Gulf of Riga

Nitrogen concentrations in sediment; Carbon concentrations in sediment; Inorganic chemical composition of sediment or rocks

Elemental analysers; atomic absorption spectrometers; spectrophotometers

During a three year period (2001-2003) samples of surface sediments (nepheloid layer) for trace metals, nutrients, chlorophyll a and other supporting analysis were collected at three stations in the Gulf of Riga. At the station 119 (57o 18.00' N, 23o 51.00' E) samples were taken 40 times, at 135 (57o 24.00' N, 23o 29.00' E) and 137A (57o 21.00' N, 24o 05.00' E) samples were taken 9 and 11 times respectively. Sediment cores were taken by Kajak gravity corer on the board of research vessel 'Antonija'. The top 2 - 3 mm of sediment core (nepheloid layer) was collected for analysis. For trace metal analysis samples were totally digested by hydrofluoric acid, nitric acid and hydrogen peroxide. Trace metals were detected by atomic absorption spectroscopy - in flame and graphite furnace. Chlorophyll a was extracted with ethanol and determined by spectrophotometer. Total carbon and total nitrogen were analyzed by CHNS analyzer. For total phosphorus determination samples were heated at 500 oC. Total and inorganic phosphorus were extracted with hydrochloric acid and determined by spectrophotometer. Organic phosphorus was residual between total and inorganic phosphorus. Biologically available silica in sediment surface was determined colorimetrically with molybdate method after extraction with sodium carbonate solution. The final data are related to dry weight with SD.

Latvian Institute of Aquatic Ecology
Voleru str.4
Riga

LV-1007
Latvia