Characterisation of LA-ICP-MS and receptor modelling to measure, speciate and source apportion particulate matter

Adhitya Sutresna¹, Peter Rayner¹, Bence Paul¹, Estephany Marillo Sialer¹, Robyn Schofield¹, Andrew Bowie², Michal Strzelec², Maximilien Desservettaz³ 

1. School of Earth Sciences, The University of Melbourne, Parkville, Victoria, Australia
2. Institute of Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia
3. Centre for Atmospheric Chemistry, University of Wollongong, Wollongong, New South Wales, Australia

Particulate matter (PM) has been observed to produce negative health impacts in humans^1,2. However, these health impacts can vary depending on several factors, including their sources^3,4. One approach to source apportioning PM is to determine its elemental composition, which can then be used as data inputs for receptor models that can characterise distinct source fingerprints. This project aims to identify a protocol for conducting elemental analysis of PM using Laser Ablation Inductively-Coupled Plasma Mass Spectrometry (LA-ICP-MS), which can serve as a high-throughput, low-cost alternative to analytical techniques employed for this purpose. Data from this analysis is then processed through a combination of the factor analysis receptor model Positive Matrix Factorisation (PMF) and back trajectories to estimate the contributions of different sources of PM.

PM samples were collected from Garden Island, Western Australia between April and May 2018 and Parkville, Victoria between December 2018 and April 2019, with the former being PM_2.5 (as determined by Scanning Electron Microscope, SEM, analysis) and the latter being PM₁₀. Several Garden Island samples were also analysed using Acid Digestion ICP-MS, a reference method for speciating PM5, to validate the accuracy of LA-ICP-MS results. SEM was also used to identify spatial distributions of particles on sample papers, which was used to determine the ideal proportion of sample to be scanned to representatively detect the particles present. It was found that LA-ICP-MS analysis was able to reflect atmospheric conditions of the sampling periods. For example, high concentrations of marker elements (e.g. K, S) for smoke during bushfire events as well as a near 1:1 ratio between Na and Cl that reflects the PM produced by sea spray. Source apportionment using PMF resolved elemental ratios that distinguished different source profiles, while back trajectories correlated calculated source contributions with actual atmospheric transport conditions.

1. World Health Organisation. (2016). Ambient air pollution: A global assessment of exposure and burden of disease. Retrieved from http://apps.who.int/iris/bitstream/handle/10665/250141/9789241511353-eng.pdf?sequence=1
2. Organisation for Economic Co-operation and Development. (2014). The cost of air pollution: Health impacts of road transport. Retrieved from: http://www.oecd.org/env/the-cost-of-air-pollution-9789264210448-en.htm
3. Jalava, P. I., Salonen, R. O., Pennanen, A. S., Sillanpaa, M., Halinen, A. I., Happo, M. S., . . . Hirvonen, M. R. (2007). Heterogeneities in inflammatory and cytotoxic responses of RAW 264.7 macrophage cell line to urban air coarse, fine, and ultrafine particles from six European sampling campaigns. Inhalation Toxicology, 19(3), 213-225. doi:10.1080/08958370601067863
4. Pun, V. C., Yu, I. T. S., Ho, K. F., Qiu, H., Sun, Z. W., & Tian, L. W. (2014). Differential Effects of Source-Specific Particulate Matter on Emergency Hospitalizations for Ischemic Heart Disease in Hong Kong. Environmental Health Perspectives, 122(4), 391-396. doi:10.1289/ehp.1307213
5. Brown, R. J. C., Jarvis, K. E., Disch, B. A., Goddard, S. L., Adriaenssens, E., & Claeys, N. (2010). Comparison of ED-XRF and LA-ICP-MS with the European reference method of acid digestion-ICP-MS for the measurement of metals in ambient particulate matter. Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement, 9, 493-502. doi:10.1007/s00769-010-0668-7

Ocean-derived atmospheric volatile organic compounds (VOCs) during the Surface Ocean Aerosol Production (SOAP) voyage, South West Pacific Ocean

Sarah Lawson¹, Mike Harvey², Cliff Law² 

1. CSIRO Climate Science Centre, Aspendale
2. NIWA, Wellington, New Zealand

Biological process in the surface ocean may contribute significantly to the composition of the overlying atmosphere, though direct emission of bacteria, viruses and algal debris, and through emission of reactive volatile organic compounds (VOCs) including dimethyl sulfide. The SOAP (Surface Ocean Aerosol Production) voyage in February 2012 examined biological influences on aerosol production and chemical composition east of New Zealand, by targeting phytoplankton blooms along the Sub-Tropical Front along Chatham Rise in the South West Pacific. We present atmospheric concentrations of dimethyl sulfide (DMS), methanethiol (MeSH) and acetone in the atmosphere, measured continuously during the voyage using a Proton Transfer Reaction Mass Spectrometer.

DMS and MeSH atmospheric concentrations correlated throughout the voyage, and diurnal cycles of DMS and MeSH show similar behaviour with the lowest concentration in mid-afternoon, likely due to photochemical destruction. The DMS diurnal cycle shows similar behaviour to historical published DMS measurements at Cape Grim, Tasmania, but with higher concentrations (factor of 2-4 times higher). Acetone and DMS atmospheric concentrations correlated during Bloom 1 which had very high concentrations of water and atmospheric DMS.

Ocean sources of atmospheric DMS, MeSH and acetone are explored by correlating atmospheric measurements with seawater biogeochemical parameters. Finally, the MeSH sea-air flux during the voyage is estimated.

The Northern Territory Baseline Air Pollution Station (NT BAPS)  

Erin Dunne¹, Jason Ward¹, James Harnwell¹, Zoe Loh¹, Melita Keywood¹, Sylvester Werczynski², Grant Edwards³ 

1. CSIRO Climate Science Centre, Aspendale, VIC, Australia
2. ANSTO, Lucas Heights, NSW, Australia
3. Dept Environment & Geography, Macquarie University, North Ryde, NSW, Australia

NT BAPS, located at Gunn Point ~ 40km to the northeast of Darwin, is a regional station in the World Meteorological Organisation’s Global Atmospheric Watch (WMO GAW) Program along with Cape Grim, RV Investigator, Macquarie Is, Casey, Mawson, and Cape Ferguson which together provide key data on atmospheric composition and chemistry spanning the Southern Latitudes. Along with our partners at NT BAPS- BoM, ANSTO and Macquarie University- measurements of greenhouse gases, aerosols, reactive gases, mercury and radon have been collected since 2010 with expanded measurements occurring as part of focused field campaigns.

Savannah fires contribute significantly to global aerosol loading and consequently to the Earth’s radiative budget. Accurate modelling of the impact of these aerosols on climate is limited due to a lack of long-term observation records in the tropical savannah. Likewise, the inter-annual and decadal variability of methane remains poorly understood, principally due to a lack of observational data in the tropics, where biomass burning and wetland emissions are both large sources that alternate between the dry and wet seasons. Measurements of aerosols, methane and other GHGs in the tropics contributes to the data needed to answer key questions about global carbon accounting. This presentation will provide an overview of the measurement capability at NT BAPS, it's contribution to national observing programs, and current and future directions of the NT BAPS program.

Chellenges to homogenise historical radiosonde humidity data

Branislava Jovanovic¹, Robert Smalley¹, Chris Lucas², Steven Siems³, Bertrand Timbal⁴ 

1. Climate Monitoring and Prediction Section, Comunity Forecasts, Australian Bureau of Meteorology, Melbourne
2. Science for Services, Science and Innovation, Australian Bureau of Meteorology, Melbourne
3. School of Earth, Atmosphere and Environment, Monash University, Melbourne, Australia
4. Centre for Climate Research, National Environment Agency, Singapore

Water vapour plays a major role in the global climate. It is a potent and abundant greenhouse gas and has a strong effect on radiative transfer. It is a key component in the formation of clouds and precipitation and, through the associated latent heating, plays a key role in the transport of energy in the atmosphere. Given its importance, understanding its historical variability and evolution is crucial for understanding the present climate and estimating any future regional climate changes.

Observing water vapour in the free atmosphere is challenging, as absolute concentrations decrease rapidly with increasing altitude. Direct measurements of humidity are made by radiosondes and were historically subject to two reporting biases - warm and dry. Respectively these were caused by cold observations (when ambient air temperature below -40 °C) and dry observations (when relative humidity less than 20%) being reported as missing. Further, there are also measurement biases in the long-term record, caused by the introduction of new radiosonde or sensor types. These biases have a limiting effect on identifying any changes in global atmospheric water vapour. Hence, it is important to develop homogeneous records with the aim of gaining greater confidence in the results of the analysis.

To improve the homogeneity of the long-term data series, daily humidity data (represented as dew point temperature, DWPT) for the period starting in 1987 (i.e. after the Vaisala radiosondes were introduced) were removed if the ambient temperature was below -40 °C or the relative humidity below 20%. This was done based on the formula proposed for the WMO Hygrometer Intercomparison.

Preliminary results related to the development of the bias-corrected Australian monthly humidity data set are presented. Adjustments of the time series were determined using historical metadata and an objective statistical test for break-point detection.

Increasing hydrogen use: effects on global atmospheric chemistry

Matt Woodhouse¹, Steve White², Martin Cope¹, Anne Tibbett² 

1. CSIRO, Aspendale, VICTORIA, Australia
2. CSIRO, North Ryde

As the world comes to terms with its carbon addiction, an inevitable transition from burning of fossils fuels to other energy sources will occur. This transition will require new mechanisms to move and store energy, with one possibility being hydrogen. Increasing use of hydrogen as an energy vector will lead to additional release of hydrogen to the atmosphere due to the unintended release of hydrogen during its manufacture, transport, storage, and use. Possibilities for hydrogen use include shipping, land transport, electricity use and distribution.

The effect of increased concentrations of atmospheric H₂ (molecular hydrogen), NH₃ (ammonia) and CH₃OH (methanol) on atmospheric constituents, and subsequently climate, are not well quantified and may become significant as the hydrogen economy grows. Here, the ACCESS-UKCA global composition-climate model is used to simulate the impacts of increased fluxes (and hence increases in concentration) of NH₃ and CH₃OH on key climate-relevant atmospheric constituents such as OH (hydroxyl), and O₃ (ozone).

In ACCESS-UKCA, we find that a modest increase of emissions of NH₃ and CH₃OH results in regionally and locally significant increases in these species. The subsequent impacts on atmospheric oxidative capacity are globally negligible for the scenario tested, however there are locally significant differences. These local and regional effects may impact air quality, and merit further investigation.

One significant uncertainty is the size of the contribution that hydrogen will make to the energy mix in the future, both regionally and globally. Thus it is difficult to specify the changes in emissions that are necessary to conduct these kinds of simulations. This uncertainty is a fundamental constraint on our ability to understand the impact on atmospheric composition of a transition to a hydrogen-based economy.

Development of a next generation regional chemical transport model in Western Australia

Sean Lam¹ 

1. Department of Water and Environmental Regulation, Joondalup, WESTERN AUSTRALIA, Australia

The purpose of this project is to develop a state-of-the-art chemical transport model through the integration of a highly explicit representation of atmospheric chemistry and next generation of meteorological model. Critical to the development of this next generation regional chemical transport model will be the meteorological data, detailed emission data and selected chemical mechanism scheme. 

Department of Water and Environmental Regulation (DWER) has conducted numerous sensitivity analysis for Weather Research Forecast (WRF) model in the region. The recent update of Perth metropolitan emission inventory offers a great opportunity to incorporate a state-of-the art meteorological model with detailed emissions in the region. 

This project involves the development of the next-generation regional photochemical transport model that extends the highly explicit representation of the atmospheric chemistry beyond what is currently available. The construction of Common Representative Intermediates mechanism (CRImech) will involve an updated Master Chemical Mechanism (MCM) database and explicit atmospheric degradation scheme of new Volatile Organic Compounds (VOC) species, which are not included in the current version of CRImech. The modelled results will be evaluated and compared to long term observational data in the region.