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Sorption of Para‐Xylene Vapors on Salt‐Treated Soils Measured by Flow‐Equilibration and Gas Chromatography Methods
Author(s) -
Rhue R.D.,
Pennell K.D.,
Reve W. H.,
Hornsby A. G.
Publication year - 1993
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1993.00472425002200030017x
Subject(s) - sorption , chemistry , adsorption , anhydrous , soil water , vapor pressure , salt (chemistry) , environmental chemistry , volume (thermodynamics) , chromatography , organic chemistry , geology , soil science , thermodynamics , physics
The impact of soil properties other than organic C content and surface area on vapor‐phase sorption has rarely been considered. This study was conducted to determine the effect of salt, namely CaCl 2 , on the sorption of p ‐xylene vapor under anhydrous and hydrated conditions. Sorption on Webster soil (Typic Haploquolls) before and after removal of organic C was measured using a flow‐equilibration method. In addition, the utility of an eluted pulse gas chromatography method was evaluated using the sand fraction of Oldsmar soil (Alfic Arenic Haplaquods) as a column‐packing material. The CaCl 2 significantly decreased p ‐xylene sorption at both 0 and 90% RH for both adsorbents. Under anhydrous conditions, reduced sorption by Oldsmar sand was evidenced at low p ‐xylene vapor pressures by a constant net retention volume and symmetrical peaks, indicating linear sorption and ideal behavior at these vapor pressures (i.e., the Henry's region). In the absence of salt, the net retention volume continued to increase at p ‐xylene vapor pressures as low as 0.33 Pa, indicating isotherm nonlinearity, even at this low vapor pressure. This difference in retention behavior suggests that salt modified the nature of the surface of the sorbents. Under hydrated conditions, the reduction in sorption may be related to the salting‐out effect of CaCl 2 on gas solubility in adsorbed water films. These data suggest that the distribution and migration of organic vapors may be substantially greater in salt‐affected soils due to reduced sorption on both the dry and water‐coated solid phases that are present.