Simulation of solution chemistry in an acidic forest soil

The computer simulation model SOILEQ was used to estimate soil solution chemistry over a 7 week period from October 3 to November 14, 1988 in the soils of a sugar maple forest located near St. Hippolyte, Quebec, Canada. Model parameters for pH-dependent CEC and exchangeable cations were calculated from laboratory measurements while soil solution chemistry, including Al solubility, at the start of the simulation was taken from values obtained from lysimeter samples. Model predictions were compared with values obtained from 12 sets of soil solution collectors over the same time period. Predicted values of Ca, Mg and K in the mineral soil horizons at 25-, 75- and 125-cm depths generally fall within the 95% confidence interval of the median for the measured values. Simulated values of pH and inorganic Al are not as close to the measured values. Some error due to drift is apparent, most notably for base cations in solutions leaving the organic surface horizons, and may be attributable to decomposition of organic matter, not included in the simulation model. The results indicate that other mechanisms that release H* (nitrification, for example) and base cations (mineral weathering or mineralization of organic matter) need to be considered.     

Organic matter dynamics in a temperate forest as influenced by soil frost

In the future, climate models predict an increase in global surface temperature and during winter a changing of precipitation from less snowfall to more raining. Without protective snow cover, freezing can be more intensive and can enter noticeably deeper into the soil with effects on C cycling and soil organic matter (SOM) dynamics. We removed the natural snow cover in a Norway spruce forest in the Fichtelgebirge Mts. during winter from late December 2005 until middle of February 2006 on three replicate plots. Hence, we induced soil frost to 15 cm depth (at a depth of 5 cm below surface up to –5°C) from January to April 2006, while the snow‐covered control plots never reached temperatures < 0°C. Quantity and quality of SOM was followed by total organic C and biomarker analysis. While soil frost did not influence total organic‐C and lignin concentrations, the decomposition of vanillyl monomers (Ac/Ad)_V and the microbial‐sugar concentrations decreased at the end of the frost period, these results confirm reduced SOM mineralization under frost. Soil microbial biomass was not affected by the frost event or recovered more quickly than the accumulation of microbial residues such as microbial sugars directly after the experiment. However, in the subsequent autumn, soil microbial biomass was significantly higher at the snow‐removal (SR) treatments compared to the control despite lower CO₂ respiration. In addition, the water‐stress indicator (PLFA [cy17:0 + cy19:0] / [16:1ω7c + 18:1ω7c]) increased. These results suggest that soil microbial respiration and therefore the activity was not closely related to soil microbial biomass but more strongly controlled by substrate availability and quality. The PLFA pattern indicates that fungi are more susceptible to soil frost than bacteria.     

The composition of the soil solution as influenced by fertilization and nutrient uptake

The composition of the soil solution in unfertilized and well-fertilized plots of three long-term field experiments has been determined at the beginning and at the end of the growing season. All the plots were manured and the K and P fertilizers given in the autumn before the growth of sugar beet. N was applied in the spring, 3–4 weeks before the first soil sampling.The soil solution was removed at a pressure of 5 atm. The composition and the corresponding osmotic pressure were calculated for the moisture contents at field capacity and wilting point.In spring the salt concentrations, cations + anions, at the field capacity were in the range 91–97 mmoles/l in the fertilized plots. In autumn the concentration had dropped to 13.9–20.3, a decrease of 78–85%. At the wilting point, the concentrations in spring were as high as 211–307 mmoles/l and in autumn 31.5–69 mmoles/l. The corresponding osmotic pressures at field capacity in the spring ranged 2.2–2.3 atm. and at wilting point 5.1–7.4 atm.In spring the unfertilized plots showed concentrations of 16–21 mmoles/l and osmotic pressures of 0.38–0.51 atm., the values decreasing 52–65% during the growing season.It was pointed out that the high soil-solution concentration and osmotic pressure at low moisture contents may lead to an unfavourable effect on root metabolism. Further, the obscuring effect of the varying soil-solution concentration on the relationships between root ion exchange and nutrient uptake by plants has been discussed.     

Aluminium phosphates as products of transformations of fertilizer phosphorus in an acid soil

The interactions of double superphosphate in an acid soddy-podzolic soil initially give rise to R-amorphous aluminium phosphates. These, however, have small admixtures of cryptocrystalline phases, indicating the beginning of the formation of aluminium phosphate minerals. Model experiments have demonstrated that minerals of the variscite group, mainly metavariscite, can be synthesized in the zone of reaction of the fertilizer P₂O₅ in an acid soil. Metavariscite, variscite and aluminium phosphates of various degrees of crystallization were studied with respect to the solubility and availability of their phosphorus to plants. The results of the experiment show metavariscite to have better solubility and higher availability to plants than variscite. Crystal aluminium phosphates seem to satisfy about 10–25% of the phosphorus needs of crops. Newly precipitated aluminophosphates have much higher availability.     

Cation exchange capacity of an acid soil as influenced by different sources of organic litter

Abstract

A pot trial was conducted in order to relate the increase in the cation exchange capacity (CEC) of an acid soil (Quartspsament) to the CEC of several organic materials which were added to it. Peat, sugarcane bagasse and filter cake from sugar industry, worm compost, poultry and cattle manure, compost, and papermill sludge were incubated in natural and limed soil under controlled soil water content. Soil CEC was measured at soil pH after 30 and 90 days of incubation and results were strongly affected by pH of the incubated soil. About 32% of the soil CEC would be predicted by the CEC of the organic material measured at pH 7.0. This proportion increased to 78% when soil pH was included in the regression.     

Effects of acid anion additions (trifluoroacetate and bromide) on soil solution chemistry of a northern hardwood forest soil

Experimental plots within the Hubbard Brook Experimental Forest, NH, were treated with sodium trifluoroacetate (TFA) and lithium bromide (Br), to study the impact of TFA alone and in the presence of increased anion concentrations (e.g. acid deposition) on the soil solution chemistry of a northern hardwood forest soil. Trifluoroacetate is a major atmospheric degradation product of replacement compounds of chlorofluorocarbons (CFC) and Br is widely used as a hydrologic tracer. Calculated drainage losses via soil water flow were less than 60% of inputs, added during the summer, and TFA and Br were temporarily retained in the soil until fall. The initial indication of an acid input of the treatments (HTFA, HBr) in the Bs2 horizon, which reflects stream water chemistry as well, was an increase of base cations in the soil solution, decreasing the soil's acid neutralizing capacity. Thereafter, trifluoroacetate and Br concentrations peaked after the peak in base cations, synchronous with peaks in H⁺ and Al concentrations. Organic anions, nitrate and chloride played the major role in accompaning base cations out of the solum. Sulfate retention at soil adsorption sites was increased by the presence of TFA and Br, reducing its role as a mobile anion of base cations in this experiment. Relative retention of anions for the whole profile of this northern hardwood forest soil was estimated by correlation analyses and input-output balances in decreasing order on an equivalant basis: SO₄ > TFA = Br ≥ Cl > NO₃ > organic anions. Recovery from acid additions were recorded within several weeks after the treatments were stopped. Evaluating the impact of added chemical compounds to soils must be considered within the context of linkages among element cycles and pools.     

Cadmium fractions in an acid sandy soil and Cd in soil solution as affected by plant growth

In a previous experiment, plants were able to immobilize or solubilize Cadmium (Cd) in a sandy acid soil enriched with 40 μmol Cd kg^–1, because Cd solution concentration was decreased by maize (Zea mays) and sunflower (Helianthus annuus), and increased by flax (Linum usitatissimum L. ssp. usitatissimum) and spinach (Spinacia oleracea). It is assumed that the equilibrium with Cd fractions in the soil solid phase and the chemical form of Cd in the soil solution were affected. In the present study, the effect of the four plant species mentioned above on Cd binding in soil was investigated by means of a fractionation of soil Cd with a sequential extraction of seven steps. The seven fractions of Cd are operationally defined by the extraction sequence that follows the order of increasing acidity with extractants of different complexing and redox properties. In the unplanted soil, Cd was predominantly present in the exchangeable Fraction I (F. I) and easily mobilizable Fraction II (F. II) (64%). Significant concentrations of Cd were found in F. III (occluded in Mn oxides; 22%) and F. IV (organically bound; 10%). Fractions V (occluded in poorly crystalline Fe oxides), F. VI (occluded in well crystallized Fe oxides), and F. VII (residual fraction) amounted to less than 5% of the total soil Cd concentration. The plants changed the binding of Cd in soil in a different manner. All plants decreased F. I, but F. II was increased by maize and spinach, decreased by flax or remained unaffected by sunflower. Fraction III was not affected by maize and flax, but decreased by sunflower and spinach, and F. IV was not affected by sunflower and spinach, but was increased by maize and flax. These changes of Cd fractions were not related to the changes the plants had caused in total Cd or Cd²⁺ concentration of the soil solution. These results show that plant species differ in how they affect Cd binding to the soil solid phase, but this effect is not related to how they affect Cd in soil solution. The mechanisms by which plants affect the relationship between the soil solid and liquid phase are still unclear.     

Leaching of metals from a spruce forest soil as influenced by experimental acidification

Acidified (H₂SO₄+HNO₃, 3:1) throughfall waters (pH 3.16 and 3.40 as volume weighted means or control (untreated throughfall water, pH 3.72) were applied for 3.5 yr by an automatic irrigation device to lysimeters containing podzolized spruce forest soils of 0–5, 0–15 and 0–35 cm soil depth. The total volume of the leachates was measured together with their pH and total content of DOC, Na, K, Ca, Mg, Fe, Mn, Al, Cu, Zn, Cd and Pb and the initial amounts of metals and H in the soil. The main part of H⁺ added with the throughfall waters was retained within the soil. Concentrations and fluxes of Mg, Ca, Mn, Zn and Cd in the soil were significantly increased by addition of acidified throughfall waters; K was less affected. As a consequence of lowered flux of DOC in the A horizon as acid input increased, Fe, Al, Cu, and Pb fluxes also decreased. The mobility of these metals in the A horizon was shown to be regulated mainly by the formation of watersoluble organic compounds rather than directly by pH variations. Compared to the control, the additional annual loss of Mg from the soil profile in the most acid treatment was c. 10% of the currently exchangeable amount.     

The relationships among microbial parameters and the rate of organic matter mineralization in forest soils,as influenced by forest type

Vegetation type influences the rate of accumulation and mineralization of organic matter in forest soil, mainly through its effect on soil microorganisms. We investigated the relationships among forest types and microbial biomass C (MBC), basal respiration (R_B), substrate-induced respiration (R_S), N mineralization (N_min), specific growth rate μ, microbial eco-physiology and activities of seven hydrolytic enzymes, in samples taken from 25 stands on acidic soils and one stand on limestone, covering typical types of coniferous and deciduous forests in Central Europe. Soils under deciduous trees were less acidic than soils of coniferous forests, which led to increased mineralizing activities R_B and N_min, and a higher proportion of active microbial biomass (R_S/MBC) in the Of horizon. This resulted in more extractable organic C (0.5 M K₂SO₄) in soils of deciduous forests and a higher accumulation of soil organic matter (SOM) in coniferous forest soil. No effect of forest type on the microbial properties was detected in the Oh horizon and in the 0–10 cm layer. The microbial quotient (MBC/C_org), reflecting the quality of organic matter used for microbial growth, was higher in deciduous forests in all three layers. The metabolic quotient qCO₂ (R_B/MBC) and the specific growth rate μ, estimated using respiration growth curves, did not differ in soils of both forest types. Our results showed that the quality of SOM in coniferous forests supported microorganisms with higher activities of β-glucosidase, cellobiosidase and β-xylosidase, which suggested the key importance of fungi in these soils. Processes mediated by bacteria were probably more important in deciduous forest soils with higher activities of arylsulphatase and urease. The results from the stand on limestone showed that pH had a positive effect on microbial biomass and SOM mineralization.     

Aluminium contamination and other changes of acid soil solution isolated by means of porcelain suction-cups

Comparison was made between the chemical composition of soil solutions isolated by means of a suction method using porcelain cups and by centrifugation. The soil solutions were isolated from three depths of field plots, where the soil (Typic Haplohumod) had been subjected to various pretreatments.
The cups were made of mullite and corundum as shown by X-ray diffraction analysis. The material when powdered had a cation exchange capacity of about 10meq kg⁻¹. Solutions with similar ionic strengths were obtained by the two methods, but the cups were found to release substantial amounts of Al and to adsorb H, Ca, K, Na and organic matter.
After the cups had been placed in the soil for more than 7 months, calculations suggested that the Al activity in cup solutions was controlled by amorphous gibbsite. This amorphous material was probably produced by proton-induced decomposition of part of the cup material. It is concluded that such cups are improper for isolation of soil solution from acid soils.     

Rice and common bean growth and nutrient concentration as influenced by aluminum on an acid lowland soil

Aluminum (Al) toxicity is a major limiting factor for crop production in many acid soils in Brazil. Two greenhouse experiments were conducted to evaluate response of rice (Oryza saliva L.) and common bean (Phaseolus vulgaris L.) to Al levels on a Low Humic Gley acid soil. The Al levels created by liming were: 0,0.03, 0.10, 0.23, 1.03, and 3.83 cmol_c kg^‐1 of soil. Rice dry matter and grain yield were significantly improved (P<0.05) with increasing Al levels in the soil solution. However, common bean dry matter as well as grain yield were significantly (P<0.01) decreased with increasing Al levels. At 3.83 cmol_c Al kg^‐1 of soil, bean did not produce any dry matter or grain yield. On an average, Al decreased nutrient concentrations in the tops of rice plant except zinc (Zn) and manganese (Mn), but in bean crop almost all the nutrients concentrations were increased with increasing Al levels. Rice showed tolerance to Al toxicity, whereas, common bean was susceptible to toxicity of this element. For successful intensive crops production lime application will be necessary in Varzea soils especially for legume production.     

Effects of liming and fertilization on soil solution chemistry in North German forest ecosystems

The effect of aboveground liming and fertilization as well as ploughing and liming of forest soils on soil solution chemistry was studied in various experimental plots of the German Solling area. Due to low solubility of limestone, aboveground liming had only moderate effects on soil pH and base saturation of CEC. Calcium and Mg concentration increased and Ca/Al and Mg/Al ratios of the soil solution improved. Despite extreme doses of lime, nitrate leaching did not increase in the case of a beech plot. Elevated nitrate leaching was found in the case of a spruce and a beech plot previously fertilized with N. Nitrate concentrations are far from drinking water thresholds in the case of beech. Nitrate levels of soil solution of the unfertilized spruce plot are in the range of 3 to 8 mg L⁻¹. Liming did increase these values slightly in the first years, and nitrate levels reached those of the untreated plot in the following years. Ploughing connected with high liming doses obviously led to inhomogeneous distribution of lime. No significant deacidification of seepage water at a depth of 100 cm occurred because of leaching of sulfate from the industrial lime used. This was followed by Al-leaching. Nitrate levels slightly exceeded drinking water standards throughout the first winter period after the measure. The development of young trees was significantly improved.     

Redox condition and nitrate change in a newly flooded rice soil under percolation as influenced by oxidative iron and manganese

Nitrate leaching from intermittently flooded rice fields contributes to nitrate pollution in groundwater. In this study, redox conditions and nitrate change in a newly flooded rice soil under the influence of oxidative iron (Fe) and manganese (Mn) were investigated using flooded soil columns under moderate percolation (4.2?mm?d^?1). The amendments of α-Fe₂O₃ and β-MnO₂ powder (5 and 2.7?mg?g^?1, respectively) delayed the establishment of reducing conditions and lowered the rate of nitrate removal in the soil column, and subsequently increased the percolation of soil indigenous nitrate (8.3?mg nitrogen [N]?kg^?1) from 2.0% to 8.0%, and the percolation of externally amended nitrate (250?mg?N?kg^?1) from 11.0% to 26.0%. The pool of oxidative iron-centered metal oxidants needs to be jointly considered with the availability of organic carbon and hydrological conditions in evaluating redox conditions and nitrate change in intermittently flooded rice soils.     

Aluminium speciation and pH of an acid soil in the presence of fluoride

The aim was to determine whether the addition of F to an acid soil reduces the concentration of free Al³⁺ and other forms that have been shown to be toxic to plants. The ability of two different extracts to reflect Al speciation in the soil solution was also investigated. Addition of F (0-5.2μmolg⁻¹) to an acid soil (pH 4.15, soil solution) increased the pH and total concentrations of Al and F in the soil solution whereas Al³⁺ remained constant or decreased. Soil solution pH, total soluble Al and Al extracted by 0.01 m CaCl₂ are not good predictors of the likelihood of aluminium toxicity in soils containing soluble fluoride.     

Soil solution chemistry in the rhizosphere of beech (Fagus silvatica L.) roots as influenced by ammonium supply

Roots can induce significant changes in the rhizosphere soil. The aim of the present study was to investigate the influence of beech (Fagus silvatica L.) roots on the chemistry of the rhizosphere soil solution. Special emphasis was given to the effect of the NH₄⁺ supply since many forest soils presently receive high NH₄⁺ inputs from atmospheric deposition. In a mature beech stand, a non‐mycorrhized long root was forced to grow into a rhizotrone filled with homogenized acidic forest soil from the Bw horizon of a Dystric Cambisol. Beside the control, a NH₄⁺ enriched treatment was installed. Thirty micro suction cups of 1 mm diameter and 0.5 cm length were placed in a systematic grid of 5 × 10 mm in each rhizotrone to enable root growth through the grid. The water potential of the soil was kept constant by supplying a synthetic soil solution. Small amounts of soil solution were sampled periodically from May to October 1999 and analyzed by capillary electrophoresis for major cations and anions. Furthermore, pH and conductivity were measured by micro electrodes. In the laboratory experiments, beech seedlings were grown in rhizotrones in a control and in a NH₄⁺ fertilized soil. The equipment for sampling soil solutions and the soil conditions in the laboratory was similar to the field experiment. In each rhizotrone a single long root grew through the lysimeter grid. The laboratory conditions induced higher rates of nitrification as compared to the field. Thus, the overall concentration range of the soil solution was not comparable between field and laboratory studies. In all treatments average soil solution concentrations of H⁺ and Al³⁺ were significantly higher in the rhizosphere than in the bulk soil. The NH₄⁺ treatment resulted, in the field and laboratory, in a strong increase of the H⁺ and Al³⁺ concentrations in the rhizosphere, accompanied by an accumulation of Ca²⁺, Mg²⁺, and NO₃^—. The observed rhizosphere gradients in soil solution chemistry were highly dynamic in time. The results demonstrate that the activity of growing beech roots results in an acidification of the soil solution in the rhizosphere. The acidification was enhanced after the addition of NH₄⁺.     

Micro-scale variation of solid-phase properties and soil solution chemistry in a forest podzol and its relation to soil horizons

In order to evaluate micro-scale heterogeneities 55 micro suction cups were placed in an array at 15 mm intervals in a profile face of a cambic podzol. The chemistry of soil solution (mineral anions, pH, UV absorption as a measure for DOC) was compared with solid-phase properties from soil samples (2 cm³ volume), which had surrounded the suction cups. Sequential extraction techniques (water, NF₄Cl, hydroxylamin-hydrochloride, citrate-bicarbonate, oxalate, dithionite-citrate-bicarbonate) and base titrations were applied to characterize the solid phase. Although the average soil solution concentrations between horizons often differed significantly, the spatial distributions of pH and SO₄^2? did not correlate with soil horizon borders. Even if concentration isolines and soil horizon borders were parallel, marked concentration gradients could be observed within individual soil horizons. The less intense the interaction between solute ion and soil matrix, the greater was the variation in solution concentration within a soil horizon. For the soil solid phase only a weak correlation of slow buffer reactions to soil horizons was found. The distribution of extractable Fe and Al was typical for a podzol profile, however, with very steep gradients within single soil horizons. Except for pH, which was related mainly to citrate-bicarbonate extractable aluminium, no solid-phase characteristic showed a clear correlation with soil solution chemistry.     

Reversibility of soil solution acidity and of sulfate retention in acid forest soils

To quantify the effects of reduced sulfate input on the chemistry of soil solution and soil S storage in acid forest soils, an experiment with undisturbed soil columns from two different sites was implemented. The acid cambisol of the Solling is subjected to a high sulfate input and especially the B-horizon has a high sulfate content. On the contrary, the podzol of the Fuhrberg site is subjected to low input and has low sulfate content. Undisturbed soil columns were taken from both sites and were irrigated at 6 °C with a precipitation rate of 3 mm d^?1 over 10 mo. In treatment No. 1, an artificial throughfall with pH 5.2 and reduced sulfate load (45 μmol L^?1) was applied. In treatment No. 2, an artificial througfall representing a high sulfate deposition (427 μmol L^?1, pH 3.2) was used. In case of the Solling soil, the pH of soil solution was unaffected by treatments during the entire experiment. Alkalinity of the soil solution was slightly increased in treatment No. 1 at a depth of 20 cm. While treatment No. 1 resulted in a reduction of the sulfate concentrations of the soil solution in the top soil, sulfate concentrations were unaffected at a depth of 40 cm. The B-horizon of the Solling soil prevented deacidification of the soil solution by desorption of previously stored sulfate. In case of the Fuhrberg soil, treatment No. 1 resulted in reduced sulfate concentrations of the soil solution even in deeper soil layers with concentrations approaching input levels. The pH of the solution was slightly elevated and the alkalinity of the solution increased. Organic S compounds in the soil seemed to have no influence on sulfate release in either soils.     

Fixation of radiocaesium in an acid brown forest soil

The OAh and Ah horizons of acid brown and podzolic forest soils are reported to fix more radiocaesium than the mineral B horizons beneath them. We determined the respective influence of organic matter and clay minerals on the magnitude of Cs⁺ retention in a strongly acid brown forest soil in Belgium. The soil contained mica throughout the profile. Vermiculite was identified in the OAh and Ah horizons, and hydroxy interlayered vermiculite (HIV) in the Bw horizon. The OAh and Ah clay fraction retained much more Cs⁺ than the Bw horizon. The extraction of Al interlayers by Na-citrate resulted in a marked increase in Cs⁺ fixation in the Bw clays as well as the collapse of the vermiculitic layers after K⁺ saturation. Organic matter had a strong but indirect effect on Cs⁺ fixation. In the Bw horizon, acid weathering of layer silicates releases free Al and produces HIV minerals in which Al polymers block the access of radiocaesium onto Cs⁺-specific sites. In OAh and Ah horizons, free Al is complexed by organic acids. Consequently, the interlayer specific sites remain accessible for Cs⁺ fixation.     

Effect of simulated sulfuric acid rain on the chemistry of a sulfate-adsorbing forest soil

Simulated H₂SO₄ rain (pH 3.0, 3.5, 4.0) or control rain (pH 5.6) was applied for 3.5 yr to large lysimeter boxes containing a sulfate-adsorbing forest soil and either red alder (Alnus rubra Bong) or sugar maple (Acer saccharum Marsh.) seedlings. After removal of the plants and the litter layer, soil samples were obtained at 15-cm intervals to a total depth of 90 cm. Elevated SO₄ concentrations caused by the simulated H₂SO₄ rain were most pronounced for the top 15 cm, but extended down to 45 cm (maple) or 75 cm (alder). There were no effects on SO₄ concentrations at a depth of 75 to 90 em. This confirmed the existence of a sulfate front between 20 cm and 100 cm, as postulated earlier on the basis of extracted soil solutions. Decreases in Mg and Ca concentrations, base saturation, and soil pH were limited to the uppermost 15 cm and, in most cases, to the pH 3.0 treatment. Concentrations of Mg and Ca for the pH 3.0 treatments were greater than control at a depth of 15 to 30 cm, indicating transport of these cations from the soil surface. Concentrations of Na and K, and cation exchange capacity, were not affected by simulated H₂SO₄ rain. Elevated concentrations of NO₃ and extractable Zn throughout the alder systems indicated (1) either increased rates of symbiotic N-fixation or decreased rates of N immobilization; and (2) mobilization of Zn by all acid rain treatments.     

Changes in chemistry and mineralogy of forest soils by acid rain

The goal of the present study was a qualitative and quantitative determination of chemical and mineralogical changes in forest soils due to acid atmospheric depositions. In the NE/SE Vienna Woods soil samples were taken at 4 depths (0 to 5 cm, 5 to 10 cm, 10 to 20 cm, 20 to 30 cm) in the contaminated infiltration zone of stemflow (S) of 8 beech trees (Fagus sylvatica), strongly influenced by acid atmospheric depositions (soil-pH 2.8 to 3.0) and in their non contaminated reference areas (R) between trees, where acid imput is much smaller (soil-pH 5.0 to 6.0). The results show that intensive weathering processes took place in the contaminated soil areas, which show higher clay and silt contents and smaller aggregates, as well as clay illuviation. Moreover, in the top of the contaminated soil areas higher contents of C_t and S_t and of the heavy metals Pb, Zn and Cu could be observed, accompanied by extreme low base saturation (expecially of Ca and Mg) and high Al-saturation (50 to 80% of the CEC). These data were confirmed by analysis of the water saturation extract. Moreover, in the contaminated top soils high amounts of Fe-oxides were found, whereas no “secondary” Al-chlorite (due to its instability at pH-values <4.0) could be traced. The desilification process which took place at the same time could be shown through total element analysis. In the clay-fraction strong weathering led to a loss of layer charge and to the genesis of highly expandable three-layer-silicates which could be determined by X-ray diffraction using n-alkylammonium-chloride technics and other chemical treatments.