Contributions of long-range transport from the Asian continent and local emissions on atmospheric PM2.5, polycyclic aromatic hydrocarbons, and their nitro-derivatives in Kanazawa and Noto Peninsula, Japan.

This study collected samples of particulate matter that are 2.5 µm or less in diameter (PM2.5) in Kanazawa, Japan, and Noto Peninsula located 100 km north on the windward side of the westerlies from the Asian continent and characterized the extent of polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs (NPAHs) pollution in Kanazawa. Emission areas and specific sources of PM2.5 and of PAHs and NPAHs were clarified via back-trajectory analysis and the NP-method, respectively. The results indicate that during 2020 and 2021, most PAHs (93%) in Kanazawa were transported from the Asian continent by westerlies and that the main source was coal and biomass combustion. The presence of NPAHs in Kanazawa was caused by a mixture of transport from the Asian continent (53%) and local emissions (47%), with the main source of the latter being from vehicles. Although the content of combustion-derived particulates (Pc) was <2.4% of PM2.5 in Kanazawa, this showed a similar seasonal variation (winter > summer) to that of PAHs. The contribution of Pc transported from the Asian continent exceeded that of locally emitted Pc. The current situation of Kanazawa is considerably different from that of 1997, when local vehicles were the main source of pollution.

The molecular level degradation state of drift plastics in the Sea of Japan coastline.

Polyethylene (PE) and polyethylene terephthalate (PET) are among the most abundant plastics polluting the oceans. However, their environmental fate depends on how they have been weathered. Due to its unique geography, the Sea of Japan is a pollution hotspot where plastics accumulate. In this study, the structures of plastics, having drifted into the Sea of Japan coastline environment, were analyzed with a particular focus on examining polymer crystallization and carbonyl formation; two factors which influence microplastic formation and the adsorption of contaminants onto plastic surfaces. PE in the coastal environment did not show evidence of crystallization, although carbonyl formation did increase. By contrast, PET bottles were shown to not be uniform in structure, with unaged bottles being less crystalline in the neck component compared to the body. Because of this difference, in environmental PET bottles, it was the bottle neck that showed increases in crystallization and carbonyl group formation.

Differences in microplastic degradation in the atmosphere and coastal water environment from two island nations: Japan and New Zealand.

Microplastics are subject to environmental forces that can change polymer organization on a molecular scale. However, it is not clear to what extent these changes occur in the environment and whether microplastics in the atmospheric and water environment differ. Here we identify structural differences between microplastics in the atmosphere and water environment from Japan and New Zealand, representing two archipelagos differing in their proximity to nearby countries and highly populated areas. We first highlight the propensity for smaller microplastics to arrive via air masses from the Asian continent to the Japan Sea coastal area, while New Zealand received larger, locally derived microplastics. Analyses of polyethylene in the Japanese atmosphere indicate that microplastics transported to the Japanese coastal areas were more crystalline than polyethylene particles in the water, suggesting that the plastics arriving by air were relatively more aged and brittle. By contrast, polypropylene particles in New Zealand waters were more degraded than the microplastic particles in the air. Due to the lack of abundance, both polyethylene and polypropylene could not be analyzed for both countries. Nevertheless, these findings show the structural variation in microplastics between environments in markedly different real-world locations, with implications for the toxic potential of these particles.

Abundance and characterization of microplastics in amphipods from the Japanese coastal environment.

Microplastics can be ingested by tiny detritivores such as amphipods, with potential consequences on the food chain. The present study characterizes the abundance, chemical composition, and size of microplastics in amphipods found in the Japan Sea coastal environment, which is a hotspot for microplastic accumulation. High amounts of microplastic ingestion and a large discrepancy by amphipod species, Talorchestia nipponensis, Ampithoe valida, and Trinorchestia trinitatis, were observed (between 0.2 and 76.3 particles/individual) which may be due to differences in habitat preference and background contamination. This result indicates that coastal amphipods in particular may ingest large amounts of microplastics. The average microplastic particle size in amphipods was 59 ± 8.6 µm, with 83% of particles smaller than 90 µm, and polyethylene was dominant. This study provides insights into microplastic abundance in coastal amphipods and the context for further studies on coastal amphipod microplastic ingestion.

Hydroxylated benzo[c]phenanthrene metabolites cause osteoblast apoptosis and skeletal abnormalities in fish.

To study the toxicity of 3-hydroxybenzo[c]phenanthrene (3-OHBcP), a metabolite of benzo[c]phenanthrene (BcP), first we compared it with its parent compound, BcP, using an in ovo-nanoinjection method in Japanese medaka. Second, we examined the influence of 3-OHBcP on bone metabolism using goldfish. Third, the detailed mechanism of 3-OHBcP on bone metabolism was investigated using zebrafish and goldfish. The LC50s of BcP and 3-OHBcP in Japanese medaka were 5.7 nM and 0.003 nM, respectively, indicating that the metabolite was more than 1900 times as toxic as the parent compound. In addition, nanoinjected 3-OHBcP (0.001 nM) induced skeletal abnormalities. Therefore, fish scales with both osteoblasts and osteoclasts on the calcified bone matrix were examined to investigate the mechanisms of 3-OHBcP toxicity on bone metabolism. We found that scale regeneration in the BcP-injected goldfish was significantly inhibited as compared with that in control goldfish. Furthermore, 3-OHBcP was detected in the bile of BcP-injected goldfish, indicating that 3-OHBcP metabolized from BcP inhibited scale regeneration. Subsequently, the toxicity of BcP and 3-OHBcP to osteoblasts was examined using an in vitro assay with regenerating scales. The osteoblastic activity in the 3-OHBcP (10-10 to 10-7 M)-treated scales was significantly suppressed, while BcP (10-11 to 10-7 M)-treated scales did not affect osteoblastic activity. Osteoclastic activity was unchanged by either BcP or 3-OHBcP treatment at each concentration (10-11 to 10-7 M). The detailed toxicity of 3-OHBcP (10-9 M) in osteoblasts was then examined using gene expression analysis on a global scale with fish scales. Eight genes, including APAF1, CHEK2, and FOS, which are associated with apoptosis, were identified from the upregulated genes. This indicated that 3-OHBcP treatment induced apoptosis in fish scales. In situ detection of cell death by TUNEL methods was supported by gene expression analysis. This study is the first to demonstrate that 3-OHBcP, a metabolite of BcP, has greater toxicity than the parent compound, BcP.

Calculating source contributions to urban atmospheric polycyclic aromatic hydrocarbons and nitropolycyclic aromatic hydrocarbons using 1-nitropyrene and pyrene: An application to an Asian dust event.

A method to calculate source contributions to atmospheric polycyclic aromatic hydrocarbons (PAHs) and their nitrated congeners (NPAHs) is proposed, using pyrene (Pyr) and 1-nitropyrene (1-NP), as respective representatives of PAHs and NPAHs. This is based on the known increases in NPAH to PAH ratios as combustion temperatures increase. The fractions of 1-NP and Pyr from high temperature combustion sources in total 1-NP and Pyr are respectively calculated as a (0 < a <1) and b (0 < b < 1). By using atmospheric concentrations of Pyr and 1-NP obtained at monitoring sites, contributions of high and low temperature combustion sources were calculated. Using this method, the contributions of automobiles and coal combustion facilities/industries to atmospheric Pyr and 1-NP concentrations were calculated for atmospheric samples collected in Kanazawa, Japan during a seasonal Asian dust event. The results show that Pyr was almost entirely emitted from industries in China and transported long-range to Japan. By contrast, 1-NP was emitted primarily from automobiles in Kanazawa and its surrounding areas, with a small amount of 1-NP possibly transported from China. The proposed method can provide greater clarity on source identification compared to the typically used PAH isomer pairs.

Calculating sources of combustion-derived particulates using 1-nitropyrene and pyrene as markers.

Airborne particulate matter (PM) contains numerous hazardous polycyclic aromatic hydrocarbons (PAHs) as well as their functionalized congeners. However, the lack of useful methods to identify the sources of PM has hindered the development of researches in atmospheric and public health fields. This report proposes a new method for estimating the source contribution of combustion-derived particulate (Pc) by using 1-nitropyrene (1-NP) and pyrene (Pyr) as markers. This is premised on the fact that the formation of nitrogen oxides in the flame gas and the subsequent nitration of PAHs are functions of combustion temperature and therefore the concentration ratios of NPAHs to PAHs are highly temperature dependent. This method divides combustion sources into two groups - high and low temperatures - which here are respectively represented by automobile engine and coal combustion in urban areas. Formulae are derived for combustion-derived particulate (Pc), whose fraction in the total particulate is y (0 < y < 1), and particulates from combustion sources with high temperatures (Ph), whose fraction in Pc is x (0 < x < 1), and low temperatures (Pl), whose fraction is (1 －x). When concentrations of 1-NP and Pyr in Ph and Pl are known, values x and y can be calculated from the formulae by determining atmospheric 1-NP and Pyr concentrations at monitoring sites. Then atmospheric concentrations of Pc, Ph and Pl can be calculated. The proposed method has been applied for total suspended particulate matter (TSP) samples collected in Kanazawa and Kitakyushu (Japan) and Beijing (China) having different types of atmospheric pollution to clarify the change of contributions of automobiles and coal combustion.

Comparison of metabolomic responses of earthworms to sub-lethal imidacloprid exposure in contact and soil tests.

Eisenia fetida earthworms were exposed to sub-lethal levels of imidacloprid for 48 h via contact filter paper tests and soil tests. After the exposure, 1H nuclear magnetic resonance (NMR) metabolomics was used to measure earthworm sub-lethal responses by analyzing the changes in the polar metabolite profile. Maltose, glucose, malate, lactate/threonine, myo-inositol, glutamate, arginine, lysine, tyrosine, leucine, and phenylalanine relative concentrations were altered with imidacloprid exposure in soil. In addition to these metabolites (excluding leucine and phenylalanine), fumarate, ATP, inosine, betaine, scyllo-inositol, glutamine, valine, tryptophan, alanine, tyrosine, and isoleucine relative concentrations shifted with imidacloprid exposure during contact tests. Metabolite changes in E. fetida earthworms exposed to imidacloprid showed a non-linear concentration response and an upregulation in gluconeogenesis. Overall, imidacloprid exposure in soil induces a less pronounced response in metabolites glucose, maltose, fumarate, adenosine-5'-triphosphate (ATP), inosine, scyllo-inositol, lactate/threonine, and tyrosine in comparison to the response observed via contact tests. Thus, our study highlights that tests in soil can result in a different metabolic response in E. fetida and demonstrates the importance of different modes of exposure and the extent of metabolic perturbation in earthworms. Our study also emphasizes the underlying metabolic disruption of earthworms after acute sub-lethal exposure to imidacloprid. These observations should be further examined in different soil types to assess the sub-lethal toxicity of imidacloprid to soil-dwelling earthworms.

The presence of nitroarenes formed by secondary atmospheric processes in the Japanese freshwater environment.

In this study, the concentrations and distributions of nitrated polycyclic aromatic hydrocarbons (NPAHs) were characterized in the freshwater environment of a Japanese city. While the NPAHs were few in number, they were found in pg/L concentrations and the specific isomers suggested the deposition of NPAHs formed via the atmospheric transformation of PAHs. The absence of NPAHs formed via primary combustion processes such as automobile exhaust, suggests that improvements in emission standards are being reflected in the environment, though the NPAHs formed by secondary atmospheric processes are still a significant ecotoxicological threat. The stability of the NPAHs was also examined in spiked freshwater matrices. There was a significant decrease in spiked NPAHs over this period, suggesting that they were either being sorbed or transformed and are therefore not long lived in the freshwater environment. This indicates that the NPAHs found in freshwater samples are from recent deposition.

Sources and Characteristics of Polycyclic Aromatic Hydrocarbons in Ambient Total Suspended Particles in Ulaanbaatar City, Mongolia.

The purpose of this study was to identify pollution sources by characterizing polycyclic aromatic hydrocarbons from total suspended particles in Ulaanbaatar City. Fifteen polycyclic aromatic hydrocarbons were measured in total suspended particle samples collected from different sites, such as the urban center, industrial district and ger (Mongolian traditional house) areas, and residential areas both in heating (January, March), and non-heating (September) periods in 2017. Polycyclic aromatic hydrocarbon concentration ranged between 131 and 773 ng·m-3 in winter, 22.2 and 530.6 ng·m-3 in spring, and between 1.4 and 54.6 ng·m-3 in autumn. Concentrations of specific polycyclic aromatic hydrocarbons such as phenanthrene were higher in the ger area in winter and spring seasons, and the pyrene concentration was dominant in late summer in the residential area. Polycyclic aromatic hydrocarbons concentrations in the ger area were particularly higher than the other sites, especially in winter. Polycyclic aromatic hydrocarbon ratios indicated that vehicle emissions were likely the main source at the city center in the winter time. Mixed contributions from biomass, coal, and petroleum combustion were responsible for the particulate polycyclic aromatic hydrocarbon pollution at other sampling sites during the whole observation period. The lifetime inhalation cancer risk values in the ger area due to winter pollution were estimated to be 1.2 × 10-5 and 2.1 × 10-5 for child and adult exposures, respectively, which significantly exceed Environmental Protection Agency guidelines.

Improvements in polycyclic aromatic hydrocarbon contamination in the Japan Sea: An interannual survey from 2008 to 2014.

The concentrations and distributions of polycyclic aromatic hydrocarbons (PAHs) were examined from 2008 to 2014 in the surface waters of the Japan Sea region. PAH concentrations decreased in the Japan Sea and Tsushima Strait; consistent with improvements in atmospheric pollution from Japan. There were no changes in the Korean Strait, suggesting a continual influx of contamination separate from the Japan Sea. At all sites, PAHs in the dissolved phase were greater than in the particulate phase. A separate survey in 2011 studied whether contamination in the Kuroshio current accounted for the contamination in the Tsushima strait and Japan Sea. PAH concentrations increased as waters moved into the Tsushima strait and the Japan Sea, suggesting inputs were local and not from the Kuroshio current. This was however confounded by the greater influence of particulate phase PAHs, which are likely deposited by seasonal desert storms.

Characterization and Risk Assessment of Atmospheric PM2.5 and PM10 Particulate-Bound PAHs and NPAHs in Rwanda, Central-East Africa.

Exposure to airborne particulates is estimated as the largest cause of premature human mortality worldwide and is of particular concern in sub-Saharan Africa where emissions are high and data are lacking. Particulate matter (PM) contains several toxic organic species including polycyclic aromatic hydrocarbons (PAHs) and nitrated PAHs (NPAHs). This study provides the first characterization and source identification for PM10- and PM2.5-bound PAHs and NPAHs in sub-Saharan Africa during a three-month period that spanned dry and wet seasons at three locations in Rwanda. The 24-h mean PM2.5 and PM10 concentrations were significantly higher in the dry than the wet season. PAH and NPAH concentrations at the urban roadside site were significantly higher than the urban background and rural site. Source identification using diagnostic ratio analysis and principal component analysis (PCA) revealed diesel and gasoline-powered vehicles at the urban location and wood burning at the rural location as the major sources of PAHs and NPAHs. Our analysis demonstrates that PM concentrations and lifetime cancer risks resulting from inhalation exposure to PM-bound PAHs and NPAHs exceed World Health Organization safe limits. This study provides clear evidence that an immediate development of emission control measures is required.

Analysis of Sub-Lethal Toxicity of Perfluorooctane Sulfonate (PFOS) to Daphnia magna Using ¹H Nuclear Magnetic Resonance-Based Metabolomics.

¹H nuclear magnetic resonance (NMR)-based metabolomics was used to characterize the response of Daphnia magna after sub-lethal exposure to perfluorooctane sulfonate (PFOS), a commonly found environmental pollutant in freshwater ecosystems. Principal component analysis (PCA) scores plots showed significant separation in the exposed samples relative to the controls. Partial least squares (PLS) regression analysis revealed a strong linear correlation between the overall metabolic response and PFOS exposure concentration. More detailed analysis showed that the toxic mode of action is metabolite-specific with some metabolites exhibiting a non-monotonic response with higher PFOS exposure concentrations. Our study indicates that PFOS exposure disrupts various energy metabolism pathways and also enhances protein degradation. Overall, we identified several metabolites that are sensitive to PFOS exposure and may be used as bioindicators of D. magna health. In addition, this study also highlights the important utility of environmental metabolomic methods when attempting to elucidate acute and sub-lethal pollutant stressors on keystone organisms such as D. magna.

Metabolomics reveals energetic impairments in Daphnia magna exposed to diazinon, malathion and bisphenol-A.

(1)H nuclear magnetic resonance (NMR)-based metabolomics was used to study the response of Daphnia magna to increasing sub-lethal concentrations of either an organophosphate (diazinon or malathion) or bisphenol-A (BPA). Principal component analysis (PCA) of (1)H NMR spectra were used to screen metabolome changes after 48h of contaminant exposure. The PCA scores plots showed that diazinon exposures resulted in aberrant metabolomic profiles at all exposure concentrations tested (0.009-0.135 µg/L), while for malathion the second lowest (0.08µg/L) and two highest exposure concentrations (0.32µg/L and 0.47µg/L) caused significant shifts from the control. Individual metabolite changes for both organophosphates indicated that the response to increasing exposure was non-linear and described perturbations in the metabolome that were characteristic of the severity of exposure. For example, intermediate concentrations of diazinon (0.045µg/L and 0.09µg/L) and malathion (0.08µg/L) elicited a decrease in amino acids such as leucine, valine, arginine, glycine, lysine, glutamate, glutamine, phenylalanine and tyrosine, with concurrent increases in glucose and lactate, suggesting a mobilization of energy resources to combat stress. At the highest exposure concentrations for both organophosphates there was evidence of a cessation in metabolic activity, where the same amino acids increased and glucose and lactate decreased, suggesting a slowdown in protein synthesis and depletion of energy stocks. This demonstrated a similar response in the metabolome between two organophosphates but also that intermediate and severe stress levels could be differentiated by changes in the metabolome. For BPA exposures, the PCA scores plot showed a significant change in metabolome at 0.1mg/L, 1.4mg/L and 2.1mg/L of exposure. Individual metabolite changes from 0.7 to 2.1mg/L of BPA exposure showed increases in amino acids such as alanine, valine, isoleucine, leucine, arginine, phenylalanine and tyrosine. These metabolite changes were correlated with decreases in glucose and lactate. This pattern of response was also seen in the highest organophosphate exposures and suggested a generalized stress response that could be related to altered energy dynamics in D. magna. Through studying increasing exposure responses, we have demonstrated the ability of metabolomics to identify discrete differences between intermediate and severe stress, and also to characterize how systemic stress is manifested in the metabolome.

Analysis of Eisenia fetida earthworm responses to sub-lethal C60 nanoparticle exposure using (1)H-NMR based metabolomics.

The enhanced production and environmental release of Buckminsterfullerene (C60) nanoparticles will likely increase the exposure and risk to soil dwelling organisms. We used (1)H NMR-based metabolomics to investigate the response of Eisenia fetida earthworms to sub-lethal C60 nanoparticle exposure in both contact and soil tests. Principal component analysis of (1)H NMR data showed clear separation between controls and exposed earthworms after just 2 days of exposure, however as exposure time increased the separation decreased in soil but increased in contact tests suggesting potential adaptation during soil exposure. The amino acids leucine, valine, isoleucine and phenylalanine, the nucleoside inosine, and the sugars glucose and maltose emerged as potential bioindicators of exposure to C60 nanoparticles. The significant responses observed in earthworms using NMR-based metabolomics after exposure to very low concentrations of C60 nanoparticles suggests the need for further investigations to better understand and predict their sub-lethal toxicity.

Development of an NMR microprobe procedure for high-throughput environmental metabolomics of Daphnia magna.

Nuclear magnetic resonance (NMR) is the primary platform used in high-throughput environmental metabolomics studies because its non-selectivity is well suited for non-targeted approaches. However, standard NMR probes may limit the use of NMR-based metabolomics for tiny organisms because of the sample volumes required for routine metabolic profiling. Because of this, keystone ecological species, such as the water flea Daphnia magna, are not commonly studied because of the analytical challenges associated with NMR-based approaches. Here, the use of a 1.7-mm NMR microprobe in analyzing tissue extracts from D. magna is tested. Three different extraction procedures (D2O-based buffer, Bligh and Dyer, and acetonitrile : methanol : water) were compared in terms of the yields and breadth of polar metabolites. The D2O buffer extraction yielded the most metabolites and resulted in the best reproducibility. Varying amounts of D. magna dry mass were extracted to optimize metabolite isolation from D. magna tissues. A ratio of 1-1.5-mg dry mass to 40 µl of extraction solvent provided excellent signal-to-noise and spectral resolution using (1)H NMR. The metabolite profile of a single daphnid was also investigated (approximately 0.2 mg). However, the signal-to-noise of the (1)H NMR was considerably lower, and while feasible for select applications would likely not be appropriate for high-throughput NMR-based metabolomics. Two-dimensional NMR experiments on D. magna extracts were also performed using the 1.7-mm NMR probe to confirm (1)H NMR metabolite assignments. This study provides an NMR-based analytical framework for future metabolomics studies that use D. magna in ecological and ecotoxicity studies.

(1)H NMR-based metabolomics investigation of Daphnia magna responses to sub-lethal exposure to arsenic, copper and lithium.

Metal and metalloid contamination constitutes a major concern in aquatic ecosystems. Thus it is important to find rapid and reliable indicators of metal stress to aquatic organisms. In this study, we tested the use of (1)H nuclear magnetic resonance (NMR) - based metabolomics to examine the response of Daphnia magna neonates after a 48h exposure to sub-lethal concentrations of arsenic (49µgL(-1)), copper (12.4µgL(-1)) or lithium (1150µgL(-1)). Metabolomic responses for all conditions were compared to a control using principal component analysis (PCA) and metabolites that contributed to the variation between the exposures and the control condition were identified and quantified. The PCA showed that copper and lithium exposures result in statistically significant metabolite variations from the control. Contributing to this variation was a number of amino acids such as: phenylalanine, leucine, lysine, glutamine, glycine, alanine, methionine and glutamine as well as the nucleobase uracil and osmolyte glycerophosphocholine. The similarities in metabolome changes suggest that lithium has an analogous mode of toxicity to that of copper, and may be impairing energy production and ionoregulation. The PCA also showed that arsenic exposure resulted in a metabolic shift in comparison to the control population but this change was not statistically significant. However, significant changes in specific metabolites such as alanine and lysine were observed, suggesting that energy metabolism is indeed disrupted. This research demonstrates that (1)H NMR-based metabolomics is a viable platform for discerning metabolomic changes and mode of toxicity of D. magna in response to metal stressors in the environment.