Direct Calorimetric Studies on the Heats of Ionization of Oxygenated and Deoxygenated Hemoglobin

Abstract The total heats of ionization, Qo and Qr, of bovine, human, and horse oxygenated and deoxygenated hemoglobin (O2Hb and Hb) have been directly measured by the rapid calorimetric method over the pH range from 5.7 to 9.0, at 12–28°. The most extensive determinations have been those on bovine hemoglobin: above about pH 6.6 the thermal titration curve for Hb lies systematically above that for O2Hb by about 600 cal, this difference presisting practically unchanged up to the most alkaline pH (8.7) studied. The two thermal titration curves cross at approximately pH 6.3, below which the O2Hb curve lies above the Hb curve by an increasing amount (up to 1,000 cal). The fact that Qr remains greater than Qo at pH 8.7, at which the absolute value of Qr is about 11,000 cal, implies that the heme-linked group, which ionizes in this pH range in the case of Hb, must have a heat of ionization, Qr, of around 11,000 cal. This figure, which was confirmed by an approximate method of calculation, lies outside the range usually attributed to the heat of ionization of imidazole or its derivatives. There is some indication, from a comparison of the difference between the two thermal titration curves for human Hb and O2Hb at approximately pH 7.3, that (Qr - Qo) is of the order of 4,000 cal, Qo being the heat of ionization of the corresponding heme-linked group in O2Hb. The results thus support the conclusions reached in the adjoining paper by Rossi-Bernardi and Roughton on the effect of temperature on the oxygen-linked ionizations of hemoglobin. The relation of the present studies to the cognate effects of pH on the heat of oxygenation of hemoglobin is briefly indicated

First validation of high-resolution satellite-derived methane emissions from an active gas leak in the UK

Atmospheric methane (CH4) is the second-most-important anthropogenic greenhouse gas and has a 20-year global warming potential 82 times greater than carbon dioxide (CO2). Anthropogenic sources account for ∼ 60 % of global CH4 emissions, of which 20 % come from oil and gas exploration, production and distribution. High-resolution satellite-based imaging spectrometers are becoming important tools for detecting and monitoring CH4 point source emissions, aiding mitigation. However, validation of these satellite measurements, such as those from the commercial GHGSat satellite constellation, has so far not been documented for active leaks. Here we present the monitoring and quantification, by GHGSat's satellites, of the CH4 emissions from an active gas leak from a downstream natural gas distribution pipeline near Cheltenham, UK, in the spring and summer of 2023 and provide the first validation of the satellite-derived emission estimates using surface-based mobile greenhouse gas surveys. We also use a Lagrangian transport model, the UK Met Office's Numerical Atmospheric-dispersion Modelling Environment (NAME), to estimate the flux from both satellite- and ground-based observation methods and assess the leak's contribution to observed concentrations at a local tall tower site (30 km away). We find GHGSat's emission estimates to be in broad agreement with those made from the in situ measurements. During the study period (March–June 2023) GHGSat's emission estimates are 236–1357 kg CH4 h−1, whereas the mobile surface measurements are 634–846 kg CH4 h−1. The large variability is likely down to variations in flow through the pipe and engineering works across the 11-week period. Modelled flux estimates in NAME are 181–1243 kg CH4 h−1, which are lower than the satellite- and mobile-survey-derived fluxes but are within the uncertainty. After detecting the leak in March 2023, the local utility company was contacted, and the leak was fixed by mid-June 2023. Our results demonstrate that GHGSat's observations can produce flux estimates that broadly agree with surface-based mobile measurements. Validating the accuracy of the information provided by targeted, high-resolution satellite monitoring shows how it can play an important role in identifying emission sources, including unplanned fugitive releases that are inherently challenging to identify, track, and estimate their impact and duration. Rapid, widespread access to such data to inform local action to address fugitive emission sources across the oil and gas supply chain could play a significant role in reducing anthropogenic contributions to climate change

Scientific Assessment of Ozone Depletion: 2010, Chapter 2 - Stratospheric Ozone and Surface Ultraviolet Radiation

As a result of the Montreal Protocol, ozone is expected to recover from the effect of ozone-depleting substances (ODSs) as their abundances decline in the coming decades. The 2006 Assessment showed that globally averaged column ozone ceased to decline around 1996, meeting the criterion for the first stage of recovery. Ozone is expected to increase as a result of continued decrease in ODSs (second stage of recovery). This chapter discusses recent observations of ozone and ultraviolet radiation in the context of their historical records. Natural variability, observational uncertainty, and stratospheric cooling necessitate a long record in order to attribute an ozone increase to decreases in ODSs. The primary tools used in this Assessment for prediction of ozone are chemistry-climate models (CCMs). These CCMs are designed to represent the processes determining the amount of stratospheric ozone and its response to changes in ODSs and greenhouse gases. Eighteen CCMs have been recently evaluated using a variety of process-based compari-sons to measurements. The CCMs are further evaluated here by comparison of trends calculated from measurements with trends calculated from simulations designed to reproduce ozone behavior during an observing period