Elsevier

Marine Chemistry

Volume 76, Issues 1–2, October 2001, Pages 77-98
Marine Chemistry

Organic pollutants in sea-surface microlayer and aerosol in the coastal environment of Leghorn—(Tyrrhenian Sea)

https://doi.org/10.1016/S0304-4203(01)00049-4Get rights and content

Abstract

The levels of dissolved and particle-associated n-alkanes, alkylbenzenes, phthalates, PAHs, anionic surfactants and surfactant fluorescent organic matter (SFOM) were measured in sea-surface microlayer (SML) and sub-surface water (SSL) samples collected in the Leghorn marine environment in September and October 1999.

Nine stations, located in the Leghorn harbour and at increasing distances from the Port, were sampled three times on the same day. At all the stations, SML concentrations of the selected organic compounds were significantly higher than SSL values and the enrichment factors (EF=SML concentration/SSL concentration) were greater in the particulate phase than in the dissolved phase.

SML concentrations varied greatly among the sampling sites, the highest levels (n-alkanes 3674 μg/l, phthalates 177 μg/l, total PAHs 226 μg/l) being found in the particulate phase in the Leghorn harbour.

To improve the knowledge on pollutant exchanges between sea-surface waters and atmosphere, the validity of spray drop adsorption model (SDAM) was verified for SFOM, surface-active agents, such as phthalates, and compounds which can interact with SFOM, such as n-alkanes and PAHs.

Introduction

During the last decades many investigations have been conducted on the physical properties and chemical composition of the sea-surface microlayer (SML) as well as on exchange processes at the air/sea interface GESAMP, 1995, Liss and Duce, 1997, CIESM Workshop, 1999. These studies have highlighted that a wide variety of natural and anthropogenic contaminants concentrate in the SML because of their surfactant nature, hydrophobic properties, possible association with floatable particles, vertical diffusion mechanisms or bubbles scavenging. The transfer of such materials from the sea-surface to the atmosphere may take place through the volatilisation due to their high vapour tension, the stripping by the bubbles and the formation of wind-generated aqueous aerosols Wallace and Duce, 1978, Hardy, 1982, Buat-Ménard, 1983, Blanchard, 1989, Cini et al., 1994a, Lepri et al., 1995, Gustafson and Dickhut, 1997. In fact, when air bubbles burst at the sea-surface they generate an aerosol which is contaminated and enriched with material scavenged from the sea-surface microlayer and the water column Blanchard, 1975, Tseng et al., 1992. Several studies Blanchard, 1983, Liss and Duce, 1997 have shown that bacteria and viruses in aerosol particles have concentrations significantly higher than those obtained in the bulk-water from which they were generated. Analogous results were found for lipids Gagosian, 1986, Simò et al., 1991 and surfactants Blanchard, 1964, Garrett, 1967 transported via marine aerosol to the coastal regions where hazardous effects on animals and vegetation Giovannelli et al., 1989, Bussotti et al., 1995, together with toxic effects on human health (WHO, 1998), have been observed. In addition, high concentrations of toxic metals Hoffmann et al., 1974, Hunter, 1980, Hardy et al., 1985 and organic pollutants Williams et al., 1986, Hardy et al., 1987, Cross et al., 1987, Sauer et al., 1989, Hardy et al., 1990 have been found in the SML compared to the sub-surface water (SSL) throughout various coastal environments. However, a few investigations have been carried out on the characterisation of organic pollutants in the SML of Mediterranean waters (CIESM Workshop, 1999).

To this end, aliphatic and aromatic hydrocarbons and phthalates have been determined in SML, SSL and aerosol samples collected in the Tyrrhenian Sea near Leghorn. Size fractionated aerosol samples were collected to provide more information on air–sea processes, as well as verify the validity of Spray Drop Adsorption Model (SDAM) (Oppo et al., 1999). Moreover, the compounds measured were particularly useful for evaluating the degree of marine pollution because alkylbenzenes, phthalates and PAHs enter the marine environment only by anthropogenic sources, while n-alkanes may have biogenic and/or anthropogenic origin.

Section snippets

SML and SSL

SML and SSL samples were collected between September and October 1999 at nine different sites in the Tyrrhenian Sea, near Leghorn and Gorgona island. Table 1 gives some information about the sampling sites including location, water depth, distance from the coast, temperature and pH.

Our sampling strategy included stations in areas believed to receive different amounts of pollutants in order to have a representative picture of sea surface contamination in the investigated zone (Fig. 1). SML and

SML and SSL samples

Table 2 reports the mean concentrations, expressed in μg/l, of individual n-alkanes, phthalates, PAHs and alkylbenzenes found in the SML samples and in their related underlying water collected at Quercianella (station 3). Such compounds represent almost all the organic substances extractable with n-hexane or n-hexane-methylene chloride (1:1 v/v).

Dissolved n-alkanes in SML exhibit a different distribution with respect to the particulate hydrocarbons, which reflects the probable loss of low

SML and SSL

Aliphatic hydrocarbons, alkylbenzenes, PAHs, phthalates, anionic surfactants and SFOM were found to be present in the surface film and the underlying water of all the samples. Hydrocarbons concentrate in the particulate phase according to their hydrophobic properties with the exception of alkylbenzenes which have been only detected in the dissolved phase at very low amounts. This behaviour seems to be general and not connected to the pollution level of the investigated sampling site, and

Concluding remarks

The results give a picture of aquatic surface contamination in a coastal zone of the Tyrrhenian sea, near Leghorn, during September–October 1999. Signals of pollution from chemicals of petrogenic origin are evident in SML samples collected in the harbour of Leghorn and at various distances from the Port.

The SML is enriched with n-alkanes, phthalates, PAHs, suspended matter and SFOM with respect to sub-surface waters. The presence of slicks gives rise to unusual dissolved concentrations of these

Acknowledgements

This study was supported by the University of Florence through the National Project “The development of innovative analytical methods for the study of environmental matrices”.

Many thanks to the Director of the Inter University Center of Marine Biology and of the Municipal Aquarium of Leghorn for their hospitality and logistic assistance. We greatly thank Prof. R. Udisti for sodium ion analysis.

References (73)

  • L. Lepri et al.

    Transport of organochlorine pesticides across the air/sea interface during the aerosol process

    Anal. Chim. Acta

    (1995)
  • J.L.A. Long et al.

    Micro-organic compounds associated with sediments in the Humber rivers

    Sci. Total Environ.

    (1998)
  • J.C. Marty et al.

    Hydrocarbons (normal alkanes) in the surface microlayer of sea-water

    Deep-Sea Res.

    (1976)
  • J.C. Marty et al.

    Organic matter characterization in the Northern Adriatic Sea with special reference to the sea surface microlayer

    Mar. Chem.

    (1988)
  • C. Oppo et al.

    Surfactant components of marine organic matter as agents for biogeochemical fractionation and pollutant transport via marine aerosol

    Mar. Chem.

    (1999)
  • M.R. Preston et al.

    Phthalate ester speciation in estuarine water, suspended particulates and sediments

    Environ. Poll.

    (1989)
  • D. Rumbold et al.

    Sea-surface microlayer toxicity off the Florida Keys

    Mar. Environ. Res.

    (1999)
  • T.C. Sauer et al.

    Concentrations of chlorinated pesticides and PCBs in microlayer and sea-water samples collected in open-ocean waters off the U.S. East Coast and in the Gulf of Mexico

    Mar. Chem.

    (1989)
  • M.A. Sicre et al.

    Aliphatic aromatic hydrocarbons in different sized aerosols over the Mediterranean Sea: occurrence and origin

    Atmos. Environ.

    (1987)
  • A. Turner et al.

    The behaviour of di-(2-ethylhexyl)phthalate in estuaries

    Mar. Chem.

    (2000)
  • M. Vitali et al.

    Phthalate esters in freshwaters as markers of contamination sources a site study in Italy

    Environ. Int.

    (1997)
  • P.M. Williams et al.

    Chemical and microbiological studies of sea-surface films in the southern Gulf of California and off the west coast of Baja California

    Mar. Chem.

    (1986)
  • D.C. Blanchard

    Sea-to-air transport of surface active material

    Science

    (1964)
  • D.C. Blanchard

    Bubble scavenging and the water-to-air transfer of organic material in the sea

    Adv. Chem. Ser.

    (1975)
  • D.C. Blanchard

    The production, distribution and bacterial enrichment of the sea-salt aerosol

  • D.C. Blanchard

    The ejection of drops from the sea and their enrichment with bacteria and other materials: a review

    Estuaries

    (1989)
  • P. Buat-Ménard

    Particle geochemistry in the atmosphere and oceans

  • F. Bussotti et al.

    The role of marine salt and surfactants in the decline of Tyrrhenian coastal vegetation in Italy

    Ann. Sci. For.

    (1995)
  • S.S. Butcher et al.
  • CIESM Workshop, 1999. Role of sea surface microlayer processes in the biogeochemistry of the Mediterranean Sea, Paris,...
  • R. Cini et al.

    Spectrofluorimetric evidence of the transport of marine organic matter in Antarctic snow via air–sea interaction

    Int. J. Environ. Anal. Chem.

    (1994)
  • Comes, R., Ventajas, L., Kocmur, S., 1987. Hydrocarbons polinucleares en el Mar de Weddell. Primer Symposium Espanol de...
  • G.C. Cripps

    Hydrocarbons in the seawater and pelagic organisms of the Southern Ocean

    Polar. Biol.

    (1990)
  • J.N. Cross et al.

    Contaminant concentrations and toxicity of sea-surface microlayer near Los Angeles, California

    Mar. Environ. Res.

    (1987)
  • Degli Innocenti, N., 1993. Le sostanze umiche nell'ambiente marino: aspetti chimico-fisici. PhD thesis in Environmental...
  • P.G. Desideri et al.

    Recovery identification and determination of organic compounds in marine sediments

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