Objective 1: How does NP shape affect groundwater transport?
The study showed that non-spherical nanoplastics exhibit up to three times higher deposition rates than spherical particles on simple quartz surfaces, indicating reduced transport. However, on more complex minerals like kaolinite, surface functional groups were more influential than particle shape in determining deposition behavior. This pattern remained unchanged in the presence of organic matter. Therefore, in realistic groundwater environments, surface chemistry plays a more significant role in nanoplastic retention than particle shape.
Objective 2: Can flow rates modify NP transport in porous media?
This objective was fully achieved. Using sediment column experiments, it was found that high flow rates (50 m/d), typical of macropores and infiltration zones, significantly enhance nanoplastic transport, regardless of mineral type or interaction conditions. In contrast, low flow rates (1 m/d), representative of typical groundwater velocities, did not support NP transport. These results highlight that NP mobility is primarily enabled in fast-flowing subsurface environments.
Objective 3: Are fungal communities able to retain NP under realistic aquifer conditions?
This objective was fully achieved. While batch and column experiments showed no measurable NP retention by fungal hyphae, microfluidic chip experiments revealed a site-limited adsorption process. Once reactive sites on the hyphae were saturated, no further NP retention occurred. This suggests that fungal hyphae can retain environmentally relevant NP concentrations (<1 ppm) in groundwater systems under flow conditions.
