posted on 2024-03-13, 20:30authored byGabriel Erni-Cassola, Reto Dolf, Patricia Burkhardt-Holm
Measured microplastic
concentrations in river surface waters fluctuate
greatly. This variability is affected by season and is codriven by
factors, such as sampling methodologies, sampling site, or sampling
position within site. Unfortunately, most studies comprise single-instance
measurements, whereas extended sampling periods are better suited
to assessing the relevance of such factors. Moreover, microplastic
concentrations in riverine water column remain underexplored. Similar
to the oceans, however, this compartment likely holds significant
amounts of microplastics. By representatively sampling the entire
Rhine River cross-section near Basel through five sampling points
over 22 months, we found a median microplastic (50–3000 μm)
concentration of 4.48 n m–3, and
estimated a widely ranging load between 4.04 × 102n s–1 and 3.57 × 105n s–1. We also show that
the microplastic concentration in the water column was not well explained
by river discharge. This suggests that although high discharge events
as observed here can over short time periods lead to peak microplastic
concentrations (e.g., 1.23 × 102n m–3), microplastic load variance was not dominated
by discharge in the study area.