Single particle characterisation of inorganic and organic North Sea suspension

Automated electron probe X-ray micro-analysis and scanning transmission electron microscopy were used to characterise the chemical and mineral composition of individual suspended particles, collected in the Southern Bight of the North Sea. The suspended matter contains 13 particle types, which can be classified in seven genetic groups: (i) terrigenous (aluminosilicate and calcium carbonate particle types); (ii) terrigenous–biogenic (silica type); (iii) terrigenous–hydrogenous (Fe-rich type); (iv) biogenic–authogenic (S-containing type); (v) terrigenous–anthropogenic (Ti- and Al-rich types); (vi) biogenic–anthropogenic (organic type); and (vii) terrigenous–anthropogenic–authogenous (heavy metal rich type). Staining the suspended matter with RuO4, revealed extra information about their organic matter content. Organic matter coatings were detected on all of the suspended particles. A high concentration of organic material was detected in all Mn-rich, Cr-rich, Zn-rich and Ni-rich particles. A strong correlation between organic- and heavy metal-rich particles which was revealed by factor analysis, may indicate that organic matter is complexing heavy metals. Organic material in the southern part of the North Sea is least abundant in fall and winter, and most common, but also very variable, during primary bioproduction boom in spring. The amount of suspended matter was relatively constant throughout the year close to the Westerschelde estuary.