Methods

Abstract

This article describes the survey methods used in the project 'Lake sediments as a carbon store'. Lakes for the study were selected to repsesent the average lake water quality in Finland. This article gives the basis for lake selection. For each lake basin, estimates were made of the amount of organic sediments and carbon and their respective accumulation rates. Field methods, such as acoustic sounding, coring and sampling are described as well as the preparation of core for laboratory analysis. Physical analyses included water content, loss on ignition, dry bulk density and grain size. The results of dry bulk density were calculated. The article gives the basis for calculation and equations used. Chemical studies included carbon, nitrogen and hydrogen analyses (LECO CHN-600), and ICP-analyses carried out following microwave assisted nitric acid digestion. Sediment cores were dated by either the palaeomagnetic method or the radiocarbon method, or by age estimation based on deglaciation or basin isolation and core stratigraphy. Both methods and the principles of age estimation are described.