Discovering persistent pollution in remote places

Every year, I do a small stint of lecturing at the Australian National University here in Canberra. I cover broad issues related to contaminated lands and catchment management in these lectures, covering topics such as which chemicals are monitored during a standard contaminated sites investigation; what types of groundwater data are collected during a standard groundwater monitoring event assessing groundwater pollution and what the data do and do not mean; and how pollution is managed and prevented in Australia.

I met Xin Liu after one such lecture. Keen to enhance his abilities to address pollution problems in the environment, Xin begun work with me on a number of different projects that focused on pollution as part of his Masters degree. Together with a number of other scientists who specialise in different aspects of pollution, we converted the work he did as part of his final project into a scientific research article. This blog is a summary of what we found.

Our work focused on understanding what types of pollutants might be found in dust that rises in Australia’s rural arid and semi-arid regions and moves across Australia in dust storms. We had access to thousands of samples as a result of DustWatch, a program that sees citizen scientists from across Australia head outside to collect dust, then send what they collect in to scientists like us who can use it to understand phenomena like wind erosion and air quality.

A dust storm near Mildura. Photo courtesy of Shutterstock

We selected ten DustWatch samples dating from 1990 to 2018 for analyses, with all of these samples collected from a remote rural site (Buronga) near Mildura. Limiting the number of samples in this way, and to this one location, meant that we could understand whether there was any point looking at dust samples in remote areas for pollutants in the first place — there was the possibility we would find nothing. Limiting sample numbers also meant we could also constrain whether the lack of appropriate storage on these samples had made our research unviable or not; normally environmental samples which are to be assessed for pollution are stored in refrigerators, as many chemicals that occur in soils or dusts flux off to the atmosphere at normal room temperatures. Finally, because of the way in which the dust samples were stored, we could only assess for chemicals that were persistent. Such persistence is a key characteristic of pollutants, however, as chemicals that degrade easily are far less likely to be pollutants in the first place (although there are some exceptions like nitroxides).

I was very surprised to see what Xin found in the samples analysed.

All families of persistent organic pollutants that we looked for were found in the samples analysed. This included chemicals like DDT and DDE, hexachlorobenzene (HCB), polychlorinated biphenyls (PCBs), hexachlorocyclohexane (HCH), poly‑brominated diphenyl ethers (PBDEs) and per- and poly-fluoroalkyl substances (PFASs). Some of these chemicals, like DDT and PCBs have been banned in Australia for decades. Others, like the PFAS group that includes perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS), have only been phased out of use in Australia over the last decade.

We found the insecticide DDT at concentrations of up to 68 ng/g. This chemical, banned in 1987, reflects its ongoing role in environmental pollution. Although it is unclear whether the source of DDT in this case is local or somewhere in the world ― another feature of the persistent organic pollutant group of chemicals, of which DDT is part, is that these chemical are subject to long-range atmospheric transport and can cause environmental impacts thousands of kilometres from their source.

Other chemicals, such as the flame retardant PBDEs indicate pollution from industrial or urban sources where flame retardants have been applied to furniture or electronics equipment. We found this group of chemicals in concentrations of up to 40.6 ng/g. The PFAS group of chemicals can reflect pollution from sources including landfills, sewage treatment plants, airports, and even paper recycling plants, and was in concentrations of up to 690 ng/g.

It was impossible to constrain the ultimate source of pollutants from the data that we collected in our study. We could only conclude that these chemicals were there, in these dust samples collected from a remote and rural area of Australia from which much dust originates. We also didn’t try to interpret the environmental or human health hazard from the dust we assessed ― just trying to understand what was there was enough for this initial study. What we can say, is that there is clear evidence of pollution arising from human activities in even remote areas of Australia, far from the urban and industrial centres from which such pollution is generally generated. We also know that this dust moves from its source in arid Australia, across its east coast, to destinations including New Zealand and Antarctica.

The authors of this paper are grateful to Dr Dave Brittain for suggestion on its scope and direction, and Dr Jochen Mueller and two anonymous reviewers for their review. The full version of this article is published in the Australasian Bulletin of Ecotoxicology and Environmental Chemistry, and can be found here.

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