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We investigate the effect of partial dissolution on the transport of chemicals in sea ice. Physically plausible mechanisms are added to a brine convection model that decouples chemicals from convecting brine. The model is evaluated against a recent observational dataset where a suite of qualitatively similar chemicals (poly- and perfluoroalkylated substances, PFASs) with quantitatively different physico-chemical properties were frozen into growing sea ice. With no decoupling the model performs poorly – underestimating the measured concentrations of high-chain-length PFASs. A decoupling scheme where PFASs are decoupled from salinity as a constant fraction of their brine concentration and a scheme where decoupling is proportional to the brine salinity give better performance and bring the model into reasonable agreement with observations. A scheme where the decoupling is proportional to the internal sea-ice surface area performs poorly. All decoupling schemes capture a general enrichment of longer-chained PFASs and can produce concentrations in the uppermost sea-ice layers above that of the underlying water concentration, as observed. Our results show that decoupling from convecting brine can enrich chemical concentrations in growing sea ice and can lead to bulk chemical concentrations greater than that of the liquid from which the sea ice is growing. Brine convection modelling is useful for predicting the dynamics of chemicals with more complex behaviour than sea salt, highlighting the potential of these modelling tools for a range of biogeochemical research areas.

We investigate the effect of partial dissolution on the transport of chemicals in sea ice. Physically plausible mechanisms are added to a brine convection model that decouples chemicals from convecting brine. The model is evaluated against a recent observational dataset where a suite of qualitatively similar chemicals (poly- and perfluoroalkylated substances, PFASs) with quantitatively different physico-chemical properties were frozen into growing sea ice. With no decoupling the model performs poorly – underestimating the measured concentrations of high-chain-length PFASs. A decoupling scheme where PFASs are decoupled from salinity as a constant fraction of their brine concentration and a scheme where decoupling is proportional to the brine salinity give better performance and bring the model into reasonable agreement with observations. A scheme where the decoupling is proportional to the internal sea-ice surface area performs poorly. All decoupling schemes capture a general enrichment of longer-chained PFASs and can produce concentrations in the uppermost sea-ice layers above that of the underlying water concentration, as observed. Our results show that decoupling from convecting brine can enrich chemical concentrations in growing sea ice and can lead to bulk chemical concentrations greater than that of the liquid from which the sea ice is growing. Brine convection modelling is useful for predicting the dynamics of chemicals with more complex behaviour than sea salt, highlighting the potential of these modelling tools for a range of biogeochemical research areas.

Perfluoroalkyl acids (PFAAs) are synthetic chemicals with a variety of industrial and consumer applications that are now widely distributed in the global environment. Here, we report the measurement of six perfluorocarboxylates (PFCA, C4–C9) in a firn (granular compressed snow) core collected from a non-coastal, high-altitude site in Dronning Maud Land in Eastern Antarctica. Snow accumulation of the extracted core dated from 1958 to 2017, a period coinciding with the advent, use, and geographical shift in the global industrial production of poly/perfluoroalkylated substances, including PFAA. We observed increasing PFCA accumulation in snow over this time period, with chemical fluxes peaking in 2009–2013 for perfluorooctanoate (PFOA, C8) and nonanoate (PFNA, C9) with little evidence of a decline in these chemicals despite supposed recent global curtailments in their production. In contrast, the levels of perfluorobutanoate (PFBA, C4) increased markedly since 2000, with the highest fluxes in the uppermost snow layers. These findings are consistent with those previously made in the Arctic and can be attributed to chlorofluorocarbon replacements (e.g., hydrofluoroethers) as an inadvertent consequence of global regulation.

Climate change brings about significant changes in the physical environment in the Arctic. Increasing temperatures, sea ice retreat, slumping permafrost, changing sea ice regimes, glacial loss and changes in precipitation patterns can all affect how contaminants distribute within the Arctic environment and subsequently impact the Arctic ecosystems. In this review, we summarized observed evidence of the influence of climate change on contaminant circulation and transport among various Arctic environment media, including air, ice, snow, permafrost, fresh water and the marine environment. We have also drawn on parallel examples observed in Antarctica and the Tibetan Plateau, to broaden the discussion on how climate change may influence contaminant fate in similar cold-climate ecosystems. Significant knowledge gaps on indirect effects of climate change on contaminants in the Arctic environment, including those of extreme weather events, increase in forests fires, and enhanced human activities leading to new local contaminant emissions, have been identified. Enhanced mobilization of contaminants to marine and freshwater ecosystems has been observed as a result of climate change, but better linkages need to be made between these observed effects with subsequent exposure and accumulation of contaminants in biota. Emerging issues include those of Arctic contamination by microplastics and higher molecular weight halogenated natural products (hHNPs) and the implications of such contamination in a changing Arctic environment is explored.

The Arctic is undergoing unprecedented change. Observations and models demonstrate significant perturbations to the physical and biological systems. Arctic species and ecosystems, particularly in the marine environment, are subject to a wide range of pressures from human activities, including exposure to a complex mixture of pollutants, climate change and fishing activity. These pressures affect the ecosystem services that the Arctic provides. Current international policies are attempting to support sustainable exploitation of Arctic resources with a view to balancing human wellbeing and environmental protection. However, assessments of the potential combined impacts of human activities are limited by data, particularly related to pollutants, a limited understanding of physical and biological processes, and single policies that are limited to ecosystem-level actions. This manuscript considers how, when combined, a suite of existing tools can be used to assess the impacts of pollutants in combination with other anthropogenic pressures on Arctic ecosystems, and on the services that these ecosystems provide. Recommendations are made for the advancement of targeted Arctic research to inform environmental practices and regulatory decisions.

Over the years, oil has been the major source of revenue in Nigeria. Agriculture has been recommended as an alternative viable option, for this to be achieved the sustainable use of pesticides has to be key. Pesticides are used by farmers to ward off pests in farms, however it has been reported that these pesticides are inappropriately used which could adversely affect the environment and could potentially endanger humans exposed to them through their consumption of fruits and vegetables. This research aimed to investigate pesticide use among farms and its impact on the environment. 486 farmers in Akwa Ibom state were interviewed and 185 farmers representing the geo political zones of the country were equally interviewed. Field observations were also done and among other things, it revealed some farmers did not receive training on pesticide application. Soil samples were analysed to ascertain their levels of concentrations. It was found that pesticides usage is high as almost every farmer made use of pesticides, the chemicals were mostly misused. Farmers are constantly exposed to chemicals and levels of concentration of the pesticides were generally within the maximum residue levels and below the WHO recommended maximum limits and impliedly did not pose any significant threats. There is also a tendency that the area considered as ‘non-farm’ is not the case as some sections of those areas used to have farms situated in them and may not reflect the current practice, hence reasons for of the concentration levels found therein. The reported concentrations of the metabolites of DDT suggest that it is from either historical usage or the illegal usage of these pesticides or even a case of both factors. The research showed that most farmers did not receive training on pesticide application and the authorities mandated with carrying out enforcement in this regard by regulating the way it is used, need to do more.

Climate change brings about significant changes in the physical environment in the Arctic. Increasing temperatures, sea ice retreat, slumping permafrost, changing sea ice regimes, glacial loss and changes in precipitation patterns can all affect how contaminants distribute within the Arctic environment and subsequently impact the Arctic ecosystems. In this review, we summarized observed evidence of the influence of climate change on contaminant circulation and transport among various Arctic environment media, including air, ice, snow, permafrost, fresh water and the marine environment. We have also drawn on parallel examples observed in Antarctica and the Tibetan Plateau, to broaden the discussion on how climate change may influence contaminant fate in similar cold-climate ecosystems. Significant knowledge gaps on indirect effects of climate change on contaminants in the Arctic environment, including those of extreme weather events, increase in forests fires, and enhanced human activities leading to new local contaminant emissions, have been identified. Enhanced mobilization of contaminants to marine and freshwater ecosystems has been observed as a result of climate change, but better linkages need to be made between these observed effects with subsequent exposure and accumulation of contaminants in biota. Emerging issues include those of Arctic contamination by microplastics and higher molecular weight halogenated natural products (hHNPs) and the implications of such contamination in a changing Arctic environment is explored.

Poly- and perfluoroalkyl substances (PFAS) are contaminants of emerging Arctic concern and are present in the marine environments of the polar regions. Their input to and fate within the marine cryosphere are poorly understood. We conducted a series of laboratory experiments to investigate the uptake, distribution, and release of 10 PFAS of varying carbon chain length (C4–C12) in young sea ice grown from artificial seawater (NaClsolution). We show that PFAS are incorporated into bulk sea ice during ice formation and regression analyses for individual PFAS concentrations in bulk sea ice were linearly related to salinity (r2 = 0.30 to 0.88, n = 18, p < 0.05). This shows that their distribution is strongly governed by the presence and dynamics of brine (high salinity water) within the sea ice. Furthermore, long-chain PFAS (C8–C12), were enriched in bulk ice up to 3-fold more than short-chain PFAS (C4–C7) and NaCl. This suggests that chemical partitioning of PFAS between the different phases of sea ice also plays a role in their uptake during its formation. During sea ice melt, initial meltwater fractions were highly saline and predominantly contained short-chain PFAS, whereas the later, fresher meltwater fractions predominantly contained long-chain PFAS. Our results demonstrate that in highly saline parts of sea ice (near the upper and lower interfaces and in brine channels) significant chemical enrichment (ε) of PFAS can occur with concentrations in brine channels greatly exceeding those in seawater from which it forms (e.g., for PFOA, εrinebrine = 10 ± 4). This observation has implications for biological exposure to PFAS present in brine channels, a common feature of first-year sea ice which is the dominant ice type in a warming Arctic.

Persistent organic pollutants (POPs) are a highly diverse group of synthetic chemicals that are released into the environment from human activities and display a host of adverse effects in wildlife and humans. Perfluoroalkylated substances (PFASs) are one major group of industrial chemicals that are globally produced in vast quantities and are subject to various global regulations. However, PFASs are present in the Earth’s Polar Regions and yet little is known about their environmental fate and behaviour, particularly their accumulation and fate in snow and ice and the wider cryosphere. Moreover, climate change is altering the cryosphere, affecting sea ice and its properties for example, which in turn may affect the biogeochemical cycling of these pollutants and could lead to altered or enhanced biological exposure and uptake. This thesis examines the accumulation of PFASs in snow and firn as a useful recorder of environmental contamination in Antarctica, a region which lacks a multi-decadal time series of air monitoring data. The thesis also investigates in detail the processes that result in the uptake, distribution and accumulation of persistent organic pollutants in sea ice, particularly in the context of a warmer Arctic, where sea ice is now dominated by brine-rich single season ice. There is a lack of monitoring data on the levels of PFASs in Antarctica, and so a snow core was taken from Kohnen Station (East Antarctica plateau) to determine the historical deposition rates in the region. Results revealed low or non-detectable levels of perfluorosulfonic acids (PFSAs) but showed increasing trends of perfluorocarboxylates (PFCAs) between 1958 – 2017. Deposition rates for PFCAs in snow varied depending on chain length, with PFBA (C4) showing up to 2-orders of magnitude higher (1.3 and 280 ng m-2 yr-1) than PFOA (C8) (1.6 and 12.6 ng m-2 yr-1). Furthermore, correlations between PFCAs of varying chain length were strong (r2 > 0.7, p < 0.01). This information suggest

Context : Chemical risk assessment has traditionally been dependent on “narrative” approaches for synthesising evidence about potential health harms from exposure to chemical substances. However, narrative reviews are recognised as being vulnerable to a range of methodological shortcomings which introduce bias and inconsistency into the summarisation of scientific evidence. This is likely to be a contributing factor in a number of controversies about the safety of chemical substances. The potential value of systematic review methods for improving the transparency and validity of chemical risk assessments was arguably first articulated in the mid-2000s. By 2015, the first major frameworks for conducting systematic reviews of environmental health evidence had been published. What was not well understood at the time was how systematic review, as a technically exacting methodology originally developed for evaluating the effectiveness of interventions in healthcare, might be adapted to the specific workflows and evidence streams of chemical risk assessment. Objectives : The aim of this Thesis is to investigate how systematic review methods can be applied to the conduct of chemical risk assessment. This overall aim is broken down into four specific objectives: to identify practical challenges and knowledge gaps which impede the implementation of systematic review methods in chemical risk assessment; to define a consensus view on key recommended practices for the planning and conduct of systematic reviews in the environmental health sciences; to examine how “biological plausibility” as a concept fundamental to risk assessment is accommodated in systematic review methodologies; and to describe the role of ontologies in making evidence accessible for use in systematic chemical assessments. Discussion : The use of systematic review methods should improve the validity, utility and transparency of chemical risk assessments. However, the successful implementation of systematic r

Amphibians are undergoing large population declines in many regions around the world. As environmental pollution from both agricultural and urban sources has been implicated in such declines, there is a need for a biomonitoring approach to study potential impacts on this vulnerable class of organism. This study assessed the use of infrared (IR) spectroscopy as a tool to detect changes in several tissues (liver, muscle, kidney, heart and skin) of late-stage common frog (Rana temporaria) tadpoles collected from ponds with differing water quality. Small differences in spectral signatures were revealed between a rural agricultural pond and an urban pond receiving wastewater and landfill run-off; these were limited to the liver and heart, although large differences in body size were apparent, surprisingly with tadpoles from the urban site larger than those from the rural site. Large differences in liver spectra were found between tadpoles from the pesticide and nutrient impacted pond compared to the rural agricultural pond, particularly in regions associated with lipids. Liver mass and hepatosomatic indices were found to be significantly increased in tadpoles from the site impacted by pesticides and trace organic chemicals, suggestive of exposure to environmental contamination. Significant alterations were also found in muscle tissue between tadpoles from these two ponds in regions associated with glycogen, potentially indicative of a stress response. This study highlights the use of IR spectroscopy, a low-cost, rapid and reagent-free technique in the biomonitoring of a class of organisms susceptible to environmental degradation., V mnoha oblastech světa dochází k velkému poklesu populací obojživelníků. Jelikož se za příčinu tohoto poklesu považuje znečištění životního prostředí jak ze zemědělských, tak z městských zdrojů, existuje potřeba biomonitoringu sloužícího studiu potenciálních dopadů na tuto zranitelnou skupinu organismů. Tato práce posuzuje užití IČ spektroskopie jako nástroje detekce změn ve tkáních (játra, svaly, ledviny, srdce a kůže) pulců skokana hnědého (Rana temporaria) v pozdních fázích vývoje, kteří byly odebráni z vodních nádrží s různou kvalitou vody. Malé rozdíly byly shledány mezi nádržemi venkovského zemědělství a městskými nádržemi, do kterých přitékají odpadní vody a odtoky ze skládek; tyto rozdíly byly omezeny na játra a srdce, ačkoliv byly zjevné velké rozdíly ve velikosti pulců, překvapivě pulci z městských nádrží byli větší než pulci z venkovských nádrží. Větší rozdíly ve spektrech jater byly nalezeny mezi pulci z nádrží zatížených pesticidy a živinami ve srovnání s venkovskými nádržemi. Hmotnost jater a hepatosomatické indikátory byly významně zvýšené u pulců z nádrží znečištěných pesticidy a stopovými organickými chemikáliemi, což naznačuje vystavení kontaminaci životního prostředí.Významné změny byly též nalezeny ve svalových tkáních u pulců z těchto dvou nádrží, v částech spojených s glykogenem, což potenciálně indikuje reakci na stress. Tato práce vyzdvihuje využití IČ spektroskopie, levné a rychlé analytické techniky biomonitoringu třídy organismů ovlivněných degradací životního prostředí.

Systematic evidence mapping offers a robust and transparent methodology for facilitating evidence-based approaches to decision-making in chemicals policy and wider environmental health. Interest in the methodology is growing; however, its application in environmental health is still novel. To facilitate the production of effective systematic evidence maps for environmental health use cases, we survey the successful application of evidence mapping in other fields where the methodology is more established. Focusing on issues of “data storage technology”, “data integrity”, “data accessibility”, and “transparency”, we characterise current evidence-mapping practice and critically review its potential value for environmental health contexts. We note that rigid, flat data tables and schema-first approaches dominate current mapping methods and highlight how this practice is ill-suited to the highly connected, heterogeneous and complex nature of environmental health data. We propose this challenge is overcome by storing and structuring data as “knowledge graphs”. Knowledge graphs offer a flexible, schemaless and scalable model for systematically mapping the environmental health literature. Associated technologies such as ontologies are well-suited to the long-term goals of systematic mapping methodology in promoting resource-efficient access to the wider environmental health evidence base. Several graph storage implementations are readily available, with a variety of proven use cases in other fields. Thus, developing and adapting systematic evidence mapping for environmental health should utilise these graph-based resources to ensure the production of scalable, interoperable and robust maps to aid decision-making processes in chemicals policy and wider environmental health.

Chemicals policy is designed to protect human and ecological health from the adverse effects that can result from exposure to manufactured chemical substances. It entails a complex process of regulatory chemical risk assessment and risk-management decision-making, drawing expertise from a diverse range of fields including toxicology and environmental health. However, these decision-making processes have come under increased scrutiny in recent years – criticized for bias, lack of transparency, rigor and a failure to identify unacceptable risks before widespread exposure occurs. This has resulted in calls for a more “evidence-based” approach, in which all relevant, available evidence is analyzed in a robust, transparent and reproducible manner. There is thus a growing need to incorporate methodological frameworks capable of facilitating evidence-based approaches to chemical risk assessment and regulatory decision-making. Such frameworks have been successfully developed in the field of medicine, which underwent a similar paradigm shift to that currently shaping chemical risk assessment, in the early 1990s. The gold-standard for evidence-based decision-making championed by the evidence-based medicine movement takes the form of systematic review. Systematic review describes a prescriptive and transparent method for collating, appraising and analyzing all available, relevant evidence in answer to a specific research question. By pooling the results of individual (independent) studies, systematic reviews synthesize conclusions which are not only more precise but are representative of an entire evidence-base. Now well established within clinical decision-making, the application of systematic review to chemical risk assessment is beginning to gain prominence. However, several challenges and barriers threaten to slow the uptake and quality of systematic review for chemical risk assessment. These include the prohibitively narrow focus of systematic reviews, which are at odds w