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This study assessed the impact of on-site field-simulated oil spills at the International Institute for Sustainable Development-Experimental Lakes Area (IISD-ELA) on a freshwater boreal lake. Low total petroleum hydrocarbons (TPH) values were obtained in water and sediments from the locations without direct oil loading across the 6-year monitoring program. Biogenic n -alkanes and pyrogenic polycyclic aromatic hydrocarbons (PAHs) were predominant pre- and post-spill. No petroleum biomarkers were detected in the water, but trace levels appeared in a few sediments. Most TPH and PAH levels were within acceptable limits set by the Canadian Council of Ministers of the Environment (CCME) and Ontario regulations, though some PAHs exceeded guidelines. However, the frequency of exceedances did not change significantly before and after the spill. These results suggest that the spilled oil was contained effectively during the experiment period, and the environment recovered to near-background levels afterward with appropriate precautions and remediation operations. • Six years of field surveys were conducted before and after simulated oil spill projects. • Biogenic and pyrogenic inputs are primary for n-alkanes and PAHs, respectively. • All TPH and most PAH values are lower than the national and provincial guidelines. • The frequency of PAH guideline exceedances remains largely unchanged throughout the 6 years. • The area used for simulated oil spills was unaffected by project operations. [ABSTRACT FROM AUTHOR]

Goldstone radar facility is used for surveying the prominent structures on the surface of Mars, at wavelengths of 3.5 and 13 centimeters. Tyrrhena Patera, Melas Dorsa, Nectaris Fossae, Ma'adim Vallis long channel and basin Huygens are surveyed by delay-Doppler observations. Numerous sites in the heavily cratered highlands are also included in the survey. The surveyed areas have local topographic lows, with depths in different ranges from 200 to 800 meters. The valleys have average slopes of 1%, as indicated by the radar profiles.

Old plateaus of Mars have numerous small valleys which are only a few kilometers wide, and their length varies from few kilometers to more than 50 kilometers. The valleys have smoothly curved shapes and valley-side slopes. This is indicated by the study of the topographic profiles found across several valleys determined by one dimensional photoclinometry. A few of the unusual valleys near the flanks of Alba Patera also have smoothly curved shapes and valley-side slopes. The valley slide slope have inclination ranging between 10 degrees and 20 degrees.

Background: Interest has risen in identifying individuals at high risk of incident Parkinson's disease (PD) to facilitate inclusion in neuroprotective treatment trials. Current risk estimates of prodromal markers are based on aggregated data of an entire population, but this approach disregards differences in risk estimates by subgroups of a population. In this proof of concept, we determine subgroup-specific risk estimates of olfactory dysfunction for incident PD.Methods: PubMed, EMBASE and Cochrane were searched for prospective studies investigating the association between olfactory dysfunction and incident PD. Random-effects meta-analysis, subgroup analyses and meta-regression were performed to investigate general and subgroup risk estimates.Results: Individuals with odor identification dysfunction seemed to be at greater risk of incident PD compared to controls without olfactory dysfunction (OR = 4.18; 95%CI [2.47-7.07]). Risk estimates were higher in studies that included higher percentages of women (regression slope β = 0.053 increase in log odds ratio per 1% increase 1%, p = 0.0006), increased with mean study age (β = 0.21 per one year increase; p = 0.005) and in REM-sleep behavior disorder cohorts (β = 1.95; p = 0.03). Furthermore, the association between olfactory dysfunction and incident PD was most distinct in studies with shorter follow-up duration (ß = -0.56; p = 0.0047).Conclusion: The presence of olfactory dysfunction conveys a considerably elevated risk of incident PD, likely more in studies with a higher proportion of women, older individuals or short follow-up duration. Individual patient data are warranted to confirm these findings and to yield subgroup-specific risk estimates of other common markers to refine prodromal PD criteria. [ABSTRACT FROM AUTHOR]

Mercury (Hg) contamination in aquatic systems can lead to adverse human and environmental health outcomes. Yellowknife, a city in Canada's Northwest Territories, is a historic mining community, with two large gold mines (Giant Mine and Con Mine) that used Hg amalgamation methods to extract gold between ∼1938 and 1960. We analyzed dated sediment cores from 20 small lakes to investigate the spatial and temporal Hg deposition patterns within 50 km of Giant Mine. Breakpoint analysis of the within-lake z-score normalized anthropogenic Hg flux indicates two significant time periods of changing emission rates. The first is a significant increase in Hg deposition rate (∼1925) during the time of gold exploration in the region and onset of Hg amalgamation (1938) and the second is a significant decrease in deposition rate that begins around the time of the cessation of Hg amalgamation at Giant Mine (∼1959). Sediment Hg concentrations exceeded the Canadian Council for Ministers of the Environment Interim Sediment Quality Guideline (ISQG) for Hg (0.17 mg/kg dw) in 55% of the lakes (n = 11) during mining (1948–1999). All lakes within 5 km of the Giant Mine roaster stack exceeded CCME ISQG during mining (n = 8), with a 4-fold increase in total Hg concentration observed during mining at these near-field (<5 km from stack) sites. We observed evidence of enriched Hg in near-field, mid-field, and far-field sites. The elevated sedimentary Hg concentrations during mining in near-field sites would have posed a hazard to human and wildlife health during the height of emissions, however the significant decrease in Hg concentrations since the closure of mines in the region demonstrate the potential for recovery in these aquatic ecosystems. [Display omitted] • Lakes <5 km from the Giant Mine were affected by Hg emissions from mines. • Lakes >20 km likely received inputs primarily from global sources. • Hg inputs to the lakes decreased after the cessation of roasting mercury amalgams. • Hg flux time trends are consistent with the regional history of Hg amalgamation. • Hg concentrations exceeded sediment quality guidelines in 55% of lakes. [ABSTRACT FROM AUTHOR]

Abstract Marked increases in ring-billed gulls and double-crested cormorants in the Laurentian Great Lakes during the last century have garnered attention over their ecological impacts, sparking debates about management strategies. However, monitoring data are generally sparse and of short duration for these colonies, hampering the ability to place recent changes within long-term context. Sediment records from ponds immediately surrounded by colonies on nesting islands can be used to track past bird populations, as they release wastes with geochemical signals that can be tracked using traditional paleolimnological methods, such as diatoms and stable isotopes of nitrogen (δ15N). Here, we provide new information about waterbird nesting histories on islands in eastern Lake Ontario that are of interest to wildlife managers. In all bird-impacted ponds, eutrophic diatom assemblages and elevated sediment chlorophyll- a coincided with high signatures of δ15N in the recent sediments, signifying bird influence. An absence of significant bird impacts in the oldest portion of one sediment core indicates that the current cormorant colony size (>2000 birds) is unprecedented over the ~150-year record. Diatoms and sediment chlorophyll- a also responded to even a small, short-duration cormorant nesting event on an actively managed reference island. Collating our findings with those from four previously studied sediment cores from nearby islands, we show that cormorants are unlikely to have occupied eastern Lake Ontario in their current numbers within the past ~150 years. However, ring-billed gulls have likely used several islands in the area for most of the 20th century (and perhaps earlier) until present. [ABSTRACT FROM AUTHOR]

Most small valleys in the ancient highlands of Mars are probably the result of erosion by groundwater sapping. This conclusion together with the fact that liquid water is thermodynamically unstable on the surface of Mars today is frequently used to argue that the planet was warmer in the past. The strength of these arguments is tested by examining the effectiveness of the sapping mechanism under various climatic and hydrologic conditions, including aquifer permeability, aquifer temperature, sediment grain size, wind speed at the surface, latitude, and obliquity. Numerical simulations of groundwater sapping under different conditions indicate that the link between the small valleys and a warmer early martian climate is not as strong as is often assumed. If water in the upper few hundred meters of the martian regolith had been kept above the freezing point through hydrothermal circulation or conduction of geothermal heat, then the small martian valleys could have formed by groundwater sapping under climatic conditions like those that prevail today, especially if the permeability of the martian regolith is like that of terrestrial gravels. Geothermal warming to temperatures well above the freezing point would have greatly facilitated sapping. The current low-pressure atmosphere is more conducive to the sapping process (though not necessarily to subsequent stream flow) than a high-pressure atmosphere that is only slightly warmer. [C] 2000 Academic Press Key Words: Mars; surface; geological processes.

Recent climate change may be enhancing mercury fluxes to Arctic lake sediments, confounding the use of sediment cores to reconstruct histories of atmospheric deposition. Assessing the independent effects of climate warming on mercury sequestration is challenging due to temporal overlap between warming temperatures and increased long-range transport of atmospheric mercury following the Industrial Revolution. We address this challenge by examining mercury trends in short cores (the last several hundred years) from eight lakes centered on Cape Herschel (Canadian High Arctic) that span a gradient in microclimates, including two lakes that have not yet been significantly altered by climate warming due to continued ice cover. Previous research on subfossil diatoms and inferred primary production indicated the timing of limnological responses to climate warming, which, due to prevailing ice cover conditions, varied from ∼1850 to ∼1990 for lakes that have undergone changes. We show that climate warming may have enhanced mercury deposition to lake sediments in one lake (Moraine Pond), while another (West Lake) showed a strong signal of post-industrial mercury enrichment without any corresponding limnological changes associated with warming. Our results provide insights into the role of climate warming and organic carbon cycling as drivers of mercury deposition to Arctic lake sediments. [ABSTRACT FROM AUTHOR]

Eutrophication, which remains one of the greatest threats to water quality worldwide, is particularly acute in agricultural areas. Here we assessed long-term drivers of potential pollution inputs to lakes in southwest Nova Scotia (Canada), a region marked by fur farming (mainly mink) and other agricultural activities. We used a BACI (before-after-control-impact) study design with sediment cores collected from 14 lakes selected based on their proximity to mink farms. We combined economic data, mink faecal samples, and a series of geochemical markers in dated sediment cores, including sterols, δ15N, visible reflectance spectroscopy (VRS)-inferred chlorophyll- a , and heavy metals, to relate changes in sediment geochemistry to the growth of mink farms in the region. Sterol biomarkers (cholesterol and β-sitosterol) measured in a range of samples (i.e. mink faeces and feed, aquaculture feed), were elevated where mink farms were located close to each study lake. Mink-related sterols (cholesterol, β-sitoserol), δ15N measurements, VRS chlorophyll- a , and heavy metals As, Cu, Sr increased in the 1980s coeval with a ∼400% increase of mink farms in the region, especially near Nowlans Lake. Agricultural impacts were subtler in other lakes. Our study expands on prior applications of geochemical fingerprinting in forensic paleolimnology when direct monitoring data are incomplete. This multi-proxy approach has promising applications for environmental pollution assessments in other lake ecosystems experiencing water quality issues. [Display omitted] • Chemical fingerprints in dated sediments track the history of mink farm activity. • Sterols, δ15N, Sr, As, and Cu track historical releases from mink farms. • Chemical markers increase in the 1980s coeval with increased mink farm activity. [ABSTRACT FROM AUTHOR]

The synthetic polycyclic musks HHCB (Galaxolide ® ) and AHTN (Tonalide ® ) were monitored in fathead minnows (FHMs) caged for a month at various locations in the North Saskatchewan River (NSR), upstream and downstream of the Gold Bar wastewater treatment plant that serves the city of Edmonton, AB, Canada. In addition, the distribution of these musk compounds in the river was predicted using the fugacity-based Quantitative Water Air Sediment Interface (QWASI) model. In FHMs caged 0.15 km downstream of the wastewater outfall, mean concentrations of HHCB and AHTN were 7.4 and 0.4 μg g −1 wet weight, respectively. These are among the highest reported concentrations of these musk compounds in fish exposed to treated wastewater. The musk concentrations in FHMs were significantly lower further downstream of the outfall. High bioconcentration factors (BCFs) in FHMs that exceeded 10 4 higher than estimated concentrations in water indicated that there were low rates of biotransformation of the musks in the fish. In the FHMs caged at the site closest to the wastewater outfall, HHCB concentrations in FHMs were comparable to the body burdens that have been reported to moderate expression of vitellogenin in female rainbow trout, indicating that fish in the NSR downstream of the wastewater outfall may be at risk of anti-estrogenic effects. The QWASI model applied to six individual river sections of the NSR predicted that the largest fluxes of HHCB and AHTN would be for downstream transport in water, which explains why FHMs accumulated elevated concentrations of the musks at the furthest downstream site, 9.9 km from the wastewater discharge. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Most future growth in the Alberta bituminous sands will be based on thermal in - situ recovery technologies. To date, however, most attention on the environmental effects of bitumen recovery has focused on surface mining in the Athabasca region. Recent uncontrolled bitumen flow-to-surface incidents (FTS; appearance at the surface of bitumen emulsions from deep subsurface recovery zones) reported at the Cold Lake heavy oil fields highlight the need to better understand the potential role of in - situ extraction as a source of contaminants to landscapes and surface waters. We analyzed sediment cores from a lake located ∼2 km away from a recent bitumen FTS incident to provide a long-term perspective on the delivery of metals, polycyclic aromatic compounds (PACs), and polychlorinated biphenyls (PCBs) to surface freshwaters, and to assess whether the onset of local in - situ bitumen extraction can be linked to contaminant increases in nearby lakes. An increase in alkyl PACs coincided with the onset and expansion of commercial in - situ bitumen extraction, and multiple lines of evidence indicate a petrogenic source for recent alkyl PAC enrichment. However, no coincident increase in vanadium (enriched in bitumen) occurred that would suggest the source of petrogenic PAC enrichment is direct input of bituminous particles. Our results show that, similar to surface mining in the Athabasca region, activities associated with in - situ extraction can increase the burden of petrogenic PACs in nearby lakes, but many questions still remain regarding the exact sources and pathways of PACs into the environment. Given that more than 80% of Alberta's bitumen reserves can only be accessed using in - situ technologies, we recommend that this be made a research priority. [ABSTRACT FROM AUTHOR]