Open AccessUse of Fly Ash as Soil Amendment to Offset Anion Exclusion Effect on Nitrate Transport
Author(s) -
Medina Ricardo,
Menezes G.B.,
Khachikian C.S.,
Ellis A.
Publication year - 2015
Publication title -
vadose zone journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.036
H-Index - 81
ISSN - 1539-1663
DOI - 10.2136/vzj2014.08.0103
Subject(s) - fly ash , saturation (graph theory) , leachate , hydraulic conductivity , chemistry , amendment , soil water , nitrate , soil science , environmental chemistry , environmental science , mathematics , organic chemistry , combinatorics , political science , law
This study investigated the direct effect of fly ash used as a soil amendment on anion exclusion in NO 3 − transport in a variably saturated soil. A sandy clay soil was amended with Class F fly ash (FA) at four levels: 0, 2, 10, and 20% FA. The soils were placed in a small soil column and kept at constant saturation using a steady‐state centrifugation unsaturated flow apparatus. Three saturation ranges were investigated, 0.75 to 0.9, 0.4 to 0.45, and 0.27 to 0.29, designated as high, medium, and low saturation, respectively. Ammonium nitrate (0.7 mmol L −1 ) solution was passed through the soil sample, and the leachate was collected at predetermined intervals up to a total volume equivalent to 12 effective pore volumes. The leachate samples were analyzed for NO 3 − concentration using ion chromatography, and breakthrough curves were constructed. Experimental and modeling results showed that the amount of fly ash and saturation level had a significant effect on the hydraulic properties of the soil, reducing the hydraulic conductivity and increasing water retention. Furthermore, it was shown that the fly ash treatment slowed the transport of NO 3 − , especially at low saturation levels, when the effect of anion exclusion is thought to be stronger.