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Open accessJournal ArticleDOI: 10.5194/ESSD-13-713-2021

Hyperspectral-reflectance dataset of dry, wet and submerged marine litter

02 Mar 2021-Earth System Science Data (Copernicus GmbH)-Vol. 13, Iss: 2, pp 713-730
Abstract: . This paper describes a dataset consisting of 47 hyperspectral-reflectance measurements of plastic litter samples. The plastic litter samples include virgin and real samples from the Port of Antwerp. They were measured in dry conditions in the Flemish Institute for Technological Research (VITO) calibration facility, and a selection of the samples were also measured in wet conditions and submerged in a water tank at Flanders Hydraulics. The construction on top of the tank allowed us to submerge the plastics and keep sediments in suspension. The spectral measurements were performed using an Analytical Spectral Devices (ASD) FieldSpec 4 and a Spectral Evolution (SEV) spectrometer. The datasets are available on the 4TU.ResearchData open-access repository (ASD dataset: https://doi.org/10.4121/12896312.v2 , Knaeps et al., 2020; SEV dataset: https://doi.org/10.4121/uuid:9ee3be54-9132-415a-aaf2-c7fbf32d2199 ; Garaba et al., 2020).

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6 results found


Open accessJournal ArticleDOI: 10.1038/S41598-021-84867-6
08 Mar 2021-Scientific Reports
Abstract: While at least 8 million tons of plastic litter are ending up in our oceans every year and research on marine litter detection is increasing, the spectral properties of wet as well as submerged plastics in natural marine environments are still largely unknown. Scientific evidence-based knowledge about these spectral characteristics has relevance especially to the research and development of future remote sensing technologies for plastic litter detection. In an effort to bridge this gap, we present one of the first studies about the hyperspectral reflectances of virgin and naturally weathered plastics submerged in water at varying suspended sediment concentrations and depth. We also conducted further analyses on the different polymer types such as Polyethylene terephthalate (PET), Polypropylene (PP), Polyester (PEST) and Low-density polyethylene (PE-LD) to better understand the effect of water absorption on their spectral reflectance. Results show the importance of using spectral wavebands in both the visible and shortwave infrared (SWIR) spectrum for litter detection, especially when plastics are wet or slightly submerged which is often the case in natural aquatic environments. Finally, we demonstrate in an example how to use the open access data set driven from this research as a reference for the development of marine litter detection algorithms.

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Topics: VNIR (53%)

10 Citations


Open accessJournal ArticleDOI: 10.3390/RS13122335
15 Jun 2021-Remote Sensing
Abstract: Airborne and spaceborne remote sensing (RS) collecting hyperspectral imagery provides unprecedented opportunities for the detection and monitoring of floating riverine and marine plastic debris. However, a major challenge in the application of RS techniques is the lack of a fundamental understanding of spectral signatures of water-borne plastic debris. Recent work has emphasised the case for open-access hyperspectral reflectance reference libraries of commonly used polymer items. In this paper, we present and analyse a high-resolution hyperspectral image database of a unique mix of 40 virgin macroplastic items and vegetation. Our double camera setup covered the visible to shortwave infrared (VIS-SWIR) range from 400 to 1700 nm in a darkroom experiment with controlled illumination. The cameras scanned the samples floating in water and captured high-resolution images in 336 spectral bands. Using the resulting reflectance spectra of 1.89 million pixels in linear discriminant analyses (LDA), we determined the importance of each spectral band for discriminating between water and mixed floating debris, and vegetation and plastics. The absorption peaks of plastics (1215 nm, 1410 nm) and vegetation (710 nm, 1450 nm) are associated with high LDA weights. We then compared Sentinel-2 and Worldview-3 satellite bands with these outcomes and identified 12 satellite bands to overlap with important wavelengths for discrimination between the classes. Lastly, the Normalised Vegetation Difference Index (NDVI) and Floating Debris Index (FDI) were calculated to determine why they work, and how they could potentially be improved. These findings could be used to enhance existing efforts in monitoring macroplastic pollution, as well as form a baseline for the design of future multispectral RS systems.

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Topics: Hyperspectral imaging (55%), Multispectral image (55%), Spectral signature (54%) ... read more

3 Citations


Open accessJournal ArticleDOI: 10.1186/S43591-021-00014-Y
Abstract: A central challenge in microplastics (MP, diameter 250 μm, with drastic improvements in analysis time as compared with the best available technology, such as Fourier transform infrared (FT-IR) and Raman spectroscopy. Primary challenges we identified through the review include improving spatial resolution to detect smaller MP and development of robust models for data analysis. Parameters and practices for reporting quality assurance and quality control measures are summarized and recommendations are made for future research. We conclude that HSI is a promising technology for MP analysis but requires adaptation for this new application.

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2 Citations


Open accessJournal ArticleDOI: 10.1364/OE.440380
25 Oct 2021-Optics Express
Abstract: We present a direct and proxy-based approach to qualitatively and semi-quantitatively observe floating plastic litter in the Great Pacific Garbage Patch (GPGP) based on a survey in 2018 using very high geo-spatial resolution 8-waveband WorldView-3 imagery. A proxy for the plastics was defined as a waveband difference for anomalies in the top-of-the-atmosphere spectra. The anomalies were computed by subtracting spatially varying reflectance of the surrounding ocean water as background from the top-of-the-atmosphere reflectance. Spectral shapes and magnitude were also evaluated using a reference target of known plastics, The Ocean Cleanup System 001 Wilson. Presence of ‘suspected plastics’ was confirmed by the similarity in derived anomalies and spectral shapes with respect to the known plastics in the image as well as direct observations in the true color composites. The proposed proxy-based approach is a step towards future mapping techniques of suspected floating plastics with potential operational monitoring applications from the Sentinel-2 that recently started regular imaging over the GPGP that will be supported or validated by numerical solutions and net trawling survey.

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Open accessJournal ArticleDOI: 10.3390/RS13224548
12 Nov 2021-Remote Sensing
Abstract: Marine plastic debris (MPD) is a globally relevant environmental challenge, with an estimated 8 million tons of synthetic debris entering the marine environment each year. Plastic has been found in all parts of the marine environment, including the surface layers of the ocean, within the water column, in coastal waters, on the benthic layer and on beaches. While research on detecting MPD using remote sensing is increasing, most of it focuses on detecting floating debris in open waters, rather than detecting MPD on beaches. However, beaches present challenges that are unique from other parts of the marine environment. In order to better understand the spectral properties of beached MPD, we present the SWIR reflectance of weathered MPD and virgin plastics over a sandy substrate. We conducted spectral feature analysis on the different plastic groups to better understand the impact that polymers have on our ability to detect synthetic debris at sub-pixel surface covers that occur on beaches. Our results show that the minimum surface cover required to detect MPD on a sandy surface varies between 2–8% for different polymer types. Furthermore, plastic composition affects the magnitude of spectral absorption. This suggests that variation in both surface cover and polymer type will inform the efficacy of beach litter detection methods.

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Topics: Plastic pollution (53%), Debris (52%)

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6 results found


Open accessJournal ArticleDOI: 10.1016/0022-2860(95)08609-Y
Th. Huth-Fehre, Roger Feldhoff, Th. Kantimm, L. Quick  +6 moreInstitutions (1)
Abstract: An imaging spectrometer with a 256 element InGaAs diode array was combined with a high throughput optical arrangement for recording high quality NIR spectra (824 nm to 1700 nm) of plastics from a distance of 25 cm within 6.3 milliseconds. The considered spectral region was assessed to be suitable for plastic identification.

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Topics: Imaging spectrometer (52%)

64 Citations


Open accessJournal ArticleDOI: 10.5281/ZENODO.1076916
Abstract: In this paper, an automated system is presented for identification and separation of plastic resins based on near infrared (NIR) reflectance spectroscopy. For identification and separation among resins, a \"Two-Filter\" identification method is proposed that is capable to distinguish among polyethylene terephthalate (PET), high density polyethylene (HDPE), polyvinyl chloride (PVC), polypropylene (PP) and polystyrene (PS). Through surveying effects of parameters such as surface contamination, sample thickness, label and cap existence, it was obvious that the \"Two-Filter\" method has a high efficiency in identification of resins. It is shown that accurate identification and separation of five major resins can be obtained through calculating the relative reflectance at two wavelengths in the NIR region. Keywords—Identification, Near Infrared, Plastic, Separation, Spectroscopy

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Topics: Spectroscopy (53%)

55 Citations


Open accessJournal ArticleDOI: 10.1016/J.RSE.2015.06.022
Els Knaeps1, Kevin Ruddick, David Doxaran2, Ana I Dogliotti3  +3 moreInstitutions (3)
Abstract: In ocean colour remote sensing, the use of Near Infra Red (NIR) spectral bands for the retrieval of Total Suspended Matter (TSM) concentration in turbid and highly turbid waters has proven to be successful. In extremely turbid waters (TSM > 100 mg L − 1 ) however, these bands are less sensitive to increases in TSM. Here it is proposed to use Short Wave Infra Red (SWIR) spectral bands between 1000 and 1300 nm for these extreme cases. This SWIR spectral region is subdivided into two regions, SWIR-I (1000 nm to 1200 nm) and SWIR-II (1200 nm to 1300 nm) which correspond to local minima in the pure water absorption spectrum. For both spectral regions the water reflectance signal was measured in situ with an ASD spectrometer in three different extremely turbid estuarine sites: Scheldt (Belgium), Gironde (France), and Rio de la Plata (Argentina), along with the TSM concentration. A measurable water reflectance was observed for all sites in SWIR-I, while in the SWIR-II region the signal was not significant compared to the Signal-to-Noise Ratio (SNR) of current Ocean Colour (OC) sensors. For the spectral band at 1020 nm (present in Ocean and Land Colour Instrument — OLCI, onboard Sentinel-3) and at 1071 nm, an empirical single band TSM algorithm is defined which is valid for both the Gironde and Scheldt estuarine sites. This means that a single algorithm can be applied for both sites without expensive recalibration. The relationship between TSM and SWIR reflectance at 1020 and 1071 nm is linear and did not show any saturation for the concentrations measured here (up to 1400 mg L − 1 ), while saturation was observed for the NIR wavelengths, as expected. Hence, for extremely turbid waters it is advised to switch from NIR to SWIR-I wavelengths to estimate TSM concentration. This was demonstrated for an airborne hyperspectral dataset (Airborne Prism Experiment, APEX) from the Gironde estuary having several spectral bands in the SWIR-I. The empirical single band SWIR TSM algorithm was applied to the atmospherically corrected scene providing a TSM concentration map of the Gironde from mouth to more upstream with concentrations expected in this region ranging from a few to several hundreds mg L − 1 . These results, i.e. the existence of a single relationship for the Scheldt and Gironde, not showing any decrease of sensitivity, highlights the importance of having SWIR bands in future ocean colour sensors for studying extremely turbid rivers, coastal areas and estuaries in the world. A further implication of these results is that there is a TSM limit for application of atmospheric correction algorithms which assume zero SWIR marine reflectance. That limit is defined here as function of wavelength and sensor noise level.

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Topics: Spectral bands (53%)

55 Citations


Journal ArticleDOI: 10.1109/TGRS.2012.2185055
Abstract: Accurately determining field-of-view has rarely been considered in field spectroscopy where specifications for fore optics used are generally limited and the influence of the spectroradiometer rarely considered. The issue can be compounded with full wavelength spectroradiometric systems which include multiple spectrometers. In these systems, the size and alignment of the viewing optics and technology adopted to transfer light from the fore optic to individual spectrometers may cause significant nonuniformity of spectral response across the area of measurement support, and this area may not align with that assumed from the specification that is supplied for the fore optic. When recording spectra from heterogeneous earth surface targets, it is important to have the area of measurement support accurately defined as individual reflecting surfaces may be present in varying proportions within this area, and these proportions need to be determined to relate spectral reflectance or spectral radiance to state variables or target classifications being considered. The area of measurement support and the spatial and spectral responsivity of an ASD Field Spec Pro FR spectroradiometer and a SVC GER 3700 spectroradiometer have been determined by measuring the directional response function (DRF) of each instrument. This research highlights several areas of concern and makes recommendations for the improvement of field spectroradiometers and field spectroscopy methodologies. These results are specific to the spectroradiometer/fore optic combinations investigated and at the measurement distances specified. Although similar characteristics can be expected for other instruments/fore optics of the same design, and at other measurement distances, the DRFs will vary from those reported here.

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Topics: Spectroradiometer (57%), Radiance (50%)

53 Citations


Open accessJournal ArticleDOI: 10.5194/ESSD-12-77-2020
Abstract: . Combating the imminent environmental problems associated with plastic litter requires a synergy of monitoring strategies, clean-up efforts, policymaking and interdisciplinary scientific research. Lately, remote sensing technologies have been evolving into a complementary monitoring strategy that might have future applications in the operational detection and tracking of plastic litter at repeated intervals covering wide geospatial areas. We therefore present a dataset of Lambertian-equivalent spectral reflectance measurements from the ultraviolet (UV, 350 nm) to shortwave infrared (SWIR, 2500 nm) of synthetic hydrocarbons (plastics). Spectral reflectance of wet and dry marine-harvested, washed-ashore, and virgin plastics was measured outdoors with a hyperspectral spectroradiometer. Samples were harvested from the major accumulation zones in the Atlantic and Pacific oceans, suggesting a near representation of plastic litter in global oceans. We determined a representative bulk average spectral reflectance for the dry marine-harvested microplastics dataset available at https://doi.org/10.21232/jyxq-1m66 (Garaba and Dierssen, 2019c). Similar absorption features were identified in the dry samples of washed-ashore plastics: dataset available at https://doi.org/10.21232/ex5j-0z25 (Garaba and Dierssen, 2019a). The virgin pellets samples consisted of 11 polymer types typically found in floating aquatic plastic litter: dataset available at https://doi.org/10.21232/C27H34 (Garaba and Dierssen, 2017). Magnitude and shape features of the spectral reflectance collected were also evaluated for two scenarios involving dry and wet marine-harvested microplastics: dataset available at https://doi.org/10.21232/r7gg-yv83 (Garaba and Dierssen, 2019b). Reflectance of wet marine-harvested microplastics was noted to be lower in magnitude but had similar spectral shape to that of dry marine-harvested microplastics. Diagnostic absorption features common in the marine-harvested microplastics and washed-ashore plastics were identified at ∼931 , 1215, 1417 and 1732 nm. In addition, we include metrics for a subset of the marine-harvested microplastics related to particle morphology, including sphericity and roundness. These datasets are also expected to improve and expand the scientific evidence-based knowledge of optical characteristics of common plastics found in aquatic litter. Furthermore, these datasets have potential use in radiative transfer simulations exploring the effects of plastics on ocean colour remote sensing and developing algorithms applicable to remote detection of floating plastic litter.

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Topics: Microplastics (58%)

19 Citations