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Interfaces in aquatic ecosystems: Implications for transportand impact of anthropogenic compounds

Johannes Knulst FK, Sm

Akademisk avhandling, som for avlaggande av filosofie doktorsexamen vid matematisk- naturvetenskapliga fakulteten vid Lunds Universitet, kommer att offentligen forsvaras i Bla Hallen, Ekologihuset, Solvegatan 37, Lund, ffedagen den 13 december 1996, kl. 1300. DISCLAIMER

Portions of this document may be illegible in electronic image products. Images are produced from the best available original document Interfaces in aquatic ecosystems: Implications for transport and impact of anthropogenic compounds

Johannes Knulst

FK,Sm

Dissertation

Lund 1996 A doctoral thesis at a university in Sweden is produced either as a monograph or as a collection of papers. In the latter case, the introductory part constitutes the formal thesis, which summarizes the accompanying papers. These have either already been published or are manuscripts at various stages (in press, submitted or in ms).

ISBN 91-7105-082-5 SE-LUNBDS/NBKE-96/1010+136 Contents

Introduction 7 Materials and Methods 20

Conclusions 26

Summary 35

A cknowledgements 37

References 37

D ankwoord 44

List of used abbreviations 46

List of Papers This thesis is based on the following papers which are referred to by Roman numerals. Papers I-III, V and VII are reprinted with permission from the publishers.

I. Espedal, H. A., O. M. Johannessen and J. Knulst. Satellite detection of natural films on the ocean surface. Geophysical Research Letters (in press).

II. Sodergren, A., P. Larsson, J. Knulst and C. Bergqvist. (1990) Transport of incinerated organochlorine compounds to air, water, microlayer, and organisms. Marine Pollution Bulletin 21:18-24.

III. Knulst, J. and A. Sodergren. (1994) Occurrence and toxicity of persistent pollutants in surface microlayers near an incineration plant. Chemosphere 29(6): 1339-1347.

IV. Knulst, J., P. Backlund, D. O. Hessen, G. Riise, and A. Sodergren. Response of surface microlayers to artificial acid precipitation in a meso-humic lake in Norway. Water Research (submitted).

V. Knulst, J. C. C. (1992) Effects of pH and humus on the availability of 2,2',4,4',5,5'- hexachlorobiphenyl- C in lake water. Environmental Toxicology and Chemistry 11(9): 1209-1216.

VI. Knulst, J. C., R. C. Boerschke and S. Loemo. Differences in organic surface microlayers from an artificially acidified and control lake, elucidated by XAD- 8ZXAD-4 tandem separation and solid state 13C NMR spectroscopy. Environmental Science &Technology (submitted).

VII. Hessen, D. O., E. T. Gjessing, J. Knulst and E. Fjeld. TOC fluctuations in a humic lake as related to catchment acidification, season and climate. Biogeochemistry, (in press).

i ’’For out of the oldfieldes, as men saithe, Cometh al this new come fro yere to yere; And out of old bookes, in goodfaithe, Cometh al this new science that men lere. ” —Geoffrey Chaucer (1328-1400) From Tyrwhitt Introduction

Mechanismsthat govern transport, accumulation and toxicity of persistent pollutants at interfaces in aquatic ecosystems are the foci of this thesis. Specific attention is paid to humic substances, their occurrence, composition, and role in exchange processes across interfaces.

The interface between air and water of lakes and oceans is covered with a thin layer of chemical substances. This thin layer (the surface film or microlayer) reveals properties distinct from subsurface water, and may therefore be treated as a separate ecosystem. Langmuir (1917) stated that anthropogenic effects occurring at physical boundaries of systems are of key importance for biological, physical, and chemical processes. Therefore, the properties of the surface film that presumably covers all bodies of water on Earth, are of particular interest.

The presence of an unique environment at the air-water interface has interested man for a long time. As early as 1500 B.c. Babylonian seafarers experienced that oil calmed angry seas when poured on the waves. A number of review articles (Liss 1975, Norkrans 1980, Hunter and Liss 1981, Hardy 1982, Maki 1993) assimilated findings on the chemistry, physics and biology of this environmental interface.

Surface films are defined as a relativelythin (0.001 to 200 pm), organic substance-rich layer at the water surface (Norkrans 1980). They maintain specific chemical and biological features (Daumas et al. 1976, Kjelleberg et al. 1979, Hardy 1982, Nageli et al. 1993). The upper portion of this film is referred to as the surface microlayer. In this thesis, an arbitrary difference between surface film and microlayer is that:

• The film contains a number of strata with concentrated biota, chemicals, and distinct physical characteristics compared to

subsurfacewater,

• while the microlayer constitutes the portion of the surface film

sampled by the collector.

7 ATMOSPHERE

Gas exchange ^ Dry deposition wind generated aerosols wet depostion bursting bubbles animal defecation evaporation gas exchange biotic uptake ^ biotic uptake run-off

^Wind and SURFACE FILM

currents Upwelling j L Biotic uptake convection = wave action diffusion % emulsion bubbles •| dissolution floatation E sedimentation _ re-fluxing r downwelling run-off a y

^wmd and

Figure 1. Sources and pathways of chemical substances to aquatic surface films. (After Hardy and Word 1986). Natural surface film is exposed to many environmental factors such as rain, winds, temperature gradients, and cosmic irradiance. Understanding the effects of man-made environmental changes on the properties of the surface film improves our ability to describe and explain the influence of surface films on transport of pollutants from air to water and vice versa. Studies of this kind are complicated, and the environmental circumstances must be considered carefully.

8 In spite of frequent sources of disturbance surface films are resistant to disruption, suggesting that a surface film is present on almost all surface waters. After physical disruption, the film is rapidly restored (Jarvis 1967, Williams et al. 1980, Dragcevic and

Pravdic 1981). Sources of the materials building surface films are, among others:

Aquatic biota releasing by-products (Dietz and Lafond 1950), leaching of allochtonous matter from land (Goldacre 1949), compounds of anthropogenic origin (Baier et al.

1974, Cross et al. 1987, Papers II and III), and atmospheric deposition (Hatcher and

Parker 1974, Elzerman et al. 1979). Transport of energy and matter from the atmosphere to aquatic ecosystems follows several processes (Fig. 1).

Air-water interface

The structure of the surface film has been described with several models (Fig. 2).

Figure 2. Surface film models proposed by (a) Norkrans (1980) Air (a) and (b) Sieburth (1983). The lipid bilayer model was first proposed lEiismmpi!* by Gorter and Grendel in 1925 as the fundamental membrane structure of biological cells. •©* ■©• *©• *®* Norkrans proposed two strata: The upper constituted of the lipids, the lower of protein- i *©♦ water molecule linear macromolecule saccharide complexes. The latter model is based on the fluid I phospholipid fatty add 1 particle or coiled macromolecule mosaic model (Singer and Nicolson 1972) proposed for complex membrane structures. The proposed models are based on the properties of the major groups of substances identified in the film. The simplest model (Fig. 2a) has a number of strata, defined by their chemical building blocks (Maki 1993). Although this model was found acceptable at that time, it is most likely not representative for the natural surface films of seas and lakes. The later model is based on a matrix principle where the chemical and biological building blocks of the film are placed in a gel-like matrix (Fig. 2b), co-ordinated by the quest for the lowest expense of energy. The gelatinous matrix suspension of

9 phospholipids means that the fatty acid tails of the phospholipids allow large molecules to float among them by changing molecular conformations of the fatty acids (Singer and Nicolson 1972, Sieburth 1983). The water surface can also act as a solid surface since the functional groups exposed to the air often are hydrophobic or ionic.

In 1974 a model of air-water exchange of gases was proposed by Liss and Slater. The model was based on a simple two-layer interfacial structure. The authors cautioned against the discrepancies in this model, but suggested that it was useful for visualising processes at the interface. Calculations made with this model were not different from the more sophisticated model of Danckwerts (1970, in Liss and Slater 1974). Important conclusions were (1) that all resistance to transfer of sparingly soluble gases, such as 02 and N2, across the interface occur in the liquid phase, not in the gaseous phase, and (2) transfer across the bilayer is molecular (Liss and Slater 1974). Emerson. (1975) found C02 transfer across the interface to behave similarly, and proposed a model for gaseous fluxes across air-water interfaces. This model is similar to that used for computer simulations of surface processes (Li et al. 1995). Doskey and Andren (1981) proposed a model for flux calculations of PCB across the Great Lakes air-water interface. They found fluxes of PCB into the aquatic ecosystem to exceed those out of the water.

Since I have found the major part of organic surface microlayers to consist of macromolecular humic and fulvic acids (Paper VI), and these molecules have multiple binding sites for other compounds (Paper V), the gel matrix model of surface films proposed by Sieburth (1983) seems best to represent the chemical environment at the freshwater air-water interface. For unstable gases, such as C02, significant influence of the humic macromolecules on transport may complicate the use of simple two-layer models to describe fluxes across the interface.

Other interfaces

Membrane structures surrounding cells form important interfaces. Cell membranes and surface films are structurally comparable, and to some extent also consist of similar organic compounds (Table 1). Theoretically their effects on transport of pollutants may be alike. Transport of compounds across biological interfaces mainly follows special corridors, in the form of proteins or impurities in the membranous structure (Suttie

10 1983). Transport across synthetic materials such as dialysis membranes, polymer films, and other solids may follow the pores and impurities of the material, or dissolve and diffuse in the material (Comyn 1985). Compounds may simply diffuse through the interface, or become actively transported across it. The exact processes for this transfer are not known.

My studies of organic pollutant transport through the membrane structures of dialysis membranes gave some insight into the processes involved. Selective transfer of pollutants through cell membranes may alter the fingerprint pattern of e.g. PCB compounds taken up through interfacial structures. The transfer of PCB through the dialysis membranes was prohibited by association of PCB with natural organic macromolecules.

Organic composition of surface films

Natural organic matter (NOM) encompasses all but anthropogenic organic carbonaceous substance present in the environment. The NOM pool can be .divided into two major fractions:

I. The dissolved fraction, usually expressed as dissolved organic carbon (DOC) which represents the dissolved organic matter (DOM), is a fraction that is most mobile in aqueous systems (Wetzel and Manny 1977). This means that it can be transferred between phases with relativeease.

II. The particulate fraction can be divided into several portions (e. g. coarse and fine) of particulate organic matter. In this work it is referred to as particulate organic carbon (POC). POC is separated from the dissolved fraction by filtration. The filter pore size defines the cut-off molecular size. This fraction is easily degraded, rendering it available as a major food resource to aquatic invertebrates (Cummins 1974). The adsorption of chemical substances on the surface of POC will allow transportation of these substances throughout the ecosystem (Riise et al. 1994).

Hunter and Liss (1981) reviewed the NOM of sea surface microlayers, noting that approximately 90% of DOM was uncharacterised. The main portion of uncharacterised DOM belongs to the dissolved humic substances (Table 1). Thurman (1985) reviewed the organic chemical composition of surface waters and reported a recovery of 65-70% of DOM with XAD-resin separation techniques. Thurman and Malcolm (1983) used

11 XAD-8 in combination with XAD-4 resins to separate up to 85% of the total DOM pool. This method, improved by Malcolm (1991), was used in Paper VI to characterise DOM of surface films. About 15% of DOM still remained uncharacterised in my study (Paper VI).

Table 1. Organic constituents of surface films of autochtonous (A) or allochtonous (U) origin and biological structures of Alcohols + + animal (S) or vegetative (P) origin in rough shares of total Fatty acids ++ ++ organic carbon (- trace element, Carbohydrates -(A) +(U) -(S) +(P) + minor element, ++ major element). Compiled from Gara- Hydrocarbons -H- - betian et al (1993), Williams et Humic substances + (A) ++(U) (-) (S) ++(P) al. (1986), Thurman (1985), Suttie (1983), Hunter and Liss Proteins (+)+ ++ (1981), Sieburth et al. 1976, Vitamins, enzymes - - Larsson et aL 1974, Baier et aL 1974, and this work

The major portion of natural organic substances in soil and water is made up of humic substances (HS)(Schnitzer and Kahn 1972). This also seems to be the case with organic surface films of lakes (Paper VI). HS constitute a large number of organic compounds arbitrarily defined by their method of separation. HS are chemically relatively stable compounds and resist degradation by micro-organisms. They are of biological origin, derived from lignin and cellulose, and dominated by macromolecular structures (Thurman 1985), or synthesised from smaller organic molecules of biological origin (Stevenson 1982).

The macromolecules of the HS group contain a variety of functional groups. The most important functional groups responsible for the polyelectrolytic character are the carboxylic, phenolic, and alcoholic groups (Thurman 1985). HS macromolecules are commonly surface active and therefore may be found in surface films (Hunter and Liss 1981). In the early 70s it was found that at least 10% of the DOM consisted of macromolecules (Sharp 1973). However, in my study of the surface microlayer of Lake Skjervatjem, 40 to 50% of DOM consisted of macromolecular compounds (humic acids and hydrophobic neutrals, Paper VI). Development of analytical techniques may explain this difference.

12 I also found a relatively large proportion of carbohydrates in the surface microlayer of the acid treated Lake Skjervatjem (Paper VI). It indicated that the surface film organic matter was more closely related to soil humic matter, while the surface film of the control basin contained a small proportion of carbohydrate DOM, which is characteristic for aquatic humic substances. Also, the carbohydrates are usually combined with protein molecules (Aiken 1985) which was supported by the large organic N fractions in surface films of Lake Skjervatjem (Paper IV). The HS evaluation may thus be used in source location of film DOM.

Enrichment of surface active organic matter

Surface active substances at the air-water interface can be determined by measurement of surface potential or surface tension (Jarvis 1967). However, since the exact composition of the surface film is not known, these measurements can only indicate a relative state of the interfacial material. Spatial variability of DOM in surface films is great and related to concentrations of DOM in the bulk water (Carlson 1983, Paper IV). Measurements of surface potential can give a rough estimate of spatial DOM variability.

Enrichment of surface active materials in the film, defined as the ratio of a compound in the surface microlayer to that in the subsurface water, differs due to compound properties. Enrichment in the film of phenolic fractions of DOM can be described with a partitioning relationship (Carlson 1983), indicating their behaviour as lipophilic compounds. Proteins are surface active and usually enriched in freshwater surface films (Baier 1972, Baier et al 1974, Papers IV and VI). A major difference between phenolic DOM and protein material is that proteins do not reduce surface tension significantly (Walstra and DeRoos 1993).

Removal of organic matter from surface films

Salinity of sea-water is inversely related to the enrichment of DOM in surface films (Daumas et al. 1976) since DOM precipitates when the solution ’s ionic strength increases. Allochtonous terrestrial materials can contribute significantly to particle formation in film DOM (Sholkovitz et al. 1978). Wangersky (1976) proposed that organic coating of atmospheric particles while passing through the surface film removed

13 dissolved organic matter. Upon wind compression the collapse of DOM in surface films could be a significant removal process for film DOM (Wheeler 1975). Removal and re-supply times of substances in the surface film were calculated by Carlson (1983). He found that the size of the molecules plays an important role in the cycling rate of compounds. The kinetics of removal and re-supply are hard to study if the residence times of the molecules at the interface are short. The other reason for difficulties with kinetic studies is that the chemical identification of surface film NOM is still incomplete.

Separation and identification of surface film DOM with new methods (Paper VI) showed that the sources of DOM in the acid treated and non-treated lake basins were different. Compared to the control basin, more POC turnover took place in the treated basin surface film. This may have been a result of a proportionally larger influence of the watershed on the film DOM. This would indicate a greater impact on DOM removal by allochtonous material from terrestrial sources (Sholkovitz et al. (1978) than by particle formation resulting from surface film wind compression (Wheeler 1975).

Anthropogenic materials

Surface active substances possess a high affinity for non-polar organic pollutants (Sodergren 1973, Hardy et al. 1988) and trace metals (Duce et al. 1972, Owen et al. 1979, Cross et al. 1987). The film itself is not considered important as a major contaminant reservoir due to its small volume. The functioning of this reservoir is of major concern. For example, since atmospheric transport of pollutants has become the prominent distribution process to remote ecosystems (e. g. Muir et al. 1988) transport phenomena between air and water have gained importance. The film does not interfere with air-water equilibrium partitioning of pollutants, but affects the dynamics of this process.

Two regions in the Northern Hemisphere have received particular attention with respect to anthropogenic aspects of surface film research, namely the Great Lakes Region of North America and the Baltic Region of Europe. In Scandinavia, the majority of persistent organic pollutants is imported through atmospheric transportation (Alsberg

14 and Nylund 1993). This is also valid for the Great Lakes (Eadie et al. 1983). Both in Scandinavia and the Great Lakes Region, enrichment of persistent organic pollutants (PCB, DDT) in surface films were studied (Sodergren 1973, Andren et al. 1976, Rice et al. 1982). In some surface film studies, atmospheric transport of pollutants is put in relation to internal cycling processes of the aquatic ecosystem, such as sedimentation and re-suspension of PCB enriched particles (Rice et al. 1982) or evasion of PCB to the atmosphere by bursting bubbles (Sodergren and Larsson 1982). The presence of toxic substances in surface films has lead to investigations of properties connected to these films in polluted marine locations such as Baja California (Williams ,ef al. 1986), the New York Bight (Hardy et al. 1988), the North (Hardy and Cleary 1987) and Mediterranean Seas (Garabetian et al. 1993).

Testing in situ surface film toxicity is difficult. Yet, collecting the surface microlayer and testing its toxicity in laboratory bioassays is practised. My study (Paper III) indicated that the toxicity of the surface film reservoir cannot be ignored although considerable caution has to be taken to establish contact between the film’s pollutants and the test organisms. It has to be emphasised that most toxicity bioassays are not suited for testing hydrophobic materials such as surface microlayers.

Impact of airborne pollutants on ecosystems

Air pollutants are either gases, liquids, or solids (particles). Aerosols, either neutral particles or condensation nuclei (hydroscopic substances), are closely related with surface film material (Eisenreich 1982). Dispersion of air pollutants depends on wind vectors, barometric pressure, temperatures, precipitation, and topography (Williamson 1983). Major natural sources of airborne materials are volcanic eruptions, swamps, and forest fires, although relative contributions are far less than those from anthropogenic sources.

Airborne pollutants may affect aquatic ecosystems and the surface film in a number of ways (Table 2). Acute toxic effects of airborne pollutants are commonly not expressed. Chronic toxicity is more common, as is the damage done to the ecosystem structure (e. g. diminished prey population due to unsuitable light or nutritional conditions).

15 Table 2. Ecosystem functions affected by exposure to toxic substances and effects shown and discussed in this thesis.

organic decomposition change in water colour nutrient losses or conservation nitrogen budgets offset changes in energy balance alteration in light extinction (UV) changes in biological production availability ofHMW/LMW material altered food webs not shown functional regulation of ecosystem processes particle formation, and light extinction

Atmospheric pollutant transport

Studies of organic pollutant contents in precipitation, reviewed by Mazurek and Simoneit (1987), showed concentrations of organic pollutants in rain, snow, and dry deposition to varyafter similar patterns. This strengthens the belief that these pollutants are long-range transported (Volokitina and Shuklin 1980). Wet deposition of particles is a significant source of organic pollutants to soil and water (Sodergren 1972, Larsson and Okla 1989). The uptake of atmospheric pollutants into an ecosystem is mainly directed by the rate of pollutant volatilisation from particulate to dissolved state, secondarily by the contact of particles with active surfaces (Omann and Lakowicz 1981). The pollutant ’s volatilisation rate is determined by the adsorptive capacity of the particle surface and by the properties of the pollutant. Changes made to the pollutant during atmospheric transportation can express themselves as altered adsorption coefficients.

Interfaces as transport regulators

Besides functioning as a transport corridor for pollutants, the surface film has several regulatory functions. I will present some examples.

Exchange processes between air and water are related to climatic (Fig. 3) and surface conditions. The importance of surface films for transfer of light between air and water has recently been discussed (Kirk 1994).

16 Climatic conditions SOLAR' lirradiationl

cipitation Atmospheric Clouds losses ## """""""" Reflection >1 Gas Deposition gk~ . diffusion Evaporation

Runoff Surface viscosity TOC and molecular density trace elements nutrients Removal pollutants processes

light regime nutrient availability temperature TOC turbulence light regime nutrients pollutants geochemical cycles

Figure 3. Major pathways between the atmosphere, aquatic surface film, subsurface water and land that are related to climate. The mechanisms by which exchange takes place are not clarified (Eadie et al. 1983, Kirk 1994). Liss and Duce (in press) edited a number of subjects related to climatic conditions and exchange processes at the ocean surface. Climatic changes due to altered atmospheric conditions may affect surface films by temperature, pressure, turbulence, and irradiance changes. The surface film chemistry may respond to climatic changes and allow shifts in physical properties, such as UV light extinction. HS macromolecules at the air-water interface, maintaining a gelatinous structure will inevitably lead to reduced evaporation rates, unless the macromolecular structure is damaged by UV irradiation or other environmental forces. The shapes and properties of HS in the surface film have to be known, before detailed conclusions can be drawn about the impact of environmental forces on resistance of the molecular film to transfer across the air-water interface.

17 Statistical analysis of surface film data

Statistical evaluation of surface film data is commonly hampered by the small numbers of collected samples. Laboratory studies, such as those given in Papers II and V, provide a better control of the variables than field studies, such as Paper IV. When large numbers of samples are collected, multivariate analysis can give indications of relatedness and quantify relationships. However, collection of surface film in quantities necessary for chemical analysis of field parameters like pH, conductivity, spectrophotometric absorbencies, etc. and specific parameters such as DOC, POC, chlorophyll-^, and nitrogen fractions, is often complicated and difficult to achieve simultaneously. This thesis puts together laboratory experimentation and extensive field surveys, and can therefore provide a quantitative as well as qualitative description of surface film chemistry, in spite of narrow statistical evidence.

Remote sensing of surface film chemistry

If chemical substances are defined as units of energy, then ecosystems are units of energy cycling and recycling. When investigating the effects of a chemical substance on a certain target (e. g. organism, organ, tissue component or function) in an ecosystem, the way how the substance reaches the target is important. New approaches in toxicology are based on this energy flow principle such as the use of quantitative structure-activity relationships (QSAR). In QSAR studies, toxicology of a substance or series of substances is related to the chemical structure and/or one or more physico ­ chemical properties of the substance(s) by statistical analysis (DeBruijn 1991). Remote sensing capabilities of environmental features have recently improved, and energy forms can be used to scan the environment for pollutant sources (Paper I). As life within an ecosystem is dependent on the availability of energy and matter, the input of energy to the ecosystem is the key to development and functioning. In ecosystems, the input of energy and matter takes place at the ecotones, the ecosystem ’s boundaries. The major boundaries of aquatic ecosystems are the littoral zone (soil-water), sediment- water, and the air-water interfaces (Wetzel 1983, Hardy 1987). In this work only phenomena at the air-water interface were studied via remote sensing.

18 ”1 do not know what I may appear to the world; but to myself I seem to have been only like a boy playing on the sea-shore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me. ”

—Isaac Newton (1642-1727)

i

Ii ! I i i ! 19 I iI Materials and Methods

Sampling

Surface microlayer

Because the definition of surface film or microlayer depends on the collector, I will briefly describe the sampling techniques used. Most field collections of the surface film material presented in this thesis were performed with a remotely controlled (RC) surface slick collector (Fig. 4).

Figure 4. Remotely controlled by radio-frequency signals, the surface slick collector INTERFACE I, recovers surface microlayers (10-150 pm) with little risk for contamination (Artist: Arvid Karsvoll). Rotating drum

The collector is directed via a FM radio control unit and designed after the rotating drum principle proposed by Harvey (1966). The drum, fitted in front of a catamaran vessel, rotates slowly (at 9-15 rpm) against the direction of motion across the water surface. The vessel moves slowly (at 0.15-0.20 km hr" 1) across the water surface. The drum, covered with chemically treated teflon film, giving it hydrophilic properties, adsorbs a thin layer of water. The water (surface microlayer) primarily adheres to the drum by capillary forces. After the microlayer attaches to the drum, it is scraped off by a sharp, hydrophobic teflon wiper blade (Fig. 5). The microlayer flows into a glass container in the vessel.

20 Figure 5. The principle of the rotating drum collector first proposed by Harvey Scraper blade (1966) and applied to the radio-frequency controlled model vessels INTERFACE I and//.

Time, visible weather and surface conditions, number of drum rota ­ tions, water and air temperatures, and volumes of sample are registered during the collection of surface microlayer.

The major advantages of this RC collector are:

• The sample is collected well away from possible sources of contamination (ships, coastlines, etc.).

• The collector has access to locations with low navigability for larger vessels.

• Various measurements can be made from the collector platform during sampling.

The satisfactory use of this RC vessel on inland waters, however, was not achieved on the open sea, where the small size (LxWxH, 120x38x29 cm) and forward drum placement decrease sampling efficiency (from 80-98% to 15-35%, unpubl. data). Therefore, I constructed a new slick collector, using the INTERFACE I as a prototype. This collector is larger than its prototype (160x136x52 cm). The drum was placed between the floaters of the vessel where it provides better stability and is protected from the influence of side sweeping waves. The robust size complicates navigation in tight places, such as between emerging macrophytes in freshwater, but makes it better suited for marine environments.

Glass plate

Harvey and Burzell (1972) described a simple method for collecting surface film samples, using a glass plate. This method is easy to use, gives adequate results, and has therefore been applied by many researchers. For comparative purposes and because of its suitability for small waters (fish tanks, ponds) this method has been used in certain cases.

21 Figure 6 . The glass plate method by Harvey and Burzell (1972). Drawn from their original illustration.

The plate is held with a handle, immersed in a vertical position and drawn up through the air-water interface at a constant speed and vertical angle to the surface. The organic film adheres to both sides of the glass plate and is removed by scraping the plate with a neoprene window wiper blade (Fig. 6).

Teflon plate (sheet)

Garrett and Barger (1974) first described the use of a teflon sheet for collecting bacterial surface films. The sheet is fitted to a handle and dipped onto the water surface.

Figure 7. Teflon dipping plate and handle (SQdergren 1979) for collection of surface microlayer material from small water surfaces.

After making full contact with the water surface, the sheet is retrieved with a vertical motion and can be dried off with a wiper, or a surface microlayer fraction can be extracted by a suitable solvent. This method, modified by Sodergren (1979), using hydrophilic teflon sheets cut into round discs (Fig. 7), was used in the fish tank

22 experiments of Paper II. After extraction, the discs could be cleaned and re-used several times.

Subsurface water

In Paper II the subsurface water was sampled with polyurethane foam filters (Uthe et al. 1974). The polyurethane foam has a large surface to volume ratio and absorbs non ­ polar organic pollutants effectively (Uthe et al. 1974, Larsson and Sodergren 1987). The polyurethane foam plug(s) are placed in a glass tube which is open at one end and connected to a hydrostatic pump at the other. The tube is placed at a defined depth in the water, and water is pumped through the foam plug(s). The sample is extracted from the plugs with solvents, concentrated, cleaned up, and then analysed.

Air

Paper II explains the use of polyurethane foam plugs to extract airborne compounds. The foam plug(s) are put in a glass tube that is open on one end, while the other side leads to a large volume air pump. The tube is attached in the air, with the open end downward, to prevent precipitation from contacting the plug(s).

Analytical procedures

NOM separation and analysis

Aiken (1985) reviewed different methods for aquatic humic substance isolation. Paper VI describes the used NOM extraction and separation procedures. Since this is a novel method in the field of surface film research, I will briefly discuss the principles of the method.

Surface microlayer and subsurface water are filtered to remove particles. The DOC constituents are then separated from the liquid by macroporous ion exchange resins, called XAD resins (Rohm and Haas, Philadelphia, PA.). Aiken et al. (1979) reported a column retention and release of 98% from XAD-8 resin. Fine grained XAD-2 resins show lower separation efficiencies and are therefore not recommended for whole sample surveys (Aiken 1985). The organic matter not retained by the XAD-8 column is between 30-40% of total DOC, mainly hydrophilic organic acids (LMW) and acid sugars (Thurman 1985). This fraction is usually not recovered in this procedure, but the

23 tandem separation with XAD-8, followed by XAD-4 macroporous resin (Thurman and Malcolm 1983, Malcolm 1991, Paper VI) reduces the unrecovered portion of DOC below 15%. The XAD-4 resin is fine grained, and adsorbs LMW molecules well (Malcolm 1991). XAD-4 resin is capable of selective adsorption of ionic surfactants with smaller molecular sizes than humic and fulvic acids (Thurman and Field 1989).

13C-Nuclear Magnetic Resonance (NMR) data suggest that differences exist between soil and aquatic humic substances (Thurman 1985, Malcolm and MacCarthy 1986). These differences were not determined by earlier studies using other methods (Schnitzer and Kahn 1972, Gjessing 1976, Visser 1985). No evidence has been available for the distinction between surface film humic materials and soil or water humic substances. This thesis includes the first article (Paper VI) to be published on detailed microlayer humic substance analysis that allows identification of humic material in surface microlayer DOM.

Experimental methods

Some general comments

Sediments--The closed fish tank used to study the distribution of substances introduced via the air in various environmental compartments had a major simplification. For the stability of the system, sediments were not included, although they are important compartments in aquatic ecosystems.

Biogenic film formation—A method was developed to introduce substances originating from an incinerator ’s smoke stack to aquatic ecosystems at a smooth rate in both gaseous and particulate forms. To study the influence of the surface film on the distribution pattern, artificial lipid films were introduced on the water surface. For comparative purposes, several attempts were made to remove the surface microlayers from the systems, but all failed. The presence of biogenic compounds in the water provided a new film within seconds.

HUMEX— Surface microlayers and subsurface water were collected from both sides of the plastic curtain that separated the acid treated basin from the control basin of Lake Skjervatjem in Western Norway (Fig. 8). The treatment of catchment and basin with

24 artificial acid precipitation was followed in the HUMEX project, coordinated by the Norwegian Institute for Water Research. The main goals of this project were to determine the effects of acidification on humic substances in catchment and lake, as well as the effects of humic substances on the acidification process (Gjessing 1992). Papers IV, VI and VII all dealt with data collected at this site.

Figure 8. The HUMEX site, where catchment and lake were treated with artificial acid rain on one side (A) of the divide, and the other side (B) served as the control.

I

25 Conclusions

The relationships between surface film chemistry and anthropogenic influences, were discussed as pollution discharge effects (Papers I-IJI) or by the effects of pollutants and environmental factors on film properties (Papers TV-VII). Humic substances are among the organic compounds that are responsible for the surfactant properties of the films, and are possibly involved in transport mediation of trace metals and non-polar organic pollutants.

Satellite radar detection of interface properties

Need for temporal and spatial interfacial exchange assessment

Assessment of transport phenomena across interfacial structures is possible in small scale experiments (Papers II-V). However, spatial and temporal information about large scale transport of energy and matter across air-water interfaces is more difficult to obtain. Knowledge about ocean surface features is applicable in many areas such as ship navigation, oil spill monitoring, and algal bloom detection (Hovland et al. 1994), and would increase dramatically using remote sensing. Paper I introduced the use of satellite borne synthetic aperture radar (SAP.) for detection of sea surface films. Establishing a databank to run adequate algorithms involves the collection of data of film chemistry, interactions with waves (windspeed), currents, and aquatic biology (e.g. algal blooms, coral reefs). Some specific features in SAR images of ocean surfaces can still not be translated into physical phenomena. No correlation of surface film chemistry with radar backscatter was established during our experiments, probably due to incomplete chemical identification of components in the organic film.

Humic substances are an important component of the film since they influence surface tension significantly (Chen and Schnitzer 1978, Hayase 1992, Anderson et al. 1995) and are abundant in the films (Paper VI). Humic acids are of particular interest due to their relatively large size and complex forming behaviour.

The amount of UV absorbed by the surface microlayer, used as coarse indication of the phenolic portion of DOC (Carlson and Mayer 1980), showed a covariation with radar backscatter. Sources that contribute to surface film DOC are related to environmental conditions (coastal vs. oceanic areas, terrestrial vs. planktonic sources). The phenolic

26 portion of DOC is small when the source is planktonic (Johannes and Webb 1965) and large with terrestrial sources (Berdie et al. 1995). Therefore, near-shore surface films, most likely influenced by HS of terrestrial origin, will cause stronger dampening of capillary waves than oceanic films will.

The amount of particulate matter in the film showed a covariation with the radar backscatter. However, due to the many variables that govern particle presence of the film, it should not be used in a tracking algorithm. As shown in this thesis, and concluded by others (e.g. Hoffman et al. 1978), the particulate fraction of the NOM is important for transport of, for example, trace metals and non-polar organic pollutants across the air-water interface.

VMndspeed T (degr Q (nrVsec) 17.5 T INTERFACE II, 15 Sept. 1995

17.0-

■TSM

•* —TSW 15.5, p.

time (min)

Figure 9. Example of temperature profiles used to detect slicks on the sea surface. Temperatures in air (h=0.8 m), surface water (SM) (0 to -3 mm), and subsurface water (SW) (-0.2 m) in the North Sea during NORCOAST experiment. Windspeed (WS) measured at h=0.8 m from the INTERFACE n model vessel. The temperature ratio between surface and subsurface water may be used to study surface film characteristics (Fig. 9). When phenolic HS are present in a slick, temperature in the slick may increase compared to the non-slicked surface, due to absorbance of solar energy by the HS molecules and decreased evaporation by capping

27 the interface with a denser organic film. Combining surface temperature measurements with SAR imaging may be feasible for surface film detection and coarse chemical identification of the film constituents.

Natural organic matter in surface films

Need for complete NOM characterisation

Many models of air-water interfacial processes suffer from the incomplete knowledge of the organic composition of surface films. I suggest that more attention be paid to humic substances, mainly because of their surface active character and abundance in surface film. I will illustrate the significant proportion of HS present in freshwater surface films by comparing my data on organic compound distributions with those givenby Thurman (1985)for what he called a typical freshwater lake (Fig. 10).

DOC histogram

Fulvic acids

Humic acids

Hydrophilic acids

Carbohydrates

Carboxylic acids

Amino acids

Hydrocarbons 0 10 20 30 40 50 %

Subsurface water Surface microlayer

Figure 10. Composition of dissolved organic carbon (DOC) in subsurface water from a freshwater lake with average DOC concentrations of 4-5 mg C litre"1 (from Thurman 1985) compared to surface microlayers from freshwater Lake Skjervatjem, Western Norway.

Humic substances are also able to alter illuminescense and surface tension, hence they can affect remotely sensed surface data (e. g. Ocean Colour Index and SAR signature of

28 wave dampening). The aromatic character of the humic DOM fraction changed after acid treatment (Paper VI), indicating that UV absorbance of the surface film may change accordingly. I found that DOC enrichments in freshwater surface films rarely exceeded 3 (Paper IV), suggesting that DOC of the surface film followed subsurface water DOC. An appreciable amount of the surface film DOC showed hydrophilic properties, supporting findings reported by Hunter and Liss (1981), and suggesting that the organic surface film layer is a gelatinous matrix with molecules supporting each other at the interface by inter- and intramolecular interactions.

Pollutant movement across interfaces

Concentration gradients and uptake patterns

Surface films often contain pollutants at higher concentrations than the surrounding air or water. Partitioning of lipophilic pollutants from air to water via the interfacial film is a major transport mechanism, primarily controlled by the pollutant ’s hydrophobicity (Hoff et al. 1993). The relativelyhigh proportion of lipid materials at the interface may trap pollutants with lipophilic properties. Transfer is molecular across the interface, and transfer rates may increase by association of the lipophilic pollutants with humic acids or particles. The factors affecting the amount of pollutant transfer across the surface film are the surfactant properties (molecular conformation, particle porosity) of the carrier host, the strength between pollutant-carrier complexes, and the density of the surface film.

The lipid bilayer (Fig. 2) is transparent for non-polar pollutants but resists transfer of ionic or polar molecules. The simple model proposed by Norkrans (1980), therefore, would not allow selective transfer of PCS - humic acid complexes. Since transfer of PCBs across the surface film does occur, and the film contains humic macromolecules that can complex PCB, the surface film cannot be regarded as a simple lipid bilayer. Finding both humic acids and protein-polysaccharide complexes (Paper VI) in the drum collected surface microlayer of Lake Skjervatjem supports the chemical description of freshwater microlayers given by Baier et al. (1974) and Sieburth et al. (1976). Some questions about the density of the organic macromolecules in the upper film strata remain unanswered. Earlier work has concentrated mainly on the low molecular weight

29 fractions of the NOM from slicks (see Hunter and Liss 1981). Knowledge of the abundance of humic acids in the surface film adds a new dimension to chemical arrangement of the upper film strata. This has important consequences.

Suppose that the surface film is arranged in patterns similar to cell membranes. Then, ionic (e.g. cations, trace metals) and polar compounds can only be transferred across the film structure by carrier hosts. These carrier hosts could either be proteins as in cell membranes, solvents, and/or macromolecular structures with properties similar to proteins such as humic acids. The host will dissolve the ionic or polar substance by encasing it (crown or micelle formation, Morrison and Boyd 1983) and allowing transfer through the film. The abundance and lipophilic properties of surface film HS favour such a mechanism. However, to finally prove the existence of such transport mechanisms, the organic composition of a surface film has to be better explored to allow for kinetic studies.

Pollutants may also be distributed by any of the transport processes shown in Figure 1. Adsorption of dissolved and particulate lipophilic organic molecules will result in enrichment in the film.

Organisms collected at polluted sites (Paper III) showed higher pollutant levels in tissues than those collected at the control site. This may be related to the higher pollution level in the air (Papers II - III), resulting in partitioning between air, surface film, water, and organisms.

NOM properties in surface water (Paper V) influenced the uptake of lipophilic organic pollutants by solvent filled membranes. My results showed that transfer by passive diffusion across interfaces is of significance. DOM, originating from lakes with high DOC levels and great tendency to form particles, reduced uptake of pollutants by the solvent filled membranes more than DOM from lakes with low DOC levels.

Toxicity of surface microlayer material to organisms

Toxicity of surface films should not be assessed by conventional toxicity assays since the lipid properties of the surface film may prevent contact between the pollutants and test organisms (Paper III). There is an urgent need to develop specific bioassays for

30 testing non water soluble pollutants such as the floating cells proposed by Premdas and Kendrick (1992).

The sampling method considerably affects toxicity assessments. Since my study made use of the same method to collect material for toxicity studies, my conclusions have a qualitative status, indicative of possible variation between sites.

Natural organic matter and pollutants !

Effects of acidification and liming on the ability of HS to associate non-polar substances and transfer across interfaces were investigated in a laboratory assay (Paper V). Pollutants associated with DOM were prevented from penetrating dialysis membrane interfaces. A linear relationship existed between pH of the solution and the ability of the DOM to trap PCS compounds. It was concluded that the reduced dialysis concentration factor (DCF) was related to the organic contents of the lake water. The concentration of DOC had a significant effect on the reduction of the DCF in the acidified system. Due to different composition of DOC, the reduction in DCF varied between lakes. DOC separation and identification would have contributed to the understanding of involved processes, but the volumes of the experimental systems were too small for such determinations to be made. Kukkonen et al. (1990) investigated the relationship between pollutant uptake in Daphnia magna and pollutant binding to XAD- 8 organic fractions. The hydrophobic XAD-8 acids fraction had the greatest affinity for binding PAH of relatively high hydrophobicity. This was also the fraction with the highest relative UV absorbing potential.

Assuming that a gelatinous matrix surface film is present at the air-water interface and that HS are incorporated in this film, has another important consequence. The pollutants that are somehow complexed with the organic macromolecules in the film are distributed throughout the film. Pollutant enrichment studies in surface films must include the presence of HS macromolecules for two reasons: (1) The HS molecules can complex the pollutant and prevent its separation and detection and (2) the pollutant does not necessarily reside in the lipid fraction of the surface film. The statement recently made by Gever et al. (1996), that the enrichment factors of hydrophobic pollutants in

31 the surface microlayer will be underestimated due to the lipid film actually being 10-20 Angstrom, while collecting much thicker layers exemplifies the neglect of possible HS - pollutant interactions and the possibility of HS molecules to reside in any part of the matrix. The applied method for surface microlayer recovery needs to be able to collect the whole matrix. The use of hydrophilic teflon is still the best method in this respect.

Pollutant transport and anthropogenic changes

Acidification effects on transfer across interfaces

The effects of artificial acidification on the aquatic surface films of Lake Skjervatjem in Western Norway (HUMEX) in relation to the key functioning of the lake ecosystem were discussed in Paper IV. Separating the effects of the treatment on water and film chemistry from the effects of hydrology and geomorphology of the catchment was difficult (Paper VII). The composition of the organic surface films of both lake basins was different from the subsurface water. This was also the case with the functional groups of the humic substances and small size organic acids (Paper VI). Anderson et al. (1995) reported unique surface tensions for different HS, which changed significantly due to altered pH of the solution. Presence of saccharides in the acid treated surface film suggested that the DOM in this basin was dominated by terrestrial HS, while the film DOM of the control basin mainly consisted of aquatic humic material. The production of saccharides by acid degradation of higher MW material was not likely, since the inorganic composition of the lake water did not change due to the acid treatment (Lydersen et al. 1996). Unique properties of the surface film DOM seem related to the origin of the DOM, such as was proposed by Sodergren (1993). The formation of slicks (Paper I) and the removal processes of slick organic matter are often related to particle formation (Paper IV) affected by external environmental stresses such as acidification, wind, and UV irradiance.

Liming effects on transfer across interfaces

The effect of liming was most likely due to the addition of particles to the systems, thereby increasing the surface area for interactions, ionic strength of the solution, and neutralising H4" concentrations. The ionic strength and the pH of the solution alter the

32 ability of the HS molecules to complex pollutants (Choudhry 1983, Suffet and MacCarthy 1989).

Effects on NOM complexation of trace metals

In natural water at ambient pH, HS may adsorb trace metals (Morel 1983). Therefore, DOM can act as carrier of trace metals. The properties of the HS will most likely be responsible for the specific association between metals and HS. A number of studies have reported high concentrations of NOM and trace metals in surface films (Williams et al. 1986, Cross et al. 1987, Hardy et al. 1988). Studies of complexation between HS and trace metals have shown that metals commonly are associated to the NOM macromolecules by van der Waals forces, H-bonding, ion exchange, cation bridging, covalent bonding, ligand exchange, protonation and dipole-dipole interaction mechanisms (Riise 1994). In the surface film, trace metals are mainly associated to particulate matter and correlated with POC (Lion et al. 1982). Surface adsorption seems to dominate over other mechanisms. Hardy and Cleary (1992) found higher enrichments of trace metals in surface films from near-shore locations in the German Bight than further out to sea. They also found a decreasing toxicity gradient toward the open sea. These findings, although only of comparative character, support the POC related association of pollutants in the surface film. Effects of acidification and liming on the DOCrPOC ratio reported in this thesis, suggest that the toxicity of trace metals and organic pollutants may vary due to changes in NOM-pollutant complex formation.

Catchment, climate, and surface film organic matter

NOM fluctuations due to catchment

The absence of seasonal trends in the sedimentation rates of TOC in Lake Skjervatjem (Paper VII) indicated that sedimentation does not covariate with UV irradiance or weather conditions. The seasonal fluctuations of TOC in the lake and run-off were similar in both basins. Sedimentation, photo-oxidation, and biological degradation are minor removal processes of TOC from a small lake in relation to surface run-off. For the surface film, however, sedimentation is considered the main removal process of

33 TOC from the film, resulting from particle formation upon compression, UV oxidation, chemical oxidation, and biological degradation of the NOM.

NOM fluctuations due to climate

Experimental UV-B irradiance of a small pond in the catchment of the HUMEX experiment resulted in increased proportions of particulate organic matter in the surface film of the pond, directly following the UV-B exposure, as compared to a control pond (Fig. 11). After more than one hour of UV-B irradiance of the surface film of this highly coloured pond the particulate matter became depleted in the surface film. UV-B irradiation thus affected the surface microlayer proportion of POC, which supports findings of UV degradation and precipitation of aquatic humic matter (Gjessing and Gjerdahl 1970, Backhand 1992). Particle formation can result either from coagulation of degradation products in the surface film (Paper IV), or from removal of DOM, followed by replacement with surface active material from the subsurface water. Products of degradation can move either to the atmosphere or to the subsurface water, or they can possibly become utilised by micro-organisms in the surface film (Maki and Hermansson 1994).

6 —•—DOC 3 —■—POC 3 * * ^ * ■DOC6 •'O** POC 6

m

-2 -1 01 2 3 4 5 6 7 8 Relative time (hr)

Figure 11. Dissolved and particulate organic carbon enrichment factors in surface microlayers of a pond irradiated with UV-B (no. 3) and a pond with natural exposure (no. 6) (Knulst and Loemo, unpub!, material). Surface microlayers were collected with glass plates on August 12, 1994. Time 0 (11 a.m. local time) indicates the start of the UV-B irradiation. Mean DOC cone, in subsurface water 32-34 mg C litre"1.

34 Summary

Mechanisms that govern transport, accumulation and toxicity of persistent pollutants at interfaces in aquatic ecosystems were the foci of this thesis. Specific attention was paid to humic substances, their occurrence, composition, and role in exchange processes across interfaces. It was concluded that:

• Composition of humic substances in aquatic surface microlayers is different from that of the subsurface water and terrestrial humic material.

• Levels of dissolved organic carbon (DOC) in the aquatic surface microlayer reflect the DOC levelsin the subsurface water.

• While the levels and enrichment of DOC in the aquatic surface microlayer generally show small variations, the levels and enrichment of particulate organic carbon (POC) vary to a great extent.

• Similarities exist between aquatic surface films, artificial semi-permeable and biological membranes regarding their structure and functioning.

• Acidification and liming of freshwater ecosystems affect DOCrPOC ratio and humic composition of the surface film, thus influencing the partitioning of pollutants across interfaces.

• Properties of lake catchment areas extensively govern DOC:POC ratio both in the surface film and the subsurface water.

• Increased UV-B irradiation changes the DOC:POC ratio in the surface film and thus affects transfer of matter across the interface.

• Transport of lipophilic, persistent organic pollutants across semi-permeable membranes is influenced by the organic composition of the solute.

• Significant passive, diffusion-mediated transport of lipophilic, organic pollutants across interfaces in aquatic ecosystems exists. Epilogue

The basic understanding of surface film functioning has been hampered by two major difficulties: (1) The dynamic properties of the films and (2) incomplete identification of the organic constituents. As Carlson (1983) wrote,

"Two factors are important to investigations of microlayer process and reactions: the first is that such inventories should represent both types and concentrations of organic materials, including assessment of possible temporal and spatial variations; the second is the availability of some NOM which represents significant fractions of the microlayer dissolved materials, and offers quantitativeand predictive possibilities. ”

Carlson emphasised the need for more serious treatment of questions dealing with surface film organic composition and effects of this composition on the properties as well as the need for larger sample quantities to reduce errors due to variations in the natural composition of the surface film. I feel that my work in surface science has been guided by Carlson ’s wise words and hope that my findings can be seen as an improvement.

I identified several difficulties with modem surface film research. I would like to mention the most severe. First, environmental research endeavours depend highly on political interests, known to take fast turns. Environmental problems commonly are long term problems. But long term studies are usually not adequately financed. This prohibits the assimilation of data collected by various researchers in large-scale ecosystem facilities. In spite of the great value and cost-effectiveness of these facilities, maintenance and operation becomes impossible over a longer time, due to financial difficulties. Since surface film dynamics depend on many external sources and sinks, large scale ecosystem studies are necessary for surface film research. Yet, this option is not frequently provided.

Second, to match data on surface film chemistry with e.g. radar backscatter, new methodology is needed. In this respect, the combination of various insitu systems, i. e. by means of the INTERFACE II platform, can be useful for gaining new insight in surface science.

36 Acknowledgements

This summary was made possible by the encouragement of Prof. Dr. Egil Gjessing, Dr. M. Ian Jenness, Dr. Don Y(Hj)eltman, Prof. Dr. Anders Sodergren, and many doctoral students who inspired me to complete this work. Comments on the manuscript were greatly appreciated. The Swedish Environmental Research Institute (TVL), Norwegian Research Council (NFR) and EC Environmental Research Directorate are acknowledged for financial support, as well as Greenpeace International, Swedish Environmental Protection Agency (SNV), Carl Tiyggers and Magnus Bergvalls Foundations.

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42 t f

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43 Dankwoord

"Maar ook een lange weg wordt stap voor stop afgelegd, de vreugde over de rijping van het werk en het bereiken van het doel wordt onderweg beleefd en.verteerd. De laatste stap is eenvoudigweg de laatste stap. ”

-Oek de Jong From Cirkel in het gras

Time to thank all of those who have contributed to my education, personal growth, and endurance needed for reaching goals like this. Some of these folks do not speak nor read the ’’universal language. ” To them I feel obliged to express my sincere gratitude in their own tongues. Hartelijk bedankt voor de vele jaren van vriendschap en vol spannende belevenissen. Tack, snalla Ni, for att jag kanner mig hemma. Danke Schon, Freunden, fur Alles durch dieser Jahren. Takk for gott samarbeid och vennlighet. In mijn jeugd was het niet moeilijk om inzicht en ontzag te verkrijgen voor de schoonheid en het belang van de natuur. Mijn vader groeide op in de ’’wildemis” als zoon van een jachtopziener. Zijn interessen in en kennis der natuur schiepen bij mij al vroeg een onverwoestbare wens om met natuurbehoud bezig te zijn. De zestiger jaren waren de tijd van wilde demonstraties en de milieurevolutie, die bijdroegen om mij de richting van milieukunde te wijzen. Ik herinner me nog hoe ik in 1972 Wim Ter Keurs ontmoette, nu professor in milieubiologie aan de Universiteit van Leiden. Hij was als stagiere bij mijn opa geweest en ontfermde zich 1972 over het natuurgebied De Horsten. De uitbouw van snelwegen en woonwijken tussen de steden van de Randstad knaagden overal aan natuurgebieden. Er was kennis en moed nodig om deze negatieve ontwikkeling te stoppen. Op weg om te promoveren als doktor in een milieuwetenschap, hoop ik een bijdrage te kunnen maken aan de bescherming van bestaande natuur. Gekant met teleurstellingen en vreugde, heeft de weg mij langzaam maar zeker toch naar deze mijlpaal geleidt. De vele mensen die mij langs de weg aangemoedigd hebben zijn hier niet allemaal op te noemen voor gebrek aan papier. Maar vooral mijn ouders, Dra. en Drs. Walter, Ter Keurs, Aart Koster, de jongens van de HAS, tante Annie en ome Jan en Caroline Bakker ben ik daarvoor zeer dankbaar. At a US college in the Appalachian Mountains, far away from the North Sea and dutch canals, I began to realize the importance of water. Dr. Van Gundy, who taught limnology, got me involved in a special topic study on water quality. His lectures were inspiring, and my course was set. Thanks, Don, Ian, Jim, Larry, Greg, PK, and your families, and fellow students for the Bio Club picnics, hikes, camping trips, caving, climbing Seneca Rocks, Woods O’, Wilderness Co-op, rafting, maple syruping, paddling, and pancake breakfasts. I had fun and learned a lot.

44 1«

Kort efter min ankomst till Sverigefortsatte jag utbildningen vid limnologen i Lund. Dar motte jag ett glatt gang som alltid hade rid att diskutera saker och ring. Tack, Gunnar Andersson, for din talamod medans jag kikade pa faglar och vass och klagade ibland, Leo, for att jag fick plocka 2000 Chironomider fran sjosediment som mitt forsta limniska arbete samt hela ganget for de ’’onyttiga” kakor och trevliga raster. Tack, Pelle Larsson, for din kamratskap och goda ideer, doktorandganget och personalen vid ekotox-ekokem for att jag kande mig valkommen vid mina "drop-in" besdk fran Smaland. Ja, Smalandsnaturen drog familjen uppat landet. Nu var det langt till civilationen, d v s svarforaldrama, Sjobo, den blivande Oresundsbro och Lunds domkyrka. Jag saknar nog svarforaldrama mest. Tack, Sissi, Lars och Rickard for erat kontinuerliga stdd och otroliga gastfrihet. This thesis was made possible by a Human Capital and Mobility Grant from the European Community used to study surface films (and Norwegian highways) during 1994. Many trips were made between "my” office at the Norwegian Institute for Water Research in Oslo and the HUMEX site at the westcoast. Thanks, Egil Gjessing and Dick (RE) Wright for this opportunity. I am also grateful for the help with equipment and stimulating conversations at NTVA. The encouragement of friends and "doctors to become ”, mainly during work at the HUMEX site, was invaluable, as was the "hidden” sense of pride and soft management of my parents. I apologise for having been a little less friendly to my colleagues in Aneboda during the past months.. Those who possibly suffered most during the time I spent on my studies are my wife Anette, and children Mats, Rasmus, and Ron) a. Anette, not having to pull out the old typewriter this time to help me type the manuscript, did have to live with me and saw to it that I ate a bite sometimes. Thanks!!! I thank my family for letting me pull myself together and finish something once. And I apologise for not listening, playing ball, remembering to pick up the kids at day-care, feeding the dog, paying the bills, and not doing all other things that I was supposed to do. It is almost over. The overheated fax and internet lines can soon cool off. It has been quite a challenge. De laatste stap, de laatste stap... "Luctor et Emergo "

45 List of Used Abbreviations

°c degrees Celcius pm micrometer (10-6 m) B.C. Before Christ C Carbon C02 carbon dioxide DCF Dialysis Concentration Factor DDT l,l,l-trichloro-2,2-bis-(p-chlorophenyl) ethane and related compounds DOC Dissolved Organic Carbon DOM Dissolved Organic Matter Ef Enrichment Factor (quotient surface film over subsurface water contents) FM Frequency Modulated transmission (radio) HMW Heavy (High) Molecular Weight HS Humic Substances km hr" 1 kilometres per hour LMW Light (Low) Molecular Weight LxWxH Length x Width x Height m/s metres per second n 2 nitrogen gas NMR Nuclear Magnetic Resonance Spectroscopy NOM Natural Organic Matter o 2 oxygen gas PAH Polycyclic Aromatic Hydrocarbons PCB PolyChlorinated Biphenyls PE PolyEthylene PH -log (H+ concentration) POC Particulate Organic Carbon QSAR Quantitative Structure-Activity Relationships RC Radio (Remotely) Controlled SAR Synthetic Aperture Radar TOC Total Organic Carbon unpubl. unpublished UV Ultraviolet (radiation) XAD-2 miroporous styrene-divinylbenzene polymer resin XAD-4 styrene-divinylbenzene polymer resin XAD-8 methyl methacrylate polymer resin The following is a list of Doctoral theses from the Department of Chemical Ecology and Ecotoxicology, Department of Ecology, University of Lund, Sweden.

1. ANDERS SODERGREN. Transport, distribution, and degradation of organochlorine residues in limnic ecosystems (defended at the Dept, of Limnology). 23 May 1973. 2. GORAN BENGTSSON. Ecological significance of amino acids and metal ions, a microanalytical approach (defended at the Dept, of Zooecology) 24 May 1982. 3. CARITA BRINCK. Scent marking in mustelids and bank voles, analysed of chemical compounds and their behavioural significance (defended at the Dept, of Zooecology) 17 May 1983. 4. ANDERS TUNLID. Chemical signatures in studied of bacterial communities. Highly sensitive analyses by gas chromatography and mass spectrometry, 3 October 1986. 5. ANDERS THUREN. Phthalate esters in the environment: analytical methods, occurrence, distribution and biological effects, 4 November 1988. 6. PETER SUNDIN. Plant root exudates in interactions between plants and soil micro-organisms. A gnotobiotic approach, 16 March 1990. 7. ANDERS VALEUR. Utilization of chromatography and mass spectrometry for the estimation of microbial dynamics, 16 October, 1992. 8. HANS EK. Nitrogen acquisition, transport and metabolism in intact ectomycorrhizial associations studied by ^N stable isotope techniques, 14 May 1993. 9. ROLAND LINDQUIST. Dispersal of bacteria in ground water - mechanisms, kinetics and consequences for facilitated transport, 3 December 1993. 10. ALMUT GERHARDT. Effects of metals on stream invertebrates, 17 February 1995. 11. OLOF REGNELL. Methyl mercury in lakes: factors affecting its production and partitioning between water and sediment, 21 April 1995. 12. PER WOIN. Xenobiotics in aquatic ecosystems: effects at different levels of organisation, 15 December 1995. 13. GORAN EWALD. Role of lipids in the fate of organochlorine compounds in aquatic ecosystems, 18 October 1996. 14. JOHAN KNULST. Interfaces in aquatic ecosystems: Implications for transport and impact of anthropogenic compounds, 13 December 1996.