Very few studies reported the potential of arbuscular mycorrhizal symbiosis to dissipate hydrocarbons in aged polluted soils. The present work aims to study the efficiency of arbuscular mycorrhizal colonized wheat plants in the dissipation of alkanes and polycyclic aromatic hydrocarbons (PAHs). Our results demonstrated that the inoculation of wheat with Rhizophagus irregularis allowed a better dissipation of PAHs and alkanes after 16 weeks of culture by comparison to non-inoculated condition. These dissipations observed in the inoculated soil resulted from several processes: (i) a light adsorption on roots (0.5% for PAHs), (ii) a bioaccumulation in roots (5.7% for PAHs and 6.6% for alkanes), (iii) a transfer in shoots (0.4 for PAHs and 0.5% for alkanes) and mainly a biodegradation. Whereas PAHs and alkanes degradation rates were respectively estimated to 12 and 47% with non-inoculated wheat, their degradation rates reached 18 and 48% with inoculated wheat. The mycorrhizal inoculation induced an increase of Gram-positive and Gram-negative bacteria by 56 and 37% compared to the non-inoculated wheat. Moreover, an increase of peroxidase activity was assessed in mycorrhizal roots. Taken together, our findings suggested that mycorrhization led to a better hydrocarbon biodegradation in the aged-contaminated soil thanks to a stimulation of telluric bacteria and hydrocarbon metabolization in mycorrhizal roots.

During the past two centuries metal loads in the Earth's atmosphere and ecosystems have increased significantly over pre-industrial levels. This has been associated with deleterious effects to ecosystem processes and human health. The magnitude of this toxic metal burden, as well as the spatial and temporal patterns of metal enrichment, is recorded in sedimentary archives across the globe. This paper presents a compilation of selected Pb contamination records from lakes (n = 10), peat mires (n = 10) and ice fields (n = 7) from Europe, North and South America, Asia, Australia and the Northern and Southern Hemisphere polar regions. These records quantify changes in Pb enrichment in remote from source environments. The presence of anthropogenic Pb in the environment has a long history, extending as far back as the early to mid-Holocene in North America, Europe and East Asia. However, results show that Pb contamination in the Earth's environment became globally ubiquitous at the beginning of the Second Industrial Revolution (c.1850–1890 CE), after which the magnitude of Pb contamination increased significantly. This date therefore serves as an effective global marker for the onset of the Anthropocene. Current global average Pb enrichment rates are between 6 and 35 times background, however Pb contamination loads are spatially variable. For example, they are >100 times background in Europe and North America and 5–15 times background in Antarctica. Despite a recent decline in Pb loads in some regions, most notably Europe and North America, anthropogenic Pb remains highly enriched and universally present in global ecosystems, while concentrations are increasing in some regions (Australia, Asia and parts of South America and Antarctica). There is, however, a paucity of Pb enrichment records outside of Europe, which limits assessments of global contamination.

Per- and polyfluoroalkyl substances (PFASs) were detected in the atmosphere of a source region in Tianjin, China. Fluorotelomer alcohols (FTOHs) were the dominant neutral PFASs in the atmosphere with total concentrations of 93.6-131 pg/m3 and 8:2 FTOH contributing the most, whereas perfluorooctane sulfonamide derivatives (PFOSAs) were two magnitudes lower or undetected. In comparison, ionic PFASs (perfluoroalkyl carboxyl acids (PFCAs)) in the atmosphere were detected at similar or even higher levels. At wastewater treatment plants (WWTPs), the air over influent was found with higher levels of FTOHs than over aeration tank and effluent; whereas in the air over the aeration tank, the concentrations of PFOSAs and nonvolatile ionic PFASs substantially increased, suggesting a possible direct release of ionic PFASs to the atmosphere besides the atmospheric conversion from volatile precursors. In the air phase, a low proportion (1-5%) of PFCAs was subjected to dry deposition in the source region. Interestingly, the dry-deposition-to-bulk-air ratios of PFCA analogues were the lowest at medium chain lengths (C8 and C9) and increased with either shorter or longer chain length. The extraordinary affinity of shorter-chain PFCAs (C6-C7) to particles was presumed to be due to their smaller molecular size favoring the interactions between the carboxyl head groups and specific sorption sites on particulate matter.

Exposure to trihalomethanes (THMs) and haloacetic acids (HAAs) has been individually associated with adverse male reproductive effects; however, their joint male reproductive toxicity is largely unknown. This study aimed to explore the joint effects of THMs and trichloroacetic acid (TCAA) on semen quality in a Chinese population. A total of 337 men presenting to the Reproductive Center of Tongjing Hospital, in Wuhan, China to seek semen analysis were included this study. Baseline blood THMs [chloroform (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and bromoform (TBM)] and urinary TCAA were analyzed and dichotomized at their median levels. The joint effects of THMs and TCAA on below-reference semen quality parameters were evaluated by calculating the relative excess risk due to interaction (RERI). After adjusting for potential confounders, we found a suggestive synergistic effect between Br-THMs (sum of BDCM, DBCM, and TBM) and TCAA for below-reference sperm count (RERI = 2.14, 95% CI: −0.37, 4.91) (P = 0.076); men with high Br-THMs and TCAA levels (above the median) had 3.31 times (95% CI: 1.21, 9.07) elevated risk of having below-reference sperm count than men with low Br-THMs and TCAA levels (below the median). No apparent joint effects were observed between THMs and TCAA for other semen quality parameters. Our results suggest that co-exposure to Br-THMs and TCAA is associated with additive effects on decreased semen quality. However, further studies in a larger sample size and mechanistic studies are needed to confirm the findings.

Classical laboratory-based single-species sediment bioassays do not account for modifications to toxicity from bioturbation by benthic organisms which may impact predictions of contaminated sediment risk to biota in the field. This study aims to determine the effects of bioturbation on the toxicity of zinc measured in a standard laboratory bioassay conducted with chironomid larvae (Chironomus tepperi). The epi-benthic chironomid larvae were exposed to two different levels of sediment contamination (1600 and 1980 mg/kg of dry weight zinc) in the presence or absence of annelid worms (Lumbriculus variegatus) which are known to be tolerant to metal and to have a large impact on sediment properties through bioturbation.Chironomids had 5–6x higher survival in the presence of L. variegatus which shows that bioturbation had a beneficial effect on the chironomid larvae. Chemical analyses showed that bioturbation induced a flux of zinc from the pore water into the water column, thereby reducing the bioavailability of zinc in pore water to the chironomid larvae. This also suggested that pore water was the major exposure path for the chironomids to metals in sediment. During the study, annelid worms (Oligochaetes) produced a thin layer of faecal pellets at the sediment surface, a process known to: (i) create additional adsorption sites for zinc, thus reducing its availability, (ii) increase the microbial abundance that in turn could represent an additional food source for opportunistic C. tepperi larvae, and (iii) modify the microbial community’s structure and alter the biogeochemical processes it governs thus indirectly impact zinc toxicity.This study represents a contribution in recognising bioturbating organisms as “ecological engineers” as they directly and indirectly influence metal bioavailability and impact other sediment-inhabiting species. This is significant and should be considered in risk assessment of zinc levels (and other metals) in contaminated sediment when extrapolating from laboratory studies to the field.

Methane emissions in oil sands tailings ponds are sustained by anaerobic biodegradation of unrecovered hydrocarbons. Naphtha (primarily C6–C10; n- iso- and cycloalkanes) is commonly used as a solvent during bitumen extraction process and its residue escapes to tailings ponds during tailings deposition. To investigate biodegradability of hydrocarbons in naphtha, mature fine tailings (MFT) collected from Albian and CNRL tailings ponds were amended with CNRL naphtha at ∼0.2 wt% (∼2000 mg L−1) and incubated under methanogenic conditions for ∼1600 d. Microbial communities in both MFTs started metabolizing naphtha after a lag phase of ∼100 d. Complete biodegradation/biotransformation of all n-alkanes (except partial biodegradation of n-octane in CNRL MFT) followed by major iso-alkanes (2-methylpentane, 3-methylhexane, 2- and 4-methylheptane, iso-nonanes and 2-methylnonane) and a few cycloalkanes (derivatives of cyclopentane and cyclohexane) was observed during the incubation. 16S rRNA gene pyrosequencing showed dominance of Peptococcaceae and Anaerolineaceae in Albian MFT and Anaerolineaceae and Syntrophaceae in CNRL MFT bacterial communities with co-domination of Methanosaetaceae and “Candidatus Methanoregula” in archaeal populations during active biodegradation of hydrocarbons. The findings extend the known range of hydrocarbons susceptible to methanogenic biodegradation in petroleum-impacted anaerobic environments and help refine existing kinetic model to predict greenhouse gas emissions from tailings ponds.

We compared temporal trends of total mercury (Hg) in eggs of five seabird species breeding at Prince Leopold Island in the Canadian high Arctic. As changes in trophic position over time have the potential to influence contaminant temporal trends, Hg concentrations were adjusted for trophic position (measured as δ15N). Adjusted Hg concentrations in eggs of thick-billed murres (Uria lomvia) and northern fulmars (Fulmarus glacialis) increased from 1975 to the 1990s, followed by a plateauing of levels from the 1990s to 2014. Trends of adjusted Hg concentrations in eggs of murres, fulmars, black guillemots (Cepphus grylle) and black-legged kittiwakes (Rissa tridactyla) had negative slopes between 1993 and 2013. Adjusted Hg concentrations in glaucous gull (Larus hyperboreus) eggs decreased by 50% from 1993 to 2003 before starting to increase again. Glaucous gull eggs had the highest Hg concentrations followed by black guillemot eggs, and black-legged kittiwake eggs had the lowest concentrations consistently in the five years compared between 1993 and 2013. Based on published toxicological thresholds for Hg in eggs, there is little concern for adverse reproductive effects due to Hg exposure in these birds, although the levels in glaucous gull eggs warrant future scrutiny given the increase in Hg concentrations observed in recent years. There is evidence that the Hg trends observed reflect changing anthropogenic Hg emissions. It remains unclear, however, to what extent exposure to Hg on the overwintering grounds influences the Hg trends observed in the seabird eggs at Prince Leopold Island. Future research should focus on determining the extent to which Hg exposure on the breeding grounds versus the overwintering areas contribute to the trends observed in the eggs.

Environmental pollution by both ambient CO2 and heavy metals has been steadily increasing, but we do not know how fluctuating CO2 concentrations influence plant nutrients under high Cd pollution, especially in crops. Here, we studied the effects of elevated CO2 and Cd accumulation on proteins and amino acids in rice under Cd stress. In this pot experiment, we analyzed the amino-acid profile of 20 rice cultivars that accumulate Cd differently; the plants were grown in Cd-containing soils under ambient conditions and elevated CO2 levels. We found that although Cd concentrations appeared to be higher in most cultivars under elevated CO2 than under ambient CO2, the effect was significant only in seven cultivars. Combined exposure to Cd and elevated CO2 strongly decreased rice protein and amino acid profiles, including essential and non-essential amino acids. Under elevated CO2, the ratios of specific amino acids were either higher or lower than the optimal ratios provided by FAO/WHO, suggesting that CO2 may flatten the overall amino-acid profile, leading to an excess in some amino acids and deficiencies in others when the rice is consumed. Thus, Cd-tainted rice limits the concentration of essential amino acids in rice-based diets, and the combination with elevated CO2 further exacerbates the problem.

The resuspension of polluted sediments by boat traffic could release substantial amounts of metals to the water column, affecting at the same time their bioavailability. In order to characterize the impact of sediment resuspensions on biota, caged amphipods have been deployed on three different channelized watercourses in Northern France. Firstly, the biological responses of transplanted freshwater gammarid amphipods, Gammarus fossarum, described by trace metal accumulation, feeding and reproduction activities were quite similar for the three water courses despite the differences of metal contamination and navigability. Secondly, the concentrations of metals accumulated in gammarids never exceeded the contamination thresholds previously defined for Co, Cu, Cr and Zn. Values were in the same order of magnitude whatever the studied site despite: (i) large differences noticed in the sediment quality and (ii) some concentrations in the overlying waters exceeding the Environmental Quality Standards (EQS) defined by the Water Framework Directive. Conversely, Pb was highly bioaccumulated with values systematically exceeding the threshold value whatever the site. Therefore, the impact of navigation cannot be proved and the difference between the 3 monitoring periods is rather attributed to environmental variability, probably linked to the seasonality. Moreover, this study also confirms that organisms sampled from a local population in the vicinity of the three studied watercourses could be used as test organisms, leading to similar results than the ones obtained with reference gammarids initially used for developing all the biological responses. This would simplify and then promote the development of studies based on gammarid amphipod, G. fossarum, as bioindicators.

Diesel combustion and solid biomass burning are the major sources of ultrafine particles (UFP) in urbanized areas. Cardiovascular and pulmonary diseases, including lung cancer, are possible outcomes of combustion particles exposure, but differences in particles properties seem to influence their biological effects.Here the physico-chemical properties and biological effects of diesel and biomass particles, produced under controlled laboratory conditions, have been characterized. Diesel UFP were sampled from a Euro 4 light duty vehicle without DPF fuelled by commercial diesel and run over a chassis dyno. Biomass UFP were collected from a modern automatic 25 kW boiler propelled by prime quality spruce pellet. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images of both diesel and biomass samples showed aggregates of soot particles, but in biomass samples ash particles were also present. Chemical characterization showed that metals and PAHs total content was higher in diesel samples compared to biomass ones.Human bronchial epithelial (HBEC3) cells were exposed to particles for up to 2 weeks. Changes in the expression of genes involved in xenobiotic metabolism were observed after exposure to both UFP already after 24 h. However, only diesel particles modulated the expression of genes involved in inflammation, oxidative stress and epithelial-to-mesenchymal transition (EMT), increased the release of inflammatory mediators and caused phenotypical alterations, mostly after two weeks of exposure.These results show that diesel UFP affected cellular processes involved in lung and cardiovascular diseases and cancer. Biomass particles exerted low biological activity compared to diesel UFP. This evidence emphasizes that the study of different emission sources contribution to ambient PM toxicity may have a fundamental role in the development of more effective strategies for air quality improvement.