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 × 10² n s^–1 and 3.57 × 10⁵ n 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 × 10² n m^–3), microplastic load variance was not dominated by discharge in the study area.

中文翻译：

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巴塞尔附近莱茵河水体中的微塑料：22 个月的采样

河流表层水中测得的微塑料浓度波动很大。这种变化受到季节的影响，并受到采样方法、采样地点或采样地点内采样位置等因素的共同驱动。不幸的是，大多数研究都包含单实例测量，而延长采样周期更适合评估这些因素的相关性。此外，河流水体中的微塑料浓度仍未得到充分研究。然而，与海洋类似，这个隔间可能含有大量的微塑料。通过在 22 个月内通过五个采样点对巴塞尔附近的整个莱茵河断面进行代表性采样，我们发现微塑料（50–3000 μm）浓度中位数为 4.48 nm ^–3，并估计负载范围广泛为 4.04 × 10 ² ns –1和 3.57 ^× 10 ⁵ ns –1 ^。我们还表明，河流排放不能很好地解释水体中的微塑料浓度。这表明，虽然此处观察到的高排放事件可以在短时间内导致微塑料浓度达到峰值（例如，1.23 × 10 2 ⁿ m –3 ^），但研究区域中的微塑料负荷变化并非由排放主导。