Surface-active properties of organic matter in the North Adriatic Sea

Abstract

Characterization of surface-active organic substances has been performed in the North Adriatic Sea, in surface and bottom layers, during the year 2000. Surfaceactive substances (SAS), their hydrophobicity and acidity, were estimated with alternating current voltammetry (in-phase mode) using o-nitrophenol as an electrochemical probe. Depending on hydrophobicity and acidity of present SAS electrochemical characteristics of the o-nitrophenol probe are changing in a specific way. Normalization of the change of prepeak height as an indication of organic matter acidity to shift of peak potential as a measure of hydrophobicity give indication of relative acidity of present SAS. Experiment with model substances showed that humic and fulvic acids contribute the highest to the relative acidity, while biogenic surface-active organic substances as proteins, polysaccharides and lipids contribute lower to the relative acidity.Surface water layer is characterized with higher phytoplankton excretion during whole year concluded from higher contribution of biogenic organic substances to surfactant activity. Humic and fulvic substances dominate in surfactant activity in the bottom layer. Proteinaceous material is found in a heterodispersed fraction during supposed phytoplankton blooms that were in March, July, September and even December, in the Northern Adriatic, connected to unexpectedly high temperatures. Surfactant activity of particulate fraction was found to be mainly less than 10 %. Exceptions were obtained in April and October when surfactant activity of particulate fraction contributed up to 55 and 20 %, respectively. 2

Organic matter characterization in Barents Sea and eastern Arctic Ocean during summer

“…Increased SAS"p" have been mainly found during the period of increased phytoplankton activity (Gašparović and Ćosović, 2003). It is interesting to note that in the Barents Sea the increased contribution of SAS"p" to the SAST was found mostly in the UML and only The surface-active organic matter in the polar region investigated was characterized by increasing hydrophilicity with the depth (Table 3).…”

“…The increased concentration of SAS in the euphotic layer is often related to the new phytoplankton community production (Gašparović and Ćosović, 2003;Gašparović et al, 2005) but it may originate from other sources. For example the SAS may be a relict from previous blooms resulting from protozoan grazing on phytoplankton (Kujawinski et al 2002).…”

“…concentration of T-X-100). Relative acidity is an arbitrary unit of acidity per surfactant activity (l mg -1 ) (Gašparović and Ćosović, 2003). The results were elaborated for total SAS (SAST), dissolved SAS (SASdiss) and the difference between the concentration of total SAS and SAS ( SAS"p".).…”

“…showed that biogenic SAS such as polysaccharides, proteins and lipids, contribute less to the ) (Gašparović and Ćosović, 2003). (Gašparović et al, 2005) and for the temperate seawaters in the Mediterranean, 7.7 -29.5 l mg -1 (Gašparović, unpublished data).…”

Distribution of surfactants in sea-surface microlayer and atmospheric aerosols at selected coastal area of Peninsular Malaysia

“…As for natural sources, sea-salt compositions originated from sea-surface microlayer (SML) could play a significant role in forming natural surfactants [4]. In addition, phytoplankton excretion and biodegradation of organic substances may have connection to the production of surfactants in SML [5][6].…”