The Impact of Lake-level Fluctuations on the Sediment Composition

Lithological and granulometric investigations of the surface and short core sediments in L. Martiska (northeastern Estonia) showed that variations in the grain-size parameters and LOI content were influenced by the changes in deposition conditions during the regression and transgression phases monitored in the lake since the 1960s. During the regression and transgression phases displacement of the erosion-transport-accumulation zones in the lake took place depending on the bottom topography. The water level fluctuations are especially clearly reflected in grain-size variations in cores from peripherial area.     

Historical changes in the concentrations of polycyclic aromatic hydrocarbons (PAHs) in Lake Peipsi sediments

The distribution of 11 individual polycyclic aromatic hydrocarbons (PAHs) was analysed in a (210)Pb dated sediment core from the deepest area of Lake Peipsi and in four surface sediment samples taken from littoral areas. According to the concentrations in the core three groups of PAHs may be distinguished: (1) relatively stable concentrations of PAHs within the whole studied time interval; (2) very low concentrations in sediments accumulated before intensive anthropogenic impact (from 19th century up to the 1920s) following a slight increase and (3) an overall increase in PAH concentrations since the 1920s up to the present. Comprehensive analysis of PAHs in the core and monitoring data obtained in the 1980s together with the lithology of sediments show that an increase of anthropogenically induced PAHs correlates well with the history of fuel consumption in Estonia and speaks about atmospheric long-distance transport of PAHs. The continuous increase of PAH concentrations since the 1920s do not support the earlier hypothesis about the dominating impact of the oil shale fired power plants near the lake, because their emissions decreased significantly in the 1990s. The concentration of PAHs in the deep lake core sample correlates well with the content of organic matter, indicating absorption and co-precipitation with plankton in the sediment.     

Survey of dioxin sources in the Baltic Region (extended summary)

The present paper summarises the results of the project: 'Survey of Anthropogenic Sources of Dioxins and Furans in the Baltic Region'. As a part of the project, inventories have been carried out in Estonia, Latvia, Lithuania and Poland by applying the toolkit for quantification of dioxin and furan releases developed by UNEP Chemicals. The main route of direct releases to the environment is emission to air. Total emission to air from Poland was estimated at 490 (88-1,300) g I-TEQ/year, whereas the emissions from Estonia, Latvia and Lithuania were estimated as being 14 (2.4-54), 23 (2.6-63) and 17 (2.6-38) g I-TEQ, respectively. In general, the uncertainty on the estimates is very high, and recommendations regarding further development of the inventories have been made, and measures for reducing the releases have been provided.     

森林反射系数模型:理论和应用

森林反射系数模型有助于林区上空卫星图像的判读.本文简要描述了一种多目标森林反射系数模型及其基本思路、模型输入和输出选项.通过以下模拟实例,论证了在森林遥感中运用该模型的可能性:森林反射系数对年龄的依从关系、森林反射系数的季节变化、落叶对森林反射系数的影响、叶绿素和水分指数的敏感性(分别关于叶片中叶绿素和水分),以及由于林分参数的变化而产生的指数的不确定性.如果与大气辐射传送和传感器校准模型一起使用,森林反射系数模型可应用于卫星图像辅助森林生态学和健康评价、森林清查及经营.     

Forest reflectance modeling: theoretical aspects and applications

Forest reflectance models are able to contribute to the interpretation of satellite images over forested areas. A multipurpose forest reflectance model, its basic ideas, model input and output options are briefly described. The possibility to apply the model in forest remote sensing is demonstrated through the following simulation examples: the age dependence of forest reflectance, the seasonal course of forest reflectance, defoliation effects on forest reflectance, sensitivity of chlorophyll and water indices with respect to leaf chlorophyll and water content, respectively, and uncertainties in these indices introduced by the variation in stand parameters. When used together with the atmospheric radiative transfer and sensor calibration models, the forest reflectance model is applicable in satellite-imagery-aided forest ecology and health assessment, forest inventory and management.