Laboratory-scale evaluation of algaecide effectiveness for control of microcystin-producing cyanobacteria from Lake Okeechobee, Florida (USA).

Growth of microcystin-producing cyanobacteria in Lake Okeechobee (Florida, USA) and surrounding waters has resulted in adverse health impacts for humans and endangered species, as well as significant economic losses. As these issues worsen, there is growing pressure for efficacious solutions to rapidly mitigate harmful algal blooms (HABs) and protect critical freshwater resources. Applications of USEPA-registered algaecides as management tactics meet many decision-making criteria often required by water resource managers (e.g., effective, scalable, selective), but have not yet been evaluated on a large scale within the Lake Okeechobee waterway. This study was conducted to bolster the peer-reviewed database for available management tactics against microcystin-producing cyanobacteria in waters of this region. Laboratory-scale experiments can be conducted first to minimize uncertainty at larger scales and improve confidence in decision-making. In this study, samples containing microcystin-producing cyanobacteria collected from Lake Okeechobee were exposed to several USEPA-registered algaecides in laboratory toxicity experiments. Responses of target cyanobacteria were measured 3 days after treatment (DAT) in terms of cell density, chlorophyll-a concentrations, and phycocyanin concentrations. Based on responses of the cyanobacteria, minimum effective exposure concentrations were identified for each algaecide. Microcystin release (i.e. proportion of total microcystins in the aqueous phase) was measured and compared 1 DAT among effective exposures. Total microcystin concentrations were measured in effective treatments at 1, 4, and 9 DAT to discern potential for microcystin persistence following exposures to the effective formulations and exposure concentrations. Overall, several formulations including GreenClean Liquid® 5.0, GreenClean Liquid® 5.0 combined with Hydrothol® 191, and the copper-based algaecides evaluated (Algimycin® PWF, Argos, Captain® XTR, Cutrine® Ultra, and SeClear®) achieved significant and similar effects on target cyanobacteria. The chelated copper-based formulations (Algimycin® PWF, Argos, Captain® XTR, and Cutrine® Ultra) resulted in relatively less microcystin release 1 DAT and lesser total microcystin concentrations 4 DAT. At 9 DAT, total microcystin concentrations were significantly lower than in untreated controls in all treatments evaluated. These results provide the necessary comparative performance data for preliminary decision-making and designing additional studies at larger scales. Importantly, the comparative toxicity data and approach provided in this study demonstrate the initial steps for development of site-specific management strategies for Lake Okeechobee and other areas impacted by harmful algal blooms with large spatial and temporal scales.

Relationship among aqueous copper half-lives and responses of Pimephales promelas to a series of copper sulfate pentahydrate concentrations.

Copper algaecide exposures in situ are often of shorter duration than exposures for static toxicity experiments because aqueous concentrations in situ dissipate as a function of site-specific fate processes. Consequently, responses of organisms to static copper exposures may overestimate effects following in situ exposures. To understand the role of exposure duration for altering responses, Pimephales promelas survival was compared following static (96 h) and pulse (1.5, 4, 8, and 15 h half-lives) exposures of CuSO4•5H2O. Copper concentrations sorbed by fry indicated a consequence of different exposures. Responses of P. promelas to static exposures resulted in 96 h LC50s of 166 µgCu/L (95% confidence interval [CI], 142-189 µgCu/L) as soluble copper and 162 µgCu/L (CI, 140-183 µgCu/L) as acid soluble copper. Relative to static 96 h LC50s, exposures with half-lives of 1.5, 4 and 8 h resulted in LC50s 10, 3 and 2 times greater, respectively, for responses measured 96 h after exposure initiation. Copper concentrations extracted from fry exposed for 1.5, 4 and 8 h half-lives were less than the static experiment. However, copper sorbed by fry in the 15 h half-life experiment was not different than the static experiment. The relationship between 96 h LC50 and 1/half-life was expressed using the equations y = 116 + 1360 × (R2 = 0.97) for soluble copper and y = 147 + 1620 × (R2 = 0.98) for acid soluble copper. Incorporation of exposure duration for predictions of P. promelas responses to copper pulse exposures increases prediction accuracy by an order of magnitude.

Cell density dependence of Microcystis aeruginosa responses to copper algaecide concentrations: Implications for microcystin-LR release.

Along with mechanistic models, predictions of exposure-response relationships for copper are often derived from laboratory toxicity experiments with standardized experimental exposures and conditions. For predictions of copper toxicity to algae, cell density is a critical factor often overlooked. For pulse exposures of copper-based algaecides in aquatic systems, cell density can significantly influence copper sorbed by the algal population, and consequent responses. A cyanobacterium, Microcystis aeruginosa, was exposed to a copper-based algaecide over a range of cell densities to model the density-dependence of exposures, and effects on microcystin-LR (MC-LR) release. Copper exposure concentrations were arrayed to result in a gradient of MC-LR release, and masses of copper sorbed to algal populations were measured following exposures. While copper exposure concentrations eliciting comparable MC-LR release ranged an order of magnitude (24-h EC50s 0.03-0.3mg Cu/L) among cell densities of 106 through 107 cells/mL, copper doses (mg Cu/mg algae) were similar (24-h EC50s 0.005-0.006mg Cu/mg algae). Comparisons of MC-LR release as a function of copper exposure concentrations and doses provided a metric of the density dependence of algal responses in the context of copper-based algaecide applications. Combined with estimates of other site-specific factors (e.g. water characteristics) and fate processes (e.g. dilution and dispersion, sorption to organic matter and sediments), measuring exposure-response relationships for specific cell densities can refine predictions for in situ exposures and algal responses. These measurements can in turn decrease the likelihood of amending unnecessary copper concentrations to aquatic systems, and minimize risks for non-target aquatic organisms.

Influence of CuSO4 and chelated copper algaecide exposures on biodegradation of microcystin-LR.

Copper exposures from algaecide applications in aquatic systems are hypothesized to impede bacterial degradation of microcystin (MC), a cyanobacterial produced hepatotoxin. Despite regulatory implications of this hypothesis, limited data exist on influences of copper-exposures on MC-degrading bacteria and consequent MC-degradation. In this study, influences of copper-algaecide concentrations and formulations on bacterial composition and microcystin-LR (MCLR) degradation were investigated. Microcystis aeruginosa was exposed to four concentrations (0-5.0 mg Cu L-1) of three copper-algaecide formulations, and rates and extents of MCLR degradation were measured. In untreated controls and following exposures of 0.1, 0.5, and 1.0 mg Cu L-1, MCLR concentrations decreased at a rate of ∼41-53 µg MCLR/L d-1. Following exposure to 5.0 mg Cu L-1 MCLR degradation rates decreased an order of magnitude to ∼3-7 µg MCLR/L d-1. Bacterial diversity decreased following copper-exposures greater than 0.1 mg Cu L-1 for all formulations. Relative abundance of certain groups of MC-degrading bacteria identified in treatments increased with increasing copper concentration, suggesting they may be less sensitive to copper exposures than other, MCLR and non MC-degrading heterotrophic bacteria present in the assemblage. Results from this study revealed that copper concentration can influence degradation rates of MCLR, however this influence was not significant within copper concentrations currently registered for use (≤1.0 mg Cu L-1) of the tested algaecides. Copper formulation did not significantly alter degradation rates or bacterial composition. These data augment our understanding of the influences of copper algaecide-exposures on MCLR degradation, and can be used to inform more accurate risk evaluations and use of copper-algaecides for management of MCLR-producing cyanobacteria.

A risk-based approach for identifying constituents of concern in oil sands process-affected water from the Athabasca Oil Sands region.

Mining leases in the Athabasca Oil Sands (AOS) region produce large volumes of oil sands process-affected water (OSPW) containing constituents that limit beneficial uses and discharge into receiving systems. The aim of this research is to identify constituents of concern (COCs) in OSPW sourced from an active settling basin with the goal of providing a sound rational for developing mitigation strategies for using constructed treatment wetlands for COCs contained in OSPW. COCs were identified through several lines of evidence: 1) chemical and physical characterization of OSPW and comparisons with numeric water quality guidelines and toxicity endpoints, 2) measuring toxicity of OSPW using a taxonomic range of sentinel organisms (i.e. fish, aquatic invertebrates, and a macrophyte), 3) conducting process-based manipulations (PBMs) of OSPW to alter toxicity and inform treatment processes, and 4) discerning potential treatment pathways to mitigate ecological risks of OSPW based on identification of COCs, toxicological analyses, and PBM results. COCs identified in OSPW included organics (naphthenic acids [NAs], oil and grease [O/G]), metals/metalloids, and suspended solids. In terms of species sensitivities to undiluted OSPW, fish ≥ aquatic invertebrates > macrophytes. Bench-scale manipulations of the organic fractions of OSPW via PBMs (i.e. H2O2+UV254 and granular activated charcoal treatments) eliminated toxicity to Ceriodaphnia dubia (7-8 d), in terms of mortality and reproduction. Results from this study provide critical information to inform mitigation strategies using passive or semi-passive treatment processes (e.g., constructed treatment wetlands) to mitigate ecological risks of OSPW to aquatic organisms.

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.

Effects of environmental conditions on aerobic degradation of a commercial naphthenic acid.

Naphthenic acids (NAs) are problematic constituents in energy-derived waters, and aerobic degradation may provide a strategy for mitigating risks to aquatic organisms. The overall objective of this study was to determine the influence of concentrations of N (as ammonia) and P (as phosphate), and DO, as well as pH and temperatures on degradation of a commercial NA in bench-scale reactors. Commercial NAs provided replicable compounds necessary to compare influences of environmental conditions on degradation. NAs were quantified using high performance liquid chromatography. Microbial diversity and relative abundance were measured in treatments as explanatory parameters for potential effects of environmental conditions on microbial populations to support analytically measured NA degradation. Environmental conditions that positively influenced degradation rates of Fluka NAs included nutrients (C:N 10:1-500:1, C:P 100:1-5000:1), DO (4.76-8.43 mg L(-1)), pH (6-8), and temperature (5-25 °C). Approximately 50% removal of 61 ± 8 mg L(-1) was achieved in less than 2 d after NA introduction, achieving the method detection limit (5 mg L(-1)) by day 6 of the experiment in treatments with a C:N:P ratio of 100:10:1, DO > 8 mg L(-1), pH ∼8-9, and temperatures >23 °C. Microbial diversity was lowest in lower temperature treatments (6-16 °C), which may have resulted in observed slower NA degradation. Based on results from this study, when macro- and micronutrients were available, DO, pH, and temperature (within environmentally relevant ranges) influenced rates of aerobic degradation of Fluka NAs. This study could serve as a model for systematically evaluating environmental factors that influence NA degradation in field scenarios.

Comparative toxicity of sodium carbonate peroxyhydrate to freshwater organisms.

Sodium carbonate peroxyhydrate (SCP) is a granular algaecide containing H2O2 as an active ingredient to control growth of noxious algae. Measurements of sensitivities of target and non-target species to hydrogen peroxide are necessary for water resource managers to make informed decisions and minimize risks for non-target species when treating noxious algae. The objective of this study was to measure and compare responses among a target noxious alga (cyanobacterium Microcystis aeruginosa) and non-target organisms including a eukaryotic alga (chlorophyte Pseudokirchneriella subcapitata), microcrustacean (Ceriodaphnia dubia), benthic amphipod (Hyalella azteca), and fathead minnow (Pimephales promelas) to exposures of hydrogen peroxide as SCP. Hydrogen peroxide exposures were confirmed using the I3(-) method. SCP margins of safety for these organisms were compared with published toxicity data to provide context for other commonly used algaecides and herbicides (e.g. copper formulations, endothall, and diquat dibromide). Algal responses (cell density and chlorophyll a concentrations) and animal mortality were measured after 96h aqueous exposures to SCP in laboratory-formulated water to estimate EC50 and LC50 values, as well as potency slopes. Despite a shorter test duration, M. aeruginosa was more sensitive to hydrogen peroxide as SCP (96h EC50:0.9-1.0mgL(-)(1) H2O2) than the eukaryotic alga P. subcapitata (7-d EC50:5.2-9.2mgL(-1) H2O2), indicating potential for selective control of prokaryotic algae. For the three non-target animals evaluated, measured 96-h LC50 values ranged from 1.0 to 19.7mgL(-1) H2O2. C. dubia was the most sensitive species, and the least sensitive species was P. promelas, which is not likely to be affected by concentrations of hydrogen peroxide as SCP that would be used to control noxious algae (e.g. M. aeruginosa). Based on information from peer-reviewed literature, other algaecides could be similarly selective for cyanobacteria. Of the algaecides compared, SCP can selectively mitigate risks associated with noxious cyanobacterial growths (e.g. M. aeruginosa), with an enhanced margin of safety for non-target species (e.g. P. promelas).

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.

Cellular and aqueous microcystin-LR following laboratory exposures of Microcystis aeruginosa to copper algaecides.

Microcystin release from algal cells influences use of copper-algaecides in water resources. Accurate data regarding relationships between copper-algaecide exposures and responses of microcystin-producing algae are needed to make informed management decisions. Responses of Microcystis aeruginosa were measured in terms of cellular microcystin-LR (MC-LR), aqueous MC-LR, and chlorophyll-a following exposure to CuSO4 and copper-ethanolamine. Comparisons were made between treated and untreated samples, and copper formulations. EC50s and slopes for M. aeruginosa responses to copper exposures were calculated. Algal responses followed a sigmoidal exposure-response relationship, and cellular MC-LR and chlorophyll-a were negatively related to copper concentrations. Aqueous MC-LR increased with copper concentrations, although the increase in aqueous MC-LR was not proportional to decreases in cellular MC-LR and chlorophyll-a. Cellular MC-LR and chlorophyll a declined at a greater rate than aqueous MC-LR increased. Total MC-LR was less than untreated controls following copper exposure. Differences were measured between copper formulations in terms of aqueous and total MC-LR concentrations at concentrations of 0.5 and 1.0 mg Cu L-1. Aqueous and total MC-LR were greater (10-20%) following exposure to CuSO4 compared to copper-ethanolamine one day following exposure. The positive relationship between copper concentration and aqueous MC-LR at 0.07-1.0 mg Cu L-1 demonstrates that lower copper concentrations were as effective as higher concentrations in controlling M. aeruginosa while decreasing the total amount of MC-LR, and minimizing the proportion of MC-LR released to the aqueous-phase. Results serve to support more accurate risk evaluations of MC-LR concentrations when M. aeruginosa is exposed to copper-algaecides and when it is untreated.

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 simulated oilfield produced water on early seedling growth after treatment in a pilot-scale constructed wetland system.

Seed germination and early seedling growth bioassays were used to evaluate phytotoxicity of simulated oilfield produced water (OPW) before and after treatment in a subsurface-flow, pilot-scale constructed wetland treatment system (CWTS). Responses to untreated and treated OPW were compared among seven plant species, including three monocotyledons: corn (Zea mays), millet (Panicum miliaceum), and sorghum (Sorghum bicolor); and four dicotyledons: lettuce (Lactuca sativa), okra (Abelmoschus esculents), watermelon (Citrullus lanatus), and soybean (Glycine max). Phytotoxicity was greater in untreated OPW than in treated OPW. Exposures to untreated and treated OPW enhanced growth in some plant species (sorghum, millet, okra, and corn) relative to a negative control and reduced growth in other plant species (lettuce, soybean, and watermelon). Early seedling growth parameters indicated that dicotyledons were more sensitive to test waters compared to monocotyledons, suggesting that morphological differences between plant species affected phytotoxicity. Results indicated the following sensitivity scale for plant species: lettuce>soybean>watermelon>corn>okra≈millet>sorghum. Phytotoxicity of the treated OPW to lettuce and soybean, although concentrations of COCs were less than irrigation guideline concentrations, suggests that chemical characterization and comparison to guideline concentrations alone may not be sufficient to evaluate water for use in growing crops.

Evaluation of the utility of six measures for algal (Microcystis aeruginosa, Planktothrix agardhii and Pseudokirchneriella subcapitata) viability.

Standard algal toxicity tests are used to discern responses of algae to a variety of exposures including pesticides, personal care products and complex mixtures such as runoff and effluents. There are concerns regarding the accuracy, precision and utility of algal viability measures used as endpoints in algal toxicity test protocols. To definitively evaluate six algal viability measures, algae were heat-treated to produce known live:dead cell ratios. Cultures of two prokaryotic algae (Microcystis aeruginosa and Planktothrix agardhii) and a eukaryotic alga (Pseudokirchneriella subcapitata) were boiled for five minutes and mixed after cooling with untreated cultures to produce suspensions of 0%, 25%, 50%, 75% and 100% live algal cells. Optical microscopy was used to assess the viability of algae on a cell-by-cell basis by measuring cell density, uptake of a vital stain (neutral red) and exclusion of a mortal stain (erythrosin b). Aggregate measures of algal cell viability included chlorophyll a concentrations, pheophytin a concentrations and respiration (measured as 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyl tetrazolium formazan absorbance (INT)). Cell densities, erythrosin b stained cells and chlorophyll a concentrations correlated with viable M. aeruginosa, P. agardhii and P. subcapitata cells (R(2)=0.97-0.78, 0.98-0.85 and 0.99-0.97 respectively). Pheophytin a concentrations and neutral red stained cells did not correlate with viable algae (R(2)=0.41-0.01 and 0.15-0.03 respectively). For INT formazan absorbance, 50%, 75% and 100% viable algae had greater variances and did not strongly correlate (R(2)=0.75-0.54). This result was likely confounded by respiration associated with resident bacteria. Three of the six methods provided accurate and precise information regarding the viability of both prokaryotic and eukaryotic algae. These methods also have a relatively low initial expense and can be used widely.

Role of sediments in modifying the toxicity of two Roundup formulations to six species of larval anurans.

The role of sediment in modifying the toxicity of the original formulation of Roundup® and Roundup WeatherMAX® was examined in aqueous laboratory tests. Six species of anurans (Bufo fowleri, Hyla chrysoscelis, Rana catesbeiana, Rana clamitans, Rana sphenocephala, and Rana pipiens) were exposed at Gosner stage 25 to concentrations of the 2 herbicide formulations in 96-h, static, nonrenewal experiments in the presence and absence of sediment. All species tested had lower median lethal concentration values in water-only exposures of both formulations compared with exposures with sediment. Sediment significantly altered the potency slopes in all tests with the exceptions of H. chrysoscelis and R. clamitans when exposed to the original formulation of Roundup and H. chrysoscelis and R. sphenocephala when exposed to Roundup WeatherMAX. Thresholds were significantly different in all tests, including those in which potency slopes did not differ. Based on water-sediment exposures of the original formulation of Roundup, all 6 species tested had a margin of safety when compared with the predicted environmental concentration of the highest label application rate. Of the 6 species, 5 had a margin of safety when exposed to Roundup WeatherMAX. During incidental exposures in the field, sediments and organic matter present in aquatic systems provide significant sources of environmental ligands. If used according to label instructions, both herbicides should pose minimal risk to anuran amphibians in actual field applications. Environ Toxicol Chem 2014;33:2616-2620. © 2014 SETAC.

Treatment of oil and grease in produced water by a pilot-scale constructed wetland system using biogeochemical processes.

Constructed wetland treatment systems (CWTSs) can effectively remove many constituents that limit beneficial use of oilfield produced water. The objectives of this investigation were: (1) to assess the effect of mass loadings of oil and grease (O & G) on treatment performance in pilot-scale subsurface flow and free water surface CWTS series having sequential reducing and oxidizing cells, and (2) to evaluate effects on treatment performance of adding a pilot-scale oil-water separator. Increase in O & G mass loading from 5 to 20 mg min(-1) caused decreases in both dissolved oxygen concentration and sediment redox potential, which affected treatment performance. Biogeochemical pathways for removal of O & G, iron, and manganese operate under oxidizing conditions, and removal rate coefficients for these constituents decreased (0.905-0.514 d(-1) for O & G, 0.773-0.452 d(-1) for iron, and 0.970-0.518 d(-1) for manganese) because greater mass loading of O & G promoted reducing conditions. With increased mass loading, removal rate coefficients for nickel and zinc increased from 0.074 to 0.565 d(-1) and from 0.196 to 1.08 d(-1), respectively. Although the sequential reducing and oxidizing cells in the CWTS were very effective in treating the targeted constituents, an oil-water separator was added prior to wetland cells to enhance O & G removal at high inflow concentration (100 mg L(-1)). The oil-water separator removed approximately 50% of the O & G, and removal extents and efficiencies approximated those observed at 50 mg L(-1) inflow concentration during treatment without an oil-water separator.

Relative toxicity of the components of the original formulation of Roundup to five North American anurans.

The responses of five North American frog species that were exposed in an aqueous system to the original formulation of Roundup were compared. Carefully designed and un-confounded laboratory toxicity tests are crucial for accurate assessment of potential risks from the original formulation of Roundup to North American amphibians in aquatic environments. The formulated mixture of this herbicide as well as its components, isopropylamine (IPA) salt of glyphosate and the surfactant MON 0818 (containing polyethoxylated tallowamine (POEA)) were separately tested in 96 h acute toxicity tests with Gosner stage 25 larval anurans. Rana pipiens, R. clamitans, R. catesbeiana, Bufo fowleri, and Hyla chrysoscelis were reared from egg masses and exposed to a series of 11 concentrations of the original formulation of Roundup herbicide, nine concentrations of MON 0818 and three concentrations of IPA salt of glyphosate in static (non-renewal) aqueous laboratory tests. LC50 values are expressed as glyphosate acid equivalents (ae) or as mg/L for MON 0818 concentrations for comparison between the formulation and components. R. pipiens was the most sensitive of five species with 96 h-LC50 values for formulation tests, for the five species, ranging from 1.80 to 4.22 mg ae/L, and MON 0818 exposures with 96 h-LC50 values ranging from 0.68 to 1.32 mg/L. No significant mortality was observed during exposures of 96 h for any of the five species exposed to glyphosate IPA salt at concentrations up to 100 times the predicted environmental concentration (PEC). These results agree with previous studies which have noted that the surfactant MON 0818 containing POEA contributes the majority of the toxicity to the herbicide formulations for fish, aquatic invertebrates, and amphibians. These study results suggest that anurans are among the most sensitive species, and emphasize the importance of testing the herbicide formulation in addition to its separate components to accurately characterize the toxicity and potential risk of the formulation.

Comparative toxicity of two glyphosate formulations (original formulation of Roundup® and Roundup WeatherMAX®) to six North American larval anurans.

The toxicity of two glyphosate formulations (the original formulation of Roundup® and Roundup WeatherMAX®) to six species of North American larval anurans was evaluated by using 96-h static, nonrenewal aqueous exposures. The 96-h median lethal concentration values (LC50) ranged from 1.80 to 4.22 mg acid equivalent (ae)/L and 1.96 to 3.26 mg ae/L for the original formulation of Roundup and Roundup WeatherMAX, respectively. Judged by LC50 values, four species were more sensitive to Roundup WeatherMAX exposures, and two species were more sensitive to the original formulation. Two of six species, Bufo fowleri (p < 0.05, F = 14.89, degrees of freedom [df] = 1) and Rana clamitans (p < 0.05, F = 18.46, df = 1), had significantly different responses to the two formulations tested. Increased sensitivity to Roundup WeatherMAX likely was due to differences in the surfactants or relative amounts of the surfactants in the two formulations. Potency slopes for exposures of the original formulation ranged from 24.3 to 92.5% mortality/mg ae/L. Thresholds ranged from 1.31 to 3.68 mg ae/L, showing an approximately three times difference in the initiation of response among species tested. For exposures of Roundup WeatherMAX, slopes ranged from 49.3 to 84.2% mortality/mg ae/L. Thresholds ranged from 0.83 to 2.68 mg ae/L. Margins of safety derived from a simulated direct overspray were above 1, except for one species in exposures of Roundup WeatherMAX. Laboratory data based on aqueous exposures are conservative because of the lack of environmental ligands; however, these tests provide information regarding the relative toxicity between these two Roundup formulations.

Responses of Lyngbya magnifica Gardner to an algaecide exposure in the laboratory and field.

Predicting responses of organisms exposed to toxic materials in the field from results produced in laboratory studies and confirming those predictions has been a central question in aquatic toxicology since its inception. A field treatment of a cyanobacterium and laboratory measurements of responses to algaecide exposures provided an opportunity to address that question. This research involved predicting the response of Lyngbya magnifica to an algaecide exposure (Phycomycin SCP) in the laboratory and evaluating that prediction with a comparable exposure in the field. Based on the results from initial laboratory experiments, an effective algaecide and concentration (i.e. 92 mg Phycomycin SCP/g algae) were selected for field application in a farm pond. L. magnifica chlorophyll a and biomass were measured initially and 1, 4, 7, 10, and 21 days after treatment (DAT) for both laboratory and field exposures. Measurements of chlorophyll a decreases in the field treatment at 7, 10, and 21 days after treatment were significantly greater than responses obtained in similar laboratory exposures of Phycomycin SCP. Biomass was significantly decreased in the field at 21 DAT compared to laboratory measurements. This approach can be effective for site specific predictions and can provide valuable information for informed decisions regarding water resource management and should be included in a management plan for increased product efficiency and ecological safety.

A risk assessment approach to identifying constituents in oilfield produced water for treatment prior to beneficial use.

A risk assessment approach incorporating exposure pathways and calculated risk quotients was applied to identifying constituents requiring treatment prior to beneficial use of oilfield produced water (OPW). In this study, risk quotients are ratios of constituent concentrations in soil or water to guideline concentrations for no adverse effects to receptors. The risk assessment approach is illustrated by an example of an oilfield water produced from non-marine geologic strata of a rift basin in sub-Saharan Africa. The OPW studied has the following characteristics: 704-1370 mg L(-1) total dissolved solids (TDS), 45-48 mg L(-1) chloride, and 103.8 mg L(-1) oil and grease. Exposure pathways of constituents in OPW used for irrigation include: ingestion of plant tissue, ingestion and direct contact of irrigated soil by livestock, inhalation of aerosols or volatilized constituents, and ingestion of OPW directly by livestock. Applying risk quotient methods for constituents in soil and water, constituents of concern (COCs) identified for irrigation and livestock watering using the OPW studied include: iron (Fe), manganese (Mn), nickel (Ni), zinc (Zn), and oil and grease. Approximately 165,000 barrels d(-1) (26,233 m(3) d(-1)) of OPW from the study site are available for use. Identification of COCs and consideration of water quantity allows for development of reliable treatment design criteria to ensure effective and consistent treatment is achieved to meet guideline levels required for irrigation, livestock watering, or other uses. This study illustrates the utility of risk assessment for identifying the COCs in OPW for treatment, the level of treatment required, and viable options for use of the treated water.

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.