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Suspended particulate matter concentration as a proxy for microplastics abundance in the Tamar estuary (UK): application to satellite remote sensing
Summary
Researchers developed and tested an Earth Observation method using satellite data to estimate microplastic concentrations in rivers by correlating them with suspended particulate matter measurements that satellites can detect from space. The approach was validated against field data from multiple rivers, showing reasonable predictive accuracy for plastic loads. If confirmed, this technique could enable monitoring of microplastic pollution in rivers at a global scale using existing satellite infrastructure.
Rivers flowing into the ocean have been identified as one of the largest contributors to the marine plastic pollution budget. However, much uncertainty remains over the spatio-temporal distribution of plastic pollution and the scale of fluxes entering the marine environment from river systems. This work aims to develop and validate a new Earth Observation (EO) approach to quantify the microplastic flux rates from rivers into coastal waters using satellite ocean colour data. The current methods available to quantify and monitor microplastic fluxes are based on localised, time and resource intensive in-situ sampling, laboratory analysis and modelling approaches. Previous EO approaches have focused primarily on floating macroplastic aggregation detection in the open ocean and relatively clear coastal waters. Microplastic concentrations are often not sufficiently high to change the water surface optical reflectance signal.. River mouths present additional challenges because the waters are often highly turbid and optically-complex, making it more difficult to accurately detect water constituent components. In light of these challenges, one possible approach to quantify microplastic discharge from rivers is to use an indirect detection method where optically active substances derived from medium resolution optical satellite imagery, like suspended particulate matter (SPM), are used to estimate microplastic concentrations. This study presents the results from an in situ sampling campaign in the estuary at the mouth of the river Tamar (UK). In situ SPM is correlated to microplastic concentrations (100µm¿D¿2.5cm). This relationship is used to produce microplastic proxy concentration and, with river gauge data, a time-varying microplastic discharge estimate for this river system is calculated. The methodology for the microplastic discharge quantification and preliminary results will be presented, discussing the assumptions it makes and the advantages and limitations of the approach. Also see: https://micro2022.sciencesconf.org/427179/document