The Fate and Threat of Man-Made Polluted Particles

Pollution can come in many forms. Sometimes it is in the form of chemicals, like pesticides. Sometimes it is in the forms of particles, like soot and microplastics. But what about when it is both? Many researchers these days are now asking, "what is more toxic for a fish that is swimming in microplastic polluted waters, the microplastic or the chemicals in that microplastic?". It is not a far stretch to think it is the chemicals in the microplastic, as many plastics can contain a variety of hazardous chemicals, like bisphenol A, brominated flame retardants, and PCBs. Traditionally, however, environmental research has just focussed on chemical pollution and particle pollution as two different things. Thinking of particles as carriers of pollutants, and developing ways to measure and model this, is a relatively new concept. Exactly this was the key focus of the research project FANTOM. A key drive of the research was to develop new ways of in situ monitoring of so-called "free-phase" contaminants in the environment. "Free-phase" refers to contaminants not sorbed to a particle but rather are freely suspended in air or water. To do this, cutting-edge sampling methodology was developed using novel materials, such as 20 µm think silicon sheets sandwiched between metal cage-like sheets, which an rapidly sample the "free-phase" concentrations in the time scale of days to weeks in water and air, depending on the chemical. This "free-phase" data could then be compared with concentrations in collected particle samples. The FANTOM researchers optimized their work in three polluted areas, the water treatment plants in Oslo Harbor, in an industrial harbor near Nyköping Sweden, and in the industrial area of Grenlandsfjord. In addition, a relatively clean area near Oskarbsorg was used in their field campaign. Another key development was to separate man-made particles from sediment. For this FANTOM researchers developed a low-cost microplastic-sediment separator, they refer to as the Bauta. do to it being shaped like a Bauta stone from the Viking period. The amount of data collected as part of FANTOM was quite large. FANTOM researchers are currently sorting through the data, though have already presented their first results. Part of this data processing involved finding a simplistic way of synthesizing concentration profiles across different environments, like the atmosphere, water and sediments. A simplifying approach they came across was to express concentrations in the form of a concept called "chemical activity", which can be thought of as a unitless concentration. Using this approach, FANTOM scientists can more easily account for the fluxes and even toxicity of contaminants, disentangling the "free-phase" from the "particle-bound" phase, in a relatively simplistic manner. It can be conceptualized that contaminants generally move from areas of high chemical activity to low chemical activity. Further, certain chemical activities are associated with membrane disruption in cells, and therefore are inherently toxic. So, what is more toxic for a fish that is swimming in microplastic water? The answer is, there is no universal answer. However, with results of FANTOM, researchers will now be able to answer this question on a case-by-case basis in a wide variety of chemical and particle polluted environments.

The technology and theoretical approaches developed in FANTOM are of wide-spread interest to the environmental contaminant community. The in situ method FANTOM researchers developed for free-phase contaminant monitoring in air and water is much simpler and portable than state-of-the-art equivalents. Further, the FANTOM designed Bauta microplastic sediment separator has also attracted much interest, as this could simplify separation of man-made polluted particles, like microplastics, in a more economic way than currently available. The presence of hazardous additives (like flame retardants) in microplastic in the ocean is attracting attention. Here the modelling of FANTOM can be used to directly investigate this topic, to differentiate the fate of plastic additives being transported by microplastic vs free-phase emissions. However, the FANTOM approach can be extended to all particles.

Hydrophobic organic contaminants (HOCs) are often introduced into the environment alongside or within man-made particles. As examples, the Baltic Sea continues to be bombarded with dioxin loaded aerosols formed by industrial combustion, and the coast of Å lesund, Norway contains elevated levels of brominated flame retardants from microplastic particles. An increasing number of field observations are providing clues that these man-made particles regulate the exposure of HOCs to the local ecosystem, more so than natural sorbing phases do, contrary to the orthodox view of organic contaminant research. To address this, I hypothesize that risks from man-made organic contaminants depend on the man-made particles that introduce them into the environment, particul arly for man-made combustion, petroleum and sewage residues, as well as nanoparticles and microplastics. Methods: I seek to gain unprecedented, highly resolved profiles of dissolved HOCs and particulate bound HOCs along air-water-sediment transects in co ntaminated coastal areas. For this, I have designed novel equipment that will simultaneously and passively sample dissolved and particulate-bound HOCs. This equipment takes full advantage of the most recent advances in passive sampling technology and mari ne technology design. Four, unique areas will be studied that vary in terms of how the HOCs are introduced: atmospheric deposition, microplastic pollution, river dredging and water treatment overflow. Impact: Combining HOC profiles, geochemical characte rization and biogeochemical process modelling, unparalleled accounts of man-made particulate - pollutant dynamics will be obtained. This will shift the focus of HOC pollution research, improve risk and management guidelines, introduce novel technology and methods, inform on the remediation strategies for contaminated areas such as natural recovery, as well as be transferable to assessing emerging threats from nanoparticles and microplastics.