Environmental Science

Permanent URI for this collectionhttps://hdl.handle.net/1807/3069

Browse

Now showing 1 - 20 of 96

Equity-based energy retrofits to address energy poverty in Canada
(Elsevier BV, 2024-12) Tozer, Laura; Baggio, Guilherme; Kantamneni, Abhilash; MacRae, Hannah
Many energy efficiency and decarbonization retrofit programs aim to alleviate energy poverty by targeting low-income households, but these programs do not always address the multiple determinants of energy poverty. This study develops a vulnerability-based framework to explore the extent to which energy retrofit programs designed for low-income households comprehensively account for socioeconomic, demographic, and cultural structures that shape energy poverty experiences, employing Canada as an empirical case study using key informant interviews with program administrators. The framework conceptualizes energy poverty as the vulnerability to future housing-related harms, amplified by energy-related risk factors, and conditioned by a household's inability to adequately respond. The study finds several key issues limiting the capacity of low-income retrofit programs to address the overlapping and compounding determinants of energy poverty, including inadequate funding, exclusion of the poorest quality housing, limited retrofit options, and a narrow focus on energy efficiency gains. This study shows key opportunities to expand and deepen the current ecosystem of low-income retrofit programs by expanding existing policy innovations. The paper also offers suggestions for widening the policy arena to address energy poverty, both within retrofit programs and beyond.
Nature for Resilience? The Politics of Governing Urban Nature
(Taylor & Francis, 2022-11-02) Tozer, Laura; Bulkeley, Harriet; Kiss, Bernadett; Luque-Ayala, Andrés; Voytenko Palgan, Yuliya; McCormick, Kes; Wamsler, Christine
Transcending initial efforts to make cities “climate smart” by focusing on the potential of new technologies and infrastructural interventions, various actors are increasingly interested in deploying nature to help achieve urban resilience. In this context, rather than taking resilience as a given property of particular systems or entities, it is important to examine why, how, with what implications, and for whom resilience is being enacted. We examine how and why nature-based solutions are being mobilized as a means for governing the resilience of cities and what this means for the ways in which urban resilience is imagined and enacted by different actors. Recognizing that behind different approaches to resilience are diverse ways of valuing nature, we identify four value positions through which nature comes to be understood, given meaning, form, and purpose. Drawing on systematic document analysis and sixty-six interviews from Cape Town, Mexico City, and Melbourne, we discuss how these four value positions of nature are manifested in nature-based interventions for resilience, as well as the implications both for the politics of resilience interventions and the opportunities for enabling social benefit through nature-based solutions. We find that the integration of intrinsic values for nature opens opportunities for nature-based solutions to enable social benefits through an increased focus on the means through which they are implemented. We conclude that urban-nature-as-resilience interventions serve to embed values and the socionatures they produce within the city, creating fundamentally different consequences for the forms and politics of nature-based interventions designed to realize urban resilience.
Mobilizing infrastructure investments for urban climate action in Africa: enabling factors for multilevel action
(Taylor & Francis, 2022-08-26) Tozer, Laura; Mayr, Marcus; Greenwalt, Julie; Nadi, Gifti; Runhaar, Hens
This article explores the importance of national governments and national-local relationships for scaling up local climate action to achieve global goals. From the Sustainable Development Goals to the New Urban Agenda to the Paris Climate Change Agreement, the achievement of global sustainability goals will depend on deep changes to national infrastructure and urban systems. Through an analysis of climate action planning and investments in exemplary cases in Africa, the paper highlights the opportunities and challenges that come with integrating national governments into urban-focused priorities and needs, especially for mobilising financial resources. The paper finds that scaling up city climate action in the selected African countries benefits from a constructive multi-level relationship between local and national institutions and stakeholders to shape and improve the legislative, financial and operating frameworks to enable systemic change. Large-scale urban climate action can be enabled by formal multi-level institutional arrangements, links to politically prioritised policy frameworks, and transformative aims that address both climate and socio-economic benefits for communities.
Achieving deep-energy retrofits for households in energy poverty
(Ubiquity Press, Ltd., 2023-06-01) Tozer, Laura; MacRae, Hannah; Smit, Emily
Climate change and energy poverty are two sustainability challenges that can be addressed through deep-energy retrofits for homes. This systematic review identifies which factors influence the achievement of energy retrofits for households vulnerable to energy poverty. It covers both energy-poor households and the landlords or building owners of energy-poor households. The results identify a range of influential factors across several themes: financial, policy and organizational, trust and communication, technical, attitudes and values, and health. Health and quality of life are particularly influential motivating factors among households vulnerable to energy poverty, as is the presence of trust and communication between stakeholders. Multiple financial considerations are also important, such as the availability of no-cost retrofit options and the prospect of lower energy and maintenance costs. Lastly, government requirements to retrofit and minimum energy standards are motivating, particularly in the social housing sector. These findings and the lack of focus on energy poverty within the energy retrofit literature and policies point to a need for further research on this topic, and for retrofit policies specifically targeted to households vulnerable to energy poverty.
What’s behind the barriers? Uncovering structural conditions working against urban nature-based solutions
(Elsevier BV, 2022-04) Dorst, Hade; van der Jagt, Alexander; Toxopeus, Helen; Tozer, Laura; Raven, Rob; Runhaar, Hens
Nature-based solutions (NBS) are a promising and innovative approach to address multiple sustainability challenges faced by cities. Yet, NBS are not integrated into mainstream urban development practices. Based on a qualitative comparative case study of Germany, Hungary, the Netherlands, Spain, Sweden, and the United Kingdom, this study shows how barriers to mainstreaming urban NBS are shaped by the structural conditions in urban infrastructure regimes, which offers an improved, context-sensitive understanding of why such barriers persist. We identify underlying structural conditions shaping seven key barriers to urban NBS: limited collaborative governance, knowledge, data and awareness challenges, low private sector engagement, competition over urban space, insufficient policy development, implementation and enforcement, insufficient public resources, and challenging citizen engagement. This study also advances an understanding of urban infrastructure regimes as complex, heterogeneous systems, made up of different functional domains that define the space available for sustainability innovations. Importantly, our case comparison reveals that similar barriers to NBS mainstreaming in planning processes are caused by different structural conditions across countries. For example, perceived causes of limited citizen engagement are low environmental awareness in Spain, a lack of resources to support participation in Hungary, and NIMBY-ism in the Netherlands. Our findings stress the importance of moving beyond ‘silver bullet’-type approaches to addressing NBS mainstreaming barriers, towards systemic but context-sensitive responses, tailored to specific urban infrastructure regimes. This systematic understanding of barriers and their underlying structural conditions can help both scholars and practitioners identify promising pathways for the mainstreaming of NBS as an urban sustainability innovation.
Reduction of industrial iron pollution promotes phosphorus internal loading in eutrophic Hamilton Harbour, Lake Ontario, Canada
(2019-09) Markovic, Stefan; Liang, Anqi; Watson, Sue B; Depew, David; Zastepa, Arthur; Surana, Preksha; Byllaardt, Julie Vanden; Arhonditsis, George; Dittrich, Maria
Diagenetic sediment phosphorus (P) recycling is a widespread phenomenon, which causes degradation of water quality and promotes harmful algal blooms in lakes worldwide. Strong P coupling with iron (Fe) in some lakes is thought to inhibit diagenetic P efflux, despite elevated P concentrations in the sediment. In these sediments, the high Fe content leads to P scavenging on ferric Fe near the sediment surface, which increases the overall P retention. Reduced external Fe inputs in such lakes due to industrial pollution control may lead to unintended consequences for sediment P retention. Here, we study sediment geochemistry and sediment-water interactions in the historically polluted Hamilton Harbour (Lake Ontario, Canada) which has undergone 30 years of restoration efforts. We investigate processes controlling diagenetic P recycling, which has previously been considered minor due to historically high Fe loading. Our results demonstrate that present sediment P release is substantial, despite sediment Fe content reaching 6.5% (dry weight). We conclude that the recent improvement of wastewater treatment and industrial waste management practices has reduced Fe pollution, causing a decrease in diagenetically reactive Fe phases, resulting in the reduction of the ratio of redox-sensitive P and Fe, and the suppression of P scavenging on Fe oxyhydroxides.
Organomineralization of proto-dolomite by a phototrophic microbial mat extracellular polymeric substances: Control of crystal size and its implication for carbonate depositional systems
(2020-01-01) Paulo, Carlos; Mckenzie, Judith A.; Raoof, Basirath; Bollmann, Jörg; Fulthorpe, Roberta; Strohmenger, Christian J.; Dittrich, Maria
Many have postulated that a specific microbial metabolism or the presence of microbes or/and their extracellular polymeric substances (EPS) can lead to the formation of dolomite. Although now there is the consensus that dolomite can be formed in the presence of microorganisms, the exact nature of the involvement of microbes in the dolomite nucleation remains a matter of debate. The focus is now in understanding how microbial mats determine the mineralogy of dolomite. Here we report the effect of the EPS extracted from phototrophic microbial mat isolated from a sabkha in Qatar dominated by cyanobacteria (Lyngbya aestuarii) in the formation of dolomite precursors at 25 °C and 40 °C. Both the temperature and the presence of EPS impact the size and morphology of minerals, promoting spherulitic and dumbbell growth in sulfate free solutions. The formation of proto-dolomite was enhanced by the abundance of carboxylated molecules in EPS which controlled the polymorphism of carbonates. Our study emphasizes the dual importance of organic matter and temperature in dolomite formation and their impact on mineral morphology and chemical composition in sabkhas.
Proto-dolomite formation in microbial consortia dominated by Halomonas strains
(2019-11) Alibrahim, Ammar; Al-Gharabally, Dunia; Mahmoud, Huda; Dittrich, Maria
Microbes can be found in hypersaline environments forming diverse populations with complex ecological interactions. Microbes in such environments were found to be involved in the formation of minerals including dolomite, a mineral of economic importance and whose origin has been long-debated. Various reports on in vitro experiments using pure cultures provided evidence for the microbial role in dolomite formation. However, culturing experiments have been limited in scope and do not fully address the possible interactions of the naturally occurring microbial communities; consequently, the ability of microbes as a community to form dolomite has been investigated in this study. Our experiments focused on examining the microbial composition by culturing aerobic heterotrophs from the top hypersaline sediments of Al-Khiran sabkha in Kuwait, a modern dolomite-forming environment. The objectives of this study were to assess the ability of two microbial consortia to form dolomite using enrichment culture experiments, mineralogy, and metagenomics. Proto-dolomite was formed by a microbial community dominated by Halomonas strains whereby degradation of the extracellular polymeric substances (EPS) was observed and the pH changed from 7.00 to 8.58. Conversely, proto-dolomite was not observed within a microbial community dominated by Clostridiisalibacter in which EPS continuously accumulated and the pH slightly changed from 7.00 to 7.29.
Pathways to Living Cities: A Policy & Governance Framework
(2022-10) Tozer, Laura; Mettler, Christine; Neeson, Emily; Salas Reyes, Raúl; Amon, Emily
The Pathways to Living Cities Framework was created to help green infrastructure practitioners learn what has worked in other communities, and what they can do to be successful. Showcasing best practices, resources, and case studies from across North America and Europe, the Framework lays out key strategies that have helped cities to accelerate more abundant, equitable, and thriving green infrastructure. The Framework also highlights the importance of working in partnership with community and industry in order to advance green infrastructure on both public and private lands.
Deep Decarbonization in Practice: Solutions and Challenges for Low-Carbon Building Retrofits
(Institute of Urban Studies, University of Winnipeg, 2019) Tozer, Laura
This paper examines efforts taking place in London, San Francisco and Stockholm to implement deep greenhouse gas emission cuts—‘deep decarbonization’—through the transformation of buildings and urban energy infrastructure for increased energy efficiency and low/zero carbon energy supply. Drawing on interviews, policy document analysis, and site tours to buildings and energy infrastructure, this paper analyzes how deep decarbonization is being embedded into urban buildings, energy systems, and institutions. It argues that practitioners are finding ways to create new low/zero carbon future buildings, but are having difficulty correcting the historical development path through retrofitting. This paper examines solutions and challenges brought to light by urban decarbonization in practice targeting existing buildings from which other cities can learn. Four key lessons for low/zero carbon retrofits are highlighted: 1) shift primary targets from homeowners to owners of multiple buildings, 2) expand the suite of resources available to support zero carbon retrofits, 3) experiment and teach using public investment, and 4) institutionalize energy and carbon reporting linked to municipal department targets. Given the necessity of low-carbon, efficient, and climate resilient building retrofits to address the climate crisis, action can be scaled up by considering buildings and energy infrastructure an infrastructure priority for public investment.
Catalyzing sustainability pathways: Navigating urban nature based solutions in Europe
(2022-05) Tozer, Laura; Bulkeley, Harriet; van der Jagt, Alexander; Toxopeus, Helen; Xie, Linjun; Runhaar, Hens
The notion that pathways can be identified and followed towards more sustainable futures has become an increasingly prevalent idea across the science and policy of global environmental change. Focusing on the debate within literatures on socio-technical systems, we find that pathways are often tied to the concept of scaling up such that they are dependent on trajectories which extend from the geographically small to large scale or from singular incidences to widespread adoption. Building on relational approaches to scaling, in this paper we argue that sustainability pathways need to be conceived as emerging from the catalytic interaction of multiple and overlapping efforts to change the status quo. We suggest that pathways can be conceptualized as being composed of ‘stepping stones’: bundles of related interventions that seize or create opportunities to build momentum for the implementation of innovations, the form of which is not predetermined. Drawing on 243 interviews, participant observation, and document analysis examining urban nature-based solutions across six European countries and the EU, we identify 20 stepping stones that can be used to accelerate the uptake of urban NBS in European cities. In the case of urban NBS in Europe, we find that the capacity of stepping stones to generate catalytic change strongly depends on how they interact with one another. We illustrate that pathways are not given but rather assembled through key interventions that collectively generate the capacities and momentum needed to overcome inertia and generate new socio-material orders in which such interventions are normalized as mainstream responses to sustainability challenges.
Technical pathways to deep decarbonization in cities: Eight best practice case studies of transformational climate mitigation
(2022-04) Linton, Samantha; Clarke, Amelia; Tozer, Laura
As the urgency for climate action heightens, local governments and stakeholders are developing pathways towards deep decarbonization at the local level and committing to community-wide greenhouse gas reductions of 80–100% by 2050 or earlier. Urban areas are the largest place-based source of greenhouse gas emissions, accounting for 71%–76% of global emissions. Local governments have direct and indirect control of over a significant proportion of emissions that occur within their municipalities. However, there remains a gap in knowledge about the local technical and policy pathways that are being developed in order to achieve deep decarbonization and how these pathways vary for different size cities. This study qualitatively analyzes eight local government deep decarbonization plans of cities that range in size from eight thousand to nine million people. We analyze emerging patterns among the cities, while also considering the impacts of the population size and the national context. Each city has unique circumstances and priorities when it comes to decarbonization, and not all cities prioritize their highest emitting sectors for decarbonization. We find that emerging technical pathways to deep decarbonization focus on five priority sectors (electricity, buildings, transportation, waste, and carbon sinks and storage), but also that several local governments are developing innovative strategies beyond what is described in the literature for decarbonizing the priority sectors within their jurisdiction and are expanding the scope of their plans to include emerging areas in GHG mitigation such as scope 3 and embodied greenhouse gas emissions.
Mainstreaming sustainable innovation: unlocking the potential of nature-based solutions for climate change and biodiversity
(2022-06) Xie, Linjun; Bulkeley, Harriet; Tozer, Laura
Sustainable innovation has been widely acknowledged as the key driver for societal transitions towards sustainability. Recently, there have been widespread calls to mainstream nature-based solutions (NBS), a form of socio-ecological-technical innovation, to address urban sustainable development concerns especially for climate change and increasingly for biodiversity loss. However, what mainstreaming means and how sustainability-oriented innovations like NBS can be mainstreamed to benefit multiple agendas remains underexplored. In this paper, we first critically discuss existing literature on mainstreaming and argue that the common understanding of the concept rooted in policy sciences does not fit the governance context in which urban innovations like NBS are being shaped and adopted. Drawing on sustainability transitions and urban studies literature, we then propose a new approach that promotes the use of NBS to deliver multiple sustainability goals simultaneously. We argue that mainstreaming NBS relies on identifying and acting on a certain set of key forms of interventions - stepping stones - that can facilitate the embeddedness and maintenance of NBS across urban infrastructure regimes. Based on case studies of existing European practices, we identify pivotal stepping stones and promising pathways for mainstreaming NBS for climate change and biodiversity separately and explore what this means for addressing both agendas simultaneously.
Transnational Governance and the Urban Politics of Nature-Based Solutions for Climate Change
(2022) Tozer, Laura; Bulkeley, Harriet; Xie, Linjun
Multiple visions for how urbanism can respond to the climate crisis and foster sustainability have emerged on the international agenda, including the ecocity, low-carbon city, smart city, and resilient city. These competing visions have been joined by one deploying “nature-based solutions.” We examine how nature-based solutions are emerging as a linchpin holding together the nature and climate agendas and what this means for where and by whom nature-based solutions are forming part of transnational urban governance. We argue that this field is animated by four frames connecting urban nature and climate: nature for resilience, nature for mitigation, the integrated benefits of nature, and nature first. Diverse actors, from conservation organizations to design firms to transnational municipal networks, draw on these frames and adopt new governance arrangements such that what it means to govern climate in the city is shifting. How this emerging nature–climate governance complex is structured will generate new momentum for governing urban nature over the coming decade.
Whose city? Whose nature? Towards inclusive nature-based solution governance
(2020) Tozer, Laura; Hörschelmann, Kathrin; Anguelovski, Isabelle; Bulkeley, Harriet; Lazova, Yuliana
Nature-based solutions have recently been embraced as one route towards simultaneously addressing urban environmental and social problems, but an emerging agenda has sought to ask whether and how the ‘greening’ of cities may actually reinforce inequalities or lead to new forms of social exclusion. Using comparative case-study analysis, this paper examines the extent to which nature-driven stewardship initiatives recognize and redress inequalities. We compare two urban contexts that have undergone significant societal transformations over the last two to three decades: Sofia and Cape Town. The comparison shows how nature-driven stewardship initiatives differentially address deeper roots of environmental, social and racial privilege shaped significantly by post-socialist and post-apartheid transition contexts. Instead of assuming a homogenous ideal of urban nature and focusing on questions of the distribution of urban nature and its access, this paper finds it is important to consider the kinds of social relations that are required to both shape decision-making processes and generate meaningful and diverse values and ways of relating to nature in the city. Furthermore, it finds that inclusive nature-based solution governance recognizes and redresses both inequalities in access and inequalities that perpetuate dominant views about what nature is and for whom nature is produced and maintained.
Catalyzing political momentum for the effective implementation of decarbonization for urban buildings
(2020) Tozer, Laura; University, Durham
This paper expands the toolkit available to consider the effectiveness of urban climate responses by examining political effectiveness in the implementation of urban decarbonization initiatives. By focusing on the politics of implementation, this approach complements dominant approaches for assessing effectiveness that emphasize greenhouse gas emission accounting. Drawing on case studies of urban building low carbon governance in Stockholm, London and San Francisco incorporating 40 expert interviews, the analysis provides insight into whether climate change mitigation measures are catalyzing political momentum that is untangling fossil fuels from institutions. It finds that urban decarbonization is gaining political momentum when it comes to new buildings, although with concerning implications for inequality and uneven development, but systemic change is limited since efforts to target existing buildings are stumbling over challenges. Two key insights are highlighted: 1) reframing the policy goal of urban climate mitigation to decarbonization productively refocuses attention on systemic change; 2) effective urban carbon governance is not only about providing instrumental tools, but it also involves triggering political dynamics that build momentum. Future urban decarbonization initiatives should consider the complementary roles of offering instrumental solutions and catalyzing political momentum through implementation.
Mobilizing infrastructure investments for urban climate action in Africa: enabling factors for multilevel action
(2022) Tozer, Laura; Mayr, Marcus; Greenwalt, Julie; Nadi, Gifti; Runhaar, Hens
This article explores the importance of national governments and national-local relationships for scaling up local climate action to achieve global goals. From the Sustainable Development Goals to the New Urban Agenda to the Paris Climate Change Agreement, the achievement of global sustainability goals will depend on deep changes to national infrastructure and urban systems. Through an analysis of climate action planning and investments in exemplary cases in Africa, the paper highlights the opportunities and challenges that come with integrating national governments into urban-focused priorities and needs, especially for mobilising financial resources. The paper finds that scaling up city climate action in the selected African countries benefits from a constructive multi-level relationship between local and national institutions and stakeholders to shape and improve the legislative, financial and operating frameworks to enable systemic change. Large-scale urban climate action can be enabled by formal multi-level institutional arrangements, links to politically prioritised policy frameworks, and transformative aims that address both climate and socio-economic benefits for communities.
The urban material politics of decarbonization in Stockholm, London and San Francisco
(2019) Tozer, Laura
This paper examines the implementation of carbon governance initiatives targeting urban buildings and energy infrastructure and uses a material politics approach to evaluate whether these practices are triggering trajectories towards decarbonization. Urban low carbon transitions suggest a substantial re-ordering of urban infrastructure. However, there is a critical need to engage with the material implications of low carbon practices since research so far has painted a picture of incremental ambitions struggling in implementation. This paper interrogates how carbon governance is implemented through urban buildings and energy systems, and the implications for urban decarbonization, by drawing on three urban case studies: Stockholm, London and San Francisco. The analysis draws on interviews with representatives from government, industry, utilities, building owners, and non-governmental organizations who are striving to achieve decarbonization in their cities. Patterns are emerging in what is being made to matter politically through the translation of carbon governance into building-energy infrastructure. In particular, the paper finds that (1) a short-term decision making timeline encourages action that incrementally reduces greenhouse gas emissions without fundamentally overcoming carbon lock-in, (2) actors are harnessing exceptional urban space to overcome the tyranny of cost-effectiveness in maintaining fossil fuel entrenchment (with concerning implications for justice and uneven development), (3) there is a pattern of individualization of responsibility for decarbonization, and (4) material politics are limiting the application of low carbon retrofits for the existing built form. Overall, this paper examines the implementation of urban carbon governance while encompassing the messy, materially embedded, and contested nature of infrastructure transformations.
Landscape controls on total mercury and methylmercury export from small boreal forest catchments
(Springer, 2022-06-09) Lam, W. Y.; Mackereth, R. W.; Mitchell, C. P. J.
Mercury (Hg) is a widespread contaminant known to pose severe risks to wildlife and human health. While Hg emissions have declined in recent decades, legacy emissions and stored Hg will continue to impact watershed Hg cycling for the foreseeable future. Boreal forests are a major concern due to their capacity for storing Hg, vulnerability to disturbance, and record of high Hg concentrations in fish. Thus, there is a need to better quantify factors that influence Hg export from boreal forest catchments to inform watershed management decisions regarding Hg. Streamflow measurements, as well as approximately bi-weekly sampling for total mercury (THg), methylmercury (MeHg), and supporting stream chemistry were completed in 19 headwater streams near Dryden, Ontario during the ice-free season of 2019. The results were related to landscape and hydrological indices to elucidate the potential factors governing THg and MeHg export across these catchments. This study shows that while Hg concentrations are relatively low (0.50–20.46 ng l−1 THg; < 0.04–1.21 ng l−1 MeHg) across boreal streams in south central Canada, there are significant differences in Hg export. Catchments within boreal shield landscapes dominated by shallow soils and exposed bedrock export more methylmercury than catchments within glaciolacustrine plain landscapes dominated by thicker sand deposits. Coniferous forest cover is more significant than dissolved organic matter concentrations and more reliable than available % wetland cover data, two metrics commonly included in Hg transport models, for predicting THg and MeHg loads. In the absence of substantial mapped wetland cover, wet forest cover, as defined by the proportion of catchment cover by tree species favoring wet conditions, is shown to be an effective alternative metric. Considering the generally detailed and extensive data on tree species coverage available in Canada’s managed forests, wet forest cover, in addition to coniferous forest cover, could be useful for modelling Hg transport in boreal forest watersheds.
Molecular correlations of dissolved organic matter with inorganic mercury and methylmercury in Canadian boreal streams
(Springer, 2022-06-09) Mangal, V.; Lam, W. Y.; Huang, H.; Emilson, E. J. S.; Mackereth, R. W.; Mitchell, C. P. J.
The molecular composition of dissolved organic matter (DOM) is increasingly recognized as fundamentally important to mercury transport and transformations, with numerous approaches undertaken to examine DOM characteristics beyond dissolved organic carbon concentrations. In this study, we use a high-resolution mass spectrometry approach, Fourier-transform ion cyclotron resonance mass spectrometry, to characterize DOM compound classes, DOM aromaticity (AImod), and the nominal oxygenation state of carbon (NOSC) across thirteen small boreal forest streams in central Canada. We then relate the relative abundance of hundreds of different DOM molecules with inorganic mercury and methylmercury (MeHg) concentrations across late spring and fall seasons. The number of significant correlations and the classes of DOM compounds significantly correlating with inorganic mercury and MeHg concentrations differs substantially across seasons and between mercury forms. For inorganic mercury, the abundance of nitrogen and sulfur containing DOM are most often positively correlated (mean ρ = 0.80) in the late spring, whereas during the fall, the abundance of low-oxidized lignins is more important, though with weaker correlations (mean ρ = 0.51). For MeHg, low-oxidized lignins and hydrolysable tannins, likely sourced from conifer throughfall and litter, account for up to 83% of all DOM-MeHg correlations regardless of season. Further network analyses reveal that the strongest and most significant inorganic mercury-DOM correlations are found across a wide range of NOSC values, indicating that DOM involved with the transport of inorganic mercury encompasses a wide range of polarities and thermodynamic stabilities. In contrast, DOM molecules exclusively correlated with MeHg concentrations have more positive NOSC and AImod values, implying the preferential transport of MeHg with more thermodynamically stable and aromatic DOM molecules. DOM molecules significantly correlated with both inorganic mercury and MeHg concentrations are found exclusively in the late spring. Overall, this non-targeted approach may help to inform further targeted investigations, especially as it relates to the underrepresented importance of plant biomolecules in facilitating mercury transport.

Browse

Recent Submissions