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881.
Trace metals in acid sediments and waters, Pimpama catchment, southeast Queensland, Australia 总被引:2,自引:1,他引:2
The Pimpama River floodplain has developed over the last several thousand years as a result of sea-level fluctuations that
shaped the lower catchment and enabled the formation of sedimentary pyrite. The subsequent production of sulfuric acid due
to the oxidation of this pyrite enhances the breakdown of metal-bearing sediments and can lead to leaching of major and trace
metals into the waters of the region. The seasonal pattern of rainfall and current land-use activities are important aspects
that intensify the natural production of acid and influence the release and distribution of metals. To identify the source
and migration of metals in the Pimpama catchment and to understand the impact of pyrite oxidation on the distribution of metals
in sediments and waters, several components of the drainage system were analyzed: bedrock, sediments from river bed and bank,
and water. The elements analyzed in this study (V, Cr, Co, Ni, Cu, Zn and Pb) are all present in the bedrock material which
explains their occurrence in the unconsolidated sediments of the floodplain. These metals concentrate in the upper section
of the sedimentary sequence and their presence is related to clay minerals such as smectite, organic matter and iron phases.
However, Zn, Mo and Co occur in higher amounts than the local background and within standard shale. This comparison suggests
that the diagenetic processes alone cannot explain the higher concentrations and it is concluded that these metals also have
an anthropogenic source. The formation of sulfuric acid creates conditions for higher mobility of some metals, such as Cr,
Co, Ni, Cu, Zn, but does not affect less mobile ones such as Mo and Pb. Over the longterm, the production of acid influences
the breakdown of mineral phases and enhances the process of weathering. Over the short term, every rain event leaches acid
from sediments and mobilizes metals resulting in a substantial reduction in the quality of river water.
Received: 2 October 1998 · Accepted: 16 February 1999 相似文献
882.
Controls on the nature and distribution of an alga in coal mine-waste environments and its potential impact on water quality 总被引:2,自引:0,他引:2
A dominant non-bacterial microorganism that may strongly impact environmental conditions in acid mine drainage at several
Indiana coal mine sites is a single-celled protozoan, Euglena mutabilis. Field data suggest E. mutabilis has high tolerance for elevated total dissolved solids (TDS), to 18 g/l, and acid conditions to pH 1.7. Distribution is restricted
to unmixed effluent pH<4.6, with prolific growth between pH 3.0 and 3.5. Additional factors influencing E. mutabilis include preference for areas with lower mineral/colloidal precipitation rates and a stable substrate of iron-rich precipitates.
Initial studies indicate that in areas of prolific growth it contributes to oversaturation of dissolved oxygen by up to 200%.
The presence of small orange intracellular crystalline-like structures, similar in color to iron oxyhydroxides, suggests that E. mutabilis may be sequestering iron, and possibly other metals. Further work is needed to determine if E. mutabilis contributes to natural mitigation of poor water quality at these and other coal mine sites.
Received: 13 January 2000 · Accepted: 2 May 2000 相似文献
883.
The Salí River hydrogeological basin is one of the most productive artesian basins in Argentina. It is located in the southeastern
part of the province of Tucumán, northwestern Argentina, and its groundwater resources are developed for water supply and
irrigation. The chemical composition of the water is strongly influenced by the interaction with the basinal sediments and
by hydrologic characteristics such as the flow pattern and time of residence.
Three hydrochemical zones are defined in the study area and the processes that control the chemical composition of the water
are manifestly different in each zone. The dissolution of halite, sodium sulphate, and gypsum explains part of the contained
Na+, K+, Cl–, SO4
2–, and Ca2+, but other processes, such as cation exchange, calcite precipitation, weathering of aluminosilicates, and gas exchange with
the atmosphere, also contribute to the water composition.
The assessment of contamination indicators, such as pH, dissolved organic matter, dissolved oxygen, phosphate, and nitrate,
indicates that the groundwater is suitable for human consumption. However, biological contamination has been detected in samples
from some wells, especially those near the Salí River.
Electronic Publication 相似文献
884.
Abstract: 3–D velocity images of the crust beneath the northern margin of the North China Plate have been constructed using P-wave travel time residuals of the latest earthquakes, with the data supplied by Chinese seismic networks.
The seismic image results indicate that there is a lateral heterogeneity in the crust beneath the northern part of the North China block. The velocity images of the upper crust show features closely related to the tectonic features on the surface. It can be seen from these velocity images of the vertical sections, and from the horizontal slice images at depths of 11 and 16 km that there exist East-West and North-East structures. The images indicate that the juncture zone of basin–and–range terrain is between the blue-colored high–velocity block corresponding to the Yanshan mountain range that developed during the Yanshan period in northwest Beijing and the green low-velocity area corresponding to the North China basin in southeast Beijing (Fig. 5). The juncture zone between high-velocity and low–velocity, and EW and NE fault zones have significant ore-control effects. From the chart of epicenters in the northern region of North China, we find that the epicenters of earthquakes are almost entirely distributed within the NE strip. Almost all major earthquakes took place in the transition strip between the high and low-velocity zones in the crust. The distribution of epicenters also reflects the strikes of known NE–faults. From the image sections along the latitude, we find that in the area between 114.0 E –118.0 E , there is a blue high-velocity block standing upright from the Moho to the upper crust (Fig. 6), from which can be deduced that some materials such as magma moved upward from the upper mantle during the history of its geological development. 相似文献
The seismic image results indicate that there is a lateral heterogeneity in the crust beneath the northern part of the North China block. The velocity images of the upper crust show features closely related to the tectonic features on the surface. It can be seen from these velocity images of the vertical sections, and from the horizontal slice images at depths of 11 and 16 km that there exist East-West and North-East structures. The images indicate that the juncture zone of basin–and–range terrain is between the blue-colored high–velocity block corresponding to the Yanshan mountain range that developed during the Yanshan period in northwest Beijing and the green low-velocity area corresponding to the North China basin in southeast Beijing (Fig. 5). The juncture zone between high-velocity and low–velocity, and EW and NE fault zones have significant ore-control effects. From the chart of epicenters in the northern region of North China, we find that the epicenters of earthquakes are almost entirely distributed within the NE strip. Almost all major earthquakes took place in the transition strip between the high and low-velocity zones in the crust. The distribution of epicenters also reflects the strikes of known NE–faults. From the image sections along the latitude, we find that in the area between 114.0 E –118.0 E , there is a blue high-velocity block standing upright from the Moho to the upper crust (Fig. 6), from which can be deduced that some materials such as magma moved upward from the upper mantle during the history of its geological development. 相似文献
885.
Agricultural practices, hydrology, and water quality of the 267-km2 Big Spring groundwater drainage basin in Clayton County, Iowa, have been monitored since 1981. Land use is agricultural; nitrate-nitrogen
(-N) and herbicides are the resulting contaminants in groundwater and surface water. Ordovician Galena Group carbonate rocks
comprise the main aquifer in the basin. Recharge to this karstic aquifer is by infiltration, augmented by sinkhole-captured
runoff. Groundwater is discharged at Big Spring, where quantity and quality of the discharge are monitored.
Monitoring has shown a threefold increase in groundwater nitrate-N concentrations from the 1960s to the early 1980s. The nitrate-N
discharged from the basin typically is equivalent to over one-third of the nitrogen fertilizer applied, with larger losses
during wetter years. Atrazine is present in groundwater all year; however, contaminant concentrations in the groundwater respond
directly to recharge events, and unique chemical signatures of infiltration versus runoff recharge are detectable in the discharge
from Big Spring.
Education and demonstration efforts have reduced nitrogen fertilizer application rates by one-third since 1981. Relating declines
in nitrate and pesticide concentrations to inputs of nitrogen fertilizer and pesticides at Big Spring is problematic. Annual
recharge has varied five-fold during monitoring, overshadowing any water-quality improvements resulting from incrementally
decreased inputs.
Electronic Publication 相似文献
886.
Impacts of afforestation on groundwater resources and quality 总被引:4,自引:0,他引:4
Plans to double the proportion of land under forest cover in Ireland by the year 2035 have been initiated. The plan, primarily
financially driven, ignores potential environmental impacts of forestry, particularly impacts on groundwater resources and
quality. Since groundwater supplies almost 25% of Ireland's total potable water, these impacts are important. Field investigations
indicate that afforestation leads to a reduction in runoff by as much as 20%, mainly due to interception of rainfall by forest
canopies. Clearfelling has the opposite impact. Implications are that uncoordinated forestry practices can potentially exacerbate
flooding. Groundwater recharge is affected by forestry, largely due to greater uptake of soil water by trees and to increased
water-holding capacity of forest soils, arising from higher organic contents. Recharge rates under forests can be reduced
to one tenth that under grass or heathland. Groundwater quality may be affected by enhanced acidification and nitrification
under forests, due partly to scavenging of atmospheric pollutants by forest canopies, and partly to greater deposition of
highly acid leaf litter. The slower recharge rates of groundwater under forests lead to significant delays in manifestation
of deterioration in groundwater quality.
Electronic Publication 相似文献
887.
Brenda S. Pierce Artur Martirosyan Gourgen Malkhasian Samvel Harutunian Grigory Harutunian 《International Journal of Coal Geology》2001,45(4):307
The Antaramut–Kurtan–Dzoragukh (AKD) coal deposit is a previously unrecognized coal field in north-central Armenia. Coal has been known to exist in the general vicinity since the turn of the century, but coal was thought to be restricted to a small (1 km2) area only near the village of Antaramut. However, through detailed field work and exploratory drilling, this coal deposit has been expanded to at least 20 km2, and thus renamed the Antaramut–Kurtan–Dzoragukh coal field, for the three villages that the coal field encompasses. The entire coal-bearing horizon, a series of tuffaceous sandstones, siltstones, and claystones, is approximately 50 m thick. The AKD coal field contains two coal beds, each greater than 1 m thick, and numerous small rider beds, with a total resource of approximately 31,000,000 metric tonnes. The coals are late Eocene in age, high volatile bituminous in rank, relatively high in ash yield (approximately 40%, as-determined basis) and moderate in sulfur content (approximately 3%, as-determined basis). The two coal beds (No. 1 and No. 2), on a moist, mineral-matter-free basis, have high calorific values of 32.6 MJ/kg (7796 cal/g) and 36.0 MJ/kg (8599 cal/g), respectively. Coal is one of the few indigenous fossil fuel resources occurring in Armenia and thus, the AKD coal field could potentially provide fuel for heating and possibly energy generation in the Armenian energy budget. 相似文献
888.
GPS工程控制网的若干特殊问题 总被引:9,自引:1,他引:9
根据GPS定位技术的优点,讨论了建立GPS工程控制网在踏勘、设计、观测及数据处理方面的若干特殊问题,并提出高精度工程控制网GPS数据处理方案。 相似文献
889.
890.
对“3S”集成技术的一些认识 总被引:3,自引:0,他引:3
本文从遥感,地理信息系统和全球定位系统的产生与发展过程,论述了它们走向集成化的必然趋势,说明了“3S”信息集成技术的涵意;介绍了它的应用领域,最后提出了作者对发展我国以“3S”集成技术为支撑的地理信息产业应采取的对策的建议。 相似文献