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1.
The profile distributions of oxalate- and pyrophosphate-soluble Al compounds and oxalate-soluble Si compounds in the main horizons of pale-podzolic soils of the Central Forest Reserve and the fractions <1. 1–5, and >5 μm have been considered. In the clay-eluvial part of soil profile, the content of these compounds is differentiated by the eluvial–illuvial type with a clear accumulation in the EL horizon compared to the AEL horizon. This distribution is largely ensured by their differentiation in the clay and fine silt fractions, while an accumulative distribution of mobile Al compounds is observed in fractions >5 μm. The high correlation between the Al and Si contents in the Tamm extracts from the clay and fine silt fractions with the (Alox–Alpy)/Siox molar ratios, which are in the range of 1–3 in the EL horizon, confirms that mobile compounds are accumulated in these fractions in the form of amorphous aluminosilicates. In the AEL and EL horizons, an additional amount of Al can pass into the oxalate solution from the fine fractions due to the dissolution of Al hydroxide interlayers of soil chlorites. The eluvial–illuvial distribution of mobile Al and Si compounds typical for Al–Fe–humus podzols within the clay-illuvial part of profiles of the soils under study can be considered as an example of superimposed evolution.  相似文献   

2.
H.H. Le Riche 《Geoderma》1973,9(1):43-57
This previously described buried soil, developed in uniform parent material, was used to study the relative movements of elements and other soil components down the profile. Samples from all horizons were treated with hydrogen peroxide and ammonium oxalate, under ultra-violet light, to remove organic matter and sesquioxides, and the residues were subdivided into six particle size fractions.Downward movement of clay (< 0.5 μm) was accompanied by movement of extractable Al2O3 and Fe2O3, thus identifying these as part of the mobile fraction. The less close relationship of extractable Fe2O3 to the clay suggested that it also occurred partly in coarser aggregates. Proportions of minor elements extracted varied from < 1% for Sr to nearly complete extraction of Co, Cu and Mo in some horizons. The extractable fractions of most minor elements throughout the profile behaved more like Fe2O3 than Al2O3. In the extraction residues, nearly all elements were enriched in the clay fractions relative to the coarser fractions; this being greatest for V and Fe.  相似文献   

3.
Small fragments of intermeshed fibrous material of high electron density were observed by electron microscopy in the fine (< 0.5 μm) clay taken from an iron-rich cemented layer forming part of the B horizon of a Podzol (Typic Haplorthod). Each fibre was about 5 nm in width and about 100 nm in length. Similar material was also common in larger (0.5–2.0 μm) clay fractions but here it occurred as unbroken particles which resembled bacteria in shape and size. At high magnifications, individual fibres were seen to consist of very small (5 nm) particles aligned along the length of each fibre.Electron microanalysis of the fibrous material showed it to consist of iron, aluminium and silicon. The average composition (water-free basis) of seventeen bacteria-like particles was 66% Fe2O3, 22% Al2O3 and 11% SiO2. The particles were positively identified as aluminium-substituted goethite by selected-area electron diffraction.The fibrous material was completely dissolved by dithionite-citrate-bicarbonate treatment but was only slightly affected, if at all, by ammonium oxalate, pH3, in darkness. Other extraction data and X-ray diffraction results showed that the clay also contained considerable amounts of material of short range order, probably in the form of ferrihydrite and allophane.  相似文献   

4.
律兆松  徐琪 《土壤学报》1993,30(3):274-288
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5.
The phosphatase activity (PA) was studied in the chestnut paleosols buried in 1718–1720 under the Anna Ivanovna rampart in the southern part of the Privolzhskaya Upland and in the middle of the third millennium BC under the burial mound of the Bronze Age on the Northern Yergeni Upland; the background analogues of these soils were also examined. The PA values in the fresh soil samples varied from 2.5 to 37 mg of P2O5/10 g of soil per h with maximums in the A1 horizon of the surface soils and in the B1 horizon of the paleosols. The PA values depended on the time of storage of the samples: with time, they increased by 2.6–2.9 times in the A1 horizon of the background surface soil and decreased by 20–60% in the other soil samples. The specific distribution patterns of the PA values in the soil profiles remained the same independently of the time of storage of the samples. Relatively small amounts of the soil samples were sufficient for the reliable determination of the PA: 1–2 g for the A1 horizon and 3–5 g for the B1 and B2 horizons. The time of incubation with the substrate had to be increased up to 4 h for the long-stored samples.  相似文献   

6.
Concentrations of dialysable silica in equilibrium with Al2O3-SiO2-H2O sols at pH 4.5–5.0 confirm the formation of a poorly ordered non-dialysable proto-imogolite species with an Al : Si ratio near 2, close to that of imogolite. Sols with Al : Si>2 give nearly constant levels of free silica in solution in the range 2–6 μg/cm3, indicating equilibrium between proto-imogolite and aluminium hydroxide species. These findings indicate that imogolite-like precipitates in acid soils will buffer silica in solution to within this range during leaching episodes. Imogolite is more stable than a previous estimate suggested, and a revised value for its free energy of formation is proposed: ΔG0f(298.15) = -2929.7 kJ/mol. In Fe2O3-SiO2-H2O sols, the Fe : Si ratio of the non-dialysable species varies smoothly from 11 to 3 as free silica in solution ranges from 4 to 35 μg/cm3. Such sols are much less colloidally stable than hydroxyaluminium silicate sols, but mixed Al2O3—Fe2O3—SiO2—H2O sols are almost as stable as iron-free sols up to a Fe : Al ratio of 1.5. Thus migration of Al and Fe as mixed hydroxide sols can account for the almost constant ratio of Al to Fe with depth in oxalate extracts from Bs horizons of podzols.  相似文献   

7.
Examination by infrared spectroscopy and electron microscopy of the fine clays (<0.5 μm) dispersed at pH 3.5 from H2O2-treated soil indicates that imogolite and proto-imogolite allophanes are concentrated in podzolic B2 and B3 horizons, and make up at least 6 percent of one B2 horizon soil, which contains virtually no layer silicate clays. It is argued here that imogolite-type components are the principal source of extractable aluminium and silicon in such horizons, that they may act as cementing agents in indurated horizons, and that proto-imogolite, a soluble aluminium-silicate complex, is the predominant mobile form in which aluminium is transported to B2 and lower horizons of podzols. Comparison of the amounts of aluminium extracted by acetic acid with those extracted by EDTA indicates that extractable aluminium in Bhg, Bh, and organic-rich A2 horizons is present principally in organic complexes. It is proposed that the aluminium fulvates concentrated in these horizons are formed in situ.  相似文献   

8.
Data from two Podzol O and E horizons, sampled in 1-cm layers at 13 points within 2 m × 2 m plots, were used to test the hypothesis that the composition of hydrogen ions (H) and aluminium (Al) adsorbed to the solid-phase soil organic matter (SOM) determines pH and Al solubility in organic-rich acidic forest soils. Organically adsorbed Al was extracted sequentially with 0.5 m CuCl2 and organically adsorbed H was determined as the difference between total acidity titrated to pH 8.2 and Al extracted in 0.5 m CuCl2. The quotient between fractions of SOM sites binding Al and H (NAl/NH) is shown to determine the variation in pH and Al solubility. It is furthermore shown that models in which pH and Al solubility are linked via a pH-dependent solubility of an Al hydroxide and in which cation exchange between Al3+ and Ca2+, rather than cation exchange between Al3+ and H+, is the main pH-buffering process cannot be used to simulate pH or Al solubility in O and E horizons. The fraction of SOM sites adsorbing Al increased by depth in the lower O and throughout the E horizon at the same magnitude as sites adsorbing H decreased. The fraction of sites binding the cations Ca2+ + Mg2+ + K+ + Na+ remained constant. It is suggested that a net reaction between Al silicates (proton acceptors) and protonated functional groups in SOM (proton donors) is the long-term chemical process determining the composition of organically adsorbed H and Al in the lower part of the O and in the E horizon of Podzols. Thus, in the long term, pH and Al solubility are determined by the interaction between organic acidity and Al alkalinity.  相似文献   

9.
Cores of podzolic soil (monolith lysimeters) were treated for 4.8 yr with 1500 mm yr?1 of either 0.5 mM H2SO4 at pH 3, equivalent to 24 g S m?2 yr?1 (acid treated) or distilled water (controls). The acid treatment was about 37 times greater than the average annual input of H3O+ from rain at the site from which the monoliths were taken. Acid treatment acidified the litter (from pH(CaCl2)3.4 to pH(CaCl2)2.6) and the mineral soil to a depth of 80 cm (mean pH(CaCl2) decrease of 0.2 unit). In the litter and upper A horizon, ion-exchange reactions provided the main neutralizing mechanism, resulting in a decrease in the reserves of extractable (in 2.5 % acetic acid) Ca, Mg, and Mn of about 70 to 80 %. Dissolution of solid phase Al from hydrous oxides provided most neutralization below this depth. Al3+ was the principal soluble Al species throughout the profile. In the litter and upper A horizon, some of the mobilized Al3+ was retained on cation exchange sites resulting in an increase in exchangeable Al. Deeper in the profile, where the exchange sites were effectively saturated with Al3+, no increase in exchangeable Al occurred, and Al3+ was, therefore, available for leaching. Some reversible adsorption of SO4 2?, associated with hydrous Al oxides, occurred in the Bs and C horizons. The results are discussed in relation to possible effects of acid deposition over regions of Europe and N. America.  相似文献   

10.
Material balance in an aquic Hapludalf from loess by means of IR-phase analysis Grain size fractions of an aquic Hapludalf from loess near Göttingen were examined mineralogically and chemically. On the base of actual mineral composition (mode) by means of infrared spectroscopy weathering balances were made up. The results reveal a strong illite/mica loss of about 80 kg/m2, which is due to decomposition in the A-horizon, and which is not compensated by a slight gain in the B-horizon. The mineral balance of the total profile yields a clay degradation of 44 kg/m2. Furthermore, in the A-horizon the chemical balance gives evidence of considerable mobilizations and substantial losses mainly of SiO2, Al2O3, MgO and K2O combined in silicates. Depending on soil horizons and grain sizes the illites have K-contents varying from 4 to 8% K2O. Al2O3 and MgO also show distinct variations. Both components are correlated negatively and decrease (Al2O3) respectively increase (MgO) from the top to the bottom.  相似文献   

11.
Batch acid addition experiments were carried out to determine the acid buffer capacities (amount of acid required to lower soil pH by one unit) of forest soils. Samples of O, E, B (or BC), and C horizons taken from 29 podzolic profiles in southern Finland were used in the experiments. Subsamples of soil were equilibrated for 24 h with NaCl solution containing additions of HCl acid. Cation exchange, mineral dissolution (weathering), and the protonation of organic matter all appeared to have been involved in the buffering of the acid additions. For the O horizon samples, most of the cations released in response to the acid additions were base cations. For the mineral soil samples, most of the cations released were Al3+ ions. With the exception of a few samples, the added acid was not fully neutralised and pH was lowered even with the lowest addition treatment. However, the acid addition treatments corresponded to many times the regional annual acid deposition load (1.6–2.0 cmol(c) m?2). Calculated acid buffer capacities (cmol(c) kg?1 pH?1) ranged from 9.8 to 40.8 for O horizon soil samples and from 0.1 (C horizon) to 5.2 (E horizon) for the mineral soil samples. Total acid buffer capacities for a profile (to a depth of 50 cm) ranged from 500 to 2349, with a mean value of 1091 cmol(c) m?2 pH?1. It is concluded that, in addition to CEC and base saturation, acid buffer capacity is a useful measure to describe the ecological effects of acid deposition on soil.  相似文献   

12.

Purpose

In this paper, an attempt was made to explain the long-lasting occurrence of atrazine in soil. Despite the fact that this herbicide has been banned in European Union 10 years ago, it is still detected in the environment.

Materials and methods

Soil samples (organic and mineral horizon), SiO2 and Al2O3 sorbents were spiked with atrazine. The ultrasound-assisted extraction coupled with gas chromatography-electron capture detector was performed to establish the atrazine recovery depending on the type of soil horizon and sorbent. Fourier transform infrared spectroscopy (FTIR) analysis was conducted to determine the type of interactions between atrazine and sorbents.

Results and discussion

The atrazine recovery was lower for the mineral horizon (15%) compared to the organic horizon (63%). This finding suggests an interaction between atrazine and the mineral components of soil. Therefore, attempts have been made to explain atrazine’s interaction with the main mineral components of soil, SiO2 and Al2O3, and to investigate the influence of pH on atrazine’s behaviour in soil. The atrazine recoveries were 86.5 and 10.7% for Al2O3 and SiO2, respectively. The obtained results demonstrated that the protonated atrazine exhibits stronger interactions with the soil mineral layer (recovery below 0.1%) in comparison to molecular form of atrazine (recovery 86%). FTIR results suggested interactions between atrazine and SiO2. FTIR analysis revealed that 1,3,5-azidine ring interacts with SiO2 molecule.

Conclusions

In acidic soil, atrazine remediation is limited, especially if the soil contains minerals with high SiO2 contents. This situation may cause the long-lasting persistence of atrazine in soil.
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13.
The potentiometric titration of water extracts from the upper horizons of taiga-zone soils by salt solutions of heavy metals (Pb, Cu, and Zn) showed that their addition is an additional source of the extract acidity because of the involvement of the metal ions in complexation with water-soluble organic substances (WSOSs). At the addition of 0.01 M water solutions of Al(NO3)3 to water extracts from soils, Al3+ ions are also involved in complexes with WSOSs, which is accompanied by stronger acidification of the extracts from the upper horizon of soddy soils (with a near-neutral reaction) than from the litter of bog-podzolic soil (with a strongly acid reaction). The effect of the Al3+ hydrolysis on the acidity of the extracts is insignificantly low in both cases. A quantitative relationship was revealed between the release of protons and the ratio of free Cu2+ ions to those complexed with WSOSs at the titration of water extracts from soils by a solution of copper salt.  相似文献   

14.
The coastal areas of SE Norway provide suitable conditions for studying soil development with time, because unweathered land surfaces have continuously been raised above sea level by glacio‐isostatic uplift since the termination of the last ice age. We investigated Podzol development in a chronosequence of six soils on sandy beach deposits with ages ranging from 2,300 to 9,650 y at the W coast of the Oslofjord. The climate in this area is rather mild with a mean annual temperature of 6°C and an annual precipitation of 975 mm (Sandefjord). The youngest soil showed no evidence of podzolization, while slight lightening of the A horizon of the second soil (3,800 years) indicated initial leaching of organic matter (OM). In the 4,300 y–old soil also Fe and humus accumulation in the B horizon were perceptible, but only the 6,600 y–old and older soils exhibited spodic horizons. Accumulation of OM in the A horizons reached a steady state in <2,300 y, while in the B horizons OM accumulated at increasing rates. pH dropped from 6.6 (H2O)/5.9 (KCl) in the recent beach sand to 4.5 (H2O)/3.8 (KCl) within approx. 4,500 y (pHH2O)/2,500 y (pHKCl) and stayed constant thereafter, which was attributed to sesquioxide buffering. Base saturation showed an exponential decrease with time. Progressive weathering was reflected by increasing Fed and Ald contents, and proceeding podzolization by increasing amounts of pyrophophate‐ and oxalate‐soluble Fe and Al with soil age. These increases could be best described for most Fe and Al fractions by exponential models. Only the increasing amounts of Fep could be better described by a power function and those of Feo by a linear model.  相似文献   

15.
Saturated hydraulic conductivity (Ks) is one of the soil properties used most often to predict soil behavior and suitability for a variety of uses. Because of the difficulty in Ks measurement and its variability with depth and across the landscape, Ks is commonly predicted from other more easily evaluated properties including texture, clay mineralogy, bulk density, pedogenic structure and cementation. Of these, texture and pedogenic structure are most commonly used to estimate Ks, but the reliability of these estimates has not been evaluated for common soils in the Southern Piedmont of Georgia. Thus, the objectives of this study were to evaluate Ks for major horizons in soils and landscapes in the Georgia Piedmont and to relate Ks to morphological properties of these horizons. Ten sites across the region were selected, and 21 pedons arranged in three transects were described from auger holes and pits. For each pedon, Ks was measured in upper Bt horizons, at 140 cm below the surface (Bt, BC, or C horizon), and at a depth intermediate between the shallow and deep measurements (Bt, BC, or C horizon) with a constant head permeameter. The Ks of individual horizons ranged from 1 × 10− 8 to 2 × 10− 5 m s− 1. At six of 10 sites evaluated, clayey upper Bt horizons had higher Ks than deeper horizons with less clay. This difference was attributed to weaker structure in the deeper BC horizons. Structural differences did not explain all variation in Ks with depth, however. Other soil and landscape properties including parent material composition, colluvium on lower slope positions, C horizon cementation, and depth of soil development also affected Ks of horizons in these soils and should be used to better estimate Ks.  相似文献   

16.
The macromorphology, micromorphology and chemical nature of illuvial material in podzol B horizons and subsoils can be explained by contributions from two different migrating species: (a) a positively-charged mixed Al2O3-Fe2O3-SiO2-H2O sol incorporating minor amounts of adsorbed organic matter and silicate clay, and (b) negatively charged organic sols and solutions, carrying minor amounts of Al, Fe and clay. These species can also be generated within B horizons of high root activity. An alternative theory, that requires allophane to be formed in situ in the B horizon by microbial decomposition of precipitated organic complexes, fails to predict the observed distribution of allophane.  相似文献   

17.
Iron, Al, and Mn were extracted by oxalate and dithionite from two Brown Mediterranean Soils, two Red Mediterranean Soils, one Vertisol and one Gley soil, all derived from basalt or scoria in the sub-humid and humid Mediterranean regions of the Golan Heights. Ratios of oxalate: dithionite extracted iron (Feo:Fed) were low in all soils, indicating that the predominant form of free iron is crystalline. Feo accumulates in the argillic B horizons of the Mediterranean soils, while Fed accumulates in the surface horizons. A large part of the free iron oxide in the surface horizons of Mediterranean soils is associated with non-clay fractions. While manganese behaves in a manner somewhat similar to that of iron, no definite trends could be discerned in the vertical distribution of free aluminium. In the Vertisol, Feo and Mno accumulate in the subsoil. Fed and Mnd increase slightly with soil depth. In the Gley soil, amorphous iron accumulates in the surface horizon, total free iron in the bottom horizon. Both amorphous and total free Mn had been depleted from the upper horizons of the Gley soil.  相似文献   

18.
Buried horizons and lenses in riparian soil profiles harbor large amounts of carbon relative to the surrounding soil horizons. Because these buried soil horizons, as well as deep surface horizons, frequently lie beneath the water table, their impact on nitrogen transport across the terrestrial–aquatic interface depends upon their frequency and spatial distribution, and upon the lability of associated organic matter. We collected samples of 51 soil horizons from 14 riparian zones Rhode Island, USA, where soil profiles are characterized by glacial outwash and alluvial deposits. These soil samples came from as deep as 2 m and ranged in carbon content from <1% to 44% in a buried O horizon 54–74 cm deep. We used these samples to: (1) determine the extent to which carbon in buried horizons, and deep surface horizons, is potentially microbially available; (2) identify spatial patterns of carbon mineralization associated with surface and buried horizons; and (3) evaluate likely relationships between soil horizon types, chemical characteristics and carbon mineralization. Carbon mineralization rates associated with buried horizons during anaerobic incubations ranged from 0.0001 to 0.0175 μmol C kg soil?1 s?1 and correlated positively with microbial biomass (R=0.89, P<0.0001, n=21). Excluding surface O horizons from the analysis, carbon mineralization varied systematically with horizon type (surface A, buried A, buried O, lenses, A/C, B, C) (P<0.05) but not with depth or depth x horizon interaction (overall R2=0.59, P<0.0005, n=47). In contrast to this result and to most published data sets, 13C-to-12C and 15N-to-14N ratios of organic matter declined with depth (13C?26.9 to ?29.3 per mil, 15N+5.6 to ?0.8 per mil). The absence of a relationship between horizon depth and C availability suggests that carbon availability in these buried horizons may be determined by the abundance and quality of organic matter at the time of horizon formation or burial, rather than by duration since burial, and implies that subsurface microbial activity is largely disconnected from surface ecosystems. Our results contribute to the emerging view that buried horizons harbor microbially available C in quantities relevant to ecosystem processes, and suggest that buried C-rich soil horizons need to be incorporated into assessments of the depth of the biologically active zone in near-stream subsurface soils.  相似文献   

19.
X-ray absorption near edge structure (XANES) spectra at the sulfur (S) K-edge (E=2472 eV) were compared for bulk soil material, humic and fulvic acid fractions, and different particle size separates from Ah horizons of two arable Luvisols, from an O and a Bs horizon of a Podzol under Norway spruce forest, and from an H horizon of a Histosol (peat bog). In the bulk soil samples, the contribution of reduced organic S (organic mono- and disulfides) to total sulfur increased from 27% to 52%, and the contribution of ester sulfate and SO42−-S decreased from 39% to 14% of total S in the following order: arable Luvisols Ah—forested Podzol O—Histosol H. This sequence reflects the increasing organic carbon content and the decreasing O2 availability in that order. Neither sulfonate nor inorganic sulfide was detected in any of the bulk soil samples. For all samples except the Podzol Bs, the XANES spectra of the bulk soils differed considerably from the spectra of the humic and acid fractions of the respective soils, with the latter containing less reduced S (16-44% of total S) and more oxidized S (sulfone S: 19-35%; ester sulfate S: 14-38% of total S). Also the S speciation of most particle size fractions extracted from the Ah horizon of the Viehhausen Luvisol and the Bs horizon of the Podzol was different from that of the bulk soil. For both soils, the contribution of oxidized S species to total S increased and the contribution of sulfoxides and organic mono- and disulfides decreased with decreasing particle size. Thus, sulfur K-edge XANES spectra of alkaline soil extracts, including humic and fulvic acids or of particle size separates are not representative for the S speciation of the original soil sample they are derived from. The differences can be attributed to (i) artificial changes of the sulfur speciation during alkaline extraction (conversion of reduced S into oxidized S, loss of SO42− during purification of the extracts by dialysis) or particle size separation (carry-over of water-soluble S, such as SO42−), but also to (ii) preferential enrichment of oxidized S in hydrophilic water-soluble soil organic matter (ester sulfate) and in the clay fraction of soils (ester sulfate, adsorbed SO42−).  相似文献   

20.
Aluminum concentrations in organoaluminum complexes, mineral polymers, Al(H2O) 6 3+ , Al(OH)(H2O) 5 2+ , Al(OH)2(H2O) 4 + , AlH3SiO 4 2+ , and Al(OH)3(H2O) 3 0 extracted with 0.001 M CaCl2 from the main genetic horizons of a podzolic soil on two-layered deposits were determined experimentally and calculated from thermodynamic equations. It was found that aluminum bound in organic complexes was predominant in extracts from the AE horizon, and mineral polymer aluminum compounds prevailed in extracts from the E and IIBD horizons. In the AE horizon, organoaluminum compounds were a major source of aluminum, which passed into solution predominantly by exchange reactions. In the E horizon, aluminum hydroxide interlayers in soil chlorites were the main source of aluminum, which passed into solution by dissolution reactions. In extracts from the IIBD horizon, aluminum was solubilized by the dissolution of aluminosilicates inherited from the parent rock.  相似文献   

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