This work presents the temporal evolution and spatial distribution of nitrogen dioxide (NO2) measured with the help of passive diffusion tubes in different environments: rural, sub-urban, urban, at La Réunion Island in December 1997 and November 2000 (austral spring), respectively. NO2 concentration exhibits notable enhancement from 1997 to 2000. For instance, its mean concentration was 16 and 20 μg/m3 in December 1997 and November 2000, respectively, at La Réunion Island, especially in inhabited regions due to increase of local anthropogenic activities, mainly traffic circulation, in the absence of house heating and biomass burning. We also observe a net increase of pollutant levels by a factor two in rural/remote areas within 3 years, which is tied to the extension of inhabited areas and air-flows from enhanced local sources. The increase of atmospheric pollutants is mainly due to enhancement of anthropogenic activities (traffic) since the 1990s at La Réunion Island, which results from a constant increase of population and consequently, from a higher number of vehicles in circulation. Importantly, in cities like Saint-Denis, where traffic network has been subject to notable improvement (e.g. single to double lanes, etc.), pollutant levels exhibit little variability as in temperate continental latitudes. Semi-continuous NO2 concentration measured in parallel with ozone in November 2000 also showed that daytime photochemical ozone production is influenced by pollutant and precursor (NO2) levels at Saint-Denis, while nighttime ozone increase is mainly tied to dynamical processes. The November 2000 ozone diurnal pattern is notably different from that observed in September 1995, during which a daytime ozone loss was observed, pointing out that atmospheric conditions have been subject to notable changes, i.e., clean to moderately polluted, within a few years at La Réunion Island. The results presented here point out that the ‘source enhancement effect’ is superimposed on dynamical and photochemical processes to influence pollutants variability and hence atmospheric chemistry, in a quite ‘pristine’ tropical oceanic region. 相似文献
Analyses of mineral inclusions, carbon isotopes, nitrogen contents and nitrogen aggregation states in 29 diamonds from two Buffalo Hills kimberlites in northern Alberta, Canada were conducted. From 25 inclusion bearing diamonds, the following paragenetic abundances were found: peridotitic (48%), eclogitic (32%), eclogitic/websteritic (8%), websteritic (4%), ultradeep? (4%) and unknown (4%). Diamonds containing mineral inclusions of ferropericlase, and mixed eclogitic-asthenospheric-websteritic and eclogitic-websteritic mineral associations suggests the possibility of diamond growth over a range of depths and in a variety of mantle environments (lithosphere, asthenosphere and possibly lower mantle).
Eclogitic diamonds have a broad range of C-isotopic composition (δ13C=−21‰ to −5‰). Peridotitic, websteritic and ultradeep diamonds have typical mantle C-isotope values (δ13C=−4.9‰ av.), except for two 13C-depleted peridotitic (δ13C=−11.8‰, −14.6‰) and one 13C-depleted websteritic diamond (δ13C=−11.9‰). Infrared spectra from 29 diamonds identified two diamond groups: 75% are nitrogen-free (Type II) or have fully aggregated nitrogen defects (Type IaB) with platelet degradation and low to moderate nitrogen contents (av. 330 ppm-N); 25% have lower nitrogen aggregation states and higher nitrogen contents (30% IaB; <1600 ppm-N).
The combined evidence suggests two generations of diamond growth. Type II and Type IaB diamonds with ultradeep, peridotitic, eclogitic and websteritic inclusions crystallised from eclogitic and peridotitic rocks while moving in a dynamic environment from the asthenosphere and possibly the lower mantle to the base of the lithosphere. Mechanisms for diamond movement through the mantle could be by mantle convection, or an ascending plume. The interaction of partial melts with eclogitic and peridotitic lithologies may have produced the intermediate websteritic inclusion compositions, and can explain diamonds of mixed parageneses, and the overlap in C-isotope values between parageneses. Strong deformation and extremely high nitrogen aggregation states in some diamonds may indicate high mantle storage temperatures and strain in the diamond growth environment. A second diamond group, with Type IaA–IaB nitrogen aggregation and peridotitic inclusions, crystallised at the base of the cratonic lithosphere. All diamonds were subsequently sampled by kimberlites and transported to the Earth's surface. 相似文献
The ‘Anthropocene’ is now being used as a conceptual frame by different communities and in a variety of contexts to understand the evolving human–environment relationship. However, as we argue in this paper, the notion of an Anthropos, or ‘humanity’, as global, unified ‘geological force’ threatens to mask the diversity and differences in the actual conditions and impacts of humankind, and does not do justice to the diversity of local and regional contexts. For this reason, we interpret in this article the notion of an Anthropocene in a more context-dependent, localized and social understanding. We do this through illustrating examples from four issue domains, selected for their variation in terms of spatial and temporal scale, systems of governance and functional interdependencies: nitrogen cycle distortion (in particular as it relates to food security); ocean acidification; urbanization; and wildfires. Based on this analysis, we systematically address the consequences of the lens of the Anthropocene for the governance of social-ecological systems, focusing on the multi-level, functional and sectoral organization of governance, and possible redefinitions of governance systems and policy domains. We conclude that the notion of the Anthropocene, once seen in light of social inequalities and regional differences, allows for novel analysis of issue-based problems in the context of a global understanding, in both academic and political terms. This makes it a useful concept to help leverage and (re-)focus our efforts in a more innovative and effective way to transition towards sustainability. 相似文献
The release of excessive anthropogenic nitrogen contributes to global climate change, biodiversity loss, and the degradation of ecosystem services. Despite being an urgent global problem, the excess nitrogen is not governed globally. This paper considers possible governance options for dealing with excessive nitrogen through target setting, which is an approach commonly adopted to address global environmental problems. The articulation of the nitrogen problem and the numerous international institutions dealing with it, provide evidence of a nitrogen regime characterised by limited coordination and targets covering sources and impacts only partially. This calls for improving the nitrogen governance in the direction of more integrated approaches at the global scale. In this vein, the paper investigates two opposite governance options – here labelled as ‘holistic’ and ‘origin-based’ – and evaluates them for their capability to define solutions and targets for human-induced nitrogen. From the analysis, it emerges that origin-based solutions can be preferable to holistic solutions as they can be more specific and potentially have greater immediate results. Independent from which governance arrangement is chosen, what matters most is the speed at which an arrangement can deploy solutions to combat (fast-growing) nitrogen pollution. 相似文献
Recent information on some consequences of the acute mid-water oxygen deficiency in the Arabian Sea, especially on carbon-nitrogen
cycling, is reviewed. An evaluation of published estimates of water column denitrification rate suggests an overall rate in
the vicinity of 30Tg Ny-1, but the extent of benthic contribution remains unknown. A decoupling of denitrification from primary production, unique
to the Arabian Sea, is revealed by nitrite, electron transport system (ETS) activity and bacterial production data. Results
of both enzymatic and microbiological investigations strongly point to a major role of organic carbon other than that sinking
from surface layers in supporting denitrification. Although denitrification is associated with an intermediate nepheloid layer,
it seems unlikely that the excess carbon comes with particles re-suspended along the continental margins and transported quasi-horizontally
into the ocean interior; instead, the particle maximum may directly reflect a higher bacterial abundance. It is proposed that
denitrification may be predominantly fuelled by the dissolved organic matter. 相似文献
Nitrate pollution due to deep leaching from pit latrines has caused water supply wells in eastern Botswana to exceed health limits concerning nitrate. It was deduced from the estimated intake of salt and protein by the population that, as an average, about 10 percent of the human nitrogen excretion is leached to the groundwater. This fraction was also found in southern India, where on-the-ground excretion is customary. The nitrogen circulation in general in the savanna ecosystem is not appreciably affected in spite of a large livestock density. Overall nitrate leaching is in the order of 1.5 kg N/ha/y, similar to that in another semiarid area in southern India. However, in India, there seems to be a more diffuse areal leaching from agriculture as well as from villages.Measures to minimize the nitrate leaching could be to plant deep-rooted trees adjacent to pit latrines or to use latrines that separate the urine from the faces for a more near-surface infiltration facilitating plant uptake. Measures to minimize leaching will also lessen the rick for bacterial pollution of the groundwater. 相似文献
The gel-permeation chromatography system with multicomponent detection of organic carbon, organic nitrogen, organic halogen, and UV/vis absorption measurement is shown to be a useful tool for characterization of industrial wastewaters and wastewater treatment processes. The proposed system was used to investigate biologically treated wastewater from chemical industry, whereby one branch stream was identified to be the main source of persistent halogenated organics. Various treatment processes of pulp mill wastewater were also evaluated revealing that precipitation with aluminium is very effective for the removal of the high molecular fraction whereas the biological treatment is generally less selective. In the biological treatment of tannery wastewaters, it has been shown that the aerobic treatment, in contrast to anaerobic step, causes evident alterations of the composition of the polar DOC fraction. The nitrogen containing compounds are also better decomposed in the aerobic step compared to the anaerobic one. 相似文献
Surface NO and NO2 mixing ratios were measured aboard the research vessel Polarstern during the mission ANT VII/1 from 24 September to 5 October 1988. The measurements were taken along the meridian at 30° W in the Atlantic region covering latitudes between 30° N and 30° S. The average mixing ratios were about 12 pptv NO/30 pptv NO2 in the Northern Hemisphere and about 7 pptv NO/22 pptv NO2 in the Southern. Elevated mixing ratios of 20 pptv NO/70 pptv NO2 were found at 12° N (probably due to air masses originating from the surface of West Africa) and in the region of the ITCZ between 8° N and 5° N. Because of probable contamination by the ship, the measured mixing ratios mostly represent upper limits. 相似文献