Macroplastic Fate and Transport Modeling: Freshwaters Act as Main Reservoirs.

Macroplastic fate and transport in the freshwater environment are of great concern due to the potentially harmful effects of macroplastic on plants, animals, and humans. Here, we present a modeling approach to simulate macroplastic fate and transport at the country scale based on an existing plastic release model. The fate model was parametrized through available monitoring data and results from field experiments and applied to Swiss rivers and lakes. We found that almost all (98%) macroplastic emissions into freshwater remain within Switzerland. After exploring the influences of weirs, retention in rivers, and retention in lakes through a sensitivity analysis, we found a high retention variability across different catchments and within rivers. In all 22 analyzed scenarios for continuous retention along each river bank (i.e., beaching), we found that at least 70% of input emissions into the water bodies would be retained long-term in the catchments (about 200 g per river km and year). Across all catchments, we found a dominance of "continuous retention" through beaching along the entire river length compared with "point retention" at weirs or lakes. Thus, by modeling macroplastic fate and transport on a country level for the first time, we were able to confirm the concept of "rivers as plastic reservoirs" through modeling.

Tire wear particle emissions: Measurement data where are you?

Tire wear particle (TWP) emissions are gaining more attention since they are considered to contribute a major share to the overall microplastic emissions and are suspected to be harmful to flora, fauna and humans. Hence, recent studies derived country-based TWP emissions to better understand the significance of the problem using either tire emission factors (EF) or a material flow analysis (MFA) of tires. However, all 14 country-based TWP emission studies found and published since the year 2000 base their calculation on other studies rather than own measurements. Therefore, we started to search for the actual TWP measurements which the 14 studies would rely on. As a result, we found a network of 63 studies which were used to derive TWP emissions in different countries and regions. Only in few cases (12%) TWP emission studies reference directly to a measurement study to derive TWP emissions, but mostly (63%) they rely on reviews or summarizing studies. Additionally, we could not obtain 25 studies in the analysed network. In total we found nine studies which actually measured TWP emissions. Out of these four studies originate from the 1970s, one analysed only light vehicles and one only considered buses. Thus, only three non peer-reviewed studies were considered to show trustful results which were cited a maximum of three times in the network. The obtained 14 country-based studies suggest TWP emissions of about 1.3 kg capita-1 year-1 for the EF approach and 2.0 kg capita-1 year-1 for the MFA approach (overall range: 0.9-2.5 kg capita-1 year-1). Consequently, we call for an urgent need to minimize uncertainties of TWP emission estimates to better understand the contribution of TWP to the overall microplastic pollution of the environment. A better understanding about quantities could also help to better address the risk of environmental pollution by TWP.