Andrew D. McQueen

Campus parking lot stormwater runoff: Physicochemical analyses and toxicity tests using Ceriodaphnia dubia and Pimephales promelas

Campus parking lot stormwater (CPLSW) runoff can mobilize a variety of constituents from vehicular and atmospheric deposition that may pose risks to receiving aquatic systems. The objective of this study was to characterize CPLSW and to discern potential constituents of concern that may affect aquatic biota in receiving systems. Characterization of CPLSW included analyses of metals, oil and grease, and general water chemistry. Toxicity tests were performed using two sentinel species, Ceriodaphniadubia Richard and Pimephales promelas Rafinesque. Metals measured (at their maximum) in CPLSW included 4756microg Al L(-1), 53microg Cu L(-1), 130microg Pb L(-1), and 908microg Zn L(-1). Although CPLSW varied widely in composition and toxicity, constituents of concern included: pH, alkalinity, total suspended solids, biological oxygen demand, chemical oxygen demand, metals, and oil and grease. Fish (P. promelas) were more sensitive to CPLSW than C. dubia with decreased survival in 92% and 15% of the samples (n=13), respectively.

Comparative responses of freshwater organisms to exposures of a commercial naphthenic acid

Comparative toxicity studies using unconfounded exposures can prioritize the selection of sensitive sentinel test species and refine methods for evaluating ecological risks of complex mixtures like naphthenic acids (NAs), a group of organic acids associated with crude oils and energy-derived waters that have been a source of aquatic toxicity. The objectives of this study were to compare responses of freshwater aquatic organisms (vertebrate, invertebrates, and a macrophyte; in terms of acute toxicity) to Fluka commercial NAs and to compare measured toxicity data with peer-reviewed toxicity data for other commercial NA sources and energy-derived NA sources. Exposures were confirmed using high performance liquid chromatography. Responses (7-d LC50s/EC50) ranged from 1.9 mg L(-1) for Pimephales promelas to 56.2 mg L(-1) for Typha latifolia. Following P. promelas in order of decreasing sensitivity were Ceriodaphnia dubia (7-d LC50 = 2.8 mg L(-1)), Hyalella azteca (7-d LC50 = 4.1 mg L(-1)), Chironomus dilutus (7-d LC50 = 6.5 mg L(-1)), and T. latifolia (7-d EC50 = 56.2 mg L(-1)), indicating that in terms of sensitivities, fish > invertebrates > plant for Fluka NAs in this study. Factors that affect exposures and measurements of exposures differ among commercial and energy-derived NAs and constrain comparisons. Despite differences in exposures, fish and invertebrates were relatively sensitive to both commercial and energy-derived NA sources (based on laboratory measurements and peer-reviewed data) and could be appropriate sentinel species for risk evaluations.

Responses of Lyngbya wollei to algaecide exposures and a risk characterization associated with their use

To make informed decisions regarding management of noxious algal growths, water resource managers require information on responses of target and non-target species to algaecide exposures. Periodic treatments of Phycomycin®-SCP (sodium carbonate peroxyhydrate) followed by Algimycin®-PWF (gluconate and citrate chelated copper) to control Lyngbya wollei growths for ten years provided an opportunity for a risk evaluation of treated coves in Lay Lake, AL. Abiotic sediment characteristics (acid soluble copper concentrations, acid volatile sulfides, percent organic matter and cation exchange capacity) and survival of Hyalella azteca and Chironomus dilutus were measured in sediment samples from treated and untreated coves to assess the bioavailability of potential copper-residuals. In laboratory studies to seek a more effective approach for managing the growth of Lyngbya, six algaecide treatments consisting of combinations of copper-based algaecides (Cutrine®-Ultra, Clearigate® and Algimycin®- PWF), a hydrogen peroxide based algaecide (Phycomycin®-SCP) and an adjuvant (Cide-Kick II) were assessed for efficacy in controlling L. wollei sampled from Lay Lake. The most efficient algaecide treatment was determined based on post-treatment algal wet weight and visual observations of responses to exposures. To estimate the margin of safety for non-target organisms, Pimephales promelas was exposed to the most efficacious treatment and a treatment of Phycomycin®-SCP followed by Algimycin®-PWF. Results from sediment experiments demonstrated that there were no measureable copper residuals and no adverse effects on H. azteca and C. dilutus from sediments following ten years of copper-based algaecide treatments. Based on the laboratory results, a treatment of Phycomycin®-SCP at 10.1 mg H2O2/L followed by Cide-Kick II at 0.2 mg/L and Algimycin®- PWF at 0.26 mg Cu/L could control the growth of Lyngbya wollei from Lay Lake, AL and enhance the margin of safety for non-target species (e.g. P. promelas).

Effects of Acid Volatile Sulfides (AVS) from Na2S-Amended Sediment on Hyalella azteca

Ratios of acid volatile sulfides (AVS) and simultaneously extracted metals (SEM) have been used extensively for predicting bioavailability of divalent metals (i.e., Cd, Cu, Pb, Ni, Zn) in sediments of aquatic environments. However, the role of sulfides (as AVS) as a toxicant has been largely ignored. The aim of this research was to measure relationships of AVS (as sodium sulfide [Na2S]-amended sediment) and toxicity to a sensitive benthic amphipod Hyalella azteca to evaluate the exposure-response relationships among a series of sulfide exposures. The specific objectives were to (1) measure SEM/AVS ratios in a series of sodium sulfide (Na2S·9H2O)-amended sediments producing a range of sulfide concentrations and (2) measure responses of H. azteca (as mortality) in 96-h static sediment toxicity tests to exposures of Na2S-amended sediments. Amended sediments had a predictable increase in AVS concentrations and a concomitant decrease in ∑SEM/AVS ratios. Increasing concentrations of AVS resulted in a range of ∑SEM/AVS ratios that varied over more than an order of magnitude from 0.185 to 0.006. H. azteca survival decreased with increasing concentrations of “excess” AVS, with 96-h no observable effect concentration (NOEC) and LC50 of 0.041 and 0.019 ∑SEM/AVS, respectively. Clearly, the SEM/AVS model provides a useful tool for evaluating potential bioavailability of divalent metals and predicting ecological risk; however, this study demonstrates the need to consider sulfide (as AVS) as a potential source of toxicity in situations with low [<<1] ∑SEM/AVS ratios.

Influence of commercial (Fluka) naphthenic acids on acid volatile sulfide (AVS) production and divalent metal precipitation.

Energy-derived waters containing naphthenic acids (NAs) are complex mixtures often comprising a suite of potentially problematic constituents (e.g. organics, metals, and metalloids) that need treatment prior to beneficial use, including release to receiving aquatic systems. It has previously been suggested that NAs can have biostatic or biocidal properties that could inhibit microbially driven processes (e.g. dissimilatory sulfate reduction) used to transfer or transform metals in passive treatment systems (i.e. constructed wetlands). The overall objective of this study was to measure the effects of a commercially available (Fluka) NA on sulfate-reducing bacteria (SRB), production of sulfides (as acid-volatile sulfides [AVS]), and precipitation of divalent metals (i.e. Cu, Ni, Zn). These endpoints were assessed following 21-d aqueous exposures of NAs using bench-scale reactors. After 21-days, AVS molar concentrations were not statistically different (p<0.0001; α=0.05) among NA treatments (10, 20, 40, 60, and 80mg NA/L) and an untreated control (no NAs). Extent of AVS production was sufficient in all NA treatments to achieve ∑SEM:AVS <1, indicating that conditions were conducive for treatment of metals, with sulfide ligands in excess of SEM (Cu, Ni, and Zn). In addition, no adverse effects to SRB (in terms of density, relative abundance, and diversity) were measured following exposures of a commercial NA. In this bench-scale study, dissimilatory sulfate reduction and subsequent metal precipitation were not vulnerable to NAs, indicating passive treatment systems utilizing sulfide production (AVS) could be used to treat metals occurring in NAs affected waters.