C - Lublin

More documents

Recommendations

Info

According to this, when x/N (1-x) is plotted against p/p 0 a straight line should result with slope s=(C BET -1)/N m C BET and intercept i = 1/ N m C BET . Solution of the two simultaneous equations gives N m and C BET - N m =1/(s+i) and C BET =(s/i)+1. The second step is to calculate the surface area from the dependence: S=N m ×M -1 ×L×ω, where L is the Avogadro number (6.02×10 23 molecules mole), M is the molecular weight of water (gram/mole) and ω is the molecule cross-sectional area (10.8×10 -20 m 2 for water). If N m is expressed in grams of adsorbate per gram of solid the surface area S (m 2 g -1 ) is estimated from the monolayer capacity as S=3612× N m . In order to use of any of these formulae, it is necessary to know the value of the molecule cross-sectional area, ω. Emmett and Brunauer proposed that ω be calculated from the density ρ of the adsorbate in the ordinary liquid or solid form. This leads to the formula: 2 / 3 16 ω = f ( M ρ N) × 10 Here M is the molecular weight of adsorbate, N is Avogadro's constant, f is a packing factor and ρ is the mass density of the bulk liquid. With the hexagonal close packing at the density of bulk liquid phase the value of f is 1.091 and if ρ is expressed in kilograms per cubic meter ω is expressed in square nanometers. For nitrogen as adsorbate at -195 0 the value ω=0.162 nm 2 (16.2 Å 2 ). The adsorption of water vapour is complicated in that it is highly specific and it appears that the application oh the BET equation to water isotherms, in many cases, has no real validity. Early work indicated that the value of the molecule cross-sectional area is 10.6 Å 2 (0106 nm 2 ). Harkins and Jura showed that it was 14.8 Å 2 . MEASUREMENT OF SURFACE AREA According to Polish Standard PN-Z-19010-1 the surface area is estimated as described further. Before the adsorption measurement the soil samples are dried in a vacuum chamber with the concentrated sulphuric acid until the weight of samples reached constant values. The soil sample of the weight equal approximately to 3g is put into the glass vessel and placed over sulphuric acid solution. The sample is equilibrated with water vapour during two days. The amount of adsorbed water vapour is computed as the difference between the weight of the sample with water and the dry sample (dried in an oven at 105°C). The relative water pressures are obtained from the density of sulphuric acid solutions. Fife levels of relative pressure are selected in range of 0.034 to 0.352. The adsorption measurements are replicated three times keeping the temperature constant, T=20°C ± 0.5. The specific surface area is calculated from adsorption data as described above. 134
SURFACE AREA AND OTHER SOIL PROPERTIES Surface area is highly sensitive indicator of various processes occurring in soils: organic matter accumulation, leaching and oxidation, soil acidification, alkalization, silica accumulation, wetting-drying cycles and many others. Surface area is well correlated with many soil properties, as this is shown in Table 1. Table 1. Correlation coefficients of linear regression between the specific surface area, obtained from water vapour and nitrogen, and selected properties of mineral soils (482 soil samples) Fraction OM CEC Exchangeable cations
Page 2 and 3:
PHYSICS, CHEMISTRY AND BIOGEOCHEMIS
Page 4 and 5:
IN MEMORIAM Dr Ludmila Petrovna Kor
Page 6 and 7:
magnetic (ferrimagnetic) oxides, ma
Page 8 and 9:
educed water activity, would favour
Page 10 and 11:
In this paper AT sorption by surfac
Page 12 and 13:
were obtained with clay content, pH
Page 14 and 15:
In present investigation the quartz
Page 16 and 17:
Hence, the micromorphology suggests
Page 18 and 19:
As the indicators of soil aeration
Page 20 and 21:
Stomatal diffusive resistance of th
Page 22 and 23:
indicators of soil aeration conditi
Page 24 and 25:
REFERENCES 1. 2. 3. 4. 5. 6. 7. 8.
Page 26 and 27:
Table 1. Breakdown of numbers and t
Page 28 and 29:
MORPHOLOGICAL AND PHYSICOCHEMICAL P
Page 30 and 31:
conditions, existing at the first p
Page 32 and 33:
INFLUENCE OF TEMPERATURE ON WATER P
Page 34 and 35:
moisture % 100 90 80 70 60 50 40 so
Page 36 and 37:
STATE OF MICROBIAL COMMUNITIES IN M
Page 38 and 39:
million cells/g soil 25 20 15 10 5
Page 40 and 41:
THE INFLUENCE OF COMPOSITION AND PR
Page 42 and 43:
days grew faster than on substrate
Page 44 and 45:
SOIL SALINITY AND CLIMATE CHANGES I
Page 46 and 47:
POROUS STRUCTURE OF NATURAL BODIES
Page 48 and 49:
These nonuniform classification sys
Page 50 and 51:
Mercury intrusion data are plotted
Page 52 and 53:
METHOD AND MATERIALS The shear stre
Page 54 and 55:
wheat flour NaCl salt fine milk Fig
Page 56 and 57:
The shear experiments revealed two
Page 58 and 59:
Variable charge of mineral surfaces
Page 60 and 61:
3. Huffaker RC and Wallace A 1958 P
Page 62 and 63:
Q V (pH)/N t = α(pH) = n ∑ i= 1
Page 64 and 65:
REFERENCES 1. De Wit, J.C.M, Van Ri
Page 66 and 67:
BM - biomass; NM - necromass; MM -
Page 68 and 69:
thousand times at the absence of co
Page 70 and 71:
. m 131.5 131.0 I Height above sea
Page 72 and 73:
SEASONAL VARIABILITY OF SOIL WATER
Page 74 and 75:
The mean difference (MD) and the ro
Page 76 and 77:
Acknowledgement This paper presents
Page 78 and 79: 1992; Selim 1999). The relative imp
Page 80 and 81: 1.0 C rel 0.5 0.0 v=0.7 D=3.28 v=0.
Page 82 and 83: 1.0 a b C rel 0.5 0.0 0 1 2 3 0 1 2
Page 84 and 85: Comparison of before- and after-pul
Page 86 and 87: provides the accessibility of catio
Page 88 and 89: MODEL RESEARCH ON FORMATION OF SYNT
Page 90 and 91: The analysis of the specific surfac
Page 92 and 93: PHOSPHATE-INDUCED CHANGES IN THE SP
Page 94 and 95: According to the data of Table 1, t
Page 96 and 97: MINERAL-ORGANIC COMPOUND OF SOILS:
Page 98 and 99: RESULTS AND DISCUSSION An analysis
Page 100 and 101: INTRODUCTION CHEMICAL DEGRADATION O
Page 102 and 103: of organic particles and their elec
Page 104 and 105: HNO 3 -extractable form is very clo
Page 106 and 107: Results demonstrated that Pb and Cd
Page 108 and 109: tion was measured using the Tjurina
Page 110 and 111: OUTPUT FLUXES OF LEAD IN FOREST ECO
Page 112 and 113: Regional data on Pb concentrations
Page 114 and 115: DEVICE FOR EVALUATION OF THE RAPE P
Page 116 and 117: SPECTROSCOPIC COMPARISON OF HUMIC A
Page 118 and 119: ehavior of sequentially extracted H
Page 120 and 121: MODERN MONITORING SYSTEMS FOR THE M
Page 122 and 123: The control of the measurement syst
Page 124 and 125: ASORPTION AND SURFACE AREA OF SOILS
Page 126 and 127: Nm xCBET N = ( 1− x BET − )[ 1+
Page 130 and 131: POTENTIAL OF AZOLLA CAROLINIANA TO
Page 132 and 133: The decrease of Pb(II) and of Cd(II
Page 134 and 135: 12. 13. 14. 15. 16. Piechalak, A.,
Page 136 and 137: Kloc, 2001]. Nitrogen adsorption is
Page 138 and 139: This is worth noting that the lower
Page 140 and 141: N ( h) 1 2 γ ( h) = [ ( ) ( )] ( )
Page 142 and 143: Exemplary spatial distributions (sa
Page 144 and 145: This is worth noting that significa
Page 146 and 147: adsorbed chemicals to microorganism
Page 148 and 149: were detected in the untreated soil
Page 150 and 151: 0.4 1000 Moisture [Vol.] 0.3 0.2 0.
Page 152 and 153: NITROUS OXIDE EMISSION FROM SOILS W
Page 154 and 155: N2O-N [mg kg -1 ] 100 80 60 40 20 0
Page 156 and 157: LITERATURE 1. 2. 3. 4. 5. 6. 7. 8.
Page 158 and 159: where v(t) - CO 2 production rate;
Page 160 and 161: carbon was involved mainly into mic
Page 162 and 163: Demkin Vitaliiy DrSc Dmitrakov Leon
Page 164 and 165: Priputina Irina PhD Rudko Tadeusz P
show all

C - Lublin

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?