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1 Polish Geological Institute Special Papers

1 2008

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A new map of the Neva Bay bottom sediments and technogenic objects under the result of side-scan sonar profiling

Spiridonov M. A., Ryabchuk D. V., Kropachev Y. A., Nesterova E. N., Zhamoida V. A., Vallius H., Kotilainen A.

Polish Geological Institute Special Papers

2008

Vol. 23

95-107

In summer 2004, Department of Marine and Environmental Geology of VSEGEI carried out investigations of the Neva Bay bottom surface east of the St. Petersburg Flood Protective Dam using a side-scan sonar system. The main aim of this experimental work was the creation of a new “factographical” map of bottom sediments and different types of technogenic objects. State geological surveys of the Neva Bay bottom were carried out by VSEGEI in 1987–1989. Besides, geoenvironmental investigations were conducted here in 1993–1995 and 2000–2002. As a result, a set of maps of bottom sediments based on hundreds of sampling stations (both cores and grab-sampler) were compiled. Side-scan investigations of 2004 allowed more exact recognition of the bottom sediment distribution. Furthermore, in some places new data permit to suppose that the sedimentary conditions have changed here during the last decades as a result of high technogenic load, including Flood Protective Dam influence. In summer 2004 there were a joint expedition of the VSEGEI and the Geological Survey of Finland (GTK). Altogether 10 sampling stations from the mud accumulation areas were sampled with a use of Niemisto corer. Cores were sliced in 1 cm samples and analyzed in chemistry laboratory of GTK (Finland) – gamma spectrometry for 137Cs, ICP-AES and ICP-MS, whereupon important results about heavy metals concentration and distribution were received.