Technological innovations to mitigate plastic pollution in water bodies, called plastic clean-up technologies, have increased in recent years. One of the devices used in European rivers, ports, and harbors is an air-bubbling curtain system (commonly used to block the passage of jellyfish, oil spills, etc). However, the knowledge of their environmental impact is limited, particularly about bycatch or the unintentional collection of non-plastic materials such as reed (i.e., vegetation material). The goal of this work was to determine the effects of (1) plastic litter type, (2) water flow, and (3) plastic litter load on items caught and bycatch of the air bubble curtain mechanism. To do so we did series of flume experiment with an air bubbling prototype and used Bayesian Belief Network (BBN) model. The structure of the BBN was simplified based on natural riverine environment and the observations in the experiment. We also asked for expert knowledge in developing the model which consist of the nexus of flow velocity, plastic object, plastic load, biota, and biota load to plastic caught and bycatch. The model simulation showed that plastic caught in the air bubble has the probability of changing depending on the plastic object due to characteristics of plastic objects that affect their transport and deposition, favouring floating plastics such as bottles. The plastic items do not affect the amount of bycatch due to the minimal interaction of plastics and reeds. We also observed that the probability of more plastic being caught, and the amount of bycatch increase with flow velocity. The amount of plastic loaded only had a negligible effect on the amount of plastic caught and did not affect bycatch. Overall, the study suggests that the air-bubbling mechanism is more likely to collect bycatch than plastic. The plastic caught-to-bycatch ratio is 1:3 at low flow and 3:4 at high flow. Our study is innovative and provides new insights in the growing holistic understanding of the impacts of plastic clean-up technologies to effectively maximize their potential as a complementary tool amongst other measures to mitigate plastic pollution.
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