240 research outputs found
sj-pdf-1-wmr-10.1177_0734242X231180863 – Supplemental material for Knowns and unknowns of plastic waste flows in the Netherlands
No full textSupplemental material, sj-pdf-1-wmr-10.1177_0734242X231180863 for Knowns and unknowns of plastic waste flows in the Netherlands by Delphine Lobelle, Li Shen, Bas van Huet, Tim van Emmerik, Mikael Kaandorp, Giulia Iattoni, Cornelius Peter Baldé, Kara Lavender Law and Erik van Sebille in Waste Management & Research</p
sj-pdf-2-wmr-10.1177_0734242X231180863 – Supplemental material for Knowns and unknowns of plastic waste flows in the Netherlands
No full textSupplemental material, sj-pdf-2-wmr-10.1177_0734242X231180863 for Knowns and unknowns of plastic waste flows in the Netherlands by Delphine Lobelle, Li Shen, Bas van Huet, Tim van Emmerik, Mikael Kaandorp, Giulia Iattoni, Cornelius Peter Baldé, Kara Lavender Law and Erik van Sebille in Waste Management & Research</p
Water stress detection using radar
No full textVegetation is a crucial part of the water and carbon cycle. Through photosynthesis carbon is assimilated for biomass production, and oxygen is released into the atmosphere. During this process, water is transpired through the stomata, and is redistributed in the plant. Transpired water is refilled by uptake of water from the root zone in the subsurface. Transpiration by vegetation accounts for most of the total evaporation from land on a global scale. In some ecosystems, such as tropical rainforests, transpiration even makes up more than 70% of total evaporation. Periods of low water availability, water stress, leads to irreversible damage to plants, and can eventually lead to plant death. To prevent this, various mechanisms are activated by the vegetation to survive. Transpiration is reduced as a result of vegetation water stress, which can affect the water and carbon cycle on local, regional, and even global scales. Additionally, water stress in crops is one of the major reasons for harvest losses, threatening food security. However, many effects of vegetation water stress on crops and tropical forests remains poorly understood.New satellite observations provide opportunities for better detection and understanding of vegetation water stress. Recent research suggests that radar remote sensing might yield valuable insights into vegetation water content. Radar backscatter is sensitive to vegetation because of direct backscatter from the canopy, and through two-way attenuation of the signal as it travels through the vegetation layer. The degree of interaction of radar waves with the vegetation is mainly a function of the vegetation dielectric constant, which is in turn primarily influenced by vegetation water content. Over the last years, various studies have reported links between anomalies in radar backscatter and vegetation water stress. This has led to the hypothesis that radar backscatter is sensitive to vegetation water stress. Additional field measurements of vegetation water content and dielectric constant, in combination with radar backscatter are necessary to test this hypothesis. This is what inspired this thesis. Based on a combination of field measurements using new sensors, models, and radar backscatter, this thesis focuses on understanding the effects of water stress on plant dynamics, identifying early signatures of vegetation water stress, and exploring the opportunities of early water stress detection using radar remote sensing. This thesis studies the effects of vegetation water stress across scales, from individual leaves to rainforests. A new method is presented that allows measurements of leaf dielectric properties on living plants. First, the method is tested on tomato plants in a controlled environment. By measuring tomato plants with and without water stress, it is demonstrated that there is a significant difference in the leaf dielectric properties of stressed and unstressed tomato plants. Second, this same method is used under field conditions. Using data sets of corn plants with and without water stress, it is demonstrated that water stress changes plant water content, resulting in significant changes of leaf dielectric properties. Using the field data from the stressed corn field, a modeling study was done to investigate the sensitivity of radar backscatter to water stress. Here, it is shown that total and leaf water content can change considerably during the day, leading to observable differences in radar backscatter.To study the effects of water stress in tropical rainforests, accelerometers were placed on trees in the Brazilian Amazon to measure tree sway. Tree sway depends on various tree properties, and this thesis demonstrates that the measured tree acceleration is sensitive to tree mass, intercepted rainfall, and tree-atmosphere interactions. Using five months of acceleration data from 19 trees, an effect of the transition from the wet to the dry season was found. This thesis hypothesizes that this was caused by water related changes in tree mass, or leaf fall in response to increased tree water deficit.Finally, coinciding field data on tree water content and tree water deficit, and radar backscatter, were used to demonstrate the sensitivity of radar backscatter to increased water stress. During the transition from wet to dry season, a strong drop was found in radar backscatter, which is explained by a rapid increase in measured tree water deficit.For years, the hypothesis that radar backscatter is sensitive to vegetation water stress has been discussed. Yet, a lack of observations withheld this hypothesis to be tested. This thesis uses field data of crops, and trees in tropical forests, and modeling approaches to finally demonstrate that vegetation water stress results in significant changes in plant water status, which lead to observable variations in radar backscatter.Water Resource
Some milestones in the life and work of the mathematical chemist J.J. Van laar (1860-1938): Calphad XIX (1990)
No full textThis lecture: 'Some Milestones in the Life and Work of Mathematical Chemist J.J. van Laar (1860-1938)' discusses his life and three important examples of his work. Insufficient schooling meant that Van Laar was not permitted to take academic examinations and this lack of recognized qualifications led to problems in establishing his scientific career. These difficulties brought him close to mental collapse in 1896 and 1911. At the University of Amsterdam he was opposed by J.D. Van der Waals (1837-1923) but was highly appreciated by H.W. Bakhuis Roozeboom (1854-1907). This lecture focuses on some of his achievements and describes his recognition as a scientist. H.A. Lorentz (1853-1928) played an important part in Van Laar's development as a mathematical chemist. Van Laar is said to have endowed him with 'the father role' and it is certain that Lorentz encouraged and supported him. The study of mathematical chemistry as Van Laar practiced it no longer exists. Together with Bakhuis Roozeboom, Van Laar is the founder of phase theory. Examples of his work are discussed in the sections of the melting point line of tin amalgam (1902), the spinodal (1905) and retrograde solubility (1908). The lecture concludes with a description of the final years of his life and includes the kind letter of condolence by L.S. Ornstein (1880-1941). Throughout the lecture reference is made to fragments of letters and to photographs.Applied Science
Editorial: Contributions to river plastic monitoring across scales, volume II
No full textPlastic pollution in aquatic environments has emerged as a critical global issue, with rivers playing a significant role in transporting plastic debris from land to sea. The complexity of riverine plastic transport is influenced by various factors, including the physical properties of plastics such as type, size, shape, and density, which affect their spatiotemporal distribution in flowing waters (Range et al., 2023). Rivers, however, not only act as conduits for plastic debris but also serve as temporary or perpetual sinks, particularly in tidal zones or compounded stretches, also contributing to the formation of localized accumulation zones (van Emmerik et al., 2022; Liro et al., 2022). These riverine plastic hotspots, while smaller in scale compared to oceanic counterparts, exhibit significantly higher concentrations of plastic, posing risks to ecosystem functioning and human health (e.g., Liro et al., 2022; Tasseron et al., 2024).
Monitoring and quantifying plastic transport in rivers is essential for understanding the dynamics of plastic emissions and validating global estimates (Vriend et al., 2020). Despite advancements in detection technologies, such as deep learning and acoustic methods, challenges remain in achieving continuous and accurate monitoring data and in method harmonization (van Emmerik et al., 2023). New techniques like using the Acoustic Doppler Current Profiler (ADCP) for macroplastic detection (Boon et al.) and instance segmentation models using deep learning architectures like YOLOv8 (e.g., Ahmed et al., 2023; Fan et al., 2024; Kataoka et al.) are being developed to enhance detection capabilities and provide more reliable data. An important step was made towards harmonization of data evaluation and determination of plastic transport (Pessenlehner et al.). These innovations are important in order to create simplified application possibilities and thus improve global datasets and their interpretation. The urgency of addressing plastic pollution is underscored by its detrimental impacts on ecosystems and human health, necessitating comprehensive research and effective policy measures. Plastic debris can lead to ingestion, entanglement, and suffocation of marine life, and its presence in the food chain poses severe health risks to humans, including exposure to toxic chemicals (e.g., Issac and Kandasubramanian, 2021). Global efforts, including the UN’s push for a legally binding treaty (March et al., 2024; UNEP, 2024) and the EU’s ban on single-use plastics, highlight the need for coordinated action to mitigate these impacts (European Commission, 2022; IISD, 2022)
Meetprotocol drijvend zwerfafval en macroplastic in rivieren
No full textOp dit moment is het onbekend hoeveel zwerfafval en macroplastics door de Nederlandse Rijkswateren stroomt en hoeveel daarvan uiteindelijk in zee terechtkomt. Daarnaast is het onduidelijk in hoeverre geanalyseerde monsters uit andere riviersystemen representatief zijn voor de Nederlandse Rijkswateren. Zwerfafval en macroplastics in en rondom riviersystemen is echter een groeiend probleem, en het daarom belangrijk is om drijvend afval en macroplastics te monitoren. Betrouwbare monitoring van zwerfafval en macroplastics in en rondom rivieren is essentieel om beleid- en beheervragen te beantwoorden en om geschikte maatregelen te nemen. In dit rapport wordt ingegaan op een belangrijk onderdeel bij de monitoring van drijvend afval en macroplastics in rivieren: het protocol waarin de systematiek van de metingen beschreven staat en met welke aspecten bij de opzet van een meting rekening dient te worden gehouden. Er kan gebruik worden gemaakt van telmetingen vanaf bruggen op relevante en representatieve locaties via de visual counting-methode. Daarnaast kan er een analyse van lokaal zwerfafval op oevers nabij de bruggen worden gedaan volgens het Protocol van Schone Rivieren gebaseerd op OSPAR Beach Litter Monitoring Guidelines. De methodes worden gebruikt om te kwantificeren waar, hoe en wanneer zwerfafval en macroplastics worden getransporteerd in en door Rijkswateren. Vervolgens kan er door de metingen te vergelijken gekeken worden naar de veranderingen in drijvend afval over tijd, om zo ontwikkelingen en trends te kunnen signaleren. Om uitspraken te kunnen doen over zwerfafval en macroplastics in rivieren is het belangrijk om alles nauwkeurig te noteren en een juiste bemonsteringsstrategie en analysemethode te hanteren. Bovendien is het belangrijk om bewust te zijn van afwijkingen en dit meetprotocol geeft handvatten om deze te beperken. Ondanks dat de metingen relatief eenvoudig zijn, blijven ze arbeidsintensief. Hierdoor dienen kosten ook in overwegingen te worden meegenomen. Op dit moment laten de eerste resultaten van een pilot zien dat met behulp van deze betrekkelijk eenvoudige meetmethoden een goed gedetailleerd beeld kan worden gekregen van de hoeveelheid zwerfafvaltransport, de variatie over ruimte en tijd, en de samenstelling. Toekomstig onderzoek moet uitwijzen in hoeverre de metingen op deze manier kunnen worden blijven uitgevoerd, of dat metingen eventueel kunnen worden versimpeld of worden afgeschaald. De aanbeveling is om dit meetprotocol te gaan gebruiken in praktijksituaties, waarbij verschillende combinaties van methoden worden toegepast om drijvend zwerfafval te monitoren, en waarbij tevens de veranderingen in hydrologie en standplaatscondities worden gevolgd. Deze informatie is cruciaal voor het ontwerpen van een langetermijnstrategie voor zwerfafval en macroplastics in en rondom rivieren
Routekaart Zwerfafvalmonitoring Nederlandse rivieren
No full textZwerfafval in rivieren heeft een negatieve impact op mens en milieu. Een langetermijn monitoringstrategie zal bijdragen aan (1) beleid, (2) kennisontwikkeling, (3) operationele doelen en (4) evalueren van oplossingen. De Routekaart maakt de samenhang tussen doelen, openstaande vragen en projecten inzichtelijk, en helpt om concrete projecten te formuleren , prioriteren en evalueren. De Routekaart bestaat uit drie niveau’s : (1) meettechnieken, (2) nulmetingen, en (3) langetermijnmetingen . Deze fundamentele ontwikkelingen voeden op hun beurt de antwoorden op de grote vragen . Projectvoorstellen kunnen middels de Routekaart geprioriteerd worden, om een optimale volgorde van uitvoering te bepalen. De Routekaart kan aangepast worden naar aanleiding van nieuwe inzichten vanuit de grote vragen, nieuwe observaties, en technische ontwikkelingen. Door middel van een Dashboard kan direct inzichtelijk worden gemaakt hoe afgeronde projecten beschikbare methoden, kennis en kunde vergroten. De projecten gebundeld in zes clusters: Nieuwe Meettechieken , Meetprotocollen, Nationale Nulmeting, Langetermijnmonitoring, Samenwerking & Integratie, en Richtlijnen & Oplossingen. Specifieke projecten kunnen worden toegevoegd of verwijderd. De zes clusters zijn geplaatst op een tijdlijn als suggestie welke projecten prioriteit moeten krijgen op korte, middellange en lange termijn. De Routekaart is geen lineaire oplossing , maar biedt een flexibel raamwerk . Na nieuwe inzichten kan opnieuw de cyclus van doel vragen routes projecten clustering planning doorlopen worden. Ontwikkeling en optimalisatie van een nationale zwerfafvalmonitoringstrategie is een iteratief proce
Roadmap litter monitoring in Dutch rivers
No full textZwerfafval (marco-afval, >0.5 cm) in rivieren heeft een negatieve impact op de staat van ecosystemen en de menselijke leefomgeving. Betrouwbare monitoringsdata op nationale schaal is cruciaal voor het optimaliseren van preventie-, mitigatie- en opruimstrategieën. Zwerfafvalmonitoring is op dit moment gelimiteerd tot rivieroevers op nationale schaal, en ad hocprojecten op lokale schaal. In dit rapport presenteren wij een Routekaar voor een nationale monitoringstrategie voor zwerfafval in en rondom Nederlandse rivieren. De routekaart biedt een aantal handvatten om specifieke projecten te plannen, categoriseren en prioriteren. Deze zullen op hun beurt bijdragen aan het beantwoorden van de grote open vragen omtrent zwerfafvalmonitoring in rivieren
Diurnal differences in vegetation dielectric constant as a measure of water stress
No full textCurrently, vegetation is considered a barrier to soil moisture retrieval by both passive and active remote sensing missions. Microwave emission and backscattering of vegetation is driven by the vegetation dielectric constant, which is a function of vegetation water content. The latter is a measure of root zone water availability. Understanding the variation in dielectric properties of vegetation will contribute to soil moisture retrieval using microwaves in vegetated areas. This study presents a unique dataset of the diurnal pattern of the leaf dielectric properties, which was linked to vegetation water content and water stress. Using a microstrip line sensor, in-vivo dielectric property measurements were conducted on three maize leaves (leaf 8, 10 and 12) from 8 to 19 October 2012. A correlation was found between the resonant frequency of the microstrip line and the leaf water content of maize. This showed that a decrease of leaf water content during the day led to an increase of the resonant frequency. Water stress was quantified by calculating the evaporation deficit and by measuring the soil water tension at 30cm and 50cm depth. It was found that the diurnal difference in resonant frequency of the sensor at leaf 8 increased in similar fashion as the soil tension and evaporation deficit, which indicates a correlation between water stress and vegetation dielectric properties. The upper leaves 10 and 12 responded differently to increased water stress. The diurnal difference in resonant frequency of the sensor at leaf 10 and 12 decreased or was non-existent. The dielectric measurements revealed the complex reaction of vegetation to water stress and pointed out many opportunities for further research. The water-cloud model was used to demonstrate the impact of changing water content at different frequencies and polarizations. For L-,C-,X-,Ku- and Ka-band the sensitivity of radar backscatter to soil moisture and vegetation water content was modeled. This showed that at L-band, for low volumetric soil moisture (<0.2) vegetation is the main contributor to total backscatter. At higher frequencies backscatter was mainly sensitive to leaf water content. Time series analysis of modeled radar backscatter, based on field measurements of vegetation water content and soil moisture, showed that using the standard water-cloud model, the simulated diurnal difference in backscatter was small (0.05 dB). A modified water-cloud model was formulated that takes into account leaf and stalk water content separately. This model simulated a higher diurnal difference in backscatter (0.8 dB) and corresponded better to the trend in decreasing leaf water content and increasing water stress. This study presented interesting results that will hopefully stimulate follow up research projects. As a first step, it already revealed possibilities of using vegetation as an indicator for soil moisture, vegetation water status and water stress. The eventual possibilities of monitoring this at a global scale will lead to new innovative applications that will contribute to improving the state of the world.Water ResourcesWater ManagementCivil Engineering and Geoscience
- …
