Lindfors, V. & Laurila, T. 2000. Biogenic volatile organic compound (VOC) emissions from forests in Finland. Boreal Env. Res. 5: 95–113.
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Kettunen, A., Kaitala, V., Alm, J., Silvola, J., Nykänen, H. & Martikainen, P. J. 2000. Predicting variations in methane emissions from boreal peatlands through regression models. Boreal Env. Res. 5: 115–131.
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Nieminen, M. 2000. A simple device for automatic sampling of runoff for quality monitoring during rainfall events. Boreal Env. Res. 5: 133–136.
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Uitto, A. 2000. Diurnal and vertical grazing activity of mesozooplankton during summer on the SW coast of Finland. Boreal Env. Res. 5: 137–146.
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Savchuk, O. P. 2000. Studies of the assimilation capacity and effects of nutrient load reductions in the eastern Gulf of Finland with a biogeochemical model. Boreal Env. Res. 5: 147–163.
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Leivuori, M., Jokòas, K., Seisuma, Z., Kulikova, I., Petersell, V., Larsen, B. Pedersen, B. & Floderus, S. 2000. Distribution of heavy metals in sediments of the Gulf of Riga, Baltic Sea. Boreal. Env. Res. 5: 165–185.
Abstract
Full text (pdf format)
Lindfors, V. & Laurila, T. 2000. Biogenic volatile organic compound (VOC) emissions from forests in Finland. Boreal Env. Res. 5: 95–113.
Kettunen, A., Kaitala, V., Alm, J., Silvola, J., Nykänen, H. & Martikainen, P. J. 2000. Predicting variations in methane emissions from boreal peatlands through regression models. Boreal Env. Res. 5: 115–131.
Nieminen, M. 2000. A simple device for automatic sampling of runoff for quality monitoring during rainfall events. Boreal Env. Res. 5: 133–136.
Uitto, A. 2000. Diurnal and vertical grazing activity of mesozooplankton during summer on the SW coast of Finland. Boreal Env. Res. 5: 137–146.
Savchuk, O. P. 2000. Studies of the assimilation capacity and effects of nutrient load reductions in the eastern Gulf of Finland with a biogeochemical model. Boreal Env. Res. 5: 147–163.
Leivuori, M., Jokòas, K., Seisuma, Z., Kulikova, I., Petersell, V., Larsen, B. Pedersen, B. & Floderus, S. 2000. Distribution of heavy metals in sediments of the Gulf of Riga, Baltic Sea. Boreal. Env. Res. 5: 165–185.
We present model estimates of biogenic volatile organic compound (VOC) emissions from the forests in Finland. The emissions were calculated for the years 1995–1997 using the measured isoprene and monoterpene emission factors of boreal tree species together with detailed satellite land cover information and meteorological data. The three-year average emission is 319 kilotonnes per annum, which is significantly higher than the estimated annual anthropogenic VOC emissions of 193 kilotonnes. The biogenic emissions of the Finnish forests are dominated by monoterpenes, which contribute approximately 45% of the annual total. The main isoprene emitter is the Norway spruce (Picea abies) due to its high foliar biomass density. Compared to the monoterpenes, however, the total isoprene emissions are very low, contributing only about 7% of the annual forest VOC emissions. The isoprene emissions are more sensitive to the meteorological conditions than the monoterpene emissions, but the progress of the thermal growing season is clearly reflected in all biogenic emission fluxes. The biogenic emission densities in northern Finland are approximately half of the emissions in the southern parts of the country.
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Frequently measured data from a boreal fen was used to test how regression models predict the spatial and temporal variations in methane emissions. In the spatial microscale, emissions were lowest from high hummocks with low water table and highest from the intermediately moist lawn with a high sedge cover. Seasonal variations were strong, but diurnal variations weak. The importance of episodic emissions increased from wet microsites to hummocks. The regression models explained the temporal pattern of methane emissions quite satisfactorily for flarks and low hummocks, but less satisfactorily for high hummocks. For independent data sets, the goodness of fit values were usually low. Episodic pulses and diurnal variations were not captured by the models and the models overestimated the spring emissions and underestimated midsummer high emissions.
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The construction and operation of a new device for automatic sampling of runoff during rainfall events is described. It is easily made, simple to use, not vulnerable to operational disturbances, and inexpensive, thus allowing use at many sites with reasonable costs. The basic principle is to use the weight of the rain to trigger the sample collection. To test the utility of the device, runoff during rainfall events was collected at three catchments over the summer of 1994.
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Diurnal and vertical grazing activity of the most dominant mesozooplankton species was studied during the summer 1987 in the coastal area of the SW Finland. The samples for gut fluorescence measurements (Chl-a + phaeopigments) were taken from five depths between the surface and 35 m depth four times a day. Chl-a concentration was higher in the upper water layer of 10 m than at 20 m depth, and higher in the daytime (1300 and 1900 hrs samplings) than by night (0100 and 0700 hrs samplings). The ambient Chl-a concentration explained 34% to 90% of the variation in the gut pigment contents of Eurytemora affinis, Bosmina longispina maritima and Synchaeta spp., when the whole data was examined using the linear regression analysis. In Acartia spp. this relation was insignificant. The gut pigment contents of copepods, B. longispina maritima and Synchaeta spp. were higher in the upper water layer (0 to 10 m) than in the deeper layer (20 to 35 m), but only by night. Diurnal variation was not found within either of the water layers or vertically between the layers in the daytime. The gut pigment content of the cladocerans Podon/Pleopsis spp. and Evadne nordmanni exceeded several times that of copepods and B.longispina maritima. The estimated daily specific ingestion rate (ingestion% of body carbon) varied from 2% to 12% in Acartia spp. and 3% to 28% in E. affinis, the highest percentages being found in the upper water layer. For Pseudocalanus minutus enlongatus, which was mostly found in the deeper depths, the corresponding percentage was only 4%. Carbon originating from other sources than phytoplankton was likely to be important for the nutrition of copepods.
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A model of the nitrogen and phosphorus biogeochemical cycles was applied to the Gulf of Finland for summer and autumn 1991 and validated with concurrent field observations. Estimates derived from modeled biogeochemical fluxes indicated that in August a relatively small easternmost area can assimilate up to 70%–100% of the nitrogen load from the St. Petersburg region. Phosphorus assimilation is equivalent to 160%–260% of the land load. In November, the nitrogen retention decreases to about 4%, while the phosphorus export exceeds the entire land input by 12% due to internal (sediment) loading. The nutrient load reduction scenarios imply that reduction of nitrogen load would result in locally reduced eutrophication and decreased nitrogen export into the open Gulf, while phosphorus reduction would increase assimilation of phosphorus imported into the easternmost area from the west.
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A large number of sediment samples (totally 138) were studied in 1991–1996 to clarify the role of sediments as a sink of heavy metals in the Gulf of Riga. The samples were analysed for total content of carbon, organic carbon, cadmium, lead, copper, zinc and mercury. Certain additional elements such as aluminium, lithium, iron, manganese, chromium, nickel, titanium and vanadium were also measured from some of the samples from the accumulation areas to enable combination with corresponding data from other parts of the Baltic Sea. The non-mineralogical portion of the heavy metals of some samples was estimated with nitric acid leaching. Heavy metal data for mean concentrations are shown separated into accumulation and non-deposition areas for 1, 2 and 5 cm sample intervals. Spatial distribution patterns are shown for the topmost 5 cm samples. The highest concentrations of metals are mainly found in the mud accumulation areas and in some specific cases, such as cadmium, in the near-shore areas. Lead, copper and zinc show a more widespread distribution over the whole Gulf. For copper and cadmium the presented vertical distributions of selected profiles show decreased accumulation trends during the past 30 years, while for other elements no similar pattern is identified. Comparisons with the Gulf of Bothnia and Gulf of Finland show that total concentrations of lead, copper and zinc are lower in the Gulf of Riga and cadmium and mercury are in the same range as those in the Gulf of Bothnia and Gulf of Finland.
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