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1.
《Communications in Soil Science and Plant Analysis》2012,43(5-6):785-798
Abstract The study aims at determining the cobalt retention properties of various soil components. Therefore, cobalt (Co) sorptions and extractions were carried out using an Oxisol sample before (untreated) and after successive removal of organic matter and active manganese (Mn) oxides (H2O2‐treated) and iron (Fe) oxides (H2O2+CBD‐treated). A synthetic goethite was included for comparison. Sorption of the four sorbents was determined over a range of Co concentrations (initially 10‐8 M to 10‐4 M), pH values (3 to 8) and reaction times (2 hours to 504 hours). The Co species sorbed was Co(ll), since oxygen exclusion during sorption had no effect on the amount sorbed. The pH‐dependent sorption curve (sorption edge) was shifted to lower pH at decreasing initial Co concentration and increasing reaction time. The displacements, in particular of the sorption edges corresponding to the lowest initial Co concentrations, to successively higher pH following removal of Mn oxides, organic matter and Fe oxides could be attributed to sorption onto sites of decreasing Co affinity [Mn oxides (and organic matter) > Fe oxides > kaolinite]. Extractions of sorbed Co at pH 5.5–7.5 with 2 M HCI showed that the extractability decreased with increasing sorption time and decreasing initial Co concentration. The untreated and H2O2‐treated soil samples retained sorbed Co at least as firmly as the synthetic goethite, whereas the H2O2+CBD‐treated sample (kaolinite) was clearly less effective. The results emphasized the importance of the soil Mn and Fe oxides for Co retention in soils but also the necessity of taken interior sorption sites into consideration. 相似文献
2.
The dependency of the retention of dissolved organic carbon (DOC) on mineral phase properties in soils remains uncertain especially at neutral pH. To specifically elucidate the role of mineral surfaces and pedogenic oxides for DOC retention at pH 7, we sorbed DOC to bulk soil (illitic surface soils of a toposequence) and corresponding clay fraction (< 2 μm) samples after the removal of organic matter and after removal of organic matter and pedogenic oxides. The DOC retention was related to the content of dithionite‐extractable iron, specific surface area (SSA, BET‐N2 method) and cation exchange capacity (pH 7). The reversibility of DOC sorption was determined by a desorption experiment. All samples sorbed 20–40 % of the DOC added. The DOC sorption of the clay fractions explained the total sorption of the bulk soils. None of the mineral phase properties investigated was able to solely explain the DOC retention. A sorption of 9 to 24 μg DOC m–2 indicated that DOC interacted only with a fraction of the mineral surface, since loadings above 500 μg m–2 would be expected for a carbon monolayer. Under the experimental conditions used, the surface of the silicate clay minerals seemed to be more important for the DOC sorption than the surface of the iron oxides. The desorption experiment removed 11 to 31 % of the DOC sorbed. Most of the DOC was strongly sorbed. 相似文献
3.
《Communications in Soil Science and Plant Analysis》2012,43(17-18):2367-2381
Abstract The extractant Mehlich‐1 is routinely used in Brazil for determination of soil nutrients, whereas Mehlich‐3 has been suggested as a promising extractor for soil fertility evaluation. Both were used for extraction of molybdenum (Mo) in Brazilian soils with Mo dosage by the KI+H2O2 method. The Langmuir and Freundlich isotherms were used to study soil Mo adsorption. Mehlich‐1 extracted more Mo than Mehlich‐3 in soils with high contents of organic matter, clay, and iron (Fe) oxides. Mehlich‐3 and Mehlich‐1 extractions correlated positively and significantly with amorphous Fe oxides, crystalline Fe oxides, and organic matter. Molybdenum recovering rates correlated to crystalline Fe oxides and clay contents but not to organic matter, pH, and Mo adsorption capacity. Amorphous and crystalline Fe oxides, clay, and organic matter were responsible for most of the Mo adsorption. The Langmuir isotherm described better the Mo adsorption to soil amorphous Fe oxides and organic matter than the Freundlich isotherm. 相似文献
4.
The adsorption of the toxin from Bacillus thuringiensis (Bt‐toxin), which is synthesized in genetically modified maize, on sterilized Na‐montmorillonite and on H2O2‐treated and untreated clay fractions of three soils from different sites were studied. All adsorption isotherms can be described by a linear isotherm. Although all clay fractions from the different soils show nearly the same mineralogical composition, we found different affinities ranging from k = 47.7 to k = 366.7 of the adsorbates for the Bt‐toxin. The H2O2‐treated clay fractions show no correlation between the adsorption affinity and the amount of soil organic matter. On the other hand, there is a correlation between the content of organic carbon and the adsorption affinity of the untreated clay fractions. This can be explained by the fact that due to the coatings of soil organic matter on aggregates, the Bt‐toxin polymers are not able to adsorb within the clay aggregates. 相似文献
5.
《Communications in Soil Science and Plant Analysis》2012,43(11-12):939-948
Abstract The importance of various soil components on copper (Cu) retention by Spodosois was investigated. Copper sorption and extraction were conducted on samples from the B horizon from six Danish Spodosois. The investigation was conducted on untreated samples, on hydrogen peroxide‐treated samples (to remove organic matter), on oxalate‐treated samples [to remove amorphous to poorly crystalline aluminum (Al) and iron (Fe) oxides], on hydroxylamine‐treated samples [to remove manganese (Mn) oxides]. Subfractions treated with hydrogen peroxide (H2O2) were further treated with oxalate and citrate‐bicarbonate‐dithionite (CBD). Sorption of Cu from an initial 10‐6 M solution after 48 hours was determined in the pH range 3 to 7 using 0.1M sodium nitrate (NaNO3) as the background electrolyte. The pH‐dependent sorption curve (sorption edge) was shifted to a higher pH with decreasing Al oxide content in the soils, and for the treated sample after removal of organic matter and Al and Fe oxides. A negligible effect was seen after removal of the Mn oxides because of their low abundance. Extraction of sorbed Cu at pH 4 to 6 with 0.1M nitric acid (HNO3) for 24 hours confirmed the sorption results, in inasmuch as removal of the Al (and Fe) oxides increased Cu extractability. Therefore, it was concluded that in the soils investigated, Cu retention is mainly determined by the oxalate‐extractable Al fraction with a minor contribution due to crystalline Fe oxides. 相似文献
6.
7.
《Communications in Soil Science and Plant Analysis》2012,43(19-20):2887-2905
Abstract To evaluate contributions of organic matter, oxides, and clay fraction to copper (Cu) adsorption in six characterized soils, adsorption isotherms and distribution coefficients were obtained by a batch experimental method. Copper adsorption isotherms from untreated soil, organic matter removed from samples, and organic‐matter‐ and oxide‐removed samples were compared with curve patterns and correlated to Langmuir and Freundlich models. Copper sorption data on untreated soils described L or H‐curves, whereas in soils deprived of any component, their curves were S‐type. Distribution coefficients allowed knowing Cu adsorption capacity of untreated soil and of organic matter, oxides, and clay fraction. Soil organic matter is the main component that affects Cu adsorption as long as soil pH is near neutrality. At acid pH, oxides are the main component that affects Cu adsorption, although to a much smaller extent than organic matter near neutral conditions. Soil pH is the main soil factor that determines Cu adsorption. 相似文献
8.
V. S. Anisimov I. V. Kochetkov S. V. Kruglov R. M. Aleksakhin 《Eurasian Soil Science》2011,44(6):618-627
The sorption and ion-exchange behavior of Co(II) and Zn in the soil-equilibrium solution system was studied for different
types and varieties of native soils and their clay fractions before and after mild oxidation with H2O2 to remove the organic carbon. The parameters of the ion-exchange adsorption and the selectivity coefficients of the (Co(II),
Zn)/Ca ion exchange were determined using different models for describing the relationship between the dissolved and sorbed
forms of the metals. These were the empirical Langmuir and Freundlich adsorption isotherms and the model of the ion-exchange
adsorption based on the acting mass law. It was found that the soil organic matter played an important role in the selectivity
of the ion-exchange adsorption of Co(II) and Zn by the soils and their clay fractions. This was confirmed by an abrupt decrease
(to almost 1) of the selectivity coefficients of the Co2+/Ca2+ and Zn2+/Ca2+ exchange after the treatment of the clay fraction with hydrogen peroxide. 相似文献
9.
《Communications in Soil Science and Plant Analysis》2012,43(19-20):3379-3391
Abstract The influence of soil organic matter on selenite sorption was investigated in the selenite adsorption capacity and the surface particle charge change by ligand exchange reaction using the hydrogen peroxide (H2O2) treatment and the ignition treatment of two Andosols. The removal of organic carbon (C) in soils accelerated selenite sorption, implying that organic matter of soils had negative influence on the selenite adsorption on the soils. Positive charge decrease on soil particles, concomitant proton consumption, and release of silicon (Si), sulfate (SO4 2‐), and organic C were observed in selenite sorption by the soils. The development of surface particle negative charge with selenite sorption was smaller in the H2O2‐treated soil than in the original soils and was scarcely observed in the ignition‐treated soil. It can be assumed that the increase of negative charge by selenite sorption was attributed to new negative sites borne by released insoluble organic matter and negative charge development directly by selenite sorption was small. 相似文献
10.
《Communications in Soil Science and Plant Analysis》2012,43(12):1157-1166
Abstract Sorption of trace quantities of Cd in four soils of different chemical and mineralogical properties, was studied. Initial Cd concentrations were between 15 to 150 μg. 1?1. The sorption isotherms were linear and had a positive intercept in three of the soils, indicating a constant partition‐high affinity sorption isotherm (Giles et. al6). The data also followed the Freundlich sorption isotherm, and the Freundlich K parameter was taken as a measure of the relative affinity of the different soils for the Cd metal sorbed. Cadmium sorbed was extracted by IN‐NH4C1 followed by 0.1N HC1, and the fraction remaining in the soils was considered specifically sorbed Cd. This fraction also followed a linear sorption isotherm, and was around 30% for the four soils studied. The sorption order for the amount of specifically sorbed Cd showed that the Boomer soil (kaolinite‐iron oxides) had the lowest affinity for specific sorption of this metal. This was taken as evidence that kaolinite and iron oxides have a lower capacity for retaining cadmium through specific sorption mechanism(s) than the materials present on the other soils (2:1 layer silicates and humic substances). The existence of specific mecha‐nism(s) responsible by the sorption of trace quantities of Cd in soil solutions has important implications on soil‐plant relationships, Cd mobility in soil profiles and control of Cd activity in soil solutions. 相似文献
11.
Organo-mineral associations in sandy acid forest soils: importance of specific surface area, iron oxides and micropores 总被引:2,自引:0,他引:2
Organo-mineral associations stabilize soil organic matter, though the mechanisms by which they do so are unclear. We used particle-size fractions < 6.3 μm of two soils to examine the importance of Fe oxides, short-range order Al silicates and the surface areas of minerals and micropores on the formation of organo-mineral associations. In the subsoil Fe oxides were most strongly statistically correlated with the mineral-bound organic carbon. We therefore assume that they are the most important substrates for the formation of organo-mineral associations. There is no indication that this is caused by physical protection of organic matter in their micropores (< 2 nm). In the Haplic Podzol, dithionite–citrate–bicarbonate-soluble short-range order Al silicates may also play a role. Fe oxide particles were calculated to offer specific surface areas of ∼ 200 m2 g−1 (goethite) and ∼ 800 m2 g−1 (ferrihydrite), corresponding to crystal diameters of only a few nm. We assume that the resulting large amount of oxide-specific reactive surface sites (conditionally charged hydroxyl groups) is responsible for their dominant role as sorbents. With maximum C loadings of 1.3 mg C per m2 Fe oxide for the Dystric Cambisol and 1.1 mg C per m2 Fe oxide + short-range order Al silicates for the Haplic Podzol the subsoils of both soils seem to have reached saturation with respect to organic matter sorption. In contrast to subsoil horizons, organo-mineral associations from topsoils contain much larger amounts of organic matter. Here a larger C loading on Fe oxides or a greater importance of other sorbents in addition to the oxides must be assumed. 相似文献
12.
《Communications in Soil Science and Plant Analysis》2012,43(7-8):805-816
Abstract Soils have substantial capacity for sorption of sulfur dioxide (SO2) but little is known about the nature of the sorbed S. Three surface soils varying in pH, organic matter, CaCO3 equivalent and surface area were exposed to air containing 5% SO2 and subsequently analyzed by ten different procedures to characterize the sorbed S. Most of the sulfur retained by soils after exposure to SO2 could be recovered as CaCl2‐extractable S, Ca(H2PO4)2‐extractable S, or S released as H2S by hydriodic acid (HI). Only small amounts of sulfur could be recovered as tetrachloromercurate (TCM)‐extractable S, S released as SO2 by HCl, or S released as H2S by HCl + Zn, HCl + Sn, or Raney Ni and NaOH. However, large amounts of S released as SO2 by HCl were recovered from the air‐dry Webster and the moist Storden soils indicating that SO2 sorption is influenced by organic matter in air‐dry soils and by CaCO3 in moist soils. 相似文献
13.
The influence of the soil mineral phase on organic matter storage was studied in loess derived surface soils of Central Germany. The seven soils were developed to different genetic stages. The carbon content of the bulk soils ranged from 8.7 to 19.7 g kg—1. Clay mineralogy was confirmed to be constant, with illite contents > 80 %. Both, specific surface area (SSA, BET‐N2‐method) and cation exchange capacity (CEC) of bulk soils after carbon removal were better predictors of carbon content than clay content or dithionite‐extractable iron. SSA explained 55 % and CEC 54 % of the variation in carbon content. The carbon loadings of the soils were between 0.57 and 1.06 mg C m—2, and therefore in the ”︁monolayer equivalent” (ME) level. The increase in SSA after carbon removal (ΔSSA) was significantly and positively related to carbon content (r2 = 0.77). Together with CEC of carbon‐free samples, ΔSSA explained 90 % of the variation in carbon content. Clay (< 2 μm) and fine silt fractions (2—6.3 μm) contained 68—82 % of the bulk soil organic carbon. A significantly positive relationship between carbon content in the clay fraction and in the bulk soil was observed (r2 = 0.95). The carbon pools of the clay and fine silt fractions were characterized by differences in C/N ratio, δ13C ratio, and enrichment factors for carbon and nitrogen. Organic matter in clay fractions seems to be more altered by microbes than organic matter in fine silt fractions. The results imply that organic matter accumulates in the fractions of smallest size and highest surface area, apparently intimately associated with the mineral phase. The amount of cations adhering to the mineral surface and the size of a certain and specific part of the surface area (ΔSSA) are the mineral phase properties which affect the content of the organic carbon in loess derived arable surface soils in Central Germany most. There is no monolayer of organic matter on the soil surfaces even if carbon loadings are in the ME level. 相似文献
14.
Air-dry and moist soils were shown to possess the capacity to sorb substantial amounts of (75Se)dimethylselenide produced by the yeast Candida humicola in culture, or by soil supplied with (75Se)selenite, depending largely upon the organic matter content and selenium concentration of the soils. The sorption capacities of individual soil constituents followed the order; organic matter > clay minerals > manganese oxides > iron oxides > acid-washed sand.A chemical fractionation procedure applied to soils fumigated with (75Se)dimethylselenide revealed that the majority of the selenium sorbed was converted after 1 month to other forms, extractable mainly with strong acid solutions. Experiments with sterilized (autoclaved and γ-irradiated) soils indicated that soil microorganisms played little, if any, part in the sorption process.The work reported here indicates that soil is an important natural “sink” for atmospheric dimethylselenide. 相似文献
15.
The relationship and mechanisms among weathering processes, cation fluxes, clay mineralogy, organic matter composition and stability were studied in soils developing on basaltic material in southern Italy (Sicily). The soils were transitions between Phaeozems and Vertisols. Intense losses of the elements Na, Ca and Mg were measured indicating that weathering has occurred over a long period of time. The main weathering processes followed the sequence: amphibole, mica, volcanic glass or if ash was the primary source → smectite → interstratified smectite–kaolinite → kaolinite. Kaolinite formation was strongly related to high Al, Mg and Na losses. The good correlation between oxyhydroxides and kaolinite in the soils suggests that (macro)aggregates have formed due to physical or electrostatic interactions between the 1:1 clay minerals and oxides. The stability of organic matter was investigated with a H2O2-treatment that assumes that chemical oxidation mimics the natural oxidative processes. The ratio of C after the H2O2 treatment to the total organic C ranged from 1–28%. No correlation between clay content and organic matter (labile or stable fraction) was found. The refractory organic fraction was enriched in aliphatic compounds and did not greatly interact with the kaolinite, smectite or poorly crystalline Fe or Al phases. A part of this fraction (most probably proteins) was bound to crystalline Fe-oxides. In contrast, the oxidisable fraction showed a strong relationship with poorly crystalline oxyhydroxides and kaolinite. Surprisingly, smectite did not contribute to the stabilisation of any of the organic C fractions. The stabilisation of organic matter in the soils has, therefore, two main mechanisms: 1) the protection of labile (oxidisable with H2O2) organic matter, including also aromatic-rich compounds such as charcoal, by the formation of aggregates with oxyhydroxides and kaolinite and 2) the formation of a refractory fraction enriched in aliphatic compounds. 相似文献
16.
About the sorption of dissolved organic matter to forest soils This investigation characterizes the major forest soils of the temperate climatic zones (leptosols, vertisols, cambisols, luvisols, podzols, stagnosols, gleysols) as sorbents for dissolved organic matter (DOM). Sorption isotherms were obtained for 135 soil horizons from 36 profiles. When solutions containing no DOC were added, the release of dissolved organic carbon (DOC) was highest for horizons rich in organic C (A and Bh horizons). In subsoil horizons DOC release was much lower. Most of the investigated top soils (A and E horizons) and Bh, Bg, and C horizons showed a weak DOC sorption. This was caused by low contents of sorbents (clay and sesquioxides) and/or high contents of organic C. Organic C seems to reduce the DOC sorption by occupying binding sites. Subsoils rich in clay and sesquioxides like Bs, Bt, and Bw horizons showed a strong retention of DOC. Under the aerobic conditions of the experiments, some of the subsoils of stagnosols and gleysols also showed a strong sorption of DOC. However, in sorption experiments conducted after an anaerobic incubation, the DOC sorption decreased significantly. 相似文献
17.
Clay addition to light-textured soils is used to ameliorate water repellency and to increase nutrient retention. However, clay addition may also increase the potential to bind organic matter and thus C sequestration. Divalent calcium ions (Ca2+) play an important role in binding of organic matter to clay because they provide the bridge between the clay particles and organic matter which are both negatively charged. In the first experiment, quartz sand was mixed with clay isolated from a Vertosol at rates of 0, 50 and 300 g kg-1, finely ground mature wheat residues (20 g kg-1) and powdered CaSO4 at 0, 5 and 10 g kg-1. Soil respiration was measured over 28 d. Compared to the sand alone, addition of isolated clay at 300 g kg-1 increased cumulative respiration with a stronger increase than that at 50 g kg-1. Addition of CaSO4 increased electrical conductivity, decreased sodium adsorption ratio and reduced cumulative respiration. The latter can be explained by enhanced sorption of organic matter to clay via Ca2+ bridges. In a second experiment, isolated clay or subsoil of the Vertosol without or with powdered CaSO4 at 10 g kg-1 were used for a batch sorption with water-extractable organic C (WEOC) from wheat straw followed by desorption with water. Addition of 10 g kg-1 CaSO4 increased sorption and decreased desorption of WEOC in both subsoil and isolated clay. In the third experiment, subsoil of the Vertosol was used for a batch sorption in which WEOC was added repeatedly. Repeated addition of WEOC increased the concentration of sorbed C but decreased the sorbed proportion of the added WEOC. This indicates that sorption of WEOC may be underestimated if it is added only once in batch sorption experaments. 相似文献
18.
Mixtures of the dipolar organic solvents formic acid (FA) and dimethyl sulphoxide (DMSO) were used to extract organic matter from soils. At 100 °C optimum extraction from a calcareous clay loam was with 80/20 v/v FA/DMSO, corresponding to a maximum in dielectric constant. Extraction of seven soils with boiling FA/H, O (107 °C) and FA/DMSO (112 °C) indicated that similar amounts of C and N are generally dissolved by the two solvent mixtures. However, FA/DMSO was about twice as efficient as FA/H2O for the ver-miculite-rich, calcareous, organic clay loam, removing 66 per cent of its C and 54 per cent of its N. Zr(IV) hydroxide in acidic aqueous acetone was a better flocculant than Ti(IV) for the dissolved organic matter. Model compound studies, together with hydrolytic and NMR studies, indicated that Zr precipitates carbohydrate-like but not aromatic organic components. The quantity of Zr sorbed to the organic matter corresponds closely with its C.E.C. determined by Ba retention. 相似文献
19.
《植物养料与土壤学杂志》2017,180(3):347-354
Soil particle size distribution (PSD), particularly the active clay fraction, mediates soil engineering, agronomic and environmental functions. The tedious and costly nature of traditional methods of determining PSD prompted the development of water sorption‐based models for determining the clay fraction. The applicability of such models to semi‐arid soils with significant amounts of calcium carbonate and/or gypsum is unknown. The objective of this study was to validate three water sorption‐based clay prediction models for 30 calcareous soils from Iran and identify the effect of CaCO3 on prediction accuracy. The soils had clay content ranging from 9 to 61% and CaCO3 from 24 to 97%. The three water sorption models considered showed a reasonably fair prediction of the clay content from water sorption at 28% relative humidity (RMSE and ME values ranging from 10.6 to 12.1 and −8.1 to −4.2, respectively). The model that considers hysteresis had better prediction accuracy than the other two that do not. Moreover, the prediction errors of all three models arose from under‐prediction of the clay content. The amount of hygroscopic water scaled by clay content decreased with increasing CaCO3 content. The low organic carbon content of the soils and the low fraction of low‐activity clay minerals like kaolinite suggested that the clay content under‐predictions were due to large CaCO3 contents. Thus, for such water‐sorption based models to work accurately for calcareous soils, a correction factor that considers the reduction of water content due to large CaCO3 content should be included. 相似文献
20.
《Communications in Soil Science and Plant Analysis》2012,43(17-18):2461-2487
Abstract Copper (Cu) is bound strongly to organic matter, oxides of iron (Fe) and manganese (Mn), and clay minerals in soils. To investigate the relative contribution of different soil components in the sorption of Cu, sorption was measured after the removal of various other soil components; organic matter and aluminum (Al) and Fe oxides are important in Cu adsorption. Both adsorption and desorption of Cu at various pH values were also measured by using diverse pasture soils. The differences in the sorption of Cu between the soils are attributed to the differences in the chemical characteristics of the soils. Copper sorption, as measured by the Freundlich equation sorption constants [potassium (K) and nitrogen (N)], was strongly correlated with soil properties, such as silt content, organic carbon, and soil pH. The relative importance of organic matter and oxides on Cu adsorption decreased and increased, respectively, with increasing solution Cu concentrations. In all soils, Cu sorption increased with increasing pH, but the solution Cu concentration decreased with increasing soil pH. The cumulative amounts of native and added soil Cu desorbed from two contrasting soils (Manawatu and Ngamoka) during desorption periods showed that the differences in the desorbability of Cu were a result of differences in the physico‐chemical properties of the soil matrix. This finding suggests that soil organic matter complexes of Cu added through fertilizer, resulted in decreased desorption. The proportions of added Cu desorbed during 10 desorption periods were low, ranging from 2.5% in the 24‐h to 6% in the 2‐h desorption periods. The desorption of Cu decreased with increasing soil pH. The irreversible retention of Cu might be the result of complex formation with Cu at high pH. 相似文献