RESUMEN
An environmental risk assessment for alcohol ethoxylates (AE) is presented that integrates wastewater treatment plant monitoring, fate, and ecotoxicity research with a new application of mixture toxicity theory based on simple similar concentration addition of AE homologs in a species-sensitivity distribution (SSD) context. AEs are nonionic surfactants composed of a homologous series of molecules that range in alkyl chain length from 12 to 18 carbons and ethoxylates from 0 to 18 units. Chronic ecotoxicity of AE is summarized for 17 species in 60 tests and then normalized to monitoring data for AE mixtures. To do so, chronic aquatic toxicity was first expressed as EC10 per species (the concentration predicted to cause a 10% reduction in an important ecological endpoint). Normalization integrated several new quantitative structure-activity relationships for algae, daphnids, fish, and mesocosms and provided an interpretation of toxicity test data as a function of individual homologs in an AE mixture. SSDs were constructed for each homolog and the HC5 (hazardous concentration protective of 95% of species based on a small biological effect [the chronic EC10]) was predicted. Total mass of AE in monitored effluents from 29 sites in Europe, Canada, and the United States averaged 6.8, 2.8, and 3.55 microg/L, respectively. For risk assessment purposes, correction of exposure to account for fatty alcohol derived from sources other than AE and for sorbed components based on experimental evidence was used to determine AE concentrations in undiluted (100%) effluents from North America and Europe. Exposure and effect findings were integrated in a toxic unit (TU)-based model that considers the measured distribution of individual AE homologs in effluent with their corresponding SSDs. Use of environmentally relevant exposure corrections (bioavailability and accounting for AE-derived alcohol) resulted in TUs ranging from 0.015 to 0.212. Low levels of risk are concluded for AE in the aquatic environments of Europe and North America.
Asunto(s)
Alcoholes/toxicidad , Contaminantes Químicos del Agua/toxicidad , Adsorción , Alcoholes/análisis , Algoritmos , Animales , Biodegradación Ambiental , Daphnia , Eucariontes , Europa (Continente) , Peces , América del Norte , Relación Estructura-Actividad Cuantitativa , Valores de Referencia , Medición de Riesgo , Especificidad de la Especie , Terminología como Asunto , Microbiología del Agua , Contaminantes Químicos del Agua/análisisRESUMEN
Traditionally, ecotoxicity quantitative structure-activity relationships (QSARs) for alcohol ethoxylate (AE) surfactants have been developed by assigning the measured ecotoxicity for commercial products to the average structures (alkyl chain length and ethoxylate chain length) of these materials. Acute Daphnia magna toxicity tests for binary mixtures indicate that mixtures are more toxic than the individual AE substances corresponding with their average structures (due to the nonlinear relation of toxicity with structure). Consequently, the ecotoxicity value (expressed as effects concentration) attributed to the average structures that are used to develop the existing QSARs is expected to be too low. A new QSAR technique for complex substances, which interprets the mixture toxicity with regard to the "ethoxymers" distribution (i.e., the individual AE components) rather than the average structure, was developed. This new technique was then applied to develop new AE ecotoxicity QSARs for invertebrates, fish, and mesocosms. Despite the higher complexity, the fit and accuracy of the new QSARs are at least as good as those for the existing QSARs based on the same data set. As expected from typical ethoxymer distributions of commercial AEs, the new QSAR generally predicts less toxicity than the QSARs based on average structure.
Asunto(s)
Alcoholes/toxicidad , Contaminación Ambiental/análisis , Tensoactivos/toxicidad , Contaminantes Químicos del Agua/toxicidad , Algoritmos , Animales , Cromatografía Líquida de Alta Presión , Daphnia , Peces , Modelos Estadísticos , Relación Estructura-Actividad CuantitativaRESUMEN
Alcohol ethoxylates (AEs) are an important group of nonionic surfactants. Commercial AEs consist of a mixture of several homologues of varying carbon chain length (Cx) and degree of ethoxylation (EOy). The major disposal route of AE is down the drain to municipal wastewater treatment plants that discharge into receiving surface waters. Sorption of AE homologues onto activated sludge and river water solids is an important factor in assessing exposure of AE in the environment. This study presents the experimental determination of sorption coefficients for a wide array of AE homologues including five alcohols under environmentally relevant conditions and combines these data with literature data to generate a predictive model for the sorption of AEs in the environment. These results demonstrate that sorption can be effectively modeled using a log Kd vs. Cx and EOy predictive equation having the form log Kd = 0.331C - 0.00897EO - 1.126(R2 = 0.64).
Asunto(s)
Alcoholes/análisis , Alcoholes Grasos/análisis , Aguas del Alcantarillado/análisis , Contaminantes Químicos del Agua/análisis , Adsorción , Biodegradación Ambiental , Fenómenos Químicos , Química Física , Monitoreo del Ambiente , Predicción , Agua Dulce/análisis , Modelos Lineales , Modelos Estadísticos , Eliminación de Residuos , Medición de Riesgo , Termodinámica , Eliminación de Residuos LíquidosRESUMEN
Bisphenol A (BPA) (CAS 80-05-7) was analyzed in receiving waters upstream and downstream of US manufacturers (1996 and 1997) and processors (1997) during seasonal low flow periods. BPA was not detected (< 1 microgram/l) in any surface water sample in 1996 or at six of seven sites in 1997. Concentrations near the seventh site ranged from 2 to 8 micrograms/l; however, its receiving stream had no measurable flow and concentrations represent undiluted effluent. All surface water concentrations from this and other studies were less than the freshwater predicted no effect concentration (PNEC) of 64 micrograms/l, suggesting that BPA discharges from manufacturing and processing facilities to surface water do not pose an environmental concern.
Asunto(s)
Fenoles/análisis , Contaminantes Químicos del Agua/análisis , Compuestos de Bencidrilo , Industrias , Control de Calidad , Estados UnidosRESUMEN
Ecotoxicity methods were used to assess different soil and oil combinations before, during and after laboratory bioremediation with associated hydrocarbon analysis. Heavy, medium and light crude oil (API gravity 14, 30, and 55) was spiked (ca. 5% w/w) into two sandy soils in the laboratory having organic carbon concentrations of 0.3 (Norwood) and 4.7% (Norwood/Baccto). The earthworm (Eisenia fetida) 14-d lethality assay, the modified Microbics Microtox Solid-Phase assay, and the 14-d plant seed germination and growth assays using corn, wheat and oats, were spiked and tested during a 360-d laboratory remediation. Eisenia was the most sensitive of the three methods utilized with survival increasing throughout bioremediation with fastest toxicity reduction in the high carbon Norwood/Baccto soils where LC50's were 100% or greater at the end of 90-d whereas, > 150-d were required to achieve a similar result in the low carbon soil. Analysis of the undiluted treatments with oily soil alone showed that earthworm survival was high after 90-d in all high organic carbon soils, and after eight months in the low carbon soils, except for the Norwood soil-light oil treatment, which required 360-d to achieve 100% survival. The Microtox assay was less sensitive with EC50's 100% or greater observed after 90-d in high carbon soils and after 240-d for all low carbon soils. After bioremediation, no effects on seed germination were observed, although some plant growth inhibition effects remained. There was no direct correlation between total petroleum hydrocarbon concentrations and toxicity.
Asunto(s)
Monitoreo del Ambiente/métodos , Aceites Combustibles/análisis , Contaminantes del Suelo/análisis , Administración de Residuos , Animales , Ecología , Aceites Combustibles/toxicidad , Concentración de Iones de Hidrógeno , Oligoquetos , Desarrollo de la Planta , Plantas/efectos de los fármacos , Sensibilidad y Especificidad , Contaminantes del Suelo/toxicidad , Estados UnidosRESUMEN
Effects of a homologous series of three primarily linear alcohol ethoxylate surfactants were studied in laboratory flow-through 28-day early-life-stage tests with fathead minnow (Pimephales promelas Rafinesque). Surfactants were a C(9-11), C(12-13), and C(14-15) with an average of 6, 6.5, and 7 ethylene oxide units per mole of alcohol, respectively. Average measured surfactant recoveries were 103%, 81%, and 79% of nominal concentrations for the C(9-11) EO 6, C(12-13) EO 6.5, and C(14-15) EO 7 studies, respectively. Embryo survival at 48 h was not adversely affected at any of the concentrations tested. Impaired hatching and deformed fry were observed only in the C(12-13) EO 6.5 study. The 28-day LC50 values were 4.87, 2.39, and 1.02 mg/L for the C(9-11) EO 6, C(12-13) EO 6.5, and C(14-15) EO 7 surfactants, respectively. The corresponding NOECs for survival were 1.01, 1.76, and 0.74 mg/L. Posthatch fry growth was more sensitive than survival for the C(12-13) EO 6.5 and C(14-15) EO 7 surfactants. Survival of posthatch fry decreased with increasing surfactant alkyl chain length. Twenty-eight-day laboratory data were compared to 96-h laboratory, 10-day laboratory and 30-day stream mesocosm data for fathead minnow previously determined for these surfactants. Survival endpoints from the different exposures were comparable and only varied within a factor of two. Similarity of results suggests that it is possible to effectively use 96-h, 10-day, or 28-day laboratory data to predict environmental effects concentrations of these surfactants for fish. http://link.springer-ny. com/link/service/journals/00244/bibs/37n4p536.html
Asunto(s)
Cyprinidae , Óxido de Etileno/toxicidad , Tensoactivos/toxicidad , Alcoholes/toxicidad , Animales , Cyprinidae/embriología , Embrión no Mamífero/efectos de los fármacos , Óxido de Etileno/análogos & derivados , Concentración de Iones de Hidrógeno , Relación Estructura-Actividad , Temperatura , Pruebas de Toxicidad/métodosRESUMEN
Two microcosm-scale wetlands (570-liter containers) were integratively designed and constructed to investigate transfers and transformations of zinc associated with an aqueous matrix, and to provide future design parameters for pilot-scale constructed wetlands. The fundamental design of these wetland microcosms was based on biogeochemical principles regulating fate and transformations of zinc (pH, redox, etc.). Each wetland consisted of a 45-cm hydrosoil depth inundated with 25 cm of water, and planted with Scirpus californicus. Zinc ( approximately 2 mg/liter) as ZnCl2 was amended to each wetland for 62 days. Individual wetland hydraulic retention times (HRT) were approximately 24 h. Total recoverable zinc was measured daily in microcosm inflow and outflows, and zinc concentrations in hydrosoil and S. californicus tissue were measured pre- and post-treatment. Ceriodaphnia dubia and Pimephales promelas7-day aqueous toxicity tests were performed on wetland inflows and outflows, and Hyalella azteca whole sediment toxicity tests (10-day) were performed pre- and post-treatment. Approximately 75% of total recoverable zinc was transferred from the water column. Toxicity decreased from inflow to outflow based on 7-day C. dubia tests, and survival of H. azteca in hydrosoil was >80%. Data illustrate the ability of integratively designed wetlands to transfer and sequester zinc from the water column while concomitantly decreasing associated toxicity.
Asunto(s)
Ecosistema , Plantas/metabolismo , Eliminación de Residuos Líquidos/métodos , Contaminantes Químicos del Agua/metabolismo , Purificación del Agua/métodos , Zinc/metabolismo , Animales , Biotransformación , Chironomidae/efectos de los fármacos , Crustáceos/efectos de los fármacos , Oxidación-Reducción , Suelo/análisis , Tasa de Supervivencia , Pruebas de Toxicidad , Eliminación de Residuos Líquidos/instrumentación , Contaminantes Químicos del Agua/toxicidad , Purificación del Agua/instrumentación , Zinc/toxicidadRESUMEN
Responses of aquatic invertebrates to 30-day exposures to a nonionic linear alcohol ethoxylate (LAE) surfactant (C12-13AE-6.5) were evaluated in 10 outdoor stream mesocosms. Responses were measured as changes in invertebrate densities and invertebrate drift densities during a 14-day pretreatment period, a 30-day treatment period, and a 14-day posttreatment period relative to untreated control stream densities. Mean measured surfactant concentrations in duplicate streams were 0.32, 0.88, 1.99, and 5.15 mg LAE/liter, with two streams serving as untreated controls. Statistically significant effects were observed on simulid, copepod, and cladoceran population densities during the treatment period. Based on these effects, the no-observed-effect concentration (NOEC) for invertebrate densities was <0.32 mg LAE/liter and the lowest-observed-effect concentration (LOEC) was 0.32 mg LAE/liter. No statistically significant differences due to treatment were detected in drifting invertebrates; however, a trend was observed with increased numbers of invertebrates drifting in the streams treated with 5.15 mg LAE/liter as compared with controls.
Asunto(s)
Alcoholes/efectos adversos , Ecosistema , Glicoles de Etileno/efectos adversos , Agua Dulce/química , Invertebrados/efectos de los fármacos , Contaminantes Químicos del Agua/efectos adversos , Análisis de Varianza , AnimalesRESUMEN
Bisphenol A (CAS 85-05-7) may be released into the environment through its use and handling, and permitted discharges. BPA is moderately soluble (120 to 300 mg/L at pH 7), may adsorb to sediment (Koc 314 to 1524), has low volatility, and is not persistent based on its rapid biodegradation in acclimated wastewater treatment plants and receiving waters (half-lives 2.5 to 4 days). BPA is "slightly to moderately" toxic (algal EC50 of 1000 micrograms/L) and has low potential for bioaccumulation in aquatic organisms (BCFs 5 to 68). The chronic NOEC for Daphnia magna is > 3146 micrograms/L. Surface water concentrations are at least one to several orders of magnitude lower than chronic effects, with most levels nondetected.
Asunto(s)
Contaminantes Ocupacionales del Aire/química , Contaminantes Ambientales/análisis , Fenoles/química , Contaminantes Ocupacionales del Aire/toxicidad , Animales , Compuestos de Bencidrilo , Biodegradación Ambiental , Contaminantes Ambientales/toxicidad , Semivida , Humanos , Fenoles/toxicidad , Eliminación de Residuos Líquidos , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/toxicidadRESUMEN
Two pilot-scale wetland cells (6.1 x 30.5 m) were integratively designed and constructed to emphasize and enhance transfers and transformations of selected metals (Cu, Pb, and Zn) in an aqueous matrix. A series of preliminary experiments and analyses were conducted to select macrofeatures (hydroperiod, hydrosoil, and vegetation) of the constructed wetland system. These wetland cells were designed to operate in series or parallel with nominal hydraulic retention times of 24-48 hr, respectively. With water at a depth of 30 cm, both wetland cells had hydrosoil (45 cm) planted with Scirpus californicus. After 250 days of wetland operation, average hydrosoil redox potentials in each wetland cell decreased from +90 mV to -165 mV, and average plant height increased from 0.3 to 2.7 m. Aqueous samples were collected over a 4.5-month period at the inflow and outflow sites of the wetland cells. Average inflow concentrations of total recoverable Cu, Pb, and Zn were 22.4, 10.5, and 565.9 micrograms/L, respectively. After a 46-hr HRT, average outflow concentrations of total recoverable Cu, Pb, and Zn were 15, 2.2, and 85.9 micrograms/L, resulting in removals of 33, 79, and 85%, respectively. Initial results suggest that these constructed wetlands can be designed to remove targeted metals in wastewater.
Asunto(s)
Residuos Industriales/análisis , Metales , Petróleo , Administración de Residuos/métodos , Contaminantes Químicos del Agua , Oxidación-Reducción , Proyectos Piloto , Plantas/química , Plantas/metabolismo , Suelo/análisisRESUMEN
Fish, benthic macroinvertebrate, and plant responses to 30-day exposures of C14-15 linear alcohol ethoxylate surfactant with an average of 7 mol of ethylene oxide (LAE) were measured in flowthrough stream mesocosms. Replicate stream mesocosms were treated in two experiments with concentrations of LAE ranging from 80 to 550 microg/liter. Macroinvertebrates were relatively insensitive with the exception of Simuliidae density which was significantly affected at 160 microg/liter. Fathead minnow (Pimephales promelas R.) reproduction was significantly reduced at >280 microg/liter and larval survival decreased significantly at 330 microg/liter. Growth and mortality of bluegill sunfish (Lepomis macrochirus L.) were not affected at the highest exposure concentration of 330 microg/liter in the first experiment. No ecologically significant effects were observed for vascular aquatic plants or periphyton. The laboratory and stream mesocosm results were similar with NOECs ranging between 80 and 550 microg/liter surfactant. The study provided data for an improved risk assessment of this nonionic surfactant, by reducing the uncertainty associated with extrapolation from laboratory data.
Asunto(s)
Óxido de Etileno/toxicidad , Tensoactivos/toxicidad , Contaminantes Químicos del Agua/toxicidad , Animales , Peces/metabolismo , Agua Dulce , Invertebrados/efectos de los fármacos , Invertebrados/metabolismo , Dosificación Letal Mediana , Plantas/efectos de los fármacos , Plantas/metabolismo , Pruebas de Toxicidad , Contaminantes Químicos del Agua/análisisRESUMEN
A series of 12 outdoor model stream mesocosms was designed to evaluate the effects of chemicals and mixtures on the biota in stream ecosystems. An integrated design plan incorporated physical, chemical, and biological factors as well as the specific experimental objectives and effects parameters to be evaluated. Analysis of biological assemblages such as macroinvertebrates and periphyton in the model stream mesocosms demonstrated the presence of diverse and sensitive taxa. These model stream mesocosms also included the ability to evaluate responses of sentinel fish species such as Pimephales promelas and Lepomis macrochirus as well as macrophytes. The design and construction of the stream are discussed in detail and a brief description of a typical experimental protocol is provided. Experiments, to date, have spanned 14-30 days pretreatment "colonization" with 30 days of treatment and 15 days of posttreatment observation. Precision and accuracy of test chemical delivery to the stream have been excellent and the overall experimental design has been useful for delivering threshold toxicity concentrations and evaluating ecosystem potency for the chemicals tested.