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  • Online Resource  (6)
  • 2005-2009  (6)
  • 2006  (6)
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  • Online Resource  (6)
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  • 2005-2009  (6)
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  • 2006  (6)
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  • 1
    Online Resource
    Online Resource
    Stabilization of Organic Matter at Micropores (〈2 nm) in Acid Forest Subsoils
    Wiley ; 2006
    In:  Soil Science Society of America Journal Vol. 70, No. 6 ( 2006-11), p. 2049-2056
    Details
    In: Soil Science Society of America Journal, Wiley, Vol. 70, No. 6 ( 2006-11), p. 2049-2056
    Abstract: Binding of soil organic matter (OM) at micropore entrances within small mesopores (2–10 nm) has been suggested as a potential mechanism for the stabilization of OM against biodegradation. We hypothesized that the mineral‐associated fraction of stable OM [OM resisting treatment with 6% sodium hypochlorite (NaOCl) and subsequently extracted by 10% hydrofluoric acid] is associated with pores 〈 10 nm in 12 acid subsoil horizons. To study the coverage of micropores by stable OM sorbed in mesopores, we assumed that most micropores have entrances of mesopore size. We compared the accessibility of CO 2 at 273 K to micropores after NaOCl treatment with that of N 2 at 77 K. In contrast to N 2 , diffusion of CO 2 into micropores is little affected by OM and the difference in both micropore volumes (MIV) is taken as a measure of micropore clogging and thus of the association of stable OM with mesopores. The MIV measured by CO 2 adsorption was corrected for CO 2 sorption in OM (MIV‐CO 2 corr ). In 7 out of 12 samples, the MIV‐CO 2 corr equaled the MIV‐N 2 , suggesting that micropore entrances are not blocked by stable OM. For four samples the results were ambiguous, whereas in an Eutric Hapludand Bw horizon, a threefold larger MIV‐CO 2 corr compared with the MIV‐N 2 indicates that stable OM was associated with pores 〈 10 nm. Based on the findings that (i) mineral MIVs derived from CO 2 and N 2 adsorption were similar for most samples after exposure to NaOCl, (ii) the change of MIV‐N 2 on NaOCl treatment was small in all samples, and (iii) no relationship existed of the MIV‐CO 2 corr and small mesopore volume with the content of mineral‐associated stable organic C (OC), we conclude that the association of OM with micropore entrances in small mesopores does not primarily control the stabilization of OM in these acid subsoils.
    Type of Medium: Online Resource
    ISSN: 0361-5995 , 1435-0661
    URL: Article
    DOI: 10.2136/sssaj2005.0366N
    RVK:
    RA 4845
    Language: English
    Publisher: Wiley
    Publication Date: 2006
    detail.hit.zdb_id: 241415-6
    detail.hit.zdb_id: 2239747-4
    detail.hit.zdb_id: 196788-5
    detail.hit.zdb_id: 1481691-X
    SSG: 13
    SSG: 21
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  • 2
    Online Resource
    Online Resource
    Phosphate Desorption from Goethite in the Presence of Galacturonate, Polygalacturonate, and Maize Mucigel ( Zea mays L.)
    Wiley ; 2006
    In:  Soil Science Society of America Journal Vol. 70, No. 5 ( 2006-09), p. 1731-1740
    Details
    In: Soil Science Society of America Journal, Wiley, Vol. 70, No. 5 ( 2006-09), p. 1731-1740
    Abstract: Uronates are important constituents of maize mucilage and polyuronates are used as a simplified model of the soil–root interface. We tested whether galacturonate (GA) and polygalacturonate (PGA) impair the diffusion of phosphate (PO 4 ) into and out of pores of a synthetic goethite (147 m 2 g −1 ) and whether the effect of maize mucigel (MU) is comparable to PGA. We measured the PO 4 desorption kinetics of goethites in batch experiments over 2 wk at pH 5. One part of the goethite was equilibrated with organic substances before PO 4 addition, another part after addition of PO 4 Before the desorption experiments, the porosity of our samples was analyzed by N 2 gas adsorption. In each treatment a rapid initial desorption was followed by a slow desorption reaction, which is assigned to the diffusion of PO 4 out of mineral pores. No consistent relation between the micro‐ and mesoporosity and the rate of the slow PO 4 desorption was observed. Compared with the C‐free control, only PGA and MU affected the fraction of PO 4 mobilized by the fast and slow desorption reaction: when PGA was sorbed to goethite before PO 4 , twice as much PO 4 was mobilized via the fast reaction than in the treatment where PO 4 was sorbed before PGA, suggesting a decreased accessibility of goethite pores to PO 4 Mucigel, however, showed reversed effects, which is ascribed to its differing chemical composition. In conclusion, PGA seems inappropriate as a model substance for maize MU collected from non‐axenic sand cultures. Under the experimental conditions chosen, the efficacy of all organic substances to increase PO 4 solution concentrations by pore clogging and sorption competition is small.
    Type of Medium: Online Resource
    ISSN: 0361-5995 , 1435-0661
    URL: Article
    DOI: 10.2136/sssaj2005.0414
    RVK:
    RA 4845
    Language: English
    Publisher: Wiley
    Publication Date: 2006
    detail.hit.zdb_id: 241415-6
    detail.hit.zdb_id: 2239747-4
    detail.hit.zdb_id: 196788-5
    detail.hit.zdb_id: 1481691-X
    SSG: 13
    SSG: 21
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  • 3
    Online Resource
    Online Resource
    Citrate impairs the micropore diffusion of phosphate into pure and C-coated goethite
    Elsevier BV ; 2006
    In:  Geochimica et Cosmochimica Acta Vol. 70, No. 3 ( 2006-2), p. 595-607
    Details
    In: Geochimica et Cosmochimica Acta, Elsevier BV, Vol. 70, No. 3 ( 2006-2), p. 595-607
    Type of Medium: Online Resource
    ISSN: 0016-7037
    URL: Article
    DOI: 10.1016/j.gca.2005.10.032
    RVK:
    TE 1000
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2006
    detail.hit.zdb_id: 300305-X
    detail.hit.zdb_id: 1483679-8
    SSG: 13
    SSG: 16,12
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  • 4
    Online Resource
    Online Resource
    Restructuring of polygalacturonate on alumina upon hydration—Effect on phosphate sorption kinetics
    Elsevier BV ; 2006
    In:  Geochimica et Cosmochimica Acta Vol. 70, No. 12 ( 2006-6), p. 2957-2969
    Details
    In: Geochimica et Cosmochimica Acta, Elsevier BV, Vol. 70, No. 12 ( 2006-6), p. 2957-2969
    Type of Medium: Online Resource
    ISSN: 0016-7037
    URL: Article
    DOI: 10.1016/j.gca.2006.03.007
    RVK:
    TE 1000
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2006
    detail.hit.zdb_id: 300305-X
    detail.hit.zdb_id: 1483679-8
    SSG: 13
    SSG: 16,12
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  • 5
    Online Resource
    Online Resource
    Acid Polysaccharide Coatings on Microporous Goethites : Controls of Slow Phosphate Sorption
    Wiley ; 2006
    In:  Soil Science Society of America Journal Vol. 70, No. 5 ( 2006-09), p. 1547-1555
    Details
    In: Soil Science Society of America Journal, Wiley, Vol. 70, No. 5 ( 2006-09), p. 1547-1555
    Abstract: Organic coatings on Fe oxides can decrease the accessibility of intraparticle pores for oxyanions like phosphate. We hypothesized that the slow sorption of phosphate to goethite coated with polygalacturonate (PGA) is controlled by the accessibility of external goethite surfaces to phosphate rather than by diffusion of phosphate into micropores (Ø 〈 2 nm). We studied the phosphate sorption kinetics of pure and PGA‐coated goethites that differed in their microporosity (N 2 at 77 K, 46 vs. 31 mm 3 g −1 ). Because drying may affect the structure or surface coverage of PGA, we also tested the effect of freeze‐drying on the slow phosphate sorption. The samples were examined by gas adsorption (N 2 , CO 2 ) and electrophoretic mobility measurements. Phosphate sorption and PGA‐C desorption were studied in batch experiments for 3 wk at pH 5. In PGA‐coated samples, the slow phosphate sorption was independent of micropore volume. Phosphate displaced on average 57% of PGA‐C within 3 wk. Similar to phosphate sorption, the PGA‐C desorption comprised a rapid initial desorption, which was followed by a slow C desorption. Sorption competition between phosphate and presorbed PGA depended on the 〈 10‐nm porosity and the C loading of the adsorbent. The efficacy of phosphate to desorb PGA generally increased after freeze‐drying. We conclude for PGA‐coated goethites that (i) freeze‐drying biased the slow phosphate sorption by changing the structure/surface coverage of PGA, and (ii) within the time frame studied, micropores did not limit the rate of the slow phosphate sorption. Rather, the slow, gradual desorption of PGA and/or the diffusion of phosphate through PGA coatings controlled the slow phosphate sorption to PGA‐coated goethite.
    Type of Medium: Online Resource
    ISSN: 0361-5995 , 1435-0661
    URL: Article
    DOI: 10.2136/sssaj2005.0340
    RVK:
    RA 4845
    Language: English
    Publisher: Wiley
    Publication Date: 2006
    detail.hit.zdb_id: 241415-6
    detail.hit.zdb_id: 2239747-4
    detail.hit.zdb_id: 196788-5
    detail.hit.zdb_id: 1481691-X
    SSG: 13
    SSG: 21
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  • 6
    Online Resource
    Online Resource
    Kinetics of Phosphate Sorption to Polygalacturonate‐coated Goethite
    Wiley ; 2006
    In:  Soil Science Society of America Journal Vol. 70, No. 2 ( 2006-03), p. 541-549
    Details
    In: Soil Science Society of America Journal, Wiley, Vol. 70, No. 2 ( 2006-03), p. 541-549
    Abstract: Biogenetic polysugars may affect the sorption characteristics of soil mineral particles in the rhizosphere. We hypothesized that polygalacturonate [PGA, (C 6 H 7 O 6 ) n − ] coatings on goethite reduce the diffusion of phosphate into the pores of the adsorbent. Goethite was preloaded with PGA (0–10 mg C g −1 ). The samples were characterized by N 2 and CO 2 adsorption, electrophoretic mobility measurements, and scanning electron microscopy/energy dispersive X‐ray analysis (SEM‐EDX). The phosphate sorption kinetics was studied with batch experiments over 2 wk at pH 5 and an initial phosphate concentration of 250 μ M Pore volume and specific surface area of the goethite samples declined after PGA addition. The PGA coatings reduced the ζ‐potential of goethite from 42.3 to −39.6 mV at the highest C loading. With increasing PGA‐C content and decreasing ζ‐potential the amount of phosphate sorbed after 2 wk decreased linearly ( P 〈 0.001). Sorption of phosphate to pure and PGA‐coated goethite showed an initial fast sorption followed by a slow sorption reaction. At the smallest C loading (5.5 mg C g −1 ) the portion of phosphate retained by the slow reaction was smaller than for the treatment without any PGA, while at higher C loadings the fraction of slowly immobilized phosphate increased. Our results suggest that at low C‐loadings PGA impaired the intraparticle diffusion of phosphate. In contrast, the slow step‐by‐step desorption of PGA ( 〈 52% within 2 wk) or the diffusion of phosphate through PGA coatings or both are rate limiting for the slow phosphate reaction at C loadings 〉 5.5 mg C g −1
    Type of Medium: Online Resource
    ISSN: 0361-5995 , 1435-0661
    URL: Article
    DOI: 10.2136/sssaj2005.0250
    RVK:
    RA 4845
    Language: English
    Publisher: Wiley
    Publication Date: 2006
    detail.hit.zdb_id: 241415-6
    detail.hit.zdb_id: 2239747-4
    detail.hit.zdb_id: 196788-5
    detail.hit.zdb_id: 1481691-X
    SSG: 13
    SSG: 21
    Library Location Call Number Volume/Issue/Year Availability
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    Online Resource
    Open Access Request
    Availability (electronic / print)
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