Theoretical study of structural, mechanical and spectroscopic properties of boehmite (γ-AlOOH).

The structural, mechanical and spectroscopic properties of boehmite (AlOOH polymorph) were investigated by means of first-principle density functional theory (DFT) and semiempirical density functional based tight binding (DFTB) methods. Apart from a marginal underestimation of interlayer hydrogen bond distances the DFT method well reproduces the experimental equilibrium low-pressure structure. For the DFTB method similar good agreement was obtained for lattice parameters, however bond lengths and angles showed a larger deviation from experiment in comparison to DFT results. The experimental spectrum of the OH stretching region was interpreted by means of the calculated frequencies within the frame of the harmonic approximation and by calculating the power spectra of the hydroxyl groups obtained from molecular dynamics simulations. Using the latter approach, the strong coupling between the individual OH modes was demonstrated. Isostatic structural compression of the boehmite structure was performed in order to obtain the bulk modulus and the dependence of the vibrational spectrum on the pressure. The DFT method gives a value of 97 GPa in the athermal limit. Comparison with available bulk moduli for other AlOOH polymorphs reveals that boehmite shows the highest compression, for which mainly a strong shortening mechanism of interlayer hydrogen bonds is responsible. The DFT method also described correctly the dependence of the OH stretch frequencies upon compression resulting in a strong red shift. Although good performance is observed for the low-pressure region, the DFTB method is not found to be suitable for high-pressure studies in cases such as boehmite.

How do long-term development and periodical changes of river-floodplain systems affect the fate of contaminants? Results from European rivers.

In many densely populated areas, riverine floodplains have been strongly impacted and degraded by river channelization and flood protection dikes. Floodplains act as buffers for flood water and as filters for nutrients and pollutants carried with river water and sediment from upstream source areas. Based on results of the EU-funded "AquaTerra" project (2004-2009), we analyze changes in the dynamics of European river-floodplain systems over different temporal scales and assess their effects on contaminant behaviour and ecosystem functioning. We find that human-induced changes in the hydrologic regime of rivers have direct and severe consequences on nutrient cycling and contaminant retention in adjacent floodplains. We point out the complex interactions of contaminants with nutrient availability and other physico-chemical characteristics (pH, organic matter) in determining ecotoxicity and habitat quality, and draw conclusions for improved floodplain management.

Immobilising of Cd, Pb, and Zn contaminated arable soils close to a former Pb/Zn smelter: a field study in Austria over 5 years.

Numerous smelter sites are surrounded by rural land. The entrance of non-essential metals such as lead or cadmium into the food chain is very likely as well as phytotoxicity effects of zinc. Finding a realistic solution for these large-scale contaminations was one aim of this study. Previous results from pot experiments showed a high potential for the reduction of metals entering the food chain via crops grown on smelter-contaminated soils from Arnoldstein, Austria, by the use of amendments for immobilisation. A further aim was to optimise a field experiment for overcoming the gap between pot and field experiments and to look for long-term efficiency of the treatments [lime (CA), red mud (RM), gravel sludge + red mud (GS + RM)]. Field experiment results were obtained for 5 years. Besides soil and soil pore water samples, the following harvests were yielded: spring barley (Hordeum distichon ssp. L.) (2004-2005), narrowleaf plantain (Plantago lanceolata L.) (2006-2007) and velvet grass (Holcus lanatus L.) (2007-2008). The long-term efficiency of GS + RM led us to conclude that their application seems to be a realistic and practical measure for extensively contaminated land, best in combination with metal excluding cultivars.

Distribution of cadmium among geochemical fractions in floodplain soils of progressing development.

Initial soil development in river floodplains influences soil properties and processes. In this study, suites of young floodplain soils sampled at three European rivers (Danube/Austria, Ebro/Spain and Elbe/Germany) were used to link soil development to the soils' retention capacity for cadmium. Geochemical fractionation of original and metal-spiked soils was conducted. Cadmium remained in weakly bound fractions in both original and spiked soils, representing an entirely different behaviour than observed for copper in an earlier study. The tendency of incorporation into more stable forms over time was only slightly expressed. Correlation analysis revealed the involvement of different sorption surfaces in soil, with no single soil constituent determining cadmium retention behaviour. Nevertheless, in the calcareous soils of the Danube floodplain, we found increased cadmium retention and decreased portions of desorbable cadmium with progressing soil development.

Geochemical fractions of copper in soil chronosequences of selected European floodplains.

The influence of soil formation on copper sorption is documented based on chronosequences of soils from three river floodplains in Europe (Danube, Ebro and Elbe). Sequential extraction was used to fractionate copper in original and spiked soils in order to study the long-term and short-term behaviour of copper retention. Copper partitioning among defined geochemical fractions was mainly determined by soil pH and the contents of carbonates, organic matter and Fe-/Mn-oxides and hydroxides. Copper extracted with NH(2)OH.HCl correlated well with the contents of crystalline Fe-oxides and hydroxides, demonstrating increasing retention capacity with progressing soil development. Copper retained in original soils was found in more strongly bound fractions, whereas sorption of freshly added copper was primarily influenced by the presence of carbonates. Beyond the effect of progressing soil formation, variations in organic carbon contents due to different land use history affected the copper retention capacity of the investigated soils.

The integrated project AquaTerra of the EU sixth framework lays foundations for better understanding of river-sediment-soil-groundwater systems.

The integrated project "AquaTerra" with the full title "integrated modeling of the river-sediment-soil-groundwater system; advanced tools for the management of catchment areas and river basins in the context of global change" is among the first environmental projects within the sixth Framework Program of the European Union. Commencing in June 2004, it brought together a multidisciplinary team of 45 partner organizations from 12 EU countries, Romania, Switzerland, Serbia and Montenegro. AquaTerra is an ambitious project with the primary objective of laying the foundations for a better understanding of the behavior of environmental pollutants and their fluxes in the soil-sediment-water system with respect to climate and land use changes. The project performs research as well as modeling on river-sediment-soil-groundwater systems through quantification of deposition, sorption and turnover rates and the development of numerical models to reveal fluxes and trends in soil and sediment functioning. Scales ranging from the laboratory to river basins are addressed with the potential to provide improved river basin management, enhanced soil and groundwater monitoring as well as the early identification and forecasting of impacts on water quantity and quality. Study areas are the catchments of the Ebro, Meuse, Elbe and Danube Rivers and the Brévilles Spring. Here we outline the general structure of the project and the activities conducted within eleven existing sub-projects of AquaTerra.

Treatment of landfill leachate by irrigation and interaction with landfill gas.

The treatment efficiency of landfill leachate irrigation and the effect of landfill gas addition were investigated in a vegetated compost/gravel substrate by monitoring soil moisture content, drainage water volume and quality in a two years lysimeter experiment. Landfill leachate irrigation exceeding 350 mm increased soil moisture and drainage volumes owing to the deterioration of the vegetation resulting from high sodium chloride inputs. Even so sodium chloride was lost in between the irrigation periods, the total reduction of the landfill leachate volume by irrigation decreased from 71% in the first year to 38% in the second year. Landfill gas addition also increased drainage volumes, but was less pronounced. Twenty-two percent of magnesium was retained under landfill leachate irrigation, while decreasing pH values, redox potential and high initial concentrations in the substrate released calcium, iron and potassium. Ninety-eight percent of ammonium was removed by irrigation, but 44% of the applied ammonium was leached as nitrate after oxidation took place due to a decreased uptake after the vegetation deteriorated. Landfill gas fumigation influenced landfill leachate treatment by decreasing the redox potential and the pH and increasing the drainage water content, which improved the retention of total nitrogen and sulfate, but increased the release of iron, calcium and magnesium. To conclude, landfill leachate irrigation is a valuable treatment option to minimize leachate quantities and remove ammonium independent from the presence of landfill gas if salt accumulation is avoided.

Remediation of contaminated agricultural soils near a former Pb/Zn smelter in Austria: batch, pot and field experiments.

Metal contaminated crops from contaminated soils are possible hazards for the food chain. The aim of this study was to find practical and cost-effective measures to reduce metal uptake in crops grown on metal contaminated soils near a former metal smelter in Austria. Metal-inefficient cultivars of crop plants commonly grown in the area were investigated in combination with in-situ soil amendments. A laboratory batch experiment using 15 potential amendments was used to select 5 amendments to treat contaminated soil in a pot study using two Barley (Hordeum vulgare L.) cultivars that differed in their ability to accumulate cadmium. Results from this experiment identified 3 of these amendments for use in a field trial. In the pot experiment a reduction in ammonium nitrate extractable Cd (<41%) and Pb (<49%) compared to the controls was measured, with a concurrent reduction of uptake into barley grain (Cd<62%, Pb<68%). In the field extractable fractions of Cd, Pb, and Zn were reduced by up to 96%, 99%, and 99%, respectively in amended soils.

Vertical migration of 60Co, 137Cs and 226Ra in agricultural soils as observed in lysimeters under crop rotation.

In most studies quantifying the migration parameters - apparent migration velocity and apparent dispersion coefficient - of radionuclides in the soil by model calculations, these parameters are determined for undisturbed soils. For soils disturbed by ploughing, however, no such data are available in the literature. Therefore, in the present study, the migration parameters of (137)Cs, (60)Co and (226)Ra were estimated for ploughed soils by means of a convection-dispersion model. The depth distributions of the radionuclides were determined in four lysimeters (area: 1m(2), depth of soil monolith: 0.75m) filled with artificially contaminated soils of different types in July 1990. The lysimeters were cropped with agricultural plants. The soil in each lysimeter was ploughed manually once a year until 1996 (plough depth 20cm). In July 1999, soil samples were collected from three pits in each lysimeter. The depth distributions of all radionuclides proved to be very similar in each soil pit. The spatial variability of the depth distributions of a given radionuclide within the lysimeters was about the same as their variability between the four lysimeters. Evaluation of the migration parameters revealed that the convective transport of the radionuclides was always rather small or even zero, while the dispersive transport caused a "melting" process of the initially sharp activity edge at the lower border of the Ap horizon. These results are explained by the high evapotranspiration (80-90% of the total precipitation plus irrigation) and the small amounts of seepage water during the observation period of 9 years.

Accumulation of radionuclides from radioactive substrata by some micromycetes.

Overgrowing (interaction) and dissolution of intact and milled hot particles by various micromycetes were studied under laboratory conditions. Hot particles used for the investigation originated from the Chernobyl accident release and atomic bomb testing sites. The micromycetes investigated were mitosporic fungi mainly isolated from the Chernobyl site and vicinity. Most of the fungal species and strains showed a tendency to grow towards the hot particle, overgrow it and dissolve it after prolonged contact. The accumulation (absorption and adsorption) of radionuclides from intact hot particles was generally more intensive for (152)Eu than for (137)Cs by a factor of about 2.6-134, while in experiments with milled samples the (152)Eu and (137)Cs accumulation was similar, except for some fungal species, which showed higher (152)Eu than (137)Cs sorption. It could be shown that the main factors influencing Cs and Eu accumulation in fungi are: fungal species and strains and the size and composition of the hot particle.

Radiocaesium contamination of meadow vegetation--time-dependent variability and influence of soil characteristics at grassland sites in Austria.

Long-term trends of 137Cs and 40K concentrations in meadow grass and soil-plant transfer data at eight different sites in Upper Austria are presented. Geometric means of 137Cs TF-data and Tagg values vary between 0.03-1.06 and 0.0005-0.0184 depending on site, respectively. 40K results are less variable with TF values covering a range of 0.31-2.01. Only at one site was a significant decrease of 137Cs concentration (decay-corrected) in meadow vegetation observed during the observation period 1992-1999. Seasonal trends of 40K and 137Cs were investigated at one site in 1996. Both elements show decreasing concentrations in plants from beginning of May-July, followed by a peak in September. Although this pattern was not very pronounced, there are some hints that it may explain deviations of long-term trends in 137CS levels in grass caused by unusual weather conditions as indicated by phenological climate data (beginning of sweet cherry and black elder blossoming). Finally, TF values were correlated with soil characteristics, revealing a negative correlation of radiocaesium soil-plant transfer with soil pH, exchangeable and extractable fractions of Mg, Ca and Na as well as a positive correlation with exchangeable Al.

Microbial population structures in soil particle size fractions of a long-term fertilizer field experiment.

Soil structure depends on the association between mineral soil particles (sand, silt, and clay) and organic matter, in which aggregates of different size and stability are formed. Although the chemistry of organic materials, total microbial biomass, and different enzyme activities in different soil particle size fractions have been well studied, little information is available on the structure of microbial populations in microhabitats. In this study, topsoil samples of different fertilizer treatments of a long-term field experiment were analyzed. Size fractions of 200 to 63 microm (fine sand fraction), 63 to 2 microm (silt fraction), and 2 to 0.1 microm (clay fraction) were obtained by a combination of low-energy sonication, wet sieving, and repeated centrifugation. Terminal restriction fragment length polymorphism analysis and cloning and sequencing of 16S rRNA genes were used to compare bacterial community structures in different particle size fractions. The microbial community structure was significantly affected by particle size, yielding higher diversity of microbes in small size fractions than in coarse size fractions. The higher biomass previously found in silt and clay fractions could be attributed to higher diversity rather than to better colonization of particular species. Low nutrient availability, protozoan grazing, and competition with fungal organisms may have been responsible for reduced diversities in larger size fractions. Furthermore, larger particle sizes were dominated by alpha-Proteobacteria, whereas high abundance and diversity of bacteria belonging to the Holophaga/Acidobacterium division were found in smaller size fractions. Although very contrasting organic amendments (green manure, animal manure, sewage sludge, and peat) were examined, our results demonstrated that the bacterial community structure was affected to a greater extent by the particle size fraction than by the kind of fertilizer applied. Therefore, our results demonstrate specific microbe-particle associations that are affected to only a small extent by external factors.

Fallout strontium and caesium transfer from vegetation to cow milk at two lowland and two Alpine pastures.

Vegetation-to-milk transfer coefficients for 137Cs, 90Sr and stable strontium were determined for cows grazing on two intensively managed lowland pastures and two Alpine pastures in Austria. The 90Sr transfer coefficient at the four pastures ranged from 0.0005 to 0.0012 dl-1 and correlated with the stable strontium transfer coefficient (0.0006-0.0013 dl-1) with the lower values found on the intensively managed pastures. The 137Cs transfer coefficient ranged from 0.0009-0.0045 dl-1.

Transfer of iodine from soil to cereal grains in agricultural areas of Austria.

The concentrations of iodine in cereal grains cultivated at 38 locations in Austria from cereal-producing sites in agricultural areas and soil-to-grain transfer factors (TF) were determined. The concentrations of iodine in cereal grains, which were analyzed by radiochemical neutron activation analysis ranged from 0.002 to 0.03 microg g(-1), the arithmetic mean and the median were 0.0061 microg g(-1) and 0.0046 microg g(-1), respectively. The TF values for cereal grains were calculated to be 0.0005-0.02 and the median was 0.0016. The TF values correlated positively with the iodine concentrations in cereal grains. However, the TF values correlated negatively with the iodine concentrations in soils as well as with the amount of clay contents of soils. The TF values were almost independent on pH values (5.4-7.6) of soils.

90Sr and 137Cs in environmental samples from Dolon near the Semipalatinsk Nuclear Test Site.

The (90)Sr and (137)Cs activities of soil, plant, and milk samples from the village of Dolon, located close to the Semipalatinsk Nuclear Test Site in Kazakhstan, were determined. The areal deposition at the nine sampling sites is in the range of <500 to 6,100 Bq m(-2) and 300 to 7,900 Bq m-2 for (90)Sr and (137)Cs, respectively. Similar values have been reported in the literature. At some of the sites both nuclides mainly have remained in the top 6 cm of the soil profiles; at others they were partly transported into deeper soil layers since the deposition. For most of the samples the (90)Sr yield after destruction of the soil matrix is significantly higher than after extracting with 6 M HCl indicating that (90)Sr is partly associated with fused silicates. The low mean (90)Sr activity concentrations of vegetation samples (14 Bq kg(-1) dw) and milk samples (0.05 Bq kg(-1) fw) suggest that this has favorable consequences in terms of limiting its bioavailability.

Influence of molecular structure on sorption of phenoxyalkanoic herbicides on soil and its particle size fractions.

The sorption and desorption behaviors of four phenoxyalkanoic acid herbicides and their metabolites on four agricultural soils and soil particle size fractions were examined. Generally, there was a trend of increasing adsorption and decreasing desorption in the order mecoprop < MCPA < dichlorprop < 2,4-D. The significant increase in adsorption of the phenolic metabolites can be explained by their lower polarity and enhanced partition in the organic soil matrix. Estimation of sorption distribution coefficients from particle size fraction adsorption data was possible for a sandy soil and a silty Cambisol soil only. It is suggested that increasing steric demand, for example, molecular volume, and slight changes in the polarity of the compounds affect their adsorption properties. Comparison of adsorption and desorption data of structurally similar compounds obtained from a variety of soils allows investigation of structure-induced differences in sorption strength.

Effects of elevated ozone concentration on the degradation of dichlorprop in soil.

An aerobic degradation study was conducted to estimate possible effects of elevated ozone concentration in air on the behaviour of dichlorprop. An average ozone concentration of 80 nL L-1 was chosen, which often occurs close to congested areas during late spring and summer. A control soil and an ozone exposed soil were kept under same conditions such as temperature, air flow and soil humidity. The use of 14C-labelled dichlorprop allowed to examine the fate of dichlorprop and follow the degradation products in soil. Exhaustive extraction of both soils yielded several fractions containing dichlorprop residues. Half lives of dichlorprop of both treatments were 5 days. After 32 days most of the residues in soil remained in the non extractable fraction. The elevated ozone concentration showed no significant effects on the degradation behaviour of dichlorprop and its metabolites but significant differences were found for the behaviour of the nonextractable residues and of the release of carbon dioxide, which were higher for control soil in comparison to the ozone variant. These findings suggest that even moderately elevated ozone concentration in air can effect mineralisation and fixation processes of dichlorprop.

Responses of the soil microbiota to elevated CO2 in an artificial tropical ecosystem.

Plants in artificial tropical ecosystems were grown under ambient (340 microl l(-1)) and elevated (610 microl l(-1)) atmospheric CO2 for 530 d under low-nutrient conditions on a substrate free of organic C. At the end of the experiment a number of soil chemical and microbiological variables were determined. Although we found no changes in total soil organic matter under elevated CO2, we did find that after physical fractionation the amount of organic C in the supernatant (< 0.2 microm) and the amount of water extractable organic C (WEOC) was lower under elevated CO2. The extractable optical density (OD) indicated a higher degree of humification for the elevated than for the ambient CO2 samples (P = 0.032). Microbial biomass C was not significantly altered under high CO2, but total bacterial counts were significantly higher. The microbial biomass C-to-N ratio was also higher at elevated (15.0) than at ambient CO2 (10.0). The number of mycorrhizal spores was lower at high CO2, but ergosterol contents and fungal hyphal lengths were not significantly affected. Changes were found neither in community level physiological profiles (CLPPs) nor in the structural attributes (phospholipid fatty acids, PLFAs) of the microbial community. Overall, the effects on the soil microbiota were small, perhaps as a result of the low nutrient supply and low organic matter content of the soil used in our study. The few significant results showing changes in specific, though relatively minor, organic matter pools may point to possible long-term changes of the more major pools. Furthermore, the data suggest increased competition between plants and microbes for N at high CO2.

Distribution of radiocaesium in an Austrian forest stand.

Within an Austrian spruce stand, vertical distribution of radiocaesium in soil as well as 137Cs concentration in different forest ecosystem compartments including spruce and surface water were investigated 10 years after the Chernobyl accident. The total 137Cs inventory in the forest was estimated to be 46 kBq m-2 (ref. date: 86-05-01). From the collected data annual input rates via litterfall of 0.48% per year and output rates through waterflows of only 0.02% per year were derived. The results identify the high importance of forest soils as a sink for radiocaesium. The estimated ecological residence half-times turned out to be highest in the organic soil horizons (1-3 years per cm), whereas in mineral horizons the values decrease significantly. As a consequence, soil inventory represents more than 95% of the total, whereas only approximately 3.3% of the 137Cs inventory is stored in the living biomass of spruce trees and a further 0.5% in the phytomass of understorey vegetation.

Plant uptake of radionuclides in lysimeter experiments.

The results of seven years lysimeter experiments to determine the uptake of 60Co, 137Cs and 226Ra into agricultural crops (endive, maize, wheat, mustard, sugarbeet, potato, Faba bean, rye grass) are described. The lysimeter consists of twelve monolithic soil profiles (four soil types and three replicates) and is located in Seibersdorf/Austria, a region with a pannonian climate (pronounced differences between hot and semi-arid summers and humid winter conditions, annual mean of precipitation: 517 mm, mean annual temperature: 9.8 degrees C). Besides soil-to-plant transfer factors (TF), fluxes were calculated taking into account biomass production and growth time. Total median values of TF's (dry matter basis) for the three radionuclides decreased from 226Ra (0.068 kg kg(-1)) to 137Cs (0.043 kg kg(-1)) and 60Co (0.018 kg kg(-1)); flux values exhibited the same ranking. The varying physical and chemical properties of the four experimental soils resulted in statistically significant differences in transfer factors or fluxes between the investigated soils for 137Cs and 226Ra, but not for 60Co. Differences in transfer between plant species and plant parts are distinct, with graminaceous species showing, on average, TF values 5.8 and 15 times lower than dicotyledonous species for 137Cs and 60Co, respectively. This pattern was not found for 226Ra. It can be concluded that 137Cs transfer is heavily influenced by soil characteristics, whilst the plant-specific factors are the main source of TF variability for 60Co. The variability of 226Ra transfer originates both from soil properties and plant species behaviour.