Contribution of ephemeral wetlands to annual nitrous oxide flux from an agricultural landscape

Non-Peer ReviewedMeasurement of soil nitrous oxide emissions from soil in the Canadian Prairie Region rarely includes uncultivated ephemeral wetlands (UW) within agricultural landscapes. Accurate inventories and a better understanding spatial and temporal variability for soil N2O in agricultural terrains requires flux measurements from non-agricultural areas of the field. The purpose of this study was to measure soil nitrous oxide flux from an agricultural landscape that includes UW. Measurements were taken weekly and bi-weekly from July to October of 2003 and from March to October of 2004 and 2005. Cumulative emissions were highest from concave elements (cultivated ephemeral wetlands) (CV) elements in 2003 and 2004 and highest from the basin centers (BC) of UW in 2005. High flux events were associated with rainfall in 2003, and the recession of standing water at CV and BC elements in 2004 and 2005. However, there are differences between ephemeral wetlands in their emission response to water recession. Accounting for aerial extent of landscape units reveals that CV elements make greatest contribution to total yearly flux. Beneficial management practices intended to reduce annual emissions from this site should be designed to reduce emission from CV elements and UW should not be cleared for crop production. Sampling designs for measurement of emissions from UW need not distinguish between riparian grass and riparian tree elements within the UW

Impacts of tidal stream power on energy system security: An Isle of Wight case study

The new Energy System Model for Remote Communities (EnerSyM-RC) is implemented to quantify impacts from adopting tidal stream power alongside solar PV, offshore wind and energy storage in the Isle of Wight energy system. Based on scenarios with gross renewable energy generation matched to projected annual demand (equivalent to 136 MW mean power), installing 150 MW of solar PV, 150 MW of offshore wind, and 120 MW of tidal stream capacity maximises both supply–demand balancing and the magnitude of maximum power surplus, by 25% relative to the best performing solar+wind system. Tidal stream adoption also reduces total land/sea space by 33%. The economic viability of tidal stream capacity adoption is heavily dependent on the price of reserve energy; when the reserve energy price exceeds the average 2022 forward delivery contracts price (250 £/MWh), adopting tidal stream capacity reduces the levelised cost of whole-system energy relative to solar+wind systems. This tipping point, at which the whole-system levelised cost of energy is 92 £/MWh, occurs when the premium on tidal stream energy is outweighed by savings on reserve energy. In general these system benefits arising from tidal stream adoption are consistent over a range of different demand profiles, and in cases where gross annual renewable supply is oversized relative to demand

Impedance spectroscopy analysis of Ti n O 2n − 1 Magnéli phases

This letter presents a comprehensive impedance spectroscopy characterisation of Magnéli phases (Ti n O 2n − 1 ) over a range of temperatures, which are of interest in electrochemistry and sensing applications, with the aim to enhance the understanding of their electrical properties and influence their microstructure. The impedance of the Ti n O 2n − 1 can be resolved into two different contributions, namely the grain bulk (R B ) and grain boundaries (R GB ). The ac conductivity increases with frequency and temperature, following a universal power law. The high relative permittivity (10 5 -10 6 ), which is relatively frequency independent from 0.1 Hz to 100 kHz, is attributed to the presence of insulating grain boundaries (R GB NN R B ) creating an Internal Barrier Layer Capacitor (IBLC) effect. Above 100 kHz, the grain boundaries begin to contribute to the ac conductivity and the permittivity drops sharply