Mercury determination in suspended matter and bottom sediments of ponds,reservoirs and rivers are important for assessing the level of their pollution and study of the distribution,transport and transformation of mercury in ecosystems.Snow cover,as a natural storage of pollutants,is the most informative for evaluation of atmospheric mercury pollution during the winter period.Determination of mercury in solid particles of snow gives a quantitative characteristic of Hg emission from burning coal and waste,dust deposition,etc.The aim of our study was to optimize parameters of sample preparation and instrumental determination for solid environmental samples,such as sediments,suspended and particulate matter of freshwater and snow.Parameters of microwave decomposition in MARS-5 were unified for different kind of environmental solid samples.Mercury determination was performed on an Hg analyzer Mercur DUO Plus(Analitik Jena,Germany)both in atomic fluorescence and atomic absorption mode.It was shown that CV AFS is the preferred method for determination of mercury in comparison with atomic absorption method under these parameters.Significant matrix influence in clay sediments causes necessity to use the amalgamation step,regardless of the mercury concentration in the samples.That additional step is not required for samples of suspended and particulate matter with less organic component.The accuracy and precision of mercury determination is confirmed by analysis of certified reference materials SDPS-1(certified value of mercury is 0,013 ± 0,002 ? kg/g,the determined mercury value is 0,0128 ± 0,0002 ?kg/g).These conditions of sample preparation and mercury determination were applied for sediment samples of Novosibirsk Reservoir.The results showed that the current level of mercury in sediments of the Berdsky Bay did not exceed background values for freshwater for all studied hydrological periods.The highest mercury concentration(0.045 ?kg/g)was observed in October at the sampling point at the exit of the Berdsky Bay.Most likely this is due to the arrival of mercury in sediments detritus benthic organisms that have accumulated mercury during the summer season.So there are prerequisites for the accumulation of mercury on the food chain that requires further study.