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In alluvial plains, intensive farming with conspicuous use of agrochemicals, can cause land pollution and groundwater contamination.
In central Po River plain, paleo-channels are important links between arable lands and the underlaying aquifer, since the
latter is often confined by clay sediments that act as a barrier against contaminants migration. Therefore, paleo-channels
are recharge zones of particular interest that have to be protected from pollution as they are commonly used for water supply.
This paper focuses on fertilizer mobilization next to a sand pit excavated in a paleo-channel near Ferrara (Italy). The problem
is approached via batch test leaking and columns elution of alluvial sediments. Results from batch experiments showed fast
increase in all major cations and anions, suggesting equilibrium control of dissolution reactions, limited availability of
solid phases and geochemical homogeneity of samples. In column experiments, early elution and tailing of all ions breakthrough
was recorded due to preferential flow paths. For sediments investigated in this study, dispersion, dilution and chemical reactions
can reduce fertilizers at concentration below drinking standards in a reasonable time frame, provided fertilizer loading is
halted or, at least, reduced. Thus, the definition of a corridor along paleo-channels is recommended to preserve groundwater
quality. 相似文献
2.
Nakka vagu, a tributary of the River Manjira in the Medak district of Andhra Pradesh, has a catchment area of ∼500 km2. Patancheru is an industrial development area (IDA) near the vagu. There are about 350 industries of varied nature (pulp,
plastic, bulk drugs, pharmaceuticals, paints and steel rolling mills) that are engaged in the manufacture/processing of their
respective products and that use water extensively. The hydrogeological setup has a bearing on the widespread contamination
in the area because of discharge of industrial effluents into open land and streams. Several dug wells and boreholes situated
in the study area have been monitored for water level fluctuations and quality variations. Pumping tests have been conducted
to evaluate aquifer parameters. The geology, drainage, chemistry and other related anthropogenic factors play a major role
in the spread of pollution in the area. Hence, it is very important to determine the degree of vulnerability to pollution
based on hydrogeological factors. Amidst the granite terrain, the Nakka vagu has been identified as a paleo-channel (composed
of clay–silt–sand facies); its presence in the area has immensely increased the spread of groundwater contamination. The transmissivity
of the alluvial aquifer varies from 750 to 1315 m2/day. The adjoining granite has a transmissivity that varies from 30–430 m2/day. The thickness of the valley fill in the discharge region is about 10–12 m, with a lateral spread of 500–700 m, east
of Nakka vagu.
Received: 17 November 1999 · Accepted: 14 March 2000 相似文献
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