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The effects of timber harvesting on stream water quality and efficiency of alternate streamside management zones were evaluated
in Pockwock Lake and Five Mile Lake watersheds in central Nova Scotia, Canada. The streamside management zone (SMZ) included
a 20 m no cut, 20 m select cut and a 30 m select cut buffer strips along the stream. Water quality of eight streams, six in
harvested and two in not-harvested watersheds were monitored for two years before and two years after the harvesting of timber.
Nonparametric statistical tests on stream water quality showed that there was significant change in the concentration of potassium
in six streams, manganese in five streams, zinc in two streams and total nitrogen in one stream after timber harvesting. There
was no significant change in the quality of water in two streams used as control sites in the neighboring watersheds of similar
size and hydrological characteristics. The results show that forest management practices were most favorable in streams maintained
with 30 m select cut followed by 20 m no cut and 20 m select cut SMZ. The streamside zone width and treatment of select cut
or no cut in the zone played an important role in filtering or retaining the minerals in surface water runoff. In buffer zones
of similar width, the buffer zone with no cut or forested buffer was relatively more effective at protecting stream water
quality than select cut SMZ. The vegetation in the zone may have decreased the flow velocity and increased residence time
and thus increased filtration and retention of minerals in the riparian soil. 相似文献
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Nkambule TI Kuvarega AT Krause RW Haarhoff J Mamba BB 《Environmental science and pollution research international》2012,19(9):4120-4132
Introduction
The removal of natural organic matter (NOM) from water is becoming increasingly important in order to prevent the formation of carcinogenic disinfection by-products. The inadequate removal of NOM has a bearing on the capacity of the other treatment processes to remove organic micro-pollutants or inorganic species that may be present in the water. New methods are therefore currently being sought to effectively characterise NOM and also to ensure that it is sufficiently removed from drinking water sources.Methodology
Nitrogen- and palladium-co-doped TiO2 was synthesised by a modified sol?Cgel method and evaluated for its photocatalytic degradation activity on NOM fractions under simulated solar radiation. The photocatalyst was characterised by FT-IR, Raman, XRD, DRUV?Cvis, SEM, TEM, EDS, XPS and TGA. FT-IR confirmed the presence of OH groups on thermally stable, nearly spherical anatase nanoparticles with an average diameter of 20?nm. PdO species appeared on the surface of the TiO2 as small uniformly dispersed particles (2 to 3?nm). A red shift in the absorption edge compared to commercial anatase TiO2 was confirmed by DRUV?Cvis. In order to gain a better insight into the response of NOM to photodegradation, the NOM was divided into three different fractions based on its chemical nature.Results and discussion
Photodegradation efficiencies of 96, 38 and 15?% were realised for the hydrophobic, hydrophilic and transphilic NOM fractions, respectively. A reasonable mechanism was proposed to explain the photocatalytic degradation of the NOM fractions. The high photocatalytic activity could be attributed to the larger surface area, smaller crystalline size and synergistic effects of the co-dopants N and Pd in the TiO2 crystal. 相似文献3.
An assessment of levels of endosulfan and endosulfan sulphate in rats collected from a plot sprayed with endosulfan was carried
out for a period of four months. The analysis was carried out in the livers, muscles and fatty tissues of the rats using Gas
Chromatography. Samples were ground with sodium sulphate and aluminium oxide and the analyte soxhlet extracted with hexane.
The extract was then cleaned by florisil column chromatography. Levels of endosulfan in rats were found to range in livers
from 0.356 to 5.807 ppb, in muscles from 0.089 to 5.167 ppb and in fatty tissues from 0.083 to 4.785 ppb. Levels of endosulfan
sulphate correlated well with those of endosulfan and ranged in livers from 0.00 to 3.96 ppb, in muscles from 0.00 to 3.37 ppb
and in fatty tissue from 0.00 to 2.93 ppb. In the control rats samples, collected from an unsprayed area in the city of Harare
(University of Zimbabwe), no endosulfan could be detected. 相似文献
4.
Ratshiedana Rudzani Kuvarega Alex Tawanda Mishra Ajay Kumar 《Environmental science and pollution research international》2021,28(9):10357-10374
Environmental Science and Pollution Research - The paper reviews graphitic carbon nitride–based nanostructured photocatalytic materials and nanofibres for applications in water purification.... 相似文献
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