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Vertical distribution of trace elements in fresh water, saline water and sediments from Lake Rørholtfjorden, Norway

1982; Elsevier BV; Volume: 36; Issue: 3-4 Linguagem: Inglês

10.1016/0009-2541(82)90055-9

1872-6836

K. Jørstad, Brit Salbu, E. Roaldset,

Heavy metals in environment

Instrumental and radiochemical neutron activation analysis have been applied for the determination of up to 31 elements in a vertical profile through fresh water, saline water and bottom sediments of Rørholtfjorden, a branch of Lake Tokke, southeast Norway. In order to elucidate the distribution of elements and also fractionation and diffusion processes in the bottom sediments, desorption experiments, grain-size and mineralogical analyses have been included in the analytical program. The average enrichment factors for the elements in the anaerobic saline water relative to the fresh water are determined. Except for the rare-earth elements (REE) and iron, the factors are in agreement with literature data. The high amount of REE in the saline water may be associated to organic matter. In the uppermost part, especially above the thermocline, enrichment of some elements reflects the recent drainage-water composition. Diffusion processes influence the distribution of several elements in the lower part of the freshwater layer. A heterograde distribution for most elements investigated is seen in the saline water. The different analyses of the sediment samples indicate that the sediment core may be divided into an ankerite-bearing top layer, a intermediate layer and a pyrite-rich bottom layer. Eigenvector analysis confirms this indication. A certain fractionation of light and heavy REE is suggested by cluster analysis. According to the desorption experiments a stronger association of heavy REE to the mineral structure in the bottom layer, compared to the top layer of the sediments, is indicated and traces of only slightly soluble minerals enriched in heavy REE may be present in the bottom layer. Removal of Na from pore water during albite diagenesis may also be indicated and there are no signs of leaching of the bottom sediments by upward flow of artesian groundwater.