Trace Element Transport in Putting Green Root Mixes Amended by Coal Combustion Products (CCP)

Abstract

Golf course putting green (PG) construction methods rely on homogenous mixtures of coarse and medium-sized sands as primary components of the root mix. In some locations, cost of quartz sand delivery is prohibitive. Coal combustion products (CCP) have been used to amend soil in agricultural, horticultural, and land reclamation endeavors. A greenhouse study evaluated the hydraulic properties of PG root mixes constructed with sand-sized bottom ash (BA) and silt-sized fly ash (FA) as substitutes for mineral sand and soil components. Columns (5 cm ID x 42 cm) were packed with one of three CCP-containing root mixes or a non-amended, control root mix; all of soil textural class commonly used in putting greens. Pore volumes of leachate were collected 0, 11, 24, and 100 days after [turfgrass] sodding (DAS), and analyzed for elemental content. Compactive forces were applied to root mix surfaces throughout the 6,12, or 18 month experimental periods, following which hydraulic parameters and particle size distribution (PSD) were measured. Root mixes and compaction treatments interactively affected K, The control PG mix generally demonstrated the greatest saturated hydraulic conductivity (Ks), regardless of compaction treatment. Root mixes containing FA and sand (SFA) exhibited severe reductions in K-s. Similarly, the PSD of the surface 7 cm of the CCP-root mixes became more finely-textured with cumulative compaction events. Ibis soil textural alteration was likely responsible for impaired entry and flow of water in the CCP-amended root mixes, yet conductivity rates observed after 18 months in all but the sand-FA (SFA) root mixes mix fell within accepted ranges. Trace element concentrations in root mix leachate varied with CCP inclusion rate and cumulative pore volumes, and were highly correlated to the presence of fly ash (FA). Bottom ash may be better suited for putting green root mixes amendment than FA, yet further research is necessary to determine optimal rates of inclusion.