Isotopic evolution of atmospheric Pb from metallurgical processing in Flin Flon, Manitoba: Retrospective analysis using peat cores from bogs

Sources of exposure to lead in Arctic and subarctic regions: a scoping review

Understanding lead exposure pathways is a priority because of its ubiquitous presence in the environment as well as the potential health risks. We aimed to identify potential lead sources and pathways of lead exposure, including long-range transport, and the magnitude of exposure in Arctic and subarctic communities. A scoping review strategy and screening approach was used to search literature from January 2000 to December 2020. A total of 228 academic and grey literature references were synthesised. The majority of these studies (54%) were from Canada. Indigenous people in Arctic and subarctic communities in Canada had higher levels of lead than the rest of Canada. The majority of studies in all Arctic countries reported at least some individuals above the level of concern. Lead levels were influenced by a number of factors including using lead ammunition to harvest traditional food and living in close proximity to mines. Lead levels in water, soil, and sediment were generally low. Literature showed the possibility of long-range transport via migratory birds. Household lead sources included lead-based paint, dust, or tap water. This literature review will help to inform management strategies for communities, researchers, and governments, with the aim of decreasing lead exposure in northern regions.

Identification of possible sources for potentially toxic elements and polycyclic aromatic hydrocarbons and their spatially varying relationships in urban soils of Dublin, Ireland

Potentially toxic elements (PTEs) and polycyclic aromatic hydrocarbons (PAHs) harm the ecosystem and human health, especially in urban areas. Identifying and understanding their potential sources and underlying interactions in urban soils are critical for informed management and risk assessment. This study investigated the potential sources and the spatially varying relationships between 9 PTEs and PAHs in the topsoil of Dublin by combining positive matrix factorisation (PMF) and geographically weighted regression (GWR). The PMF model allocated four possible sources based on species concentrations and uncertainties. The factor profiles indicated the associations with high-temperature combustion (PAHs), natural lithologic factors (As, Cd, Co, Cr, Ni), mineralisation and mining (Zn), as well as anthropogenic inputs (Cu, Hg, Pb), respectively. In addition, selected representative elements Cr, Zn, and Pb showed distinct spatial interactions with PAHs in the GWR model. Negative relationships between PAHs and Cr were observed in all samples, suggesting the control of Cr concentrations by natural factors. Negative relationships between PAHs and Zn in the eastern and north-eastern regions were related to mineralisation and anthropogenic Zn-Pb mining. In contrast, the surrounding regions exhibited a natural relationship between these two variables with positive coefficients. Increasing positive coefficients from west to east were observed between PAHs and Pb in the study area. This special pattern was consistent with prevailing south-westerly wind direction in Dublin, highlighting the predominant influences on PAHs and Pb concentrations from vehicle and coal combustion through atmospheric deposition. Our results provided a better understanding of geochemical features for PTEs and PAHs in the topsoil of Dublin, demonstrating the efficiency of combined approaches of receptor models and spatial analysis in environmental studies.

Polycyclic aromatic compounds (PACs) in the Canadian environment: A review of sampling techniques, strategies and instrumentation

A wide variety of sampling techniques and strategies are needed to analyze polycyclic aromatic compounds (PACs) and interpret their distributions in various environmental media (i.e., air, water, snow, soils, sediments, peat and biological material). In this review, we provide a summary of commonly employed sampling methods and strategies, as well as a discussion of routine and innovative approaches used to quantify and characterize PACs in frequently targeted environmental samples, with specific examples and applications in Canadian investigations. The pros and cons of different analytical techniques, including gas chromatography - flame ionization detection (GC-FID), GC low-resolution mass spectrometry (GC-LRMS), high performance liquid chromatography (HPLC) with ultraviolet, fluorescence or MS detection, GC high-resolution MS (GC-HRMS) and compound-specific stable (δ¹³C, δ²H) and radiocarbon (Δ¹⁴C) isotope analysis are considered. Using as an example research carried out in Canada's Athabasca oil sands region (AOSR), where alkylated polycyclic aromatic hydrocarbons and sulfur-containing dibenzothiophenes are frequently targeted, the need to move beyond the standard list of sixteen EPA priority PAHs and for adoption of an AOSR bitumen PAC reference standard are highlighted.

A multivariate examination of the timing and accumulation of potentially toxic elements at Las Conchas bog (NW Spain)

The inorganic content of the well-preserved 3.2-m record of Las Conchas bog (NW Spain), covering 8000 cal yr BP., was analysed. To study natural vs. human contributions, we applied an innovative approach, namely the sequential study of multivariate statistics (factor analysis followed by clustering of the factor score matrix) and enrichment factors (EFs). The increasing weight of potentially toxic elements (PTEs) such as the geochemical association of Zn, Pb and Cd (EFs higher than 10, 20 and 40 in the last two centuries) was revealed, and corroborated by the contrast between the contents of anthropogenic Pb and total Rare Earth Elements (a suitable proxy for natural geogenic supplies). Furthermore, elements such as Hg, Tl and As also showed enrichment in the most recent samples of the study core. Some of them are commonly associated with global atmospheric transport; however, in this case, their increasing contents could also be explained by nearby industrial and mining activities. In summary, severe pollution was observed in the uppermost part of the record, thereby pointing to an important environmental concern. Given that local and regional sources of PTEs, such as mining and heavy industry, especially Zn smelting, were probably the main historical causes of this contamination and that some of these industries are still active, we consider that our findings deserve further attention.

Anthropogenic and lithogenic fluxes of atmospheric lead deposition over the past 3600 years from a peat bog, Changbai Mountains, China

Ombrotrophic peatlands are widely used to reconstruct atmospheric metal deposition histories. Here, we estimated the long-term atmospheric Pb deposition flux using ombrotrophic peatland data from the Changbai Mountains, northeast China. A peat profile of 320-cm depth was sampled and cut into 164 slices for measurement of Pb and other elements by ICP-MS and ICP-AES and radiometric dating by ²¹⁰Pb, ¹³⁷Cs and ¹⁴C. Pb concentration in the peat ranged from 2.18 to 68.33 mg kg^-1, while the atmospheric Pb deposition flux ranged from 0.12 to 12.49 mg m^-2 a^-1. The Little Ice Age (cold and wet climate) led to low Pb concentration, Pb/Sc ratio, and Pb deposition flux (4.40 ± 0.70 mg kg^-1, 2.04 ± 0.38, and 0.28 ± 0.09 mg m^-2 a^-1, respectively). On the other hand, intense volcanic eruptions resulted in high Pb concentration, Pb/Sc ratio, and P flux (54.48 ± 13.08 mg kg^-1, 7.85 ± 2.09, and 8.15 ± 2.85 mg m^-2 a^-1, respectively). In addition, rapid economic development since the 1980s resulted in a gradual increase of anthropogenic Pb concentration from 1.54 mg kg^-1 to 5.85 mg kg^-1; thus, the anthropogenic Pb deposition flux (0.43 ± 0.21 mg m^-2 a^-1) was high during this period. In general, peat Pb concentration and atmospheric Pb deposition fluxes in this region have been affected by climate change, volcanic eruptions, and human activities. It was further demonstrated that atmospheric Pb emissions and deposition in China decreased since leaded gasoline was phased out in 2001. The results are critical to understand the geochemistry of Pb and to assess the effects of human activities on atmospheric Pb emissions and deposition in China.

Deposition of mullite in peatlands of southern Poland: Implications for recording large-scale industrial processes

Mullite, a pure aluminosilicate (Al₆Si₂O₁₃), is a rare natural rock component, known for centuries as a very resistant ceramic material. It is also a common waste product of high-temperature coal combustion that is emitted in quantity from coal-based power stations. The occurrence of mullite in two Sphagnum-dominated peatlands located near the Upper Silesia industrial region in southern Poland is described. For the first time, a complete record of mullite deposition in the peat profiles has been obtained by XRD analyses of ashed peat samples. The mullite distribution is compared with records of Hg, Pb and Cu. While mullite is supplied during high temperature processes only, Cu, Pb and Hg show more complex pattern of distribution. Both peat profiles contain elevated amounts of mullite in the time span between ca 1950-1990 with a maximum content in ca 1980. The first appearance (∼1900) of mullite is indicative of the beginning of energy production in coal-based power plants in the region. Mullite is proposed here as an indicator of industrialization in geological records. It is resistant to post-depositional processes, emitted globally, and restricted to large-scale industry.

Concerns about Quadrupole ICP-MS Lead Isotopic Data and Interpretations in the Environment and Health Fields

There has been a massive increase in recent years of the use of lead (Pb) isotopes in attempts to better understand sources and pathways of Pb in the environment and in man or experimental animals. Unfortunately, there have been many cases where the quality of the isotopic data, especially that obtained by quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS), are questionable, resulting in questionable identification of potential sources, which, in turn, impacts study interpretation and conclusions. We present several cases where the isotopic data have compromised interpretation because of the use of only the major isotopes ²⁰⁸Pb/²⁰⁶Pb and ²⁰⁷Pb/²⁰⁶Pb, or their graphing in other combinations. We also present some examples comparing high precision data from thermal ionization (TIMS) or multi-collector plasma mass spectrometry (MC-ICP-MS) to illustrate the deficiency in the Q-ICP-MS data. In addition, we present cases where Pb isotopic ratios measured on Q-ICP-MS are virtually impossible for terrestrial samples. We also evaluate the Pb isotopic data for rat studies, which had concluded that Pb isotopic fractionation occurs between different organs and suggest that this notion of biological fractionation of Pb as an explanation for isotopic differences is not valid. Overall, the brief review of these case studies shows that Q-ICP-MS as commonly practiced is not a suitable technique for precise and accurate Pb isotopic analysis in the environment and health fields.

Chronology of anthropogenic impacts reconstructed from sediment records of trace metals and Pb isotopes in Todos os Santos Bay (NE Brazil)

The evolution of the impacts of anthropogenic activities in Todos os Santos Bay was evaluated by profiles of trace metals and Pb isotopes determined in sediment cores. Fluxes of metals increased up to 12, 4 and 2 times for Cu, Pb, and Zn, respectively, compared to those recorded in the beginning of the 20^th century. Stable Pb isotopes identified a decommissioned lead smelter and burning of fossil fuels as the main sources of Pb. Most metals showed minor to moderate enrichment factors (EF<4), but Cu and Pb were highly enriched (EF=28 and 6, respectively) at the Aratu harbor. Temporal changes in sediments were associated to different activities, namely Pb smelting, burning of fossil fuels, maritime traffic, petroleum related activities, inputs of domestic effluents, and changes in land uses. The effects of the implementation of environmental policies to improve the waters of the bay could not be identified in the evaluated cores.