Saturation and Temperature Effects on the Development of Reducing Conditions in Soils

Abstract

All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. S oil redox potential is an estimate of electron activity and is used to predict the electrochemical stability of redox sensitive species. The potential is measured between a Pt-tipped electrode and a reference electrode that are both placed in contact with a soil. Soils with more reducing conditions transfer a relatively negative charge to the Pt electrode, while soils with more oxidizing conditions transfer a relatively positive charge. Redox potential in soil is infl uenced by a number of factors including temperature, microbial activity, and the presence of various electron acceptors, such as oxygen, nitrate, Mn oxides, and Fe oxides (Ponnamperuma, 1972). Soils with oxygen present due to either the absence of saturation or oxyaquic conditions have relatively high redox potentials (Soil Survey Staff, 1999). When soil is saturated with stagnant water, oxygen is depleted from the soil environment during microbial decomposition of organic matter and electrons may then be transferred to alternate electron acceptors such as NO 3 − , Mn(IV) or Fe(III). These microbially mediated reactions are slower at cooler temperatures (Atlas and Bartha, 1987; Paul and Clark, 1996), while greater C abundance leads to increased microbial activity and therefore more rapid reduction.

Sorption behaviour of beryllium-7 and implications for its use as a sediment tracer

“…Reducing conditions can occur in floodplain soils during periods of saturation: Vaughan et al (2009) reported that reducing conditions can develop in floodplain soils after 2 days at temperatures >9°C at depths in excess of 20 cm. Increased concentration of dissolved Mn and Fe in pore waters can be used as an indicator of reduction of Mn and Fe oxides.…”

Redox Dynamics and Oxygen Reduction Rates of Infiltrating Urban Stormwater beneath Low Impact Development (LID)

“…The rapid consumption of DO while the gravel is at >39% saturation is likely caused by microbial respiration in the gravel trench. Although not measured in this study, stormwater is often rich in organic matter [38,54], which we infer as an important electron donor for microbially mediated oxygen reduction in the gravel trench. Furthermore, observed water temperatures for the period of field observation of DO (February-June 2014) range between 7 • C and 23 • C (Figure 3), which are above the benchmark temperature referred to as biological zero (5 • C), below which microbial activity generally ceases [55].…”

“…Vaughan et al (2009) [26] observed that during periods of cooler soil temperatures, saturated soils took longer to become reducing. However in this study, the observed variations in stormwater temperature have no apparent influence on the DO dynamics in the gravel trench (Figure 7 (Figure 7a).…”

“…Warmer water temperatures are associated with greater microbial activities in soils, and therefore higher rates of DO consumption [38]. Vaughan et al (2009) [26] observed that during periods of cooler soil temperatures, saturated soils took longer to become reducing. However in this study, the observed variations in stormwater temperature have no apparent influence on the DO dynamics in the gravel trench (Figure 7 …”

“…Datry et al (2004) [35] reported that seasonal microbial respiration in an infiltration basin was stimulated by the increase in temperature, thereby leading to higher oxygen deficit in summer, whereas cold winter stormwater slightly re-oxygenated groundwater. During the seasons of cooler soil temperatures, often from November through March in the Northern Hemisphere, saturated soils take longer to become reducing [38].…”