Summary Accessibility of adsorbates to internal active sites of soils depends mainly on the porous structure of the material. We aimed to determine the distribution of pore sizes in soils with varied physico‐chemical properties, by combining adsorption of gases and mercury porosimetry. Microporosity was studied by physical adsorption of N2 at 77 K and CO2 at 273 K; mercury intrusion porosimetry allowed us to evaluate the macroporosity; and mesoporosity was determined by capillary condensation of N2 and mercury porosimetry. The soils investigated were essentially macroporous, with volumes between 0.33 and 0.73 cm3 g–1; the maxima in the differential pore‐size distribution were in the range 1500–4000 nm. Volumes of meso‐ or micropores were always less than 10% of macropore volumes. Calculations based on the theory of Dubinin and the αs‐method (for N2 at 77 K) provided, generally, coincident results. In a soil containing much organic matter, N2 adsorption was only one‐ninth that of CO2 adsorption, showing that N2 adsorption into the narrow micropores of organic matter was kinetically restricted. When accessibility to micropores was not restricted, the total volume of micropores could be deduced from N2 adsorption, whereas CO2 measured exclusively the narrowest microporosity.
Morera, M. T., Echeverría J. and Garrido, J. 2002. Bioavailability of heavy metals in soils amended with sewage sludge. Can. J. Soil Sci. 82: [433][434][435][436][437][438]. The recycling of sewage sludge to agricultural land results in the slow accumulation of potentially toxic heavy metals in soils. A greenhouse experiment was conducted to determine the bioavailability of Cu, Ni, Pb and Zn applied to soils in urban anaerobically stabilized sewage sludge. The soils were Lithic Haplumbrept (Lh), Calcixerollic Xerochrept (Cx1 and Cx2) and Paralithic Xerorthent (Px). Sunflower plants (Helianthus annuus L) were grown in the soils following amendment with the sludge. The addition of sewage sludge markedly increased the average dry weight of the plants in the soils that had lower yields without sludge addition (Lh, Cx2, and Px). The acid pH of the Lh soil favoured the bioavailability of Zn from sewage sludge. The bioavailability of Cu was greater in the alkaline soils than in the acidic soil (Lh), which can be attributed to the high organic matter content of the Lh soil which complexes Cu and impairs its uptake by the plants. The concentration of metals in the plants increased with the sewage sludge dose. The effect of the soil type on the metal concentration in plants was greater that the effect of the dose. Le pH acide du Lh accroît l'absorption du Zn des boues par les plantes. La biodisponibilité du Cu est plus importante dans les sols alcalins que dans le sol acide (Lh). On l'attribue à la forte concentration de matière organique dans le Lh et à la formation de complexes avec le Cu, ce qui empêche les végétaux d'absorber cet élément. La concentration de métaux dans la plante augmente avec la quantité de boues usées employée. Le type de sol agit plus sur la concentration de métaux lourds dans la plante que le volume de boues usées.
. 2001. Mobility of heavy metals in soils amended with sewage sludge. Can. J. Soil Sci. 81: [405][406][407][408][409][410][411][412][413][414]. Sewage sludges added to arable land can improve soil fertility and physical properties. However, the concentrations of heavy metals commonly found in sludges limits their application to soil. The purpose of this paper is to evaluate the mobility of heavy metals (Cd, Cu, Ni, Pb and Zn) in four soils amended with different rates (0, 80, 60 and 320 t ha -1 ) of anaerobically stabilized urban sewage sludge. Total metal content in the sewage sludge was Zn >> Cu > Pb > Ni >> Cd. Sludge, soils and sludge-soil mixtures were fractionated by the Tessier sequential extraction procedure. The fractions extracted by H 2 O 2 /HNO 3 and NH 2 OH.HCl were the most abundant pools for metals under study. The apparent mobility of metals in the sludge was Zn ≈ Cd ≈ Ni > Pb > Cu. The addition of sewage sludge in soils increased the percentages of metal extracted in non-residual fractions. ANOVA showed that the most significant increases were those of Zn, followed by Cu and Pb; there were no statistical differences (P < 0.05) for Ni and Cd. Exchangeable Zn from sludge was immobilized in basic soils. The other trace metals showed no fraction redistribution. The soils and sludge-treated soil samples were also extracted with EDTA and DTPA. Extraction with EDTA was more sensitive to soil type, whereas extraction with DTPA showed wider variation with metals. Both chelates seemed to be more effective to assess the mobility of metals added with the sludges at low concentrations than the Tessier's chemical partitioning.Key words: Soils, sewage sludge, heavy metals, mobility Morera, M. T., Echeverría, J. C. et Garrido, J. J. 2001. Mobilité des métaux lourds dans les sols amendés avec des boues usées. Can. J. Soil Sci. 81: 405-414. L'addition de boues usées aux terres arables peut améliorer la fertilité et les propriétés physiques du sol. La concentration de métaux lourds dans les boues restreint toutefois une telle application. Les auteurs ont évalué la mobilité des métaux lourds (Cd, Cu, Ni, Pb et Zn) dans quatre sols auxquels avait été ajoutée une quantité variable (0,80, 60 et 320 t ha -1 ) de boues usées urbaines stabilisées en anaérobiose. La concentration totale de métaux dans la boue était de Zn >> Cu > Pb > Ni >> Cd. La boue, le sol et le mélange sol-boue ont été fractionnés par la technique d'extraction séquentielle de Tessier. Les fractions obtenues par extraction dans H 2 O 2 /HNO 3 et NH 2 OH.HCl contenaient la plus grande quantité de métaux de toutes les fractions examinées. La mobilité apparente des métaux dans la boue correspond à Zn ≈ Cd ≈ Ni > Pb > Cu. L'addition de boues usées au sol augmente la proportion de métal extrait des fractions non résiduelles. L'analyse de la variance révèle que c'est la concentration de Zn qui connaît la hausse la plus importante, le Cu et le Pb arrivant en second; les auteurs n'ont relevé aucune variation statistiquement significative (P < 0,05) pour le Ni ...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.