Short and long-term phytoremediation capacity of aquatic plants in Cu-polluted environments.

Freshwater ecosystems face numerous threats from human populations, including heavy metal contamination. Phytoremediation, the use of plants to remediate contaminated soils and sediments, is an effective and low-cost means of removing chemical contaminants, including heavy metals, from polluted environments. However, key questions remain unanswered in the application of this technology in aquatic environments, such as the long-term fate of pollutants following plant uptake. In this study, using two common wetland plant species (duckweed and tape grass), we first examined the capacity of plants to remove copper (Cu) from polluted water. Next, we evaluated the leaching potential of plant tissues following decomposition and how it is affected by a simulated freeze-thaw cycle. Using phytoremediated water and leachates from senesced plants we assessed phytoremediation success and Cu leaching potential by conducting standard toxicity assays using pond snails (Physa acuta), a species with known Cu sensitivity. We found that duckweed outperformed tape grass as a phytoremediator at low Cu concentrations. In addition, for plants grown in low concentrations of Cu, leaching from decaying plant material did not negatively impact snail survival, while at high concentrations of Cu, leaching did result in toxicity. Lastly, we found that a simulated freeze-thaw cycle increased the release of Cu from plant tissue in the presence of high Cu concentrations only, resulting in reduced snail survival. Our results indicate that in moderately Cu-polluted environments, some aquatic plants can remove contaminants without a long-term risk of leaching. In contrast, phytoremediation in highly polluted environments will likely require removal of plant tissue to prevent leaching of previously accumulated metals. Land managers must not only consider plant species and degree of contamination, but also geographic location, as freeze-thaw cycles may enhance plant decomposition and increase the likelihood of contaminant leaching following phytoremediation efforts in aquatic ecosystems.

Use of an epiphytic lichen and a novel geostatistical approach to evaluate spatial and temporal changes in atmospheric deposition in the Athabasca Oil Sands Region, Alberta, Canada.

Temporal and spatial atmospheric deposition trends of elements to the boreal forest surrounding bitumen production operations in the Athabasca Oil Sands Region (AOSR), Alberta, Canada were investigated as part of a long-term lichen bioindicator study. The study focused on eight elements (sulfur, nitrogen, aluminum, calcium, iron, nickel, strontium, vanadium) that were previously identified as tracers for the major oil sand production sources. Samples of the in situ epiphytic lichen Hypogymnia physodes were collected in 2002, 2004, 2008, 2011, 2014, and 2017 within a ~150 km radius from the center of surface oil sand production operations in the AOSR. Site-specific time series analysis conducted at eight jack pine upland sites that were repeatedly sampled generally showed significant trends of increasing lichen concentrations for fugitive dust linked elements, particularly at near-field (<25 km from a major oil sands production operation) sample locations. Multiple regional scale geostatistical models were developed and evaluated to characterize broad-scale changes in atmospheric deposition based on changes in H. physodes elemental concentrations between 2008 and 2014. Empirical Bayesian kriging and cokriging lichen element concentrations with oil sands mining, bitumen upgrading, coke materials handling, and limestone quarry/crushing influence variables produced spatial interpolation estimates with the lowest validation errors. Gridded zonal mean lichen element concentrations were calculated for the two comprehensive sampling years (2008, 2014) and evaluated for spatial and temporal change. Lichen sulfur concentrations significantly increased in every grid cell within the domain with the largest increases (44-88%) in the central valley in close proximity to the major surface oil sand production operations, while a minor nitrogen concentration decrease (-20%) in a single grid cell was observed. The areal extent of fugitive dust element deposition generally increased with significantly higher deposition to lichens restricted to the outer grids of the enhanced deposition field, reflecting new and expanding surface mining activity.

Source apportionment of an epiphytic lichen biomonitor to elucidate the sources and spatial distribution of polycyclic aromatic hydrocarbons in the Athabasca Oil Sands Region, Alberta, Canada.

The sources and spatial distribution of polycyclic aromatic hydrocarbons (PAHs) atmospheric deposition in the boreal forests surrounding bitumen production operations in the Athabasca Oil Sands Region (AOSR), Alberta, Canada were investigated as part of a 2014 passive in-situ bioindicator source apportionment study. Epiphytic lichen species Hypogymnia physodes samples (n = 127) were collected within a 150 km radius of the main surface oil sand production operations and analyzed for total sulfur, total nitrogen, forty-three elements, twenty-two PAHs, ten groups of C1-C2-alkyl PAHs and dibenzothiophenes (polycyclic aromatic compounds; PACs), five C1- and C2-alkyldibenzothiophenes, and retene. The ΣPAH + PAC in H. physodes ranged from 54 to 2778 ng g-1 with a median concentration of 317 ng g-1. Source apportionment modeling found an eight-factor solution that explained 99% of the measured ΣPAH + PAC lichen concentrations from four anthropogenic oil sands production sources (Petroleum Coke, Haul Road Dust, Stack Emissions, Raw Oil Sand), two local/regional sources (Biomass Combustion, Mobile Source), and two lichen biogeochemical factors. Petroleum Coke and Raw Oil Sand dust were identified as the major contributing sources of ΣPAH + PAC in the AOSR. These two sources accounted for 63% (43.2 µg g-1) of ΣPAH + PAC deposition to the entire study domain. Of this overall 43.2 µg g-1 contribution, approximately 90% (39.9 µg g-1) ΣPAH + PAC was deposited within 25 km of the closest oil sand production facility. Regional sources (Biomass Combustion and Mobile Sources) accounted for 19% of ΣPAH + PAC deposition to the entire study domain, of which 46% was deposited near-field to oil sand production operations. Source identification was improved over a prior lichen-based study in the AOSR through incorporation of PAH and PAC analytes in addition to inorganic analytes.

Using Pb isotope ratios of particulate matter and epiphytic lichens from the Athabasca Oil Sands Region in Alberta, Canada to quantify local, regional, and global Pb source contributions.

Ambient air particulate matter (PM) was collected at the Wood Buffalo Environmental Association Bertha Ganter Fort McKay monitoring station in the Athabasca Oil Sand Region (AOSR) in Alberta, Canada from February 2010 to July 2011 as part of an air quality source assessment study. Daily 24-hour duration fine (PM2.5) and coarse (PM10-2.5) PM was collected using a sequential dichotomous sampler. 100 pairs of PM2.5 and PM10-2.5 were selected for lead (Pb) concentration and isotope analysis. Pb isotope and concentration results from 250 epiphytic lichen samples collected as far as 160 km from surface mining operations in 2008, 2011, and 2014 were analyzed to examine longer term spatial variations in Pb source contributions. A key finding was recognition of thorogenic 208Pb from eastern Asia in the springtime in the PM2.5 in 2010 and 2011. 206Pb/207Pb and 208Pb/207Pb isotope ratios were used in a three-component mixing model to quantify local, regional, and global Pb sources in the PM and lichen data sets. 47 ±â€¯3% of the Pb in the PM2.5 at AMS-1 was attributed to sources from eastern Asia. Combined results from PM10-2.5 and PM2.5 indicate PM2.5 Pb contributions from eastern Asia (34%) exceed local AOSR sources of PM2.5 Pb (20%), western Canada sources of PM2.5 Pb (19%), and PM10-2.5 Pb from fugitive dust including oil sands (14%), tailings (10%), and haul roads (3%). The lichen analysis indicates regional sources contribute 46% of the Pb, local sources 32%, and global sources 22% over the 2008-2014 timeframe. Local sources dominate atmospheric Pb deposition to lichens at near field sites (0-30 km from mining operations) whereas regional Pb sources are prevalent at distal sites (30-160 km). The Pb isotope methodology successfully quantified trans-Pacific transport of Pb to the AOSR superimposed over the aerosol footprint of the world's largest concentration of bitumen mining and upgrading facilities.

Source apportionment of ambient fine and coarse particulate matter polycyclic aromatic hydrocarbons at the Bertha Ganter-Fort McKay community site in the Oil Sands Region of Alberta, Canada.

A comprehensive filter-based particulate matter polycyclic aromatic hydrocarbon (PAH) source apportionment study was conducted at the Wood Buffalo Environmental Association Bertha Ganter-Fort McKay (BGFM) community monitoring station from 2014 to 2015 to quantify ambient concentrations and identify major sources. The BGFM station is located in close proximity to several surface oil sands production facilities and was previously found to be impacted by their air emissions. 24-hour integrated PM2.5 and PM10-2.5 samples were collected on a 1-in-3-day schedule yielding 108 complete organic/inorganic filter sets for source apportionment modeling. During the study period PM2.5 averaged 8.6 ±â€¯11.8 µg m-3 (mean ±â€¯standard deviation), and PM10-2.5 averaged 8.5 ±â€¯9.5 µg m-3. Wind regression analysis indicated that the oil sands production facilities were significant sources of PM2.5 mass and black carbon (BC), and that wildland fires were a significant source of the highest PM2.5 (>10 µg m-3) and BC events. A six-factor positive matrix factorization (PMF) model solution explained 95% of the measured PM2.5 and 78% of the measured ΣPAH. Five sources significantly contributed to PM2.5 including: Biomass Combustion (3.57 µg m-3; 40%); Fugitive Dust (1.86 µg m-3; 28%); Upgrader Stack Emissions (1.44 µg m-3; 21%); Petrogenic PAH (1.20 µg m-3; 18%); and Transported Aerosol (0.43 µg m-3 and 6%). However, the analysis indicated that only the pyrogenic PAH source factor significantly contributed (78%) to the measured ΣPAH. A five-factor PMF model dominated by fugitive dust sources explained 98% of PM10-2.5 mass and 86% of the ΣPAH. The predominant sources of PM10-2.5 mass were (i) Haul Road Dust (4.82 µg m-3; 53%), (ii) Mixed Fugitive Dust (2.89 µg m-3; 32%), (iii) Fugitive Oil Sand (0.88 µg m-3; 10%), Mobile Sources (0.23 µg m-3; 2%), and Organic Aerosol (0.06 µg m-3; 1%). Only the Organic Aerosol source significantly contributed (86%) to the measured ΣPAH.

Differential accumulation of PAHs, elements, and Pb isotopes by five lichen species from the Athabasca Oil Sands Region in Alberta, Canada.

A 2014 case study investigated the relative accumulation efficiency of polycyclic aromatic hydrocarbons (PAHs), total sulfur (S), total nitrogen (N), major and minor elements and Pb isotopes in five common lichen species at three boreal forest sites in the Athabasca Oil Sands Region (AOSR) in northeastern Alberta, Canada to identify the optimum lichen species for future biomonitoring. Differences in concentrations of PAHs, multiple elements, and Pb isotopes in fruticose (Bryoria furcellata, Cladina mitis, Evernia mesomorpha) and foliose (Hypogymnia physodes and Tuckermannopsis americana) lichens were found along a 100 km distance gradient from the primary oil sands operations. Integration of insights from emission source samples and oil sands mineralogy in consort with aerosol collection indicates incorporation of more fine particulate matter (PM) into foliose than fruticose lichen biomass. Contrasting PAH with element concentrations allowed lichen species specific accumulation patterns to be identified. The ability of lichen species to incorporate different amounts of gas phase (S and N), petrogenic (V, Ni, Mo), clay (low Si/Al and more rare earth elements), and sand (higher Si/Al and Ti) components from the oil sand operations reflects aerosol particle size and lichen physiology differences that translate into differences in PM transport distances and lichen accumulation efficiencies. Based on these findings Hypogymnia physodes is recommended for future PAH biomonitoring and source attribution studies.

Source apportionment of ambient fine and coarse particulate matter at the Fort McKay community site, in the Athabasca Oil Sands Region, Alberta, Canada.

An ambient air particulate matter sampling study was conducted at the Wood Buffalo Environmental Association (WBEA) AMS-1 Fort McKay monitoring station in the Athabasca Oil Sand Region (AOSR) in Alberta, Canada from February 2010 to July 2011. Daily 24h integrated fine (PM2.5) and coarse (PM10-2.5) particulate matter was collected using a sequential dichotomous sampler. Over the duration of the study, 392 valid daily dichotomous PM2.5 and PM10-2.5 sample pairs were collected with concentrations of 6.8±12.9µgm-3 (mean±standard deviation) and 6.9±5.9µgm-3, respectively. A subset of 100 filter pairs was selected for element analysis by energy dispersive X-ray fluorescence and dynamic reaction cell inductively coupled plasma mass spectrometry. Application of the U.S. EPA positive matrix factorization (PMF) receptor model to the study data matrix resolved five PM2.5 sources explaining 96% of the mass including oil sands upgrading (32%), fugitive dust (26%), biomass combustion (25%), long-range Asian transport lead source (9%), and winter road salt (4%). An analysis of historical PM2.5 data at this site shows that the impact of smoke from wildland fires was particularly high during the summer of 2011. PMF resolved six PM10-2.5 sources explaining 99% of the mass including fugitive haul road dust (40%), fugitive oil sand (27%), a mixed source fugitive dust (16%), biomass combustion (12%), mobile source (3%), and a local copper factor (1%). Results support the conclusion of a previous epiphytic lichen biomonitor study that near-field atmospheric deposition in the AOSR is dominated by coarse fraction fugitive dust from bitumen mining and upgrading operations, and suggest that fugitive dust abatement strategies targeting the three major sources of PM10-2.5 (e.g., oil sand mining, haul roads, bulk material stockpiles) would significantly reduce near-field atmospheric deposition gradients in the AOSR and reduce ambient PM concentrations in the Fort McKay community.

Coupling meteorology, metal concentrations, and Pb isotopes for source attribution in archived precipitation samples.

A technique that couples lead (Pb) isotopes and multi-element concentrations with meteorological analysis was used to assess source contributions to precipitation samples at the Bondville, Illinois USA National Trends Network (NTN) site. Precipitation samples collected over a 16month period (July 1994-October 1995) at Bondville were parsed into six unique meteorological flow regimes using a minimum variance clustering technique on back trajectory endpoints. Pb isotope ratios and multi-element concentrations were measured using high resolution inductively coupled plasma-sector field mass spectrometry (ICP-SFMS) on the archived precipitation samples. Bondville is located in central Illinois, ~250km downwind from smelters in southeast Missouri. The Mississippi Valley Type ore deposits in Missouri provided a unique multi-element and Pb isotope fingerprint for smelter emissions which could be contrasted to industrial emissions from the Chicago and Indianapolis urban areas (~125km north and east, of Bondville respectively) and regional emissions from electric utility facilities. Differences in Pb isotopes and element concentrations in precipitation corresponded to flow regime. Industrial sources from urban areas, and thorogenic Pb from coal use, could be differentiated from smelter emissions from Missouri by coupling Pb isotopes with variations in element ratios and relative mass factors. Using a three endmember mixing model based on Pb isotope ratio differences, industrial processes in urban airsheds contributed 56±19%, smelters in southeast Missouri 26±13%, and coal combustion 18±7%, of the Pb in precipitation collected in Bondville in the mid-1990s.