Ralph Meissner

Temporal dynamics of pore water concentrations of Cd, Co, Cu, Ni, and Zn and their controlling factors in a contaminated floodplain soil assessed by undisturbed groundwater lysimeters

We aimed to assess the dynamics of pore water concentrations of Cd, Co, Cu, Ni, Zn and their controlling factors (EH, pH, DOC, Fe, Mn, and SO4(2-)) in a contaminated floodplain soil under different flood-dry-cycles. Two parallel undisturbed groundwater lysimeters (mean values presented) were used for long term (LT; 94 days) and short term (ST; 21 days) flood-dry-cycles. Reducing conditions under LT lead to low EH and pH, while DOC, Co, Fe, Mn, and Ni increased. Cadmium, Cu, Zn, and SO4(2-) increased under oxidizing conditions during ST. Cobalt and Ni revealed a similar behavior which seem to governed by EH/pH, Mn, Fe, and DOC. Cadmium, Cu, and Zn reveal a similar fate; their dynamics were affected by EH/pH, DOC, and SO4(2-). Our findings suggest that a release of Cd, Cu, Co, Fe, Mn, Ni, and Zn under different flood-dry-cycles can assumed what might create potential environmental risks in using metal-enriched floodplain soils.

Associated bacteria increase the phytoextraction of cadmium and zinc from a metal-contaminated soil by mycorrhizal willows.

In order to enhance phytoremediation efficiency, we investigated the effects of dual inoculation with ectomycorrhizal fungi and the ectomycorrhiza associated bacteria Micrococcus luteus and Sphingomonas sp. on the growth and metal accumulation of willows (Salix viminalis x caprea) on contaminated soil. The bacterial strains were previously collected from sporocarps of ectomycorrhizal fungi. The bacteria increased plant growth and the mycorrhizal dependency of willows colonized with the ectomycorrhizal fungus Hebeloma crustuliniforme. The total cadmium (Cd) and zinc (Zn) accumulation in the shoot biomass was increased after inoculation with the fungal strain Hebeloma crustuliniforme in combination with Micrococcus luteus up to 53% and in combination with Sphingomonas sp. up to 62%, respectively. The dual inoculation in combination with Laccaria laccata did not increase the accumulation of Cd and Zn in the willows. We conclude that associated bacteria can enhance the ectomyorrhiza formation and growth of willows and, thereby, the Cd and Zn accumulation in the plant biomass. The results suggest that bacterial support of root growth promoting ectomycorrhizal fungi may be a promising approach to improve the remediation of metal-contaminated soils by using willows.

Sequentially extracted phosphorus fractions in peat‐derived soils

Phosphorus (P) forms were sequentially extracted from peat derived soils (Eutric Histosols and Gleysols) at eight sites in Saxony-Anhalt (Germany) to disclose general differences in P pools between mineral and organic soils and to investigate effects of peat humification and oxidation in conjunction with land use and soil management on the P status of soils. Overall 29 samples providing a wide variety of basic chemical properties were subjected to the Hedley fractionation. The Histosol topsoils contained more total P (P t ) (1345 ± 666 mg kg -1 ) than the Gleysol topsoils (648 ± 237 mg kg -1 ). The predominant extractable fractions were H 2 SO 4 -P (36-63 % of P t ) in calcareous and NaOH-P o (0-46 % of P t ) in non-calcareous Histosols. These soils had large pools of residual P (13-93 % of P t ). Larger contents and proportions of P o and of labile P fractions generally distinguished organic from mineral soils. Regression analyses indicated that poorly crystalline pedogenic oxides and organic matter were binding partners for extractable and non-extractable P. Intensive management that promotes peat humification and oxidation results in disproportional enrichments of labile P fractions (resin-P, NaHCO 3 -P i , and NaHCO 3 -P o ). These changes in P chemistry must be considered for a sustainable management of landscapes with Histosols and associated peat derived soils.

Spatial distribution of arsenic and heavy metals in willow roots from a contaminated floodplain soil measured by X-ray fluorescence spectroscopy

Under changing redox conditions some plants create plaques at their root surface, which may affect the mobility and uptake of As and heavy metals but it is unknown to what extent this also holds true for willows in contaminated floodplain soils. Therefore, willow roots were sampled from a phytoremediation trial in the contaminated floodplain of the river Elbe (Germany), cryofixed, freeze-dried, and cross sections were mapped for the distribution of As, Ca, Cu, Fe, K, Mn, Ni, S and Zn by synchrotron based X-ray fluorescence spectroscopy. The elements Ca, Cu, Ni, S and Zn were concentrated in the aerenchymatic tissue, and not associated with Fe and Mn. Mixed Fe-Mn plaques covered the surface of the willow roots and As was accumulated in these plaques. The observed association pattern between As and Fe was explained by the different sorption/desorption properties of As(III) and As(V). The Cu and Zn intensities were not associated with the intensity of Fe in the plaque, which seems to be a willow-specific difference compared to other wetland plants. These results suggested that willows are especially suited to stabilize low-phytoextractable elements like Cu and As in their roots and rhizosphere. Thus, short rotation coppicing of willows may be a practical approach to mitigate the adverse effects of floodplain soil contamination.

Lysimeter studies in East Germany concerning the influence of set aside of intensively farmed land on the seepage water quality

Abstract Since 1990, the five new federal states of Germany have experienced a fundamental structural change in agriculture. As much as 10% of the 6.2 million hectares of the previously intensively farmed agricultural areas were abruptly set aside. In the spring of 1991, a lysimeter test, designed in 1983 to maximize yields, was adapted to these new agricultural conditions. The purpose of the test was to investigate the impact of the structural changes on water balance and budget of materials. Leaching of relevant cations (Ca 2+ , Mg 2+ , Na + , and K + ) and anions (total PO 4 3− , NO 3 − , Cl − , and SO 4 2− ) contained in the seepage water as well as the resulting pH-values were determined for various types of set aside. The reference treatment consisted of intensively farmed lysimeters following the principles of BMP (best management practices). The tests covered a period of three years. The studies proved that restricting agricultural usage on areas previously farmed heavily, by converting them into permanent or rotation fallow, will result in measurable changes of seepage water recharge and quality within less than one year. The permanent fallow showed large leaching losses of the measured cations even three years after set aside. In contrast, the leaching of the measured anions NO 3 − , SO 4 2− and Cl − decreased significantly compared with the initial level. If cation leaching decreases from lack of additional supply, a shift of the pH into the acid range is to be expected. A one year set aside in the form of a rotation fallow is connected with increased leaching of nitrate. Compared with intensively farmed agricultural land, nitrate leaching in the year of set aside is increased by approximately 55% and in the year of resuming intensive agricultural production by 30%.

Gebietsabflüsse aus Agrarlandschaften Nordost‐ und Mitteldeutschlands

Fur ein groseres Gebiet im Lockergesteinsbereich Nordost‐ und Mitteldeutschlands wurden verschiedene Verfahren zur Abschatzung des mittleren Gebietsabflusses gepruft und mit gemessenen Abflussen verglichen. Die Ansatze von Renger und Strebel (1980) sowie Bagrov, mod. von Glugla (1985) berucksichtigen die Einflusse von Boden und Landnutzung auf den Gebietsabflus und zeigen gute Ubereinstimmung mit Meswerten fur Einzugsgebiete > 100 km2. Der Gebietsniederschlag ist die dominierende Bilanzgrose. Aufgrund Niederschlagsmangels kommt es im uberwiegenden Teil des Beispielsgebietes in etwa 20% der Jahre zu extremer Verminderung und unter Nadelwald bereits zum Erliegen der Abflusbildung. Setzt man fur die erste Halfte des nachsten Jahrhunderts eine Erhohung der Temperatur um 1,5 K, eine Zunahme der Winterniederschlage um 6% und eine Abnahme der Sommerniederschlage um 2% an (mittlerer Erwartungswert auf der Grundlage von Prognosen von Kenny et al. 1993), so sind nur sehr geringe Anderungen des mittleren Abflusses z...

Differences in DOM of rewetted and natural peatlands – Results from high-field FT-ICR-MS and bulk optical parameters

Peatlands can be a potential source of dissolved organic matter (DOM) in fresh water catchment areas. The quantity and quality of DOM can differ between pristine, degraded and rewetted peatlands. Due to the large scale and continuing losses of peatlands, their conservation and restoration has been increasingly emphasized. Mostly rewetting measures are required to improve the hydrology of damaged peatlands, which is a precondition for the resettlement of peat-forming plant species. Thus, in term of DOM, there is a special need to understand how rewetting measures affect DOM characteristics and concentrations. To estimate the potential leaching of humic substances from rewetted areas two natural sites were compared with four artificially rewetted sites in a peatland area of the Harz Mountains National Park, Germany. This was done with regards to DOM quality by combining the results from Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS, measured at one time in Spring) and excitation-emission-matrix fluorescence spectroscopy (EEMF, measured monthly for the period of one year). The DOM quality was significantly less variable in the pristine peatland soil water compared to the rewetted peatland soil waters, from both a spatial and a seasonal perspective. The soil water from the rewetted peatland sites showed a higher degree of humification compared to pristine peatland. DOC concentration was mostly consistent in the pristine peatland over the year. The rewetted peatlands showed higher DOC levels in Summer months and lower DOC in Winter months compared to the pristine peatland. It can be concluded that the rewetting of peatlands is coupled with high concentrations of DOC in soil water and its quality is highly aromatic (as reflected by the observed values from the humification index) during times with elevated temperature. The results may have a significant input for dynamic catchment area studies with regards to rewetting peatland sites.

Release of nitrous oxide and dinitrogen from a transition bog under drained and rewetted conditions due to denitrification: results from a [15N]nitrate-bromide double-tracer study.

Denitrification is well known being the most important nitrate-consuming process in water-logged peat soils, whereby the intermediate compound nitrous oxide (N2O) and the end product dinitrogen (N2) are ultimately released. The present study was aimed at evaluating the release of these gases (due to denitrification) from a nutrient-poor transition bog ecosystem under drained and three differently rewetted conditions at the field scale using a 15N-tracer approach ([15N]nitrate application, 30 kg N ha−1) and a common closed-chamber technique. The drained site is characterized by a constant water table (WT) of –30 cm (here referred to as D30), while rewetted sites represent a constant WT of –15 cm, a constant WT of 0 cm (i.e. waterlogged), and an initial WT of 0 cm (which decreased slightly during the experiment), respectively, (here referred to as R15, R0, and R0d, respectively). The highest N2O emissions were observed at D30 (291 µg N2O–N m−2 h−1) as well as at R0d (665 µg N2O–N m−2 h−1). At the rewetted peat sites with a constant WT (i.e. R15 and R0), considerably lower N2O emissions were observed (maximal 37 µg N2O–N m−2 h−1). Concerning N2 only at the initially water-logged peat site R0d considerable release rates (up to 3110 µg N2–N m−2 h−1) were observed, while under drained conditions (D30) no N2 emission and under rewetted conditions with a constant WT (R15 and R0) significantly lower N2 release rates (maximal 668 µg N2–N m–2 h−1) could be detected. In addition, it has been found that natural WT fluctuations at rewetted peat sites, in particular a rapid drop down of the WT, can induce high emission rates for both N2O and N2.

Advanced Technologies in Lysimetry

The ability to quantify soil water flow is a prerequisite for the accurate prediction of solute transfer within the unsaturated zone. Monitoring these fluxes is a challenge because the results are required for answering not only scientific but also practical questions regarding the protection of groundwater, the sustainable management of agricultural, forestry, mining or set aside industrial areas, the reduction of leachate loss from landfills, and for explaining the fate of environmentally harmful substances. Both direct and indirect methods exist for estimating water flux rates; these have been applied with varying success. In Europe, the use of direct lysimetry methods for measuring water and solute fluxes in soils has increased significantly in recent years. Although this technique generates reliable drainage data, it involves relatively high investment and maintenance costs. New lysimeter techniques have been developed to tackle this problem. It is now possible to collect large monolithic soil columns and to measure the soil water balance of these monoliths (surface area 0.03–2 m2 and depth to 3 m) with a high degree of precision (±20 g). Furthermore, progress in lysimetry enables us to ascertain experimentally the mass input of dew and to calculate actual evapotranspiration, precipitation and seepage rates. Weighable groundwater lysimeters have been developed in addition to gravitation lysimeters. Different lysimeter types and their usage will be presented and explained using practical examples.

Analysis of the effect of meteorological factors on dewfall.

To get an insight into when dewfall will occur and how much to expect we carried out extensive calculations with the energy balance equation for a crop surface to 1) identify the meteorological factors which determine dewfall, 2) establish the relationship between dewfall and each of them, and 3) analyse how these relationships are influenced by changes in these factors. The meteorological factors which determine dewfall were found to be air temperature (T(a)), cloud cover (N), wind speed (u), soil heat flux (G), and relative humidity (h(r)). Net radiation is also a relevant factor. We did not consider it explicitly, but indirectly through the effect of temperature on the night-time radiation balance. The temperature of the surface (T(s)) where dew forms on is also important. However, it is not a meteorological factor, but determined by the aforementioned parameters. All other conditions being equal our study revealed that dewfall increases linearly with decreasing N or G, and with increasing h(r). The effect of T(a) and u on dewfall is non-linear: dewfall initially increases with increasing T(a) or u, and then decreases. All five meteorological factors can lead to variations in dewfall between 0 and 25 W m(-2) over the range of their values we studied. The magnitude of the variation due to one factor depends on the value of the others. Dewfall is highest at N=0, G=0, and h(r)=1. Ta at which dewfall is highest depends on u and vice versa. The change in dewfall for a unit change in N, G or h(r) is not affected by the value of N, G or h(r), but increases as T(a) or u increase. The change in dewfall for a unit change in Ta or u depends on the value of the other four meteorological factors.