Surface microlayers

Because of their hydrophobic nature, siUcones entering the aquatic environment should be significantly absorbed by sediment or migrate to the air—water interface. SiUcones have been measured in the aqueous surface microlayer at two estuarian locations and found to be comparable to levels measured in bulk (505). Volatile surface siloxanes become airborne by evaporation, and higher molecular weight species are dispersed as aerosols. 

Hardy, J. T., Apts, C. W., Crecelius, E. A. and Fell-ingham, G. W. (1985). The sea-surface microlayer fate and residence times of atmospheric metals. Limnol. Oceanog. 30, 93-101. 

Maguire RJ, Kuntz KW, Hale EJ. 1983. Chlorinated hydrocarbons in the surface microlayer of the Niagara River. J Great Lakes Res 9 281-286. 

Heussner S, Cherry RD, Heyraud M (1990) Po-210 and Pb-210 in sediment trap particles on a Mediterranean continental margin. Cont. Shelf Res 10 989-100 Heyraud M, Cherry RD (1983) Correlation of Po-210 and Pb-210 enrichments in the sea-surface microlayer with neuston biomass. Cont Shelf Res 1 283-293 Honeyman BD, Santschi PH (1989)The role of particles and colloids in the transport of radionuclides and trace metals in the oceans. In Environmental particles. Buffle J, van Leewen HP (eds) Lewis Publishers, Boca Raton, p 379-423... 

Diisopropyl methylphosphonate is slightly soluble in water (0.1—0.3 g/L at 25°) and has been demonstrated in laboratory studies to quickly diffuse between the surface microlayer into the water column after deposition as aerosols on fresh water (Van Voris et al. 1987). The solubility of diisopropyl methylphosphonate was 80 g/L (8%) and remained in solution even when the temperature was lowered to freezing (Bucci et al. 1997). In addition, there was no significant loss of diisopropyl methylphosphonate from the water column to the atmosphere, in either the presence or absence of a light wind over the water surface. Human exposure resulting from the vaporization of diisopropyl methylphosphonate from surface water is considered insignificant (EPA 1989). 

Determination of the persistence and mobility of organotin compounds — especially in aquatic abiotic materials, such as sediments, sediment interstitial waters, suspended particulates, and the water column — and on the partitioning of these compounds between the surface microlayer and subsurface waters (Wilkinson 1984 Thompson et al. 1985). 

Cleary, J.J. and A.R.D. Stebbing. 1987. Qrganotin in the surface microlayer and subsurface waters of southwest England. Mar. Pollut. Bull. 18 238-246. 

All but the most heavily contaminated fresh and marine waters contain total PAH concentrations in the part-per-trillion or low part-per-billion range (Table 25.3) (Neff 1982b). A large proportion of the PAH content in water is probably adsorbed onto suspended solids (Harrison et al. 1975). In Lake Michigan, concentrations of total PAHs in the surface microlayer varied from 0.15 to 0.45 pg/L, representing on a relative scale, 106 times the concentration in air, suggesting that aerosols are a major source of these compounds and that the microlayer is a repository until the PAHs are removed by adsorption and sedimentation (Strand and Andren 1980). 

Consequently, for an accurate quantification of surfactants in the water column, sampling must be performed by taking surface microlayer samples (at depths between 0 and 3—5 mm), using a surface sampler, and at various greater depths with Ruttner or similar bottles. 

The proportion of long-chain LAS homologues is greater in the solid phase (solids in suspension and sediment) than in water and greater than in commercial LAS. For LAS clear vertical trends in distribution can be observed both in the water and sediment columns, with relatively enriched concentrations in the surface microlayer and sediment top layers. 

Booij, K. and van Drooge, B.L. 2001, Polychlorinated biphenyls andhexachlorobenzene in atmosphere, sea-surface microlayer, and water measured widi semi-permeable membrane devices (SPMDs). Chemosphere 44 91—98. 

Garabetian, R Romano, J.-C. Paul, R. Sigoillot, J.-C. 1993, Organic matter composition and pollutant enrichment of sea surface microlayer inside and outside slicks. Mar. Environ. Res. 35 323-339. 

Hardy, J.T. Coley, J.A. Antrim, L.D. Kiesser, S.L. 1988, A hydrophobic large-volume sampler for collecting aquatic surface microlayers Characterization and comparison with the glass plate method. Can. J. Fish. Aquat. Sci. 45 822-826. 

Hardy, J.T. and Cleary, J. 1992, Surface microlayer contamination and toxicity in the German Bight. Mar. Ecol. Prog. Ser. 91 203-210. 

Gearing PJ, Gearing IN. 1982b. Transport of no. 2 fuel oil between water column, surface microlayer and atmosphere in controlled ecosystems. Marine Environmental Research 6(2) 133-143. 

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