Mikrosondenuntersuchungen an unterschiedlich stark mit Schwermetallen belasteten Böden. 2. Gehalte an Schwermetallen und anderen Elementen in Huminstoffaggregationen,Streustoffen und Holzkohlepartikeln

Electron microprobe studies on soil samples with varying heavy metal contamination. 2. Contents of heavy metals and other elements in aggregations of humic substances, litter residues and charcoal particles EMA point analysis show that the organic matter constituents of heavy metal contaminated soils are highly enriched with heavy metals. The maximal trace element accumulation were for Cu up to 13,000 mg/kg, for Zn up to 48,000 mg/kg, for Cd up to 2,100 mg/kg and for Pb up to 193,000 mg/kg. The affinity for the accumulation of the different heavy metals in aggregations of humic substances can be described by the sequence Cu > Pb ? Cd > Zn ? Ni > Co. In very strongly acidified humic top soil horizons the Pb and Cd accumulation in the organic matter constituents is in competition with the accumulation in Fe and Mn oxides. The heavy metal contents (especially of Cu) of the organic matter are often correlated with the content of organically bound calcium. The EMA results also show that high heavy metal amounts occur in combination with Ca-accumulations in the epidermis and the outer bark parenchym of decayed roots. EMA point analysis of the interior of fungus sclerotias show that sclerotias can contain high amounts of heavy metals, in particular lead (up to 49,700 mg Pb/kg). From statistical results of EMA point analysis follows that lead and other heavy metals attached to humic substances are not only bound as metal organic complexes but also as organic metal phosphate complexes. Also charcoal particles of polluted soils contain high amounts of heay metals. The accumulation affinity is quite similar to that of humic substances.     

Vertikaler Wasser- und Nitrattransport in tiefere Bodenschichten süddeutscher Ackerstandorte

Vertical water and nitrate movement into deeper soil layers on fields located in the south of Germany In Southern Bavaria, selected fields from deep loess and sandy sediments were sampled to a depth of maximum 10 m every 4 months, in order to determine the basic processes of water and nitrate movement in the course of the year. The downward movement of water and nitrate followed the principle of piston flow only in the intermediate vadose zone of loess soils with a leaching distance amounting 0.8 m per year. On the other hand, an accelerated as well as a delayed transport was observed in the zone of evapotranspiration of loess soils and in the whole profile of sandy soils, not being in accordance with the simple simulation model FLOTRA based on the classic theories of transport (Darcy flow, convection-dispersion-equation). Preferential flow led to the leaching of nitrate from the top soil to the lower boundary of the evapotranspiration zone of loess soils in 2 m depth, in winter and spring. In sandy soils nitrate was leached to the groundwater table in 4–6 m depth after extensive rainfall.     

Antioxidant effectiveness of phenolic apple juice extracts and their gut fermentation products in the human colon carcinoma cell line caco-2

Apples represent a major dietary source of antioxidative polyphenols. Their metabolic conversion by the gut microflora might generate products that protect the intestine against oxidative damage. We studied the antioxidant effectiveness of supernatants of fermented apple juice extracts (F-AEs, 6 and 24 h fermentation) and of selected phenolic degradation products, identified by HPLC-DAD-ESI-MS. Cell free antioxidant capacity of unfermented apple juice extracts (AEs) was decreased after fermentation by 30-50%. In the human colon carcinoma cell line Caco-2, F-AEs (containing <0.5% of original AE-phenolics) decreased the reactive oxygen species (ROS) level more efficiently than the F-blank (fermented without AE) but were less effective than the respective AEs. Similarly, antioxidant effectiveness of individual degradation products was lower compared to respective AE constituents. Glutathione level was slightly increased and oxidative DNA damage slightly decreased by fermented AE03, rich in quercetin glycosides. In conclusion, F-AEs/degradation products exhibit antioxidant activity in colon cells but to a lesser extent than the respective unfermented AEs/constituents.     

Extraction of mobile element fractions in forest soils using ammonium nitrate and ammonium chloride

The extraction of earth alkaline and alkali metals (Ca, Mg, K, Na), heavy metals (Mn, Fe, Cu, Zn, Cd, Pb) and Al by 1 M NH₄NO₃ and 0.5 M NH₄Cl was compared for soil samples (texture: silt loam, clay loam) with a wide range of pH(CaCl₂) and organic carbon (OC) from a forest area in W Germany. For each of these elements, close and highly significant correlations could be observed between the results from both methods in organic and mineral soil horizons. The contents of the base cations were almost convertible one‐to‐one. However, for all heavy metals NH₄Cl extracted clearly larger amounts, which was mainly due to their tendency to form soluble chloro complexes with chloride ions from the NH₄Cl solution. This tendency is very distinct in the case of Cd, Pb, and Fe, but also influences the results of Mn and Zn. In the case of Cd and Mn, and to a lower degree also in the case of Pb, Fe, and Zn, the effect of the chloro complexes shows a significant pH dependency. Especially for Cd, but also for Pb, Fe, Mn, Zn, the agreement between both methods increased, when pH(CaCl₂) values and/or contents of OC were taken into account. In comparison to NH₄Cl, NH₄NO₃ proved to be chemically less reactive and, thus, more suitable for the extraction of comparable fractions of mobile heavy metals. Since both methods lead to similar and closely correlated results with regard to base cations and Al, the use of NH₄NO₃ is also recommended for the extraction of mobile/exchangeable alkali, earth alkaline, and Al ions in soils and for the estimation of their contribution to the effective cation‐exchange capacity (CEC). Consequently, we suggest to determine the mobile/exchangeable fraction of all elements using the NH₄NO₃ method. However, the applicability of the NH₄NO₃ method to other soils still needs to be investigated.     

Repeated drying–rewetting cycles and their effects on the emission of CO2, N2O,NO, and CH4 in a forest soil

Prolonged summer droughts due to climate change are expected for this century, but little is known about the effects of drying and wetting on biogenic trace‐gas fluxes of forest soils. Here, the response of CO₂, N₂O, NO, and CH₄ fluxes from temperate forest soils towards drying–wetting events has been investigated, using undisturbed soil columns from a Norway spruce forest in the “Fichtelgebirge”, Germany. Two different types of soil columns have been used for this study to quantify the contribution of organic and mineral horizons to the total fluxes: (1) organic horizons (O) and (2) organic and mineral soil horizons (O+M). Three drying–wetting treatments with different rewetting intensities (8, 20, and 50 mm of irrigation d^–1) have been compared to a constantly moist control to estimate the influence of rainfall intensity under identical drying conditions and constant temperature (+15°C). Drought significantly reduced CO₂, N₂O, and NO fluxes in most cycles. Following rewetting, CO₂ fluxes quickly recovered back to control level in the O columns but remained significantly reduced in the O+M columns with total CO₂ fluxes from the drying–wetting treatment ranging approx. 80% of control fluxes. Fluxes of N₂O and NO remained significantly reduced in both O and O+M columns even after rewetting, with cumulative fluxes from drying–wetting treatments ranging between 20% and 90% of the control fluxes, depending on gas and cycle. Fluxes of CH₄ were small in all treatments and seem to play no significant role in this soil. No evidence for the release of additional gas fluxes due to drying–wetting was found. The intensity of rewetting had no significant effect on the CO₂, N₂O, NO, and CH₄ fluxes, suggesting that the length of the drought period is more important for the emission of these gases. We can therefore not confirm earlier findings that fluxes of CO₂, N₂O, and NO during wetting of dry soil exceed the fluxes of constantly moist soil.