Reflectance spectroscopy of insoluble organic matter (IOM) and carbonaceous meteorites     

Hannah H. Kaplan  Ralph E. Milliken  Conel M. O'D. Alexander  Christopher D. K. Herd 《Meteoritics & planetary science》2019,54(5):1051-1068

Insoluble organic matter (IOM) is the major organic component of chondritic meteorites and may be akin to organic materials from comets and interplanetary dust particles (IDPs). Reflectance spectra of IOM in the range 0.35–25 μm are presented as a tool for interpreting organic chemistry from remote measurements of asteroids, comets, IDPs, and other planetary bodies. Absorptions in the IOM spectra were strongly related to elemental H/C (atom) ratio. The aliphatic 3.4 μm absorption in IOM spectra increased linearly in strength with increasing H/C for H/C > 0.4, but was absent at lower H/C values. When meteorite spectra from the Reflectance Experiment Laboratory (RELAB) spectral catalog (n = 85) were reanalyzed at 3.4 μm, this detection limit (H/C > 0.4) persisted. Aromatic absorption features seen in IOM spectra were not observed in the meteorite spectra due to overlapping absorptions. However, the 3.4 μm aliphatic absorption strength for the bulk meteorites was correlated with both H/C of the meteorite's IOM and bulk C (wt%). Gaussian modeling of the 3 μm region provided an additional estimate of bulk C for the meteorites, along with bulk H (wt%), which is related to phyllosilicate abundance. These relationships lay the foundation for determining organic and phyllosilicate abundances from reflectance spectra. Both the full IOM spectra and the spectral parameters discussed here will aid in the interpretation of data from asteroid missions (e.g., OSIRIS‐REx, Hayabusa2), and may be able to place unknown spectral samples within the context of the meteorite collection.  相似文献   

Sediment grain size measurements are affected by site-specific sediment characteristics and analysis methods: implications for environmental monitoring     

Stephen Hunt  Hannah F. E. Jones 《新西兰海洋与淡水研究杂志》2019,53(2):244-257

Sediment grain size, and specifically changes in the percent mud content (i.e. the fraction <63?µm) over time is often used as an indicator of estuarine environmental health. Using sediment samples from three distinct estuarine systems, we determined that different analytical methods (laser diffraction and wet sieving) gave significantly different results in terms of percent mud content. These differences are also ecologically meaningful when considering the influence of mud on estuarine macrofauna. We propose an approach to measuring sediment grain size termed Environmentally Available Sediment (EAS), which advocates for the measurement of the sediment that biota are directly exposed to. For the purposes of environmental monitoring, it is also essential to monitor sediment grain size in a repeatable way which is likely to be achieved using consistent (or no) pre-treatment and the use of a measurement technique that is unlikely to change over time, e.g. wet sieving.  相似文献   

The construction of ‘local’ interest in New South Wales environmental planning processes     

Hannah Della Bosca 《The Australian geographer》2019,50(1):49-68

Deliberative democracy in the form of community participation is considered a ‘key priority’ in New South Wales (NSW) environmental planning. Community participation plays an increasingly central role in state significant developments, which are often sites of contestation. Community participation processes draw upon particular factors of place-based identity, which engage with notions of procedural legitimacy in subtle and not-so-subtle ways. This paper uses a legal geography analysis to explore this link between place-based identity and the experience of procedural legitimacy. We highlight a case study in which a contested coal mining development near Lithgow, NSW was approved by the NSW Planning Assessment Commission (PAC). This analysis examines how ‘local’ justice was constructed and mobilised in specific ways by proponents and opponents alike. Spatial factors of identity manifested in distinct ways in participation processes, particularly with respect to (i) claims to legitimacy and (ii) the lived experiences of engagement in a public forum. This case study demonstrates the way in which dualistic spatial terms such as ‘outsider’ opposition and ‘local’ support can render multiple interests of both human and non-human communities invisible. In so doing we are engaging with current work on environmental justice that examines the intersection of scale, efficacy and equity in processes of environmental governance.  相似文献   

The discursive nature of environmental conflicts: the case of the Öresund link     

Hannah Dekker Linnros  & Per Olof Hallin 《Area》2002,33(4):391-403

This paper analyzes the environmental conflict concerning the construction of a permanent link between Malmo, Sweden and the Danish capital, Copenhagen. The conflict is approached as both a discursive and institutional struggle, in which representations of nature and the environment are used not only to legitimize, but also to question institutional policies and development plans. The analysis focuses primarily on three of the counter-discourses that have emerged in conflict with the hegemonic, institutional discourse, and also indicates how spatial representations have become important constituents of the discourses.  相似文献   

The timing and isotopic character of regional hydrothermal alteration and associated epigenetic mineralization in the western sector of the Kaapvaal Craton (South Africa)     

Michael J Duane  F.Johan Kruger  Audrey M Turner  Hannah T Whitelaw  Henk Coetzee  Balt T Verhagen 《Journal of African Earth Sciences》2004,38(5):69

The Kaapvaal Craton of South Africa comprises an Archaean core of ≈3.5 Ga lithospheric and crustal rocks surrounded by younger accreted terrains of ≈3.0–2.7 and ≈2.1–1.9 Ga. The craton is covered by relatively undeformed 3.0–2.4 Ga supracrustal rocks, which show the effects of thermal and hydrothermal interaction. Part of this activity is manifested by a large number of epigenetic Pb–Zn (±Ag, Au, Cu, F) deposits in the cover rocks of the Kaapvaal Craton. These include small volcanic and breccia hosted deposits in mafic and felsic volcanic rocks of the 2.7 Ga Ventersdorp Supergroup and the Mississippi Valley-type (MVT) deposits in the carbonates of the Transvaal Supergroup.MVT mineralization at the Pering (and other Zn–Pb deposits) is hosted in fracture-generated N–S breccia bodies in the Paleoproterozoic carbonate succession of the western Kaapvaal Craton. The fluids carrying the metals were focused in vertical bodies within the fracture zones (FZ), the metals and the sulphur being carried together and precipitated in organic-rich sectors of the basin. Two small Pb–Zn deposits within mafic rocks of the Ventersdorp Supergroup, stratigraphically below the basin-hosted MVTs on the southwestern part of the Kaapvaal Craton have secondary chlorite which is extremely Rb-rich, associated with the mineralization. This chlorite and the associated altered basaltic host rocks give a Rb–Sr date of ≈1.98 Ga, and the associated galena Pb isotope data plot on the same array as those of other Pb–Zn deposits, the radiogenic intercept giving a date of ≈2.0 Ga. We interpret these data to indicate a craton-wide epigenetic fluid-infiltration event, which exploited the Maquassie Quartz Porphyry (MQP) as the aquifer and metal source.Sr isotopic results for the ore-zone gangue minerals show highly radiogenic ⁸⁷Sr/⁸⁶Sr ratios (>0.710) which support earlier models that the origin of radiogenic Sr isotopic composition in the calcite cements is the felsic tuffs (MQP) of the Ventersdorp Supergroup occurring at deeper levels within the basin. Relationships between δ¹⁸O and δ¹³C performed on carbonate cements within the aquifers are complex: the range in δ¹³C for some of the cements represents a mixture from two sources and with a progression from heavy carbon in the host to somewhat lighter carbon in the cements. Similarly, the lighter δ¹⁸O values have a narrow range indicative of rapid exchanges between hydrous fluid and rock.  相似文献   

Oxygen and hydrogen isotope ratios in tree rings: how well do models predict observed values?     

J.S. Waterhouse  V.R. Switsur  A.C. BarkerA.H.C. Carter  I. Robertson 《Earth and Planetary Science Letters》2002,201(2):421-430

We have measured annual oxygen and hydrogen isotope ratios in the α-cellulose of the latewood of oak (Quercus robur L.) growing on well-drained ground in Norfolk, UK. We compare the observed values of isotope ratios with those calculated using equations that allow for isotopic fractionation during the transfer of oxygen and hydrogen from source water taken by the tree to cellulose laid down in the cambium. The equations constitute a model in which isotopic fractionation occurs during evaporative enrichment within the leaf and during isotopic change between carbohydrates and water in the trunk during cellulose synthesis. From the relationship between isotope ratios in precipitation and α-cellulose, we deduce that the source water used by the tree comprises a constant mixture of groundwater and precipitation, chiefly from the months of May, June and July of the growth year. By selection of isotopic fractionation factors and the degree of isotope exchange within the trunk, we are able to model the observed annual values of oxygen isotope ratios of α-cellulose to a significant level (r=0.77, P<0.01). When we apply the same model to hydrogen isotope ratios, however, we find that, although we can predict the average value over the time series, we can no longer predict the year-to-year variation. We suggest that this loss of environmental signal in the hydrogen isotopes is caused by differences in the kinetic isotope effects of the biochemical reactions involved in the fixation of hydrogen in different positions of the glucose molecule. Owing to these effects, the hydrogen isotope ratios of cellulose can vary in a way not anticipated in current models and hence may induce non-climatic ‘noise’ in the hydrogen isotope time series.  相似文献   

Arsenicosis in Cambodia: Case studies and policy response     

M.L. Sampson  B. Bostick  Hannah Chiew  J.M. Hagan  A. Shantz 《Applied Geochemistry》2008

Naturally occurring As found in groundwaters has been identified to be a problem in at least 10 provinces of Cambodia with Kandal being one of the most heavily impacted. Estimates, using groundwater quality and population data for Kandal Province of Cambodia, suggest that over 100,000 people are at high risk of chronic As exposure. Levels in some areas approach 3500 μg/L, against the Cambodian Standard of 50 μg/L. Considerable work remains to adequately characterize the extent of As hazard and its possible health effects in Cambodia and the region. It is likely that additional populations will develop health problems attributed to As, of particular concern is arsenicosis. The symptoms of arsenicosis have been generally assumed to develop after 8–10 years of consumption of water with elevated As levels, however, new cases discovered in Cambodia have been identified with exposure times as short as 3 years. The rapid onset of arsenicosis may be attributed to contributing risk factors related to socioeconomic status, including malnutrition. It is thus imperative to develop strategies to rapidly identify possible regions of enrichment, to minimize exposure to As-rich waters, and to educate affected populations. To date the response to the As hazard has been led by the Ministry of Rural Development in cooperation with international organizations and NGOs, to identify at risk areas, and educate communities of the risk of As-rich water. However better coordination between government bodies, NGOs and donor agencies active in the field of water supply and treatment is essential to minimize future As exposure.  相似文献   

Inter‐annual variability in the effects of riparian woodland on micro‐climate,energy exchanges and water temperature of an upland Scottish stream          下载免费PDF全文

Grace Garner  Iain A. Malcolm  Jonathan P. Sadler  Colin P. Millar  David M. Hannah 《水文研究》2015,29(6):1080-1095

The influence of riparian woodland on stream temperature, micro‐climate and energy exchange was investigated over seven calendar years. Continuous data were collected from two reaches of the Girnock Burn (a tributary of the Aberdeenshire Dee, Scotland) with contrasting land use characteristics: (1) semi‐natural riparian forest and (2) open moorland. In the moorland reach, wind speed and energy fluxes (especially net radiation, latent heat and sensible heat) varied considerably between years because of variable riparian micro‐climate coupled strongly to prevailing meteorological conditions. In the forested reach, riparian vegetation sheltered the stream from meteorological conditions that produced a moderated micro‐climate and thus energy exchange conditions, which were relatively stable between years. Net energy gains (losses) in spring and summer (autumn and winter) were typically greater in the moorland than the forest. However, when particularly high latent heat loss or low net radiation gain occurred in the moorland, net energy gain (loss) was less than that in the forest during the spring and summer (autumn and winter) months. Spring and summer water temperature was typically cooler in the forest and characterised by less inter‐annual variability due to reduced, more inter‐annually stable energy gain in the forested reach. The effect of riparian vegetation on autumn and winter water temperature dynamics was less clear because of the confounding effects of reach‐scale inflows of thermally stable groundwater in the moorland reach, which strongly influenced the local heat budget. These findings provide new insights as to the hydrometeorological conditions under which semi‐natural riparian forest may be effective in mitigating river thermal variability, notably peaks, under present and future climates. © 2014 The Authors. Hydrological Processes published by John Wiley & Sons Ltd.  相似文献   

Recent climatic trends and linkages to river discharge in Central Vietnam   总被引：1，自引：0，他引：1       下载免费PDF全文

Maxime Souvignet  Patrick Laux  Jim Freer  Hannah Cloke  Dang Quang Thinh  Tran Thuc  Johannes Cullmann  Alexandra Nauditt  Wolfgang‐Albert Flügel  Harald Kunstmann  Lars Ribbe 《水文研究》2014,28(4):1587-1601

In this study, change in rainfall, temperature and river discharge are analysed over the last three decades in Central Vietnam. Trends and rainfall indices are evaluated using non‐parametric tests at different temporal levels. To overcome the sparse locally available network, the high resolution APHRODITE gridded dataset is used in addition to the existing rain gauges. Finally, existing linkages between discharge changes and trends in rainfall and temperature are explored. Results are indicative of an intensification of rainfall (+15%/decade), with more extreme and longer events. A significant increase in winter rainfall and a decrease in consecutive dry days provides strong evidence for a lengthening wet season in Central Vietnam. In addition, trends based on APHRODITE suggest a strong orographic signal in winter and annual trends. These results underline the local variability in the impacts of climatic change at the global scale. Consequently, it is important that change detection investigations are conducted at the local scale. A very weak signal is detected in the trend of minimum temperature (+0.2°C/decade). River discharge trends show an increase in mean discharge (31 to 35%/decade) over the last decades. Between 54 and 74% of this increase is explained by the increase in precipitation. The maximum discharge also responds significantly to precipitation changes leading to a lengthened wet season and an increase in extreme rainfall events. Such trends can be linked with a likely increase in floods in Central Vietnam, which is important for future adaptation planning and management and flood preparedness in the region. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Numerical modelling of spatio-temporal thermal heterogeneity in a complex river system     

Jonathan L. Carrivick  Lee E. Brown  David M. Hannah  Andy G.D. Turner 《Journal of Hydrology》2012

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