Detecting and monitoring an unusual highly reflective plume from space in the Río de la Plata (Argentina)

GOSSN, J.I.; MOREIRA, D.; DOGLIOTTI, A.I.; SIMIONATO, C.G.

Shanghai

Congreso; ECSA 2017 Where Land Meets Ocean: The Vulnerable Interface; 2019

The Río de la Plata (RdP) river, located in the eastern coast of South America atapproximately 35 °S, carries high amounts of suspended particulate matter making thisestuary one of the most turbid in the world with mean concentrations of suspendedparticulate matter (SPM) ranging from 100 to 300 g m-3 and measured maximum valuesaround 1,000 g m-3. The high sediment concentration, as well as its distribution, has agreat impact on the different uses and functions of the RdP. The capital cities ofArgentina and Uruguay (Buenos Aires and Montevideo) are located in the respectivemargins of the river, being the main source of drinking water of Buenos Aires, as well asthe area of discharge of its domestic and industrial effluents. The dredging activity in theriver is very intense since access channels that allow the entry of ships from the AtlanticOcean to upstream ports need dredging with regularity. Therefore, water quality controlin this highly active and human impacted area is fundamental and the knowledge of itsdynamics as well as the particle size composition using remote sensing data is highlydesired and of great importance.From mid-May until the end of October 2016 a conspicuous feature has been detected inthe upper RdP estuary using remote sensing imagery, like Sentinel-2, Landsat-8, VIIRS,and MODIS sensors. This unusual plume had a different color in the RGB compositeappearing brighter and more yellow comparing to the adjacent waters. In September 25,2016 a field campaign was performed in the upper estuary and measurements wereperformed in and outside the plume. Water reflectance was measured and surface watersamples were collected for turbidity, SPM, and particle size distribution (PSD)determinations. In this study ocean color systems with different spectral and spatialresolutions have been used to detect the highly reflective plume during the May-October2016 period. Samples collected inside the striking plume showed different spectralcharacteristics, smaller median particle size, and turbidity (T) values ten times higher(T~500 FNU) than the surrounding waters. The variability of the T:SPM relationshipregarding the particle size was analyzed as well as the capability to detect differentparticle size using ocean colour satellite data.