Paleo-environmental record of polycyclic aromatic hydrocarbons and polychlorobiphenyls at the peripheral site GV7 in Victoria Land (East Antarctica)

Pollution characteristics, distribution, and source analysis of carbazole and polyhalogenated carbazoles in coastal areas of Bohai Bay, China

Polyhalogenated carbazoles (PHCZs) are a class of emerging environmental contaminants formed by the substitution of hydrogen on carbazole (CZ) benzene rings with halogens (Cl, Br, I) with potential dioxin-like toxicity, and they have been frequently detected in various environmental media and organisms recently. Nevertheless, co-research of CZ/PHCZs with PAHs is very limited. In addition, I-PHCZs, which are believed to be much more toxic than CZ, Cl-PHCZs and Br-PHCZs, have a few data in sediments previously. The concentration and distribution of CZ/PHCZs and PAHs were analyzed in 18 surface sediments of Bohai Bay, China. There is a significant correlation (R = 0.64, P＜0.05) between PHCZs and PAHs, and principal component analysis (PCA) also indicating that they may have a certain similarity in origin. Additionally, total CZ and PHCZs was up to 230.57 ng/g dw in the studied samples, which was approximately 1-2 orders of magnitude lower than PAHs and other common persistent organic pollutants (POPs). The compositions of the CZ/PHCZs in our study were dominated by CZ (2.74-18.28, median 2.92 ng/g dw), 3,6-dichlorocarbazole (n.d-6.78, median 0.97 ng/g dw) and 3,6-iodocarbazole (n.d-12.68, median 1.65 ng/g dw). Results of this study discovered the varying origins of CZ and PHCZs and/or a complexity of anthropogenic influences and natural sources processes, and revealed a wide distribution of CZ/PHCZs across the studied. Moreover, more attention should be paid by comparing CZ/PHCZs with other widely distributed POPs.

POPs in Antarctic ecosystems: is climate change affecting their temporal trends?

Climate change is affecting Antarctica and the Southern Ocean and effects have been already reported for the abiotic compartments of the ecosystems, e.g. ice loss and iceberg calving. Global warming can alter also the distribution of persistent organic pollutant (POPs) both at a global scale and in the Antarctic Region, due to their physical-chemical characteristics. Effects of climate changes have been already reported on feeding behaviour and reproductive process of organisms. Another consequence for organisms includes the POP bioaccumulation. Here we review the literature reporting the linkage between recorded effects of climate changes and POP bioaccumulation in resident marine Antarctic species (fish and penguins). Notwithstanding Antarctica is a final sink for persistent contaminants due to the extreme cold climate, a general decreasing POP trend has been observed for some POPs. Their concentrations in biota are reported to be linked to ice melting and large iceberg calving; the peculiar marine Antarctic ecosystems and the pelagic-benthic coupling may also contribute to alterations in the bioaccumulation processes. These effects are similar in polar regions, although the comparison with the Arctic biota is not possible due to the lack of data in the Antarctic Region. It remains an open question if the POP amount accumulated in the Antarctic ecosystems is decreasing or not.

Legacy and emerging organic contaminants in the polar regions

The presence of numerous emerging organic contaminants (EOCs) and remobilization of legacy persistent organic pollutants (POPs) in polar regions have become significant concerns of the scientific communities, public groups and stakeholders. This work reviews the occurrences of EOCs and POPs and their long-range environmental transport (LRET) processes via atmosphere and ocean currents from continental sources to polar regions. Concentrations of classic POPs have been systematically monitored in air at several Arctic stations and showed seasonal variations and declining trends. These chemicals were also the major POPs reported in the Antarctica, while their concentrations were lower than those in the Arctic, illustrating the combination of remoteness and lack of potential local sources for the Antarctica. EOCs were investigated in air, water, snow, ice and organisms in the Arctic. Data in the Antarctica are rare. Reemission of legacy POPs and EOCs accumulated in glaciers, sea ice and snow may alter the concentrations and amplify their effects in polar regions. Thus, future research will need to understand the various biogeochemical and geophysical processes under climate change and anthropogenic pressures.

Behavioral and hypothalamic transcriptome analyses reveal sex-specific responses to phenanthrene exposure in the fathead minnow (Pimephales promelas)

Environmental concentrations of the polycyclic aromatic hydrocarbon phenanthrene can become elevated with petroleum processing, industrial activities, and urban run-off into waterbodies. However, mechanisms related to its neurotoxicity in fish are not fully described. Here, we exposed adult fathead minnows (FHM) to an average measured concentration of 202 μg phenanthrene/L over a 47-d period. Behaviors of male and female FHM were assessed using a novel aquarium test. Phenanthrene exposed females displayed equilibrium loss, while phenanthrene exposed males spent less time in the aquarium bottom, suggesting phenanthrene reduced anxiety-related behavior. To elucidate putative mechanisms underlying behaviors, we determined the hypothalamic transcriptome profile, a critical integration centre for the regulation of behaviors. There were 1075 hypothalamic transcripts differentially expressed between males and females (sex-specific) while 15 transcripts were phenanthrene-specific. Thus, sex of the animal was more pervasive at influencing the transcriptome compared to phenanthrene and this may partially explain the divergent behavioral responses between sexes. Transcripts altered by phenanthrene included palmitoylated 3 membrane protein, plectin 1,ATP synthase membrane subunit c, and mitochondrial ribosomal protein S11. Gene set enrichment analysis revealed less than 5% of the gene networks perturbed by phenanthrene were shared between males and females, thus phenanthrene altered the hypothalamic transcriptome in a sex-specific manner. Gene networks shared between both sexes and associated with phenanthrene-induced neurotoxicity included processes related to mitochondrial respiratory chain dysfunction, epinephrine/norepinephrine release, and glutamate biosynthesis pathways. Such energy deficits and neurotransmitter disruptions are hypothesized to lead to behavioral deficits in fish. This study provides mechanistic insights into phenanthrene-induced neurotoxicity and how it may relate to changes in fish behaviors.

A sensitive microextraction by packed sorbent-gas chromatography-mass spectrometry method for the assessment of polycyclic aromatic hydrocarbons contamination in Antarctic surface snow

For the first time an eco-friendly method involving microextraction by packed sorbent (MEPS) coupled to gas chromatography-mass spectrometry (GC-MS) was developed for the determination of the 16 US-EPA priority pollutant polycyclic aromatic hydrocarbons (PAHs) as indicators of anthropogenic contamination in snow samples collected in polar regions. MEPS was carried out by using C8 sorbent material packed in a barrel insert and needle (BIN) and integrated in the eVol® semi-automatic device. For optimization purposes a Face Centred Design and the multicriteria method of the desirability functions were performed to investigate the effect of some parameters affecting the MEPS extraction efficiency, i.e. the number of loading cycles and the number of elution cycles. The developed MEPS-GC-MS method proved to be suitable for PAHs analysis at ultra-trace level by extracting small sample volumes achieving detection limits for 16 PAHs in the 0.3-5 ng L^-1 range, repeatability and intermediate precision below 11% and 15%, respectively, and good recovery rates in the 77.6 (±0.1)-120.8 (±0.1)% range for spiked blank snow samples. Enrichment factors in the 64 (±7)-129 (±18) range were calculated. Finally, the proposed method was successfully applied to the determination of PAHs in surface snow samples collected in 2020-2021 from four locations of Northern Victoria Land, Antarctica. Local emission sources such as ships and research stations were found to influence PAHs concentrations in the surface snow.

Helical multi-walled carbon nanotube-coated fibers for solid-phase microextraction determination of polycyclic aromatic hydrocarbons at ultra-trace levels in ice and snow samples

Polycyclic Aromatic Hydrocarbons (PAHs) detected in polar environment are recognized tracers of anthropogenic pollution. High sensitivity and selectivity are required for their analysis in ice and snow samples due to the presence at ultra-trace levels. In this study a solid-phase microextraction (SPME) gas chromatography-mass spectrometry (GC-MS) method for simultaneous determination of the 16 US-EPA priority pollutant PAHs in polar snow and ice samples was developed and validated. Helical multiwalled carbon nanotubes (HMWCNTs) were proposed for the first time as novel SPME coating. For optimization purposes a Central Composite Design and the multicriteria method of the desirability functions were applied to investigate the influence of extraction parameters, i.e. time and temperature as main factors. The optimal values were 68 °C for the extraction temperature and 60 min for the extraction time. The developed SPME-GC-MS method exhibited detection limits of 16 PAHs in the 0.1-1.2 ng/L range, a repeatability and an intermediate precision within 15% and 22% relative standard deviation, respectively, and good recovery rates in the 93.7 (± 0.1)-119.7 (± 0.2)% range for real spiked water sample, showing better analytical performance compared to commercial PDMS fibers. Enrichment factors in the 2670 (± 290)-142120 (± 580) range were calculated and a long fiber shelf-life with the possibility to reuse the fiber more than 200 times was achieved. Finally, the proposed method was successfully applied to the determination of PAHs in surface snow samples collected in April 2019 at Ny-Ålesund, Svalbard. Its application to the detection of PAHs in samples collected during monitoring campaigns in the polar regions is expected in the near future.

The Great Acceleration of fragrances and PAHs archived in an ice core from Elbrus, Caucasus

The Great Acceleration of the anthropogenic impact on the Earth system is marked by the ubiquitous distribution of anthropogenic materials throughout the global environment, including technofossils, radionuclides and the exponential increases of methane and carbon dioxide concentrations. However, personal care products as direct tracers of human domestic habits are often overlooked. Here, we present the first research combining fragrances, as novel personal care products, and polycyclic aromatic hydrocarbons (PAHs) as combustion and industrial markers, across the onset of the Great Acceleration in the Elbrus, Caucasus, ice core. This archive extends from the 1930s to 2005, spanning the profound changes in the relationship between humans and the environment during the twentieth century. Concentrations of both fragrances and PAHs rose throughout the considered period, reflecting the development of the Anthropocene. However, within this rising trend, remarkable decreases of the tracers track the major socioeconomic crises that occurred in Eastern Europe during the second half of the twentieth century.

PBDEs and PCBs in terrestrial ecosystems of the Victoria Land, Antarctica

The Victoria Land (East Antarctica) is characterized by the presence of lakes and ponds where rare water is found during the Summer months. These freshwater ecosystems are an important resource for migrating seabirds that use them and leave there their droppings and feathers, contributing to enrich the water with organic matter. Persistent organic pollutants (POPs) are long-range transported to polar regions and their detection in the Antarctic ecosystems date back to the 1960s. Most studies have been related to POP concentrations in marine environment, and terrestrial ecosystems have been poorly investigated. This study reports the concentration of PBDEs (23 congeners) and PCBs (21 among non-, mono-, di-, and ortho congeners) in lake sediment, soil and vegetation mat (community of algae, cyanobacteria, bryophites) collected close to six lakes in the Victoria Land (74°31'S-74°97'S, 165°07'E-162°51'E): Edmonson Point 14 and 15A, Carezza, Enigma, Tarn Flat 20, Inexpressible Island 10B. The ∑PBDEs averaged 0.09-0.28 ng/g and BDEs 28, 47 and 154 were higher in mat and soils, while BDEs 183 and 47 in sediment samples. PCBs ranged <0.003-0.807 ng/g and congeners nos. 114, 138, and 187 were the most abundant. In addition, TEQs were derived for the non-and mono-ortho PCBs detected and values were very low in each matrix (0.010 pg/g in the soil, 0.012 pg/g in sediment and mat). The long-range atmospheric transport can be confirmed as the most important POP source in Antarctica, although the scientific stations and seabird colonies may be potential local sources and contribute to contaminant release.

Part B: Morphometric and transcriptomic responses to sub-chronic exposure to the polycyclic aromatic hydrocarbon phenanthrene in the fathead minnow (Pimephales promelas)

Phenanthrene is a tricyclic polycyclic aromatic hydrocarbon and environmental contaminant found in high concentrations around urban catchments and in the vicinity of oil extraction activities. Fish exposed to phenanthrene can exhibit altered reproductive hormone profiles and/or differences within gonadosomatic index and altered gamete proportions, but the mechanisms underlying these changes are not fully understood. In this study, we conducted a sub-chronic bioassay and measured transcriptional responses in the liver, the major tissue involved in generating lipids for oocyte growth. Adult male and female fathead minnow (Pimephales promelas) were exposed to an average measured concentration of 202 μg phenanthrene/L for a 7 week period. Condition factor was reduced in both males and females, while female fish also showed decreased gonadosomatic index relative to control females. In females exposed to phenanthrene, perinucleolar proportions were increased ∼1.9-fold relative to the control group whereas the proportions of vitellogenic oocytes decreased ∼8.8 fold. In males exposed to phenanthrene, spermatogonia proportions were increased ∼2.3 fold in testicular tissues compared to control fish. Thus, gametes were at an earlier stage of maturation in phenanthrene-treated fish compared to controls. However, no differences were detected in the production of 17β-estradiol or testosterone from the gonad in either sex. Catalase activity was also assessed in the liver as a measure of oxidative stress and this biomarker did not change in activity in either sex. In addition to endpoints in the ovary, the female hepatic transcriptome was measured, as this tissue produces lipids for oocyte maturation. Transcriptomic responses to phenanthrene exposure suggested a reduction in vitellogenin mRNA, and lipid metabolism and immune system pathways. Comparisons of hepatic transcriptome responses with Part A (72 h phenanthrene exposure) showed that energy homeostasis pathways were consistently altered following phenanthrene exposure over multiple durations and concentrations. We suggest that altered energy homeostasis may be adversely affecting reproductive efforts, as impaired reproduction has been observed in other studies investigating polycyclic aromatic hydrocarbons.

Part A: Temporal and dose-dependent transcriptional responses in the liver of fathead minnows following short term exposure to the polycyclic aromatic hydrocarbon phenanthrene

Phenanthrene is a low molecular weight polycyclic aromatic hydrocarbon (PAH) that is composed of three fused benzene rings. PAHs are formed naturally through incomplete combustion of organic materials, and are environmental contaminants due to anthropogenic activities (e.g. oil extraction and refining, industrial and municipal effluents, fossil fuel burning). Fish exposed to PAHs such as phenanthrene have been reported to exhibit altered reproductive axis endpoints, however the mechanisms that underlie these responses are not fully characterized. To better understand effects at the mechanistic level, we applied transcriptomics to identify molecular pathways altered after acute exposure to phenanthrene on both a dose and temporal scale. Female fathead minnow (Pimephales promelas) were exposed to an average measured concentration of either 0, 29.8, 389 or 943 μg phenanthrene/L for 24, 48, and 72 h in a static-renewal bioassay. Ovaries were assessed for oocyte distribution as well as in vitro 17β-estradiol production and gene expression for transcripts related to steroidogenesis and estrogen signalling. In addition, the liver transcriptome was measured as this tissue is the primary source of the egg yolk precursor protein vitellogenin. Exposure to 29.8 μg phenanthrene/L increased proportions of the cortical alveolar stage in the ovaries after 48 h while the proportion of cortical alveolar oocyte were decreased in fish exposed to 943 μg phenanthrene/L for 48 h. Phenanthrene did not affect 17β-estradiol production at any time or dose, and did not affect transcripts associated with hormone synthesis nor signalling pathways. In the liver, the transcriptome showed fewer genes in common across time when compared to those transcripts affected by concentration at a single time point. Cholesterol metabolism was the only pathway perturbed in the liver following all comparisons in both the dose and time course experiments. Our data suggest that transcriptome networks associated with hepatic lipid metabolism are rapidly affected by phenanthrene, and this may indirectly reduce resources available for reproductive efforts.