Natural and anthropogenic C2 to C6 hydrocarbons in the central-eastern Venezuelan atmosphere during the rainy season

The levels of low molecular weight hydrocarbons were measured at pristine sites and rural locations affected by hydrocarbon emissions from oil and gas producing fields in Venezuela. At the clean sites, lower concentrations of C₂ to C₆ alkanes were observed, whereas, in comparison with remotes sites, very much higher levels were measured at the polluted sites. Alkenes present relatively high concentrations, with isoprene being the most abundant, all over the study region. The main sources of alkenes are likely to be natural, mainly from vegetation. The levels of alkanes recorded at the clean sites and the alkene levels found everywhere in the region are in agreement with the values reported for other clean sites in the tropics. The increase of ozone production capacity due to the anthropogenic emissions of alkanes from oil and gas fields was estimated. Due to the presence in the atmosphere of important amounts of naturally emitted isoprene, ethene and propene, which makes a substantial contribution to the reactivity of the hydrocarbon mixture, a small increase (<5%) was estimated to occur in the capacity of the ozone production at a regional scale during the rainy season.     

A Eulerian air pollution model for Europe with nonlinear chemistry

A long-range transport model with nonlinear chemical reactions is described. The model contains 35 pollutants and 70 chemical reactions. This is a Eulerian model defined on a space domain containing the whole of Europe. The spherical space domain (corresponding to the Earth's surface covered by the model) is mapped into a square plane domain and discretized by using a 32×32 grid. The grid increments are equidistant (both along the Ox axis and along the Oy axis). The choice of values of the physical parameters involved in the model and the numerical treatment of the model are shortly discussed. The model is tested with meteorological data for 1985 and 1989. The numerical results are compared with measurements at stations located in different European countries. Extensive comparisons of ozone concentrations for July 1985 with measurements taken at 24 European stations are also carried out. Results concerning three episodes in July 1985 as well as results obtained in the study of the sensitivity of the ozone concentrations to variations of NO _x and/or anthropogenic VOC emissions are presented. The advantages and the limitations of such a model are discussed. The model is continuously improved by adding new modules to it. The plans for improvements in the near future are outlined.     

Comparability of Biogenic VOC Emission Rate Measurements under Laboratory and Ambient Conditions at the Example of Monoterpene Emissions from Scots Pine (Pinus sylvestris)

Laboratory experiments under controlled environmental conditions are a useful tool to investigate the influence of different environmental parameters on VOC emissions from plants individually. Before using the obtained results to interpret measurements under ambient conditions, it has to be ensured that the laboratory system is suitable for performing emission rate measurements under ambient-like conditions to derive algorithms describing the emissions of volatile organic compounds as a function of physical variables like temperature and light intensity. Here we compare results from monoterpene emission rate measurements with Scots pines (Pinus sylvestris L.) under both ambient environmental conditions using a mobile plant enclosure chamber, and under controlled laboratory conditions in a continuously stirred tank reactor. The different analytical instruments to quantify monoterpene emissions were compared in an intercalibration experiment. Measurements of the mixing ratios of -pinene, -pinene, 3-carene, camphene, and limonene on the order of some hundred parts per trillion differed by less than 20%. The laboratory system has proven capable of providing ambient-like conditions and results of monoterpene emission rate measurements under laboratory conditions could be extrapolated to the natural environment. Monoterpene emission rate measurements with identical specimens of Scots pines conducted within small temporal differences under similar laboratory and outdoor conditions agreed well. Both laboratory and outdoor experiments clearly showed that distinct and constant values neither exist for the standard emission rates nor for the emission pattern of monoterpenes from Scots pine. Temporal variations in the standard emission rates from identical specimens and plant-to-plant variations were on the order of one magnitude.     

The Kuwae (Vanuatu) eruption of<Emphasis Type="SmallCaps"> AD</Emphasis> 1452: potential magnitude and volatile release

Sometime during AD 1452, according to new evidence, a large-magnitude, initially phreatomagmatic eruption, destroyed the island of Kuwae (16.83°S, 168.54°E), located in the present-day Republic of Vanuatu. It created a 12×6-km submarine caldera composed of two adjacent basins. Based on estimates of caldera volume, between 30 and 60 km³ DRE of dacite magma was ejected as pyroclastic flow and fall deposits during this event. Annual layers of ice dating from the period AD 1450–1460 contain acidity peaks representing fallout of sulfuric acid onto both the Greenland and Antarctic ice caps. These acidity peaks have been attributed by others to the sedimentation of H₂SO₄ aerosols that originated from sulfur degassing during the Kuwae eruption. Improved dating techniques and new data from nineteen ice cores reveal a single acidity peak attributed to Kuwae lasting from 1453 to 1457. In this study, we present new electron microprobe analyses of the S, Cl, and F contents of matrix glasses and glass inclusions in phenocrysts from tephra ejected during the Kuwae eruption. We establish that the Kuwae event did indeed yield a large release of sulfur gases. From our glass inclusion data and analysis, we calculate that the total atmospheric aerosol loading from the 1452 Kuwae eruption was ≫100 Tg H₂SO₄. Much of the volatile mass released during the eruption was probably contained in a separate, volatile-rich, fluid phase within the pre-eruptive Kuwae magma body. Comparing the volatile release of the Kuwae eruption with other large-magnitude eruptions, places Kuwae as the greatest sulfuric acid aerosol producer in the last seven centuries, larger even than sulfur emissions from the eruption of Tambora (Indonesia) in 1815, and possibly Laki (Iceland) in 1783. The severe and unusual climatic effects reported in the mid- to late-1450s were likely caused by the Kuwae eruption.     

Mitigating Agricultural Emissions of Methane

Agricultural crop and animal production systems are important sources and sinks for atmospheric methane (CH4). The major CH4 sources from this sector are ruminant animals, flooded rice fields, animal waste and biomass burning which total about one third of all global emissions. This paper discusses the factors that influence CH4 production and emission from these sources and the aerobic soil sink for atmospheric CH4 and assesses the magnitude of each source. Potential methods of mitigating CH4 emissions from the major sources could lead to improved crop and animal productivity. The global impact of using the mitigation options suggested could potentially decrease agricultural CH4 emissions by about 30%.     

Metal-residence sites in lavas and tuffs from Volcán Popocatépetl, Mexico: implications for metal mobility in the environment

 Volcan Popocatépetl is a Quaternary stratovolcano located 60 km southeast of Mexico City. The summit crater is the site of recent ash eruptions, excess degassing, and dacite dome growth. The modern cone comprises mainly pyroclastic flow deposits, airfall tephras, debris flows, and reworked deposits of andesitic composition; it is flanked by more mafic monogenetic vents. In least-degassed fallout tuffs and mafic scoria, transition metals are concentrated in phases formed before eruption, during eruption, and after eruption. Preeruptive minerals occur in both lavas and tephra, and include oxides and sulfides in glass and phenocrysts. The magmatic oxides consist of magnetite, ilmenite, and chromite; the sulfides consist of both (Fe,Ni)_1-xS (MSS) and Cu–Fe sulfide (ISS). Syn- and posteruptive phases occur in vesicles in both lavas and tephra, and on surfaces of ash and along fractures. The mineral assemblages in lavas include Cu–Fe sulfide and Fe–Ti oxide in vesicles, and Fe sulfide and Cu–Fe sulfide in segregation vesicles. Assemblages in vesicles in scoria include Fe–Ti oxide and rare Fe–Cu–Sn sulfide. Vesicle fillings of Fe–Ti oxide, Ni-rich chromite, Fe sulfide, Cu sulfide, and barite are common to two pumice samples. The most coarse-grained of the vesicle fillings are Cu–Fe sulfide and Cu sulfide, which are as large as 50 μ in diameter. The youngest Plinian pumice also contains Zn(Fe) sulfide, as well as rare Ag–Cu sulfide, Ag–Fe sulfide, Ag bromide, Ag chloride, and Au–Cu telluride. The assemblage is similar to those typically observed in high-sulfidation epithermal mineralization. The fine-grained nature and abundance of syn- and/or posteruptive phases in porous rocks makes metals susceptible to mobilization by percolating fluids. The abundance of metal compounds in vesicles indicates that volatile exsolution prior to and/or during eruption played an important role in releasing metals to the atmosphere. Received: March 1997 · Accepted: 27 May 1997     

Measurements of stable carbon isotopic composition of ethane and propane over the western North Pacific and eastern Indian Ocean: A useful indicator of atmospheric transport process

Stable carbon isotopic composition of ethane and propane over the western North Pacific and eastern Indian Ocean between 31°N and 26°S was investigated from February through March 2004. The isotopic composition of ethane ranged from −28 to −18‰ and showed a gradual increase from north to south. Conversely, that of propane was between −31 and −24‰; it showed no systematic latitudinal variation. Investigation of the ethane/propane ratio indicates that ethane and propane that originated from northern mid-latitude countries in the eastern part of Eurasia were both transported into the western North Pacific region. However, the results of the isotopic analyses indicate the contribution of oceanic emission to the atmospheric propane during transport, although that contribution can not be discerned for ethane. A ship based stationary observation conducted in the western equatorial North Pacific showed that the isotopic composition of ethane varied from −25 to −19‰ and showed clear systematic diurnal variation: propane ranged between −32 to −26‰ and no such isotopic diurnal signal was observed. The diurnal variation for ethane is explained by entrainment of free tropospheric air, whereas the variation for propane was influenced by oceanic emissions as well as the entrainment. The contribution of oceanic emissions to the atmospheric propane inventory was considered from our isotopic observation. Isotopic composition of dissolved propane is estimated to be less than −38‰, and the contribution up to 79% was calculated when the isotopic composition of dissolved propane is assumed to be −40‰. Our study demonstrates that isotopic analysis can be more useful than ratio-based analysis to improve our present understanding of transport processes, especially for impact of the oceanic emissions on the atmospheric distribution of low level C₂–C₅ non-methane hydrocarbons such as propane in the remote marine atmosphere.     

长江三角洲碳排放与植被覆盖耦合协调时空格局及影响因素分析

通过构建评价指标体系和分析框架,利用综合指数法、耦合协调度模型和灰色关联度模型分析2005―2017年长江三角洲（长三角）碳排放与植被固碳耦合协调时空变化特征及驱动因素,并模拟政府决策优先级对耦合协调度趋势的影响。结果表明：长三角碳排放空间集聚特征显著,基本形成了以长江沿线和长三角东南沿海区域为核心的沿江沿海高排放带;长三角碳排放与植被固碳耦合协调度具有明显的空间分异特征,呈现出南京-上海沿线一般失调区域为核心的圈层结构特征;植被覆盖综合评价值高于碳排放综合评价值的地区耦合协调度普遍较高,人口的集聚和变化、城市建设和能源消耗对耦合协调度影响最大;同时,政府决策的优先级会显著影响耦合协调趋势。     

Ecological Modernization or Aristocratic Conservation? Exploring the Impact of Affluence on Carbon Emissions at the Local Level

Social scientists have debated how affluence impacts carbon emissions at the national level. We conduct an exploratory study at the subnational level to expose another dimension of the affluence–emissions debate. Based on the notion of aristocratic conservation, we hypothesize that affluence is positively related to carbon emissions from consumption activities but negatively related to emissions from production activities. We test these hypotheses using county-level data in the United States for the year 2002. A spatial regression analysis demonstrates that median household income is positively associated with consumption-based emissions; nevertheless, we find evidence of an environmental inequality Kuznets curve in the relationship between median household income and production-based emissions. This finding suggests that the wealthiest counties are able to displace certain types of emissions, specifically those related to energy and industrial production. We discuss the theoretical and political implications of these results.