高岭石,蒙脱石和针铁矿对泥炭腐殖酸的吸附和分离   总被引：6，自引：0，他引：6  

S. GHOSH  WANG Zhen-Yu  S. KANG  P. C. BHOWMIK  B. S. XING 《土壤圈》2009,19(1):21-30

Sorption of humic acid (HA) on mineral surfaces has a profound interest regarding the fate of hydrophobic organic contaminants (HOCs) and carbon sequestration in soils. The objective of our study is to determine the fractionation behavior of HA upon sorption on mineral surfaces with varying surface properties. HA was coated sequentially on kaolinite (1:1 clay), montmorillonite (2:1 clay), and goethite (iron oxide) for four times. The unadsorbed HA fractions were characterized by elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), and solid state ¹³C nuclear magnetic resonance spectroscopy (NMR). The mineral-HA complexes were characterized by DRIFT. Polarity index [(N+O)/C] revealed higher polarity of the unadsorbed HA fractions after coating on kaolinite, reflecting that relatively higher polarity fractions of HA remain unadsorbed. Sorption of aliphatic alcohol fraction along with carbohydrate was prominent on kaolinite surface. DRIFT results of the unadsorbed HA fractions indicated more sorption of aliphatic moieties on both kaolinite and montmorillonite. DRIFT results of the unadsorbed HA fractions after sorption on kaolinite and goethite showed the sorption of the proteinaceous fractions of HA. The HA fractions obtained after coating on goethite showed significant sorption of carboxylic moieties. The results mentioned above comply reasonably well with the DRIFT spectra of the mineral-HA complexes. ¹³C NMR results showed higher sorption of anomeric C on kaolinite surface. Higher sorption of paraffinic fraction was observed on montmorillonite. NMR data inferred the sorption of carboxylic moieties on goethite surface. Overall, this study showed that aliphatic moieties of HA preferentially sorbed on kaolinite and montmorillonite, while carboxylic functional groups play a significant role in sorption of HA on goethite. The sorbed fractions of HA may modify the mineral surface properties, and thus, the interaction with organic contaminants.  相似文献   

SORPTION OF INORGANIC PHOSPHATE BY IRON- AND ALUMINIUM- CONTAINING COMPONENTS   总被引：1，自引：0，他引：1  

J. R. McLAUGHLIN  J. C. RYDEN  J. K. SYERS 《European Journal of Soil Science》1981,32(3):365-378

The amounts of inorganic P sorbed by a range of Fe- and Al- containing components varied appreciably and decreased in the order allophane > fresh Al gel > Fe gel pseudoboehmite > aged Al gel > dried Fe gel > Fe-coated kaolinite > haematite > goethite > akaganeite > gibbsite = ground kaolinite > dispersed kaolinite. Al gel sorbed 30 to 70 times more P than gibbsite, and Fe gel sorbed approximately 10 times more P than its crystalline analogues (haematite, goethite. and akaganeite). Despite large differences in the extent of P sorption, the form of the isotherm was essentially the same for each sorbent. The ability of freshly-prepared Al gel suspensions to sorb P decreased with ageing, a property not shown by Fe gel. Drying of Fe gel at 80°C, however, caused an approximately 4-fold decrease in P sorption. Precipitation of Fe gel (2% Fe) on the surface of kaolinite increased P sorption by a factor of 10. The occurrence of Fe gel as a coating apparently presents more sorption sites to solution per unit weight of Fe gel than Fe gel alone. A linear relationship (r= 0.98) was obtained between the amount OH^? sorbed per unit increase in pH value (‘hydroxyl buffering’) and the overall P sorption maximum for each sorbent. Hydroxyl buffering provided a better index of P sorption potential than specific surface area. Except for the crystalline Fe sorbents, isotherms obtained by plotting fractional sorption saturation against final solution P concentration for the sorbents were essentially coincident with those for several contrasting soils. For crystalline Fe components a lower relative amount of weaker sorption, as opposed to chemisorption, of the overall sorption maximum was obtained. Differences in the extent of P sorption. however, appear to be primarily related to the number of functional M-OH groups presented at the solid-solution interface.  相似文献   

Surface loading effect on Cd and Zn sorption by kaolinite and montmorillonite from low concentration solutions     

J. García-Miragaya  R. Cardenas  A. Page 《Water, air, and soil pollution》1986,27(1-2):181-190

Studies of Cd and Zn sorption using Na-saturated kaolinite and montmorillonite, and low metal solution concentrations similar to those found in the environment, showed that metal sorption affinity (measured by K _d values) decreased markedly with increasing surface metal loading for both layer silicates. For equilibrium solution concentrations <0.1 μmol L^?1 for Cd, and < 1 μmol L^?1 for Zn, both metals were sorbed with greater affinity by kaolinite than montmorillonite. These results were probably due to the higher proportion of weakly acidic edge sites present on kaolinite surfaces. In the case of Zn there was an affinity reversal for equilibrium solution concentrations > 1 μmol L^?1, which was attributed to the permanent charge sites of montmorillonite. Cadmium ions were sorbed, by kaolinite, with greater affinity than Zn for equilibrium solution concentrations between 0.3 to 1.5 μmol L^?1. This result was attributed to retention of these metal ions through electrostatic attraction by permanent charge sites present on the kaolinite used in this work. According of these results it seems that metal sorption by these layer silicates involves predominantly edge weak acid sites at lower surface coverages (higher affinity sites), and permanent charge sites at higher metal coverages (lower affinity sites). It was concluded that Cd and Zn sorption by those two layer silicates is greatly influenced by surface metal coverage, and results cannot be extrapolated from low to high surface coverages, and viceversa.  相似文献   

DESORPTION AND ISOTOPIC EXCHANGE RELATIONSHIPS OF PHOSPHATE SORBED BY SOILS AND HYDROUS FERRIC OXIDE GEL   总被引：1，自引：0，他引：1  

J. C. RYDEN  J. K. SYERS 《European Journal of Soil Science》1977,28(4):596-609

Sorption of added inorganic phosphate (P) was irreversible in four contrasting soils and hydrous ferric oxide gel during 16 h desorption after 40 h sorption at the same (iso)pH. Irreversibility increased with increasing time of desorption above 30 h. When the amount of P which was chemisorbed during the sorption step was subtracted from the amount desorbed, the latter fell on the isotherm describing the more-physical, potential-determining sorption. No pH change occurred during desorption and net negative charge decreased by 1 equivalent per mole P desorbed. These results suggested that only more-physically sorbed P was desorbed at the iso-pH. The more-physically sorbed P was also reversible with respect to changes in the ionic strength and cation species of the desorbing solution. The isotopic exchangeability of the more-physically sorbed P was at least ten times greater than that of chemisorbed P. With increasing sorption time, both the ease of desorption and exchangeability of sorbed P decreased. Subsequent to desorption, the exchangeability of the remaining sorbed P also decreased. These observations are interpreted in terms of the concurrent changes in the amounts of chemisorbed and more-physically sorbed P.  相似文献   

Specific sorption of trace amounts of cadmium by soils     

《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   

Cadmium Sorption by Hydroxy-Aluminium Interlayered Montmorillonite     

Jobstmann  H.  Singh  Balwant 《Water, air, and soil pollution》2001,131(1-4):203-215

Cadmium sorption and desorption behaviour of hydroxy-Alinterlayered montmorillonite (pillared) was compared with unpillared montmorillonite. Characteristic properties of themontmorillonite, whose interlayer cations were replaced byhydroxy-Al polymers, are its thermal stability up to ～500 °C and increased surface area of about 300 × 10³ m² kg^-1. The cation exchange capacity was reduced by ～30% after interlayering withpositively charged hydroxy-Al polymers.Cadmium sorption data for the two montmorillonites fitted verywell (R² = 0.98 to 0.99) to the Freundlich equation. Inthe concentration range (0.89–17.79 μM Cd L^-1) used for the experiment, the unpillared montmorillonite sorbed moreCd than the pillared montmorillonite. Cadmium is possibly retained by electrostatic and chemisorption mechanisms by thepillared montmorillonite whereas electrostatic attraction ismainly responsible for Cd sorption by unpillared montmorillonite. After 5 extractions with 0.01 M NaNO₃the amount of Cd desorbed varied between 30–47 and 34–59% for unpillared and pillared montmorillonites, respectively. At lower concentrations of initially sorbed Cd, the amount ofCd desorbed was nearly equal for the two samples.  相似文献   

Assessing the fixation and availability of sorbed phosphate in soil using an isotopic exchange method   总被引：3，自引：0，他引：3  

Z. L. HE  K. N. YUAN  Z. X. ZHU  Q. Z. ZHANG 《European Journal of Soil Science》1991,42(4):661-669

An isotopic exchange method was used to characterize quantitatively the fixation and plant availability of phosphate previously sorbed by soils. In general, the exchangeability of the sorbed phosphate was much higher than its desorbability for both soils and clay minerals. Isotopic exchangeability of the sorbed phosphate increased with sorption saturation during the initial stage (15–60% saturation), but the increase was less with increasing saturation from 60–90% for all soils tested. Therefore a sorption saturation of 60% was recommended as the upper limit of P fertilization in terms of economical efficiency. For clay minerals, with increasing sorption saturation, the isotopic exchangeability of the sorbed P increased significantly for kaolinite and sesquioxides, but decreased for montmorillonite. Most of the phosphate sorbed by montmorillonite and kaolinite was found to be isotopically exchangeable, but only a small amount of the P sorbed by goethite could be exchanged. The P sorbed by Al oxide exhibited isotopic exchangeability between that of kaolinite and Fe oxide. The isotopically exchangeable phosphate pool could readily account for the P uptake of plants and the available P determined by some commonly used chemical methods, such as Olsen-P and Bray-P.  相似文献   

Kinetic behaviour of alkaline phosphatase desorbed from different clay minerals     

H. E. Makboul  J. C. G. Ottow 《植物养料与土壤学杂志》1984,147(4):497-501

The kinetic (K_m, V_max) of alkaline phosphatase (AP) desorbed from different Ca-homoionic clay minerals (montmorillonite, illite, and kaolinite) by extraction with Tris-Malate-Citrate buffer solution (pH 9.6) was studied in model experiments. After extraction (shaking for 15 min.) the K_m and V_max were measured in the extract, the remaining sediment and in the whole set-up. With kaolinite and illite, V_max of the desorbed AP was lower than that of the sediment. However, with montmorillonite, V_max of AP in the extract and whole system increased if compared to the control, but decreased in the sediment. The K_m of desorbed AP increased from 4.3 × 10^?3 (control) to 5.0 × 10^?3 M (illite), 5.4 × 10^?3M (kaolinite), and 5.5 × 10^?3M (montmorillonite). These values were lower than those obtained with the various sediments and whole experimental systems. An aberrant behaviour was recorded with the illite sorbed AP which showed an increase in affinity towards the substrate. Generally speaking, AP desorbed from clays may be reduced in its affinity towards the substrate p-nitrophenylphosphate by residual inhibitor and/or conformational change of the enzyme.  相似文献   

Sorption and desorption of cobalt by soils and soil components   总被引：2，自引：0，他引：2  

R. G. McLAREN  D. M. LAWSON  R. S. SWIFT 《European Journal of Soil Science》1986,37(3):413-426

The sorption of Co by individual soil components was studied at solution Co concentrations that were within the range found in natural soil solutions. Soil-derived oxide materials sorbed by far the greatest amounts of Co although substantial amounts were also sorbed by organic materials (humic and fulvic acids). Clay minerals and non-pedogenic iron and manganese oxides sorbed relatively little Co. It is considered that clay minerals are unlikely to have a significant influence on the sorption of Co by whole soils. Cobalt sorbed by soil oxide material was not readily desorbed back into solution and, in addition, rapidly became non-isotopically exchangeable with solution Co. In contrast, Co was relatively easily desorbed from humic acid and a large proportion of the Co sorbed by humic acid remained isotopically exchangeable. Cobalt sorbed by montmorillonite was more easily desorbed than that sorbed by soil oxide but less easily than that sorbed by humic acid. Cobalt sorption isotherms for whole soils at low site coverage were essentially linear and the gradients of isotherms increased with pH. A comparison of isotherm gradients for whole soils and individual soil components supported the suggestion that Co sorption in whole soils is largely controlled by soil oxide materials.  相似文献   

Zinc sorption–desorption by two Andepts: effect of pH and support medium     

M.T. PARDO  M.E. GUADALIX 《European Journal of Soil Science》1996,47(2):257-263

Laboratory experiments were carried out to evaluate the effect of pH, ionic strength and electrolyte composition on zinc sorption–desorption by two Andepts from the Canary Islands (Spain). At the natural soil pH, the soils exhibited little net negative surface charge and small Zn sorption capacities. More than 75% of the sorbed Zn was apparently strongly bonded. The pH greatly influenced the sorption–desorption reactions. Sorption increased with increasing pH, and retention increased abruptly at pH > 6.0. Sorption also occurred at pH values below the point of zero charge (PZC) of the soils, when most of the surface sites are positively charged. Desorption decreased continuously with rising pH and became a trace at pH > 6.0. An increase in the ionic strength of the background electrolyte decreased Zn sorption and enhanced the amount of sorbed metal that could be subsequently released. In the two soils, Zn sorption diminished somewhat in the K and Ca electrolytes as compared with the Na electrolyte. However, this did not happen at small Zn loadings. Desorption was not affected by the type of electrolyte and cation used. The results are consistent with chemisorption being responsible for most of the sorption. The results also suggested a strong affinity sorption or even precipitation at high pHs.  相似文献   

Interactive Sorption of Metal Ions and Humic Acids onto Mineral Particles     

Petrović  M.  Kaštelan-macan  M.  Horvat  A. J. M. 《Water, air, and soil pollution》1999,111(1-4):41-56

The sorption of metal ions (Pb2+, Zn2+ and Cu2+) and soil humic acids (HA) from aqueous solutions onto mineral particles (sand, calcite and clay) was investigated using a batch equilibrium system. The sorption reactions in two- component systems (heavy metals-mineral particles and humic acids- mineral particles), as well as interactions in three-component system (heavy metals-humic acids-mineral particles) were examined. Results showed that the presence of humic acids, dissolved or bound onto mineral surfaces, considerably influenced the fixation of heavy metals. The various effects, depending on mineral type, humic concentration and specific metal-ion, were observed in three- component system. Sorption of Cu2+-ions on all minerals studied rapidly increased as the concentration of dissolved HA increased. The amount of Pb2+-ions sorbed on sand slightly decreased, while on kaolin increased between 15 and 20%. Sorption of Zn2+-ions on all minerals studied decreased at pH 4. At pH 5.5 the sorption of Zn2+-ions onto calcite decreased, while on kaolin and sand increased as a function of the humic acid concentration giving the curve with maximum at c(HA) = 2.5 mmol C L-1. At pH 6.5 sorption onto kaolin and sand increased. This effect occurs as a result of the conditional stability constant of Zn-HA complexes increasing at higher pH which in turn promotes the chelation of Zn2+-ions to mineral- bound humic substances. The enhanced sorption of metal ions from the aqueous phase in three-component systems is not only the result of mineral sorption of free metals but also the result of chelation with HA sorbed on the mineral surface.  相似文献   

电解质种类和浓度影响磷酸根解吸的机理研究     

何振立  袁可能  朱祖祥 《土壤学报》1992,29(1):26-33

本文研究了吸附性阳离子、电解质浓度和组成影响几种矿物和土壤吸附态磷的解吸的机理。结果表明,吸附性阳离子影响磷酸根解吸与离子桥有关。桥接静电场愈强,被束缚磷的释放就愈困难。电解质阳离子对磷酸根解吸的影响则取决于其对表面负电荷的屏蔽效应。阳离子电价高,屏蔽作用大,磷解吸就少。电解质浓度影响吸附态磷的解吸主要与表面电位的变化有关。当pH>PZC值时,提高电解质浓度降低表面负电位,从而减少磷的吸附;当pH<PZC时,提高电解质浓度则降低表面正电位,促进磷的解吸。磷酸根解吸盐效应零点(P_PZSE)值一般都介于土壤或矿物样品吸附磷酸根前后测得的两个PZC值之间。不同浓度电解质溶液中磷解吸量之差与吸附层电位变化量(△ψ_x)呈正相关。  相似文献   

Sorption and desorption of diuron and norflurazon in Florida citrus soils     

Krishna N. Reddy  Megh Singh  Ashok K. Alva 《Water, air, and soil pollution》1992,64(3-4):487-494

The potential for surface and groundwater contamination of soil applied herbicides is partly dependent on soil properties. Sorption and desorption of diuron and norflurazon were studied in seven soils representative of the southern citrus-belt of Florida using the batch-equilibrium technique. Sorption of herbicides was influenced by soil properties. Sorption coefficients (K _d) ranged from 0.84 to 3.26 mL g^?1 for diuron and 0.63 to 2.20 mL g^?1 for norflurazon indicating weak to moderate binding of herbicides to soil. For norflurazon, K _dwas significantly related to organic C content, soil pH, and cation exchange capacity. For diuron, absence of a significant relationship between K _dand selected soil properties suggests that the soil properties other than those studied may play a role in determining sorption on these soils. Desorption studies showed that higher amounts of diuron and norflurazon was desorbed by water than by 0.5 M CaCl₂. An inverse relationship was apparent between herbicides sorbed and that which was desorbed among the soils studied. The soil which exhibited higher sorption had lower desorption and the soil which exhibited lower sorption had higher desorption.  相似文献   

Retention of cobalt by an oxisol in relation to the content of iron and manganese oxides     

《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   

On the reversibility of phosphate sorption by soils   总被引：4，自引：0，他引：4  

N. J. BARROW 《European Journal of Soil Science》1983,34(4):751-758

Sorption of phosphate was induced by incubating phosphate with samples of two soils. Both desorption and further sorption of phosphate were then measured on separate subsamples of the incubated soils. The effects of varying the amount of phosphate incubated with the soil and of period of desorption, or of further sorption, were measured on one soil; the effect of period of incubation was measured on the other. Plots of desorbed phosphate versus concentration were continuous with plots of newly sorbed phosphate versus concentration. Neither of these coincided with the plots of the original additions of phosphate. These results were compatible with a model for the reaction between soil and phosphate in which phosphate is initially adsorbed and subsequently diffuses beneath the adsorbing surfaces. Sorption is reversible in the sense that a continuous curve of sorbed and desorbed phosphate is obtained when these are measured in opposite directions by increasing, or decreasing, the solution concentration of phosphate. However, because dynamic processes are involved, an earlier position of a plot of sorbed phosphate against concentration is not retraced when the concentration is changed.  相似文献   

Sorption and desorption of Zn on Ca-Kaolinite     

J. García-miragaya  M. Dávalos 《Water, air, and soil pollution》1986,27(3-4):217-224

Experiments on Zn²⁺ sorption-desorption by Ca-kaolinite using a wide range of Zn²⁺ concentrations and two acid pH values allowed us to reach the following conclusions: (1) For Zn²⁺ surface coverages below the kaolinite C.E.C., Zn²⁺ was sorbed mainly via ion exchange; (2) At Zn^2? sorption values above the C.E.C., Zn²⁺ was sorbed with higher affinity by a mechanism stronger than ion exchange, involving a strong association of Zn ions with silicate solid phases; and (3) Use of C.E.C. values and/or Langmuir's calculated maxima would greatly underestimate Zn²⁺ sorption capacity by kaolinite, even at acid pH values.  相似文献   

Humic acid and biochar as specific sorbents of pesticides     

Irmina Ćwieląg-Piasecka  Agnieszka Medyńska-Juraszek  Maria Jerzykiewicz  Magdalena Dębicka  Jakub Bekier  Elżbieta Jamroz  Dorota Kawałko 《Journal of Soils and Sediments》2018,18(8):2692-2702

  相似文献   

Zinc sorption by acid tropical soils as affected by cultivation     

M.E. GUADALIX  M.T. PARDO 《European Journal of Soil Science》1995,46(2):317-322

The sorption of zinc (Zn) by two acid tropical soils, Mazowe clay loam (kaolinitic, coarse, Rhodic Kandiustalf) and Bulawayo clay loam (coarse, kaolinitic, Lithic Rodustalf), was studied over a wide range of Zn solution concentrations. Samples of the two soils used in the experiments were collected at both uncleared, uncultivated (virgin) sites and cultivated sites. The two virgin soils showed similar abilities to bind Zn. Mazowe soil (40 g organic matter kg^?1) presented the highest affinity for Zn. Yet, Bulawayo soil (23.5 g organic matter kg^?1) sorbed almost the same amount. Bulawayo soil had higher pH and Fe and Mn-oxide content than Mazowe soil. Once cultivated, the two soils behaved quite differently. After 50 years, Mazowe soil had lost 60% of its organic matter and effective cation exchange capacity (ECEC). In this soil, Zn sorption capacity had also been decreased by 60%. Clearing and 10 years under cultivation had affected neither the organic matter content nor the ECEC of Bulawayo soil. For this soil, Zn sorption was even higher in the cultivated soil, presumably due to an increase in the amount of Fe and Mn oxide from subsoiling. Zinc sorption was dependent upon pH, with retention dramatically increasing in the pH range 6–7. Sorption occurred at pH values below the point of zero charge (PZC), indicating that the sorption reaction can proceed even in the presence of electrostatic repulsion between the positively charged soil surface and the cation. In the two soils, the reversibility of the sorption reaction was very low. More than 90% of the sorbed Zn was apparently strongly bonded.  相似文献   

Adsorption of DNA on clay minerals and various colloidal particles from an Alfisol   总被引：2，自引：0，他引：2  

P. Cai  X. Zhang 《Soil biology & biochemistry》2006,38(3):471-476

Adsorption and desorption of salmon sperm DNA on four different colloidal fractions from Brown Soil and clay minerals were studied. The adsorption isotherms of DNA on the examined soil colloids and minerals conformed to the Langmuir equation. The amount of DNA adsorbed followed the order: montmorillonite?fine inorganic clay>fine organic clay>kaolinite>coarse inorganic clay>coarse organic clay. A marked decrease in the adsorption of DNA on organic clays and montmorillonite was observed with the increase of pH from 2.0 to 5.0. Negligible DNA was adsorbed by organic clays above pH 5.0. As for inorganic clays and kaolinite, a slow decrease in DNA adsorption was found with increasing pH from 2.0 to 9.0. The results implied that electrostatic interactions played a more important role in DNA adsorption on organic clays and montmorillonite. Magnesium ion was more efficient than sodium ion in promoting DNA adsorption on soil colloids and minerals. DNA molecules on soil colloids and minerals were desorbed by sequential washing with 10 mM Tris, 100 mM NaCl and 100 mM phosphate at pH 7.0. A percentage of 53.7-64.4% of adsorbed DNA on organic clays and montmorillonite was released, while only 10.7-15.2% of DNA on inorganic clays and kaolinite was desorbed by Tris and NaCl. The percent desorption of DNA from inorganic clays, organic clays, montmorillonite and kaolinite by phosphate was 39.7-42.2, 23.6-28.8, 29.7 and 11.4%, respectively. Data from this work indicated that fine clays dominate the amount of DNA adsorption and coarse clays play a more important role in the binding affinity of DNA in soil. Organic matter may not favor DNA adsorption in permanent-charge soil. The information obtained is of fundamental significance for the understanding of the ultimate fate of extracellular DNA in soil.  相似文献   

Effect of clay minerals on the activity of polysaccharide cleaving soil enzymes     

Werner Pflug 《植物养料与土壤学杂志》1982,145(5):493-502

Kinetic analyses of the influence of montmorillonite, palygorskite and kaolinite on the activity of three polysaccharide cleaving soil enzymes revealed an inhibitory effect that is rather due to the structure than to chemical characteristics of the clays. The fibrous palygorskite was found to be highly effective towards the starch cleaving α-amylase and amyloglucosidase, whereas the layer silicates caused only a slight inhibition. Interactions with cellulase were affected by sorption of cellulose by montmorillonite and kaolinite. When the enzyme was allowed to be sorbed by the clays before cellulose was added, a clay-enzyme complex is formed, which in contrast to the starch cleaving enzymes remains active. Compared to the native enzyme, the bound enzyme is not stabilized with respect to temperature, but the optimum pH is found to be at pH 6 instead of pH 4.8.  相似文献