engleski

Characterization of Marine Aerosols at the highly Eutrophic Seawater Ecosystem Rogoznica Lake in Central Dalmatia

In the frame of the project „The Sulphur and Carbon Dynamics in the Sea- and Fresh-water Environment“(SPHERE)“, funded by Croatian science foundation we are studying sulphur (S) and carbon (C) dynamics between different environmental compartments (atmosphere, water, sediment, biota) of the sea- and fresh-water environment. A main focus is on distribution between organic, inorganic, dissolved, colloidal and nanoparticulate fraction. Important part of the project is focused on characterization of marine and freshwater aerosols mainly by electrochemical, chromatographic and ICPMS methods. Marine aerosols play a dominant role in the transfer of oceanic material to the atmosphere. Most marine aerosol originates when air bubbles burst at the sea surface ejecting material from the sea surface microlayer (SSM) and bubble surface layers into the air. Concentrations of chemical compounds in these surface layers often differ from their concentrations in bulk water. The unique, highly eutrophic, and euxinic (anoxic water with free hydrogen sulphide in the water column) marine lake system Rogoznica Lake in the central Dalmatia (Middle Adriatic, 43o 32’N 15o 58’E) was selected as one of the important study sites. Rogoznica Lake is considered as an extreme, naturally eutrophic system which feels all effects of the Adriatic atmospheric and ocean conditions (1). Influence of these conditions due to the lake semi-closed nature might be several times stronger than in other coastal and open sea Adriatic waters. Extremely fluctuating environmental conditions such is high seasonal variations in salinity and temperature, water stratification with strong redox gradient and euxinia accompanied by high concentrations and variability of nutrients on one side and episodic appearance of holomixis with hypoxia and anoxia conditions on the other side, highly influence the lake ecosystem. In order to get better insights into aerosol characteristics and dynamics between the atmosphere and the lake marine system this study is designed to comprise seasonal data of the marine aerosols as well as the sea surface microlayer (SML) and underlaying water samples (ULW, from 0.5 m depth) at the Rogoznica Lake. The aerosol samples (aerodynamic diameter <2.5 μm) were collected on the glass fiber GF/F filters (φ=47 mm) by low volume sampler (2.3 m3 /h, sampling time: 24 h). The SML samples were collected by the Garrett screen method using the stainless steel screen. Isolation and physico- chemical characterization of the water soluble organic matter(WSOM) from aerosol, SML and ULW samples were conducted by mainly electrochemical methods for surface active substances (2, 3) and reduced sulphur species determination (4), in combination with measurements of total and dissolved organic carbon (TOC, DOC) by high temperature catalytic oxidation (HTCO) technique and trace metals by ICPMS measurements. The first preliminary results from winter and spring seasons will be presented.

marine aerosols ; sea surface microlayer

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