Density-dependent processes fluctuate over 50 years in an ecotone forest.

Spatial patterns can inform us of forest recruitment, mortality, and tree interactions through time and disturbance. Specifically, successional trajectories of self-thinning and heterospecific negative density dependence can be interpreted from the spatial arrangement of forest stems. We conducted a 50-year spatial analysis of a forest undergoing succession at the ecotone of the southwestern Canadian boreal forest. The forest progressed from early to late sere and experienced repeated severe droughts, forest tent caterpillar outbreaks (Malacosoma disstria), as well as the outbreak of bark beetles. Cumulatively, the forest lost 70% of stems due to natural succession and a combination of disturbance events. Here, we describe spatial patterns displaying signals of successional self-thinning, responses to disturbance, and changes in patterns of density dependence across 50 years. Forest succession and disturbance events resulted in fluctuating patterns of density-dependent mortality and recruitment that persisted into late seral stages. The combined effects of conspecific and heterospecific density-dependent effects on mortality and recruitment resulted in near-spatial equilibrium over the study period. However, the strength and direction of these demographic and spatial processes varied in response with time and disturbance severity. The outbreak of forest tent caterpillar, pronounced drought, and bark beetles combined to reduce stand aggregation and promote a spatial equilibrium. Density-dependent processes of competition and facilitation changed in strength and direction with succession of the plot and in combination with disturbance. Together these results reinforce the importance of successional stage and disturbance to spatial patterns.

Sphagnum Moss as an Indicator of Contemporary Rates of Atmospheric Dust Deposition in the Athabasca Bituminous Sands Region.

Sphagnum moss was collected from ombrotrophic (rain-fed) peat bogs to quantify dust emissions from the open-pit mining and upgrading of Athabasca bituminous sands (ABS). A total of 30 bogs were sampled in the ABS region, and 5 were sampled in central Alberta. Ash was separated into the acid-insoluble ash (AIA) and acid-soluble ash (ASA) fractions using HCl. The AIA concentrations increase toward industry from 0.4 ± 0.5% to 4.7 ± 2.0% over a distance of 30 km; the control site at the Utikuma Region Study Area (URSA) yielded 0.29 ± 0.07% (n = 30). Mass accumulations rates showed similar spatial variation. The morphology and mineralogy of the AIA particles were studied using scanning electron microscopy and energy-dispersive X-ray analysis and the particle size distributions using optical methods. Particle size was more variable in moss closer to industry. Major ions in the ASA fraction showed elevated accumulation rates of Ca, K, Fe, Mg, P, and S, with P being up to 5 times greater in samples nearest industry compared to those in distal locations. Given that P has been regarded as the growth-limiting nutrient in bogs, fertilization of nutrient-poor ecosystems, such as these from fugitive emissions of dusts from open-pit mining, may have long-term ecological ramifications.

Characterization of Naphthenic Acids and Other Dissolved Organics in Natural Water from the Athabasca Oil Sands Region, Canada.

With growth of the Canadian oil sands industry, concerns have been raised about possible seepage of toxic oil sands process-affected water (OSPW) into the Athabasca River (AR). A sampling campaign in fall 2015 was undertaken to monitor for anthropogenic seepage while also considering natural sources. Naphthenic acids (NAs) and thousands of bitumen-derived organics were characterized in surface water, groundwater, and OSPW using a highly sensitive online solid phase extraction-HPLC-Orbitrap method. Elevated NA concentrations and bitumen-derived organics were detected in McLean Creek (30.1 µg/L) and Beaver Creek (190 µg/L), two tributaries that are physically impacted by tailings structures. This was suggestive of OSPW seepage, but conclusive differentiation of anthropogenic and natural sources remained difficult. High NA concentrations and bitumen-derived organics were also observed in natural water located far north of the industry, including exceedingly high concentrations in AR groundwater (A5w-GW, 2000 µg/L) and elevated concentration in a tributary river (Pierre River, 34.7 µg/L). Despite these evidence for both natural and anthropogenic seepage, no evidence of any bitumen-derived organics was detected at any location in AR mainstem surface water. The chemical significance of any bitumen-derived seepage to the AR was therefore minimal, and focused monitoring in tributaries will be valuable in the future.

Peat Bogs Document Decades of Declining Atmospheric Contamination by Trace Metals in the Athabasca Bituminous Sands Region.

Peat cores were collected from five bogs in the vicinity of open pit mines and upgraders of the Athabasca Bituminous Sands, the largest reservoir of bitumen in the world. Frozen cores were sectioned into 1 cm slices, and trace metals determined in the ultraclean SWAMP lab using ICP-QMS. The uppermost sections of the cores were age-dated with 210Pb using ultralow background gamma spectrometry, and selected plant macrofossils dated using 14C. At each site, trace metal concentrations as well as enrichment factors (calculated relative to the corresponding element/Th ratio of the Upper Continental Crust) reveal maximum values 10 to 40 cm below the surface which shows that the zenith of atmospheric contamination occurred in the past. The age-depth relationships show that atmospheric contamination by trace metals (Ag, Cd, Sb, Tl, but also V, Ni, and Mo which are enriched in bitumen) has been declining in northern Alberta for decades. In fact, the greatest contemporary enrichments of Ag, Cd, Sb, and Tl (in the top layers of the peat cores) are found at the control site (Utikuma) which is 264 km SW, suggesting that long-range atmospheric transport from other sources must be duly considered in any source assessment.

Catheter-related blood stream infections in hemodialysis patients: a prospective cohort study.

BACKGROUND: For people requiring hemodialysis, infectious mortality is independently associated with geographic distance from a nephrologist. We aimed to determine if differential management of catheter-related blood stream infections (CRBSIs) could explain poorer outcomes. METHODS: We prospectively collected data from adults initiating hemodialysis with a central venous catheter between 2005 and 2015 in Alberta, Canada. We collected indicators of CRBSI management (timely catheter removal, relapsing bacteremia); frequency of CRBSIs; hospitalizations; predictors of CRBSIs, and bacteremia. We evaluated indicators and infectious episodes as a function of the shortest distance by road to the closest nephrologist's practice: <50 (referent); 50-99; and ≥100 km. RESULTS: One thousand one hundred thirty-one participants were followed for a median of 755 days (interquartile range (IQR) 219, 1465) and used dialysis catheters for a median of 565 days (IQR 176, 1288). Compared to the referent group, there was no significant difference in the rate ratio (RR) of CRBSI in the 50-100 and >100 km distance categories: RR 1.63; 95% confidence interval (CI) (0.91, 2.91); RR 0.84 (95% CI 0.44, 1.58); p = 0.87, respectively or in bacteremia: RR 1.42; (95% CI 0.83, 2.45); RR 0.79 (95% CI 0.45,1.39) p = 0.74, respectively. There were no differences in indicators of appropriate CRBSI management or hospitalizations according to distance. The overall incidence of CRBSIs was low (0.19 per 1000 catheter days) as was the frequency of relapse. Only liver disease was independently associated with CRBSI (RR 2.11; 95% CI 1.15, 3.86). CONCLUSIONS: The frequency and management of CRBSIs did not differ by location; however, event rates were low.

Airborne Petcoke Dust is a Major Source of Polycyclic Aromatic Hydrocarbons in the Athabasca Oil Sands Region.

Oil sands mining has been linked to increasing atmospheric deposition of polycyclic aromatic hydrocarbons (PAHs) in the Athabasca oil sands region (AOSR), but known sources cannot explain the quantity of PAHs in environmental samples. PAHs were measured in living Sphagnum moss (24 sites, n = 68), in sectioned peat cores (4 sites, n = 161), and snow (7 sites, n = 19) from ombrotrophic bogs in the AOSR. Prospective source samples were also analyzed, including petroleum coke (petcoke, from both delayed and fluid coking), fine tailings, oil sands ore, and naturally exposed bitumen. Average PAH concentrations in near-field moss (199 ng/g, n = 11) were significantly higher (p = 0.035) than in far-field moss (118 ng/g, n = 13), and increasing temporal trends were detected in three peat cores collected closest to industrial activity. A chemical mass-balance model estimated that delayed petcoke was the major source of PAHs to living moss, and among three peat core the contribution to PAHs from delayed petcoke increased over time, accounting for 45-95% of PAHs in contemporary layers. Petcoke was also estimated to be a major source of vanadium, nickel, and molybdenum. Scanning electron microscopy with energy-dispersive X-ray spectroscopy confirmed large petcoke particles (>10 µm) in snow at near-field sites. Petcoke dust has not previously been considered in environmental impact assessments of oil sands upgrading, and improved dust control from growing stockpiles may mitigate future risks.

Relocation of remote dwellers living with hemodialysis: a time trade-off survey.

BACKGROUND: There has been little research exploring the experience of dialysis therapy for people living in remote communities. Remote residence location has previously been associated with excess mortality in hemodialysis (HD) patients, suggesting that relocation to a referral center might improve outcomes. It is unknown whether patients view this approach as acceptable. METHODS: We studied 121 remote-dwelling chronic HD patients using the time trade-off method applied to hypothetical scenarios. RESULTS: Participants indicated that they would trade a median of 6 years of life in their current location (including current social supports) (95% CI 2.25-7) for 10 years of life in a referral center without any of their existing social supports (meaning they would be willing to forgo 4 years of life to remain in their current residence location). When current social supports were assumed to continue in both locations, people were only willing to forego a median of 2 years of life (95% CI 1-4) to remain in their current location. Older participants were much less willing to accept relocation than younger participants; the median time trade-off associated with relocation and without social supports was 2 years for participants aged <50 years, 3 years for those aged 50-69.9 years and 9 years for those aged ≥70 years. CONCLUSIONS: Hemodialysis patients currently living remotely were willing to forgo much of their remaining life expectancy rather than relocate-especially among older participants. These findings suggest that decisions about relocation should be accompanied by discussion of anticipated changes in quality of life and life expectancy.

Potentially preventable hospitalization as a complication of CKD: a cohort study.

BACKGROUND: Ambulatory care-sensitive conditions have been described as those that (if appropriately managed in an outpatient setting) generally do not require subsequent hospitalization. Our goal was to identify clinical populations of people who are at the highest risk of ambulatory care-sensitive conditions related to chronic kidney disease (CKD). STUDY DESIGN: Retrospective cohort study. SETTING & PARTICIPANTS: 2,003,054 adults (including 238,747 adults with CKD) residing in Alberta, Canada, with at least one serum creatinine measurement between 2002 and 2009. PREDICTORS: Estimated glomerular filtration rate and albuminuria categories, CKD status, demographics, and clinical characteristics. OUTCOMES: Hospitalization with heart failure, hyperkalemia, volume overload, or malignant hypertension. MEASUREMENTS: We used the Alberta Kidney Disease Network database, which incorporates data from Alberta Health, the Northern and Southern Alberta Renal Programs, and clinical laboratories in Alberta. RESULTS: During a median follow-up of 4.1 years, 43,863 participants were hospitalized for heart failure; 6,274 participants, for hyperkalemia; 2,035 participants, for volume overload; and 481 participants, for malignant hypertension. All 4 conditions were more common at lower estimated glomerular filtration rates and in the presence of albuminuria. In the subset of participants with CKD, heart failure, hyperkalemia, and volume overload were associated most strongly with older age, diabetes, chronic liver disease, and prior heart failure. Malignant hypertension was associated with prior hypertension, aboriginal status, and peripheral vascular disease. Remote-dwelling participants were more likely to experience heart failure and malignant hypertension than those living closer to providers. LIMITATIONS: No data for medication use or potentially important process-based outcomes for study participants. CONCLUSIONS: Our findings suggest that future studies seeking to determine how to prevent ambulatory care-sensitive conditions in people with CKD should target remote dwellers and those with comorbid conditions such as concomitant heart failure and liver disease.

Sphagnum mosses from 21 ombrotrophic bogs in the athabasca bituminous sands region show no significant atmospheric contamination of "heavy metals".

Sphagnum moss was collected from 21 ombrotrophic (rain-fed) peat bogs surrounding open pit mines and upgrading facilities of Athabasca bituminous sands in Alberta (AB). In comparison to contemporary Sphagnum moss from four bogs in rural locations of southern Germany (DE), the AB mosses yielded lower concentrations of Ag, Cd, Ni, Pb, Sb, and Tl, similar concentrations of Mo, but greater concentrations of Ba, Th, and V. Except for V, in comparison to the "cleanest", ancient peat samples ever tested from the northern hemisphere (ca. 6000-9000 years old), the concentrations of each of these metals in the AB mosses are within a factor of 3 of "natural, background" values. The concentrations of "heavy metals" in the mosses, however, are proportional to the concentration of Th (a conservative, lithophile element) and, therefore, contributed to the plants primarily in the form of mineral dust particles. Vanadium, the single most abundant trace metal in bitumen, is the only anomaly: in the AB mosses, V exceeds that of ancient peat by a factor of 6; it is therefore enriched in the mosses, relative to Th, by a factor of 2. In comparison to the surface layer of peat cores collected in recent years from across Canada, from British Columbia to New Brunswick, the Pb concentrations in the mosses from AB are far lower.

Quality-of-care indicators among remote-dwelling hemodialysis patients: a cohort study.

BACKGROUND: We hypothesized that the higher mortality for hemodialysis patients who live farther from the closest attending nephrologist compared with patients living closer might be due to lower quality of care. STUDY DESIGN: Population-based longitudinal study. SETTING & PARTICIPANTS: All adult maintenance hemodialysis patients with measurements of quality-of-care indicators initiating hemodialysis therapy between January 2001 and June 2010 in Northern Alberta, Canada. PREDICTORS: Hemodialysis patients were classified into categories based on the distance by road from their residence to the closest nephrologist: ≤50 (referent), 50.1-150, 150.1-300, and >300 km. OUTCOMES: Quality-of-care indicators were based on published guidelines. MEASUREMENTS: Quality-of-care indicators at 90 days following initiation of hemodialysis therapy and, in a secondary analysis, at 1 year. RESULTS: Measurements were available for 1,784 patients. At baseline, the proportions of patients residing in each category were 69% for ≤50 km to closest nephrologist; 17%, 50.1-150 km; 7%, 150.1-300 km; and 7%, >300 km. Those who lived farther away from the closest nephrologist were less likely to have seen a nephrologist 90 days prior to the initiation of hemodialysis therapy (P for trend = 0.008) and were less likely to receive Kt/V of 1.2 (adjusted OR, 0.50; 95% CI, 0.30-0.84; P for trend = 0.01). Remote location also was associated with suboptimal levels of phosphate control (P for trend = 0.005). There were no differences in the prevalence of arteriovenous fistulas or grafts or hemoglobin levels across distance categories. LIMITATIONS: Registry data with limited data for non-guideline-based quality indicators. CONCLUSIONS: Although several quality-of-care indicators were less common in remote-dwelling hemodialysis patients, these differences do not appear sufficient to explain the previously noted disparities in clinical outcomes by residence location.

Sources, spatial-distributions and fluxes of PAH-contaminated dusts in the Athabasca oil sands region.

Atmospheric deposition of polycyclic aromatic hydrocarbons (PAHs) has increased in northern Alberta, Canada, due to industrial development in the Athabasca oil sands region (AOSR). However, the sources, summertime deposition fluxes and associated spatial patterns are poorly characterized, and the magnitude of contamination has not been directly contrasted with comparable measurements around large Canadian cities. PAHs were measured in Sphagnum moss collected from 30 bogs in the AOSR and compared with reference moss collected from various remote, rural and near-urban sites in Alberta and Ontario. At all 39 locations, strong correlations between depositional fluxes of PAHs and accumulation rates of ash (n = 117, r = 0.877, p < 0.001) implied that the main source of PAHs to moss was atmospheric deposition of particles. Average PAH concentrations at near-field AOSR sites (mean [SD], 62.4 [24.3] ng/g) were significantly higher than at far-field AOSR sites (44.9 [20.8] ng/g; p = 0.038) or the 7 reference sites in Alberta (20.6 [3.5] ng/g; p < 0.001). In fact, average PAH concentrations across the entire AOSR (7,850 km2) were approximately twice as high as in London, Ontario, or near petroleum upgrading and major traffic corridors in Edmonton, Alberta. A chemical mass balance model estimated that both delayed petcoke (33 % of PAHs) and fine tailings (38 % of PAHs) were the major sources of PAHs in the AOSR. Over the 2015 summer growing season, we estimate that 101-110 kg of PAHs (on 14,300-17,300 tonnes of PAH-containing dusts) were deposited to the AOSR within a 50 km radius of surface mining. Given that the highest PAH deposition was to the northern quadrant of the AOSR, which includes the First Nations community of Fort MacKay, further dust control measures should be considered to protect human and environmental health in the region.

Higher mortality among remote compared to rural or urban dwelling hemodialysis patients in the United States.

Living far away from specialized care centers is a potential barrier to the delivery of quality health care and has been associated with adverse outcomes. To assess mortality as a function of distance from the closest hemodialysis unit, and as a function of rural rather than urban residence, we analyzed prospectively collected data on 726,347 adults initiating chronic hemodialysis in the United States over a 13-year period. Participants were classified into categories of 0-10 (referent), 11-25, 26-45, 46-100, and remote living over 100 miles from the closest hemodialysis unit. After a median follow-up of 2.7 years (range 0 to 12.7 years), 368,569 patients died. Compared to the referent group, the adjusted hazard ratio of death was 1.01, 0.99, 0.96, and 1.21, respectively. When residence location was classified using rural-urban commuter areas, 16.5, 66.8, and 16.7% of patients lived in urban, micropolitan, and metropolitan areas, respectively. Compared with those living in metropolitan areas, the adjusted hazard ratio of mortality among patients residing in micropolitan and rural communities was 1.02 and 1.01, respectively. Thus, remote but not rural residence was associated with increased mortality among patients initiating chronic hemodialysis treatment in the United States.

Spatial analysis to locate new clinics for diabetic kidney patients in the underserved communities in Alberta.

BACKGROUND: Canadians with chronic diseases often live far away from healthcare facilities, which may compromise their level of care. We used a new method for selecting optimal locations for new healthcare facilities in remote regions. METHODS: We used a provincial laboratory database linked to data from the provincial health ministry. From all patients with serum creatinine measured at least once between 2002 and 2008 in Alberta, Canada, we selected those with diabetes and an estimated glomerular filtration rate (eGFR) of 15-60 mL/min/1.73 m(2). We then used two methods to select potential locations for new clinics that would serve the greatest number of remote-dwelling patients: plots showing the unadjusted density of such patients per 100 km(2) and SatScan analysis presenting the prevalent clusters of patients on the basis of chronic kidney disease (CKD) rates (adjusted for population size). RESULTS: We studied 32,278 patients with concomitant diabetes and CKD. A substantial number of patients (8%) resided >200 km from existing nephrologists' clinics. Density plots mapped with ArcGIS were useful for localizing a large cluster of underserved patients. However, objective assessment with SatScan technique and ArcGIS permitted us to detect additional clusters of patients in the northwest and southeast regions of Alberta--and suggested potential locations for new clinics in these areas. CONCLUSIONS: Objective techniques such as SatScan can identify clusters of underserved patients with CKD and identify potential new facility locations for consideration by decision-makers. Our findings may also be applicable to patients with other chronic diseases.

Impact of the 2016 Fort McMurray wildfires on atmospheric deposition of polycyclic aromatic hydrocarbons and trace elements to surrounding ombrotrophic bogs.

Fort McMurray and the Athabasca oil sands region (AOSR) experienced major wildfires in 2016, but the impact of these on regional deposition of polycyclic aromatic hydrocarbons (PAHs) and trace elements has not been reported nor compared to industrial sources of these pollutants in the region. Living moss (Sphagnum fuscum) was collected in triplicate from five ombrotrophic bogs in the AOSR after the wildfires, and analyzed for PAHs and trace elements. These post-wildfire data were compared to data from previous years at the same sites, and also to remote reference bogs in Alberta and Ontario. Elevated post-wildfire concentrations and flux of naphthalene and fluorene were observed at all five bogs in the AOSR, but no consistent trend was evident for higher molecular weight PAHs or the sum of priority PAHs (∑13PAH). Trace elements at most AOSR bogs were not elevated post-wildfire, except at one bog in the burned area (MIL), but even here the elements that were increased (1.7-5.6 × ) were likely of bitumen-origin (i.e., V, Ni, Se, Mo and Re). Significant post-wildfire correlations between PAHs and most trace elements suggested a common source, and few significant correlations were observed with retene, suggesting that wildfires were not the dominant source of most contaminants detected. Mass balance receptor models were used to apportion sources, indicating that the major sources of trace elements among five AOSR bogs post-wildfire were oil sands ore (mean 42%), haul road dust (17%), and petcoke (11%), whereas wildfire was always a minor source (3-4%). For PAHs at the most contaminated site (MIL), delayed petcoke (27%) and wildfire (25%) were the major sources, but the contribution of wildfire to PAHs at other sites was less or not discernable. Impacts of the 2016 wildfires on regional atmospheric deposition of major pollutants was less than from ongoing deposition of anthropogenic dust from oil sands activities.

Ambulance use, distance and outcomes in patients with suspected cardiovascular disease: a registry-based geographic information system study.

BACKGROUND: Despite guideline recommendations, the majority of patients with symptoms suggestive of acute coronary syndrome do not use emergency medical services to reach the emergency department (ED). The aim of this study was to investigate the factors associated with EMS utilisation and subsequent patient outcomes. METHODS: Using administrative data, all patients who presented to an ED in the metropolitan areas of Edmonton and Calgary in the years of 2007-2013 with main ED diagnosis of acute coronary syndrome, stable angina or chest pain were included. The travel distance was estimated using the geographic information system method to approximate the distance between the ED and patient home. The clinical endpoints were the 7-day and 30-day all-cause events (death, re-hospitalisation and repeat ED visit). RESULTS: Of 50,881 patients, 30.5% presented by emergency medical services. Patients with older age, female sex, ED diagnosis of acute coronary syndrome, more comorbidities and lower household income were more likely to use emergency medical services to reach the hospital. Longer travel distance was associated with higher emergency medical services use (odds ratio 1.09, 95% confidence interval 1.09-1.10), but it was not a predictor of clinical events. After adjustment for covariates and inverse propensity score weighting, emergency medical services use was associated with a higher risk of 7-day and 30-day clinical events. CONCLUSION: Several demographic and clinical features were associated with higher emergency medical services use including geographical variation. Although longer travel distance was shown to be linked to higher emergency medical services use, it was not an independent predictor of patient outcome. This has implications for the design of emergency medical services systems, triage and early diagnosis and treatment options.

Trace metals in the dissolved fraction (<0.45µm) of the lower Athabasca River: Analytical challenges and environmental implications.

Water samples were collected on the Athabasca River (AR), upstream and downstream from bitumen mines and upgrading facilities, to identify changes in water quality due to industrial activities in this region of northern Alberta, Canada. Starting upstream of Fort McMurray and proceeding downstream ca. 100km, waters were collected in duplicate at 13 locations on the main stem of the river, as well as 5 tributary streams, using ultraclean sampling protocols developed for polar snow and ice. To estimate potential bioaccessibility, trace elements of concern (Ag, Cd, Pb, Sb, Tl) were determined in the dissolved fraction (<0.45µm) along with metals known for their enrichments in bitumen (V, Ni, Mo, Re) and those found mainly in ionic (Li, Sr) or colloidal forms (Al, Co, Cr, Fe, Ga, Mn, Th, Y). Analyses were performed in the metal-free, ultraclean SWAMP lab using quadrupole and sector-field ICP-MS. Concentrations of Ag, Cd, Pb, Sb and Tl were extremely low, not significantly more abundant downstream of industry and probably reflect "background" values. In contrast, V, Ni, Mo and Re concentrations were all significantly (p<0.05) greater downstream of industry. However, chloride also increased downstream, due to natural inputs of saline groundwaters and it is unclear whether the increases in V, Ni, Mo and Re are due to natural or anthropogenic inputs to the river. Although it had been claimed that the industrial development of the Athabasca Bituminous Sands (ABS) is a significant source of Ag, Cd, Pb, Sb and Tl to the river, our study failed to find any evidence to support this. Here we provide a first, robust (accurate and precise) description of baseline values for these trace elements in the AR, and suggest that V, Ni, Mo and Re are more valuable tracers for environmental monitoring and source assessment.

Dust is the dominant source of "heavy metals" to peat moss (Sphagnum fuscum) in the bogs of the Athabasca Bituminous Sands region of northern Alberta.

Sphagnum fuscum was collected from twenty-five ombrotrophic (rain-fed) peat bogs surrounding open pit mines and upgrading facilities of Athabasca Bituminous Sands (ABS) in northern Alberta (AB) in order to assess the extent of atmospheric contamination by trace elements. As a control, this moss species was also collected at a bog near Utikuma (UTK) in an undeveloped part of AB and 264km SW of the ABS region. For comparison, this moss was also collected in central AB, in the vicinity of the City of Edmonton which is approximately 500km to the south of the ABS region, from the Wagner Wetland which is 22km W of the City, from Seba Beach (ca. 90km W) and from Elk Island National Park (ca. 45km E). All of the moss samples were digested and trace elements concentrations determined using ICP-SMS at a commercial laboratory, with selected samples also analyzed using instrumental neutron activation analysis at the University of Alberta. The mosses from the ABS region yielded lower concentrations of Ag, As, Bi, Cd, Cu, Pb, Sb, Tl, and Zn compared to the moss from the Edmonton area. Concentrations of Ni and Mo in the mosses were comparable in these two regions, but V was more abundant in the ABS samples. Compared with the surface vegetation of eight peat cores collected in recent years from British Columbia, Ontario, Quebec and New Brunswick, the mean concentrations of Ag, As, Bi, Cd, Cu, Mo, Ni, Pb, Sb, Tl and Zn in the mosses from the ABS region are generally much lower. In fact, the concentrations of these trace elements in the samples from the ABS region are comparable to the corresponding values in forest moss from remote regions of central and northern Norway. Lithophile element concentrations (Ba, Be, Ga, Ge, Li, Sc, Th, Ti, Zr) explain most of the variation in trace metal concentrations in the moss samples. The mean concentrations of Th and Zr are greatest in the moss samples from the ABS region, reflecting dust inputs to the bogs from open pit mines, aggregate quarries, and gravel roads. Linear regressions of V, Ni, and Mo (elements enriched in bitumen) versus Sc (a conservative, lithophile element) show excellent correlations in the mosses from the ABS region, but this is true also of Ag, Pb, Sb and Tl: thus, most of the variation in the trace metal concentrations can be explained simply by the abundance of dust particles on the plants of this region. Unlike the moss samples from the ABS region and from UTK where Pb/Sc ratios resemble those of crustal rocks, the moss samples from the other regions studied yielded much greater Pb/Sc ratios implying significant anthropogenic Pb contributions at these other sites.

Animal density and track counts: understanding the nature of observations based on animal movements.

Counting animals to estimate their population sizes is often essential for their management and conservation. Since practitioners frequently rely on indirect observations of animals, it is important to better understand the relationship between such indirect indices and animal abundance. The Formozov-Malyshev-Pereleshin (FMP) formula provides a theoretical foundation for understanding the relationship between animal track counts and the true density of species. Although this analytical method potentially has universal applicability wherever animals are readily detectable by their tracks, it has long been unique to Russia and remains widely underappreciated. In this paper, we provide a test of the FMP formula by isolating the influence of animal travel path tortuosity (i.e., convolutedness) on track counts. We employed simulations using virtual and empirical data, in addition to a field test comparing FMP estimates with independent estimates from line transect distance sampling. We verify that track counts (total intersections between animals and transects) are determined entirely by density and daily movement distances. Hence, the FMP estimator is theoretically robust against potential biases from specific shapes or patterns of animal movement paths if transects are randomly situated with respect to those movements (i.e., the transects do not influence animals' movements). However, detectability (the detection probability of individual animals) is not determined simply by daily travel distance but also by tortuosity, so ensuring that all intersections with transects are counted regardless of the number of individual animals that made them becomes critical for an accurate density estimate. Additionally, although tortuosity has no bearing on mean track encounter rates, it does affect encounter rate variance and therefore estimate precision. We discuss how these fundamental principles made explicit by the FMP formula have widespread implications for methods of assessing animal abundance that rely on indirect observations.

Factors associated with initiation of chronic renal replacement therapy for patients with kidney failure.

BACKGROUND AND OBJECTIVES: Patients with kidney failure sometimes do not receive chronic renal replacement therapy (RRT), even though this may reduce their life expectancy. This study aimed to identify factors associated with initiation of chronic RRT. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: This cohort study was conducted with Albertans aged >18 years between May 2002 and March 2009, using linked data from the provincial renal programs, clinical laboratories, and provincial health ministry. This study focused on those who developed kidney failure, defined by an estimated GFR (eGFR) <15 ml/min per 1.73 m(2) at last measurement during follow-up, together with prior CKD (eGFR <60 ml/min per 1.73 m(2) at least 90 days earlier). Multivariable Cox proportional hazards models were used to determine factors significantly associated with initiation of chronic RRT. RESULTS: In total, 7901 participants had eGFR <15 ml/min per 1.73 m(2) at last measurement. After adjustment, older participants were less likely to initiate chronic RRT. Remote residence location, dementia, and metastatic cancer also decreased the likelihood of initiating RRT. The cumulative probability of initiating RRT during follow-up was 76.8% for urban-dwelling men aged <50 years without comorbidity, but was only 3.2% among remote-dwelling women aged ≥70 years with dementia and metastatic cancer. In contrast, patients with diabetes and heavy/severe proteinuria were more likely to initiate chronic RRT. CONCLUSIONS: There is substantial variability in the likelihood of RRT initiation for patients with eGFR <15 ml/min per 1.73 m(2). Further studies are needed to delineate factors that influence this outcome.