Andy M. Booth

Chemical and toxicological characterization of an unresolved complex mixture‐rich biodegraded crude oil

Chemical and toxicological characterization of unresolved complex mixtures in the water-soluble fraction of an artificially weathered Norwegian Sea crude oil was determined by a combination of chemical analysis and toxicity testing in fish in vitro bioassays. The water-soluble fraction of the crude oil was separated into 14 increasingly polar fractions by preparative high-pressure liquid chromatography. The in vitro toxicity (7-ethoxyresorufin O-deethylase activity, estrogenicity, and metabolic inhibition) of these fractions was characterized in a primary culture of liver cells (hepatocytes) from rainbow trout (Oncorhynchus mykiss). The main contributor to toxicity was one of the most polar fractions, accounting gravimetrically for more than 70% of the organic material in the water-soluble fraction and dominated by an unresolved complex mixture. Chemical analysis by gas chromatography-mass spectrometry and comprehensive two-dimensional gas chromatography-time of flight-mass spectrometry identified a large number of cyclic and aromatic sulfoxide compounds and low amounts of benzothiophenes (<0.1% of total mass) in this fraction. Commonly monitored toxic components of crude oil (e.g., naphthalenes, polycyclic aromatic hydrocarbons, and alkylated phenols) eluted in less polar fractions, characterized by somewhat lower toxicity. Normalization of in vitro responses to the mass in each fraction demonstrated a more even distribution of toxicity, indicating that toxicity in the individual fractions was related to the amount of material present. Although polar and nonpolar compounds contribute additively to crude oil toxicity, the water-soluble fraction was dominated by polar compounds because of their high aqueous solubility and the high oil-water loading. Under these conditions, the polar unresolved complex mixture-rich fraction might account for a large portion of crude oil toxicity because of its high abundance in the water-soluble fraction.

Gene Expression of GST and CYP330A1 in Lipid-Rich and Lipid-Poor Female Calanus finmarchicus (Copepoda: Crustacea) Exposed to Dispersed Oil

The copepod Calanus finmarchicus is a marine ecological key species in the Northern Atlantic food web. This species was exposed to an artificially weathered North Sea oil dispersion (oil droplets and water-soluble fractions [WSF]) and a filtered dispersion (containing only WSF) in serial dilution. Female copepods were divided into lipid-rich and lipid-poor for each exposure followed by gene expression analyses of glutathione S-transferase (GST) and cytochrome P-450 330A1 (CYP330A1). Lipid-rich copepods exhibited elevated transcription of GST and reduced transcription of CYP330A1 after exposure to both dispersed oil and WSF. In contrast, lipid-poor copepods exhibited increased transcription of CYP330A1 following exposure to WSF but not the dispersion. Data suggested that small lipid storage promotes increased bioavailability of accumulated oil compounds. Variations in response in CYP330A1 gene expression indicate that oil constituents may exert different modes of toxic action in copepods depending on their reproductive stages. The contribution of oil droplets to the observed effects seemed to be low as GST gene expression was similar after exposure to both dispersed oil and WSF. However, feeding rate in copepods exposed to dispersed oil was reduced, and this may have decreased the uptake of oil constituents via the diet. Although quantitatively higher mortality was observed in copepods exposed to the highest dispersion levels, this may result from smothering of animals by oil droplets. Furthermore, increasing dilution of both the dispersions and the WSF altered their distributions and chemical composition, which may influence the bioavailability of spilled crude oil to pelagic marine organisms.

Emissions from postcombustion CO2 capture plants.

P CO2 capture (PCCC) technology has the potential to contribute significantly to the reduction of anthropogenic CO2 emissions. The application of PCCC technology to reduce CO2 emissions at large point sources, such as fossil fuel-fired power plants is particularly promising. Amine-based scrubbing is the most mature PCCC technology, with 2-aminoethanol (MEA) the most widely utilized solvent. Despite the use of water wash systems to treat effluent, small amounts of the solvent and degradation products are present in amine-based PCCC plant emissions. Recently, concerns have arisen that emissions from PCCC plants could be harmful to human health and the environment. Of particular interest are nitrosamine and nitramine degradation products, many of which are known carcinogens. Degradation products, including nitrosamines and nitramines, will form in PCCC plants from reactions between the amine solvent and NOx species in the flue gas. For primary amine solvents (e.g., MEA), nitrosamines can only be formed indirectly from other degradation products. Solvents with secondary and tertiary amine functionalities (e.g., piperazine and N-methyldiethanolamine) can directly form stable nitrosamines. Nitramines can form directly from primary, secondary, or tertiary amines. However, there is currently limited emission data available for PCCC plants. This problem is compounded by the fact that emission composition and levels will depend significantly on the flue gas being processed, choice of solvent, and plant operation conditions. Emission levels in the range of 2−50 ng/Nm have been reported for both nitrosamines and nitramines at a pilot PCCC plant operating with MEA. These results, together with other reports of nitrosamines detected at pilot PCCC plants and in laboratory experiments, suggest low but quantifiable emissions of nitrosamines and nitramines. In addition to the formation of nitrosamines and nitramines within PCCC plants, it is also possible for these compounds to form through the atmospheric photooxidation of the amine solvent present in the emissions. Steady state conversion rates of amines to nitrosamines and nitramines have been reported for a variety of atmospheric conditions. Steady state nitrosamine yields for N-nitrosodimethylamine (NDMA) were reported to be <0.6% of the amine concentration in a rural scenario and <2.3% in an urban scenario. Similar yields were reported for other nitrosamines and nitramines. The formation of nitrosamines and nitramines can therefore occur both in a PCCC plant and in the atmosphere. Relatively little is known about the potential impacts of PCCC-related emissions on human health and the environment. Compounds emitted from the plant or formed in the atmosphere will disperse and deposit to terrestrial and aquatic environments as either wet or dry aerosols. Preliminary studies have indicated that both nitrosamines and nitramines will partition preferentially to the water phase rather than adsorb to soils and sediments. It seems likely that these compounds will therefore reach an aqueous compartment (e.g., drinking water, groundwater). The biodegradability of nitrosamines and nitramines influences their potential for accumulation in aquatic matrices and ultimately their human and environmental exposure. Initial studies indicate biodegradation of nitrosamines and nitramines is complex, differing significantly between compounds and dependent upon environmental conditions and compound concentration. In general neither nitrosamines nor nitramines seem susceptible to rapid aerobic aqueous biodegradation indicating the possibility of accumulation in these environmental matrices. Owing to their hydrophilic nature, we do not expect nitrosamines and nitramines to bioaccumulate significantly in organisms; however, there seems to be potential for chronic exposure. To determine acceptable PCCC plant emission levels it is important to consider both the environmental fate of the emissions and the acceptable exposure levels. The Norwegian Public Health Institute (NPHI) has proposed acceptable exposure levels of 4 ng/L (drinking water) and 0.3 ng/m (air concentration) based on 10−6 lifetime risk of cancer following exposure to the nitrosamine, NDMA. The NPHI assessment assumes all nitrosamines and nitramines are as carcinogenic as NDMA, which is considered one of the most carcinogenic nitrosamines. The carcinogenicity of nitramines is generally much lower, but insufficient data are available to propose reliable exposure limits. Other existing safety limits for nitrosamines and nitramines following exposure by inhalation, drinking water and to the aquatic environment range from 0.02 ng/m (inhalation; monthly average) to 7 ng/L (drinking water) for nitrosamines, and from 200 ng/L (aquatic

Molecular effects of diethanolamine exposure on Calanus finmarchicus (Crustacea: Copepoda).

Alkanolamines are surface-active chemicals used in a wide range of industrial, agricultural and pharmaceutical applications and products. Of particular interest is the use of alkanolamines such as diethanolamine (DEA) in the removal of CO(2) from natural gas and for CO(2) capture following fossil fuel combustion. Despite this widespread use, relatively little is known about the ecotoxicological impacts of these compounds. In an attempt to assess the potential effects of alkanolamines in the marine environment, a key species in the North Atlantic, the planktonic copepod Calanus finmarchicus, was studied for molecular effects following sublethal exposure to DEA. DEA-induced alterations in transcriptome and metabolome profiling were assessed using a suppression subtractive hybridization (SSH) gene library method and high resolution magic angle spinning nuclear magnetic resonance (HR-MAS NMR), respectively. Effects were observed on transcription of genes reportedly involved in lipid metabolism, antioxidant systems, metal binding, and amino acid and protein catabolism. These effects were accompanied by altered expression of fatty acid derivates, amino acids (threonine, methionine, glutamine, arginine, alanine and leucine) and cholines (choline, phosphocholine and glycerophosphocholine). Together, SSH and HR-MAS NMR offer complementary screening tools for the assessment of molecular responses of C. finmarchicus to DEA and can be used in the study of other chemicals and organisms. Concentration-response and time-response relationships between DEA exposure and single gene transcription were investigated using quantitative PCR. Specific relationships were found between DEA exposure and the transcription of genes involved in protein catabolism (ubiquitin-specific protease-7), metal ion homeostasis (ferritin) and defence against oxidative stress (gamma-glutamylcysteine synthase, glutathione synthase and Cu/Zn-superoxide dismutase). At the lowest alkanolamine concentration used in these experiments, which corresponded to 0.5% of the LC(50) concentration, no transcriptional effects were observed, giving information regarding the lower molecular effect level. Finally, similar transcription patterns were observed for a number of different genes following exposure to DEA, which indicates analogous mechanisms of toxicity and response.

Freshwater dispersion stability of PAA-stabilised cerium oxide nanoparticles and toxicity towards Pseudokirchneriella subcapitata

An aqueous dispersion of poly (acrylic acid)-stabilised cerium oxide (CeO₂) nanoparticles (PAA-CeO₂) was evaluated for its stability in a range of freshwater ecotoxicity media (MHRW, TG 201 and M7), with and without natural organic matter (NOM). In a 15 day dispersion stability study, PAA-CeO₂ did not undergo significant aggregation in any media type. Zeta potential varied between media types and was influenced by PAA-CeO₂ concentration, but remained constant over 15 days. NOM had no influence on PAA-CeO₂ aggregation or zeta potential. The ecotoxicity of the PAA-CeO₂ dispersion was investigated in 72 h algal growth inhibition tests using the freshwater microalgae Pseudokirchneriella subcapitata. PAA-CeO₂ EC₅₀ values for growth inhibition (GI; 0.024 mg/L) were 2-3 orders of magnitude lower than pristine CeO₂ EC₅₀ values reported in the literature. The concentration of dissolved cerium (Ce(3+)/Ce(4+)) in PAA-CeO₂ exposure suspensions was very low, ranging between 0.5 and 5.6 μg/L. Free PAA concentration in the exposure solutions (0.0096-0.0384 mg/L) was significantly lower than the EC10 growth inhibition (47.7 mg/L) value of pure PAA, indicating that free PAA did not contribute to the observed toxicity. Elemental analysis indicated that up to 38% of the total Cerium becomes directly associated with the algal cells during the 72 h exposure. TOF-SIMS analysis of algal cell wall compounds indicated three different modes of action, including a significant oxidative stress response to PAA-CeO₂ exposure. In contrast to pristine CeO₂ nanoparticles, which rapidly aggregate in standard ecotoxicity media, PAA-stabilised CeO₂ nanoparticles remain dispersed and available to water column species. Interaction of PAA with cell wall components, which could be responsible for the observed biomarker alterations, could not be excluded. This study indicates that the increased dispersion stability of PAA-CeO₂ leads to an increase in toxicity compared to pristine non-stabilised forms.

Oil droplet interaction with suspended sediment in the seawater column: Influence of physical parameters and chemical dispersants

The interaction of dispersed oil droplets with large diameter suspended particulate materials (SPM) has been little studied. In the current study, particle size, oil characteristics and chemical dispersant significantly influence the adsorption of oil droplets to SPM in seawater. Sediments with a smaller particulate size (clay) approaching that of the oil droplets (2-20 μm) adsorbed more oil per gram than sediments with large particle size (sand). Heavier, more polar oils with a high asphaltene content adsorbed more efficiently to SPM than lighter, less polar oils. A decrease in the smaller, more water soluble oil components in the sediment adsorbed oil was observed for all oil types. Addition of chemical dispersant decreased the adsorption of oil droplets to suspended carbonate sand in an exponential-like manner. No change in the relative distribution of compounds adsorbed to the sediment was observed, indicating dispersants do not alter the dissolution of compounds from oil droplets.

Carbon Nanotube Properties Influence Adsorption of Phenanthrene and Subsequent Bioavailability and Toxicity to Pseudokirchneriella subcapitata

The bioavailability of organic contaminants adsorbed to carbon nanotubes (CNTs) remains unclear, especially in complex natural freshwaters containing natural organic matter (NOM). Here, we report on the adsorption capacity (Q(0)) of five CNTs exhibiting different physicochemical properties, including a single-walled CNT (SWCNTs), multiwalled CNTs (MWCNT-15 and MWCNT-30), and functionalized MWCNTs (hydroxyl, -OH, and carboxyl, -COOH), for the model polycyclic aromatic hydrocarbon phenanthrene (3.1-800 μg/L). The influence of phenanthrene adsorption by the CNTs on bioavailability and toxicity was investigated using the freshwater algae Pseudokirchneriella subcapitata. CNTs were dispersed in algal growth media containing NOM (DOC, 8.77 mg/L; dispersed concentrations: 0.5, 1.3, 1.3, 3.3, and 6.1 mg/L for SWCNT, MWCNT-15, MWCNT-30, MWCNT-OH, and MWCNT-COOH, respectively). Adsorption isotherms of phenanthrene to the dispersed CNTs were fitted with the Dubinin-Ashtakhov model. Q(0) differed among the CNTs, increasing with increasing surface area and decreasing with surface functionalization. SWCNT and MWCNT-COOH exhibited the highest and lowest log Q(0) (8.891 and 7.636 μg/kg, respectively). The presence of SWCNTs reduced phenanthrene toxicity to algae (EC50; 528.4) compared to phenanthrene-only (EC50; 438.3), and the presence of MWCNTs had no significant effect on phenanthrene toxicity. However, phenanthrene adsorbed to NOM-dispersed CNTs proved to be bioavailable and contribute to exert toxicity to P. subcapitata.

Alkylnaphthalenes: Priority Pollutants or Minor Contributors to the Poor Health of Marine Mussels?

Alkylnaphthalenes (AN) are relatively water-soluble hydrocarbons which, following spillages of crude oils, have been widely reported in contaminated marine organisms such as mussels. In the present report we show, by tandem-gas chromatography-time-of-flight-mass spectrometry (GC × GC-ToF-MS), that the range of AN in contaminated wild mussels from the UK extends beyond the previously GC resolved isomers to those with at least seven substituent carbon atoms. Since surprisingly little information on AN toxicity to such marine organisms has been reported we synthesized two C(8) AN and measured the toxicity of C(2-8) AN to mussels (clearance rate assay). C(2-3) AN were appreciably toxic (concentration for 50% clearance rate inhibition, 48 h IC(50) 1.4-2.6 μmol g(-1) dry weight tissue), but several C(4), (6) and C(8) AN, including branched isomers expected to be resistant to biodegradation and more accumulative, were relatively nontoxic (48 h IC(50) > 10 μmol g(-1)) and longer term exposure (8d) failed to elicit a greater toxic response. The accumulation profiles of AN in laboratory mussels exposed to oil were similar to those of the wild mussels. Moreover, laboratory oil-exposed mussels depurated toxic C(2-3) AN within 5 days in clean water and clearance rates recovered. The latter might imply that, in contrast with branched alkyl benzenes tested previously, AN are of less toxic concern, but such a straightforward conclusion cannot necessarily be drawn; a synthetic branched C(8) AN persisted following depuration and was as toxic to mussels as a C(3) AN (IC(50) 1.3 μmol g(-1)). This indicates that the structures of AN are also important.

Uptake and toxicity of methylmethacrylate‐based nanoplastic particles in aquatic organisms

The uptake and toxicity of 2 poly(methylmethacrylate)-based plastic nanoparticles (PNPs) with different surface chemistries (medium and hydrophobic) were assessed using aquatic organisms selected for their relevance based on the environmental behavior of the PNPs. Pure poly(methylmethacrylate) (medium; PMMA PNPs) and poly(methylmethacrylate-co-stearylmethacrylate) copolymer (hydrophobic; PMMA-PSMA PNPs) of 86 nm to 125 nm were synthesized using a miniemulsion polymerization method. Fluorescent analogs of each PNP were also synthesized using monomer 7-[4-(trifluoromethyl)coumarin]acrylamide and studied. Daphnia magna, Corophium volutator, and Vibrio fischeri were employed in a series of standard acute ecotoxicity tests, being exposed to the PNPs at 3 different environmentally realistic concentrations (0.01 mg/L, 0.1 mg/L, and 1.0 mg/L) and a high concentration 500 mg/L to 1000 mg/L. In addition, sublethal effects of PNPs in C. volutator were determined using a sediment reburial test, and the uptake and depuration of fluorescent PNPs was studied in D. magna. The PNPs and fluorescent PNPs did not exhibit any observable toxicity at concentrations up to 500 mg/L to 1000 mg/L in any of the tests except for PMMA-PSMA PNPs and fluorescent PNPs following 48-h exposure to D. magna (median lethal concentration values of 879 mg/L and 887 mg/L, respectively). No significant differences were observed between labeled and nonlabeled PNPs, indicating the suitability of using fluorescent labeling. Significant uptake and rapid excretion of the fluorescent PNPs was observed in D. magna. Environ Toxicol Chem 2016;35:1641-1649.

Biokinetics of nanomaterials: The role of biopersistence

Nanotechnology risk management strategies and environmental regulations continue to rely on hazard and exposure assessment protocols developed for bulk materials, including larger size particles, while commercial application of nanomaterials (NMs) increases. In order to support and corroborate risk assessment of NMs for workers, consumers, and the environment it is crucial to establish the impact of biopersistence of NMs at realistic doses. In the future, such data will allow a more refined future categorization of NMs. Despite many experiments on NM characterization and numerous in vitro and in vivo studies, several questions remain unanswered including the influence of biopersistence on the toxicity of NMs. It is unclear which criteria to apply to characterize a NM as biopersistent. Detection and quantification of NMs, especially determination of their state, i.e., dissolution, aggregation, and agglomeration within biological matrices and other environments are still challenging tasks; moreover mechanisms of nanoparticle (NP) translocation and persistence remain critical gaps. This review summarizes the current understanding of NM biokinetics focusing on determinants of biopersistence. Thorough particle characterization in different exposure scenarios and biological matrices requires use of suitable analytical methods and is a prerequisite to understand biopersistence and for the development of appropriate dosimetry. Analytical tools that potentially can facilitate elucidation of key NM characteristics, such as ion beam microscopy (IBM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS), are discussed in relation to their potential to advance the understanding of biopersistent NM kinetics. We conclude that a major requirement for future nanosafety research is the development and application of analytical tools to characterize NPs in different exposure scenarios and biological matrices.