Promotive Effects of Chloride and Sulfate on the Near-Complete Destruction of Perfluorocarboxylates (PFCAs) in Brine via Hydrogen-tuned 185-nm UV Photolysis: Mechanisms and Kinetics.

Hydrogen-tuned 185 nm vacuum ultraviolet (VUV/H2) photolysis is an emerging technology to destroy per- and polyfluoroalkyl substance (PFAS) in brine. This study discovered the promotive effects of two major brine anions, i.e., chloride and sulfate in VUV/H2 photolysis on the hydrated electron (eaq-) generation and perfluorocarboxylates (PFCAs) destruction and established a kinetics model to elucidate the promotive effects on the steady-state concentration of eaq- ([eaq-]ss). Results showed that VUV/H2 achieved near-complete defluorination of perfluorooctanoic acid (PFOA) in the presence of up to 1000 mM chloride or sulfate at pH 12. The defluorination rate constant (kdeF) of PFOA peaked with a chloride concentration at 100 mM and with a sulfate concentration at 500 mM. The promotive effects of chloride and sulfate were attributed to an enhanced generation of eaq- via their direct VUV photolysis and conversion of additionally generated hydroxyl radical to eaq- by H2, which was supported by a linear correlation between the predicted [eaq-]ss and experimentally observed kdeF. The kdeF value increased from pH 9 to 12, which was attributed to the speciation of the H·/eaq- pair. Furthermore, the VUV system achieved >95% defluorination and ≥99% parent compound degradation of a concentrated PFCAs mixture in a synthetic brine, without generating any toxic perchlorate or chlorate.

Methylation and Demethylation of Emerging Contaminants in Plants.

Many contaminants of emerging concern (CECs) have reactive functional groups and may readily undergo biotransformations, such as methylation and demethylation. These transformations have been reported to occur during human metabolism and wastewater treatment, leading to the propagation of CECs. When treated wastewater and biosolids are used in agriculture, CECs and their transformation products (TPs) are introduced into soil-plant systems. However, little is known about whether transformation cycles, such as methylation and demethylation, take place in higher plants and hence affect the fate of CECs in terrestrial ecosystems. In this study, we explored the interconversion between four common CECs (acetaminophen, diazepam, methylparaben, and naproxen) and their methylated or demethylated TPs in Arabidopsis thaliana cells and whole wheat seedlings. The methylation-demethylation cycle occurred in both plant models with demethylation generally taking place at a greater degree than methylation. The transformation rate of demethylation or methylation was dependent on the bond strength of R-CH3, with demethylation of methylparaben or methylation of acetaminophen being more pronounced. Although not explored in this study, these interconversions may exert influences on the behavior and biological activity of CECs, particularly in terrestrial ecosystems. The study findings demonstrated the prevalence of transformation cycles between CECs and their methylated or demethylated TPs in higher plants, contributing to a more complete understanding of risks of CECs in the human-wastewater-soil-plant continuum.

Limited Effectiveness of Carbonaceous Sorbents in Sequestering Aged Organic Contaminants in Sediments.

Carbonaceous materials are often proposed for use in restoring soils or sediments contaminated with hydrophobic organic contaminants (HOCs). However, the contamination of most sites is a result of historical events, where HOCs have resided in the solid compartment for many years or decades. The prolonged contact time, or aging, leads to reduced contaminant availability and likely diminished effectiveness of using sorbents. In this study, three different carbonaceous sorbents, i.e., biochars, powdered activated carbon, and granular activated carbon, were amended to a Superfund site marine sediment contaminated with DDT residues from decades ago. The amended sediments were incubated in seawater for up to 1 year, and the freely dissolved concentration (Cfree) and the biota-sediment accumulation factors (BSAFs) for a native polychaete (Neanthes arenaceodentata) were measured. Even though the bulk sediment concentrations were very high (6.4-154.9 µg/g OC), both Cfree and BSAFs were very small, ranging from nd to 1.34 ng/L and from nd to 0.024, respectively. The addition of carbonaceous sorbents, even at 2% (w/w), did not consistently lead to reduced DDT bioaccumulation. The limited effectiveness of carbonaceous sorbents was attributed to the low DDT availability due to prolonged aging, highlighting the need for considering contaminant aging when using sorbents for remediation.

Methylation and Demethylation of Emerging Contaminants Changed Bioaccumulation and Acute Toxicity in Daphnia magna.

Contaminants of emerging concern (CECs) in the environment undergo various transformations, leading to the formation of transformation products (TPs) with a modified ecological risk potential. Although the environmental significance of TPs is increasingly recognized, there has been relatively little research to understand the influences of such transformations on subsequent ecotoxicological safety. In this study, we used four pairs of CECs and their methylated or demethylated derivatives as examples to characterize changes in bioaccumulation and acute toxicity in Daphnia magna, as a result of methylation or demethylation. The experimental results were further compared to quantitative structure-activity relationship (QSAR) predictions. The methylated counterpart in each pair generally showed greater acute toxicity in D. magna, which was attributed to their increased hydrophobicity. For example, the LC50 values of methylparaben (34.4 ± 4.3 mg L-1) and its demethylated product (225.6 ± 17.3 mg L-1) differed about eightfold in D. magna. The methylated derivative generally exhibited greater bioaccumulation than the demethylated counterpart. For instance, the bioaccumulation of methylated acetaminophen was about 33-fold greater than that of acetaminophen. In silico predictions via QSARs aligned well with the experimental results and suggested an increased persistence of the methylated forms. The study findings underline the consequences of simple changes in chemical structures induced by transformations such as methylation and demethylation and highlight the need to consider TPs to achieve a more holistic understanding of the environmental fate and risks of CECs.

The Use of Non-targeted Lipidomics and Histopathology to Characterize the Neurotoxicity of Bifenthrin to Juvenile Rainbow Trout (Oncorhynchus mykiss).

Due to the detection frequencies and measured concentrations in surface water, the type I pyrethroid insecticide, bifenthrin, has been of particular concern within the Sacramento-San Joaquin Delta in California. Concentrations have been detected above levels previously reported to impair neuroendocrine function and induce neurotoxicity to several species of salmonids. Metabolomic and transcriptomic studies indicated impairment of cellular signaling within the brain of exposed animals and potential alteration of lipid metabolism. To better understand the potential impacts of bifenthrin on brain lipids, juvenile rainbow trout (Oncorhynchus mykiss) were exposed to mean bifenthrin concentrations of 28 or 48 ng/L for 14 days, and non-targeted lipidomic profiling in the brain was conducted. Brain tissue sections were also assessed for histopathological insult following bifenthrin treatment. Bifenthrin-exposed trout had a concentration-dependent decrease in the relative abundance of triglycerides (TGs) with levels of phosphatidylcholines (PCs) and phosphatidylethanolamines (PEs) significantly altered following 48 ng/L bifenthrin exposure. An increased incidence of histopathological lesions, such as focal hemorrhages and congestion of blood vessels, was noted in the brains of bifenthrin-treated animals, suggesting an association between altered lipid metabolism and neuronal cell structure and integrity.

Conjugation of Di-n-butyl Phthalate Metabolites in Arabidopsis thaliana and Potential Deconjugation in Human Microsomes.

Plasticizers, due to the widespread use of plastics, occur ubiquitously in the environment. The reuse of waste resources (e.g., treated wastewater, biosolids, animal waste) and other practices (e.g., plastic mulching) introduce phthalates into agroecosystems. As a detoxification mechanism, plants are known to convert phthalates to polar monophthalates after uptake, which are followed by further transformations, including conjugation with endogenous biomolecules. The objective of this study was 2-fold: to obtain a complete metabolic picture of the widely used di-n-butyl phthalate (DnBP) by using a suite of complementary techniques, including stable isotope labeling, 14C tracing, and high-resolution mass spectrometry, and to determine if conjugates are deconjugated in human microsomes to release bioactive metabolites. In Arabidopsis thaliana cells, the primary initial metabolite of DnBP was mono-n-butyl phthalate (MnBP), and MnBP was rapidly metabolized via hydroxylation, carboxylation, glycosylation, and malonylation to seven transformation products. One of the conjugates, MnBP-acyl-ß-d-glucoside (MnBP-Glu), was incubated in human liver (HLM) and intestinal (HIM) microsomes and was found to undergo rapid transformations. Approximately 15% and 10% of MnBP-Glu were deconjugated to the free form MnBP in HIM and HLM, respectively. These findings highlight that phthalates, as diesters, are susceptible to hydrolysis to form monoesters that can be readily conjugated via a phase II metabolism in plants. Conjugates may be deconjugated to release bioactive compounds after human ingestion. Therefore, an accurate assessment of the dietary exposure of phthalates and other contaminants must consider plant metabolites, especially including conjugates, to better predict their potential environmental and human health risks.

Stage Dependent Enantioselective Metabolism of Bifenthrin in Embryos of Zebrafish (Danio rerio) and Japanese Medaka (Oryzias latipes).

Bifenthrin (BF) is a widely used pyrethroid that has been frequently detected in surface waters. Previous studies indicated that BF had antiestrogenic activity in zebrafish embryos but estrogenic activity in posthatch fish. To determine whether age-related differences in metabolism contribute to the endocrine effects in developing fish, embryos from zebrafish and Japanese medaka were exposed to BF before and after liver development. Since the commercial mixture of BF is an isomer-enriched product containing two enantiomers (1R-cis-BF and 1S-cis-BF), enantioselective metabolism was also evaluated. The estrogenic metabolite, 4-hydroxybifenthrin (4-OH-BF) was identified in zebrafish embryos, and formation was higher in animals after liver development (>48 hpf). Treatments with ß-glucuronidase indicated that 4-OH-BF underwent conjugation in embryos. Formation was reduced by cotreatment of the cytochrome P450 (CYP450) inhibitor, ketoconazole. Formation of 4-OH-BF was greater when treated with 1R-cis-BF compared to the S-enantiomer. However, metabolites were not observed in medaka embryos. These data indicate enantioselective oxidation of BF to an estrogenic metabolite occurs in zebrafish embryos and, since it is increased after liver development, may partially explain estrogenic activity observed in older animals. The lack of activity in medaka suggests species-specific effects with BF metabolism and may influence risk assessment strategies in wildlife.

Accumulation of HOCs via Precontaminated Microplastics by Earthworm Eisenia fetida in Soil.

Soil is a primary sink for plastics, but the influence of microplastics as carriers on terrestrial cycling of persistent contaminants is poorly understood as compared to aquatic systems. Studies to date have disregarded the potential fact that microplastics are generally contaminated before their entry into soil. In this study, earthworm Eisenia fetida was incubated for 28 d in a soil amended with five common types of microplastics precontaminated with polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) to elucidate contaminant transfer. Accumulation of HOCs in E. fetida varied greatly among different plastic types and HOCs. The freely dissolved concentration (Cfree) of HOCs showed that desorption of HOCs from microplastics into soil was closely related to plastic types and HOC hydrophobicity and was much slower for polystyrene or polypropylene than polyethylene. Biodynamic model analysis suggested that ingestion of microplastics could act as a significant pathway for some microplastics, likely due to HOCs on the plastics being in an "over-equilibrium" state. This was in contrast with mixing clean microplastics into HOC-contaminated soil, where the microplastics decreased bioaccumulation. Therefore, whether microplastics serve as facilitators or inhibitors of HOC bioaccumulation depends on the fugacity gradient of HOCs between microplastics and soil, which highlights the importance of considering the sequence of contamination between the plastics and soil. These findings also question the validity of short-term experiments because of the generally very slow partition kinetics of HOCs on plastics.

Cation-π Interactions with Coexisting Heavy Metals Enhanced the Uptake and Accumulation of Polycyclic Aromatic Hydrocarbons in Spinach.

Few studies have considered the effect of co-occurring heavy metals on plant accumulation of hydrophobic organic compounds (HOCs), and less is known about the role of intermolecular interactions. This study investigated the molecular mechanisms of Cu/Zn effects on hydroponic uptake of four deuterated polycyclic aromatic hydrocarbons (PAHs-d10) by spinach (Spinacia oleracea L.). Both solubility enhancement experiment and quantum mechanical calculations demonstrated the existence of [PAH-Cu(H2O)0-4]2+ and [2·PAH-Cu(H2O)0-2]2+ via cation-π interactions when Cu2+ concentration was ≤100 µmol/L. Notably, PAH-d10 concentrations in both roots and shoots increased significantly with Cu2+ concentration. This was because the formation of phytoavailable PAH-Cu2+ complexes decreased PAH-d10 hydrophobicity and consequently decreased their sorption onto dissolved organic carbon (DOC, i.e., root exudates), thereby increasing phytoavailable concentrations and uptake of PAHs-d10. X-ray absorption near-edge structure analysis showed that PAH-Cu2+ complexes could enter defective spinach roots via apoplastic pathway. However, Zn2+ and PAHs-d10 cannot form the cation-π interactions because of the high desolvation penalty of Zn2+. Actually, Zn2+ decreased the spinach uptake of PAHs-d10 due to the increase of DOC induced by Zn. This work provides molecular insights into how metals could selectively affect the plant uptake of HOCs and highlights the importance of considering the HOC phytoavailability with coexisting metals.

Metabolomic Profiles in the Brains of Juvenile Steelhead (Oncorhynchus mykiss) Following Bifenthrin Treatment.

The pyrethroid insecticide, bifenthrin, is frequently measured at concentrations exceeding those that induce acute and chronic toxicity to several invertebrate and fish species residing in the Sacramento-San Joaquin Delta of California. Since the brain is considered to be a significant target for bifenthrin toxicity, juvenile steelhead trout (Oncorhynchus mykiss) were treated with concentrations of bifenthrin found prior to (60 ng/L) and following (120 ng/L) major stormwater runoff events with nontargeted metabolomics used to target transcriptomic alterations in steelhead brains following exposure. Predicted responses were involved in cellular apoptosis and necrosis in steelhead treated with 60 ng/L bifenthrin using the software Ingenuity Pathway Analysis. These responses were predominately driven by decreased levels of acetyl-l-carnitine (ALC), docosahexaenoic acid (DHA), and adenine. Steelhead treated with 120 ng/L bifenthrin had reductions of lysophosphatidylcholines (LPC), lysophosphatidylethanolamines (LPE), and increased levels of betaine, which were predicted to induce an inflammatory response. Several genes predicted to be involved in apoptotic (caspase3 and nrf2) and inflammatory (miox) pathways had altered expression following exposure to bifenthrin. There was a significantly increased expression of caspase3 and miox in fish treated with 120 ng/L bifenthrin with a significant reduction of nrf2 in fish treated with 60 ng/L bifenthrin. These data indicate that bifenthrin may have multiple targets within the brain that affect general neuron viability, function, and signaling potentially through alterations in signaling fatty acids.

Contaminants of emerging concern affect Trichoplusia ni growth and development on artificial diets and a key host plant.

Many countries are utilizing reclaimed wastewater for agriculture because drought, rising temperatures, and expanding human populations are increasing water demands. Unfortunately, wastewater often contains biologically active, pseudopersistent pharmaceuticals, even after treatment. Runoff from farms and output from wastewater treatment plants also contribute high concentrations of pharmaceuticals to the environment. This study assessed the effects of common pharmaceuticals on an agricultural pest, Trichoplusia ni (Lepidoptera: Noctuidae). Larvae were reared on artificial diets spiked with contaminants of emerging concern (CECs) at environmentally relevant concentrations. Trichoplusia ni showed increased developmental time and mortality when reared on artificial diets containing antibiotics, hormones, or a mixture of contaminants. Mortality was also increased when T. ni were reared on tomatoes grown hydroponically with the same concentrations of antibiotics. The antibiotic-treated plants translocated ciprofloxacin through their tissues to roots, shoots, and leaves. Microbial communities of T. ni changed substantially between developmental stages and when exposed to CECs in their diets. Our results suggest that use of reclaimed wastewater for irrigation of crops can affect the developmental biology and microbial communities of an insect of agricultural importance.

A Novel Water-Swelling Sampling Probe for in Vivo Detection of Neonicotinoids in Plants.

Ecotoxicological risks of neonicotinoid insecticides are raising significant concerns, including their potential role in bee population declines. Neonicotinoids are water-soluble, systemic insecticides, and exposure of nontarget organisms such as pollinators occurs mainly through residues in nectar and pollens of flowering plants. To better elucidate the underlying mechanisms for such nontarget exposure, it is highly valuable to develop analytical capabilities for in vivo monitoring of neonicotinoids in live plants. In this study, we developed a novel biomimetic water-swelling solid-phase microextraction (SPME) probe, with limits of detection for neonicotinoids as low as 0.03 ng mL-1, and applied it for in vivo detection of seven neonicotinoids in plant sap. The preparation of this fiber was simple and free of stringent or complex physical-chemical reactions. Equilibrium in neonicotinoid accumulation on the fiber was reached in <10 min, allowing for near instantaneous sampling. The water-swelling fiber displayed much greater sampling capacity than the commercially available polydimethylsiloxane and polyacrylate fibers, good reproducibility (RSD of inter- and intrafiber <8.9% and 7.8%, respectively), and antibiofouling property (no loss in performance after 20 use cycles). After treating lettuce (Lactuca sativa L.) by foliar spray and soybean (Glycine max M.) by seed soaking, the in vivo assays provided a wealth of information, including changes in levels and distribution of neonicotinoids over time in the same plants. Kinetics and distribution patterns suggested that after treatment at the same level, neonicotinoids differed significantly in their levels in the sap. The in vivo sampling and monitoring of neonicotinoids in live plants may provide unique and much needed information in achieving breakthrough understanding of the connection between neonicotinoid use and pollinator exposure.

Occurrence and Probable Sources of Urban-Use Insecticides in Marine Sediments off the Coast of Los Angeles.

Insecticides such as pyrethroids and fipronil are used in large amounts in both agricultural and urban settings and have the potential to elicit toxicity to nontarget aquatic organisms. In California, like in many other regions of the world, urban centers are located along the coast, and it is documented that urban-use insecticides enter the marine environment, where little is known about their occurrence and consequences. In this study, we measured the spatial distribution of pyrethroids and fipronil (and its metabolites) on the Palos Verdes Shelf off the coast of Los Angeles. Total pyrethroid levels ranged from nd to 170 µg/kg (dry weight), and fipronil sulfide levels ranged from 1.8 to 5.6 µg/kg. Two pyrethroids were traced to wastewater effluent discharge, while two others and fipronil sulfide were traced to to surface runoff. Toxicity units (TUs) were estimated for benthic invertebrates, which ranged from no toxicity (nt) to 146 for total pyrethroids, and 0.09 to 1.6 and 4.2 to 75 for fipronil sulfide, depending on the indicator species. Therefore, near-shore deposition of urban-use insecticides due to wastewater discharge and surface runoff poses a significant risk to marine benthic invertebrates and highlights the importance of monitoring near-shore ocean environments and developing mitigation strategies to reduce seaward movement.

Pharmaceutical and Personal Care Products: From Wastewater Treatment into Agro-Food Systems.

Irrigation with treated wastewater (TWW) and application of biosolids introduce numerous pharmaceutical and personal care products (PPCPs) into agro-food systems. While the use of TWW and biosolids has many societal benefits, introduction of PPCPs in production agriculture poses potential food safety and human health risks. A comprehensive risk assessment and management scheme of PPCPs in agro-food systems is limited by multiple factors, not least the sheer number of investigated compounds and their diverse structures. Here we follow the fate of PPCPs in the water-soil-produce continuum by considering processes and variables that influence PPCP transfer and accumulation. By analyzing the steps in the soil-plant-human diet nexus, we propose a tiered framework as a path forward to prioritize PPCPs that could have a high potential for plant accumulation and thus pose greatest risk. This article examines research progress to date and current research challenges, highlighting the potential value of leveraging existing knowledge from decades of research on other chemicals such as pesticides. A process-driven scheme is outlined to derive a short list that may be used to refocus our future research efforts on PPCPs and other analogous emerging contaminants in agro-food systems.

Inference of Organophosphate Ester Emission History from Marine Sediment Cores Impacted by Wastewater Effluents.

Organophosphate esters (OPEs) have been in use as flame retardants for many decades, with their actual usage varying over time. Knowledge of the emission history of OPEs is valuable for improving our prediction of their environmental loadings and associated risks. In this study, concentrations and compositions of 10 OPEs were measured in three dated sediment cores from the Palos Verdes Shelf (PVS) off the coast of Los Angeles, which has been impacted by wastewater treatment plant (WWTP) effluents for over a century. The total OPE concentrations varied from 0.68 to 1064 ng/g along the sediment profile, with two apparent peaks. The first peak occurred in the 1970s, coinciding with peak emissions from WWTPs. The second peak appeared in the 2000s and was possibly attributed to increased consumption of OPEs as replacement flame retardants. Since downward movement of OPEs in the PVS sediment bed was retarded by their slow desorption, the reconstructed history likely provided an accurate picture of OPE emissions in Southern California and North America. These findings suggest that the near-shore marine sediments affected by WWTP effluents could serve as an environmental proxy documenting history in OPE use and emissions.

A Novel Active Sampler Coupling Osmotic Pump and Solid Phase Extraction for in Situ Sampling of Organic Pollutants in Surface Water.

Active samplers for ambient monitoring of trace contaminants in surface water are highly desirable, but their use is often constrained by power supply. Here, we proposed a novel solution by coupling an improved osmotic pump (OP) with a solid-phase extraction (SPE) cartridge to construct a power-free active sampler for organic contaminants. The OP simply consisted of two cylindrical chambers separated by a reverse osmosis membrane. We, for the first time, added ion-exchange resins into the OP inlet chamber and successfully constructed OPs with a smooth and constant flow. In the OP-SPE sampler, water was continuously drawn through the SPE cartridge at a constant flow, and time-weighted average concentration over the sampling course may be easily calculated from the amount of target analytes retained on the SPE cartridge and water collected in the sampler. The OP-SPE samplers were deployed in a river to detect herbicides, and the measured concentrations were largely in agreement with the average of 11 daily spot samples. Given that a wide range of SPE cartridges are available for different classes of organic contaminants, this approach is versatile and may find widespread applications for in situ sampling of surface water under different conditions, including poorly accessible locations.

Effects of bifenthrin on sex differentiation in Japanese Medaka (Oryzias latipes).

Bifenthrin (BF) is a pyrethroid insecticide used in urban and agricultural applications. Previous studies in early life stages of fish have indicated anti-estrogenic activity; however, estrogenic activity has been observed in adults. To test the hypothesis that BF impairs sex differentiation, larval Japanese Medaka were exposed to BF during a critical developmental window for phenotypic sexual differentiation. Fish were exposed to environmentally relevant concentrations of BF (0.15 µg/L and 1.5 µg/L), a single concentration (0.3 mg/L) of an estrogen receptor (ER) antagonist (ICI 182,780), and an ER agonist (0.2 ug/L) (17ß-estradiol). Fish were exposed at 8 days post hatch (dph) larvae for 30 days. Phenotypic sex, secondary sexual characteristics (SSC) and genotypic sex were investigated at sexual maturity (8 weeks). A trend towards masculinization (p = 0.06) based on the presence of papillary processes in anal fin rays of Japanese Medaka was observed in fish exposed to the lowest concentration of BF. However, genotypic gender ratios were not altered. These results show sex differentiation was not significantly altered by larval exposure to BF in Japanese medaka.

Stable Isotope Labeling-Assisted Metabolite Probing for Emerging Contaminants in Plants.

Biotransformation is a notable modulator of the fate, bioaccumulation, and toxicity of contaminants in the environment. However, it is often formidable to identify unknown biotransformation products in the absence of reference standards, and this analytical challenge is particularly true for contaminants of emerging concern (CECs) that are mostly polar molecules without characteristic structures (e.g., Cl and Br) and in complex matrices such as plants. In this study, using the fibrate drug gemfibrozil as a model CEC and Arabidopsis thaliana as a model plant, we developed and demonstrated a novel analytical framework coupling deuterium stable isotope labeling with high-resolution mass spectrometry (SILAMS) in identifying plant biotransformation products. When exposed in A. thaliana cells, gemfibrozil was quickly taken up into the cells and extensively metabolized. The use of nonlabeled and deuterated gemfibrozil at a 3:1 ratio created unique diagnostic patterns in mass spectra, enabling the identification of 11 novel phase II amino acid/peptide conjugates. Similarity in mass fragmentation patterns and chromatographic behaviors was then employed to establish the probable structures. Two major metabolites were further confirmed as glutamate and glutamine conjugates using authentic standards. Most of the identified conjugates were also detected in the whole A. thaliana plant. Therefore, SILAMS offers unique advantages by excluding false matrix positives and helping discern unknown metabolites, including polar conjugates with endogenous biomolecules, with a high degree of confidence. This novel framework may be readily applied to other CECs for high-throughput metabolite screening in plants to improve our understanding of their food safety and human health risks and potential deleterious effects on other species living on plants.

Role of fluoranthene and pyrene associated with suspended particles in their bioaccumulation by zebrafish (Danio rerio).

Hydrophobic organic compounds (HOCs) tend to be associated with suspended particles in surface aquatic systems, however, the bioavailability of HOCs on suspended particles to fish is not well understood. In this study, a passive dosing device was used to control the freely dissolved concentrations (Cfree) of polycyclic aromatic hydrocarbons (PAHs) including fluoranthene and pyrene, and the influence of particle-associated PAHs on their bioaccumulation by zebrafish was investigated. The results showed that, when the Cfree of PAHs were kept constant, the presence of suspended particles did not significantly affect the steady state of PAH bioaccumulation in zebrafish tissues excluding head and digestive tracts, suggesting that the bioaccumulation steady state was controlled by the freely dissolved concentrations of PAHs. However, suspended particles promoted the uptake and elimination rate constants of PAHs in zebrafish body excluding head and digestive tracts. The uptake rate constants with 0.5 g/L suspended particles were approximately twice of those without suspended particles, and the body burden in zebrafish increased by 16.4% - 109.3% for pyrene and 21.8% - 490.4% for fluoranthene during the first 8-d exposure. This was due to the reasons that suspended particles could be ingested, and part of PAHs associated with them could be desorbed in digestive tract and absorbed by the zebfrafish, leading to the enhancement of uptake rates of PAHs in zebfrafish. The findings obtained from this study indicate that PAHs on suspended particles are partly bioavailable to zebrafish and particle ingestion is an important route in PAH bioaccumulation. Therefore, it is important to consider the bioavailability of HOCs on suspended particles to improve ecological risk assessment.

Effects of contaminants of emerging concern on Myzus persicae (Sulzer, Hemiptera: Aphididae) biology and on their host plant, Capsicum annuum.

Many countries are utilizing reclaimed wastewater for agriculture as water demands due to drought, rising temperatures, and expanding human populations. Unfortunately, wastewater often contains biologically active, pseudopersistant pharmaceuticals, even after treatment. Runoff from agriculture and effluent from wastewater treatment plants also contribute high concentrations of pharmaceuticals to the environment. This study assessed the effects of common pharmaceuticals on an agricultural pest, the aphid Myzus persicae (Sulzer, Hemiptera: Aphididae). Second instar nymphs were transferred to bell peppers (Capsicum annuum) that were grown hydroponically. Treatment plants were spiked with contaminants of emerging concern (CECs) at environmentally relevant concentrations found in reclaimed wastewater. M. persicae displayed no differences in population growth or microbial community differences due to chemical treatments. Plants, however, displayed significant growth reduction in antibiotic and mixture treatments, specifically in wet root masses. Antibiotic treatment masses were significantly reduced in the total and root wet masses. Mixture treatments displayed an overall reduction in plant root wet mass. Our results suggest that the use of reclaimed wastewater for crop irrigation would not affect aphid populations, but could hinder or delay crop production.