Spatial and temporal variation in toxicity and inorganic composition of hydraulic fracturing flowback and produced water.

Hydraulic fracturing for oil and gas extraction produces large volumes of wastewater, termed flowback and produced water (FPW), that are highly saline and contain a variety of organic and inorganic contaminants. In the present study, FPW samples from ten hydraulically fractured wells, across two geologic formations were collected at various timepoints. Samples were analyzed to determine spatial and temporal variation in their inorganic composition.

The Acute and Chronic Effects of a Sediment-Bound Synthetic Musk, Galaxolide, on Hyalella azteca, Chironomus dilutus, and Lumbriculus variegatus.

Galaxolide is one of the most frequently used synthetic polycyclic musks on the market and is commonly detected in aquatic waterways. Previous studies have mainly evaluated the toxicity of this emerging contaminant using water-only exposures; however, its high Log K (5.9) suggests that this compound is likely to partition to sediments.

Freshwater Sediment Toxicity Evaluation from Meso-Scale Spill Tests of Diluted Bitumen and Conventional Crude.

Oil and gas development and transportation in many areas of the world, such as the oil sands region of Alberta, Canada, are heavily monitored to minimize the environmental impacts of development and the risk of oil spills. However, oil spills to aquatic environments still occur. Although the science of oil spills has received considerable attention of late, uncertainty still remains in evaluating the fate and transport of oil spills as well as the effects of those spills on aquatic biota.

A complex bioaccumulation story in flowback and produced water from hydraulic fracturing: The role of organic compounds in inorganic accumulation in Lumbriculus variegatus.

Hydraulic fracturing creates large volumes of flowback and produced water (FPW). The waste is a complex mixture of organic and inorganic constituents. Although the acute toxicity of FPW to freshwater organisms has been studied, few have attempted to discern the interaction between organic and inorganic constituents within this matrix and its role in toxicity.

Understanding the effects of hydraulic fracturing flowback and produced water (FPW) to the aquatic invertebrate, Lumbriculus variegatus under various exposure regimes.

Hydraulic fracturing of horizontal wells is a cost effective means for extracting oil and gas from low permeability formations. Hydraulic fracturing often produces considerable volumes of flowback and produced water (FPW). FPW associated with hydraulic fracturing has been shown to be a complex, often brackish mixture containing a variety of anthropogenic and geogenic compounds.

Toxicity in aquatic model species exposed to a temporal series of three different flowback and produced water samples collected from a horizontal hydraulically fractured well.

In the present study, we compared the toxicity and associated chemical characterizations of flowback and produced water (FPW) collected from a single horizontal hydraulically fractured well at different time points during FPW production. Since few studies on whole mixture toxicity related to FPW exist, our aims were to determine both overall toxicity of the FPW mixture in a suite of organisms (Daphnia magna, Lumbriculus variegatus, Danio rerio, and Oncorhynchus mykiss) and also determine if toxicity changes depending on variation in FPW chemical properties as a function of time sampled (1.33, 72, and 228 h FPW samples collected immediately post-well production onset were analyzed in current study).

Developmental Toxicity of a Neonicotinoid Insecticide, Acetamiprid to Zebrafish Embryos.

Agricultural use of neonicotinoid insecticides is increasing worldwide, posing a risk to nontarget organisms. The present study investigated developmental toxicity of a widely used neonicotinoid, acetamiprid, to zebrafish embryos. Sublethal (malformations, hatchability, heart rate, body length, alteration of spontaneous movement and touch responses) and lethal effects were monitored during exposure period from 6 h post fertilization (hpf) to 120 hpf.

Identifying Organic Toxicants in Sediment Using Effect-Directed Analysis: A Combination of Bioaccessibility-Based Extraction and High-Throughput Midge Toxicity Testing.

Toxicity identification evaluation (TIE) and effect-directed analysis (EDA) were integrated to diagnose toxicity drivers in a complex system, such as sediment. In TIE manipulation, XAD resin was utilized as an amending agent for characterizing organic toxicants, which also facilitate a large-volume bioaccessibility-based extraction for EDA purposes. Both raw sediments in TIE and extract fractions in EDA were tested with Chironomus dilutus for toxicity using whole-sediment testing and a high-throughput microplate assay.

Improvements and cost-effective measures to the automated intermittent water renewal system for toxicity testing with sediments.

The push to make bioassays more sensitive has meant an increased duration of testing to look at more chronic endpoints. To conduct these longer bioassays through the use of traditional bioassay methods can be difficult, as many traditional bioassays have employed manual water changes, which take considerable time and effort. To that end, static-renewal systems were designed to provide researchers a technique to ease the manual water change burden.

Resolving the false-negative issues of the nonpolar organic amendment in whole-sediment toxicity identification evaluations.

Three common false-negative scenarios have been encountered with amendment addition in whole-sediment toxicity identification evaluations (TIEs): dilution of toxicity by amendment addition (i.e., not toxic enough), not enough amendment present to reduce toxicity (i.

Effect-Directed Analysis of Toxicants in Sediment with Combined Passive Dosing and in Vivo Toxicity Testing.

Identifying key toxicants in sediment is a great challenge, particularly if nontarget toxicants are involved. To identify the contaminants responsible for sediment toxicity to Chironomus dilutus in Guangzhou reach of the Pearl River in South China, passive dosing and in vivo toxicity testing were incorporated into effect-directed analysis (EDA) to account for bioavailability. Fractionation of sediment extracts was performed with gel permeation chromatography and reverse phase liquid chromatography sequentially.

Development of whole-sediment toxicity identification and evaluation (TIE) techniques for two Australian freshwater species: Chironomus tepperi and Austrochiltonia subtenuis.

Most of the public literature and available guidance documents on the conduct of freshwater whole-sediment toxicity identification and evaluations (TIEs) detail the use of test organisms and amending agents that are readily available in North America. These commonly used test organisms and the supported amending agents, however, are not available and largely inappropriate (i.e.

Influence of bioturbation on bioavailability and toxicity of PAHs in sediment from an electronic waste recycling site in South China.

The present study examined the effects of bioturbation by the oligochaete Lumbriculus variegatus on bioavailability and toxicity of sediment-associated polycyclic aromatic hydrocarbons (PAHs) to the oligochaete and the epi-benthic amphipod Hyalella azteca. Various densities of L. variegatus in sediment were used to represent different levels of bioturbation.

Toxicity of sediment-associated unresolved complex mixture and its impact on bioavailability of polycyclic aromatic hydrocarbons.

Unresolved complex mixtures (UCMs) and polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in sediment originating from oil leaks, shipping, and other human activities and thus it is necessary to understand the role of UCM on sediment toxicity and PAH bioaccumulation. In the current study, lethal and sublethal effects of sediment-associated UCM were examined in two benthic invertebrates (Chironomus dilutus and Lumbriculus variegatus) using two spiked sediments. Results showed that UCM alone was toxic to the organisms and its toxicity was species-dependent.

Joint toxicity of a pyrethroid insecticide, cypermethrin, and a heavy metal, lead, to the benthic invertebrate Chironomus dilutus.

Insecticides and heavy metals are frequently detected in the environment, but few studies have assessed the joint toxicity of organic and inorganic contaminants. Joint toxicity of a pyrethroid insecticide, cypermethrin, and a heavy metal, Pb(2+), was evaluated in the present study. An antagonistic toxic response was observed when the benthic invertebrate Chironomus dilutus was simultaneously exposed to the two contaminants in both water and sediment exposures.

Identifying the causes of sediment-associated toxicity in urban waterways of the Pearl River Delta, China.

Twenty-one sediments collected in urban waterways of the Pearl River Delta (PRD) in China were screened for acute toxicity using Chironomus dilutus in addition to being examined for potential contributors of sediment toxicity, including 19 organochlorine, five organophosphate, and nine pyrethroid insecticides, 28 polycyclic aromatic hydrocarbons, 27 polychlorinated biphenyls, 15 polybrominated diphenyl ethers, 12 metals, and ammonia. Fifteen of the 21 sediments exhibited acute toxicity to C. dilutus, with 33% of the samples exhibiting 100% mortality.

Bioavailability of hydrophobic organic contaminants in sediment with different particle-size distributions.

Few studies have been conducted examining the distribution of different-sized particles in sediment and its potential impact on bioavailability of sediment-associated contaminants. In the current study, three sediments composed of different particle sizes, i.e.

Identifying the causes of sediment-associated contamination in the Illinois River (USA) using a whole-sediment toxicity identification evaluation.

Whole-sediment toxicity identification evaluation (TIE) techniques were employed on the Illinois River Complex (IRC), USA to identify the sources of sediment toxicity that may have contributed to the decline in benthic invertebrate populations. The TIE focused on three classes of contaminants: ammonia, metals, and organics. Sediment toxicity was assessed using the amphipod Hyalella azteca, and the focus of the TIE was on assessing spatial and temporal patterns of contamination.

Comparative analysis of whole sediment and porewater toxicity identification evaluation techniques for ammonia and non-polar organic contaminants.

Porewater and whole sediment toxicity identification evaluations (TIEs) were performed on contaminated Illinois River sediment and compared using two standardized toxicity-testing organisms (Ceriodaphnia dubia and Hyalella azteca). Results suggested that the choice of testing matrix (porewater versus whole sediment) significantly influenced characterization of toxicity. The porewater TIE suggested that ammonia was the major source of toxicity, while the whole sediment TIE indicated that non-polar organics, specifically polycyclic aromatic hydrocarbons, were the primary contributor to toxicity, with ammonia being a secondary contributor to toxicity.

The rat parvocellular reticular formation: I. Afferents from the cerebellar nuclei.

The present report elucidates the location of the cells of origin of the cerebellar nuclear-parvocellular reticular projection in the rat. Injection of horseradish peroxidase (HRP) into the parvocellular reticular formation resulted in labeled neurons in the dorsolateral protuberance of the contralateral medial nucleus and bilaterally in the dorsolateral hump region and the large celled subgroup of the lateral nucleus. A small number of labelled cells were found in the middle part of the contralateral medial nucleus.

Immunocytochemical localization of glutamic acid decarboxylase (GAD) and glutamine synthetase (GS) in the area postrema of the cat. Light and electron microscopy.

The present study was designed to investigate the existence of two key enzymes involved in the metabolism of gamma-aminobutyric acid, glutamic acid decarboxylase (GAD) and glutamine synthetase (GS), in the area postrema (AP) of the cat. The results showed that punctuate structures of variable size corresponding to axon terminals, exhibited GAD-immunoreactivity and were distributed in varying densities. The greatest accumulation was present in the caudal and middle segment of the AP and particularly in the area subpostrema, where the aggregation of terminals was extremely dense.

Axoglial contacts in the area postrema of the cat: an ultrastructural study.

Axoglial contacts were observed in an ultrastructural study of the area postrema of the cat. According to the disposition of the electron-dense projections attached to the adjoining membranes these contacts were classified as symmetrical or asymmetrical. The axon profiles contained aggregations of clear vesicles randomly distributed or grouped in cluster adjacent to the electron-dense projections.

Dual efferent projections of the trigeminal principal sensory nucleus to the thalamic ventroposteromedial nucleus in the squirrel monkey.

Anterograde degeneration methods demonstrated two efferent components from the trigeminal principal sensory nucleus (PrV) to the thalamic ventroposteromedial nucleus (VPM) in the squirrel monkey: fibers from the dorsal PrV coursed within the central tegmental tract and terminated in a dorsoventromedial strip of the ipsilateral VPM; fibers from the ventral PrV mainly decussated caudal to the interpeduncular nucleus and terminated in the contralateral VPM exclusive of the sector receiving the dorsal PrV component, contralaterally. Adjacent Nissl sections showed an apparent increase in glial profiles accompanying an intense somal staining among the deafferented neuronal population in the VPM, coextensive with those regions in the VPM exhibiting terminal field degeneration.

Autopsy analysis of the safety, efficacy and cartography of electrical stimulation of the central gray in humans.

Electrical brain stimulation is effective in controlling certain intractable chronic pain syndromes in humans, but the specific target site(s) for stimulation producing a maximal analgesic effect is (are) not well defined. This prospective study correlates the clinical results of chronic stimulation of the periaqueductal gray (PAG) and periventricular gray (PVG) matter in humans with the anatomic site of electrode placement as determined at autopsy, and documents the histologic reactions to electrode implantation and electrical stimulation of the area. Seven patients underwent electrode implantation to control their chronic pain; two had electrodes implanted bilaterally.

Immunocytochemical localization of glial fibrillary acidic protein (GFAP) in the area postrema of the cat. Light and electron microscopic study.

Glial fibrillary acidic protein (GFAP) was demonstrated in the cytoplasm and processes of ependymal cells and astroglial components of the area postrema of the cat. These observations differ from the findings in the ependyma of the ventricular cavities which are consistently negative for the protein. Since some studies have suggested sensory functions of the glial cells in this emetic chemoreceptor trigger zone, a careful consideration of morphological and biochemical attributes of these cells seems appropriate.