COMBINING IN SITU AND MULTI-SENSOR SATELLITE DATA TO ASSESS THE IMPACT OF ATMOSPHERIC DEPOSITION IN LAKE GARDA

摘要

In this study we investigated the effect of the depositionrnof Saharan dust on the phytoplankton growth (i.e. dustrnfertilization hypothesis) in Lake Garda, an oligotrophicrnbasin with low nutrient and low chlorophyll-a (chl-a)rnconcentration, by combining satellite data with in siturnmeasurements. A Saharan dust event has beenrnrecognised on 28/07/2005 by: (ⅰ) SEVIRI (SpinningrnEnhanced Visible and InfraRed Imager) datarnprocessing, (ⅱ) a significant increase of PM10 withrnrespect to PM2.5 in a site southern the lake; and (ⅲ) thernhigh values of AOT (aerosol optical thickness) withrncorresponding low values of the Angstrom parameterrnmeasured by AERONET in Ispra. Few days later, anrnincrease of chl-a in the lake was detected from MERISrn(Medium Resolution Imaging Spectrometer). Thernimages were processed with the Case-2 Regional (C2R)rnprocessor that provided values comparable to in siturnmeasurements (r=0.78). Therefore, preliminary resultsrnseem to indicate a response of the Lake Garda in termsrnof increasing of chl-a as a consequence of the Saharanrndust event recognised on 28/07/2005. Nevertheless, thernanalysis of further events is mandatory in order to havernconfirmation (or no), about the linkage betweenrnatmospheric deposition and phytoplankton dynamics inrnthe study area.