Assessment of road run-off and domestic wastewater contribution to microplastic pollution in a densely populated area (Flanders, Belgium).

Plastics are omnipresent in our daily life. Unfortunately, the produced plastics will partly end up in the environment including aquatic ecosystems. People often refer to littering or illegal waste dumping as sources of plastic emission to the environment. However, daily-life sources could also, unknowingly, contribute considerably to the total microplastic pollution in the ecosystem. Hence, there is an urgent need to study these potential sources. In this research, two common sources, i.e. domestic wastewater and road run-off from tire and road wear particles, were studied in detail to quantify the relative contribution of both domestic sources towards microplastic pollution in freshwater ecosystems in Flanders, Belgium. This assessment shows that every person (in studied area) emits on average 1145 microplastics (25-1000 µm) daily through domestic wastewater, resulting in a yearly discharge of 418,000 microplastic particles per person. The road run-off samples contained between 0.02 and 9.2 mg tire wear particles per litre per day, which corresponds to an emission of 10.8 mg tire wear particles per driven vehicle km. The gross and net emissions of both above mentioned microplastic sources were extrapolated to the whole Flanders region using an emission model. From the yearly gross microplastic pollution in the domestic wastewater, 623 kg (20%) will be discharged in the freshwater. The highest losses originated from the households that have a private drain or are not (yet) connected to an active wastewater treatment plant. In Flanders, the yearly net microplastic emission into the aquatic environment of tire wear particles is estimated to be 246 tonnes (38%), mainly from the direct run-off from the road surface. Based on the results, specific mitigation measures can be installed to reduce the emission of microplastics towards the freshwater ecosystem. Other sources should be quantified in a similar way for a more holistic strategy to counteract plastic pollution.

The importance of uncertainties in scenario analyses--A study on future ecosystem service delivery in Flanders.

Land use is rapidly changing and is significantly affecting ecosystem service delivery all around the world. The socio-economic context and political choices largely determine land use change. This land use change, driven by socio-economic pressures, will impact diverse elements of the environment including, for example, air quality, soil properties, water infiltration and food and wood production, impacts that can be linked to the provisioning of ecosystem services. To gain more insight into the effects of alternative socio-economic developments on ecosystem service delivery, land use change models are being coupled to ecosystem service delivery models to perform scenario analyses. Although the uncertainty of the results of these kind of scenario analyses are generally far from negligible, studies rarely take them into account. In this study, a cellular automaton land use change model is coupled to Bayesian belief network ecosystem service delivery models to facilitate the study of error propagation in scenario analysis. The proposed approach is applied to model the impact of alternative socio-economic developments on ecosystem service delivery in Flanders, Belgium and to assess the impact of land use allocation uncertainty on the uncertainty associated to future ecosystem service delivery. Results suggest that taking into account uncertainties may have an effect on policy recommendations that come out of the scenario analysis. However, in this study, uncertainties in the applied ecosystem service models were dominant, reducing the importance of accounting for land use allocation uncertainty.