RESUMEN
Seasonal variations in foliar ¹³7Cs levels were examined in Norway spruce (Picea abies (L.) Karst.), and Scots pine (Pinus sylvestris L.) in western Finland. Our aim was to test the occurrence of seasonal variation in contents and concentrations of ¹³7Cs, potassium and carbon in needles. The study focused on analysing levels of total ¹³7Cs in the three youngest needle age classes and comparing them to the levels of potassium and carbon. Spruce and pine needles were collected from 50- and 65-year-old stands on 18 sampling occasions between April 1996 and February 1997. Phases of intensive growth, needle elongation and dormancy were apparent in the time series for the needle contents and activity concentration of ¹³7Cs, both of which varied according to needle age class and tree species. The sequence of phases with a temporal fluctuation of needle contents, activity concentrations of ¹³7Cs and concentrations of K and carbon varied occasionally, and the efficiency of their translocation revealed some differences in the dynamics of ¹³7Cs, K and carbon in spruce and pine. The data clearly showed that the needles' K contents responded strongly to changes in K demand from other parts of the tree due to seasonal changes and that these responses were stronger than the associated retranslocations of ¹³7Cs, particularly in Scots pine. During intensive growth, K was less mobile than ¹³7Cs in the needles. The uptake of ¹³7Cs by current-year needles is simultaneously affected by uptake from the soil via the roots and retranslocation from other internal sources, and both of these processes affect the observed transfer rates during the growth period. Our results provided information on the transfer rates and revealed differentiation of root uptake and retranslocation of ¹³7Cs in needles. The study can support dynamic modelling of atmospheric ¹³7Cs contamination in forests.
Asunto(s)
Carbono/metabolismo , Cesio/metabolismo , Exposición a Riesgos Ambientales , Picea/metabolismo , Pinus/metabolismo , Potasio/metabolismo , Contaminantes Radiactivos/metabolismo , Factores de Edad , Radioisótopos de Cesio/metabolismo , Monitoreo del Ambiente , Finlandia , Picea/efectos de la radiación , Pinus/efectos de la radiación , Hojas de la Planta/metabolismo , Hojas de la Planta/efectos de la radiación , Estaciones del Año , Espectrometría gamma , Espectrofotometría AtómicaRESUMEN
Increasing use of wood fuels for energy production in Finland since the 1990s implies that large quantities of the generated ashes will be available for forest fertilization. The aim of this study was to analyse the effect of wood ash application on ¹³7Cs activity concentrations in Scots pine (Pinus sylvestris L.) needles and certain berries and mushrooms on drained peatlands. The study was based on field experiments carried out on two mires in Finland in 1997-1998. Two different types of wood ash were applied at dosages of 3500, 3700, 10 500 and 11 100 kg ha⻹. Wood ash did not increase ¹³7Cs activity concentration in plants in the second growing season following application. On the contrary, a decrease in ¹³7Cs activity concentration was seen in the plants of the ecosystem on drained peatlands. This result is of importance, for instance, when recycling of ash is being planned.
Asunto(s)
Radioisótopos de Cesio/metabolismo , Monitoreo del Ambiente , Fertilizantes , Plantas/metabolismo , Árboles , Madera , Agaricales/crecimiento & desarrollo , Agaricales/metabolismo , Ecosistema , Finlandia , Frutas/crecimiento & desarrollo , Frutas/metabolismo , Pinus sylvestris/crecimiento & desarrollo , Pinus sylvestris/metabolismo , Desarrollo de la Planta , Hojas de la Planta/crecimiento & desarrollo , Hojas de la Planta/metabolismo , Reciclaje/métodos , Estaciones del AñoRESUMEN
Compared to agricultural lands, forests are complex ecosystems as they can involve diverse plant species associations, several vegetative strata (overstorey, shrubs, herbaceous and other annual plant layer) and multi-layered soil profiles (forest floor, hemi-organic and mineral layers). A high degree of variability is thus generally observed in radionuclide transfers and redistribution patterns in contaminated forests. In the long term, the soil compartment represents the major reservoir of radionuclides which can give rise to long-term plant and hence food contamination. For practical reasons, the contamination of various specific forest products has commonly been quantified using the aggregated transfer factor (T(ag) in m(2)kg(-1)) which integrates various environmental parameters including soil and plant type, root distribution as well as nature and vertical distribution of the deposits. Long lasting availability of some radionuclides was shown to be the source of much higher transfer in forest ecosystems than in agricultural lands. This study aimed at reviewing the most relevant quantitative information on radionuclide transfers to forest biota including trees, understorey vegetation, mushrooms, berries and game animals. For both radiocaesium and radiostrontium in trees, the order of magnitude of mean T(ag) values was 10(-3)m(2)kg(-1) (dry weight). Tree foliage was usually 2-12 times more contaminated than trunk wood. Maximum contamination of tree components with radiocaesium was associated with (semi-)hydromorphic areas with thick humus layers. The transfer of radionuclides to mushrooms and berries is high, in comparison with foodstuffs grown in agricultural systems. Concerning caesium uptake by mushrooms, the transfer is characterized by a very large variability of T(ag), from 10(-3) to 10(1)m(2)kg(-1) (dry weight). For berries, typical values are around 0.01-0.1 m(2)kg(-1) (dry weight). Transfer of radioactive caesium to game animals and reindeer and the rate of activity reduction, quantified as an ecological half-life, reflect the soil and pasture conditions at individual locations. Forests in temperate and boreal regions differ with respect to soil type and vegetation, and a faster decline of muscle activity concentrations in deer occurs in the temperate zone. However, in wild boar the caesium activity concentration shows no decline because of its special feeding habits. In the late phase, i.e. at least a few months since the external radionuclide contamination on feed plants has been removed, a T(ag) value of 0.01 m(2)kg(-1) (fresh weight) is common for (137)Cs in the muscles of adult moose and terrestrial birds living in boreal forests, and 0.03 m(2)kg(-1) (fresh weight) for arctic hare. Radiocaesium concentrations in reindeer muscle in winter may exceed the summer content by a factor of more than two, the mean T(ag) values for winter ranging from 0.02 to 0.8 m(2)kg(-1) (fresh weight), and in summer from 0.04 to 0.4m(2)kg(-1). The highest values are found in the year of initial contamination, followed by a gradual reduction. In waterfowl a relatively fast decline in uptake of (137)Cs has been found, with T(ag) values changing from 0.01 to 0.002 m(2)kg(-1) (fresh weight) in the three years after the contaminating event, the rate being determined by the dynamics of (137)Cs in aquatic ecosystems.
Asunto(s)
Ecosistema , Contaminantes Radiactivos del Suelo/metabolismo , Árboles/metabolismo , Agaricales/metabolismo , Animales , Radioisótopos de Cesio/análisis , Radioisótopos de Cesio/metabolismo , Frutas/metabolismo , Contaminantes Radiactivos del Suelo/análisisRESUMEN
The paper summarizes an evaluation of practicability of rural countermeasures after radioactive fallout in northern conditions carried out by a Finnish group of experts in the FARMING Network project. Snow and soil frost limit the selection of crops, and the short growing season allows mostly one harvest yearly. Cold climate restricts fruit production to apples and berries. Due to the long indoor feeding period, conserved and stored clean feed is available almost all year round. The use of fertilisers and lime on poor and acidic soils leads to high potassium and calcium intake of cows increasing the incidence of milk fever. The surface soil layer is thin and ploughing deeper than 20 cm is problematic due to stony and compacted soils. It also increases soil acidity and decreases fertility. Cultivation of peatlands limits the selection of plants and increases long-term radiocaesium contamination of crops. Frost and snow delay ploughing and spreading of waste milk on arable land, but removal of snow is a decontamination option. Long distances and high transport costs complicate carrying out the countermeasures. The Finnish stakeholder group considered it vital to be prepared for implementation of practicable measures for the safety of food.