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Dataset of ADCP data used to test to which extend items are detectable using ADCP echo. The objectives of the exploratory research were to: (1) determine the range of echo intensity and the effect item characteristics, such as orientation, form and material, have on this echo intensity, (2) confirm the detectability of the plastic items in a natural environment with other disturbances such as air bubbles and aquatic life, and (3) evaluate an ADCP plastic monitoring method in the field with simultaneous net measurements. We deployed three ADCPs in three different environments. In a basin and harbor, (semi-)controlled experiments are undertaken where an ADCP is fixed horizontally below the water surface and plastics are introduced within the beam. In a river an uncontrolled experiment is undertaken, where a vessel mounted ADCP is deployed and 'naturally' present plastics are studied. The dataset contains raw ADCP data files.

Plastic pollution has become an enormous environmental problem, endangering ecosystems, livelihoods, safety and human health. Large quantities of plastics are trapped in or transported by rivers. Monitoring methods mostly focus on plastics floating at the surface or deposited on riverbanks, while a substantial part of plastics may be transported below the water surface. Available underwater monitoring methods rely on nets and large equipment, making them labour-intensive, expensive and invasive. The measurements are, therefore, limited to occasional point measurements. In this paper, we explore the potential of echo sounding for the monitoring of suspended macroplastic (plastic items bigger than 5 mm). We performed tests in a controlled (basin), a semi-controlled (harbour) and an uncontrolled (river) environment using the high-end Acoustic Doppler Current Profiler (ADCP). This device is already in use for the estimation of flow velocity and suspended sediment concentrations using the wide network of ADCPs in the Netherlands and other countries. In the undisturbed controlled environment, 25 items varying in size, material, and orientation could be detected up to at least 4.6 m from the ADCP. The semi-controlled experiments showed that most of these items can also be detected among other naturally occurring scatterers, such as aquatic life, organic material and air bubbles. The field tests under natural conditions, combining ADCP and net measurements, showed that ADCP data can be calibrated towards a correct order of magnitude estimate of plastic transport. The coupling of the ADCP data to item characteristics such as size, material and orientation is still challenging, but more research into, for example, the signature of items may enable distinguishing item characteristics. This fundamental knowledge, combined with repetitions of validated field measurements under different flow conditions, is needed for the development of a robust monitoring method. Such a method m

Plastics originating from land are mainly transported to the oceans by rivers. The total plastic transport from land to seas remains uncertain because of difficulties in measuring and the lack of standard observation techniques. A large focus in observations is on plastics floating on the water surface. However, an increasing number of observations suggest that large quantities of plastics are transported in suspension, below the water surface. Available underwater plastic monitoring methods use nets or fish traps that need to be deployed below the surface and are labor-intensive. In this research, we explore the use of echo sounding as an innovative low-cost method to quantify and identify suspended macroplastics. Experiments under controlled and natural conditions using a low-cost off-the-shelf echo sounding device show that plastic items can be detected and identified up to 7 m below the river surface. Eight different debris items (metal can, cup, bottles, food wrappers, food container) were characterized based on their reflection signature. Reflectance from plastic items diverged significantly from organic material and non-plastic anthropogenic debris. During a multi-day trial field expedition in the Guadalete river, Spain, we found that between 0.8 and 6.3 m depth considerable quantities of plastics are transported. As most plastic monitoring and removal strategies focus on the upper layer below the surface (up to approximately 1.5 m depth), a substantial share of the total plastic transport may be neglected. With this paper we 1) demonstrate that echo sounding is a promising tool for underwater plastic monitoring, and 2) emphasize the importance of an improved understanding of the existing plastic loads below the surface.

Dit onderzoek is uitgevoerd in opdracht van Rijkswaterstaat WVL (Water, Verkeer en Leefomgeving). Het is gericht op het verkennen van akoestische sensoren voor het monitoren van (macro)plastic in de waterkolom. De uitkomsten dragen bij aan de eventuele ontwikkeling van technieken voor het meten en monitoren van onderwaterplastics. Het doel van dit project is het verkrijgen van inzicht in de potentie van akoestische sensoren om de plastic-concentratie in de waterkolom van rivieren automatisch te monitoren. Hierbij is het de ambitie om een zo volledig mogelijk overzicht te generen van beschikbare technieken met bijbehorende voor- en nadelen.

Plastics originating from land are mainly transported to the oceans by rivers. The total plastic transport from land to seas remains uncertain because of difficulties in measuring and the lack of standard observation techniques. A large focus in observations is on plastics floating on the water surface. However, an increasing number of observations suggest that large quantities of plastics are transported in suspension, below the water surface. Available underwater plastic monitoring methods use nets or fish traps that need to be deployed below the surface and are labor-intensive. In this research, we explore the use of echo sounding as an innovative low-cost method to quantify and identify suspended macroplastics. Experiments under controlled and natural conditions using a low-cost off-the-shelf echo sounding device show that plastic items can be detected and identified up to 7 m below the river surface. Eight different debris items (metal can, cup, bottles, food wrappers, food container) were characterized based on their reflection signature. Reflectance from plastic items diverged significantly from organic material and non-plastic anthropogenic debris. During a multi-day trial field expedition in the Guadalete river, Spain, we found that between 0.8 and 6.3 m depth considerable quantities of plastics are transported. As most plastic monitoring and removal strategies focus on the upper layer below the surface (up to approximately 1.5 m depth), a substantial share of the total plastic transport may be neglected. With this paper we 1) demonstrate that echo sounding is a promising tool for underwater plastic monitoring, and 2) emphasize the importance of an improved understanding of the existing plastic loads below the surface.

Plastic pollution in aquatic ecosystems is a global problem. Rivers transport large quantities of litter from land to the oceans. Plastics of different sizes and properties are widely present at various locations in river systems. Concerning macroplastics, previous studies mainly focussed on floating plastics, however, substantial parts of the litter can be transported underneath the water surface. Currently, this suspended litter load remains understudied. Submerged litter is presently monitored with the use of nets. The use of nets has several disadvantages. In large rivers, nets can usually, not be deployed over the full depth and width of the river. Moreover, using nets is labour intensive and requires fixed structures to be deployed. To overcome this problem, this thesis aimed to develop and test a new method for monitoring submerged riverine litter. In accordance with the fish detection abilities of sonar, it seems to have a high potential for identifying suspended underwater objects. In this study, the litter detection ability of a low-cost single beam echosounder (Deeper CHIRP+) were investigated. Three different experiments were executed, in specific, controlled tests in an artificial environment, semi-controlled tests in a natural environment and litter monitoring in a naturally flowing river. The controlled tests, to get an insight into the scanning technique and detection abilities of the echosounder, were performed in the Kerkpolderbad in Delft. During these tests, the influence of actual object size, object depth and flow velocity on the sonar signal was investigated. The semi-controlled tests were carried out in the Rio de San Pedro, in Andalusia, Southern Spain. During these tests, several plastic targets were used and repeatedly released in the river, passing the sensor. For this, objects of different material properties and sizes were used. Lastly, plastic was monitored in the Guadalquivir and Guadalete rivers in Andalusia. In the Guadalq, Water Management

Plastic pollution in aquatic ecosystems is a global problem. Rivers transport large quantities of litter from land to the oceans. Plastics of different sizes and properties are widely present at various locations in river systems. Concerning macroplastics, previous studies mainly focussed on floating plastics, however, substantial parts of the litter can be transported underneath the water surface. Currently, this suspended litter load remains understudied. Submerged litter is presently monitored with the use of nets. The use of nets has several disadvantages. In large rivers, nets can usually, not be deployed over the full depth and width of the river. Moreover, using nets is labour intensive and requires fixed structures to be deployed. To overcome this problem, this thesis aimed to develop and test a new method for monitoring submerged riverine litter. In accordance with the fish detection abilities of sonar, it seems to have a high potential for identifying suspended underwater objects. In this study, the litter detection ability of a low-cost single beam echosounder (Deeper CHIRP+) were investigated. Three different experiments were executed, in specific, controlled tests in an artificial environment, semi-controlled tests in a natural environment and litter monitoring in a naturally flowing river. The controlled tests, to get an insight into the scanning technique and detection abilities of the echosounder, were performed in the Kerkpolderbad in Delft. During these tests, the influence of actual object size, object depth and flow velocity on the sonar signal was investigated. The semi-controlled tests were carried out in the Rio de San Pedro, in Andalusia, Southern Spain. During these tests, several plastic targets were used and repeatedly released in the river, passing the sensor. For this, objects of different material properties and sizes were used. Lastly, plastic was monitored in the Guadalquivir and Guadalete rivers in Andalusia. In the Guadalq, Water Management