Forsius, M., Johansson, M., Posch, M., Holmberg, M., Kämäri, J., Ahti Lepistö, A., Roos, J., Syri, S. & Starr, M. 1997. Modelling the effects of climate change, acidic deposition and forest harvesting on the biogeochemistry of a boreal forested catchment in Finland. Boreal Env. Res. 2(2): 129–143.
Abstract
Gottschalk, L. & Krasovskaia, I. 1997. Climate change and river runoff in Scandinavia, approaches and challenges. Boreal Env. Res. 2(2): 145–162.
Abstract
Zhang, Z., Wu, H. & Wang, Y. 1997. Variability of climatic and ice conditions in the Bohai Sea, China. Boreal Env. Res. 2(2): 163–169.
Abstract
Frycklund, C. & Jacks, G. 1997. Iron and artificial recharge of groundwater. Boreal Env. Res. 2(2): 171–181.
Abstract
Itkonen, A. & Olander, H. 1997. The origin of the hypertrophic state of a shallow boreal shield lake. Boreal Env. Res. 2(2): 183–198.
Abstract
Kløve, B. 1997. Comparison of different water pollution control methods in decreasing sediment load from peat mining areas. Boreal Env. Res. 2(2): 199–207.
Abstract
Pettersson, C., Rahm, L., Allard, B. & Borén, H. 1997. Photodegradation of aquatic humic substances: An important factor for the Baltic carbon cycle? Boreal Env. Res. 2(2): 209–215.
Abstract
Parmanne, R., Popov, A. & Raid, T. 1997. Fishery and biology of herring (Clupea harengus L.) in the Gulf of Finland: A review. Boreal Env. Res. 2(2): 217–227.
Abstract
Forsius, M., Johansson, M., Posch, M., Holmberg, M., Kämäri, J., Ahti Lepistö, A., Roos, J., Syri, S. & Starr, M. 1997. Modelling the effects of climate change, acidic deposition and forest harvesting on the biogeochemistry of a boreal forested catchment in Finland. Boreal Env. Res. 2(2): 129–143.
The relative importance of climate change, acidic deposition and forest harvesting/clearcutting on soil and streamwater chemistry of Rudbäcken, a small forested catchment in southern Finland, was evaluated by using a linked model system. The emphasis was on the assessment of long-term effects of different impact scenario combinations. The models were calibrated to measured values of soil and streamwater chemistry as well as forest biomass and growth increment. Deposition scenarios were based on atmospheric transport models. The effects of the three main driving forces (climate, deposition and forest harvesting) showed complex interactions, which were not always easy to interpret. Climate change (high change scenario), considerable emission reductions, and the clearcut scenario, were almost equally significant for parameters related to acidification effects. Considerable emission reductions resulted in either a slight improvement (streamwater pH) or steady-state (soil base saturation) compared with the current situation. The most negative response was predicted for the high climate change scenario, where high nitrogen immobilisation dependence on temperature was assumed. With the exception of the clearcut scenario, a clear increase in NO3 leaching in the long run was predicted for the site until the year 2050. Although the scenarios are hypothetical, they demonstrate the combined effects of elevated deposition inputs and climate change for the N leaching and accumulation processes.
Gottschalk, L. & Krasovskaia, I. 1997. Climate change and river runoff in Scandinavia, approaches and challenges. Boreal Env. Res. 2(2): 145–162.
Two main approaches dominate the studies of a possible temperature rise impact on river runoff: analyses of historical hydrological and climatological observation series and modelling of the river flow under an assumption of a predetermined temperature rise. The historical climatic and hydrological series provide a perfect tool to depict a variety of environmental situations, liable to correspond to a certain temperature change, i.e. produce synthetic climatic and hydrologic pictures on the realistic data available for the period with such climatic change. An application of this approach in Scandinavia has shown that already a small rise in the mean annual temperature of ~ 1°C, can cause notable changes in the river flow regime. Application of this approach is, however, often limited by the scarcity of long climatological and hydrological series, representing different environments. Another limitation is a poor knowledge about the influence of low frequency components (trends) of several decades or more, which might have a significant influence on the development of both climatological and hydrological series.The modelling approach can produce series of any desired length. However, the results of model studies heavily depend on the accuracy and relevance of the used model and climate scenarios. The modelling approach in the impact studies of climate change has two types of uncertainties. The first one concerns uncertainty in the climate model simulations, especially on a regional scale. Validation of the results of these models at present faces some serious obstacles, especially what concerns relevant hydrological “ground truth”. The second type concerns hydrological models used for forecasting of effects of climate change on river runoff. The paper offers a review of some important findings for a regionalized Scandinavian data set and discusses a number of essential problems and challenges connected to the studies of hydrological impacts of a possible climate change.
Zhang, Z., Wu, H. & Wang, Y. 1997. Variability of climatic and ice conditions in the Bohai Sea, China. Boreal Env. Res. 2(2): 163–169.
The Bohai Sea is a shallow and seasonally ice-covered sea. The annual maximum ice extent has exhibited a large variability during the past observation years. Ice and mean wintertime air temperature data have been collected in the present work, and a preliminary analysis is made of interannual changes of local mean air temperature and ice conditions. The mean wintertime air temperature has increased by 1.0°C and 1.4°C in the recent 10 (1986–95) and 5 years (1991–95), respectively, compared with the mean value of the past 40 years (1956–95). The latest 5 years have been exceptionally mild in the Bohai Sea, and the ice conditions also show an evident retrogradation. In addition, a preliminary discussion on the long-term fluctuation tendencies of the local mean air temperature and ice conditions is made.
Frycklund, C. & Jacks, G. 1997. Iron and artificial recharge of groundwater. Boreal Env. Res. 2(2): 171–181.
High iron concentrations may be a problem when groundwater is used for drinking water supply. The objective of this field study has been to clarify the factors that control the presence of iron in the water phase at artificial groundwater recharge with pond infiltration. The iron concentration in water was monitored over a 7-month period at a site with pond infiltration. Water was sampled once a month from 10 to 115 cm depth in the filtersand of the pond, and analyzed for iron. The filtersand was sampled before and after the water sampling period so that accumulation of iron could be quantified. It was found that at the 20 cm level in the filtersand the iron concentration was reduced to a level fully acceptable in drinking water. The analysis of the soil showed that 86% of the accumulated iron was retained in the top 5 cm of the filtersand. According to a budget considering the amount of iron coming to the filtersand and the amount leaving it, 138 g m– 2 should have been retained during 15 months while 145 g m– 2 was actually found by analysis. The findings show that the iron retention process was fast, both in time and travel distance. The iron retention efficiency would thus not be improved by a longer residence time. This suggests that even smaller geologic formations may be used for pond infiltration. The results also indicate that the iron retention was a largely abiotic process. The problem with gradually increasing iron concentrations at induced recharge is discussed in view of studies of iron-reducing microorganisms.
Itkonen, A. & Olander, H. 1997. The origin of the hypertrophic state of a shallow boreal shield lake. Boreal Env. Res. 2(2): 183–198.
The trophic development and external reasons for changes in the geochemical environment were evaluated for a period covering the last 200 years in the now hypertrophic Lake Köyliönjärvi, SW Finland. The geochemistry and chironomid remains indicate the activation of several interconnected mechanisms favoring phosphorus postdepositional mobility since the 1940s. The geochemical indicators include sedimentary biogenic silicon concentration, P fractions, Fe:P and Fe:Mn ratios, sulfides and CH4 convection, since 1961 also several water quality parameters. The most important external reasons for this development have probably been the lowering of the water level of the lake in 1938–40 and the following intensive use of P fertilizers on fields in the catchment area. The present great extent of summertime methane convection in the top sediments of Lake Köyliönjärvi highlights the importance of this P transfer mechanism. The results show that under favorable conditions the sedimentary geochemical record can be used to trace the past magnitude of P internal loading.
Kløve, B. 1997. Comparison of different water pollution control methods in decreasing sediment load from peat mining areas. Boreal Env. Res. 2(2): 199–207.
Different water treatment alternatives used to reduce sediment from peat mines were compared with a mathematical model. The simulation tested the benefit of different alternatives to reduce sediment tranport during a simulated storm. Traditional structures such as bed ditch pipe barriers, sedimentation ponds were compared against new alternatives such as artificial floodplains, and peak runoff control structures. The results of simulations show that detention of peak discharge is the most efficient way to reduce sediment transport. When runoff peaks are reduced traditional sedimentation ponds seem to have a smaller effect on sediment transport; increased settling is achieved by using shallow settling basins such as artificial floodplains.
Pettersson, C., Rahm, L., Allard, B. & Borén, H. 1997. Photodegradation of aquatic humic substances: An important factor for the Baltic carbon cycle? Boreal Env. Res. 2(2): 209–215.
Although humic substances (HS) are often considered as chemically stable and non-biodegradable in a marine environment, it is well known that exposure to light will lead to a decomposition of these substances. Laboratory experiments of photodegradation by UV-irradiation of aquatic humic substances and natural water resulted in a rapid and quantitative degradation. Seasonal variations in the humic fraction of the total organic carbon (TOC) was indicated in field studies in humic-rich water in Sweden. The HS/TOC-ratio was considerably higher during the dark part of the year than during the light season. Both the laboratory results and the field studies indicate the potential importance of photodegradation of HS and formation of CO2 for the global carbon cycle, though other mechanisms like microbial degradation are possible. Furthermore, the formation of biodegradable low-molecular weight organic acids from terrestrial humic substances may be essential for partly heterotrophic systems like the Bothnian Bay.
Parmanne, R., Popov, A. & Raid, T. 1997. Fishery and biology of herring (Clupea harengus L.) in the Gulf of Finland: A review. Boreal Env. Res. 2(2): 217–227.
The herring catch represents two-thirds of the entire fish catch in the Gulf of Finland. Herring reach maturity at a total length of 12–15 cm by the age of 2–3 years. Spawning takes place in May-June along most of the coast. Mass spawning begins when the water temperature is 8–9°C; eggs are usually attached to vegetation. Egg development takes 6–15 days. In recent years the growth of herring has been slow. In the catches, the oldest herring have been over 15 years. In the spring trap net catches, the most plentiful age group are the three-year-olds. In the autumn trawl catches, the most abundant age group is one-year-old herring. The stock is presently exploited around the F0.1 level. Assessing the state of the herring stock in the Gulf of Finland is complicated, because of the spawning and feeding migrations between the Gulf and the Baltic Sea proper.