Characterization of the porous structure of soils: adsorption of nitrogen (77 K) and carbon dioxide (273 K), and mercury porosimetry

Abstract

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.

Mobility of heavy metals in soils amended with sewage sludge

“…Calcixerollic Xerochrepts (Cx1 and Cx2) and Px were agricultural soils, whereas Lh was uncultivated (Echeverría et al 1998(Echeverría et al , 1999a. Samples from the top 15 cm soil layer were air-dried, ground, and sieved through a 2-mm mesh before determining specifics soils properties: (1) particle-size distribution by fractionation using wet sieving and sedimentation (Primo Yúfera and Carrasco Dorriens 1987); (2) mineralogical composition of clay fraction by a Siemens D500 X-ray diffractometer; (3) total amount of carbon and nitrogen by using a Carlo Erba EA 1108 elemental analyzer; (4) inorganic carbon (Loeppert et al 1984); (5) pH (McLean 1982); (6) cation-exchange capacity (CEC) by Ca 2+ saturation, displacement by 1 M sodium acetate and measurement of Ca 2+ ions by atomic absorption spectroscopy (Jackson 1982); and (7) surface area by N 2 gas adsorption at 77 K (Echeverría et al 1999b). Selected physical and chemical characteristics of soils are presented in Table 1.…”

“…Sequential extractions have been used to fractionate heavy metals in sludge (McGrath and Cegarra 1992;Petruzzelli et al 1994) or sludge-amended soils to investigate their chemical distribution among the solid fractions (Emmerich et al 1982;McGrath and Cegarra 1992) and, indirectly, their mobility and plant availability (Dudka and Chlopecka 1990;Sims and Kline 1991;Tsadilas et al 1995). Despite uncertainties related to the selectivity of the various extractants and to potential problems due to readsorption, sequential extraction procedures provide detailed information about the status of trace metals in soils (Pickering 1986;Echeverría et al 1998).…”

Área superficial específica, porosidade da fração argila e adsorção de fósforo em dois latossolos vermelhos

“…Nessa região, tem-se o enchimento de macroporos, porém, tratando-se de materiais com baixo volume de microporos, a extrapolação dessa região correspondeu ao volume de microporos (Echeverría et al, 1999).…”

Characterizing soil pore structure using nitrogen adsorption, mercury intrusion porosimetry, and synchrotron-radiation-based X-ray computed microtomography techniques

“…In accordance with this, soils having higher clay and iron oxide content showed larger BET surface area and pore volume from nanometers to tens of nanometer. The contribution of pores within the soil organic matter (SOM) to pore volume measured by NAI is supposed to be negligible due to the low thermal energy of N 2 and its restricted diffusion at 77 K within the polymeric structure of SOM (Echeverria et al 1999). Inaccessibility of SOM for N 2 may cause underestimation of pore volume in the soils with higher organic matter content (Echeverria et al 1999;Paz Ferreiro et al 2010).…”

“…The high-resolution micro-CT technique has been used to quantify soil pore space with a spatial resolution of several microns (Elliot and Heck 2007;Peth et al 2008;Papadopoulos et al 2009;Sander et al 2008;Taina et al 2008;Tippkoetter et al 2009;Zhou et al 2013). The most commonly indirect methods for soil pore analysis are mercury intrusion porosimetry (MIP), gas adsorption isotherms (Dal Ferro et al 2012;Echeverria et al 1999;Filimonova et al 2006;Jozefaciuk et al 2009;Sasanian and Newson 2013), and soil water retention curve (Imhoff et al 2010;Dexter et al 2008;Eynard et al 2004;Hajnos et al 2006). The most common gas adsorption method for examining soil pore structure is the use of N 2 adsorption at 77 K (Gregg and Sing 1982;Hajnos et al 2006).…”