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A Triassic carbonate unit has been intensively drained by zinc and lead ore mines and numerous borehole fields since the nineteenth
century. Its groundwater recharge has increased due to: pumping of water from boreholes, mining activity, and urbanization.
An approach to determine the amounts of the recharge at a variety of spatial scales is presented in the paper. Different methods
were used to identify and quantify recharge components on a regional and local scale: mathematical modelling was performed
for four aquifers included in an aquifer system, an analytical estimation based on the assumption that an average recharge
is equal to the average discharge of the hydrogeological system—for six man-made drainage centres, and the method of water
level fluctuation (WLF) was applied in one observation borehole. Results of modelling have been supplemented by observation
of environmental tracers (δ18O, δ2H, 3H), noble gases temperatures, and 4Heexc in groundwater. The regional aquifer’s current recharge according to estimations performed by means of modelling varies from
39 to 101 mm/year on average. Depending on the aquifer site the average precipitation ranges from 779 to 864 mm/year. In the
confined part of the aquifer average recharge ranges from 26 to 61 mm/year. Within outcrops average recharge varies from 96
to 370 mm/year. Current recharge estimated by the analytical method for man-made drainage centres varies from 158 up to 440 mm/year.
High values are caused by different recharge sources like precipitation, induced leakage from shallow aquifers, and water
losses from streams, water mains and sewer systems. Pumping of water, mining and municipal activities constitute additional
factors accounting for the intensified recharge. 相似文献
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F. W. Witkowski D. J. Blundell P. Gutteridge A. D. Horbury N. H. Oxtoby H. Qing 《Marine and Petroleum Geology》2000,17(10)
Diagenetic studies of sedimentary rocks using cold cathodoluminescence (CL) microscopy have been severely limited because of the very low intensity of visible luminescent emissions, which required long photographic exposure times, and because of the difficulty in obtaining quantitative data from CL observations. The solution to this problem is to fit the microscope with a high-sensitivity digital colour video camera linked to a computer with image enhancement and image analysis software. The new technique described in this paper:
- • produces digital CL images of consistent high quality, both quickly and cheaply;
- • controls the capture and editing of CL images, to reveal detailed textural information even from minerals exhibiting low level luminescence such as quartz;
- • acquires quantitative information on pore systems and the abundance of cement zones from CL images.
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The Fuelwood Crisis in Southern Africa — Relating Fuelwood Use to Livelihoods in a Rural Village 总被引:2,自引:0,他引:2
The aim of the paper is to examine wood as a source of fuel energy in rural South Africa and factors influencing its usage.
The analysis is based on household profiles and characteristics (e.g., gender, caste, population and income) in a livelihood
framework. Fuelwood consumption was estimated to be 692 kg/capita, and 4343 kg/user household per annum, valued at $311 per
household. Consumption was modelled in relation to informal and formal cash incomes, and population of children, female and
male adults. However, only the population of female adults could significantly influence consumption of fuelwood. This implied
that where there were more women in a household, consumption was likely to be high. This might be due to the majority of women
doing the cooking and heating in the household. Any change in the value of cash income of households had no significant impacts
on fuelwood consumed. Cash incomes might therefore not be strong determinants of the types of energy used by rural households.
The average quantity of wood consumed for fuel energy in summer was not significantly different from consumption in winter.
Some households perpetually used more wood than others. The study further showed that harvesting of wood for fuel energy is
not opportunistic, but requires reallocation of time for other livelihood activities in times of shortage. The fuelwood crisis
is not simple and not only about shortage of fuelwood and/or population growth but linked to household profiles and other
livelihood strategies and subsequently vulnerability of households. These would require thorough investigation and understanding
in relation to precise demand and supply data for fuelwood before the fuelwood problem can be sufficiently managed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Water requirements for germination and early seedling establishment in four African savanna woody plant species 总被引:1,自引:0,他引:1
The aim of this study was to determine the water requirements for germination and early seedling establishment of four African savanna tree species, namelyAcacia karroo, A. nilotica, A. tortilisandMundulea sericea. The acacias are characteristic of nutrient-rich, andM. sericeaof nutrient-poor savannas. Imbibition times of scarified seeds ofA. karroo(4 h),M. sericea(6 h) andA. tortilis(8 h) were rapid relative toA. nilotica(28 h) and were inversely correlated with seed size. Imbibed water is lost in about 2 h after drying at 25°C for all species exceptA. nilotica(only 70% moisture loss). Seeds ofA. karrooandM. sericeakept at 40°C dried to below their original moisture contents within 2 h. Seeds ofA. niloticaandA. tortilisdried at 40°C lost viability relative to (undried) control seeds, while there was no significant loss of viability forA. karrooandM. sericea. For fully imbibed seeds to germinate in sandy savanna soils, all four species required at least the equivalent of 3 mm rainfall every 2 days under mild greenhouse conditions. However, most ungerminated seeds were still viable despite drying-out from a fully imbibed state. Maintenance of soil at 50% field capacity (FC), or watering to FC every 9th day is the maintenance requirements for 2-week-old seedlings ofA. niloticaandM. sericeato continue growth for a further 5 weeks under greenhouse conditions, althoughA. niloticamostly survived 25% FC with one seedling surviving 12·5% FC. Root penetration was rapid in sandy soils, withA. niloticaandM. sericeaattaining a depth of 40 cm within 15 days. Frequent, but not necessarily high, rainfall appears to be essential for germination and seedling survival over the first 7 weeks. 相似文献
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Darss Sill as a biological border in the fossil record of the Baltic Sea: evidence from diatoms 总被引:1,自引:0,他引:1
Andrzej Witkowski Anja Broszinski Ole Bennike Beata Janczak-Kostecka Jrn Bo Jensen Wolfram Lemke Rudi Endler Antoon Kuijpers 《Quaternary International》2005,130(1):97
Biostratigraphical and palaeoecological analyses of cores along a transect from Femer Belt to the Arkona Basin reveal that North Sea waters began to enter the western Baltic Sea between 8600 and 8400 calibrated years BP. Studies of diatoms indicate that Mecklenburg Bay was characterised by slightly brackish-water conditions between 8400 and 8000 cal. years BP. At around 8000 cal. years BP increasing salinity is indicated by a strong dominance of the diatoms Paralia sulcata and Dimeregramma minor. Some centuries later another diatom assemblage appeared and became dominant in Mecklenburg Bay. This assemblage includes Hyalinella lateripunctata and Pravifusus hyalinus species typical of shallow water areas along the Atlantic coast today. At this time the first marine molluscs made their appearance. The oldest shell of a marine mollusc found in our material is dated to 7600 cal. years BP. The associated assemblage that includes adult specimens of the gastropod Aporrhais pespelicani indicates higher salinities than today.During the Littorina Sea stage a marine diatom flora with P. sulcata, Catenula adhaerens and D. minor crossed the Darss Sill and became widely distributed in the Arkona Basin, Pomeranian Bay and the Baltic Sea proper. In contrast, taxa indicative of the Hyalinella lateripunctata/P. hyalinus assemblage are only found west of the Darss Sill in Femer Belt and Mecklenburg Bay. Apparently, the Darss Sill threshold has been acting as an important salinity border from around 7800 cal. years BP until today. 相似文献