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PUBLICATION NUMBER
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AAT 8708701
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TITLE
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ASPECTS OF NITROGEN KINETICS IN MID-ATLANTIC SOILS (RETENTION, ADSORPTION, GROUNDWATER, DELAWARE)
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AUTHOR
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CARSKI, THEODORE HENRY
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DEGREE
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PHD
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SCHOOL
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UNIVERSITY OF DELAWARE
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DATE
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1986
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PAGES
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104
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SOURCE
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DAI-B 47/12, p. 4705, Jun 1987
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SUBJECT
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AGRICULTURE, AGRONOMY (0285)
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The use of miscible displacement techniques to study kinetics of ion exchange on clay minerals and soils is increasing. A device that ensures constant dilution volumes, regardless of adsorbent, was developed to differentiate the adsorption and desorption processes from the dilution process. This device, the stirred-flow reaction chamber, was employed to kinetically study nitrate retention and differentiation of soil N fractions.
Anion adsorption-desorption kinetics for systems including Cl, NO(,3), and SO(,4) were studied using soils of the Mid-Atlantic region. Nitrate-Cl exchange was nearly 100% reversible, stoichiometric, and very rapid, indicating simple electrostatic exchange. Total amounts of NO(,3) or Cl adsorbed accounted for only 11% of the anion exchange capacity (AEC) when soils were pre-saturated at very low opposing anion concentrations (0.7 mM (-) charge). Total NO(,3) or Cl adsorption accounted for 90% of the AEC when the pre-saturating concentration equalled 0.2 M (-) charge. This may indicate the need for differentiation of total and effective AEC.
The chemically induced release of NH(,4) from four Delaware soils was monitored over time using the stirred-flow system. The extractants used were 0.02 M KMnO(,4) - 0.5 M H(,2)SO(,4) at 297 K, and 0.01 M CaCl(,2) at 368 K. The kinetic approach presented does allow direct differentiation of two NH(,4) releasing reactions. The reactions were considered to represent the release of NH(,4) from an inorganic and an organic source. Using this approach, estimates of these pools were made and compared with estimates based on traditional batch techniques. Neither extractant gives direct evidence for the existence of a chemically active pool, however, there is indirect evidence for such a pool.
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