Satellite-Based Land-Use Regression for Continental-Scale Long-Term Ambient PM2.5 Exposure Assessment in Australia.

Australia has relatively diverse sources and low concentrations of ambient fine particulate matter (<2.5 µm, PM2.5). Few comparable regions are available to evaluate the utility of continental-scale land-use regression (LUR) models including global geophysical estimates of PM2.5, derived by relating satellite-observed aerosol optical depth to ground-level PM2.5 ("SAT-PM2.5"). We aimed to determine the validity of such satellite-based LUR models for PM2.5 in Australia. We used global SAT-PM2.5 estimates (∼10 km grid) and local land-use predictors to develop four LUR models for year-2015 (two satellite-based, two nonsatellite-based). We evaluated model performance at 51 independent monitoring sites not used for model development. An LUR model that included the SAT-PM2.5 predictor variable (and six others) explained the most spatial variability in PM2.5 (adjusted R2 = 0.63, RMSE (µg/m3 [%]): 0.96 [14%]). Performance decreased modestly when evaluated (evaluation R2 = 0.52, RMSE: 1.15 [16%]). The evaluation R2 of the SAT-PM2.5 estimate alone was 0.26 (RMSE: 3.97 [56%]). SAT-PM2.5 estimates improved LUR model performance, while local land-use predictors increased the utility of global SAT-PM2.5 estimates, including enhanced characterization of within-city gradients. Our findings support the validity of continental-scale satellite-based LUR modeling for PM2.5 exposure assessment in Australia.

Baseline characterisation of source contributions to daily-integrated PM2.5 observations at Cape Grim using Radon-222.

We discuss 15 years (2000-2015) of daily-integrated PM2.5 samples from the Cape Grim Station. Ion beam analysis and positive matrix factorisation are used to identify six source-type fingerprints: fresh sea salt (57%); secondary sulfate (14%); smoke (13%); aged sea salt (12%); soil dust (2.4%); and industrial metals (1.5%). An existing hourly radon-only baseline selection technique is modified for use with the daily-integrated observations. Results were not significantly different for days on which >20 hours were below the baseline radon threshold compared with days when all 24 hours satisfied the baseline criteria. This relaxed daily baseline criteria increased the number of samples for analysis by almost a factor of two. Two radon baseline thresholds were tested: historic (100 mBq m-3), and revised (50 mBq m-3). Median aerosol concentrations were similar for both radon thresholds, but maximum values were higher for the 100 mBq m-3 threshold. Back trajectories indicated more interaction with southern Australia and the Antarctic coastline for air masses selected with the 100 mBq m-3 threshold. Radon-only baseline selection using the 50 mBq m-3 threshold was more selective of minimal terrestrial influence than a similar recent study using wind direction and back trajectories. The ratio of concentrations between terrestrial and baseline days for the primary sources soil, smoke and industrial metals was 3.4, 2.6, and 5.5, respectively. Seasonal cycles of soil dust had a summer maximum and winter minimum. Seasonal cycles of smoke were of similar amplitude for terrestrial and baseline events, but of completely different shape: peaking in autumn and spring for terrestrial events, compared to summer for baseline conditions. Seasonal cycles of industrial metals had a summer maximum and winter minimum. A significant fraction of the Cape Grim baseline smoke and industrial metal contributions appeared to be derived from long-term transport (>3 weeks since last terrestrial influence).

Chemical characterisation and source identification of atmospheric aerosols in the Snowy Mountains, south-eastern Australia.

Characterisation of atmospheric aerosols is of major importance for: climate, the hydrological cycle, human health and policymaking, biogeochemical and palaeo-climatological studies. In this study, the chemical composition and source apportionment of PM2.5 (particulate matter with aerodynamic diameters less than 2.5µm) at Yarrangobilly, in the Snowy Mountains, SE Australia are examined and quantified. A new aerosol monitoring network was deployed in June 2013 and aerosol samples collected during the period July 2013 to July 2017 were analysed for 22 trace elements and black carbon by ion beam analysis techniques. Positive matrix factorisation and back trajectory analysis and trajectory clustering methods were employed for source apportionment and to isolate source areas and air mass travel pathways, respectively. This study identified the mean atmospheric PM2.5 mass concentration for the study period was (3.3±2.5)µgm-3. It is shown that automobile (44.9±0.8)%, secondary sulfate (21.4±0.9)%, smoke (12.3±0.6)%, soil (11.3±0.5)% and aged sea salt (10.1±0.4)% were the five PM2.5 source types, each with its own distinctive trends. The automobile and smoke sources were ascribed to a significant local influence from the road network and bushfire and hazard reduction burns, respectively. Long-range transport are the dominant sources for secondary sulfate from coal-fired power stations, windblown soil from the inland saline regions of the Lake Eyre and Murray-Darling Basins, and aged sea salt from the Southern Ocean to the remote alpine study site. The impact of recent climate change was recognised, as elevated smoke and windblown soil events correlated with drought and El Niño periods. Finally, the overall implications including potential aerosol derived proxies for interpreting palaeo-archives are discussed. To our knowledge, this is the first long-term detailed temporal and spatial characterisation of PM2.5 aerosols for the region and provides a crucial dataset for a range of multidisciplinary research.

Trace metal content in inhalable particulate matter (PM2.5-10 and PM2.5) collected from historical mine waste deposits using a laboratory-based approach.

Mine wastes and tailings are considered hazardous to human health because of their potential to generate large quantities of highly toxic emissions of particulate matter (PM). Human exposure to As and other trace metals in PM may occur via inhalation of airborne particulates or through ingestion of contaminated dust. This study describes a laboratory-based method for extracting PM2.5-10 (coarse) and PM2.5 (fine) particles from As-rich mine waste samples collected from an historical gold mining region in regional, Victoria, Australia. We also report on the trace metal and metalloid content of the coarse and fine fraction, with an emphasis on As as an element of potential concern. Laser diffraction analysis showed that the proportions of coarse and fine particles in the bulk samples ranged between 3.4-26.6 and 0.6-7.6 %, respectively. Arsenic concentrations were greater in the fine fraction (1680-26,100 mg kg-1) compared with the coarse fraction (1210-22,000 mg kg-1), and Co, Fe, Mn, Ni, Sb and Zn were found to be present in the fine fraction at levels around twice those occurring in the coarse. These results are of particular concern given that fine particles can accumulate in the human respiratory system. Our study demonstrates that mine wastes may be an important source of metal-enriched PM for mining communities.

Mechanisms of murine cerebral malaria: Multimodal imaging of altered cerebral metabolism and protein oxidation at hemorrhage sites.

Using a multimodal biospectroscopic approach, we settle several long-standing controversies over the molecular mechanisms that lead to brain damage in cerebral malaria, which is a major health concern in developing countries because of high levels of mortality and permanent brain damage. Our results provide the first conclusive evidence that important components of the pathology of cerebral malaria include peroxidative stress and protein oxidation within cerebellar gray matter, which are colocalized with elevated nonheme iron at the site of microhemorrhage. Such information could not be obtained previously from routine imaging methods, such as electron microscopy, fluorescence, and optical microscopy in combination with immunocytochemistry, or from bulk assays, where the level of spatial information is restricted to the minimum size of tissue that can be dissected. We describe the novel combination of chemical probe-free, multimodal imaging to quantify molecular markers of disturbed energy metabolism and peroxidative stress, which were used to provide new insights into understanding the pathogenesis of cerebral malaria. In addition to these mechanistic insights, the approach described acts as a template for the future use of multimodal biospectroscopy for understanding the molecular processes involved in a range of clinically important acute and chronic (neurodegenerative) brain diseases to improve treatment strategies.

Chemical alterations to murine brain tissue induced by formalin fixation: implications for biospectroscopic imaging and mapping studies of disease pathogenesis.

Understanding biochemical mechanisms and changes associated with disease conditions and, therefore, development of improved clinical treatments, is relying increasingly on various biochemical mapping and imaging techniques on tissue sections. However, it is essential to be able to ascertain whether the sampling used provides the full biochemical information relevant to the disease and is free from artefacts. A multi-modal micro-spectroscopic approach, including FTIR imaging and PIXE elemental mapping, has been used to study the molecular and elemental profile within cryofixed and formalin-fixed murine brain tissue sections. The results provide strong evidence that amino acids, carbohydrates, lipids, phosphates, proteins and ions, such as Cl(-) and K(+), leach from tissue sections into the aqueous fixative medium during formalin fixation of the sections. Large changes in the concentrations and distributions of most of these components are also observed by washing in PBS even for short periods. The most likely source of the chemical species lost during fixation is the extra-cellular and intra-cellular fluid of tissues. The results highlight that, at best, analysis of formalin-fixed tissues gives only part of the complete biochemical "picture" of a tissue sample. Further, this investigation has highlighted that significant lipid peroxidation/oxidation may occur during formalin fixation and that the use of standard histological fixation reagents can result in significant and differential metal contamination of different regions of tissue sections. While a consistent and reproducible fixation method may be suitable for diagnostic purposes, the findings of this study strongly question the use of formalin fixation prior to spectroscopic studies of the molecular and elemental composition of biological samples, if the primary purpose is mechanistic studies of disease pathogenesis.

Atmospheric iron deposition: global distribution, variability, and human perturbations.

Atmospheric inputs of iron to the open ocean are hypothesized to modulate ocean biogeochemistry. This review presents an integration of available observations of atmospheric iron and iron deposition, and also covers bioavailable iron distributions. Methods for estimating temporal variability in ocean deposition over the recent past are reviewed. Desert dust iron is estimated to represent 95% of the global atmospheric iron cycle, and combustion sources of iron are responsible for the remaining 5%. Humans may be significantly perturbing desert dust (up to 50%). The sources of bioavailable iron are less well understood than those of iron, partly because we do not know what speciation of the iron is bioavailable. Bioavailable iron can derive from atmospheric processing of relatively insoluble desert dust iron or from direct emissions of soluble iron from combustion sources. These results imply that humans could be substantially impacting iron and bioavailable iron deposition to ocean regions, but there are large uncertainties in our understanding.

Urban air quality in the Asian region.

Over the past decade, member states of the Regional Co-operation Agreement (RCA), an intergovernmental agreement for the East Asia and Pacific region under the auspices of the IAEA with the assistance of international organizations and financial institutions such as the World Bank and the Asian Development Bank, have started to set in place policies and legislation for air pollution abatement. To support planning and evaluate the effectiveness of control programs, data are needed that characterizes urban air quality. The focus of this measurement program describe in this report is on size segregated particulate air pollution. Such airborne particulate matter can have a significant impact on human health and urban visibility. These data provide the input to receptor models that may permit the mitigation of these impacts by identification and quantitative apportionment of the particle sources. The aim of this report is to provide an overview of the measurements of concentrations and composition of particulate air pollution in two size fractions across the participating countries. For many of the large cities in this region, the measured particulate matter concentrations are greater than air quality standards or guidelines that have been adopted in developed countries.