Derivation of a conservation equation for mean molecular weight for a two-constituent gas within a three-dimensional,time-dependent model of the thermosphere

Systematic circulation systems within the thermosphere create major departures of composition of both major and minor species from diffusive equilibrium. For example, latitudinal gradients in the mixing ratios of major and minor species in recent empirical models of the Earth's thermosphere are inconsistent with changes of the thermal structure alone or with temporal or spatial changes of the turbopause altitude. A conservation equation describing the time rate of change of mean molecular weight is derived for a two-species gas, in the presence of molecular and turbulent diffusion and general global circulation. The equation is fully three-dimensional and time-dependent and is derived from a combination of the general diffusion equation and the time-dependent continuity equation. In the Earth's thermosphere, the two species are [O] the light species and [N₂,O₂] the heavy species and the approach is valid since the time constants of dissociation of [O₂] and recombination of [O] are long compared with typical dynamical time constants. One of the major effects of allowing a wind-driven departure from diffusive equilibrium is that, at the solstice, the pole to pole exospheric temperature difference is increased by more than 50%, while the prevailing summer to winter meridional wind actually decreases. A conservation equation of this kind has general application to any planetary atmosphere which may be considered to be predominantly comprised of two species. Results for a three-dimensional, time-dependent thermospheric model for solstice conditions are presented for the conditions of solar heating only. The model results are compared with previous model results with composition fixed at pressure levels and with empirical temperature and composition models of MSIS.     

Greenhouse gas emissions from a managed grassland

Managed grasslands contribute to global warming by the exchange of the greenhouse gases carbon dioxide, nitrous oxide and methane. To reduce uncertainties of the global warming potential of European grasslands and to assess potential mitigation options, an integrated approach quantifying fluxes from all three gases is needed. Greenhouse gas emissions from a grassland site in the SE of Scotland were measured in 2002 and 2003. Closed static chambers were used for N₂O and CH₄ flux measurements, and samples were analysed by gas chromatography. Closed dynamic chambers were used for soil respiration measurements, using infrared gas analysis. Three organic manures and two inorganic fertilizers were applied at a rate of 300 kg N ha⁻¹ a⁻¹ (available N) and compared with a zero-N control on grassland plots in a replicated experimental design. Soil respiration from plots receiving manure was up to 1.6 times larger than CO₂ release from control plots and up to 1.7 times larger compared to inorganic treatments (p<0.05). A highly significant (p<0.001) effect of fertilizer and manure treatments on N₂O release was observed. Release of N₂O from plots receiving inorganic fertilizers resulted in short term peaks of up to 388 g N₂O–N ha⁻¹ day⁻¹. However losses from plots receiving organic manures were both longer lasting and greater in magnitude, with an emission of up to 3488 g N₂O–N ha⁻¹ day⁻¹ from the sewage sludge treatments. During the 2002 growing season the cumulative total N₂O flux from manure treatments was 25 times larger than that from mineral fertilizers. CH₄ emissions were only significantly increased (p<0.001) for a short period following applications of cattle slurry. Although soil respiration in manure plots was high, model predictions and micrometeorological flux measurements at an adjacent site suggest that all plots receiving fertilizer or manure acted as a sink for CO₂. Therefore in terms of global warming potentials the contribution of N₂O from manure treatments becomes particularly important. There were considerable variations in N₂O and CO₂ fluxes between years, which was related to annual variations in soil temperature and rainfall.     

Evidence on neutron star structure from pulsars and related objects

Properties of pulsars and binary X-ray sources which seem particularly relevant to theories of neutron star structure and strong magnetic fields are reviewed and discussed.Paper presented at the Symposium on Solid State Astrophysics, held at the University College, Cardiff, Wales, between 9–12 July, 1974.     

Irrelevant economics: The water pricing and pollution charging debate

Conventional economic appraisals of the water industry have concentrated on economic efficiency defined almost entirely in allocative terms, the key issues being the efficiency with which available water resources are allocated between users and with which factors of production are invested in new facilities. Since marginal cost pricing has been viewed as the mechanism theoretically capable of bringing about optimality in resource allocation, assessments of water industry practices have all too often been reduced to reiteration of the extent to which current pricing practices diverge from the theoretical optima. This paper, based on empirical work on water suppliers in both Britain and Australia, questions the relevance of this conventional approach.First, it is argued that the concentration on allocative efficiency has diverted attention from the equally crucial issue of whether the industry is efficient in managerial, technical and product terms. Since technological efficiency must exist in an industry before a Pareto optimal allocation of resources can occur, the presupposition, in papers which argue that the introduction of optimal pricing rules will ensure allocative efficiency, must be that the industry is already producing an appropriate product using least cost production methods. No such presupposition can be made in an industry where the profit motive and competitive forces do not operate.Second, it is argued that optimal pricing policies can only produce optimal resource allocations if consumers act in a prescribedly rational way to the prices set. Although it is well known that ‘second-best’ pricing rules may be needed to counter inefficient conditions prevailing in other sectors of the economy, the effect of market imperfec- tions on the way consumers react to prices has been less well analysed. Using results from a study of firms' reactions to trade effluent charges, it is shown that the structure of companies and the way they operate their revenue and capital budgets may severely limit the effectiveness of the price mechanism in ensuring allocative efficiency.Finally, the paper considers the ‘equity’ with which the costs of water services are distributed between consumers. Once again it is argued that the issue has been neglected since the distribution of income is irrelevant to the achievement of allocative optimality in Paretian terms. Evidence is presented that contradicts the popular myth that, although current pricing arrangements may be less than efficient, they are at least ‘broadly fair’. It is shown that, in practice, price discrimination against low income consumers is widespread, and this can hardly be regarded as equitable, whatever definition of equity is used.     

The geography of age

"This article examines the geography of age across the counties of England and Wales and the regions of Scotland [and in Northern Ireland]." Sections are included on national and subnational age structures and on spatial patterns for childhood ages, working ages, and retired ages.     

云南个旧卡房铜矿床地质地球化学特征及其成因探讨

云南个旧是世界上最大的锡多金属矿田,卡房铜矿是个旧矿田主要的产铜区。卡房铜矿主要的矿床类型有两类:玄武岩层中或玄武岩与大理岩层间的似层状矿体以及花岗岩与围岩接触带矿体。围岩蚀变主要有夕卡岩化、阳起石化和金云母化。电子探针分析结果显示,卡房铜矿夕卡岩中的辉石主要为透辉石-钙铁辉石系列,石榴子石端元组分以钙铝榴石-钙铁榴石为主。流体包裹体及氢、氧同位素研究显示,从主成矿期到后成矿期,流体温度有显著降低(从260～360℃到160～280℃),而流体盐度则基本保持不变(从1.74%～12.51%到1.74%～11.93%)。氢、氧同位素组成表明,早期成矿流体主要以岩浆水为主,而晚期成矿流体可能在上升过程中与地层中的大气降水相混合。硫同位素分析结果表明,卡房铜矿似层状矿体中硫化物的硫来源于三叠系玄武岩,而燕山期花岗岩和三叠纪玄武岩共同为卡房铜矿接触带矿体提供了成矿所需的大部分的硫。铅同位素分析结果显示,卡房铜矿似层状矿体的成矿物质主要来源于三叠系玄武岩,而接触带矿体的铅可能主要来源于燕山期花岗岩。     

Sulphur isotope effects in the dissociation and evaporation of troilite: A possible mechanism for 34S enrichment in lunar soils

Both the dissociation and evaporation of troilite. heated to its melting point in vacuo, are isotopically selective. The elemental sulphur from the dissociation of troilite has a ${}^{34}\text{S}{}^{32}\text{S}$ ratio which is 13.0‰ less than that of the undissociated material while the ${}^{34}\text{S}{}^{32}\text{S}$ ratio in evaporated troilite is 5.4‰ less than that of the residual material. The two processes occur simultaneously and the isotopic variations during the course of the reaction are in accord with those for a branched reaction where the unreacted material remains isotopically well-mixed, as in a Rayleigh distillation process. This isotopic selectivity must be taken into account, along with that in other lunar surface processes, when considering the heavy isotope enrichment of sulphur in lunar soils.     

Developing carbon budgets for UK agriculture, land-use, land-use change and forestry out to 2022

This paper derives a notional future carbon budget for UK agriculture, land use, land use change and forestry sectors (ALULUCF). The budget is based on a bottom-up marginal abatement cost curve (MACC) derived for a range of mitigation measures for specified adoption scenarios for the years 2012, 2017 and 2022. The results indicate that in 2022 around 6.36 MtCO₂e could be abated at negative or zero cost. Furthermore, in the same year, over 17% of agricultural GHG emissions (7.85 MtCO₂e) could be abated at a cost of less than the 2022 Shadow Price of Carbon (£34 (tCO₂e)^???1). The development of robust MACCs faces a range of methodological hurdles that complicate cost-effectiveness appraisal in ALULUCF relative to other sectors. Nevertheless, the current analysis provides an initial route map of efficient measures for mitigation in UK agriculture.