Particulate Trace Elements Research Articles

Technical note: Determining chemical composition of atmospheric single particles by a standard-free mass calibration algorithm

Abstract. The chemical composition of individual particles can be revealed by single-particle mass spectrometers (SPMSs). With higher accuracy in the ratio of mass to charge (m/z), more detailed chemical information could be obtained. In SPMSs, the conventional standard-based calibration methods (internal/external) are constrained by the inhomogeneity of ionization lasers and the finite focusing ability of the inlet system, etc.; therefore, the mass accuracy is restricted. In this study, we obtained the detailed and reliable chemical composition of single particles utilizing a standard-free mass calibration algorithm. In the algorithm, the characteristic distributions of hundreds of ions were concluded and collected in a database denoted as prototype. Each single-particle mass spectrum was initially calibrated by a function with specific coefficients. The range of coefficients was constrained by the magnitude of mass deviation to a finite vector space. To find the optimal coefficient vector, the conformity of each initially calibrated spectrum to the prototype dataset was assessed. The optimum calibrated spectrum was obtained with maximum conformity. For more than 98 % ambient particles, a 20-fold improvement in mass accuracy, from ∼ 10 000 ppm (integer) to ∼ 500 ppm (two decimal places), was achieved. The improved mass accuracy validated the determination of adjacent ions with a m/z difference ∼ 0.05 Th. Furthermore, atmospheric particulate trace elements that were poorly studied before are specified. The obtained detailed single-particle-level chemical information could help explain the source apportionment, reaction mechanism, and mixing state of atmospheric particles.

Size distribution and source-specific risks of atmospheric elements in Dalian, a coastal city in north China

Trace elements in particles play an essential role in particle-related health and environmental effects and were recognized as primary source tracers. An understanding of the size-segregated elemental composition is critical for accurate source attribution and risk evaluation. The present study investigated the characteristics of 28 elements in the size-fractioned particles of a coastal megacity in north China. The size distribution of element concentration posed bimodal peak mode, and the proportion of most trace elements tended to increase with the decreasing particle size, especially toxic metals like Hg, Ga, Tl, As, Pb, Se, and Cd. Source attribution based on the size-segregated concentrations was conducted by positive matrix factorization. Natural sources such as crust and sea spray aerosol dominated the trace element concentration in the large particles, while anthropogenic sources such as traffic, biomass, coal combustion, and industry contributed the majority in the fine particles. The source-specific exposure risk calculation based on the size-segregated dataset showed a noncarcinogenic risk (HQ) of 6.62 for children, mainly contributed by Tl and As from biomass burning, petrochemical refining, and coal combustion. Compared with larger particles, the finer particles generated a higher HQ and carcinogenic risk, especially particles smaller than 0.49 μm. Fine particles primarily emitted from the petrochemical industry and coal combustion brought out the largest HQ, while fine particles from vehicle traffic and the petrochemical industry contributed the largest carcinogenic risk. Transport of sea spray aerosol contributed a considerable amount of the carcinogenic risk in the coastal urban area.

Monitoring For Elemental Composition Of Particulate Matter Deposited In Snow Cover Around Coal-Fired Thermal Power Plant (Karaganda, Central Kazakhstan).

Studies on thermal power plant areas with respect to chemical composition of particulate matter deposited in snow cover are limited. This study aims to monitor (2014–2022) particulate load and trace elements associated with the particulate matter distributed around (0.5-4.5 km) the coal-fired thermal power plant in Karaganda. In this study, snow cover was used as an effective scavenger of atmospheric pollutants. Using instrumental neutron activation analysis and atomic absorption spectrometry, the content of 26 elements and Hg, respectively, was determined in the particulate phase of snow. The results showed that particulate load varied from 26 to 1751, with mean of 427 and a background of 47 mg m-2 d-1. Anthropogenic impact caused a significant increase in content of U, Hg, Ta, Zn, Na, Cr, Co, Sr, Rb, Cs, Sc, Ca, Fe, Nd, Ba (2–30 times) in the samples compared to the background. Metal-bearing phases of Zn, Ba, As, U-Ta-Nb were detected through scanning electron microscope. The highest levels of particulate load (169–1032 mg m-2 d-1) and element contents in the samples were localized up to 0.7 km from the thermal power plant. The changes of particulate load and element composition of snow deposits during the monitoring period were connected with temperature, modernization of dust-collecting equipment, composition of coal and fly ash, long-range transport of emissions from other industries. The element content and metal-bearing phases in the particulate phase of snow can be used as markers for identifying emission sources from coal combustion.

An Ocean of Particles Characterization of Particulate Trace Elements by the GEOTRACES Program

The GEOTRACES program has greatly expanded measurements of trace elements, which serve as key nutrients, harmful contaminants, and tracers of ocean processes and past conditions. Many elements tend to associate with particulate matter, and GEOTRACES has been particularly valuable for growing our understanding of this fraction. Focusing on the micronutrient iron as an example, GEOTRACES data demonstrate that the majority of iron in the ocean is particulate. Chemically labile particulate iron, likely available for biological use, is also often more abundant than dissolved forms, particularly near continents and in the deep sea. This highlights the need to consider the particulate fraction in conceptual and numeric ocean models. Direct comparisons of particle-sampling methods highlight both the abundance of small particles (<0.45–0.8 μm), whose biogeochemical roles are still poorly known, and the difficulty in consistently capturing large, faster-sinking particles. In situ pumps with 0.8 μm filters often capture less small particulate iron than bottle-collected samples filtered onto 0.45 μm filters, but they can also capture more material near some sources. GEOTRACES datasets contain nearly sevenfold more dissolved than particulate iron measurements, and ongoing efforts to pair these measurements are needed in order to fully understand the cycles of iron and other important elements.

Concentration, speciation and risk effects of multiple environmentally sensitive trace elements in respirable fine-grained fly ash

Respirable fine-grained fly ash (RFA) is captured very inefficiently by existing air purification devices of power plant, leading to increasing concerns regarding their migration and subsequent interaction with body due to fine particle size and its complex toxic composition. Trace elements of RFA in three groups with five different sizes between 8–13 µm were analyzed in terms of available concentration, speciation and risk effects. The concentration, pollution level and ecological risk level of elements in RFA were related to particle sizes. Chronic non-carcinogenic effect risk (NER) and carcinogenic effect risk (CER) were negatively correlated with particle size. The individual weight of exposed subjects, corresponding trace elements concentration and ingestion rate in RFA were three significant variables influencing CER. NER and CER had a tenfold exaggerated effect when calculated using total element concentration of RFA. In addition to individual differences and exposure conditions, trace element properties, speciation and available concentration were the dominant factor responsible for ecological and environmental effects of trace elements in RFA, following the order As>Ni, Mn>Cr>Pb>Cu>Zn. Results of this work highlight the effects and differences of trace elements in RFA on ecology and health, and provide a basis for further pollution control and human health warning.

The impacts of fine particulate matter components and trace elements on rates of dementia hospitalization

The impacts of fine particulate matter components and trace elements on rates of dementia hospitalization

Evaluation of air quality and health risks associated with trace elements in respirable particulates (PM2.5) from Islamabad, Pakistan.

Fine atmospheric particulates are associated with numerous environmental and health issues as they can penetrate deeply in the respiratory tract thereby adversely affecting the human health. This study aimed to investigate the concentrations of trace elements in the respirable (PM2.5) fraction of the atmospheric particulates and to understand their pollution status and health risks. The samples were collected from Islamabad, and the metals were extracted using HNO3 and HCl based extraction method. Atomic absorption spectroscopy was employed to quantify the concentrations of selected trace elements. PM2.5 exhibited considerable variations in their minimum (4.737µg/m3) and maximum (108.1µg/m3) levels. The significant contributors among the selected elements bound to PM2.5 were Ca (1016ng/m3), K (759.8ng/m3), Mg (483.0ng/m3), Fe (469.7ng/m3), and Zn (341.1ng/m3), while Ag (0.578ng/m3) was found at the lowest levels with an overall descending order: Ca > K > Mg > Fe > Zn > Cu > Pb > Ni > Cd > Mn > Sr > Cr > Co > Li > Ag. Multivariate PCA and CA identified industrial activities, combustion processes and automobile emissions as the main anthropogenic contributors to particulate pollution. Enrichment factors and geoaccumulation indices were computed to assess the pollution status. The results also revealed that among the trace elements, Cd showed extremely high contamination, followed by Ag, Zn, and Pb, which showed moderate to high contamination in the atmospheric particulates. Carcinogenic health risks from Pb and Ni were found to be within the safe limit (1.0 × 10-6); however, Cr, Co, and Cd exposure was linked to significant cancer risks. The present elemental levels in PM2.5 were also compared with the reported levels from other regions around the world.

Extreme hydrological regimes of a small urban river: impact on trace element partitioning, enrichment and fluxes.

The input of trace elements from a small urban river (Las River, Toulon, France) located on the northern Mediterranean coast was studied during both base flow and flood events. A 2-year monitoring period of water flow and suspended particulate matter (SPM) showed a typical Mediterranean hydrological regime: a strong increase in water flow and SPM during short flood periods. During the flood event, an up to 2-fold increase in dissolved trace element (DTM) concentrations and particulate trace element content in SPM (PTM) was observed compared to the baseline discharge. The enrichment factor of elements in the SPM ranges from low or moderate for Co, Ni and Cr (1.0-4.7) to extremely high for Cd (157). However, the enrichment factors decrease from base flow to flood, indicating a dilution effect with a large yield of weathering particles with higher particle size. The most significant total trace element loading occurred during flood, ranging from 78% for As and Ni to 91% for Pb, while PTM loading during flood ranged from 35% for As to 77% for Pb. The specific dissolved fluxes during the flood are significantly higher for Pb, Cu and Zn than in the surrounding rivers, indicating specificity in the catchment (lithology). This study shows the importance of monitoring the transport of pollutants through small urban rivers and their potential impact on the coastal region, especially when they enter small and closed bays, as a receiving pool.

Environmental Impacts of Coal Combustion Residuals: Current Understanding and Future Perspectives.

On-site solid-waste impoundments, landfills, and receiving water bodies have served as long-term disposal sites for coal combustion residuals (CCRs) across the United States for decades and collectively contain billions of tons of CCR material. CCR components include fine particulate material, minerals, and trace elements such as mercury, arsenic, selenium, lead, etc., which can have deleterious effects on ecosystem functioning and public health. Effects on communities can occur through consumption of drinking water, fish, and other aquatic organisms. The structural failure of impoundments, water infiltration, leakage from impoundments due to poor construction and monitoring, and CCR effluent discharges to water bodies have in the past resulted in harmful environmental impacts. Moreover, the risks posed by CCRs are present to this day, as coal continues to account for 11% of the energy production in the United States. In this Critical Review, the legacy of CCR disposal and the concomitant risks posed to public health and ecosystems are assessed. The resiliency of CCR disposal sites in the context of increased frequency and intensity of storm events and other hazards, such as floods and earthquakes, is also evaluated. We discuss the current state of knowledge on the environmental fate of CCR-derived elements, as well as advances in and limitations of analytical tools, which can improve the current understanding of CCR environmental impacts in order to mitigate the associated risks. An assessment of the 2015 Coal Ash Final Rule is also presented, along with needs to improve monitoring of CCR disposal sites and regulatory enforcement.

Investigation of reducing trace elements and PM emission from coal combustion by blending coal

The fine particles and their associated trace elements derived from coal combustion had a severe adverse effect on the environment or human health. In this paper, HLH (lignite) and HS (bituminous) were blended under the predetermined ratio, and the blended coal was burned in a drop tube furnace (DTF). The particle size distribution (PSD) of particulate matter (PM) and trace elements (As, Se, Pb and Cd) were investigated during the blending coal combustion. The experimental results demonstrated that the mass concentration of PM from HLH coal combustion was higher than that of HS coal, which was attributed to the thermal instability of the minerals in HLH (lignite). In addition, it was found that PSD of PM was not consistent with that of trace elements. The blending coal combustion not only suppresses PM formation, but also reduces As, Se, Pb and Cd emission due to lowering ash fusion temperature of blending coal and liquidus capture of fine particles. Compared with the calculated values, the mass concentration of PM0.2–0.5, PM0.5–1.0, PM1.0–2.5 and PM2.5–10 from HS1HLH1 (the mass ratio of HS/HLH was 1.0) combustion was reduced by 6.06 %, 45.02 %, 50.17 % and 55.59 %, respectively. At the same time, the reduction efficiency of As, Se, Pb, and Cd emission concentration in PM0.2–0.5 by HS1HLH3 were the highest (about 91.7 %, 71.06 %, 83.45 % and 73.50 %), and their emission concentration was 0.16, 0.95, 0.97 and 0.02 μg/m3. While HS1HLH1 was the most effective for reducing As, Se, Pb, and Cd emission in PM0.5–10. Lastly, above 50 % As, Pb and Cd in PM10 was existed as the mobile phase during raw coal combustion, which had a harmfulness for the environment or human being. HS1HLH1 could stabilize Se, Pb, and Cd, and their residual fraction in PM10 were 59.4 %, 49.1 % and 29.2 %, respectively.

The migration and transformation characteristics of particulate matter and trace elements in a cement plant

ABSTRACT The particulate matter (PM) and trace elements (TEs) from industrial kilns have attracted extensive attention due to serious harm to the environment. In this work, the emissions of PM and TEs were investigated in a new dry-process cement plant. The PM was collected through a particle sampling system, and the TEs were determined by inductively coupled plasma mass spectrometry in the collected particle. The results showed significant differences of PM and TEs in the flue gas and hot air. The content of PM10 in flue gas was an order of magnitude higher than that in hot air. The TEs in flue gas were mainly Mn. In hot air, Cr accounted for more than half of the mass concentration of TEs. The conditioning tower could reduce PM10 and TEs in the flue gas. The removal efficiencies were 33.77% and 50.37%, respectively. PM10 and TEs at the end of the kiln were 18.91 mg·m−3 and 77.53 μg·m−3, respectively. The gravity settler could remove PM10 and TEs well through sedimentation, and the removal efficiencies were 31.11% and 68.18%, respectively, while the exhaust heat boiler of air quenching cooler had little effect on PM10 and TEs in the hot air.

Occurrence, contamination level and ecological risk assessment of dissolved and particulate trace elements in rivers entering the southwestern Mediterranean Sea

Metal pollution in rivers should not be overlooked before their entry into the sea. However, there are few studies for estimating such contamination in rivers entering the Algerian coastal waters. Semimonthly quantification of dissolved and particulate metals, near the mouths of two industrial-tainted rivers, El Harrach and Mazafran rivers, was carried out during a period of one year. All the trace metals analyzed are originating from anthropogenic sources (EF > 1.5), with higher contamination of dissolved Pb, Cd, Zn and Ni and a slight degree of contamination of particulate Cu and Zn (0 < Igeo < 1). Particulate metals show a stable complex with the particulate phase (e.g. 2 < LogKd < 6). The risk assessment results indicate that particulate Pb and Zn have a 33% likelihood of toxicity for adverse biological effects. A significant toxicity effect (ΣTUi >4) of the combined particulate metals (Pb, Cd, Cu, Zn, Cr, Ni and As) was primarily due to the higher particulate Cd, Zn, and Cr availability.

Particulate trace element distributions along the Canadian Arctic GEOTRACES section: shelf-water interactions, advective transport and contrasting biological production

Marine particles are important regulators of the biogeochemistry of many trace elements and isotopes in the ocean, and as such, there has been an increasing motivation to unravel the processes which control their cycling. Here, we present vertical distributions of total particulate trace elements (Al, V, Fe, Mn and P) and particulate organic carbon and particulate nitrogen (POC and pN) collected during the GEOTRACES Canadian cruise in 2015 in the Canada Basin (CB), the Canadian Arctic Archipelago (CAA), Baffin Bay (BB) and the Labrador Sea (LS), where particulate trace metal data are scarce. While particulate trace elements are generally affected by one-dimensional dynamics in ocean waters (e.g. deposition, scavenging/remineralization, and sinking), lateral transport of lithogenic-derived particles (pAl, pV and pFe) plays a dominant role in shaping their distributions in the deep CB, BB and LS basins. Higher concentrations of the aforementioned particulate trace elements are measured along the flow path of boundary currents and in near-bottom waters. Unlike pAl, pV and pFe, primarily controlled by lithogenic sources, bulk pMn distributions in our study regions (with the exception of LS) are dominated by authigenic Mn+3/4 oxides, with distinctively high concentrations in CB and BB subsurface halocline waters, as well as in the deepest samples in BB. Enhanced bacterially-mediated Mn+2 oxide formation is anticipated to occur in these halocline waters which have the potential to sustain large populations of Mn oxidizing bacteria as result of the close sediment-water interactions and distinct environmental conditions of these water masses. Overall, the highest concentrations of pP, POC and pN occurred in surface and near-surface waters (>100 m) at the same density as a chlorophyll-a peak and transmissivity drop, with a clear west-east increasing concentration gradient from the CB to LS. In summary, biogeochemical cycles of particulate elements in the Canadian Arctic Ocean are controlled by enhanced lateral transport and sediment resuspension (pAl, pFe and pV), authigenic formation of Mn and biological production (pP, POC and pN).

Retention of trace elements in coal-fired flue gas by a novel heterogeneous agglomeration technology

Heterogeneous agglomeration (HA) is a very potential technology for coal-fired flue gas treatment. In this paper, the distribution and migration mechanisms of trace elements (TEs) such as Se, As and Pb in CFPPs were studied on a 30,000 m3/hr pilot-scale experimental platform. The influences of HA on the removal efficiency of gaseous and particulate TEs were well analyzed. The results showed that Se, As and Pb were enriched in fly ash, and their sensitivity to particle size is quite different. The content of Se was the highest in PM1, reaching 193.04 mg/kg at the electrostatic precipitator (ESP) outlet. The average particle size of the total dust before ESP increased significantly from 21.686 to 62.612 µm after injecting the heterogeneous agglomeration adsorbent, conducive to its further removal by ESP. In addition, the concentrations of gaseous Se, As and Pb in the flue gas decreased after adsorbent spray, and accordingly, their contents in the hierarchical particles increased, indicating that the adsorbent could effectively promote the adsorption of gaseous trace elements in fly ash and reduce the possibility of their escape to the atmosphere. Total concentrations of Se, As and Pb emitted by wet flue gas desulfurization (WFGD) are 0.223, 0.668 and 0.076 µg/m3, which decreased by 59.98%, 47.69% and 90.71%, respectively. Finally, a possible HA mechanism model was proposed, where chemical adsorption, physical condensation and collision agglomeration of gaseous TEs and fine particles with adsorbent droplets occurred to form larger agglomerates.

Elucidating the responses of highly time-resolved PM2.5 related elements to extreme emission reductions

China's unprecedented lockdown to contain the spread of the novel coronavirus disease (COVID-19) in early 2020, provided a tragic natural experiment to investigate the responses of atmospheric pollution to emission reduction at regional scale. Primarily driven by primary emissions, particulate trace elements is vitally important due to their disproportionally adverse impacts on human health and ecosystem. Here 14 trace elements in PM2.5 were selected for continuous measurement hourly in urban representative site of Shanghai, for three different phases: pre-control period (1–23 January 2020), control period (24 January-10 February 2020; overlapped with Chinese Lunar New Year holiday) and post control period (11–26 February 2020) the city's lockdown measures. The results show that all meteorological parameters (including temperature, RH, mixing layer height et al.) were generally consistent among different periods. Throughout the study period, the concentrations of most species displayed a “V-shaped” trend, suggesting significant effects by the restriction measures imposed during the lockdown period. While this is not the case for species like K, Cu and Ba, indicating their unusual origins. As a case study, the geographical origins of Cu were explored. Seven major sources, i.e., Vehicle-related emission (including road dust; indicative of Ca, Fe, Ba, Mn, Zn, Cu; accounting for 30.1%), shipping (Ni; 5.0%), coal combustion (As, Pb; 4.2%), Se and Cr industry (24.9%), nonferrous metal smelting (Au, Hg; 7.5%) and fireworks burning (K, Cu, Ba; 28.3%) were successfully pinpointed based on positive matrix factorization (PMF) analysis. Our source apportionment results also highlight fireworks burning was one of the dominant source of trace elements during the Chinese Lunar New Year holiday. It is worth noting that 56% of the total mass vehicular emissions are affiliated with non-exhaust sources (tire wear, brake wear, and road surface abrasion).

Demonstration and application of heterogeneous agglomeration technology in a 350 MW coal-fired power plant: Removal of particulate matter and trace elements

For a domestic 350 MW coal-fired power plant, the effect of heterogeneous agglomeration technology on the migration and emission of three trace elements of arsenic, selenium and lead in tail flue gas was studied. The results show that heterogeneous agglomeration technology can promote the attachment of gaseous harmful trace elements to particulate matter effectively. The reduction rates of gaseous As, Se and Pb concentrations at the ESP outlet were 24.10%, 61.08%, and 70.38%, respectively. Under the synergistic effect of ESP, more As, Se, and Pb are enriched in fly ash, and the concentration of As, Se, and Pb in fine particles below 10 μm at the ESP outlet is reduced by 54.48%, 56.47%, and 75.17%, respectively. In addition, after spraying the agglomerating agent, the final As, Se, and Pb concentrations in the atmosphere were 1.29 μg/m3, 2.01 μg/m3, and 1.12 μg/m3, which were far lower than those of the relevant EPA emission limits.

Morphological properties, chemical composition, cancer risks and toxicological potential of airborne particles from traffic and urban background sites

From a sampling campaign from December 2018 to June 2019, at a traffic and an urban background site in Coimbra, Portugal, two particulate matter (PM10) samples from each month were selected to characterise the morphology by scanning electron microscopy, to determine the organic and inorganic chemical composition by multiple analytical techniques and to assess the ecotoxicity by the Vibrio fischeri bioluminescence inhibition assay. PM10 concentrations in winter were approximately twice as high as those recorded in the spring. Biomass burning was the greatest contributor to air pollution in winter at both sites. The contribution of vehicle emissions to the PM10 at the roadside was, on average, 7 times higher than at the background location. Distinct particle morphologies were observed. Higher abundances of aggregates enriched in Fe, Ti, Ba, Cr, Co, Cu, Zr, Mn and soot particles were registered in samples from the roadside. Bivariate plots suggested common sources of PAHs, mostly traffic and biomass burning, across the city. Benzo[a]pyrene equivalent concentrations were within the values documented for other European cities. Cancer risks resulting from exposure to PAHs by inhalation were estimated to be low (10−6 ≤ to <10−4) for both sites. The noncarcinogenic risks from particulate trace elements were always higher than the target value of 1. Cancer risks for Cr were found to be higher than the acceptable level (10−6). The calculation of toxic units indicated that 64% of the samples from the roadside location were toxic and 14% very toxic, while the corresponding shares for the urban background site were 50% and 7%, respectively. Many PM10-bound constituents, especially markers of biomass burning (e.g. anhydrosugars) and traffic emissions (e.g. Fe, Cu, Zn), showed significant statistical correlations with toxicity.

Trace elements migrating from tailings to rock varnish laminated sediments in an old mining region from Nelson, Nevada, USA

The dispersion and influence of soluble and particulate trace elements (TEs) present in the materials from abandoned mines is an imminent problem on terrestrial and aquatic environments. The goal of this research is to provide a broader view of such transport, assessing particle size distribution and TE interactions (e.g., scavenging) with mine tailings and locally derived sediments transported by water in arid region. Sand grains from wash sediment were collected from a dry ephemeral wash in Nelson, Nevada where the Techatticup Mine and Mill worked between 1850 and 1960. Samples were evaluated to determine the association and behavior of certain metals and metalloids including aluminum, arsenic, barium, cadmium, copper, chromium, iron, manganese, lead, selenium, vanadium, and zinc to rock varnish laminated sediments. Results show that some metals and metalloids were more concentrated on larger particles whereas others indicated the opposite tendency. For example, As was greatest on silt fractions and least on coarse fractions, while Se was detected only on silts. Cr, Cu, Fe, Mn, Pb, and Zn concentrations all increased with decreasing particle size (silt > sand > coarse), whereas Al, Ba, and V showed the opposite trend (silt < sand < coarse). The enrichment factor (EF) of Cu, Zn, Pb, As, and Se were lower in mine tailing sediment treated with wash than those obtained for source material. However in treated wash sediment samples, the high EFs of Ba, Cr, V, and Mn suggested a possible greater affinity of these metals to the Al, Fe, and Mn oxides from the RV sediment. The data found in this study show that transport of contaminated sediments in arid regions could lead to the enrichment of some TEs in down-gradient areas from source materials.

Baseline Air Monitoring of Fine Particulate Matter and Trace Elements in Ontario’s Far North, Canada

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.

Evaluating the effectiveness of soil conservation at the basin scale using floodplain sedimentary archives

Evaluation of the spatial and temporal composition of floodplain sediments and soils is critical in the creation of soil management strategies for impacted riverine catchments. The objective of this study was to determine the distribution, and to identify the sources, of particulate trace elements and fallout radionuclides in the catchment of the River Avon (SW England), where sedimentary processes had been altered by reservoir construction in the 1950s. The catchment was compartmentalized into its main functional units namely, cultivated land, pasture, woodland, wet moorland, and channel bank. Surface soils were collected in each unit, along with four strategically-placed cores, all of which were analyzed for particle size, fallout radionuclides and elemental concentrations. Sediment particle sizes and sediment accumulation rates were affected by the construction of the reservoir, specifically the distributions of silt and clay. The concentrations of fertilizer constituent Cr and P were highly correlated in the mid-catchment but were unrelated downstream due to elevated concentrations of Cr from geological deposits. Copper, As, Pb and Sn had variable down-core distributions, with pulses in concentrations due to mining inputs. The contributions of the end-member sources of particulate elements in the sedimentary mixtures were evaluated, quantitatively, using a Bayesian Mixing Model and the cultivated land was identified as a significant contributor to the mixtures, independent of space and time. The results contribute to advances in soil quality and conservation measures as components of a catchment management plan for the Avon, an approach maybe applicable to other small catchments in the UK and internationally.