Correction for ‘Treatment of mine water for the fast removal of zinc and lead by wood ash amended biochar’ by Stuart Cairns et al., Environ. Sci.: Adv., 2022, 1, 506–516, https://doi.org/10.1039/d2va00085g.

Industrial emissions of volatile organic compounds (VOCs) directly impact air quality downwind of facilities and contribute to regional ozone and secondary organic aerosol production. Positive matrix factorization (PMF) is often used to apportion VOCs to their respective sources using measurement data collected at fixed sites, for example air quality monitoring stations. Here, we apply PMF analysis to high time-resolution VOC measurement data collected both while stationary and while moving using a mobile monitoring platform. The stationary monitoring periods facilitated the extraction of representative industrial VOC source profiles while the mobile monitoring periods were critical for the spatial identification of VOC hotspots. Data were collected over five days in a heavily industrialized region of southwestern Ontario containing several refineries, petrochemical production facilities and a chemical waste disposal facility. Factors associated with petroleum, chemical waste and rubber production were identified and ambient mixing ratios of selected aromatic, unsaturated and oxygenated VOCs were apportioned to local and background sources. Fugitive emissions of benzene, highly localized and predominantly associated with storage, were found to be the dominant local contributor to ambient benzene mixing ratios measured while mobile. Toluene and substituted aromatics were predominantly associated with refining and traffic, while methyl ethyl ketone was linked to chemical waste handling. The approach described here facilitates the apportionment of VOCs to their respective local industrial sources at high spatial and temporal resolution. This information can be used to identify problematic source locations and to inform VOC emission abatement strategies.

Peatlands dominate the landscape of the Hudson Bay Lowlands in Ontario, Canada. Recently, mineral deposits of chromium (Cr), nickel (Ni), and copper (Cu) were discovered in the region and anticipated future industrial mining operations have the potential to impact the environment. Lichens and bryophytes are considered excellent biomonitors and indicators of deposition, deriving their nutrients directly from the atmosphere. Trace element concentrations in lichens and bryophytes have not been reported in the Hudson Bay Lowlands. Here, we seek to determine the baseline trace element concentrations of six non-vascular species (Evernia mesomorpha, Bryoria spp., Cladonia stellaris, Cladonia stygia, Sphagnum fuscum, and Sphagnum capillifolium) common to the region, explore linear relationships of trace elements with iron (Fe) as a signature of particulates with geogenic origin, and calculate trace element enrichment factors. Thalli, foliage, and peat (0–30 cm) were collected from 55 locations between 2013 and 2018 and analyzed for trace elements. Thalli and foliar concentrations are among the lowest reported in the broader literature and differ substantially from peat. Fe concentrations were significantly correlated (Pearson’s r ≥ 0.8) with aluminum (Al), titanium (Ti), and vanadium (V) in all six species. Enrichment factors show some anthropogenic deposition effects non-vascular organism chemistry. Most trace element concentrations in lichens and bryophytes are indicative of long-range atmospheric transport of dust, but some is attributed to industry, with only minimal inclusions from the local area. Epiphytic lichens are well suited for ongoing atmospheric biomonitoring as industrialization commences.

Large mineral deposits have been discovered in Ontario's Far North and are being considered for further development. Particulate matter and trace elements can be emitted from potential mining activities and these air pollutants are associated with health risks and harmful to the sensitive ecosystem. An air monitoring station, powered by solar panels and a wind turbine, was established in this near-pristine area to monitor baseline levels of fine particulate matter (PM2.5) and trace elements downwind of a proposed mine site. Levels of PM2.5 and trace elements observed from 2015 to 2018 were much lower than measurements observed in southern Ontario, suggesting minimal influence of primary emissions in the study area. One episodic PM2.5 event in July 2015 was attributable to wildfire emissions in northern Ontario. Only 8 out of the 31 target elements were detected in 25% or more of the samples. Good correlations among As, Se, Pb, and Sb, between Mn and Fe, as well as between Ce and La indicated they originated from long-range atmospheric transport from the south. Ontario's Ambient Air Quality Criteria were not exceeded for any target air pollutants. Four years of air measurements filled the data gap of baseline information in this near-pristine study area and can be used to assess impacts of potential mining activities in the future. Field operations during this study period indicated that the battery-powered air instruments and meteorological sensors worked well in the harsh environment of Ontario's Far North even in cold winter months. The field experiences gained in this study can be applied to future air monitoring activities in harsh environments where no direct power supply is available and site access is limited.

Passive samplers have proven to be effective for continuous monitoring of volatile organic compounds (VOCs) in ambient air in remote, urban and industrial environments. Thermal desorption tubes fitted with endcaps that facilitate passive uptake through diffusion are now routinely used for monitoring fugitive benzene emissions from refineries and petrochemical facilities across North America (EPA Method 325A/B). However, deployment periods of 14 days are typically employed to minimize the risk of poor retention, requiring 26 deployments per year to return an annual average concentration for comparison with chronic exposure health-based standards. Here, we explore extending the deployment duration of these passive samplers to one, two and three months by limiting VOC uptake rates using an alternative diffusive endcap featuring a smaller cross-sectional area. Field testing was performed beside a major highway during two separate three-month campaigns. Uptake rates for benzene, toluene, ethylbenzene and xylenes (BTEX) were observed to remain linear for deployments of up to three months when using the low-uptake endcaps. Application of the low-uptake endcaps and the uptake rates determined here will enable annual average concentrations of BTEX to be calculated using only four tube deployments per year. The cost savings associated with this decreased deployment frequency will facilitate increased spatial resolution during future exposure assessment studies. The stability of selected air toxics within the tubes was also assessed and the results suggest that while aromatic VOCs are stable for storage times of at least 70 days, chloroform and trichloroethylene begin to degrade within two weeks of sampling.

Poly- and perfluoroalkyl substances (PFAS) have become ubiquitous contaminants in the environment. Contamination of the terrestrial ecosystem can occur from the release of aqueous film forming foams (AFFF) used in firefighting operations. Following soil contamination with AFFF, studies report root uptake and translocation of PFAS to other plant organs, typically favouring the short chain moiety. This body of experimental work often focuses on edible organs and generally lacks entire PFAS budgets. Here, we calculate short chain (<= 6 carbons) and long chain (>= 6 or >= 7 carbons) PFAS concentrations and respective budgets for terrestrial multimedia mesocosms (plants, soil and lysimeter) of three common agricultural plants (tomato, lettuce and beet) following irrigation with low level PFAS (<1 mu g L-1) contaminated river water (short chain: 167 ng L-1; long chain 526 ng L-1). Total net recoveries were strong, ranging between 91% and 118% of added PFAS across all media. While soil was the largest receptor of PFAS in general (-70% and 115%), there was considerable mobility to various media, including vegetation (-3% and 20%) and leachate (-1%). Translocation of short chain PFAS to tomato flowers resulted with biomagnified concentrations (maximus >4000 ng g(-1)) and accounted for 1.4% of PFAS additions. While smaller tomato fruits had higher concentrations of short chain PFAS, larger fruit had more total PFAS mass. This work provides a detailed description of the fate of short and long chain PFAS when added to relatively uncontaminated terrestrial agricultural systems. We show low-level PFAS concentrations from real-world irrigation sources can affect various receptors across the multimedia landscape. This is most evident in tomato flowers and fruit where biomagnification and high total masses of short chain PFAS occurred which could have implications for pollinators and consumption, respectively. Crown Copyright (C) 2021 Published by Elsevier Ltd. All rights reserved.

Accurate, continuous long-term measurements of aromatic volatile organic compounds with known health impacts are needed for comprehensive assessments of air quality in the vicinity of industrial and vehicular emission sources. Historically, evacuated canister sampling and on-line gas chromatography (GC) have been the most popular approaches applied by government institutions in North America to measure benzene, toluene, ethylbenzene and xylenes (BTEX) in ambient air. Canister sampling is labour-intensive and typically does not provide the continuous data needed for epidemiological studies, while on-line GCs are costly and require shelter and power. In this work, the accuracy and suitability of three techniques for generating long-term ambient BTEX datasets are assessed. The first is a passive sampling method involving sorbent-packed thermal desorption tubes, the second is an on-line miniature gas chromatograph (miniGC) coupled with a photoionization detector (PID) and the third is a more traditional on-line gas chromatograph coupled with a flame ionization detector (GC-FID). These three techniques were deployed at an air quality monitoring station located adjacent to a busy highway for six weeks in summer 2018 to compare method performance and accuracy. Ambient mean concentrations of BTEX determined from the three methods for the entire study period were found to agree within 7% for benzene and within 30% for the other species. Interestingly, a temperature dependent positive bias previously identified for 14-day passive tube sampling for ethylbenzene and xylenes under cold wintertime conditions was found to be negligible under summertime conditions.

It remains uncertain how the net ecosystem CO2 exchange (NEE) of diverse peatlands will respond to warming. Here we compare five years of eddy covariance measurements of NEE and estimates of gross primary productivity and ecosystem respiration between a fen dominated by deciduous vegetation and an adjacent bog with evergreen vegetation in the Canadian Hudson Bay Lowlands. At the bog, daily net CO2 uptake lasted from snowmelt to snow cover onset, while at the fen, net CO2 uptake was delayed in spring and ended earlier in fall. Greater midsummer net CO2 uptake at the fen compensated for shoulder season net CO2 losses resulting in similar annual NEE at the two sites (fen: −52 ± 16 g C m−2, bog: −80 ± 14 g C m−2). Observations of a satellite‐based productivity index also suggest lower shoulder season and higher peak vegetation productivity at these deciduous versus evergreen plant‐dominated peatlands. The response of NEE to warmer weather differed between sites. Warming during the shoulder seasons increased net CO2 uptake at the evergreen plant‐dominated bog, while it increased net CO2 losses at the fen where deciduous leaves had not yet emerged or had senesced. In contrast, warmer weather during the peak growing season appeared to reduce net CO2 uptake more at the bog than the fen resulting from both increasing ecosystem respiration and decreasing gross primary productivity. In the short term, warming will likely decrease annual net CO2 uptake of these and similar peatlands, although the magnitude will depend on factors including vegetation dynamics and seasonality of warming.

2 Monitoring of Volatile Organic Compounds in Urban Environments 3 Robert M. Healy,*,† Julie Bennett,† Jonathan M. Wang,† Nicholas S. Karellas,† Colman Wong,† 4 Aaron Todd,† Uwayemi Sofowote,† Yushan Su,† Linda Di Federico,† Anthony Munoz,† 5 Jean-Pierre Charland,‡ Dennis Herod,‡ May Siu,‡ and Luc White‡ 6 †Environmental Monitoring and Reporting Branch, Ontario Ministry of the Environment, Conservation and Parks, Toronto, Ontario 7 M9P 3V6, Canada 8 ‡Air Quality Research Division, Environment and Climate Change, Ottawa, Ontario K4M 1B4, Canada

Prior to 2012 street sediment from the Greater Toronto Area was being managed by a local authority and provided to rural landowners under the assumption it was clean fill. The aim of this study was to characterise the chemical and physical composition of that street sediment applied to an agricultural field in southwestern Ontario, Canada and determine if contaminants had migrated to native soil. Soil was sampled from an impact and a background location during the fall of 2016 at four soil depths (0-10, 10-20, 20-30 and 30-40 cm below the surface) to characterise texture, pH, organic content, recoverable metals and total polycyclic aromatic hydrocarbons (PAHs). Textural analysis revealed street sediment was dominated by very coarse and coarse sand which differed from the native silty clay loam and extended to 30 cm below the surface. Some PAHs, including benzo(a)pyrene (1.29 μg g-1) exceeded the typical regional background concentrations. A distinct pattern of high molecular mass PAHs in the native soil below street sediments suggests that PAHs have migrated to native soil. To our knowledge this is the first study to report PAH concentrations in street sediment in Ontario and to show their potential movement and introduction to native soil. Future studies should focus on transport mechanisms and understanding movement of PAHs in native coarse textured soil.

Environmental Protection Agency Method 325 was developed for continuous passive monitoring of volatile organic compounds (VOCs), particularly benzene, at petroleum refinery fencelines. In this work, a modified version of the method was evaluated at an Ontario near-road research station in winter to assess its suitability for urban air quality monitoring. Samples were collected at 24 hour and 14 day resolution to investigate accuracy for different exposure times. Tubes were analyzed by thermal desorption-gas chromatography-mass spectrometry, and 11 VOCs were quantified, including aromatic air toxics. The same VOCs were simultaneously monitored using traditional canister sampling for comparison, and a subset of four were also monitored using a novel miniature gas chromatograph. Good agreement (within 10%) was observed between the 14 day passive tube samples and the canister samples for benzene. However, field-calibrated uptake rates were required to correct passive tube concentrations for less volatile aromatics. Passive tube deployment and analysis is inexpensive; sampling does not require power, and accurate measurements of benzene are demonstrated here for an urban environment. The method is expected to be advantageous for the generation of long-term continuous benzene datasets suitable for epidemiological research with greater spatial coverage than is currently available using traditional monitoring techniques.

Fluoride is considered one of the most phytotoxic elements to plants, and indicative fluoride injury has been associated over a wide range of foliar fluoride concentrations. The aim of this study was to determine the probability of indicative foliar fluoride injury based on Acer sp. foliar fluoride concentrations using a logistic regression model. Foliage from Acer nedundo, Acer saccharinum, Acer saccharum and Acer platanoides was collected along a distance gradient from three separate brick manufacturing facilities in southern Ontario as part of a long-term monitoring programme between 1995 and 2014. Hydrogen fluoride is the major emission source associated with the manufacturing facilities resulting with highly elevated foliar fluoride close to the facilities and decreasing with distance. Consistent with other studies, indicative fluoride injury was observed over a wide range of foliar concentrations (9.9–480.0 μg F− g−1). The logistic regression model was statistically significant for the Acer sp. group, A. negundo and A. saccharinum; consequently, A. negundo being the most sensitive species among the group. In addition, A. saccharum and A. platanoides were not statistically significant within the model. We are unaware of published foliar fluoride values for Acer sp. within Canada, and this research provides policy maker and scientist with probabilities of indicative foliar injury for common urban Acer sp. trees that can help guide decisions about emissions controls. Further research should focus on mechanisms driving indicative fluoride injury over wide ranging foliar fluoride concentrations and help determine foliar fluoride thresholds for damage.

The reliable analysis of highly toxic hexavalent chromium, Cr(VI), at ultra-trace levels remains challenging, given its easy conversion to non-toxic trivalent chromium. This work demonstrates a novel analytical method to quantify Cr(VI) at low ng L−1 concentration levels in environmental water samples by using speciated isotope dilution (SID) analysis and double-spiking with Cr(III) and Cr(VI) enriched for different isotopes. Ion chromatography tandem mass spectrometry (IC-MS/MS) was used for the analysis of Cr(VI) as HCrO4− → CrO3−. Whereas the classical linear multipoint calibration (MPC) curve approach obtained a method detection limit (MDL) of 7 ng L−1 Cr(VI), the modified SID-MS method adapted from U. S. EPA 6800 allowed for the quantification of Cr(VI) with an MDL of 2 ng L−1 and provided results corrected for Cr(VI) loss occurred after sample collection. The adapted SID-MS approach proved to yield more accurate and precise results than the MPC method, allowed for compensation of Cr(VI) reduction during sample transportation and storage while eliminating the need for frequent external calibration. The developed method is a complementary tool to routinely used inductively-coupled plasma (ICP) MS and circumvents typically experienced interferences.

Surface water concentrations of the acid herbicides 2,4-D, dicamba and mecoprop were measured in ten urban Ontario streams before (2003–2008) and after (2009–2012) a ban on the sale and use of pesticides for cosmetic (non-essential) purposes. Frequencies of detection (2003–2012) were 98%, 96% and nearly 100%, respectively for 2,4-D, dicamba and mecoprop. Concentrations were typically in the ng L−1 range, although periodic spikes in the µg L−1 range were observed. Concentrations in a majority of the study streams decreased significantly following the cosmetic pesticides ban. Concentrations decreased from 16% to 92% depending on the stream and herbicide. The presence of these herbicides in urban streams was likely a result of urban applications. Concentrations were significantly related to population density or urban land cover, and the relative proportion of the three herbicides observed in urban stream water approximated the ratios found in pesticide products formulated for urban use. Longer-term trends indicate that decreases in stream water herbicide concentrations may have preceded the ban and may be related to increased public awareness of pesticide issues and voluntary reductions in urban pesticide use.

Warm season (May–October) chloride concentrations were assessed in stream habitats of freshwater mussel species at risk in southern Ontario, Canada. Significant increases in concentrations were observed at 96% of 24 long-term (1975–2009) monitoring sites. Concentrations were described as a function of road density indicating an anthropogenic source of chloride. Linear regression showed that 36% of the variation of concentrations was explained by road salt use by the provincial transportation ministry. Results suggest that long-term road salt use and retention is contributing to a gradual increase in baseline chloride concentrations in at risk mussel habitats. Exposure of sensitive mussel larvae (glochidia) to increasing chloride concentrations may affect recruitment to at risk mussel populations.

Concerns regarding the impacts of pesticides on aquatic species and drinking water sources have increased demands on water quality monitoring programs; however the costs of sample analysis can be prohibitive. In this study we investigated enzyme-linked immunosorbent assay (ELISA) as a cost-effective, high through-put method for measuring pesticide concentrations in surface waters. Seven hundred and thirty-nine samples from 158 locations throughout Ontario were analysed for atrazine and metolachlor from April to October 2007. Concentrations ranged from <0.1 to 3.91 μg L−1 (median = 0.12 μg L−1) for atrazine and from <0.1 to 1.83 μg L−1 (median = 0.09 μg L−1) for metolachlor. Peak concentrations occurred in late spring/early summer, in rural agricultural locations, and decreased over the remainder of the growing season for both herbicides. About 3% of the samples that had ELISA results occurring above the limit of quantification (0.10 μg L−1) were evaluated against gas chromatography-mass spectrometry (GC–MS). Linear regression analysis revealed a R2 value of 0.88 and 0.39, for atrazine and metolachlor, respectively. ELISA tended to overestimate concentrations for atrazine and metolachlor, most likely because the ELISA kits also detect their metabolites. Atrazine data suggest that ELISA may be used complementary with GC–MS analysis to enhance the spatial and temporal resolution of a water quality monitoring study. The commercially available metolachlor ELISA kit requires further investigation. ELISA may be used to detect atrazine and metolachlor in surface water samples, but it is not recommended as a quantitative replacement for traditional analytical methods.

Concerns have been raised in the scientific community regarding the environmental implications of a dramatic increase in corn-based ethanol production and associated increases in pesticide use. The use of glyphosate, a broad-spectrum herbicide, for corn production has increased considerably in recent years in Canada and the United States. The cost of measuring concentrations of organic contaminants in the environment using traditional wet chemistry methods can be prohibitive; especiallywhen large numbers of samples are required to quantify the spatial and temporal variability in contaminant concentrations. The goal of our study was to evaluate a cost-effective method to measure glyphosate concentrations in surface waters. The reliability of enzyme-linked immunosorbent assay (ELISA) results was evaluated against liquid chromatography tandem mass spectrometry, and linear regression results for 30 water samples from urban watersheds revealed a strong relationship (R2 = 0.88). These results suggest that ELISA methods, used in conjunction with traditional methods, represent a cost-effective approach to enhance the spatial and temporal resolution of a water quality monitoring study. Additionally, we measured a total of 739 surface water samples from over 150 sampling locations throughout Ontario using ELISA from April to October 2007. Concentrations exceeded the method detection limit of 0.1 microg/L in 33% of the samples, with a maximum concentration of 12.0 microg/L. Glyphosate showed a bimodal temporal distribution with peak concentrations occurring in late spring/early summer and fall, and did not exceed the Canadian Council of Ministers of the Environment (CCME) guideline for the protection of aquatic life (65 microg/L) in any of the samples.

Hydrologic dynamics are examined across a range of spatial scales in a 78km2 wetland-dominated drainage basin in south central Ontario, Canada. The basin typically receives ∼800mm of precipitation annually (∼20% as snowfall), although precipitation during the 1998 study year was 28% greater due to increased snowfall. Water table elevation, outlet stream discharge and local groundwater flow patterns were monitored in a representative interdrumlin headwater wetland sub-basin. A rising water table during snowmelt sustained surface saturation in the wetland and at the slope–wetland interface, and saturation overland flow generated the bulk of annual runoff. Despite considerable till thickness on the drumlin slopes, minor groundwater fluxes from slopes to the wetland could not maintain near-surface water tables. These fell below the ground surface shortly after snowmelt and led to cessation of stream flow. Vertical water movement in response to precipitation, evapotranspiration and recharge of deeper groundwater was more important than lateral groundwater fluxes in explaining the wetland's hydrologic behavior. Spatial and temporal dynamics of variable runoff source areas in the basin were examined based on stream flow response from 15 headwater wetland sub-basins. Peak basin stream flow resulted from delivery of sub-basins runoff to a spatially linked drainage network during spring snowmelt. However, sub-basins became decoupled from the basin outlet as summer progressed, and their runoff during significant summer and fall storms entered ephemeral stream channels where most was lost to evaporation and infiltration or held in surface storage. Nevertheless, hydrologic connectivity was more protracted in 1998 than would be likely during a ‘normal’ precipitation year. Hydrologic processes in this drumlinized landscape are inconsistent with some aspects of the variable source area concept of stream flow generation, and caution should be used when extrapolating knowledge and models from well-integrated drainage networks to wetland-dominated basins such as that examined here.