosols from Australia's Lake Eyre Basin
    (Elsevier, 2010-09) Radhi, M; Box, MA; Box, GP; Mitchell, RM; Cohen, DD; Stelcer, E; Keywood, MD
    Australia is the dominant mineral dust source in the southern hemisphere, yet the physical, chemical and optical properties of Australian dust aerosol are presently poorly understood. We have investigated the properties of Australian aerosol at a site near Lake Eyre in central Australia, which is strongly influenced by mineral dust. During a field campaign in November 2007 we collected eight sets of size-resolved aerosol samples for laboratory analysis: six during quiescent conditions, and two during dust storms. Ion Beam Analysis was used to determine the elemental composition of all filter samples. Scatter plots showed that Fe, Al and Ti were well correlated with Si, and hence soil-derived. The Fe/Si ratio was consistently higher than the global crustal average, confirming that Australian dusts are comparatively rich in Fe. Scatter plots for Na and Cl against Si showed clear evidence of a second aerosol population, associated with maritime advection. Profiles of water soluble ions for two sample sets, showed the importance of marine influences on both the fine and coarse modes, as well as the presence of organic acids. Estimates of the mass fraction of NaCl in our samples suggest that, for quiescent days, roughly 0.5% of the sample mass was NaCl. © 2010, Elsevier Ltd.
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    Sources of particulate matter in the Hunter Valley, New South Wales, Australia
    (Multidisciplinary Digital Publishing Institute (MDPI), 2019-12-18) Keywood, MD; Hibberd, MF; Selleck, PW; Desservettaz, M; Cohen, DD; Stelcer, E; Atanacio, AJ; Scorgie, Y; Chang, L
    Exposure to particulate matter results in adverse health outcomes, especially in sensitive members of the community. Many communities that co-exist with industry are concerned about the perceived impact of emissions from that industry on their health. Such concerns have resulted in two studies in the Hunter Valley of New South Wales, Australia. The chemical composition of samples of particulate matter, collected over two 12-month sampling periods (2012 and 2014–2015) at six sites in the Hunter Valley and across two size fractions (PM2.5 and PM2.5–10) were input to a receptor model to determine the source of particulate matter influencing particle composition at the sites. Fourteen factors were found to contribute to particle mass. Of these, three source profiles common to all sites, size fractions, and sampling periods were sea salt, industry-aged sea salt and soil. Four source profiles were common across all sites for PM2.5 including secondary sulphate, secondary nitrate, mixed industry/vehicles, and woodsmoke. One source profile (other biomass smoke) was only identified in PM2.5 at Singleton and Muswellbrook, two source profiles (mixed industry/shipping and vehicles) were only identified in PM2.5 at Newcastle, Beresfield, Mayfield, and Stockton, and one source (primary nitrate) was only identified at Stockton in PM2.5. Three sources (bioaerosol, light absorbing particles (coal dust), and industry) were only identified in the PM2.5–10 size fraction at Mayfield and Stockton. The contribution of the soil factor to PM2.5 mass was consistent across the sites, while the fresh sea salt factor decreased with distance from the coast from 23% at Stockton to 3% at Muswellbrook, and smoke increased with distance from the coast. Primary industry was greatest at Stockton (due to the influence of ammonium nitrate emitted from a prilling tower) and lowest inland at Muswellbrook. In general, primary emissions across the sites accounted for 30% of the industry sources. The largest contribution to PM2.5 was from secondary sources at all sites except at Muswellbrook, where woodsmoke and industry sources each made an equal contribution of 40%. In general, secondary reactions accounted for approximately 70% of the industry source, although at Stockton, with the presence of the prilling tower, this split was 50% primary and 50% secondary and at Muswellbrook, the split was 20% primary and 80% secondary. These findings add to the evidence base required to inform policies and programs that will improve air quality in the Hunter Valley. © 2019 by the Authors