We examined the historical deposition of polycyclic aromatic compounds (PACs) recorded in radiometrically-dated lake sediment cores from a small, conventional oil and gas operation in the southern Northwest Territories (Cameron Hills), and placed these results in the context of previously published work from three other important regions of western Canada: (1) the Athabasca oil sands region in Alberta; (2) Cold Lake, Alberta; and (3) the Mackenzie Delta, NT. Sediment PAC records from the Cameron Hills showed no clear changes in either source or concentrations coincident with the timing of development in these regions. Changes were small in comparison to the clear increases in both parent and alkyl-substituted PACs in response to industrial development from the Athabasca region surface mining of oil sands, where parent PAC diagnostic ratios indicated a shift from pyrogenic sources (primarily wood and coal burning) in pre-development sediments to more petrogenically-sourced PACs in modern sediments. Cores near in-situ oil sand extraction operations showed only modest increases in PAC deposition. This work directly compares the history and trajectory of contamination in lake ecosystems in areas of western Canada impacted by the most common types of hydrocarbon extraction activities, and provides a context for assessing the environmental impacts of oil and gas development in the future.

Organisms around the globe are experiencing novel environments created by human activities. One such disturbance of growing concern is the salinization of freshwater habitats from the application of road deicing salts, which creates salinity levels not experienced within the recent evolutionary history of most freshwater organisms. Moreover, salinization can induce trophic cascades and alter the structure of freshwater communities, but knowledge is still scarce about the ability of freshwater organisms to adapt to elevated salinity. We examined if a common zooplankton of freshwater lakes (Daphnia pulex) could evolve a tolerance to the most commonly used road deicing salt (sodium chloride, NaCl). Using a mesocosm experiment, we exposed freshwater communities containing Daphnia to five levels of NaCl (15, 100, 200, 500, and 1000 mg Cl− L−1). After 2.5 months, we collected Daphnia from each mesocosm and raised them in the lab for three generations under low salt conditions (15 mg Cl− L−1). We then conducted a time-to-death experiment with varying concentrations of NaCl (30, 1300, 1500, 1700, 1900 mg Cl− L−1) to test for evolved tolerance. All Daphnia populations exhibited high survival when subsequently exposed to the lowest salt concentration (30 mg Cl− L−1). At the intermediate concentration (1300 mg Cl− L−1), however, populations previously exposed to elevated concentrations (i.e.100–1000 mg Cl− L−1) had higher survival than populations previously exposed to natural background levels (15 mg Cl− L−1). All populations survived poorly when subsequently exposed to the highest concentrations (1500, 1700, and 1900 mg Cl− L−1). Our results show that the evolution of tolerance to moderate levels of salt can occur within 2.5 months, or 5–10 generations, in Daphnia. Given the importance of Daphnia in freshwater food webs, such evolved tolerance might allow Daphnia to buffer food webs from the impacts of freshwater salinization.

The 22ⁿᵈ Asia-Pacific Economic Cooperation (APEC) Conference was held near Yanqi Lake, Huairou, in Beijing, China during November 10-11, 2014. To guarantee haze-free days during the APEC Conference, the Beijing government and the governments of the surrounding provinces implemented a series of controls. Three months of Aethalometer 880 nm black carbon (BC) measurements were examined to understand the hourly fluctuations in BC concentrations that resulted from emission controls and meteorology changes. Measurements were collected at the University of Chinese Academy of Sciences near the APEC Conference site and in Central Beijing at the Institute of Remote Sensing and Digital Earth of the Chinese Academy of Sciences. Synoptic conditions are successfully represented through analysis of backward trajectories in six cluster groups. The clusters are identified based on air mass transport from various areas such as Inner Mongolia, Russia, three northeastern provinces, and Hebei industrial areas, to the measurement sites. Air pollution control measures during the APEC Conference significantly reduced BC at the conference site (Huairou) and in Central Beijing, with greater reductions in BC concentrations at the conference site than in Central Beijing. The highest BC concentrations in Huairou were associated with air masses originating from Central Beijing rather than from the Hebei industrial region. The success of the control measures implemented in Beijing and the surrounding regions demonstrates that BC concentrations can be effectively reduced to protect human health and mitigate regional climate forcing. This study also demonstrates the need for regional strategies to reduce BC concentrations, since urban areas like Beijing are sources as well as downwind receptors of emissions.

Reservoirs typically have elevated fish mercury (Hg) levels compared to natural lakes and rivers. A unique feature of reservoirs is water-level management which can result in sediment exposure to the air. The objective of this study is to identify how reservoir water-level fluctuations impact Hg cycling, particularly the formation of the more toxic and bioaccumulative methylmercury (MeHg). Total-Hg (THg), MeHg, stable isotope methylation rates and several ancillary parameters were measured in reservoir sediments (including some in porewater and overlying water) that are seasonally and permanently inundated. The results showed that sediment and porewater MeHg concentrations were over 3-times higher in areas experiencing water-level fluctuations compared to permanently inundated sediments. Analysis of the data suggest that the enhanced breakdown of organic matter in sediments experiencing water-level fluctuations has a two-fold effect on stimulating Hg methylation: 1) it increases the partitioning of inorganic Hg from the solid phase into the porewater phase (lower log Kd values) where it is more bioavailable for methylation; and 2) it increases dissolved organic carbon (DOC) in the porewater which can stimulate the microbial community that can methylate Hg. Sulfate concentrations and cycling were enhanced in the seasonally inundated sediments and may have also contributed to increased MeHg production. Overall, our results suggest that reservoir management actions can have an impact on the sediment-porewater characteristics that affect MeHg production. Such findings are also relevant to natural water systems that experience wetting and drying cycles, such as floodplains and ombrotrophic wetlands.

Mainly due to automobile traffic, but also due to other sources, the platinum group elements (PGE) platinum (Pt), palladium (Pd) and rhodium (Rh) are introduced into aquatic biotopes where they accumulate in sediments of lakes and rivers. However, the toxicity of these noble metals to aquatic organisms is not well understood and especially toxicity studies under standardized condition are lacking. Thus, the toxicity of Pt, Pd and Rh to Daphnia magna was tested in single metal exposure experiments according to OECD guideline 202. Immobility and lethality was recorded after 24 h and 48 h of exposure and EC50 and LC50, respectively, were determined. As the nominal exposure concentration of Pd differed significantly from the quantified concentration, the control of the real exposure concentration by chemical analysis is mandatory, especially for Pd.The toxicity decreased in the order Pd > Pt ≫ Rh with e.g. LC50(48 h) values of 14 μg/L for Pd, 157 μg/L for Pt and 56,800 μg/L for Rh. The exposure period had a clear effect on the toxicity of Pt, Pd and Rh. For Pt and Rh the endpoint immobility was more sensitive than the endpoint lethality whereas Pd toxicity was similar for both endpoints. The Hill slopes, which are a measure for the steepness of the concentration-response curves, showed no significant discrepancies between the different metals.The binary metal exposure to Pt and Pd revealed a more-than-additive, i.e. a synergistic toxicity using the toxic unit approach. The present study is a start to understand the toxicity of interacting PGE. The modes of action behind the synergistic effect are unclear.

Se laden freshwater algae that enter the Salton Sea with river water pose ecorisks to wildlife in the lake by transferring selenium (Se) to higher trophic levels. The aim of this study was to investigate impacts of Se on Microcystis aeruginosa, widely distributed in freshwater bodies, and its relationship with toxicity, such as microcystins and Se residues. When supplied with selenite, the 96 h-IC50 was calculated 2.60 mg Se/L. However, these inhibitory effects did not extend to microcystin production, and the extracellular fraction significantly increased with selenite as well as sulfate. As M. aeruginosa assimilated selenite very efficiently, 97% of the removed Se was through accumulation, compared to 3% via volatilization, raising a concern about ecotoxicity caused by the remaining Se in the algae. The XAS analysis suggests the dominant Se species accumulated in the algal cells was elemental Se (81%), which is relatively nonbioavailable to aquatic organisms. We further investigated the potential fate of Se carried into the Salton Sea by M. aeruginosa with river water. Under hypersalinity stress, the biomass Se and intracellular microcystins were released and reduced by 47% and 74%, respectively, resulting in the increasing levels of Se and microcystins in the water column. CuSO4 was then applied as an algaecide to prevent M. aeruginosa from entering the lake. The results indicate a similar response to that under hypersalinity stress: the volatilization process was blocked and the Se and microcystins were released from the damaged algal cells in the presence of CuSO4, further raising toxicity levels by 8% and 60%, respectively, in the water column within 24 h. Overall, the coexistence of selenite and M. aeruginosa in river waters might negatively impact aquatic ecosystems of the Salton Sea and further research is required on how to harvest Se from M. aeruginosa to protect local wildlife.

We report a historical record of atmospheric deposition in dated sediment cores from Hasse Lake, ideally located near both currently and previously operational coal-fired power plants in Central Alberta, Canada. Accumulation rates of spheroidal carbonaceous particles (SCPs), an unambiguous marker of high-temperature fossil-fuel combustion, in the early part of the sediment record (pre-1955) compared well with historical emissions from one of North America's earliest coal-fired power plants (Rossdale) located ∼43 km to the east in the city of Edmonton. Accumulation rates in the latter part of the record (post-1955) suggested inputs from the Wabamun region's plants situated ∼17–25 km to the west. Increasing accumulation rates of SCPs, polycyclic aromatic hydrocarbons (PAHs) and Hg coincided with the previously documented period of peak pollution in the Wabamun region during the late 1960s to early 1970s, although Hg deposition trends were also similar to those found in western North American lakes not directly affected by point sources. A noticeable reduction in contaminant inputs during the 1970s is attributed in part to technological improvements and stricter emission controls. The over one hundred-year historical record of coal-fired power plant emissions documented in Hasse Lake sediments has provided insight into the impact that both environmental regulations and changes in electricity output have had over time. This information is crucial to assessing the current and future role of coal in the world's energy supply.

As the world burden of environmental contamination increases, it is of the utmost importance to develop streamlined approaches to environmental risk assessment in order to prioritize mitigation measures. Whole-cell biosensors or bioreporters and speciation modeling have both become of increasing interest to determine the bioavailability of pollutants, as bioavailability is increasingly in use as an indicator of risk. Herein, we examine whether bioreporter results are able to reflect expectations based on chemical reactivity and speciation modeling, with the hope to extend the research into a wider framework of risk assessment. We study a specific test case concerning the bioavailability of lead (Pb) in aqueous environments containing Pb-complexing ligands. Ligands studied include ethylene diamine tetra-acetic acid (EDTA), meso-2,3 dimercaptosuccinic acid (DMSA), leucine, methionine, cysteine, glutathione, and humic acid (HA), and we also performed experiments using natural water samples from Lake Tai (Taihu), the third largest lake in China. We find that EDTA, DMSA, cysteine, glutathione, and HA amendment significantly reduced Pb bioavailability with increasing ligand concentration according to a log-sigmoid trend. Increasing dissolved organic carbon in Taihu water also had the same effect, whereas leucine and methionine had no notable effect on bioavailability at the concentrations tested. We find that bioreporter results are in accord with the reduction of aqueous Pb2+ that we expect from the relative complexation affinities of the different ligands tested. For EDTA and HA, for which reasonably accurate ionization and complexation constants are known, speciation modeling is in agreement with bioreporter response to within the level of uncertainty recognised as reasonable by the United States Environmental Protection Agency for speciation-based risk assessment applications. These findings represent a first step toward using bioreporter technology to streamline the biological confirmation or validation of speciation modeling for use in environmental risk assessment.

Receptor models were typically used in air pollution studies and few publications are available for Positive Matrix Factorization (PMF) that consider the details of parameters and procedures in evaluating the trace organic pollutants in sediments. In this study, environmental fate and source composition of Lake Eymir sediments contaminated by polychlorinated biphenyls (PCBs) were explored by applying two PMF models, Paatero's PMF2 and United States Environmental Protection Agency's (US EPA) EPA-PMF3. PMF2 and EPA-PMF3 rely on different algorithms; Paatero's algorithm and multilinear engine algorithm, respectively. Here, the approaches of two PMF models were compared for the identification of PCB patterns taking into consideration the effects of various uncertainty matrices, residual matrices and goodness-of fit parameters. As a result of the study, it was understood that both models resolved five factors and indicated Clophen A60 as the source of PCBs. These results were consistent with the results resolved by Chemical Mass Balance model applied to the same data set in a previous study. However, source contributions identified by two models differed in quantity, but with similar patterns. This study indicates a way in understanding behavior, fate and global source of persistent organic pollutants in sediment by applying and comparing with a special data including high percentage of below detected value (38.2%) to understand the dynamics of PMF model parameters.

Polyhalogenated carbazoles (PHCZs) have attracted mounting environmental concerns since they were recently discovered in sediments and soil. Current knowledge on their occurrence, environmental behavior and fate remains very limited in general. In the present study, 11 PHCZ congeners were screened in surface sediments of Lake Tai, an important freshwater system located in the Yangtze River Delta, China. Total concentrations of PHCZs (∑PHCZs) ranged up to 15.8 ng/g dry weight (median: 1.54 ng/g dw), rivaling those of polybrominated diphenyl ethers (∑PBDEs, 0.07–15.9 ng/g dw) in the same sediments. The PHCZ congener composition profiles revealed a dominance of 3,6-dichlorocarbazole and 3,6-dibromocarbazole with comparable concentrations. These two dominant congeners differed in spatial distribution patterns in Lake Tai, indicating different sources or origins. Potential toxic effects associated with the levels of PHCZs in the sediments were evaluated via the toxic equivalent (TEQ) approach. The TEQs of PHCZs in Lake Tai sediments ranged up to 1.36 pg TEQ/g dw. As the first report on the occurrence of PHCZs in an Asian waterbody, our findings suggest that PHCZs should be given more attention during environmental monitoring and risk assessments of hazardous chemicals, as they may represent another group of persistent organic pollutants with dioxin-like effects and wide distributions.