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The emissivity of a surface is a measure of the amount of radiation that surface emits at a given temperature. Knowledge of the emissivity of the Earth’s surface is vitally important for the prediction of future climate. The emissivity of a surface is dependent on wavelength, material type, surface properties (such as roughness) and temperature, making it difficult to model. This means physical measurements are required to characterise surface emissivity. The emissivity of important surface types, including ocean, ice, and desert, are well known in the mid-infrared (wavelengths 8 to 15 microns) however only 2 measurements have been made of emissivity in the far-infrared (wavelengths longer than 15 microns), even though the far-infrared makes up around 50% of the outgoing radiation from Earth. Previously, it had been thought that far-infrared emissivity did not have a large impact on the global climate, as surface radiation from this portion of the spectrum was mostly absorbed by atmospheric water vapour. However recent modelling studies have indicated that this is not the case and including realistic far-infrared emissivity values can reduced observed biases in global climate models. It is therefore important to have accurate measurements of far-infrared emissivity for a variety of surface types. To address this lack of measurements, we are developing a spectrometer that will make in-situ measurements of emissivity in the far-infrared.
10:15 Harry Frost: Microplastic Fibres: Generation, Transport and Interactions with Metals
The laundering of synthetic textiles has been highlighted as a diffuse source of microplastic (< 5 mm length) fibre pollution. Up to 6,000,000 synthetic fibres can be shed from an average wash, and are transported to wastewater treatment plants via wastewater systems. Up to 99.9% of fibres are retained in the sewage sludge, which is often applied to agricultural land, providing a pathway for microplastic fibres to enter soils. During wastewater treatment, fibres are exposed to elevated concentrations of potentially toxic metals, which may sorb (attach) to the fibre surfaces and be transported to agricultural soils.
Our research aims to investigate the mechanisms influencing the adsorption of these elements to microplastic fibres. Polyester fabric was milled to produce microplastic fibres. Fibres were shaken with metal solutions to calculate the concentration of metal sorbed onto the fibres. Fibre-metal interaction time was varied from 5-360 minutes to investigate the kinetics of the sorption of mercury, cadmium, and lead. After shaking, suspensions were filtered, and metal concentrations were determined by ICP-MS.
Sorption was highest for mercury, followed by lead and then cadmium. For mercury and lead, initial sorption was very rapid, followed by a plateau after approximately 3 hours. Mercury sorption reached 16 µg/g at equilibrium. Fabric rinsing revealed significant leaching of antimony, probably due to the use of antimony trioxide as a catalyst in polyester production. These findings suggest polyester has the capacity to rapidly adsorb toxic metals such as mercury and lead in wastewater, which may alter metal bioavailability to soil organisms. Pristine fabrics may also act as a diffuse source of antimony. Further work aims to construct isotherms describing the adsorption of these metals to polyester fibres over a range of pH values, and to use microcosm studies to investigate the bioavailability of polyester-bound mercury to earthworms.
10:30 Sam Willard: Organic carbon storage along a nitrogen deposition gradient
Soil plays a major role in the cycling of water and nutrients, thereby impacting plant productivity and the turnover of soil organic matter (SOM), which represents a larger carbon pool than the atmosphere and vegetation combined. Long term storage of SOM is largely controlled by the soil microbial community and can influence plant productivity. SOM stocks are characterized by the accessibility of organic compounds to microbes. Quantifying the turnover of POM to MAOM and its chemical stability is extremely informative for predicting the residence time of soil C and understanding its regulators. Because of its fertilization property for microbes and plants, known quantities of deposited N could be used to predict POM build-up and turnover rates. Efforts to distinguish the effects of N addition on microbial decomposition in field studies have only added more uncertainty. SOM levels have been shown to lessen upon N fertilization at some sites while other studies found slowed microbial respiration and accumulation of SOM upon addition of inorganic N, indicating less SOM turnover. Measuring POM and MAOM levels as a function of N availability could be informative for quantifying SOM stability and longevity. Given the scope of global N deposition and the presence of accurate georeferenced datasets, exploring the dynamics through which it impacts SOM storage could be extremely consequential for C modelling and land management. Through my research, I am exploring the storage of SOM and soil microbial dynamics along a N deposition gradient in the UK.