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1.
An early Holocene lake sediment record from central Nova Scotia contains a minerogenic oscillation that is closely correlative with the 8.2 kyr event (ca. 8200 cal. yr BP), an event that has not been reported elsewhere in Atlantic Canada. A variety of biological and sedimentological indicators have been examined to characterise autochthonous and allochthonous changes that occurred during this time. The minerogenic upper oscillation (UO, ca. 8400 cal. yr BP) is marked by an increase in the chrysophyte:diatom ratio. Following the oscillation, the diatom community reflects a shift to more productive, less acidic conditions. The pollen record shows no major response to this short‐lived event. Lithostratigraphic analyses indicates that the UO is characterised by an increase in clastic content, magnetic susceptibility and mean sediment grain size, all indicators of changing environmental conditions, most likely the result of regional cooling. The Taylor Lake record adds to a growing body of evidence for a widespread, hemispheric climate oscillation at 8.2 kyr. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

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3.
The Sydney Coalfield is the largest in Atlantic Canada in which about 100 coal mines with varied lifespan have been opened since 1720. In the Glace Bay sub-basin, coal seams subcrop close to the Atlantic coast and dip seaward. Coal has been mined at 〉1200 m depth and 11 km from the coastline. Deposited possibly under a marine influence, the coals are enriched in pyrite. During mining abundant acidic sulfates such as melanterite, rozenite, copiapite and halotrichite have accumulated in the underground workings due to pyrite oxidation. The dissolution of these efflorescent salts upon mine flooding at closure gives rise to acidic mine pools wherever insufficient acid-neutralizing materials are present. A major challenge of mine decommissioning in the area is to prevent the discharge of this acidic water into the open ocean. Water monitoring in the 1B Hydraulic System, which consists of ten mines connected at various depths by natural or man-made conduits, shows that the mine pool chemistry varies with the mining practice employed. Although coal has invariably been mined by the room and pillar method, the extent of pillar removal varies from mine to mine. In mines with minimal pillar removal, coal extraction could be as low as 45%, leaving much pyrite for oxidation prior to eventual flooding and an acidic mine pool occurs. In contrast, in mines with extensive pillar removal, coal extraction could amount to 85%, leaving much less pyrite for oxidation. Moreover, the extensive pillar removal caused the collapse of the overlying strata which in some areas include limestone. The infilling of mine workings with carbonate-rich material offsets the effects of acidic effiorescent salts and a mine pool with near-neutral pH results. Geochemical modeling has affirmed the control of local water chemistry by the prevalent mineral assemblage.  相似文献   

4.
Multiple foliar specimens of the Late Pennsylvanian fossil pteridosperm [gymnosperm] Alethopteris zeilleri (Ragot) Wagner were collected from one restricted stratigraphical horizon in the Canadian Sydney Coalfield. Variability of functional-group distribution using FTIR technique was studied in compressions, adaxial versus abaxial cuticles, and in unseparated cuticles as a function of maceration time from 48 to 168 h. The results obtained document spectral variability that could be expected within specimens of one species. For example, CH2/CH3 and Al/ox ratios can differ by as much as 20% of the values. Moreover, the experiments performed confirm that by using a previously established maceration protocol, long maceration periods do not bias FTIR spectra in terms of oxygenation overprinting. The inference that this cuticle is robust, under the given diagenetic level, probably reflects a reassuring degree of chemical fidelity of the Pennsylvanian plant to support Carboniferous chemotaxonomic observations.  相似文献   

5.

Lithofacies in the mid‐Permian Nowra Sandstone indicate a middle/upper shoreface to foreshore environment of deposition under the influence of storm‐generated waves and north‐northeasterly directed longshore currents. Palaeogeographic reconstruction for the Nowra Sandstone portrays a sand‐dominated high energy shelf and offshore shoal forming a sequence thickening seaward away from the western shore of the Sydney Basin. The shoal‐crest at the outer edge of the shelf trends north‐northeast. It is characterized by fine‐ to medium‐grained sandstone with upper flow regime structures and a high proportion of conglomerate, whereas coarser sandstone with lower energy bedforms occurs along the seaward side of the shoal. In the deeper water to the east, the lower Nowra Sandstone becomes rapidly thinner as it passes seaward, via bioturbated storm redeposited sandstone beds, into the shelf deposits of the Wandrawandian Siltstone. This sequence accumulated during a regressive event and the base of the formation becomes progressively younger eastward. The sand may have been supplied by rivers along the western coast but the major source was south of the study area. The lower Nowra Sandstone is separated from the upper part of the formation by an extensive ravinement surface overlain by the Purnoo Conglomerate Member. In contrast to the lower unit, the upper Nowra Sandstone forms a westward thickening wedge that represents a backstepping nearshore sand facies that accumulated during a transgression. The upper Nowra Sandstone passes vertically and laterally eastward into the Berry Siltstone. Thus both boundaries of the Nowra Sandstone are diachronous, first younging eastward and then westward as a response to a regressive‐transgressive episode.  相似文献   

6.
Mesoproterozoic metaplutonic rocks in northern Cape Breton Island,Nova Scotia, occur in a tectonic inlier within the Appalachianorogen. Although they have been multiply metamorphosed and variablydeformed, the petrology and geochemistry of these rocks provideinsight into the tectonomagmatic evolution of easternmost Laurentia.Anorthosite, syenite, and granitoid plutons (1100–980Ma) intruded the Sailor Brook and Polletts Cove River gneisses.New Nd isotopic data are presented from a biotite-rich partof the Sailor Brook gneiss (  相似文献   

7.
黄玉  蔡保新  王宇  李昊熹 《地质通报》2014,33(08):1260-1266
饮水水源水质的人体健康安全是水源是否安全的首要问题。在调查锡矿矿坑水作为个旧市A镇及B矿段锡矿生活区饮用水源情况的基础上,应用国际辐射防护委员会和美国环保署推荐的风险评估模型,开展饮用水的人体健康风险评价。结果表明,水源中重金属致癌物质所引起的健康危害较高,风险值超过了国际辐射防护委员会推荐的最大可接受风险水平,其中以Cr6+和As的致癌风险最大,应优先控制;非致癌物质所引起的健康风险较小,风险值在10-8以下,远低于推荐的最大可接受风险水平。虽然水中重金属含量符合相关标准要求,但是长期饮用对人体存在健康风险。  相似文献   

8.
黄玉  蔡保新  王宇  李昊熹 《地质通报》2014,33(8):1260-1266
饮水水源水质的人体健康安全是水源是否安全的首要问题。在调查锡矿矿坑水作为个旧市A镇及B矿段锡矿生活区饮用水源情况的基础上,应用国际辐射防护委员会和美国环保署推荐的风险评估模型,开展饮用水的人体健康风险评价。结果表明,水源中重金属致癌物质所引起的健康危害较高,风险值超过了国际辐射防护委员会推荐的最大可接受风险水平,其中以Cr6+和As的致癌风险最大,应优先控制;非致癌物质所引起的健康风险较小,风险值在10-8以下,远低于推荐的最大可接受风险水平。虽然水中重金属含量符合相关标准要求,但是长期饮用对人体存在健康风险。  相似文献   

9.
 The seasonal frequency and duration of low pH events at three sites located in southwestern Nova Scotia were analyzed using measured and synthetic daily pH data. The basins varied in size from 0.3 to 300 km2 and were subject to frequent snowmelt events in winter and spring, as well as occasional runoff events during summer and fall. Results showed that, in order to fill in missing data from periods where collection was interrupted, statistical approximations using discharge were not totally acceptable, as generated data consistently missed the extreme values measured. Despite a lack of totally accurate event pH estimates for periods where daily data were missing, analysis showed that in this region, low pH episodes can occur year-round including summer. The highest probabilities of low pH episodes nevertheless occurred in the winter and spring when snowmelts were frequent. Received: 12 November 1999 · Accepted: 18 July 2000  相似文献   

10.
Impacts of climate change have been observed in natural systems and are expected to intensify in future decades (IPCC in Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change IPPC, Geneva, 2014). Governments are seeking to establish adaptive measures for minimizing the effects of climate change on vulnerable citizen groups, economic sectors and critical infrastructure (Adger et al. in Global Environ Change 15(2):77–86, 2005. doi: 10.1016/j.gloenvcha.2004.12.005; Smit and Wandel in Global Environ Change 16(3):282–292, 2006. doi: 10.1016/j.gloenvcha.2006.03.008). Coastal areas are particularly vulnerable to changing conditions due to rising sea levels and storm event intensification that produce new flood exposures (Richards and Daigle in Government of Prince Edward Island, Halifax, Nova Scotia, 2011 http://www.gov.pe.ca/photos/original/ccscenarios.pdf). However, communities oftentimes lack access to locally-relevant climate change information that can support adaptation planning. This research introduces the use of a Geoweb tool for supporting local climate change adaptation efforts in coastal Canadian communities. The Geoweb tool (called “AdaptNS”) is a web-based visualization tool that displays interactive flood exposure maps generated using local climate change projections of sea level rise and storm surge impacts between the years 2000 and 2100. AdaptNS includes participatory features that allow users to identify and share specific locations to protect against present and future coastal flood events. By soliciting feedback from community members, AdaptNS is shown to support local adaptation through the provision of flood exposure visuals, as a platform for identifying adaptation priorities, and as an avenue to communicate local risks to external entities that could facilitate local adaptation initiatives (e.g. upper levels of government). Future Geoweb research directions include improving the visualization of climate change projection uncertainties, the expansion of informational and participation capabilities, and understanding the potential for long-term adoption of Geoweb tools in adaptation decision-making.  相似文献   

11.
Major and trace elements and nitrogen were analysed in 59 Cambrian and Ordovician slates/phyllites of various lithostratigraphic levels within the Meguma Supergroup, 14 Ordovician slates/phyllites of The Ovens gold mineralisation, and 16 Ordovician slates/phyllites of the Eastville Pb-Zn-Cu mineralisation.The fixed nitrogen content and the normative Nfix/K2O ratio of muscovite separates members of the Goldenville (sandstone-greywacke-quartzite dominated) and Halifax Formation (slate-phyllite dominated). Low fixed nitrogen concentration is related to high manganese concentration. Black slates/phyllites of the saddle-reef-type Au-mineralisation in The Ovens area are characterised by high fixed nitrogen and a high normative Nfix/K2O ratio of muscovite. The nitrogen is of secondary hydrothermal origin. Therefore, it might be possible to use the fixed nitrogen as an exploration tool for black slates/phyllite hosted gold mineralisation in Nova Scotia. Mineralised slates/phyllites of the Eastville stratabound Pb-Zn mineralisation cannot be distinguished from nonmineralised time equivalent lithologies on the basis of the fixed nitrogen distribution or the Nfix/K2O ratio of muscovite.  相似文献   

12.
To study arsenic(As) content and distribution patterns as well as the genesis of different kinds of water, especially the different sources of drinking water in Guanzhong Basin, Shaanxi province, China, 139 water samples were collected at 62 sampling points from wells of different depths, from hot springs, and rivers. The As content of these samples was measured by the intermittent flowhydride generation atomic fluorescence spectrometry method(HG-AFS). The As concentrations in the drinking water in Guanzhong Basin vary greatly(0.00–68.08 μg/L), and the As concentration of groundwater in southern Guanzhong Basin is different from that in the northern Guanzhong Basin. Even within the same location in southern Guanzhong Basin, the As concentrations at different depths vary greatly. As concentration of groundwater from the shallow wells(50 m deep, 0.56–3.87 μg/L) is much lower than from deep wells(110–360 m deep, 19.34–62.91 μg/L), whereas As concentration in water of any depth in northern Guanzhong Basin is 10 μg/L. Southern Guanzhong Basin is a newly discovered high-As groundwater area in China. The high-As groundwater is mainly distributed in areas between the Qinling Mountains and Weihe River; it has only been found at depths ranging from 110 to 360 m in confined aquifers, which store water in the Lishi and Wucheng Loess(Lower and Middle Pleistocene) in the southern Guanzhong Basin. As concentration of hot spring water is 6.47–11.94 μg/L; that of geothermal water between 1000 and 1500 m deep is 43.68–68.08 μg/L. The high-As well water at depths from 110 to 360 m in southern Guanzhong Basin has a very low fluorine(F) value, which is generally 0.10 mg/L. Otherwise, the hot springs of Lintong and Tangyu and the geothermal water in southern Guanzhong Basin have very high F values(8.07–14.96 mg/L). The results indicate that highAs groundwater in depths from 110 to 360 m is unlikely to have a direct relationship with the geothermal water in the same area. As concentration of all reservoirs and rivers(both contaminated and uncontaminated) in the Guanzhong Basin is 10 μg/L. This shows that pollution in the surface water is not the source of the high-As in the southern Guanzhong Basin. The partition boundaries of the high- and low-As groundwater area corresponds to the partition boundaries of the tectonic units in the Guanzhong Basin. This probably indicates that the high-As groundwater areas can be correlated to their geological underpinning and structural framework. In southern Guanzhong Basin, the main sources of drinking water for villages and small towns today are wells between 110–360 m deep. All of their As contents exceed the limit of the Chinese National Standard and the International Standard(10 μg/L) and so local residents should use other sources of clean water that are 50 m deep, instead of deep groundwater(110 to 360 m) for their drinking water supply.  相似文献   

13.
Saprolitic palaeosurfaces occur at several localities on the granitoid rocks of the South Mountain Batholith of Nova Scotia. There are three ages of saprolites within the study area: pre-Pleistocene, pre-Triassic and pre-Carboniferous. Within these ‘in-place’ weathered horizons, there are remnant ellipsoidal blocks of unweathered granitoid referred to as corestones. These corestones are isolated rounded pods of relatively unweathered material surrounded by rotted granitoid saprolitic material. The weathered material which surrounds these corestones is poorly consolidated and easily eroded. The erosion of these horizons produces a lag deposit that contains many rounded corestones which can be incorporated into subsequent sedimentary units. The rounded boulders, cobbles and pebbles of granite within many of the Pleistocene glacial deposits in southern Nova Scotia are probably related to the incorporation of these saprolite related structures, given the locally derived (within 400 m of the source) nature of the tills. The presence of saprolites at unconformities of various ages on the South Mountain granitoid rocks suggests that incorporation of saprolitic material probably occurred along a number of palaeosurfaces in the past. The recognition of this process has implications for the interpretation of rounded granite-clast conglomerates and quartz-rich sandstones of various ages within the stratigraphic record of eastern Canada. Similar palaeosurfaces elsewhere in the world also have related saprolite derived sedimentary rocks associated with them. In summary, well-rounded spherical pebbles, cobbles and boulders of granitoid material incorporated in sedimentary strata need not have travelled far from source nor are they necessarily recycled from older conglomerates.  相似文献   

14.
Surface soil samples were collected from 161 sites throughout the downtown and suburban area of Beijing, China. The samples were analyzed for polycyclic aromatic hydrocarbons (PAHs) concentrations. Through Kriging analysis, five heavily contaminated zones were identified in the study area. Sources of PAHs in the soil were apportioned using principal factor analysis and multiple linear regression. Three factors were identified representing coal combustion/vehicle emission, coking emission, and petroleum sources, respectively. The relative contributions of the three sources were 48% for coal/vehicle emission, 28% for coking emission, and 24% for petroleum sources. The contributions of total PAHs from the three sources were 16.4, 4.63 and 3.70 ng g−1, respectively. Spatial analysis indicated that the contribution of coal/vehicle sources was higher in the downtown area than in the suburban area, the petroleum sources had a high contribution in the urban area, and the contribution of coking sources was high in the suburban area. The results indicated that PAH contamination in the surface soil in Beijing was closely related to the spatial characteristics of energy consumption and functional zoning. Improvement of the energy consumption structure and relocation of industries with heavy pollution are effective ways to control PAH contamination in surface soil in the area.  相似文献   

15.
The distribution of some trace metals (Cu, Zn, Ni, Co,Fe, Mn) and of DOC over a particulate (> 1 m),a colloidal (size < 0.45 m and molecular weight > 10 kD) and an ultrafiltered fraction (< 10 kD)was determined at several sites on the Thur River,Switzerland, at various times of the year. Thecomplexation of Cu by strong ligands in theultrafiltrate and in the conventional filtrate (<0.45 m) was compared using a ligand-exchange/CSV method.The <0.45 m concentrations of Cu (from anaverage of 7 nM to 24 nM), Zn (<5–23 nM), Ni (5–13 nM),Co (1.5–3 nM) and Mn (7–92 nM)increased downstream. The major part of Cu, Zn, Niand Co usually occurred in the ultrafiltratefraction at all sites, whereas Fe and Mn were mostlyin the particulate fraction, under conditions of lowsuspended matter content (< 10 mg L-1) in theriver. The percentage of metal in the colloidalfraction, with respect to the 0.45-m filtrate,decreased in the order: Cu (median 11%) > Zn Ni(median 5–6%) > Mn Co (median < 5%). DOCalso consisted mostly of molecules in the < 10 kDrange.Cu was strongly complexed by natural organic ligandsin all filtrate and ultrafiltrate samples. A largepart of the strong Cu binding ligands consisted ofcompounds in the < 10 kD range, but colloidalligands with similar properties also occurred. Cu wasdistributed among the dissolved and the colloidalligands, roughly in proportion to organic carbon.The colloidal fraction (as defined here) did notincrease in its proportional amount downstream and wasonly of limited significance in transporting traceelements in the Thur River under low discharge conditions.  相似文献   

16.
The Wentworth plutonic complex, consisting of gabbro and granite, was emplaced in the earliest Carboniferous in the Cobequid shear zone of the northern Appalachians. The plutonic complex is coeval with a 5-km-thick pile of volcanic rocks. Early alkalic A-type granite correlates with thick felsic pyroclastics and minor basalt, which are overlain by 1.5-km-thick basalts that correlate with a large gabbro pluton that is intruded, in turn, by late granites. The basalt and gabbro are Fe-rich tholeiites. The geochemistry of the late granites suggests that they formed by differentiation of a granodioritic magma resulting from assimilation of early granite by the gabbroic magma. The Wentworth plutonic complex lies on the north side of the dextral Rockland Brook fault, near the western tip of wedge-shaped basement block of the Avalon terrane. Field observations of mesoscopic structures and map contacts show that the plutonic bodies at all structural levels are related to transpressive strike–slip faults. Dykes parallel to the mylonitic foliation in the Rockland Brook fault zone and at the contacts between igneous phases suggest that the plutons developed largely through dyke to pluton construction. The plutonism was initiated by dyking related to major faults under transpression that was partitioned into shear zone-bounded blocks, while the sinking of those blocks finally provided the space for mafic magma emplacement. Dyking was active over at least a 10-Ma time period. The overall location of plutonism in the Cobequid shear zone appears related to its position at the intersection of the shear zone bounding the southwestern margin of the Magdalen basin and the E–W transpressional contact of the Avalon and Meguma terranes. Magmatism enabled thermomechanical softening of the crust and the vertical and lateral extrusion of the wedge-shaped basement blocks, whose movement controlled the localisation of the voluminous magmatic activity.  相似文献   

17.
A large part of the Sydney 2000 Olympic Site at Homebush Bay was reclaimed over several decades using an estimated 9 Mt of domestic, commercial and industrial waste. Past activities, such as reclamation of wetlands, land clearing, shoreline remodelling and industrial practices, have caused an adverse environmental impact on the Homebush Bay site. Core samples (n = 4513) collected from the reclaimed lands of Homebush Bay show that, prior to remediation, soil contaminated by heavy metals (Cr, Cu, Pb, Zn) may have posed a threat to groundwater in the area. Mean Pb concentrations from the three land types at the Olympic site range from 65 to 374 μg/g in reclaimed areas, 78–167 μg/g in landfill areas and 44–52 μg/g in non‐infilled areas, respectively. Heavy‐metal concentrations in soils from non‐infilled areas indicate that these parts of the site were uncontaminated. The distribution of heavy metals in soil samples revealed a close association between elevated concentrations and the presence of fill materials at the site. Metal concentrations were frequently above Australian and New Zealand Guidelines for Fresh and Marine Water Quality. The Olympic Coordination Authority's remediation strategy to clean up the Homebush Bay site included consolidating contaminated waste into landscaped hills, which were capped with impermeable clay and thermal destruction of scheduled waste on site. The primary aims of the current study were to provide a scientific foundation for the remediation/rehabilitation of natural systems, and to make a contribution to the Olympic Coordination Authority's Development Plan and Environmental Management System for the site.  相似文献   

18.
The Devonian Winnepegosis and Duperow Formations were examined in well 4-27-11-22W1, located in at the eastern edge of the Williston Basin in Manitoba. The variation in characteristic remanent magnetization (ChRM) direction and magnetic mineral carrier is obvious: the older Winnepegosis Formation has a primary or early post-depositional magnetization held in magnetite or pyrrhotite (n = 15; D = 324.1°, I = − 27.3°, α95 = 10.4°, k = 15.7), whereas the younger Duperow Formation magnetizations are carried by hematite and could be as late as Early Jurassic. The variability may be attributable to the intervening Prairie Evaporite acting as an aquitard to fluid migration.  相似文献   

19.
The Cobequid Highlands in the Canadian Appalachian orogen lie within Avalonia adjacent to the Meguma Terrane. U-Pb (zircon) data show that the age range of voluminous bimodal plutonism in the highlands is from 358 to 363 Ma (late Devonian). This age range is much narrower than that previously suggested by Rb/Sr geochronology and confirms that the Cobequid Highlands preserve the youngest large-scale plutonic event in the Canadian Appalachians. Late Palaeozoic tectonic history of the Appalachian orogen is profoundly influenced by predominantly dextral motion on the Avalon-Meguma terrane boundary. This age of plutonism is coeval with previously published 40Ar/39Ar (muscovite) plateau ages derived from shear zones in the Meguma terrane adjacent to the terrane boundary, which is defined by the Minas fault zone. The NNE trending structural grain of the Appalachian orogen is disturbed in this area by the E-W Minas fault zone and pluton emplacement may have been associated with motion along this terrane boundary.  相似文献   

20.
为掌握黄石市城市边缘区农用土壤环境质量现状,在高密度表、深层土壤采样的基础上,重点分析了土壤重金属元素的分布规律和特征,对其进行了生态环境风险评价,并对重金属元素成因进行了溯源分析。结果表明:研究区土壤中的重金属元素As、Pb、Hg、Cd、Zn、Ni、Cu和Cr含量范围分别为(5.2~155.9)×10-6 、(19.2~426.1)×10-6 、(0.012~1.823)×10-6 、(0.03~4.59)×10-6 、(34.8~529.6)×10-6 、(8.5~86.2)×10-6 、(16.52~104.39)×10-6 和(51.2~145.5)×10-6,平均含量均超过区域土壤环境背景值,且Cd超过农用地土壤风险筛选值。重金属污染物主要集中在表层40 cm以上土壤中,土地类型中以水田和旱地污染为主,污染物中以Cd、As和Pb为主要特征。水田中As、Pb、Cu和Zn为轻度污染,Cd和Hg为中度污染,而Cr和Ni无污染;旱地和林地中As、Pb和Hg为轻度污染,Cd为中度污染,而Cr、Cu、Ni和Zn无污染。多元统计分析表明,研究区土壤中Cr和Ni为自然源成因,与成土母质相关;Cd和Pb、As和Hg主要为人为源污染,与黄石市高强度工矿业生产和硫化物矿物酸化释放有关;而Cu和Zn为混合源成因,部分来源于土壤环境背景,部分来源于人类活动和工业生产排放。  相似文献   

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