Quantifying the legacy of coal combustion products in riverine sediments

Abstract

Coal fired power plants (CFPPs) produce much of the world’s energy and generate large quantities of coal combustion products (CCPs), including organic material (OM), fly ash, bottom ash, spheroidal carbonaceous particles (SCPs) and metals, much of which is stored near CFPPs. Despite projected closures of CFPPs, these waste products will persist and can potentially impact environments. Here, we develop a new method for SCP enumeration by analyzing 14 riverine sediment sites and then use bootstrapping techniques to quantify measurement precision as a function of subsample number. We recommend the enumeration of SCPs in sets of at least 10 subsamples per site to maximize precision and minimize error. Next, using SCP, toxic metal, and OM concentrations, we explore the differences in CFPP contamination near an active and a legacy (closed) plant. We find that for our study sites, SCPs are a better proxy for CCP environmental impacts than toxic metal or OM concentrations. SCP concentrations are highest near the active CFPP but also are present near the legacy CFPP. Even after coal combustion ceases and impoundments are closed, CCPs persist in the environment.