CHAPTER 22 • Chemometric Applications to Seawater Analysis
413
lurgical industry, mainly present in the northern part of France, the German Ruhr
area and industrial towns in the middle of the United Kingdom. A major part of Pbrich particles was found to be associated with automotive exhaust. Less important
sources of metal pollution were shown to be cement production and refuse incineration.
22.2.1.4
Water Micro/ayer
A study was performed in the North Sea (English Channel and Celtic Sea) to characterize individual particles and to find possible correlations between the sea surface
microlayer and the bulk waters (Xhoffer et al.1992). Sea surface microlayer (thickness
between 0.1 and 3.0 Ilm) is characterized by chemical, physical and biological properties different from those of the water underneath. This layer is the main communication channel for transfer of matter between atmosphere and water. The transport between surface and sea body is due to processes of diffusion, convection, upwelling and
rising of bubbles. The dispersion of the microlayer into the bulk waters occurs by sinking of particles and dissolution of water-soluble molecules, while bubble bursting and
generation of aerosol by wind action are responsible for the transport into atmosphere.
From the atmosphere matter is transferred to microlayer through wet or dry deposition processes. Many pollutants, such as petroleum hydrocarbons and chlorinated
hydrocarbons, are concentrated in the micro layer together with proteinaceous material and organic acids that can provide complexing sites for many heavy metals thus
often present in microlayer. Samples of microlayer and bulk water were collected in
five positions in the North Sea: the data set contained more than 3 000 individual particles. The samples were analysed by electron-probe X-ray microanalysis (EPXMA)
and laser microprobe mass analysis (LAMMA), techniques able to give indication if a
specific element is uniformly distributed over all the particles. Eight different types
of particles were individuated: alumino silicate, Ca-rich aluminosilicates, Ca carbonates, silicates, organic particulate matter, Fe-rich particulate and Ti-rich particulate
and a miscellaneous one. The results are compared with data from particles of atmosphere and river and related to the most probable sources: minerals, river waters, silicon-rich diatom, skeletal fragments of sponge, yeasts, bacteria, organic particulate
(dead organism), skeleton of diatoms, coccolith, phytoplankton, etc. The concentration of dissolved silicate is lower at the surface and increases with depth, because of
the decomposition of organisms. Biological activity in sea water generates an extremely
high chemical mobility of silica, while calcite and aragonite are mainly present in
oceans. Resuspension of a Ca-rich particulate fraction into marine atmosphere can
occur during sea-spray processes and reactions with species S-rich (as S02' H2S04 or
dimethylsulfoxide) present in the atmosphere can take place with formation of CaS04.
The variations of the particle types among the samples was studied by PCA. The first
two PCs explain more than 94% of the total variance. The loadings (Fig. 22.3a) of the
first PC explains the differences between aluminosilicates and organic and metal-rich
particles, while PC2 shows high positive loading on both the Ca-rich and Ca-Si-rich
particles types, that probably have the same source. The scores (Fig. 22.3b) and the
dendrograms (Fig. 22.4) show good correlation between microlayer content and bulk
seawater. For the five stations four clusters can be identified, composed as follows:
413
lurgical industry, mainly present in the northern part of France, the German Ruhr
area and industrial towns in the middle of the United Kingdom. A major part of Pbrich particles was found to be associated with automotive exhaust. Less important
sources of metal pollution were shown to be cement production and refuse incineration.
22.2.1.4
Water Micro/ayer
A study was performed in the North Sea (English Channel and Celtic Sea) to characterize individual particles and to find possible correlations between the sea surface
microlayer and the bulk waters (Xhoffer et al.1992). Sea surface microlayer (thickness
between 0.1 and 3.0 Ilm) is characterized by chemical, physical and biological properties different from those of the water underneath. This layer is the main communication channel for transfer of matter between atmosphere and water. The transport between surface and sea body is due to processes of diffusion, convection, upwelling and
rising of bubbles. The dispersion of the microlayer into the bulk waters occurs by sinking of particles and dissolution of water-soluble molecules, while bubble bursting and
generation of aerosol by wind action are responsible for the transport into atmosphere.
From the atmosphere matter is transferred to microlayer through wet or dry deposition processes. Many pollutants, such as petroleum hydrocarbons and chlorinated
hydrocarbons, are concentrated in the micro layer together with proteinaceous material and organic acids that can provide complexing sites for many heavy metals thus
often present in microlayer. Samples of microlayer and bulk water were collected in
five positions in the North Sea: the data set contained more than 3 000 individual particles. The samples were analysed by electron-probe X-ray microanalysis (EPXMA)
and laser microprobe mass analysis (LAMMA), techniques able to give indication if a
specific element is uniformly distributed over all the particles. Eight different types
of particles were individuated: alumino silicate, Ca-rich aluminosilicates, Ca carbonates, silicates, organic particulate matter, Fe-rich particulate and Ti-rich particulate
and a miscellaneous one. The results are compared with data from particles of atmosphere and river and related to the most probable sources: minerals, river waters, silicon-rich diatom, skeletal fragments of sponge, yeasts, bacteria, organic particulate
(dead organism), skeleton of diatoms, coccolith, phytoplankton, etc. The concentration of dissolved silicate is lower at the surface and increases with depth, because of
the decomposition of organisms. Biological activity in sea water generates an extremely
high chemical mobility of silica, while calcite and aragonite are mainly present in
oceans. Resuspension of a Ca-rich particulate fraction into marine atmosphere can
occur during sea-spray processes and reactions with species S-rich (as S02' H2S04 or
dimethylsulfoxide) present in the atmosphere can take place with formation of CaS04.
The variations of the particle types among the samples was studied by PCA. The first
two PCs explain more than 94% of the total variance. The loadings (Fig. 22.3a) of the
first PC explains the differences between aluminosilicates and organic and metal-rich
particles, while PC2 shows high positive loading on both the Ca-rich and Ca-Si-rich
particles types, that probably have the same source. The scores (Fig. 22.3b) and the
dendrograms (Fig. 22.4) show good correlation between microlayer content and bulk
seawater. For the five stations four clusters can be identified, composed as follows: