Impact of Humic Acids on Phosphorus Retention and Transport
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ORIGINAL PAPER
Impact of Humic Acids on Phosphorus Retention and Transport Yudi Wu 1 & Simeng Li 2
&
Gang Chen 1
Received: 13 May 2020 / Accepted: 23 July 2020 # Sociedad Chilena de la Ciencia del Suelo 2020
Abstract Phosphorus (P) loss is undesirable but prevalent in agricultural fields, as its leaching into natural water bodies usually triggers algae blooms and hypoxic conditions hazardous to aquatic ecosystems. In many developing countries, animal manure, which usually contains high levels of N, P, and organic matter, is directly applied as an economic fertilizer. While the manure-related greenhouse gas (GHG) emission issues have been widely discussed, the impacts of manure applications on nutrient leaching has been rarely discussed. In this study, we have investigated the impact of humic acid (HA) (i.e., a major derivative during manure degradation) on the adsorption and transport of P in goethite-coated silica sand through a series of batch isotherms and column experiments under steady-state flow conditions. The results show that 40 mg L−1 HA could lower the maximum adsorption capacity of goethite-coated silica (for P) by ~ 60%, leading to an increase in P leaching by ~ 70% in the media. This research demonstrates the negative impact that HA applications may have on P retention in agricultural fields. Keywords Phosphorus transport . Humic acid . Goethite coating . Isotherm adsorption . Column experiment
1 Introduction Concerns over excessive eutrophication have been increasingly reported (Fischer et al. 2017). As a consequence of high nutrient (especially phosphorus (P)) accumulation, eutrophication provokes nuisance algae blooms and “dead zoom” in aquatic ecosystem. Particular attentions have been made on appreciable subsurface P loss from agricultural land, which was well documented in coarse-textured soil, high weathered soil, and porous organic soil (Kleinman et al. 2015). Thus, it is an exigency to understand P transport in subsurface soil and subsequent leaching to surrounding water bodies. Phosphorus transport is largely affected by soil structure and properties. Although metal oxides (e.g., magnetite, kyanite, and goethite) in soil enhance nutrients’ stability (Yaghi * Simeng Li [email protected] 1
Department of Civil and Environmental Engineering, FAMU-FSU College of Engineering, 2525 Pottsdamer Street, Tallahassee, FL 32310, USA
2
Department of Civil Engineering, California State Polytechnic University Pomona, 3801 West Temple Avenue, Pomona, CA 91768, USA
and Hartikainen 2013), macropores and preferential flow in subsurface soil provide direct pathways for P leaching (Bergström et al. 2015). An example is colloid-facilitated transport, a strong sorbent bonding P, would rapidly transfer P through the macropores to aquatic environment (Vendelboe et al. 2011). To improve P acquisition, inorganic P fertilizers were reported to be co-applied with novel materials such as artificial humic substances (Yang et al. 2019), natural humic substances (Hua et al. 2008), and geochemical-modified sewage sludge (
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