Functional Principal Component Analysis for Non-stationary Dynamic Time Series

Motivated by a highly dynamic hydrological high-frequency time series, we propose time-varying Functional Principal Component Analysis (FPCA) as a novel approach for the analysis of non-stationary Functional Time Series (FTS) in the frequency domain. Traditional FPCA does not take into account (i) the temporal dependence between the functional observations and (ii) the changes in the covariance/variability structure over time, which could result in inadequate dimension reduction. The novel time-varying FPCA proposed adapts to the changes in the auto-covariance structure and varies smoothly over frequency and time to allow investigation of whether and how the variability structure in an FTS changes over time. Based on the (smooth) time-varying dynamic FPCs, a bootstrap inference procedure is proposed to detect significant changes in the covariance structure over time. Although this time-varying dynamic FPCA can be applied to any dynamic FTS, it has been applied here to study the daily processes of partial pressure of CO2 in a small river catchment in Scotland

Micro- and nanoplastic pollution of freshwater and wastewater treatment systems

Plastic waste is a widespread and persistent global challenge with negative impacts on the environment, economy, human health and aesthetics. Plastic pollution has been a focus of environmental research over the past few decades, particularly in relation to macroplastics that are easily visible by the naked eye. More recently, smaller plastic waste at the micro- and nanoscale has become of increasing concern, resulting in extensive investment in research to advance knowledge on the sources, distribution, fate and impact of these materials in aquatic systems. However, owing to their small sizes and a lack of unified methods, adequate quantitative and qualitative assessment has been difficult. Furthermore, most of the microplastic surveys available to date have focussed in the marine environment while scarce knowledge exists of freshwater systems. Because the majority of marine debris originates on land, the role of wastewater treatment systems and natural fluvial vectors in delivering these emerging contaminants to the environment should be explored. Considering fundamental aspects pertaining to microplastic sources, distribution, mobility and degradation in these systems is crucial for developing effective control measures and strategies to mitigate the discharge of these particles to the sea

Hydraulics are a first order control on CO2 efflux from fluvial systems

Evasion of carbon dioxide (CO2) from fluvial systems is now recognized as a significant component of the global carbon cycle. However the magnitude of, and controls on, this flux remain uncertain and improved understanding of both are required to refine global estimates of fluvial CO2 efflux. CO2 efflux data show no pattern with latitude suggesting that catchment biological productivity is not a primary control and that an alternative explanation for inter-site variability is required. It has been suggested that increased flow velocity and turbulence enhance CO2 efflux, but this is not confirmed. Here, using contemporaneous measurements of efflux (range: 0.07 – 107 µmol CO2 m-2 s-1), flow hydraulics (mean velocity range: 0.03 – 1.39 m s-1) and pCO2 (range: 174 – 10712 µatm) at six sites, we find that flow intensity is a primary control on efflux across two climatically different locations (where pH is not a limiting factor) and that the relationship is refined by incorporating the partial pressure of CO2 (pCO2) of the water. A remaining challenge is how to upscale from point to reach or river basin level. Remote imaging or river surface may be worth exploring if subjectivity in interpreting surface state can be overcome

Fluvial dissolved organic carbon composition varies spatially and seasonally in a small catchment draining a wind farm and felled forestry

Assessing whether land use, from activities such as wind farm construction and tree-felling, impacts on terrestrial C delivery to rivers has focused on quantifying the loss of dissolved organic carbon (DOC), and not the composition changes. Here we explore how land use influences DOC composition by considering fluvial DOC concentration, [DOC], and spectrophotometric composition of a river draining a peat-rich catchment. We find that in this 5.7 km2 catchment differences occur in both the concentration and composition of the DOC in its sub-catchments. This is attributed to differences in how land was used: one tributary (D-WF) drains an area with wind farm construction and forestry in the headwaters, and one tributary (D-FF) drains an area with felled plantation trees. Generally, [DOC] in both streams showed similar seasonal variation, and autumn maxima. However, the felled catchment had greater mean [DOC] than the wind farm catchment. The SUVA254 and E4/E6 indicated DOC in both streams had similar aromaticity and fulvic:humic acid for most of the time, but SUVA410 and E2/E4 indicated less DOC humification in the felled catchment. This may be due to young DOC from the breakdown of residual branches and roots, or more humification in soils in the wind farm area. During the dry months, DOC composition showed more spatial variation: the D-WF DOC had smaller SUVA254 (less total aromatic material) and SUVA410 (fewer humic substances). The decreased E2/E4 in both streams indicated the total aromatic carbon decreased more than humic substances content. Moreover, the larger E4/E6 for D-WF in summer indicated that the humic substances were richer in fulvic acids than humic acids. Soil disturbance associated with forestry-felling likely contributed to the higher [DOC] and release of less-humified material in D-FF. This research indicates drivers of diff

Stable Isotopic Studies of Bacteriogenic Methane Emissions

Methane is produced thermogenically from organic matter, associated with oil and coal production, and bacteriogenically by two main biochemical pathways, CO2 reduction and acetoclastic methanogenesis (commonly known as fermentation), CH4 emissions can be an environmental problem on a local scale, due to the explosive potential of CH4, and on a global scale as it is an effective radiatively forcing greenhouse gas, with continued emissions to the atmosphere contributing to potential global warming. Stable isotopic characterisation of sources can be used, when monitoring the composition of atmospheric CH4 and its secular trend, to provide constraints on the relative magnitude of fluxes (Stevens, 1988). The overall flux isotopic composition should correspond to the isotopic composition of the gas in the atmosphere, once fractionation associated with atmospheric loss processes has been accounted for (Stevens and Engelkemeir, 1988). At present, delta13C characterisation of CH4 sources is well established. By comparison, deltaD characterisation of global sources of CH4 is poorly established and the atmospheric chemistry complex. This research utilised stable isotope analyses of bacteriogenic CH4 to constrain the isotopic signature of both carbon and hydrogen, and, where possible, to understand the factors controlling that signature. (Abstract shortened by ProQuest.)

MLibrary Website - Quick Links Guerilla Test

The library website gateway includes a group of links on the bottom (footer) of each page called “Quick Links.” These links are meant to provide convenient access to some of the most frequently used and/or most requested links related to both library and university business. The goals of this test were to determine if the labels for both the group and each link within the group were clear, and whether the links included in this grouping were what users want and need.Usability GroupUsability Task Forcehttp://deepblue.lib.umich.edu/bitstream/2027.42/106787/1/QuickLinks.pd

Knowledge management across the environment-policy interface in China: What knowledge is exchanged, why, and how is this undertaken?

Global to local environmental policy-making is increasingly evidenced-based. Knowledge management (KM) is increasingly used by environmental scientists and policymakers, to deliver evidence-based policy and practice. There is thus an urgent need to identify whether and how knowledge is exchanged between knowledge producers and users in environmental science fields. Here we apply an assessment framework developed in social medicine to identify what forms of environmental knowledge are exchanged, and why and how they are exchanged. We focussed on China, as international research to better manage Chinese ecosystem services is rapidly-increasing, yet, how to best integrate this into political decision-making and the public realm remains a challenge. How KM is practiced in China is unknown. We addressed this through: 1) a systematic analysis of published KM research in China compared to global trends; 2) evaluating KM for environmental policy and management in China; 3) quantitative surveys of Chinese (n = 72) and British (n = 16) scientists researching Chinese environmental problems. The systematic literature review of two databases identified two key findings. One, of 291 papers that considered KM there were no papers in the environmental sector examining the science-policy-practice interface in China. Two, only 13 of 423 potentially relevant papers explicitly examined KM for environmental topics, notably for agriculture and information exchange (the 'What?'). Most papers reported a one-way interaction between scientists and users (the 'How?'), used to change practice (the 'Why?'). Our survey showed significantly-less awareness and use of two-way knowledge exchange (KE) methods by Chinese scientists. The paucity of documented KM research and limited evidence for two-way interaction show KE at the environmental science-policy-practice interface in China is limited. Promotion of KE practice may benefit environmental policy-making in China. We have also shown that conceptual frameworks for mapping and assessing KE practice from social medicine can be usefully adapted for examining environmental science – policy interfaces

Microscopy and elemental analysis characterisation of microplastics in sediment of a freshwater urban river in Scotland, UK

Understanding of the sources, fate, and impact of microplastics (MPs, < 5 mm) remains limited, particularly in freshwater environments, while limited comparability across available surveys hinders adequate monitoring and risk assessment of these contaminants. Here, the distribution of microscopic debris in an urban river close to the marine environment in the West of Scotland was investigated to assess concentration and distribution of primary and secondary MPs. Also, the efficiency of light and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) was evaluated for characterisation and quantification of MPs sized 2.8 mm–11 μm. Bank sediment samples were collected twice from the River Kelvin in Glasgow and were size-fractionated and processed for extraction of MPs by density separation. Sample MPs spiking and use of procedural blanks allowed the influence of processing on field data quality to be considered. Total abundances were 161–432 MPs kg−1 dry sediment, with fibres as the dominant type, comprising > 88% of total counts. Nevertheless, fibres in blanks suggest potential contributions from atmospheric contamination. Moreover, fibres concentrated mainly in fractions < 0.09 mm suggesting that their fate may be influenced by drivers of fine sediment dynamics in rivers. While no primary MPs were observed, metallic and glass pellets were present in high abundances in settled material and could be easily misidentified by visual inspection, demonstrating that compositional analysis is needed to avoid analytical errors from MP misidentification and overestimation. SEM-EDS allowed for a quick screening of plastic vs non-plastic pellets and improved identification of smaller fragments, whereas more advanced techniques are needed for proper identification of fibres. This study is the first to report on MPs in freshwater rivers in Scotland and suggests that diffuse sources of pollution may be delivering secondary MPs to the river. Their sources, fate, and risk in these systems will thus warrant further attention

Biotic and abiotic factors interact to regulate Northern peatland carbon cycling

Understanding the spatio-temporal variability of controls on peatland carbon (C) cycling is essential to project the effects of future environmental change. While there is understanding of individual drivers of C cycling, the effect of multiple drivers, including interactions, remains poorly understood. Using a spatially and temporally explicit sampling framework, we examined the effects of biotic and abiotic controls on key indicators of peatland functioning: ecosystem respiration (R (eco)), photosynthesis (P (cal)), net ecosystem exchange (NEE), methane (CH4) fluxes, and pore water dissolved organic carbon concentration ([DOC]). Measurements were made over 12 months in a blanket peatland hosting a wind farm in Scotland, UK. Overall, we found that (i) season and plant functional type (PFT) explained most variation in R (eco) and P (cal), (ii) PFT and spatial location within the wind farm, which integrates several peat properties, were dominant predictors of CH4 fluxes, and (iii) season and location within the wind farm correlated with pore water [DOC]. Examination of predictors indicated that interactions, between and within biotic and abiotic factors, explained a significant amount of variation in greenhouse gas fluxes and [DOC]. These findings indicate that combinations of biotic and abiotic factors could mediate or exacerbate the effects of future environmental change on peatland C cycling. Given this, studies of C cycling need to capture the spatial and temporal variance of biotic and abiotic factors and their interactions to project the likely impacts of environmental change

Ground-level climate at a peatland wind farm in Scotland is affected by wind turbine operation

The global drive to produce low-carbon energy has resulted in an unprecedented deployment of onshore wind turbines, representing a significant land use change for wind energy generation with uncertain consequences for local climatic conditions and the regulation of ecosystem processes. Here, we present high-resolution data from a wind farm collected during operational and idle periods that shows the wind farm affected several measures of ground-level climate. Specifically, we discovered that operational wind turbines raised air temperature by 0.18 °C and absolute humidity (AH) by 0.03 g m−3 during the night, and increased the variability in air, surface and soil temperature throughout the diurnal cycle. Further, the microclimatic influence of turbines on air temperature and AH decreased logarithmically with distance from the nearest turbine. These effects on ground-level microclimate, including soil temperature, have uncertain implications for biogeochemical processes and ecosystem carbon cycling, including soil carbon stocks. Consequently, understanding needs to be improved to determine the overall carbon balance of wind energy