The project is financed by The Research Council of Norway and is a co-operation between IFE and NIVA.

The river Glomma, SE Norway, drains a 41 800 km² large area and terminates into the shallow Glomma estuary. The total agricultural area in the catchment is about 1500 km² and mainly located in the southern part of the area. The estuary is affected by eutrofication. The lower part of the river was industrialised in the beginning of the 20th century, the main activity being pulp and paper industry, and a zinc smelter. One of the main industries today is a chromium titanium plant situated close to the river mouth. There is also a big plant for incineration of waste in this industrial area. The estuary is today mainly influenced by material transported by the river and autochthonous material from the highly productive conditions induced by the river. In the years 1986 to 1995 the river Glomma carried annually between 120 · 103 and 440 · 103 tonnes of suspended particulate matter.

The yearly contribution of lead (Pb) by river Glomma is about 10-20 tonnes and is a mixture of natural Pb from mineral particles, atmospherically longtransported Pb and Pb from local antropogenic sources. Studies of the bottom sediments in the estuary show an increasing concentration av Pb with increasing distance from the river mouth. The sedimentation is considerable in the inner parts of the estuary and Pb isotopes show that it is natural Pb adsorbed to mineral particles which sediment here. Locally are the sediments affected by traffic Pb from the town of Fredrikstad, but atmospherically longtransported Pb transported with the river water sediment in the outer parts of the estuary. Analysis indicates that much of the atmospheric Pb transported by Glomma is transported in soluble form. With the ability to adsorb to particles it is possible that Pb adsorbs to small particles, or particles with low weight, in the estuarine mixing zone with following long transportation before sedimentation.

Analysis of material from sedimentary traps show that the sedimentation pattern varies over the year. At high flood in Glomma the river water is pressed far out in the estuary and with following sedimentation of mineral Pb in its outer parts. Simultaneously, the high flood causes resuspension of sediments earlier deposited in the river over the year, including the local contribution of traffic Pb from the town of Fredrikstad. There was also a positive significant correlation between Pb and the C:N ratio, δ¹³C and δ¹⁵N ratios, though weaker, which clearly indicate a positive relationship between Pb and type of organic matter. The strong significant negative correlation between ²⁰⁶Pb/²⁰⁴Pb ratio and δ¹⁵N and δ¹³C ratios, further suggest a connection or preferences for adsorption between Pb and organic matter from specific sources.