Identification and characterization of a small-molecule metallophore involved in lanthanide metabolism.

Many bacteria secrete metallophores, low-molecular-weight organic compounds that bind ions with high selectivity and affinity, in order to access essential metals from the environment. Previous work has elucidated the structures and biosynthetic machinery of metallophores specific for iron, zinc, nickel, molybdenum, and copper. No physiologically relevant lanthanide-binding metallophore has been discovered despite the knowledge that lanthanide metals (Ln) have been revealed to be essential cofactors for certain alcohol dehydrogenases across a diverse range of phyla. Here, we report the biosynthetic machinery, the structure, and the physiological relevance of a lanthanophore, methylolanthanin. The structure of methylolanthanin exhibits a unique 4-hydroxybenzoate moiety which has not previously been described in other metallophores. We find that production of methylolanthanin is required for normal levels of Ln accumulation in the methylotrophic bacterium Methylobacterium extorquens AM1, while overexpression of the molecule greatly increases bioaccumulation and adsorption. Our results provide a clearer understanding of how Ln-utilizing bacteria sense, scavenge, and store Ln; essential processes in the environment where Ln are poorly bioavailable. More broadly, the identification of this lanthanophore opens doors for study of how biosynthetic gene clusters are repurposed for additional functions and the complex relationship between metal homeostasis and fitness.

Metallomic mapping of gut and brain in heavy metal exposed earthworms: A novel paradigm in ecotoxicology.

This study explored the uptake of lead in the epigeic earthworm Dendrobaena veneta exposed to 0, 1000, and 2500 µg Pb/g soil. The soil metal content was extracted using strong acid digestion and water leaching, and analysed by means of Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to estimate absolute and bioavailable concentrations of metals in the soil. The guts and heads of lead-exposed earthworms were processed into formalin-fixed and paraffin embedded sections for high-resolution multi-element metallomic imaging via Laser Ablation ICP-MS (LA-ICP-MS). Metallomic maps of phosphorus, zinc, and lead were produced at 15-µm resolution in the head and gut of D. veneta. Additional 4-µm resolution metallomic maps of the earthworm brains were taken, revealing the detailed localisation of metals in the brain. The Pb bioaccumulated in the chloragogenous tissues of the earthworm in a dose-dependent manner, making it possible to track the extent of soil contamination. The bioaccumulation of P and Zn in earthworm tissues was independent of Pb exposure concentration. This approach demonstrates the utility of LA-ICP-MS as a powerful approach for ecotoxicology and environmental risk assessments.

Initiation of metformin in early pregnancy results in fetal bioaccumulation, growth restriction, and renal dysmorphology in a primate model.

BACKGROUND: In recent years, pragmatic metformin use in pregnancy has stretched to include prediabetes mellitus, type 2 diabetes mellitus, gestational diabetes mellitus, and (most recently) preeclampsia. However, with its expanded use, concerns of unintended harm have been raised. OBJECTIVE: This study developed an experimental primate model and applied ultrahigh performance liquid chromatography coupled to triple-quadrupole mass spectrometry for direct quantitation of maternal and fetal tissue metformin levels with detailed fetal biometry and histopathology. STUDY DESIGN: Within 30 days of confirmed conception (defined as early pregnancy), 13 time-bred (timed-mated breeding) Rhesus dams with pregnancies designated for fetal necropsy were initiated on twice-daily human dose-equivalent 10 mg/kg metformin or vehicle control. Pregnant dams were maintained as pairs and fed either a control chow or 36% fat Western-style diet. Metformin or placebo vehicle control was delivered in various treats while the animals were separated via a slide. A cesarean delivery was performed at gestational day 145, and amniotic fluid and blood were collected, and the fetus and placenta were delivered. The fetus was immediately necropsied by trained primate center personnel. All fetal organs were dissected, measured, sectioned, and processed per clinical standards. Fluid and tissue metformin levels were assayed using validated ultrahigh performance liquid chromatography coupled to triple-quadrupole mass spectrometry in selected reaction monitoring against standard curves. RESULTS: Among 13 pregnancies at gestational day 145 with fetal necropsy, 1 dam and its fetal tissues had detectable metformin levels despite being allocated to the vehicle control group (>1 µmol metformin/kg maternal weight or fetal or placental tissue), whereas a second fetus allocated to the vehicle control group had severe fetal growth restriction (birthweight of 248.32 g [<1%]) and was suspected of having a fetal congenital condition. After excluding these 2 fetal pregnancies from further analyses, 11 fetuses from dams initiated on either vehicle control (n=4: 3 female and 1 male fetuses) or 10 mg/kg metformin (n=7: 5 female and 2 male fetuses) were available for analyses. Among dams initiated on metformin at gestational day 30 (regardless of maternal diet), significant bioaccumulation within the fetal kidney (0.78-6.06 µmol/kg; mean of 2.48 µmol/kg), liver (0.16-0.73 µmol/kg; mean of 0.38 µmol/kg), fetal gut (0.28-1.22 µmol/kg; mean of 0.70 µmol/kg), amniotic fluid (0.43-3.33 µmol/L; mean of 1.88 µmol/L), placenta (0.16-1.00 µmol/kg; mean of 0.50 µmol/kg), fetal serum (0.00-0.66 µmol/L; mean of 0.23 µmol/L), and fetal urine (4.10-174.10 µmol/L; mean of 38.5 µmol/L) was observed, with fetal levels near biomolar equivalent to maternal levels (maternal serum: 0.18-0.86 µmol/L [mean of 0.46 µmol/L]; maternal urine: 42.60-254.00 µmol/L [mean of 149.30 µmol/L]). Western-style diet feeding neither accelerated nor reduced metformin bioaccumulations in maternal or fetal serum, urine, amniotic fluid, placenta, or fetal tissues. In these 11 animals, fetal bioaccumulation of metformin was associated with less fetal skeletal muscle (57% lower cross-sectional area of gastrocnemius) and decreased liver, heart, and retroperitoneal fat masses (P<.05), collectively driving lower delivery weight (P<.0001) without changing the crown-rump length. Sagittal sections of fetal kidneys demonstrated delayed maturation, with disorganized glomerular generations and increased cortical thickness. This renal dysmorphology was not accompanied by structural or functional changes indicative of renal insufficiency. CONCLUSION: Our study demonstrates fetal bioaccumulation of metformin with associated fetal growth restriction and renal dysmorphology after maternal initiation of the drug within 30 days of conception in primates. Given these results and the prevalence of metformin use during pregnancy, additional investigation of any potential immediate and enduring effects of prenatal metformin use is warranted.

Novel protective aspects of dietary polyphenols against pesticidal toxicity and its prospective application in rice-fish mode: A Review.

The rice fish system represents an innovative and sustainable approach to integrated farming, combining rice cultivation with fish rearing in the same ecosystem. However, one of the major challenges in this system is the pesticidal pollution resulting from various sources, which poses risks to fish health and overall ecosystem balance. In recent years, dietary polyphenols have emerged as promising bioactive compounds with potential chemo-preventive and therapeutic properties. These polyphenols, derived from various plant sources, have shown great potential in reducing the toxicity of pesticides and improving the health of fish within the rice fish system. This review aims to explore the novel aspects of using dietary polyphenols to mitigate pesticidal toxicity and enhance fish health in the rice fish system. It provides comprehensive insights into the mechanisms of action of dietary polyphenols and their beneficial effects on fish health, including antioxidant, anti-inflammatory, and detoxification properties. Furthermore, the review discusses the potential application methods of dietary polyphenols, such as direct supplementation in fish diets or through incorporation into the rice fields. By understanding the interplay between dietary polyphenols and pesticides in the rice fish system, researchers can develop innovative and sustainable strategies to promote fish health, minimize pesticide impacts, and ensure the long-term viability of this integrated farming approach. The information presented in this review will be valuable for scientists, aqua-culturists, and policymakers aiming to implement eco-friendly and health-enhancing practices in the rice fish system.

Exposure Effects of Environmentally Relevant Concentrations of the Tricyclic Antidepressant Amitriptyline in Early Life Stage Zebrafish.

Antidepressants are one of the most globally prescribed classes of pharmaceuticals, and drug target conservation across phyla means that nontarget organisms may be at risk from the effects of exposure. Here, we address the knowledge gap for the effects of chronic exposure (28 days) to the tricyclic antidepressant amitriptyline (AMI) on fish, including for concentrations with environmental relevance, using zebrafish (Danio rerio) as our experimental model. AMI was found to bioconcentrate in zebrafish, was readily transformed to its major active metabolite nortriptyline, and induced a pharmacological effect (downregulation of the gene encoding the serotonin transporter; slc6a4a) at environmentally relevant concentrations (0.03 µg/L and above). Exposures to AMI at higher concentrations accelerated the hatch rate and reduced locomotor activity, the latter of which was abolished after a 14 day period of depuration. The lack of any response on the features of physiology and behavior we measured at concentrations found in the environment would indicate that AMI poses a relatively low level of risk to fish populations. The pseudopersistence and likely presence of multiple drugs acting via the same mechanism of action, however, together with a global trend for increased prescription rates, mean that this risk may be underestimated using current ecotoxicological assessment paradigms.

First Evidence of the Bioaccumulation and Trophic Transfer of Tire Additives and Their Transformation Products in an Estuarine Food Web.

The discovery of the significant lethal impacts of the tire additive transformation product N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6PPD-Q) on coho salmon has garnered global attention. However, the bioaccumulation and trophic transfer of tire additives and their transformation products (TATPs) within food webs remain obscure. This study first characterized the levels and compositions of 15 TATPs in the Pearl River Estuary, estimated their bioaccumulation and trophic transfer potential in 21 estuarine species, and identified priority contaminants. Our observations indicated that TATPs were prevalent in the estuarine environment. Eight, six, seven, and 10 TATPs were first quantified in the shrimp, sea cucumber, snail, and fish samples, with total mean levels of 45, 56, 64, and 67 ng/g (wet weight), respectively. N,N'-Diphenyl-p-phenylenediamine (DPPD) and N,N'-bis(2-methylphenyl)-1,4-benzenediamine (DTPD) exhibited high bioaccumulation. Significant biodilution was only identified for benzothiazole, while DPPD and DTPD displayed biomagnification trends based on Monte Carlo simulations. The mechanisms of bioaccumulation and trophodynamics of TATPs could be explained by their chemical hydrophobicity, molecular mass, and metabolic rates. Based on a multicriteria scoring technique, DPPD, DTPD, and 6PPD-Q were characterized as priority contaminants. This work emphasizes the importance of biomonitoring, particularly for specific hydrophobic tire additives.

Stimulated Raman Scattering Microscopy Reveals Bioaccumulation of Small Microplastics in Protozoa from Natural Waters.

Microplastics (MPs) are pollutants of global concern, and bioaccumulation determines their biological effects. Although microorganisms form a large fraction of our ecosystem's biomass and are important in biogeochemical cycling, their accumulation of MPs has never been confirmed in natural waters because current tools for field biological samples can detect only MPs > 10 µm. Here, we show that stimulated Raman scattering microscopy (SRS) can image and quantify the bioaccumulation of small MPs (<10 µm) in protozoa. Our label-free method, which differentiates MPs by their SRS spectra, detects individual and mixtures of different MPs (e.g., polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, polystyrene, and poly(methyl methacrylate)) in protozoa. The ability of SRS to quantify cellular MP accumulation is similar to that of flow cytometry, a fluorescence-based method commonly used to determine cellular MP accumulation. Moreover, we discovered that protozoa in water samples from Yangtze River, Xianlin Wastewater Treatment Plant, Lake Taihu and the Pearl River Estuary accumulated MPs < 10 µm, but the proportion of MP-containing cells was low (∼2-5%). Our findings suggest that small MPs could potentially enter the food chain and transfer to organisms at higher trophic levels, posing environmental and health risks that deserve closer scrutiny.

Bioaccumulation and Male Reproductive Toxicity of the New Brominated Flame Retardant Tetrabromobisphenol A-Bis(2,3-dibromo-2-methylpropyl ether) in Comparison with Hexabromocyclododecane.

Tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether) (TBBPA-DBMPE) has come into use as an alternative to hexabromocyclododecane (HBCD), but it is unclear whether TBBPA-DBMPE has less hazard than HBCD. Here, we compared the bioaccumulation and male reproductive toxicity between TBBPA-DBMPE and HBCD in mice following long-term oral exposure after birth. We found that the concentrations of TBBPA-DBMPE in livers significantly increased with time, exhibiting a bioaccumulation potency not substantially different from HBCD. Lactational exposure to 1000 µg/kg/d TBBPA-DBMPE as well as 50 µg/kg/d HBCD inhibited testis development in suckling pups, and extended exposure up to adulthood resulted in significant molecular and cellular alterations in testes, with slighter effects of 50 µg/kg/d TBBPA-DBMPE. When exposure was extended to 8 month age, severe reproductive impairments including reduced sperm count, increased abnormal sperm, and subfertility occurred in all treated animals, although 50 µg/kg/d TBBPA-DBMPE exerted lower effects than 50 µg/kg/d HBCD. Altogether, all data led us to conclude that TBBPA-DBMPE exerted weaker male reproductive toxicity than HBCD at the same doses but exhibited bioaccumulation potential roughly equivalent to HBCD. Our study fills the data gap regarding the bioaccumulation and toxicity of TBBPA-DBMPE and raises concerns about its use as an alternative to HBCD.

Toxicokinetics of the Antidepressant Fluoxetine and Its Active Metabolite Norfluoxetine in Caenorhabditis elegans and Their Comparative Potency.

The nematode Caenorhabditis elegans is a valuable model for ecotoxicological research, yet limited attention has been given to understanding how it absorbs, distributes, metabolizes, and excretes chemicals. This is crucial for C. elegans because the organism is known to have strong uptake barriers that are known to be susceptible to potential confounding effects of the presence of Escherichia coli as a food source. One frequently studied compound in C. elegans is the antidepressant fluoxetine, which has an active metabolite norfluoxetine. In this study, we evaluated the toxicokinetics and relative potency of norfluoxetine and fluoxetine in chemotaxis and activity tests. Toxicokinetics experiments were conducted with varying times, concentrations of fluoxetine, and in the absence or presence of E. coli, simulated with a one-compartment model. Our findings demonstrate that C. elegans can take up fluoxetine and convert it into norfluoxetine. Norfluoxetine proved slightly more potent and had a longer elimination half-life. The bioconcentration factor, uptake, and elimination rate constants depended on exposure levels, duration, and the presence of E. coli in the exposure medium. These findings expand our understanding of toxicokinetic modeling in C. elegans for different exposure scenarios, underlining the importance of considering norfluoxetine formation in exposure and bioactivity assessments of fluoxetine.

Geographic Drivers of Mercury Entry into Aquatic Food Webs Revealed by Mercury Stable Isotopes in Dragonfly Larvae.

Atmospheric mercury (Hg) emissions and subsequent transport and deposition are major concerns within protected lands, including national parks, where Hg can bioaccumulate to levels detrimental to human and wildlife health. Despite this risk to biological resources, there is limited understanding of the relative importance of different Hg sources and delivery pathways within the protected regions. Here, we used Hg stable isotope measurements within a single aquatic bioindicator, dragonfly larvae, to determine if these tracers can resolve spatial patterns in Hg sources, delivery mechanisms, and aquatic cycling at a national scale. Mercury isotope values in dragonfly tissues varied among habitat types (e.g., lentic, lotic, and wetland) and geographic location. Photochemical-derived isotope fractionation was habitat-dependent and influenced by factors that impact light penetration directly or indirectly, including dissolved organic matter, canopy cover, and total phosphorus. Strong patterns for Δ200Hg emerged in the western United States, highlighting the relative importance of wet deposition sources in arid regions in contrast to dry deposition delivery in forested regions. This work demonstrates the efficacy of dragonfly larvae as biosentinels for Hg isotope studies due to their ubiquity across freshwater ecosystems and ability to track variation in Hg sources and processing attributed to small-scale habitat and large-scale regional patterns.

Low Dietary Uptake Efficiencies and Biotransformation Prevent Biomagnification of Octamethylcyclotetrasiloxane (D4) and Decamethylcyclopentasiloxane (D5) in Rainbow Trout.

With octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5) being considered for evaluation under the UN Stockholm Convention on Persistent Organic Pollutants, which specifically acknowledges risks of biomagnification of persistent organic pollutants in traditional foods, a study into the mechanism of the biomagnification process of D4 and D5 in Rainbow trout was conducted by combining the absorption-distribution-metabolism-excretion for bioaccumulation (ADME-B) approach to determine intestinal and somatic biotransformation rates and radiochemical analyses to identify metabolite formation. High rates of intestinal biotransformation of D4 and D5 (i.e., 2.1 (0.70 SE) and 0.88 (0.67 SE) day-1, respectively) and metabolite formation [i.e., 52.0 (17 SD)% of D4 and 56.5% (8.2 SD)% of D5 were metabolized] were observed that caused low dietary uptake efficiencies of D4 and D5 in fish of 15.5 (2.9 SE)% and 21.0 (6.5 SE)% and biomagnification factors of 0.44 (0.08 SE) for D4 and 0.78 (0.24 SE) kg-lipid·kg-lipid-1 for D5. Bioaccumulation profiles indicated little effect of growth dilution on the bioaccumulation of D4 and D5 in fish and were substantially different from those of PCB153. The study highlights the importance of intestinal biotransformation in negating biomagnification of substances in organisms and explains differences between laboratory tests and field observations of bioaccumulation of D4 and D5.

Tissue-Specific Accumulation of Orally Administered Short- and Medium-Chain Chlorinated Paraffins in Honeybees (Apis mellifera L.).

The prevalence and distribution of chlorinated paraffins (CPs) have been extensively studied in various matrices and organisms; however, there is a lack of information about insects, particularly in honeybees. To address this gap, we studied young honeybee workers exposed to short- and medium-chain CPs (SCCPs and MCCPs) at an environmentally relevant concentration of 10 mg/L for 7 days, followed by a 7-day elimination period. Results indicated that CPs could transfer into the head after oral consumption and SCCPs and MCCPs exhibited clear bioaccumulation trends: midgut > hindgut > head. An evaluation of congener group distribution patterns demonstrated that the dominant congener groups in all target tissues were C11-13Cl7-8 and C14Cl7-8 for SCCPs and MCCPs, respectively, consistent with the treated CP standards. In honeybees, a significant negative relationship was observed for the log concentration of MCCP congener groups and their log KOW, but not with their log KOA. Conversely, no such correlation was found for SCCPs. These findings suggest that honeybees have a high potential to bioaccumulate MCCPs, particularly those with a low log KOW, and exhibit weak selectivity for SCCPs.

Assessing Per- and Polyfluoroalkyl Substances in Fish Fillet Using Non-Targeted Analyses.

Per- and polyfluoroalkyl substances (PFAS) are a class of thousands of man-made chemicals that are persistent and highly stable in the environment. Fish consumption has been identified as a key route of PFAS exposure for humans. However, routine fish monitoring targets only a handful of PFAS, and non-targeted analyses have largely only evaluated fish from heavily PFAS-impacted waters. Here, we evaluated PFAS in fish fillets from recreational and drinking water sources in central North Carolina to assess whether PFAS are present in these fillets that would not be detected by conventional targeted methods. We used liquid chromatography, ion mobility spectrometry, and mass spectrometry (LC-IMS-MS) to collect full scan feature data, performed suspect screening using an in-house library of 100 PFAS for high confidence feature identification, searched for additional PFAS features using non-targeted data analyses, and quantified perfluorooctanesulfonic acid (PFOS) in the fillet samples. A total of 36 PFAS were detected in the fish fillets, including 19 that would not be detected using common targeted methods, with a minimum of 6 and a maximum of 22 in individual fish. Median fillet PFOS levels were concerningly high at 11.6 to 42.3 ppb, and no significant correlation between PFOS levels and number of PFAS per fish was observed. Future PFAS monitoring in this region should target more of these 36 PFAS, and other regions not considered heavily PFAS contaminated should consider incorporating non-targeted analyses into ongoing fish monitoring studies.

Integration of Nontarget Screening and QSPR Models to Identify Novel Organophosphate Esters of High Priority in Aquatic Environment.

With the development of large numbers of novel organophosphate esters (OPEs) alternatives, it is imperative to screen and identify those with high priority. In this study, surface water, biofilms, and freshwater snails were collected from the flow-in rivers of Taihu Lake Basin, China. Screened by target, suspect, and nontarget analysis, 11 traditional and 14 novel OPEs were identified, of which 5 OPEs were first discovered in Taihu Lake Basin. The OPE concentrations in surface water ranged from 196 to 2568 ng/L, with the primary homologue tris(2,4-ditert-butylphenyl) phosphate (TDtBPP) being newly identified, which was likely derived from the transformation of tris(2,4-ditert-butylphenyl) phosphite. The majority of the newly identified OPEs displayed substantially higher bioaccumulation and biomagnification potentials in the biofilm-snail food chain than the traditional ones. Quantitative structure-property relationship models revealed both hydrophobicity and polarity influenced the bioaccumulation and biomagnification of the OPEs, while electrostatic attraction also had a contribution to the bioaccumulation in the biofilm. TDtBPP was determined as the utmost priority by toxicological priority index scheme, which integrated concentration, bioaccumulation, biomagnification, acute toxicity, and endocrine disrupting potential of the identified OPEs. These findings provide novel insights into the behaviors of OPEs and scientific bases for better management of high-risk pollutants in aquatic ecosystem.

Biotransformation, Bioaccumulation, and Bioelimination of Triphenyl Phosphate and Its Dominant Metabolite Diphenyl Phosphate In Vivo.

Aryl phosphorus flame retardants (aryl-PFRs), such as triphenyl phosphate (TPHP) and diphenyl phosphate (DPHP), are widely used worldwide. Understanding the fates of aryl-PFRs in vivo is crucial to assessing their toxicity and the risks they pose. Seven TPHP metabolites, including Phase I hydrolysis and hydroxylation and Phase II glucuronidation products, were identified in C57BL/6J male mice following subacute dietary exposure to aryl-PFRs (70 µg/kg body weight (bw)/day) for 7 days. TPHP was almost completely metabolized by mice (∼97%), with DPHP the major metabolite formed (34%-58%). In addition, mice were exposed to aryl-PFRs (7 µg/kg bw/day) for 12 weeks. Both TPHP and DPHP occurred at higher concentrations in the digestive tract (intestine and stomach), liver and heart. The total concentration of DPHP in all organs was 3.55-fold greater than that of TPHP. Recovery analysis showed that the rate of TPHP elimination from mouse organs reached 38%, while only 3%-5% of DPHP was removed, suggesting that the rates of degradation and elimination of DPHP were slower than TPHP and its bioaccumulation potential was higher. These results highlight the critical role of DPHP in the biotransformation, bioaccumulation, and bioelimination of TPHP, providing valuable insights into the fate of aryl-PFRs in vivo.

Microplastic Contamination of a Benthic Ecosystem in a Hydrothermal Vent.

Plastic contamination is a global pervasive issue, extending from coastal areas and open oceans to polar regions and even the deep sea. Microplastic (MP) contamination in hydrothermal vents, which are known for their high biodiversity even under extreme conditions, has remained largely unexplored. Here, we present, for the first time, MP pollution in a deep-sea hydrothermal vent at one of the biodiversity hotspots─the Central Indian Ridge. Not only the environment (seawater: 2.08 ± 1.04 MPs/L, surface sediments: 0.57 ± 0.19 MP/g) but also all six major benthic species investigated were polluted by MPs. MPs mainly consisted of polypropylene, polyethylene terephthalate, and polystyrene fragments ≤100 µm and were characterized as being either transparent or white in color. Remarkably, bioaccumulation and even biomagnification of microplastics were observed in the top predators of the ecosystem, such as squat lobsters (14.25 ± 4.65 MPs/individual) and vent crabs (14.00 ± 2.16 MPs/individual), since they contained more MPs than animals at lower trophic levels (e.g., mussels and snails, 1.75-6.00 average MPs/individuals). These findings reveal MP contamination of an ecosystem in a hydrothermal vent, thereby suggesting that their accumulation and magnification can occur in top-level animals, even within remote and extreme environments.

Occurrence, Spatial Distribution, and Bioaccumulation of Dissolved Synthetic Musks in Freshwaters across China.

Commercial chemicals, such as synthetic musks, are of global concern, but data on their occurrence and spatial distribution in aquatic environments of large scale are scarce. Two sampling campaigns were conducted in the present study to measure freely dissolved synthetic musks in freshwaters across China using passive samplers, along with biological coexposure at selected sites. Polycyclic musks (PCMs) dominated synthetic musks, with a detection frequency of 95%. Higher concentrations of PCMs were observed in densely populated Mid, East, and South China compared to less populated regions, indicating the significance of anthropogenic activities for synthetic musks in water. The concentration ratios of galaxolide (HHCB)/tonalide (AHTN) were significantly higher in low-latitude areas than in high-latitude areas from June to September, suggesting that solar radiation played an important role in the degradation of HHCB/AHTN. Significant correlations were found between dissolved concentrations of HHCB and AHTN and their lipid-normalized concentrations in coexposed fish and clam. The estimated hazard quotients for HHCB and AHTN in freshwater fish consumed by humans were less than 0.01 at all sampling sites except the Yangtze River Basin. These results help to understand the environmental fate and ecological risks of synthetic musks on a large geographical scale.

Scalable and Consolidated Microbial Platform for Rare Earth Element Leaching and Recovery from Waste Sources.

Chemical methods for the extraction and refinement of technologically critical rare earth elements (REEs) are energy-intensive, hazardous, and environmentally destructive. Current biobased extraction systems rely on extremophilic organisms and generate many of the same detrimental effects as chemical methodologies. The mesophilic methylotrophic bacterium Methylobacterium extorquens AM1 was previously shown to grow using electronic waste by naturally acquiring REEs to power methanol metabolism. Here we show that growth using electronic waste as a sole REE source is scalable up to 10 L with consistent metal yields without the use of harsh acids or high temperatures. The addition of organic acids increases REE leaching in a nonspecific manner. REE-specific bioleaching can be engineered through the overproduction of REE-binding ligands (called lanthanophores) and pyrroloquinoline quinone. REE bioaccumulation increases with the leachate concentration and is highly specific. REEs are stored intracellularly in polyphosphate granules, and genetic engineering to eliminate exopolyphosphatase activity increases metal accumulation, confirming the link between phosphate metabolism and biological REE use. Finally, we report the innate ability of M. extorquens to grow using other complex REE sources, including pulverized smartphones, demonstrating the flexibility and potential for use as a recovery platform for these critical metals.

Distribution and Homogenization of Multiple Mercury Species Inputs to Freshwater Wetland Mesocosms.

Mercury (Hg)-impaired aquatic ecosystems often receive multiple inputs of different Hg species with varying potentials for transformation and bioaccumulation. Over time, these distinct input pools of Hg homogenize in their relative distributions and bioaccumulation potentials as a result of biogeochemical processes and other aging processes within the ecosystem. This study sought to evaluate the relative time scale for homogenization of multiple Hg inputs to wetlands, information that is relevant for ecosystem management strategies that consider Hg source apportionment. We performed experiments in simulated freshwater wetland mesocosms that were dosed with four isotopically labeled mercury forms: two dissolved forms (Hg2+ and Hg-humic acid) and two particulate forms (nano-HgS and Hg adsorbed to FeS). Over the course of one year, we monitored the four Hg isotope endmembers for their relative distribution between surface water, sediment, and fish in the mesocosms, partitioning between soluble and particulate forms, and conversion to methylated mercury (MeHg). We also evaluated the reactivity and mobility of Hg through sequential selective extractions of sediment and the uptake flux of aqueous Hg in a diffusive gradient in thin-film (DGT) passive samplers. We observed that the four isotope spikes were relatively similar in surface water concentration (ca. 3000 ng/L) immediately after spike addition. At 1-3 months after dosing, Hg concentrations were 1-50 ng/L and were greater for the initially dissolved isotope endmembers than the initially particulate endmembers. In contrast, the Hg isotope endmembers in surface sediments were similar in relative concentration within 2 months after spike addition. However, the uptake fluxes of Hg in DGT samplers, deployed in both the water column and surface sediment, were generally greater for initially dissolved Hg endmembers and lower for initially particulate endmembers. At one year postdosing, the DGT-uptake fluxes were converging toward similar values between the Hg isotope endmembers. However, the relative distribution of isotope endmembers was still significantly different in both the water column and sediment (p < 0.01 according to one-way ANOVA analysis). In contrast, selective sequential extractions resulted in a homogeneous distribution, with >90% of each endmember extracted in the KOH fraction, suggesting that Hg species were associated with sediment organic matter. For MeHg concentrations in surface sediment and fish, the relative contributions from each endmember were significantly different at all sampling time points. Altogether, these results provide insights into the time scales of distribution for different Hg species that enter a wetland ecosystem. While these inputs attain homogeneity in concentration in primary storage compartments (i.e., sediments) within weeks after addition, these input pools remain differentiated for more than one year in terms of reactivity for passive samplers, MeHg concentration, and bioaccumulation.

Distribution Control and Environmental Fate of PFAS in the Offshore Region Adjacent to the Yangtze River Estuary─A Study Combining Multiple Phases Analysis.

The Yangtze River Estuary is the terminal sink of terrestrial per- and polyfluoroalkyl substances (PFAS) from the Yangtze River, while the environmental fate characteristics of legacy and emerging PFAS around this region have rarely been discussed. Here, 24 targeted PFAS in seawater, sediments, suspended particulate matter (SPM), and plankton in the offshore region adjacent to this estuary were investigated. The three dominant PFAS in all phases were perfluorooctanoic acid (PFOA, 23.8-61.9%), perfluorobutanoic acid (PFBA, 23.6-42.8%), and perfluoro(2-methyl-3-oxahexanoic) acid (HFPO-DA, 6.1-12.1%), and perfluoro-1-butane sulfonamide (FBSA, 0.1-7.3%) was first detected. The horizontal distributions of PFAS were dependent on salinity and disturbed by multiple water masses, while the vertical variations could be explained by their different partitioning characteristics in the water-SPM-sediment system (partition coefficients, Log Kd and Log Koc) and plankton (bioaccumulation factors, Log BAF). Although physical mixing was the major driver for PFAS settling (>83.7%), the absolute settling amount caused by the biological pump was still high (150.00-41994.65 ng m-2 day-1). More importantly, we found unexpected high Log Kd values of PFBA (2.24-4.55) and HFPO-DA (2.26-4.67), equal to PFOA (2.28-4.72), which brought concerns about their environmental persistence. Considering the increased detection of short-chain and emerging PFAS, more comprehensive environmental behaviors analysis is required urgently.