While considerable attention has been given to the measurement of mercury (Hg) and lead (Pb) concentrations and accumulation in detailed peat cores in central Canada, the geographic distribution and density of sampling are generally limited. Here, we use the Ontario Peatland Inventory to examine broad patterns of Hg and Pb concentration with depth, based on 338 peat cores (containing >1500 analyzed samples) from 127 bogs, fens and swamps located in southeastern, northeastern and northwestern sections of Ontario. Overall, Hg concentrations averaged 0.05 μg g⁻¹ and that of Pb averaged 10.8 μg g⁻¹. Maximum values in the top 50 cm of the profiles are 0.08 μg g⁻¹ and 26.2 μg g⁻¹ for Hg and Pb, respectively. The ratio between these values (surface) and the values from below 100 cm (background), where peat likely accumulated before 1850 and industrial activities were limited, are 2.3 and 6.6 for Hg and Pb, respectively. The highest surface:background concentration ratios are generally found in the westernmost part of the province and in the southeast for Hg and around areas that are more heavily populated for Pb. Our results show that a vast amount of Hg and Pb are stored in Ontarian peatlands, although the spatial distribution of these stores varies. The rapid decomposition of peat in a changing climate could release these pollutants to the atmosphere.

Toxicity and uptake of nano-CeO2 (nCeO2) in edible vegetables are not yet fully understood. In the present study, we grew romaine lettuce in sand amended with nCeO2. At high concentrations (1000 and 2000 mg/kg), nCeO2 diminished the chlorophyll content by 16.5% and 25.8%, respectively, and significantly inhibited the biomass production. nCeO2 (≥100 mg/kg) altered antioxidant enzymatic activities and malondialdehyde levels in the plants. nCeO2 (≥500 mg/kg) triggered a remarkable increase of nitrate-N level in the shoots, which can be converted to toxic nitrite in humans thereby posed risk to human health. Concentration dependent accumulation of Ce in the plant tissues was observed. X ray absorption near edge spectroscopy (XANES) results indicate that Ce presented as nCeO2 and CePO4 in the roots while as nCeO2 and Ce carboxylates in the shoots. Chelation of Ce3+ by citric acid or precipitation of Ce3+ by PO43− reduced the translocation and toxicity of nCeO2, indicating that release of Ce3+ played a critical role in the toxicity nCeO2.

Arsenic is a widespread metalloid in the environment, which poses a broad spectrum of adverse effects on human health. However, a global view of arsenic-induced heart toxicity is still lacking, and the underlying molecular mechanisms remain unclear. By performing a comparative quantitative proteomic analysis, the present study aims to investigate the alterations of proteome profile in rat heart after long-term exposure to arsenic. As a result, we found that the abundance of 81 proteins were significantly altered by arsenic treatment (35 up-regulated and 46 down-regulated). Among these, 33 proteins were specifically associated with cardiovascular system development and function, including heart development, heart morphology, cardiac contraction and dilation, and other cardiovascular functions. It is further proposed that the aberrant regulation of 14 proteins induced by arsenic would disturb cardiac contraction and relaxation, impair heart morphogenesis and development, and induce thrombosis in rats, which is mediated by the Akt/p38 MAPK signaling pathway. Overall, these findings will augment our knowledge of the involved mechanisms and develop useful biomarkers for cardiotoxicity induced by environmental arsenic exposure.

Understanding the phytoavailability of bound residues of polycyclic aromatic hydrocarbons (PAHs) in soils is essential to assessing their environmental fate and risks. This study investigated the release and plant uptake of bound PAH residues (reference to parent compounds) in field contaminated soils after the removal of extractable PAH fractions. Plant pot experiments were performed in a greenhouse using ryegrass (Lolium multiflorum Lam.) to examine the phytoavailablility of bound PAH residues, and microcosm incubation experiments with and without the addition of artificial root exudates (AREs) or oxalic acid were conducted to examine the effect of root exudates on the release of bound PAH residues. PAH accumulation in the ryegrass after a 50-day growth period indicated that bound PAH residues were significantly phytoavailable. The extractable fractions, including the desorbing and non-desorbing fractions, dominated the total PAH concentrations in vegetated soils after 50 days, indicating the transfer of bound PAH residues to the extractable fractions. This transfer was facilitated by root exudates. The addition of AREs and oxalic acid to test soils enhanced the release of bound PAH residues into their extractable fractions, resulting in enhanced phytoavailability of bound PAH residues in soils. This study provided important information regarding environmental fate and risks of bound PAH residues in soils.

The Biocoenosis of Well Sorted Fine Sands (WSFS) (SFBC, Sables Fins Bien Calibrés in French) is a Mediterranean community very well delimited by bathymetry (2–25 m) and sedimentology (>90% of fine sand) occurring in zones with relatively strong hydrodynamics. In this study focused on sites located along the Algerian, French, Italian and Spanish coasts of the Western Basin of the Mediterranean Sea (WBMS) we aim to compare the structure, ecological status and diversity of the macrofauna of the WSFS and examine the effects of recent human pressures on the state of this shallow macrobenthic community. We assess the ecological status and functioning of these WSFS using three categories of benthic indices: a) five indices based on classification of species into ecological groups, AMBI, BO2A, BPOFA, IQ and IP, b) the ITI index based on classification of species in trophic groups, and c) the Shannon H’ index, and the Biological Traits Analysis (BTA), which is an alternative method to relative taxon composition analysis and integrative indices. Cluster analyses show that each zone show a particular taxonomic richness and dominant species. The seven benthic indices reveal that the macrobenthos of the WSFS of the four coastal zones show good or high Quality Status, except for one location on the Algerian coast (the Djendjen site) in 1997. BTA highlights the presence of three groups of species: 1) typical characteristic species; 2) indicator species of enrichment of fine particles and organic matter, and 3) coarse sand species which are accessorily found on fine sand. Finally, the WSFS which are naturally subject to regular natural physical perturbations show a high resilience after human pressures but are very sensitive to changes in the input of organic matter.

There are limited ambient air measurements of extended (beyond EPA Priority 16) lists of polycyclic aromatic hydrocarbons (PAHs). We measured air concentrations of 45 PAHs using passive and active air sampling at 15 sites in a central urban community and one rural site for two years. Passive sampling was conducted with cylindrical XAD-based samplers deployed to capture spatial variability. High volume active samplers with quartz fiber filters for particles and XAD-4 absorbent for gases were deployed at two urban sites and the rural site to calibrate the passive measurements directly. Estimated passive sampling rates (PSRs) were evaluated as functions of meteorological data, seasons, locations, study year, and compared with other studies. Possible particle collection by the passive samplers was evaluated using a variety of particle measurements (TSP, PM10, PM2.5 and ultrafines <100 nm). Total PAHs were statistically associated with ultrafine particle concentrations and to a lesser extent PM2.5 and PM10, but not TSP. PSRs were more variable when PAH mass loadings were lower and near method detection limits; this occurred more often at the rural site. The PSRs were not statistically associated with meteorological conditions in this study, but wind speed had the highest potential to impact PSR results. The resulting passive PAH measurements are reported with respect to proximity to major roadways and other known air emissions types. PSRs were quantifiable for some PAHs that were found predominantly in the particulate phase in active sampling. This information, together with particle fraction calculations from active sampling, were used to estimate the particulate PAH capture of the passive sampler. Summed PAH (∑PAH) passive concentrations were measured within the range of 10–265 ng/m3, with the highest concentrations from naphthalene and the lowest detected concentrations from anthracene. These results indicated a stronger seasonal signal within 200 m of a major roadway.

Metal detoxification in plants is a complex process that involves different mechanisms, such as the retention of metals to the cell wall and their chelation and subsequent compartmentalization in plant vacuoles. In order to identify the mechanisms involved in metal accumulation and tolerance in Betula pubescens, as well as the role of mycorrhization in these processes, mycorrhizal and non-mycorrhizal plants were grown in two industrial soils with contrasting concentrations of heavy metals.Mycorrhization increased metal uptake at low metal concentrations in the soil and reduced it at high metal concentrations, which led to an enhanced growth and biomass production of the host when growing in the most polluted soil. Our results suggest that the sequestration on the cell wall is the main detoxification mechanism in white birch exposed to acute chronic metal-stress, while phytochelatins play a role mitigating metal toxicity inside the cells. Given its high Mn and Zn root-to-shoot translocation rate, Betula pubescens is a very promising species for the phytoremediation of soils polluted with these metals.

Natural attenuation of organic contaminants in groundwater can give rise to a series of complex biogeochemical reactions that release secondary contaminants to groundwater. In a crude oil contaminated aquifer, biodegradation of petroleum hydrocarbons is coupled with the reduction of ferric iron (Fe(III)) hydroxides in aquifer sediments. As a result, naturally occurring arsenic (As) adsorbed to Fe(III) hydroxides in the aquifer sediment is mobilized from sediment into groundwater. However, Fe(III) in sediment of other zones of the aquifer has the capacity to attenuate dissolved As via resorption. In order to better evaluate how long-term biodegradation coupled with Fe-reduction and As mobilization can redistribute As mass in contaminated aquifer, we quantified mass partitioning of Fe and As in the aquifer based on field observation data. Results show that Fe and As are spatially correlated in both groundwater and aquifer sediments. Mass partitioning calculations demonstrate that 99.9% of Fe and 99.5% of As are associated with aquifer sediment. The sediments act as both sources and sinks for As, depending on the redox conditions in the aquifer. Calculations reveal that at least 78% of the original As in sediment near the oil has been mobilized into groundwater over the 35-year lifespan of the plume. However, the calculations also show that only a small percentage of As (∼0.5%) remains in groundwater, due to resorption onto sediment. At the leading edge of the plume, where groundwater is suboxic, sediments sequester Fe and As, causing As to accumulate to concentrations 5.6 times greater than background concentrations. Current As sinks can serve as future sources of As as the plume evolves over time. The mass balance approach used in this study can be applied to As cycling in other aquifers where groundwater As results from biodegradation of an organic carbon point source coupled with Fe reduction.

Over 700 million people in Sub-Saharan Africa depend on solid biomass fuel and use simple cookstoves in poorly ventilated kitchens, which results in high indoor concentrations of household air pollutants. Switching from biomass to biogas as a cooking fuel can reduce airborne emissions of fine particulate matter (PM2.5) and carbon monoxide (CO), but households often only partially convert to biogas, continuing to use solid biomass fuels for part of their daily cooking needs. There is little evidence of the benefits of partial switching to biogas. This study monitored real-time PM2.5 and CO concentrations in 35 households in Cameroon and Uganda where biogas and firewood (or charcoal) were used. The 24 h mean PM2.5 concentrations in households that used: (1) firewood and charcoal; (2) both firewood (mean 54% cooking time) and biogas (mean 46% cooking time); and (3) only biogas, were 449 μg m⁻³, 173 μg m⁻³ and 18 μg m⁻³ respectively. The corresponding 24 h mean CO concentrations were 14.2 ppm, 2.7 ppm and 0.5 ppm. Concentrations of both PM2.5 and CO were high and exceeded the World Health Organisation guidelines when firewood and charcoal were used. Partially switching to biogas reduced CO exposure to below the World Health Organisation guidelines, but PM2.5 concentrations were only below the 24 h recommended limits when households fully converted to biogas fuel. These results indicate that partial switching from solid fuels to biogas is not sufficient and continues to produce concentrations of household air pollution that are likely to harm the health of those exposed. Programmes introducing biogas should aim to ensure that household energy needs can be fully achieved using biogas with no requirement to continue using solid fuels.

Pharmaceutical and personal care products (PPCPs) are continuously introduced into the soil-plant system, through practices such as agronomic use of reclaimed water and biosolids containing these trace contaminants. Plants may accumulate PPCPs from soil, serving as a conduit for human exposure. Metabolism likely controls the final accumulation of PPCPs in plants, but is in general poorly understood for emerging contaminants. In this study, we used diclofenac as a model compound, and employed 14C tracing, and time-of-flight (TOF) and triple quadruple (QqQ) mass spectrometers to unravel its metabolism pathways in Arabidopsis thaliana cells. We further validated the primary metabolites in Arabidopsis seedlings. Diclofenac was quickly taken up into A. thaliana cells. Phase I metabolism involved hydroxylation and successive oxidation and cyclization reactions. However, Phase I metabolites did not accumulate appreciably; they were instead rapidly conjugated with sulfate, glucose, and glutamic acid through Phase II metabolism. In particular, diclofenac parent was directly conjugated with glutamic acid, with acyl-glutamatyl-diclofenac accounting for >70% of the extractable metabolites after 120-h incubation. In addition, at the end of incubation, >40% of the spiked diclofenac was in the non-extractable form, suggesting extensive sequestration into cell matter. The rapid formation of non-extractable residue and dominance of diclofenac-glutamate conjugate uncover previously unknown metabolism pathways for diclofenac. In particular, the rapid conjugation of parent highlights the need to consider conjugates of emerging contaminants in higher plants, and their biological activity and human health implications.