Search

Plastic pollution in aquatic environments is a growing concern, with rivers recognized as major pathways. However, rivers themselves are also subject to pollution. Hence, understanding riverine plastic transport dynamics is essential for mitigating environmental impacts. Although plastic-related research focus has shifted from marine environments towards rivers, challenges remain in standardizing methods for monitoring and integrating spatiotemporal variabilities of riverine plastic occurrence into flux determination. This study addresses these challenges by adopting established methods from sediment research. Utilizing data from a net-based cross-sectional multi-point approach, it examines spatio-temporal and discharge-dependent variations. It comprehensively analyzes the complex dynamics of plastic transport in the Danube River, contrasting an impounded section near Aschach, Austria, with a free-flowing reach near Hainburg, Austria. The paper emphasizes the significance of applying these methodologies for accurate flux determination and underscores the risks of neglecting them. By incorporating average microplastic particle weights, we aim to overcome limitations in prior methodologies that solely emphasize qualitative aspects or rely on item numbers. Spatial distribution analysis revealed a pronounced stratification at low flow and a more variable distribution in the free-flowing section, attributed to higher turbulence. As discharge increased, vertical mixing occurred, along with distinct lateral patterns displaying increased concentrations toward the riverbanks. Encountering plastic particles throughout the river profile underscores their properties of both suspended and floating matter, emphasizing the importance of hydro-morphology and multi-point cross-sectional measurement approaches. Microplastic loads were calculated to be <6.9 t a-1 in Aschach and <17.1 t a-1 in Hainburg, compared to total plastic loads of <14.3 t a-1 in Aschach and <41.6 t a-1 in Hainburg. Consequently, plastic loads were doubled to tripled within the Austrian section of the Danube River. The study contributes valuable insights into the complex nature of plastic transport in river systems, emphasizing comprehensive spatial, temporal and discharge-dependent assessments for characterizing and managing plastic pollution. It suggests that rivers can function as sources, pathways and sinks of plastic pollution, contingent upon hydro-morphological conditions. This underscores the need for longitudinal, basin-wide assessments to accurately understand plastic transport dynamics. [ABSTRACT FROM AUTHOR]

Since the industrial revolution, human impacts on landscapes and river systems globally have intensified significantly. Humans nowadays artificially increase and decrease fluxes of water, sediment and nutrients on a scale far exceeding natural fluxes. Rivers integrate such changes occurring throughout their drainage basins, and thus can be considered as indicators of landscape processes and river basin "health" more broadly. This special issue brings together a set of papers that explore interactions of climate change and river processes, influences of land use changes, effects of reservoirs, as well as new approaches to sorting out the relative importance of these diverse influences on rivers and uncertainties in modeling future behavior. These papers contribute to a growing body of work demonstrating the fundamental differences between large rivers in the Anthropocene and rivers in prior time periods. © 2014. American Geophysical Union. All Rights Reserved.

Global warming and glacier retreat are affecting the morphodynamics of proglacial rivers. In response to changing hydrology, the altered hydraulics will significantly impact future glacifluvial erosion and proglacial channel development. This study analyses a proglacial channel evolution process at the foreland of Austria's biggest glacier Pasterze, by predicted runoff until 2050 based on a glacio-hydrological model. A high-resolution digital elevation model was created by an unmanned aerial vehicle, sediment was sampled, a one-dimensional hydrodynamic-numerical model was generated, and bedload transport formulas were used to calculate the predicted transport capacity of the proglacial river. Due to the fine sediment composition near the glacier terminus (d50< 79 mm), the calculation results underline the process of headward erosion in the still unaffected, recently deglaciated river section. In contrast, an armor layer is already partly established by a coarser grain size distribution in the already incised river section (d50> 179 mm). Furthermore, already reoccurring exposed non-fluvial grain sizes combined with decreasing flow competence in the long term indicate erosion-resistant pavement layer formation disconnecting the subsurface sediments for glacifluvial reworking (vertical landform decoupling). The presented study shows that subsystems exhibiting pavement layer formation by grains exceeding the predicted transport capacity supported by non-fluvial sediments are found at the investigated glacier foreland. Thus, an extension accompanied by a refinement of the glacifluvial system in the sediment cascade approach was developed as a central result. [ABSTRACT FROM AUTHOR]