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1.
Major mountain environments of the world are delineated and all their protected areas (MTNPA) are listed by IUCN categories. MTNPA are those places subjected to nature conservation such as national parks and nature reserves. A total of 442 IUCN Category I–IV areas with a minimal size of 10,000 ha and a minimal relief of 500 m are listed. These MTNPA constitute 42 percent of the world's area devoted to nature conservation. Summaries of the mountain protected areas in each biogeographical realm are given, sites of international importance are identified and observations are made on lacunae. The review concludes with six recommendations for more and better managed mountain parks and reserves. 相似文献
2.
《Geoforum》2015
The World Conservation Union (IUCN) publishes the Red List of Threatened Species, the most authoritative information available globally on the conservation status of species. However, the status of globally threatened species remains controversial at local levels because many of them are not protected as part of national statutory law. Such anomalies are examples of controversies in implementing the much-hyped environmental slogan “think globally, act locally”. Here we provide a comparative review between globally threatened species as listed by the IUCN Red List found in Nepal and those of nationally protected species under Nepalese law. We discovered a significantly higher diversity of globally threatened mammals and birds in Nepal than would be expected relative to their global ratios. We established remarkable disparities in species conservation in Nepal: (1) a large number (an average of 85% of species of five taxonomic groups: mammals, birds, amphibians, fishes and reptiles) of IUCN-listed globally threatened species found in Nepal are not protected by national law; (2) most protected species listed are mammals (70%), but more than half of globally-threatened mammals found in Nepal are not protected; and (3) amphibians and fish are not protected, although they represent 12% of the total number of globally-threatened species found in the country. Such large gaps in Nepalese conservation law are an indication of unresponsive and inefficient conservation planning. The Government of Nepal and international conservation partners should: (1) emphasize knowledge-based conservation strategies for all taxonomic groups; and (2) prioritize updating the lists of protected species. 相似文献
3.
W. Cullen Sherwood 《Environmental Geology》1989,14(2):99-106
Loading trends and sources of CI– in the South Fork of the Shenandoah River, Virginia were analyzed for the period 1929–1982. CI– has increased from approximately 2 mg/L (2,776 tons/yr) to over 10 mg/L (14,256 tons/yr). Natural CI– is estimated to be 1.01 mg/L (1,388 tons/yr) with precipitation providing 0.99 mg/L and rocks 0.02 mg/L. From 1929 to 1949 CI– concentrations were relatively constant and independent of discharge, conforming to the Type II curve of Davis and Zobrist (1978), indicative of natural or relatively uncontaminated streams. Since 1952 CI– concentrations increased exponentially as river discharge decreases conforming to the Type I curve of Davis and Zobrist for polluted streams. Since 1965 anthropogenic CI– loading at 12,868 tons/yr has remained relatively constant. Four major sources contribute 92.2 percent (11,871 tons/yr) of the anthropogenic CI–: (1) deicing salts—4,149 tons/yr, (2) domestic sewage—3,015 tons/yr, (3) livestock and poultry wastes—2,458 tons/yr, and (4) commercial fertilizers—2,249 tons/yr. 相似文献
4.
玉龙雪山位于青藏高原东南缘,它以其独特的地貌特征而引人关注。其顶部为一古残留面,在30×20km2范围内海拔>5000m的山峰达18座,高出其周围地区平均海拔近1000m。在分析该区地质地貌特征基础上,我们根据岩石圈弹性挠曲地壳均衡理论,以较保守的残留面海拔4250m为当时金沙江下切玉龙雪山的基准面,结果表明:由于虎跳峡中大规模物质剥蚀而引起玉龙雪山地壳均衡反弹,导致山体隆升了468m,这完全是侵蚀作用对于玉龙雪山隆升的贡献。而玉龙雪山与周围地区的剩余地势高差,主要由正断层等构造作用造成。因此,玉龙雪山的隆升是侵蚀与构造作用共同控制的结果。该区最大量地壳均衡反弹的触发机制是5.02.5M a期间玉龙雪山东西两侧正断层的发生。另一方面,作为玉龙雪山的南东延伸部分——点苍山（4122m）在5.02.5M a同样也发生了构造伸展,但是没有遭受大规模的河流侵蚀作用,因此其海拔相对要低很多。这进一步说明地壳均衡反弹导致了玉龙雪山隆升,并加大了玉龙雪山与点苍山在原有基础上的地势高差。 相似文献
5.
The intraplate Ancestral Rocky Mountains of western North America extend from British Columbia, Canada, to Chihuahua, Mexico, and formed during Early Carboniferous through Early Permian time in response to continent–continent collision of Laurentia with Gondwana—the conjoined masses of Africa and South America, including Yucatán and Florida. Uplifts and flanking basins also formed within the Laurentian Midcontinent. On the Gondwanan continent, well inboard from the marginal fold belts, a counterpart structural array developed during the same period. Intraplate deformation began when full collisional plate coupling had been achieved along the continental margin; the intervening ocean had been closed and subduction had ceased—that is, the distinction between upper versus lower plates became moot. Ancestral Rockies deformation was not accompanied by volcanism. Basement shear zones that formed during Mesoproterozoic rifting of Laurentia were reactivated and exerted significant control on the locations, orientations, and modes of displacement on late Paleozoic faults.Ancestral Rocky Mountain uplifts extend as far south as Chihuahua and west Texas (28° to 33°N, 102° to 109°W) and include the Florida-Moyotes, Placer de Guadalupe–Carrizalillo, Ojinaga–Tascotal and Hueco Mountain blocks, as well as the Diablo and Central Basin Platforms. All are cored with Laurentian Proterozoic crystalline basement rocks and host correlative Paleozoic stratigraphic successions. Pre-late Paleozoic deformational, thermal, and metamorphic histories are similar as well. Southern Ancestral Rocky Mountain structures terminate along a line that trends approximately N 40°E (present coordinates), a common orientation for Mesoproterozoic extensional structures throughout southern to central North America.Continuing Tien Shan intraplate deformation (Central Asia) has created an analogous array of uplifts and basins in response to the collision of India with Eurasia, beginning in late Miocene time when full coupling of the colliding plates had occurred. As in the Laurentia–Gondwana case, structures of similar magnitude and spacing to those in Eurasia have developed in the Indian plate. Within the present orogen two ancient suture zones have been reactivated—the early Paleozoic Terskey zone and the late Paleozoic Turkestan suture between the Siberian and East Gondwanan cratons. Inverted Proterozoic to early Paleozoic rift structures and passive-margin deposits are exposed north of the Terskey zone. In the Alay and Tarim complexes, Vendian to mid-Carboniferous passive-margin strata and the subjacent Proterozoic crystalline basement have been uplifted. Data on Tien Shan uplifts, basins, structural arrays, and deformation rates guide paleotectonic interpretations of ancient intraplate mountain belts. Similarly, exhumed deep crustal shear zones in the Ancestral Rockies offer insight into partitioning and reorientation of strain during contemporary intraplate deformation. 相似文献
6.
Boulder Mountain, located in South Central Utah, is one of several mountain ranges on the Colorado Plateau that was glaciated during the late Pleistocene. Using 3He exposure-age dating (corrected for non-cosmogenic 3He with shielded samples), we determined 3He exposure-ages for boulders from the most well-preserved moraines in the Fish Creek drainage of Boulder Mountain. 3He exposure-ages indicate a last glacial maximum (LGM) advance ∼23,100 ± 1300 to 20,000 ± 1400 yr ago and a later and smaller advance ∼16,800 ± 500 to 15,200 ± 500 yr ago. This chronology is very similar to other cosmogenic glacial chronologies from the Western U.S. and suggests that the timing of glacial advance and retreat on the Colorado Plateau was generally in phase with the rest of the Western U.S. during the late Pleistocene. 相似文献
7.
8.
Field setting,mineralogy, chemistry,and genesis of arc picrites,New Georgia,Solomon Islands 总被引：5，自引：0，他引：5
W. R. H. Ramsay A. J. Crawford J. D. Foden 《Contributions to Mineralogy and Petrology》1984,88(4):386-402
The field setting, petrography, mineralogy, and geochemistry of a suite of picrite basalts and related magnesian olivine tholeiites (New Georgia arc picrites) from the New Georgia Volcanics, Kolo caldera in the active ensimatic Solomon Islands arc are presented. These lavas, with an areal extent in the order of 1002 km and almost 1 km thick in places, are located close to the intersection of the Woodlark spreading zone with the Pacific plate margin. They contain abundant olivine (Fo94-75) and diopside (Cr2O3 1.1-0.4%, Al2O3 1–3%), and spinels characterised by a large range in Cr/(Cr+Al) (0.85–0.46) and Mg/(Mg+ Fe++) (0.65–0.1). The spinels are Fe+++ rich, with Fe+++/ (Fe++++Cr+Al) varying from 0.06 to 1.0. A discrete group of spinels with the highest Cr/(Cr+Al) (0.83–0.86) and lowest Fe+++ contents are included in the most Mg-rich olivine (Fo91–94) and both may be xenocrystal in origin.The lavas, which range between 10–28% MgO, define linear trends on oxide (element) — MgO diagrams and these trends are interpreted as olivine (0.9) clinopyroxene (0.1) control lines. For the reconstructed parent magma composition of these arc picrites, ratios involving CaO, Al2O3, TiO2, Zr, V and Sc are very close to chondritic. REE patterns are slightly LREE — enriched ((La/Sm)N 1.3–1.43) and HREE are flat. All lavas show marked enrichments in K, Rb, Sr, Ba, and LREE relative to MORB with similar MgO contents, but the TiO2 content of the proposed parent magma is close to those of postulated primary MORB liquids. It is proposed that the arc parent magma was produced by partial melting of sub-oceanic upper mantle induced by the introduction of LILE — enriched hydrous fluids derived by dehydration and/or partial melting of subducted ocean crust and possibly minor sediments. 相似文献
9.
Soil erosion risk assessment of the Keiskamma catchment,South Africa using GIS and remote sensing 总被引：4，自引：2，他引：2
Paidamwoyo Mhangara Vincent Kakembo Kyoung Jae Lim 《Environmental Earth Sciences》2012,65(7):2087-2102
This paper examines the soil loss spatial patterns in the Keiskamma catchment using the GIS-based Sediment Assessment Tool
for Effective Erosion Control (SATEEC) to assess the soil erosion risk of the catchment. SATEEC estimates soil loss and sediment
yield within river catchments using the Revised Universal Soil Loss Equation (RUSLE) and a spatially distributed sediment
delivery ratio. Vegetation cover in protected areas has a significant effect in curtailing soil loss. The effect of rainfall
was noted as two pronged, higher rainfall amounts received in the escarpment promote vegetation growth and vigour in the Amatole
mountain range which in turn positively provides a protective cover to shield the soil from soil loss. The negative aspect
of high rainfall is that it increases the rainfall erosivity. The Keiskamma catchment is predisposed to excessive rates of
soil loss due to high soil erodibility, steep slopes, poor conservation practices and low vegetation cover. This soil erosion
risk assessment shows that 35% of the catchment is prone to high to extremely high soil losses higher than 25 ton ha−1 year−1 whilst 65% still experience very low to moderate levels of soil loss of less than 25 ton ha−1 year−1. Object based classification highlighted the occurrence of enriched valley infill which flourishes in sediment laden ephemeral
stream channels. This occurrence increases gully erosion due to overgrazing within ephemeral stream channels. Measures to
curb further degradation in the catchment should thrive to strengthen the role of local institutions in controlling conservation
practice. 相似文献
10.
Zircons in basement rocks from the eastern Wyoming province (Black Hills, South Dakota, USA) have been analyzed by ion microprobe (SHRIMP) in order to determine precise ages of Archean tectonomagmatic events. In the northern Black Hills (NBH) near Nemo, Phanerozoic and Proterozoic (meta)sedimentary rocks are nonconformably underlain by Archean biotite–feldspar gneiss (BFG) and Little Elk gneissic granite (LEG), both of which intrude older schists. The Archean granitoid gneisses exhibit a pervasive NW–SE-trending fabric, whereas an earlier NE–SW-trending fabric occurs sporadically only in the BFG, which is intruded by the somewhat younger LEG. Zircon crystals obtained from the LEG and BFG exhibit double terminations, oscillatory zoning, and Th/U ratios of 0.6±0.3—thereby confirming a magmatic origin for both lithologies. In situ analysis of the most U–Pb concordant domains yields equivalent 207Pb/206Pb ages (upper intercept, U–Pb concordia) of 2559±6 and 2563±6 Ma (both ±2σ) for the LEG and BFG, respectively, which constrains a late Neoarchean age for sequential pulses of magmatism in the NBH. Unzoned (in BSE) patches of 2560 Ma zircon commonly truncate coeval zonation in the same crystals with no change in Th/U ratio, suggesting that deuteric, fluid-assisted recrystallization accompanied post-magmatic cooling. A xenocrystic core of magmatic zircon observed in one LEG zircon yields a concordant age of 2894±6 Ma (±2σ). This xenocryst represents the oldest crustal material reported thus far in the Black Hills. Whether this older zircon originated as unmelted residue of 2900 Ma crust that potentially underlies the Black Hills or as detritus derived from 2900 Ma crustal sources in the Wyoming province cannot be discerned. In the southern Black Hills (SBH), the peraluminous granite at Bear Mountain (BMG) of previously unknown age intrudes biotite–plagioclase schist. Zircon crystals from the BMG are highly metamict and altered, but locally preserve small domains suitable for in situ analysis. A U–Pb concordia upper intercept age of 2596±11 Ma (±2σ) obtained for zircon confirms both the late Neoarchean magmatic age of the BMG and a minimum age for the schist it intrudes. Taken together, these data indicate that the Neoarchean basement granitoids were emplaced at 2590–2600 Ma (SBH) and 2560 Ma (NBH), most likely in response to subduction associated with plate convergence (final assembly of supercontinent Kenorland?). In contrast, thin rims present on some LEG–BFG zircons exhibit strong U–Pb discordance, high common Pb, and low Th/U ratios—suggesting growth or modification under hydrothermal conditions, as previously suggested for similar zircons from SE Wyoming. The LEG–BFG zircon rims yield a nominal upper intercept date of 1940–2180 Ma, which may represent a composite of multiple rifting events known to have affected the Nemo area between 2480 and 1960 Ma. Together, these observations confirm the existence of a Paleoproterozoic rift margin along the easternmost Wyoming craton. Moreover, the 2480–1960 Ma time frame inferred for rifting in the Black Hills (Nemo area) corresponds closely to a 2450–2100 Ma time frame previously inferred for the fragmentation of supercontinent Kenorland. 相似文献
11.
The distribution of snow in Israel 总被引：1，自引：0，他引：1
The area researched is characterized by changes in the weather according to fluctuations in the world pressure belts throughout the year. The temperature climate in this region is typified in winter by changes in the pressure system from cyclonic to anti-cyclonic conditions in spells of about 5 days.When Israel is under the influence of a low pressure system, and the 500 mb surfaces are approximately 250 m lower than average, the temperatures along the vertical cross-sections are 6° – 8° C lower than average on rainy days, then snow may be expected in various sections of the country.This paper investigated the 35 years period from 1938/9 to 1971/2, concentrating on two mountain stations — Jerusalem in the centre of the country and Mt. Kena'an in the north —because of the high snow incidence and its greater regularity than other stations.The conclusions are as follows: The maximum number of days of snow (between 2/3 and 3/4 of the annual total) is noted at all stations during January and February, although there are also years in which there was snow but not during those months. Regional devision of the snowy days indicates that the number increases with altitude, and decreases from north to south.Snowfall in regions which have lower incidence is less stable and given to greater fluctuations. There was no indication of periodity of the number of days of snow per season, nor did it appear that a very snowy year followed a dry one.Investigation of the lenght of the snowy and the number of days of snowfall does not indicate any connection between them, and there may well be a long season with few days of snow, or a short one with relatively many snowy days.Comparison between the shorter period of readings — from 1938/9 till 1971/2 — and the longer one — from 1860/1 till 1971/2 (111 years) — at the Jerusalem station shows the same trends, which reinforce the conclusions presented above. 相似文献
12.
Northcote TG 《GeoJournal》1996,40(1-2):127-133
Perhaps nowhere in Canada, if indeed in North America, could two adjacent watershed basins be selected which show such remarkable differences in their historical and recent response to human population growth effects. One — the Fraser — covers some 234,000 km2 (about one quarter of the province of British Columbia) and houses nearly two-thirds of its total population. The other — the Okanagan — forms a small part (some 14,000 km2) of the upper Columbia River drainage in Canada. Native Indian populations at maximum before European contact in the late 1700s were about 50,000 in the Fraser basin and probably less than a fifth of that in the Okanagan. Present total resident populations of the Fraser and Okanagan basins, about 2 million and 1\4 million respectively, have greatly different distributions and thereby effects within the watersheds they occupy. In addition seasonal tourist populations have important and differential impacts within the two watersheds. Expression of these effects on water, fisheries and other aquatic resources of the two basins are explored along with possibilities and suggestions for their sustainable development. The latter, despite some glimmers of hope, will not be tenable without major changes in public attitude, in government policy at all levels, and in other measures which to many may seem impossible. 相似文献
13.
The petrochemistry of kimberlites from Yakutia and Lesotho has been studied using a silicate melt model with the SiO2, CO2 and H2O derivatives as the main anions.A model has been developed, according to which the dissolution of H2O in an ultramafic melt results in orthosilicates (H2SiC
4
-2
, H3SiO
4
–
, H4SiO4 etc.) rather than metasilicates, while the dissolution of CO2 produces additional hydrocarbonate complexes. It suggests that at high PCO
2
1
, and where the orthosilicic calcium salt clusters are likely to be present in the magma, the kimberlite melt can break down into carbonate and silicate liquids. Therefore, the composition of kimberlite magma will be determined by the H2O/CO2 ratio under the relatively constant fluid pressure. This can be seen from the distinct fluidrs trend in the H2O-CO2-SiO2 diagram for the Yakutia and Lesotho diamond-bearing kimberlites. The H2O/CO2 ratio changes with the liquidus temperature along this trend (Perchuk and Vaganov 1977) which suggests that liquid immiscibility predominates over the simple CO2 solubility in the melts of kimberlite composition. The well-known Boyd's diagrams for the equilibrium PT-conditions in peridotites have been applied along with new experimental data to natural Cpx and Opx, and the PT-parameters were correlated for peridotite inclusions in kimberlite pipes in Yakutia and Lesotho. The liquidus temperatures for the extrapolated area of these correlations gave depths (pressures) at which kimberlite magmas are formed (200–250 km).The hypothesis on SiO2 partitioning between the melt and the fluid was used to calculate the composition of dry initial kimberlite which characterised the average mantle composition: SiO2 — 45.12; TiO2 — 2.49; Al2O3 — 3.58; Cr2O3 — 0.12; FeO — 9.32; MnO — 0.16; CoO — 0.11; MgO — 23.47; CaO — 13.44; Na2O — 0.20; K2O — 1.12; P2O5 — 0.69; S — 0.18; sum — 100 wt.%. This kimberlite is close to wehrlite in composition. 相似文献
14.
N.A. Tchepkaia G.A. Chelnokov A.A. Karabtsov I.A. Tarasenko 《Journal of Geochemical Exploration》2006,88(1-3):148
This study presents new data on major, trace and REE element concentration of groundwaters in Lastochka spa located in the northern part of Primorye, Far East of Russia. The studied area is characterized by two types of groundwaters issued from a spring and wells: fresh waters with low mineralization (Total Dissolved Solids is up to 400 mg/l) and high pCO2 waters with high mineralization (TDS is up to 4700 mg/l). New data and previous δ13C(TIC), oxygen (δ18O) and hydrogen (δ2H) isotope data indicate that these waters result from meteoric water infiltration in the Sikhote–Alin mountain, circulating at shallow depths in sedimentary rocks. CO2 in groundwater is of mantle origin. 相似文献
15.
Margaret Johston 《GeoJournal》1989,19(3):323-328
An important component of recreation in mountain areas is the experience of risk. Visitors to such places may be seeking the challenge provided by risk, but they may also experience the negative side of risk — accident and injury. International and domestic visitors to mountain lands may have differing experiences of risk. Indeed, it has been suggested frequently in New Zealand that international visitors face considerably more danger than do New Zealanders in mountain recreation. This view is pursued in an examination of one of the negative outcomes of risk — fatal accidents.Coroners' reports form the basis of a comparative study of such negative outcomes for the two groups. Patterns and trends are elaborated in an exploration of the number, location and cause of fatalities, and the activity of the deceased. Differences between two groups are discussed, as are some reasons why the impression that international visitors face more danger exists. 相似文献
16.
The qanat water supply technology, which gravity drains mountain aquifers into valleys, is considered as a culturally appropriate
and ecological sustainable design to meet northern Cyprus’ drinking water development needs. This research estimates the boundary
and water budget for the proposed qanat recharge area of 370 km2, which is in the upper elevations of the limestone dominated Five Finger Mountain Range. The mountain drainage was analyzed
using global elevation data from the Shuttle Ranging Topography Mission (SRTM). Efforts to use Tropical Rainfall Measuring
Mission (TRMM) annual precipitation for water budget inputs failed due to extreme error when tested against 10–30 years of
meteorological station data; TRMM under-estimated depths on the narrow mountain peaks. Gage records, while few in number,
were area averaged to set average annual precipitation inputs at 530 mm year−1. Evaporation was estimated using a complementary relationship areal evapotranspiration (CRAE) model, setting average atmospheric
outputs at 221 mm year−1. Recharge to the qanat aquifer was set by subtracting evaporation from precipitation, and then allocating 50% of the remaining
water to environmental services. At 25% development, the qanat system supplies 14 mm3 year−1 of water, meeting the drinking water deficit of 13 mm3. 相似文献
17.
Spatial change detection of glacial lakes in the Koshi River Basin,the Central Himalayas 总被引：2，自引：0，他引：2
Region warming and the resulting ongoing deglaciation have led to the formation of new glacial lakes and expansion of existing glacial lakes. For giving an overview of the distribution and expansion of glacial lakes in the Koshi River Basin (KRB) between the Central China and Nepal Himalayas in the recent 10 years, this paper aimed to analyze and assess recent spatial variability of glacial lake changes in the KRB, Central Himalayas using two inventory data of glacial lake in 2001 and 2010 in Nepal and Landsat TM/ETM+ data for the 1990s, 2000 and 2009 on the Chinese section of the KRB. The datasets show that there are 1,203 glacial lakes with a total area of 118.54 km2 in the KRB in 2009, in which 599 lakes are mapped in the Nepalese section of the KRB with a total of 25.92 km2, and 604 lakes in the Chinese section of the KRB with a total area of 92.62 km2. From 2000 to 2009, the total number of glacial lakes decreased from 1,668 to 1,203 with a reduction of 45.86 % in the KRB, whereas the total lake areas expanded by 10.60 % (i.e. 0.72 km2/a), from 111.35 to 118.54 km2 between 2000, 2001 and 2009, 2010. Especially, 17 lakes are identified as potentially dangerous glacial lakes (PDGLs) by International Centre for Integrated Mountain Development (ICIMOD) on the Nepalese section of the KRB in 2009. In the same period, 23 PDGLs are also identified on the Chinese section of the KRB and the total area increased by 77.46 % (i.e. 0.37 km2/a) from 1990 to 2010 and the expansion rate is significantly higher than 39 % (0.19 km2/a) of non-PDGLs. Therefore, there is a need for promoting the awareness of the hazard potential of glacier lakes to support proper planning of mitigation and adaptation strategies in this context. 相似文献
18.
Françoise Elbaz-Poulichet Attila Nagy Tibor Cserny Piroska Pomogyi 《Aquatic Geochemistry》1996,2(4):379-402
Mn, Sr, Ba, Rb, Cu, Zn, Pb and Cd concentrations have been measured seasonally in the water and deposited sediments of the system comprising: Zala river (main input) — Lakes Kis-Balaton 1 and 2 (small artificial lakes created in a former bay of Lake Balaton) — Keszthely bay (hypertrophic part of Lake Balaton). The concentrations of the trace elements together with pH, alkalinity, dissolved cations (Ca2+, Mg2+, Na+, and K+), dissolved inorganic ligands (Cl–, SO4
2–), particulate Al, Ca, inorganic and organic carbon are used to assess the contamination of the study area and biogeochemical processes controlling trace element concentrations. Thermodynamic speciation calculations have also been utilized to enhance our understanding of the system. In the sediments Rb, Ba, Cu and Zn concentrations were mainly controlled by the abundance of the aluminosilicate fraction. Strontium was mainly associated with the calcium carbonate fraction. The aluminosilicate fraction constitutes a major sink for Mn and Cd but the concentration of these elements are also strongly related to calcite precipitation. The main processes that control the dissolved distribution of trace elements in the Balaton system were: solid phase formation (carbonate) for Mn; coprecipitation with calcite for Sr, Ba, Rb and possibly Mn and Cd; adsorption/desorption processes (pH dependent) for Zn and Pb; solubilization of Mn and precipitation of Cd and Cu in reed covered wetland areas where anoxic conditions were probably existing during the warm season. A preliminary budget of atmospheric and river input to Lake Balaton has also been outlined. Although Lake Balaton, is subjected to anthropogenic inputs mainly from agricultural and domestic activities, their impact on trace element concentrations in the Balaton system is very limited due to the efficiency of removal processes (i.e. adsorption and co-precipitation) and to high sedimentation rates and strong sediment re-suspension. Anthropogenic inputs are only detected for Pb. 相似文献
19.
Summary The crystal structure of scotlandite —a=4.505(2),b=5.333(2),c=6.405(6) Å, =106.24(3)o; space groupP21/m; cell content 2 {PbSO3} — was determined from singlecrystal X-ray diffractometer data. Scotlandite is isotypic with molybdomenite, PbSeO3. Lead is coordinated to nine oxygen atoms with Pb-Oav=2.75 Å, and possibly further to one sulphur atom with Pb–S=3.46 Å. The average S–O distance in the pyramidal SO3 group is 1.52 Å. The structural relationships to cerussite, PbCO3, are discussed.
With 2 Figures 相似文献
Die Kristallstruktur des Scotlandits, PbSO3
Zusammenfassung Die Kristallstruktur des Scotlandits —a=4,505(2),b=5,333(2),c=6,405(6) Å, =106,24(3)o; RaumgruppeP21/m; Zellinhalt 2 {PbSO3} — wurde aus Einkristall-Röntgendiffraktometerdaten bestimmt. Scotlandit ist mit Molybdomenit, PbSeO3, isotyp. Blei wird von neun Sauerstoffatomen mit Pb–Oav=2,75 Å und möglicherweise zusätzlich von einem Schwefelatom mit Pb–S=3,46 Å koordiniert. Der durchschnittliche S–O-Abstand in der pyramidalen SO3-Gruppe mißt 1,52 Å. Die strukturellen Beziehungen zu Cerussit, PbCO3, werden diskutiert.
With 2 Figures 相似文献
20.
Nontronite, limonite (with opal) and vivianite are forming at present in the aereated, shallower parts (water depths <250 m) of Lake Malawi. They overlie diatomite or coarse grained clastic sediments. Our investigations indicate a precipitation of nontronite and limonite (and opal) at the sediment/oxic water interface from geothermal solutions rich in SiO2 percolating through the sedimentary fill of the basin. Under reducing conditions and a pH less than 7 (as occurring in the deeper parts of our sediment cores) iron and manganese are leached and discharged into the lake. In the anoxic parts of the lake (water depth greater than 250 m) Fe3+- and Mn3+-hydroxide are precipitated within the lake's water in the mixing zone of the aerobic with the anaerobic water bodies. High dispersion and a strong supply of detrital material, however, prevent a stronger enrichment of the hydroxides in the sediment. The formation of vivianite can be explained by a dissolution of Ca-phosphate (fish debris) within the sediment and a re-deposition as Fe-phosphate in the uppermost sediment layers under reducing but slightly alkaline conditions. The results of our investigations on Recent iron formation in Lake Malawi offer an explanation for the genesis of certain sedimentary iron ores in the geological past. They indicate that a formation of iron-rich sediments — including the silicate facies — is not restricted to the marine environment.
Zusammenfassung Nontronit, Limonit (und Opal) sowie Vivianit werden an zahlreichen Stellen des südlichen Malawi-Sees in Wassertiefen bis 250 m (aerober Bereich) abgeschieden und bilden dort die jüngste sedimentäre Einheit über Diatomit oder grobklastischem Sediment. Es muß angenommen werden, daß die Bildung der Eisenmineralien aus geothermalen Lösungen erfolgt, die reich an gelöster Kieselsäure und Fe2+ (untergeordnet Mn2+) sind, wobei Eisen und Mangan aus dem Sediment selber stammen, da heiße Quellen außerhalb des Malawi-Sees diese Elemente nicht enthalten. Die Auslösung von Eisen und Mangan erfolgt durch saure Lösungen im reduzierenden Milieu unter Bedingungen, wie sie im tieferen Teil der Sediment-Kerne angetroffen wurden (pH bis 3,6!). Beim Zusammentreffen dieser Lösungen mit dem sauerstoffhaltigen, schwach alkalischen Wasser des Malawi-Sees kommt es zur Ausfällung von Nontronit oder — bei wahrscheinlich höherem Redox-Potential — von Limonit und Opal. Beim Austritt der Fe2+, Mn2+- und SiO2-reichen Lösungen in den anaeroben Teil des Malawi-Sees (Wassertiefen größer als 250 m) unterbleibt zunächst eine Ausfällung. Erst in der Mischzone des anoxischen mit dem oxischen Wasserkörper können Fe3+- und Mn3+-Hydroxide ausgeschieden werden, die jedoch infolge hoher Dispergierung und starker Zufuhr von klastischem Material eine starke Verdünnung erfahren. Für die Vivianit-Bildung kann angenommen werden, daß ein in den Sedimenten häufig vorhandener Apatit-Anteil (Fischreste) durch die sauren Lösungen aufgelöst und in den obersten Sedimentschichten (reduzierendes Milieu, pH jedoch >7) zusammen mit Fe2+ der Lösung als Vivianit abgeschieden wird. Die vorliegenden Untersuchungen geben Hinweise auf die Bildung bestimmter fossiler sedimentärer Eisenerze und zeigen gleichzeitig, daß die Genese eisenreicher Sedimente — auch von silikatischem Fazies-Typ — nicht an den marinen Ablagerungsraum gebunden ist.相似文献