On the relative role of hydrodynamic dispersion for river water quality

Gandolfi, Claudio; Facchi, A.; Whelan, M. J.

doi:10.1029/2001wr000249

Cited by 23 publications

(5 citation statements)

References 10 publications

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“…In general, the centroid of the distribution of trapped bottles should gradually shift downstream over time and the variance of the distribution should increase, approximately in accordance with advection-dispersion theory (e.g., Gandolfi et al, 2001). This is illustrated in Figure 5 which shows the predicted plastic bottle travel distance distribution 2, 5, and 10 days after injection, assuming arbitrarily that q(i) = 0.5 for all sub-reaches.…”

Section: Model Performance Beyond the Tracer Studysupporting

confidence: 75%

Macroplastic Debris Transfer in Rivers: A Travel Distance Approach

2021

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Plastic accumulation in the marine environment is a major concern given the harmful effects and longevity of plastics at sea. Although rivers are likely to significantly contribute to the flux of plastic to marine systems, the behaviour of plastic debris in fluvial systems remains poorly understood and estimates of riverine plastic flux derived from field measurements and modelling efforts are highly uncertain. This paper presents a new probabilistic model of plastic transport in rivers which describes the main processes controlling plastic displacement and which predicts the statistical distribution of travel distances for individual items of buoyant macroplastic debris. Macroplastic transport is controlled by retention in temporary stores (or traps) created by vegetation, bank roughness elements and other obstacles. The behaviour of these traps is represented in the model via a series of Bernoulli trials conducted in a Monte Carlo simulation framework. The model was applied to a tracer experiment in a small 1.1 km river reach. Three replicates were used for calibration and three for validation. For each replicate, 90 closed air-filled polyethylene terephthalate (PET) bottles were introduced at the upstream end of the reach and the location of each bottle was recorded after 24 h. Bottles were chosen as “model” macroplastic litter items given their high usage and littering rate. Travel distances were low. The average and maximum distances travelled over 24 h were 231 m and 1.1 km, respectively. They were also variable. The coefficient of variation of travel distances was 0.94. Spatial patterns were controlled by the location and characteristics of discrete traps. The model was able to describe the observed travel distance distributions reasonably well, suggesting that modelling plastic behaviour in longer reaches and even whole catchments using a stochastic travel distance approach is feasible. The approach has the potential to improve estimates of river plastic flux, although significant knowledge gaps remain (e.g., the rate and location of plastic supply to river systems, the transport behaviours of different types of plastic debris and trap effectiveness in different types of river system, season, and discharge).

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Section: Model Performance Beyond the Tracer Studysupporting

confidence: 75%

Macroplastic Debris Transfer in Rivers: A Travel Distance Approach

2021

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“…Computational results of the additional numerical tests with 0.01 D , not presented here, showed that the front shapes of the concentration profiles become more steep and the differences of the profiles of the IBCs become smaller as D decreases. The results agree qualitatively well with the theoretical analysis of Gandolfi et al (2001) who showed that the effect of the dispersion mechanism is negligible if R P is the order of 100 O or more. Nevertheless, the differences between the concentration profiles of the two IBCs are clearly not negligible under the presented conditions and are considered to become more significant for the problems with more complicated conditions.…”

Section: Computational Resultssupporting

confidence: 89%

Internal Boundary Conditions for Solute Transport Equations in Locally One-dimensional Open Channel Networks

Yoshioka

Unami

Fujihara

2013

Journal of Rainwater Catchment Systems

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Transport phenomena of solute in open channel networks are described in the framework of longitudinal dispersion. Modeling of the longitudinal dispersion in an open channel network in general requires the use of a solute transport equation coupled with an internal boundary condition to appropriately determine the dynamics of solute concentration around junctions. However, only a few researches have focused on dependence of the longitudinal dispersion on the internal boundary conditions. This paper carries out theoretical and numerical analysis on two internal boundary conditions that have different physical and mathematical basis with each other. A conforming Petrov-Galerkin finite element scheme is used to solve the solute transport equation. Computational results of a series of numerical simulations reveal that the dynamics of the solute concentration in open channel networks critically depends on the internal boundary conditions in particular for the diffusion-dominant cases that arise in typical situations, indicating their importance in practical analysis.

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“…5). For most elements, the maximum concentrations observed at Gibraleón were around 20-30% lower than those recorded at Sotiel, and the plume pass was more gradual owing to dispersion processes (Gandolfi et al, 2001). However, the maximum Fe concentration was almost 60% lower than at Sotiel (Fig.…”

Section: Impacts On the Odiel Rivermentioning

confidence: 84%