Evaluating risks to wildlife from coal fly ash incorporating recent advances in metals and metalloids risk assessment

Abstract

EDITOR'S NOTE:The Baseline Ecological Risk Assessment (BERA) of residual coal-fly ash in Watts Bar Reservoir was conducted following a 2008 spill from the Tennessee Valley Authority Kingston Fossil Plant (Roane County, Tennessee, USA). Results of the BERA were used to focus the long-term management strategy for the impacted river system. This paper is among 7 peer-reviewed papers in the special series, "Ecological Risk Assessment for Residual Coal Fly Ash at Watts Bar Reservoir, Tennessee." The series includes papers presenting the following: problem formulation for the river system; sediment toxicity test procedures; benthic community analysis techniques; methods used to evaluate risk to fish, and riparian and aquatic wildlife; an extensive analysis characterizing risk to the insectivorous tree swallow; and finally, how the BERA results influenced management decisions. ABSTRACTCurrent scientific advances in metal and metalloid risk assessment were applied to evaluate risk to aquatic and riparian wildlife species potentially impacted by residual coal fly ash after cleanup of an unprecedented large ash release into an aquatic environment-the first assessment of its kind. Risk was evaluated using multiple lines of evidence (LOE), including 1) tissue-based risk assessment of inorganic concentrations in piscivorous and insectivorous bird eggs and raccoon organs, 2) deterministic and probabilistic diet-based risk estimates for 10 receptors species, 3) raccoon health metrics, and 4) tree swallow nest productivity measures. Innovative approaches included use of tissue-based toxicity reference values (TRVs), adjustment of bioavailability in the dietary uptake models (using sequential metal extractions in sediment), partitioning chemical species into uptake compartments (e.g., prey gut, nongut, sediment), incorporating uncertainty in both modeled dose and dietary TRVs, matching TRVs to chemical forms of constituents, and pairing these LOEs with reproductive success or health status of sensitive receptor species. The weight of evidence revealed that risk to wildlife from residual ash was low and that risk, though low, was most pronounced for insectivorous birds from exposure to Se and As. This information contributes to the debate surrounding coal combustion residue regulations prompted by this ash release. Because of the responsible party's proactive approach of applying state-of-the-art methods to assess risk using several LOEs that produced consistent results, and because of their inclusion of the regulating agencies in decisions at every step of the process, the risk assessment results were accepted, and an effective approach toward cleanup protective of the environment was quickly implemented. This study highlights the value of using multiple LOEs and the latest scientific advances to assist in timely decision making to obtain an effective remedy for an emergency spill. Integr Environ Assess Manag 2015;11:67-79. © 2014 SETAC

Application of ecological risk assessment in managing residual fly ash in TVA's Watts Bar Reservoir, Tennessee

“…The 17 receptor groups evaluated included fish, benthic invertebrates, aquatic plants (periphyton and macrophytes), and wildlife that feed in and around the river system (see conceptual site model in Figure 2 in Walls, Jones et al 2015, this issue). BERA details are available in the project report (ARCADIS ), and details for several receptors are presented in 5 other articles in this series (Buys et al , Meyer et al , Rigg et al , Stojak et al , Walls, Meyer et al ).…”

“…Moderate to low risks were indicated for benthic organisms immersed in sediments that contained greater than 40% residual ash (Stojak et al , this issue). Low risks also were indicated for insectivorous birds such as killdeer and tree swallow, which both consume a large proportion of invertebrates that inhabit surface sediments for at least 1 life stage (Meyer et al , Walls, Meyer et al , this series).…”

Effects of coal fly ash on tree swallow reproduction in Watts Bar Reservoir, Tennessee

“…In the laboratory, homogenized egg content, unrinsed eggshells, and whole body nestlings were analyzed for the 26 inorganic ash‐related constituents of potential ecological concern (COPECs) identified for the site (Al, Sb, As, Ba, Be, B, Cd, Ca, Cr, Co, Cu, Fe, Pb, Mg, Mn, Hg, Mo, Ni, K, Se, Na, Sr, Ag, Tl, V, Zn). Although Hg was previously identified as a legacy constituent in different areas of Watts Bar Reservoir, it was included in this analysis given its significant correlation with coal fly ash (see Meyer et al , this issue for correlations of ash percent with COPEC concentrations). Percent moisture was recorded to convert concentrations to a dry‐weight (dw) basis.…”

Ecological risk assessment for residual coal fly ash at Watts Bar Reservoir, Tennessee: Site setting and problem formulation

“…These various types of samples were used to estimate bioavailability and bioaccumulation of COPECs from diet and other exposure pathways, as well as to model bioavailability to the respective predators. Subsequent articles focus on the evaluations for fish (Rigg et al , this issue), benthic invertebrates (Buys et al , this issue, and Stojak et al , this issue), aquatic‐ and riparian‐feeding wildlife (Meyer et al , this issue), and aerial‐feeding insectivores (i.e., tree swallows; Walls et al , this issue).…”

“…Tree swallow egg and nestling weight, tarsus length, and length of third primary feather were also measured. Also included in the BERA are raccoon gross lesions measured during necropsy, and raccoon blood count and plasma biochemistry (Souza et al ; Meyer et al , this issue).…”