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Climatic conditions in Latvia support the process of overgrowing of freshwater bodies due to natural and anthropogenic eutrophi cation process - sapropel or gyttja is the freshwater organic sediment transformed in genetic processes and mixed with mineral components. From economic point of view this sediment is subterranean renewable resource that can be used in agriculture, construction, chemical processing, cosmetology and medicine. Recultivation of overgrown lakes can be provided by sapropel removal, but the pumping, storage, logistics and processing should be planned carefully. Thus more suitable habitats for fish can be restored and landscape becomes more attractive; benefits can be gained by investing minimal resources. Remediation works in lakes of Latvia with the water depth less than 3 m can to be promoted as the lake bed is filled with organic rich sediments. Significant economic benefits from the resources extracted can be achieved by project developers, municipalities and other stakeholders. However, these works should consider price fluctuations and logistical aspects as well as the impact to the environment. The aim of this article was to provide comparison of various sapropel extraction scenarios by analysing costs, removal rates and amount of the resource based on Lake Pilvelis economic calculations example. [ABSTRACT FROM AUTHOR]

The terms "sapropel" or "gyttja" are used to describe bottom deposits of freshwater bodies rich in the organic matter (organic matter content exceed 15%) which are formed from the remains of water animals and vegetation mixed with mineral components. Sapropel has a fine disperse and plastic structure and it can be used in various fields such as agriculture, livestock farming, balneology, cosmetology etc. Germination tests are used for determination of germination potential and quality of a selected seed lot. Several factors such as diseases, age of seeds, mechanical damage of seeds, excessive moisture or drought during storage can affect the behaviour of seeds germination. The rate of germination is very significant as it indicates field planting value of seeds. Detection of influencing factors and their intensity on seed germination is especially significant research due to its practical importance in agriculture and gardening. The aim of this study was to determine the influence of sapropel (gyttja) on the germination of Trifolium pratense (red clover) seeds in the presence of copper contamination. Methodology of the study involved selection and preparation of Trifolium pratense seeds, selection of peaty sapropel obtained from Lake Pilvelis (Latvia) and preparation of germination tests. To assess the influence of sapropel on seeds germination half of seeds were germinated in water, while another part - in sapropel. In addition, to estimate the interaction of sapropel with metallic elements the study was done by adding copper in various Cu2+ target concentration (i.e., 0, 40, 70, 100, 130, 200, 400, 600, 800, 1000 mg/L) into water or sapropel. Seed germination was done by using "Phytotestkit" plates. Seeds were germinated in thermostat at the temperature 22°C for 7 days. Developed radicles, hypocotyls and shoots were measured. Obtained results showed positive influence of sapropel on Trifolium pratense seeds germination and development as well as sapropel addition reduced negative effects caused by metal contamination on seeds endurance affirming potential use of sapropel as effective soil amendment. [ABSTRACT FROM AUTHOR]