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New directions in black carbon organic geochemistry 总被引：8，自引：0，他引：8
In the past 30 years, the field of black carbon (BC) research has expanded broadly, stretching from its traditional core in the atmospheric sciences into oceanography, soil science, and even anthropology. Results produced in this period of expansion have been exciting: BC has been detected in many important geochemical pools, and interesting new research directions open as we learn about the role of this byproduct of biomass burning in the carbon cycle. Especially important research directions will be the quantification of BC loss processes (both biotic and abiotic), measurement of BC decomposition products in environmentally relevant reservoirs, and exploration of the interactions between BC and its host organo-mineral matrix, including the role of BC in pedogenesis.However, along with exciting results, we have also seen apparent discrepancies between BC studies. These discrepancies occur at least in part because of a lack of a common language, common methods, and a common model of BC. This paper lays out the framework many BC researchers use to understand the role of BC in the carbon cycle, discussing the ‘combustion continuum’ BC model and the methodological continuum that this model implies. 相似文献
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《Climate Dynamics》2008,30(7-8):887-907
Fire activity has varied globally and continuously since the last glacial maximum (LGM) in response to long-term changes in
global climate and shorter-term regional changes in climate, vegetation, and human land use. We have synthesized sedimentary
charcoal records of biomass burning since the LGM and present global maps showing changes in fire activity for time slices
during the past 21,000 years (as differences in charcoal accumulation values compared to pre-industrial). There is strong
broad-scale coherence in fire activity after the LGM, but spatial heterogeneity in the signals increases thereafter. In North
America, Europe and southern South America, charcoal records indicate less-than-present fire activity during the deglacial
period, from 21,000 to ∼11,000 cal yr BP. In contrast, the tropical latitudes of South America and Africa show greater-than-present
fire activity from ∼19,000 to ∼17,000 cal yr BP and most sites from Indochina and Australia show greater-than-present fire
activity from 16,000 to ∼13,000 cal yr BP. Many sites indicate greater-than-present or near-present activity during the Holocene
with the exception of eastern North America and eastern Asia from 8,000 to ∼3,000 cal yr BP, Indonesia and Australia from
11,000 to 4,000 cal yr BP, and southern South America from 6,000 to 3,000 cal yr BP where fire activity was less than present.
Regional coherence in the patterns of change in fire activity was evident throughout the post-glacial period. These complex
patterns can largely be explained in terms of large-scale climate controls modulated by local changes in vegetation and fuel
load.
The readers are requested to refer to the section “List of contributors” for the complete list of author affiliation details. 相似文献
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Ximei Hou Guoshun Zhuang Yanfen Lin Juan Li Yilun Jiang Joshua S. Fu 《Journal of Atmospheric Chemistry》2008,61(2):119-131
The indoor PM2.5 aerosol samples for charcoal broiling source under Chinese traditional charbroiling and the ambient fine aerosols samples
(PM2.5) were collected in Beijing to investigate the characteristics of the charcoal broiling source and its impact on the fine
organic aerosols in the atmosphere. The concentrations of 20 species of the trace organic compounds, including polycyclic
aromatic hydrocarbons (PAHs), fatty acids, levoglucosan, and cholesterol in PM2.5 were identified and quantified by GC/MS. The total PAHs and fatty acids emitted from charcoal broiling to PM2.5 were 8.97 and 87,000 ng mg−1 respectively. The concentrations of the light molecular weight (LMW) 3- and 4-ring PAHs were much higher than those of the
high molecular weight (HMW) 5- and 6-ring PAHs. Fatty acids were the most abundant species in source profile, accounting for
over 90% of all identified organic compounds. More polyunsaturated fatty acid (linoleic acids) than the saturated fatty acid
(stearic acids) emitted in the cooking. Charcoal broiling is a minor source of PAHs compared to the source of biomass burning.
Comparing the ratios of levoglucosan/fatty acid and levoglucosan/cholesterol in the charcoal broiling samples to the ambient
samples, it is evident that meat cooking is an important source of fatty acids, but a less important source of cholesterol.
Cooking, as one of the source of fine organic particles, plus other anthropogenic sources would be related to the formation
of the severe haze occurred and spread over the urban atmosphere in most of the cities of China in the past several years. 相似文献
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The equatorial peatlands of the Kutai lowland of eastern Kalimantan are generally 4–10 m in thickness but some sections exceed 16 m in depth. The deposition of peat commenced about 8000 yrs ago after shallow flooding of the basin by the Mahakam River. The earliest vegetation is a Pandanus swamp which grades upwards to swamp forest dominated by dipterocarps. The peatland has expanded laterally and rivers have maintained narrow levee-channel tracks through the swamp, which has grown vertically in balance with river accretion. Historical fires are associated with extreme El Niño years of drought, but human agency is important. The fires of 1982–1983 and 1997–1998 burnt up to 85% of the vegetation on the peatland. Although charcoal analyses show that fire has occurred throughout the history of the peatland, it is rare in forests remote from rivers until the last 3000 years and only common within the last millennium. Fires are earlier and more frequent in sites accessible from waterways, and floodplains have been widely burnt down to water table or below, forming extensive lakes. 相似文献
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Foy Lake in northwestern Montana provides a record of annual-to-decadal-scale landscape change. Sedimentary charcoal and pollen analyses were used to document fire and vegetation changes over the last 3800 years, which were then compared to similar records from AD 1880 to 2000. The long-term record at Foy Lake suggests shifts between forest and steppe as well as changes in fire regime that are likely the result of climate change. Fire activity (inferred from the frequency of charcoal peaks) averaged 18 fire episodes/1000 years from 3800 to 2125 cal year BP, and increased from 16 fire episodes/1000 years at 2125 cal year BP to 22 episodes/1000 years at 750 cal year BP, a period when the pollen data suggest that steppe vegetation yielded to increasing patches of forest cover. Between 2125 and 750 cal year BP, increased forest cover produced more background charcoal than before and after this period, when vegetation was dominated by steppe. Between 750 and 75 cal year BP steppe has expanded and fire episode frequency averaged 33 episodes/1000 years, increasing to a maximum of 40 episodes/1000 years at ca. 300 cal year BP and then decreasing to present levels. Since AD 1880, the pollen record indicates an increase in shrubs and grasses from AD 1895 to 1960 as a result of vegetation changes associated with timber harvesting and livestock grazing. No fires have been documented in the Foy Lake watershed since AD 1880. Charcoal from the extralocal fires of AD 1910, burning over 4,111,249 ha in Idaho, Montana, and Wyoming, however, is present in Foy Lake. Between AD 1970 and 2000, increased arboreal pollen in the record is consistent with observations that the forest has become more closed. The activities of Euro–Americans have led to a decline in forest cover between AD 1880 and 1970, followed by a recent increase as trees are now growing in areas previously occupied by steppe. Euro–Americans are likely the cause of a reduction in fire activity in watershed since AD 1880. 相似文献
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主要介绍新疆维吾尔自治区地震局放射性同位素碳测年实验室的１４Ｃ测年原理,样品的前处理、样品的化学制备,低水平放射性测量方法及测定年代。首次公布一批１４Ｃ年代测定数据。 相似文献
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Tadeu José Pereira Gilda Silva Maria José Costa José Lino Costa 《Estuarine, Coastal and Shelf Science》2011
The Lusitanian toadfish, Halobatrachus didactylus (Bloch and Schneider, 1801), is a subtropical sound-producing marine teleost that inhabits estuaries and other brackish water ecosystems in its northern distribution area. The relative isolation of populations within estuaries may cause important modifications in the bio-ecology of this species. The males of this species present two morphotypes which are more accurately distinguishable during the reproductive season. In the Tagus estuary population, the two types of reproductive males were present: type I, the “characteristic” morphotype, and type II, the alternative morphotype. The opportunistic males had more developed testis while type I males had more developed accessory glands. Type I males presented more developed swimbladders and larger body size and live longer than type II males. On the contrary, type II males grew faster and matured earlier. The feeding habits of the two male morphotypes were similar during the reproductive season but differences were found between reproductive specimens and non-reproductive specimens. The diet of reproductive specimens was mainly composed of benthic prey in contrast to predominance of nectobenthic prey in the diet of non-reproductive specimens. The females of H. didactylus generally had an intermediate pattern between the two male morphotypes. The percentage of type II males tended to be higher in denser areas of the estuary. In comparison with populations from different size ecosystems, smaller ecosystems revealed important modifications on the bio-ecology of the species due to the increased competition for nesting sites and mating partners, favouring alternative male tactics. 相似文献
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The Algoa Basin is an onshore rift basin filled by an Upper Mesozoic non-marine and shallow marine sedimentary sequence. The middle unit of this clastic succession is assigned to the Lower Cretaceous Kirkwood Formation, known to host a wealth of plant and animal fossils together with poorly documented lignites, amber and charcoal clasts. This study is motivated by the growing interest in the impact of wildfires on the palaeoenvironment during the high-oxygen, Cretaceous world. It has been hypothesised that frequent and severe Cretaceous wildfires triggered large-scale non-marine denudation events, altering the sedimentation dynamics and influencing the evolution of ecosystems. In order to investigate this phenomenon, charcoal-bearing sedimentary rocks and plant fossil assemblages of the Kirkwood Formation have been studied at the Bezuidenhouts River locality, ∼50 km north of Port Elizabeth (Eastern Cape, South Africa).Detailed field observations of the sedimentary facies suggest that deposition occurred in a meandering fluvial environment with mature, vegetated floodplains. Depositional trends within a charcoal-rich bed (i.e., stratification, flattening and decrease in charcoal clast size down-current) indicate that a charcoal-rich debris flow, linked to a post-wildfire flood event, became diluted by fluvial flow. Palaeocurrent indicators (e.g., orientation of fossil logs) suggest unidirectional currents from SW to NE, which are somewhat inconsistent with the previously reported regional palaeocurrent directions in the Kirkwood Formation.To gain insights into the fire-influenced dynamics of the Early Cretaceous ecosystems, the macro-plant fossil assemblages of the Kirkwood Formation were considered, with reference to the responses of modern plant analogues to wildfire. Of the plant orders reported from macrofossils of the Kirkwood Formation, the Cycadales, Pinales and Filicales, are known to have produced large woody or fibrous trunks and stems, or in the case of the Bennettitales more densely branched, divaricate architectures, and are likely to have provided the bulk of fuel for wildfires, with fern elements dominating groundcover niches. The particular role of these plants in the Early Cretaceous wildfire palaeoecology of the Algoa Basin is a topic for an ongoing study, but the Bezuidenhouts River locality appears to record the aftermath of a severe crownfire that led to mass tree mortality. 相似文献