(Table 1) Cation exchange capacity and other characteristics of soils common in Lower Saxony, Germany

The chemical and biochemical processes associated with the filtration of rainwater through soils, a step in groundwater recharge, were investigated. Under simulated climatic conditions in the laboratory, undisturbed soil columns of partly loamy sands, sandy soils and loess were run as lysimeters. A series of extraction procedures was carried out to determine solid matter in unaltered rock materials and in soil horizons. Drainage water and moisture movement in the columns were analysed and traced respectively. The behaviour of soluble humic substance was investigated by percolation and suspension experiments. The development of seepage-water in the unsaturated zone is closely associated with the soil genetic processes. Determining autonomous chemical and physical parameters are mineral composition and grain size distribution in the original unconsolidated host rock and prevailing climatic conditions. They influence biological activity and transport of solids, dissolved matter and gases in the unsaturated zone. Humic substances, either as amorphous solid matter or as soluble humic acids play a part in diverse sorption, solution and precipitation processes.

(Table 5) Experimental hydrodynamic parameters for different soil types obtained in the Lüchow-Dannenberg district, Lower Saxony

In three typical sandy soils of Northern Germany the mobility of radioactive fission products of technetium, iodine, ruthenium and zirconium have been investigated in dependence of the hydrodynamic and physico-chemical soil properties. The laboratory experiments, which simulated fall-out events, used soil columns (1 m length, 30 cm diameter) taken as undisturbed as possible. By measurements of the breakthrough curves in the percolate and of the depth distribution of radionuclides in the soil columns after 6 months the average transport velocity could be determined. These values could be compared with the average water velocity measured by 3H tagging. Three qualitative mobility relations were observed: Ranker: Tc > Ru > I > Zr; Podsol: Tc > Ru > I > Zr; Brown forest soil: Tc = Ru > I > Zr. Relations between some physico-chemical soil properties and the retardation of radionuclides due to adsorption could be observed (eg. retardation of iodine and technetium by organic substances). The average retardation factors of the radionuclides and the hydrodynamic soil parameters are used in a model which gives a quantitative assessment of the hazard of groundwater contamination by a fall-out event in areas covered with comparable soils.

Pollen analysis of a peat profile from the Rieseberger Moor, Lower Saxony, Germany

The Rieseberger Moor is a fen, 145 hectares in size, situated about 20 km east of Brunswick (Braunschweig), Lower Saxony, Germany. Peat was dug in the fen - with changing intensity - since the mid-18th century until around AD 1955. According to Schneekloth & Schneider (1971) the remaining peat (fen and wood peat) is predominantly 1.5 to 2 m thick (maximum 2.7 m). Part of the fen - now a nature reserve (NSG BR 005) - is wooded (Betula, Salix, Alnus). For more information on the Rieseberger Moor see http://de.wikipedia.org/wiki/Rieseberger_Moor. Willi Selle was the first to publish pollen diagrams from this site (Selle 1935, profiles Rieseberger Torfmoor I and II). This report deals with a 2.2 m long profile from the wooded south-eastern part of the fen consisting of strongly decomposed fen peat taken A.D. 1965 and studied by pollen analysis in the same year. The peat below 1.45 m contained silt and clay, samples 1.48 and 1.58 m even fine sand. These samples had to be treated with HF (hydrofluoric acid) in addition to the treatment with hot caustic potash solution. The coring ended in sandy material. The new pollen data reflect the early part of the known postglacial development of the vegetation of this area: the change from a birch dominated forest to a pine forest and the later spreading of Corylus and of the thermophilous deciduous tree genera Quercus, Ulmus, Tilia and Fraxinus followed by the expansion of Alnus. The new data are in agreement with Selle's results, except for Alnus, which in Selle's pollen diagram II shows high values (up to 42% of the arboreal pollen sum) even in samples deposited before Corylus and Quercus started to spread. On contrary the new pollen diagram shows that alder pollen - although present in all samples - is frequent in the three youngest pollen spectra only. A period with dominating Alnus as seen in the uppermost part of Selle's pollen diagrams is missing. The latter is most likely the result of peat cutting at the later coring site, whereas the early, unusually high alder values of Selle's pollen study are probably caused by contamination of the pollen samples with younger peat. Selle took peat samples usually with a "Torfbohrer" (= Hiller sampler). This side-filling type of sampler with an inner chamber and an outer loose jacket offers - if not handled with appropriate care - ample opportunities to contaminate older peat with carried off younger material. Pollen grains of Fagus (2 % of the arboreal pollen sum) were found in two samples only, namely in the uppermost samples of the new profile (0.18 m) and of Selle's profile I (0.25 m). If this pollen is autochthonous, with other words: if this surface-near peat was not disturbed by human activities, the Fagus pollen indicates an Early Subboreal age of this part of the profile. The accumulation of the Rieseberg peat started during the Preboreal. Increased values of Corylus, Quercus and Ulmus indicate that sample 0.78 m of the new profile is the oldest Boreal sample. The high Alnus values prove the Atlantic age of the younger peat. Whether Early Subboreal peat exists at the site is questionable, but evidently none of the three profiles reaches to Late Subboreal time, when Fagus spread in the region. Did peat-growth end during the Subboreal? Did younger peat exist, but got lost by peat cutting or has younger peat simply not yet been found in the Rieseberg fen? These questions cannot be answered with this study. The temporary decline of the curve of Pinus for the benefit of Betula during the Preboreal, unusual for this period, is contemporaneous with the deposition of sand (Rieseberger Moor II, 1.33 - 1,41 m; samples 1.48 and 1.58 m of the new profile) and must be considered a local phenomenon. Literature: Schneekloth, Heinrich & Schneider, Siegfried (1971). Die Moore in Niedersachsen. 2. Teil. Bereich des Blattes Braunschweig der Geologischen Karte der Bundesrepublik Deutschland (1:200000). - Schriften der wirtschaftswissenschaftlichen Gesellschaft zum Studium Niedersachsens e.V. Reihe A I., Band 96, Heft 2, 83 Seiten, Göttingen. Selle, Willi (1935) Das Torfmoor bei Rieseberg. - Jahresbericht des Vereins für Naturwissenschaft zu Braunschweig, 23, 46-58, Braunschweig.

(Table 1) Soil physical parameters of sediments obtained in the Lüchow-Dannenberg district, Lower Saxony

The mobility of the radionuclides of the elements Sr, I, Cs and Ce were investigated for three typical sands of Northern Germany under simulated natural, undersaturated flow conditions. The laboratory experiments include the determination of the flow parameters of the seepwater movement as well as the transport velocities of the radionuclides in the sands. For the three selected sands, the following mobility sequence/order has been established for the radionuclides: I < Sr < Cs < Ce

Geochemical and stable isotope composition of Middle Campanian marl-limestone rhythmites of the Lehrte West Syncline near Hannover (Lower Saxony, northern Germany)

A cyclic marl-limestone succession of Middle-Late Campanian age has been investigated with respect to a Milankovitch-controlled origin of geochemical data. In general, the major element geochemistry of the marl-limestone rhythmites can be explained by a simple two-component mixing model with the end-members calcium carbonate and 'average shale'-like material. Carbonate content varies from 55 to 90%. Non-carbonate components are clay minerals (illite, smectite) and biogenic silica from sponge spicules, as well as authigenically formed zeolites (strontian heulandite) and quartz. The redox potential suggests oxidizing conditions throughout the section. Trace element and stable isotopic data as well as SEM investigations show that the carbonate mud is mostly composed of low-magnesium calcitic tests of planktic coccolithophorids and calcareous dinoflagellate cysts (calcispheres). Diagenetic overprint results in a decrease of 2% d18O and an increase in Mn of up to 250 ppm. However, the sediment seems to preserve most of its high Sr content compared to the primary low-magnesium calcite of co-occurring belemnite rostra. The periodicity of geochemical cycles is dominated by 413 ka and weak signals between 51 and 22.5 ka, attributable to orbital forcing. Accumulation rates within these cycles vary between 40 and 50 m/Ma. The resulting cyclic sedimentary sequence is the product of (a) changes in primary production of low-magnesium calcitic biogenic material in surface waters within the long eccentricity and the precession, demonstrated by the CaCO3 content and the Mg/Al, Mn/Al and Sr/Al ratios, and (b) fluctuations in climate and continental weathering, which changed the quality of supplied clay minerals (the illite/smectite ratio), demonstrated by the K/Al ratio. High carbonate productivity correlates with smectite-favouring weathering (semi-arid conditions, conspicuously dry and moist seasonal changes in warmer climates). Ti as the proxy indicator for the detrital terrigenous influx, as well as Rb, Si, Zr and Na, shows only low frequency signals, indicating nearly constant rates of supply throughout the more or less pure pelagic carbonate deposition of the long-lasting third-order Middle-Upper Campanian sedimentary cycle.

Pollen and macroremains from sediment core Aschenhütte

The Upper Pleistocene sediments of the Aschenhütte sink-hole (west of Herzberg am Harz, Lower Saxony) enable one to make interesting correlations between palynological and geological results. The sequence is composed of limnic-telmatic deposits (Eemain to Lower Weichselian) and loess with paleosoils (Weichselian). Sedimentation started during the hornbeam-dominated phase of the Eemian interglacial period and continued throughout the Eemian, the Weichselian Brörup interstadial (sensu Andersen) and parts of the preceding and the following stadial phases, the Herning and the Rederstall stadials. As opposed to most of the known Eemian sites spruce was a major tree species during the hornbeam-dominated phase of the Eemian. The vegetational development during the interstadial phase does not show a period of climatic deterioration as is the case for the Brörup interstadial when considering regions with a more demanding vegetation or regions close to the natural boundaries of the tree species concerned. Pollen or seeds of Bruckenthalia and Picea omoricoides have not been found in the Aschenhütte cores. The limnic-telmatic sediments interlock with loess-paleosoils (Eemian soil and Lower Weichselian bleaching soils) at the lake shore. They are overlaid by loess paleosoils of the Stillfried-B interstadial (Hattorf soil and Lohne soil). Lake level fluctuations were determined by means of the facies distribution and isochrones as defined by pollen analysis. A relatively high stand of the lake level existed after the end of the Eemian interglacial and during the Brörup interstadial periods. In the course of the Herning stadial period the water level dropped, whereas during the Rederstall stadial phase the lake basin was covered by sediments and therefore dried up.

(Table 1) Planktonic foraminifer abundance and stable isotope ratios of a sediment core near Baddeckenstedt, north Germany

A refined sample processing technique using glacial acetic acid has been applied to Upper Cenomanian and Lower Turonian limestones from Baddeckenstedt (Lower Saxony) enabeling the first quantitative analysis of planktonic foraminiferal populations through the Stage boundary succession in northwestern Germany. Measurements of carbonate contents, organic carbon and stable carbon and oxygen isotopes were also reported. These data allow a correlation to be made of the Baddeckenstedt section with those at Misburg (basinal facies, northwestern Germany) and Dover (Plenus Marls, southern England). Significant maxima of the organic carbon content at Baddeckenstedt correspond to prominent black shale couplets at Misburg. The planktonic foraminiferal generic groups show at Baddeckenstedt similar fluctuations as reported from Dover. Their correlation reveals details of a complex paleoceanographic regime in the NW-German Basin during the Cenomanian/Turonian Oceanic Anoxic Event.

Tab. 4: Vergesellschaftung von Nitella opaca in Nordwestdeutschland

New facts on the occurrence and distribution of the threatened and rare stoneworts Chara baltica, C. connivens, C. contraria, C. virgata, Nitella hyalina, N. opaca, N. gracilis, N. capillaris, N translucens and N. flexilis and the non-threatened species Chara globularis in the northwestern part of Lower Saxony (Germany) are presented. A description of the stonewort sites is given and the abundance and the degrees of endangering of the species are discussed. Data about the Vegetation of the habitats of Nitella hyalina and N. opaca are reported. Additionally former sites of Chara canescens have been checked again. References to determination problems concerning Nitella opaca and N flexilis are given. Finally the protection of stoneworts, management requirements and the need for future investigations are discussed.

Pollen analysis from Fiekers Busch, Rinteln, Germany

Fiekers Busch is a wet alder wood close to Rinteln (southwest of Hannover/West Germany) existing there since about 6 000 or - at the most - 7 500 radiocarbon years. The sandy layers below the peaty sequence date from about 9 000 BP. The pollen diagram shows the basic trends of the postglacial vegetational development. Low pollen frequency and poor pollen preservation do , however, strongly restrict the possibilities to explain the peculiarities of the pollendiagram, especially the high pine and linden values.