Suo - Mires and peat vol. 32 no. 2 | 1981

This paper deals with the mineral exploration with the help of mire vegetation, its trophic level (geobotanic) and peat chemistry (biogeochemistry). The study area (Fig. 1) consists of 1. aeroelectrical anomaly zones (6970 ha), where the bedrock potentially contains limestone or skarnrocks with zinc ore, but is without outcrops and covered by peatlands and 2. some granite (1170 ha), quartz diorite (240 ha), gabbro (1210 ha) and amphibolite (270 ha) regions for comparison. The so called calcium influence of differed clearly from others having meso-through the peat. The anomaly region differed clearly from others having meso-and eutrophic mire types 37 % of the area. On amphibolite base there were 15 % and on gabbro base 12 % of rich mire types. Neither granite nor quartz diorite regions had mire types above mesotrophic level, the corresponding percentages being 9 and 4 (table 2). Some properties of peat were measured from 228 surface peat samples, (5—10 cm below the surface, from the first slightly humified peat layer) and from 236 borer samples through the peat horizon (106 points). The correlation analyses (Table 4) and t-tests (Table 3) certified that pH, conductivity, ash and Ca content of peat indicate the trophic level of a mire type and that the type is influenced by the bedrock. Plant species and mire types they form can thus reliably be used as measurement for the nutrient status of mire and peat. The distribution of Ni, Cu, Zn and Pb were studied. The vertical distribution of those heavy metals and Ca resembled more or less the letter c (fig. 2 and 3). The minimum contents were generally in the middle layers, about 150 cm from the bottom of mire, where the correlation (table 4) between the measured properties were also weakest. Ni contents in the surface peat were very significantly positively (+ + +) correlated to the trophic status of mire vegetation. Rich, mire-margin effected types got the greatest values. Ni was the only metal which had a very significant correlation with Ca in the surface and in the bottom layers. The correlation analyses did not show any meaningful relationships between Cu contents and other parameters except for the ash content in 50 cm layer from the bottom and other metals. The highest individual contents in the surface peat were analysed from the samples of meso- and eutrophic types with mire-margin effect. Zn distribution was the most irregular. It has significant correlation only with Cu and Pb. Zn content had sharp variations in peat profiles. The maximum contents were often in the surface peat of oligotrophic types. Pb had a very clear maximum value on the surface peat. In this material, which contains a great amount of samples from the area probably with skarn ore, Pb had a very significant correlation to ash and other heavy metals in the surface. The correlations declined and disappeared in intermediate layers but came out as significant with Ca, Cu and Zn at the bottom. In general the highest contents in surface were often analysed on mire-centre-effected types as with Zn, too. Classifying and mapping vegetation is a useful method before all when locating limestone and skarnrock deposits. It has to be remembered that mire types reflect the bedrock in accordance with the characteristic nutrient situation. The peat of mire-margin effected type might have importance being an accumulator and binder of nutrients and heavy metals coming from the nearest surroundings of the mire. The minerotrophic types with mire-centre effect reflect very locally the mineral soil and bedrock below the mire and are suitable for mineral exploration. When prospecting heavy metals on areas without outcrops of bedrock and covered with peatlands the peat chemical method can be used in connection with other methods like geophysical and -chemical ones. Also then it is relevant to take into account the information given by plants and vegetation units. The results published of the vertical distribution of heavy metals do not always agree and the pnenomenon has to be studied in more detail. One has to consider, also here, the effect of mire characteristic nutrient status (mire-margin and -centre effect). Investigating both vertical and horizontal distributions of heavy metals in peat of different mire types we get, as I understand, important information for mineral exploration. This information would also greatly help to plan a well serving peat sample collecting.

• Elomaa, Sähköposti: ei.tietoa@nn.oo

The effect of water content and degree of humification on dry density of peat has been shortly dealt with. Term dry density of peat is being used here to express the quantity of dry matter of peat held in a unit of volume of peat in situ. The material was collected from different parts of Finland both from virgin and drained mires (Fig. 1). Figures 3 and 7 are based on material collected from Eastern-Canadian raised bogs (Korpijaakko 1975). Sampling was conducted using a piston sampler designed for taking volumetric peat samples (Korpijaakko 1981). To determine water content and dry density peat samples were dried at 105 °C. Water content is given as per cent of fresh weight except for Canadian material as per cent of volume. Dry density is expressed as kg/m3 or g/cm3. Ash content of Sphagnum peat samples varies between 1 and 2 % and Carex peat between 3 and 4 %. It is not substracted from the weight. There is a clear positive correlation between the degree of humification and dry density of Sphagnum peat (comp. e.g. Päivänen 1969, Korpijaakko ja Radforth 1972, Tolonen ja Saarenmaa 1979, Mäkilä 1980). This is deliniated by a straight regression line for Finnish peats in Figure 2 and for Canadian peats in Figure 3. The slight difference on the course of the lines is due to the fact that Finnish samples come from the conditions that regularly prevail in Finnish mires where as part of Canadian samples are obtained from a exceptionally dry and consolidated deposite near a five meters high peat cliff in Point Escuminac, New Brunswick. For sedge peat there is no significant correlation between degree of humification and dry density (Fig. 4). This comes from the fact that sedge peat differently from Sphagnum peat is rather dence in its structure already in low degree of humification. Thus only minor changes of weight per volume takes place when humification advances. There is a strong negative correlation between water content and dry density of both Sphagnum and Carex peat. Within the limits of water content met in Finnish peatlands (80—95 %) the correlations can be depicted with straight regression lines (Figs. 5 and 6). When the water content of peat in situ gets still much lower than this, the regression lines will curve to the left closing to certain maximum values of dry density. As to Sphagnum peat there would be several curves representing different degrees of humification as is shown in Fig. 7. For Carex peat, because of the lack of correlation between the degree of humification and dry density, there will still be only one curve, that would follow at its wet end the data points shown in Fig. 6. The evaluation of the content of dry matter and further the energy content of a peat deposit can not be based on the knowing of peat types and degrees of humification alone. Dry density values of different kinds of peat in the deposit have to be determined. The most reliable results are obtained if the calculations are based on a sufficient quantity of volumetric samples. If they are not available the diagrams such as in Figures 5 and 6 could be utilized. The preassumption is that good enough peat samples are available for correct determination of water content on weight bases.

• Korpijaakko, Sähköposti: ei.tietoa@nn.oo
• Häikiö, Sähköposti: ei.tietoa@nn.oo
• Leino, Sähköposti: ei.tietoa@nn.oo

Turpeen pH:ta mitattaessa on huomioitava aika. Jos mittaamme pH:n liian nopeasti, saamme kalkitsemattomalle turpeelle liian korkean pH-arvon, kun taas kalkitulle turpeelle saamme liian alhaisen pH:n. Yleensä kalkitus stabiloittaa pH:n mittausta (kuva 1). Metalli-ionien määrityksissä tarvitaan suhteellisen vahvat happoliuokset. Vasta 1M happoliuokset liuottavat ja irroittavat turpeesta kationiset hivenravinteet riittävän tehokkaasti. Vasta näin vahvoilla hapoilla voidaan myös eliminoida turpeen erilaiset ominaisuudet kationisten hivenaineiden pidättäjänä. Edellä esitetyistä syistä ei esim. ammoniumasetaatti sovellu uuttoliuokseksi nyt kyseessä olevia ioneja määritettäessä. (Vertaa taulukko 3). Menetelmän hitainta työvaihetta (2—3 h) ei voida nopeuttaa sillä, että suodatuksesta otettaisiin vain osasuodos ennenkuin suodatettava on huolellisesti pesty. Totesimme, että osasuodoksista saadut metallimäärät olivat vain 25—70 % todellisista kokonaispitoisuuksista.

• Tummavuori, Sähköposti: ei.tietoa@nn.oo
• Kaikkonen, Sähköposti: ei.tietoa@nn.oo
• Pennanen, Sähköposti: ei.tietoa@nn.oo

The protection of peatland complexes has been the starting point of peatland conservation planning. This level of consideration has been completed by investigating the different characteristics of mires (vegetation types, flora, fauna etc.) as well as their ecological and regional variation. The present condition of the most threatened peatland types and flora has been surveyed in the last few years. A particular inventory has been undertaken e.g. in Kainuu, northern Finland, where the drainage has decreased the are of natural rich fens approximately to one tenth. The inventory of rich fens in Kainuu was started by examining the literature, flora register and bedrock maps with explanations. The natural state of the areas was judged by using aerial photographs, and many sites were excluded from further studies as they were already drained. In the field work main attention was paid to each mire complex, mire types, meso-eutrophic and eutrophic flora, landscape and natural state. The ranking of rich fens was performed on the basis of the following criteria: quantity and variety of types and subtypes, number of meso-eutrophic and eutrophic plant species, species under threat, natural state of peatland complexes, stage of drainage and importance of regional situation of rich fens. At the moment only two of the rich fens in Kainuu are under protection, but in the basic peatland conservation programme there are seven new sites included. A supplementary plan of the basic programme contains 20 further rich fens, which are very remarkable according to this ranking system (Table 1). Therefore, the rich fen inventory in Kainuu has proved to be necessary.

• Kaakinen, Sähköposti: ei.tietoa@nn.oo
• Kukko-oja, Sähköposti: ei.tietoa@nn.oo