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Anion Exchange Chemistry of Middle Atlantic Soils: Charge Properties and Nitrate Retention Kinetics
Author(s) -
Toner C. V.,
Sparks D. L.,
Carski T. H.
Publication year - 1989
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1989.03615995005300040013x
Subject(s) - chemistry , soil water , desorption , adsorption , nitrate , ion exchange , electrolyte , kinetics , cation exchange capacity , inorganic chemistry , titration , potentiometric titration , point of zero charge , salt (chemistry) , environmental chemistry , ion , soil science , geology , organic chemistry , physics , electrode , quantum mechanics
The negative impact of nitrate (NO 3 ) on groundwater supplies has sparked a great deal of interest and concern in recent years, particularly in areas where coarse‐textured soils abound. In light of this concern, the anion exchange chemistry of eight soils from the Middle Atlantic region was studied with particular emphasis on NO 3 retention and kinetics. The soils were chosen to encompass a range of physicochemical and mineralogical properties and were extensively characterized. Anion exchange capacity (AEC) was determined on Cl‐saturated samples by desorption of Cl with SO 4 . Anion exchange capacity ranged from 0 to 1.35 cmol c kg −1 for the eight soils and was found to parallel increases in clay and Fe oxide contents in the soil profiles. Point of zero salt effect (PZSE) values were determined by potentiometric titration with 0.001, 0.01, and 0.1 M NaCl as the indifferent electrolyte. These were of little value in predicting the development of AEC for the soils. The kinetics of NO 3 adsorption and desorption were studied using a stirred‐flow reaction chamber and a first‐order reaction best described the data. Nitrate adsorption was found to be completely reversible, indicating a simple electrostatic retention mechanism. The effect of pH and NO 3 concentration on cumulative NO 3 adsorbed (CNA) and on NO 3 adsorption kinetics was also studied. The CNA was found to increase with a decrease in pH below 5.5 and to increase with increasing NO 3 concentration. The latter indicated an increase in competitiveness by NO 3 for positively charged sites.