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51.
We used a GIS-based approach to examine the influence of road density and physical watershed features (watershed size, wetland
cover, and bedrock type) on water quality in coastal marshes of Georgian Bay, Ontario. We created a GIS that included landscape
information and water-quality data from a 9-year synoptic survey of 105 coastal marshes covering 28 quaternary watersheds.
Multiple regressions and partial correlations were used to discern confounding effects of human-induced (road density) versus
natural physical watershed determinants of water quality. Road density was the dominant factor influencing many water quality
variables, showing positive correlations with specific conductivity (COND), total suspended solids (TSS), and inorganic suspended
solids (ISS) and a negative correlation with overall Water Quality Index scores. Road density also showed positive correlations
with total nitrate nitrogen (TNN) and total phosphorus (TP). By comparison, larger watershed area was the main factor leading
to elevated TP concentrations. The proportion of the watershed occupied by wetlands explained the largest amount of variation
in TNN concentrations (negative correlation) and was also negatively correlated with COND and positively correlated with TSS
and ISS when we controlled for road density. Bedrock type did not have a significant effect in any of the models. Our findings
suggest that road density is currently the overriding factor governing water quality of coastal marshes in Georgian Bay during
the summer low-flow period. We recommend that natural variation in physical watershed characteristics be considered when developing
water quality standards and management practices for freshwater coastal areas. 相似文献
52.
Maja A. Shishovska Vera P. Trajkovska Marina T. Stefova 《Journal of environmental science and health. Part. B》2013,48(7):694-701
An isocratic High Performance Liquid Chromatographic (HPLC) method was optimized for 3-phenoxybenzyl (1RS)-cis-trans-3-(2,2-dichlorovinyl)-2,2-dimethyl-cyclopropanecarboxylate (permethrin) residues identification and quantification in wine matrix. Analytical reverse phase (RP) C-18 column was used (25 cm × 4 mm i.d., 5 μ m) with mobile phase consisting of acetonitrile and water in ratio 70 %/30 % (v v?1), flow-rate 2.0 mL min?1, UV-detection at 215 nm and controlled oven temperature at 25°C. The peaks of isomers were identified with the retention times as compared to standard cis-/trans- mixture and confirmed with characteristic spectra using photodiode array detector. Under these conditions, permethrin isomers were well separated with resolution 2.8 and no interference with the naturally present wine compounds was observed. The method was validated for linearity, precision, accuracy, limit of detection (LOD) and limit of quantification (LOQ). Linear regression analysis data proved a good linear relationship (correlation coefficients, r2, for cis- and trans-isomer are: 0.9995 and 0.9997, respectively) between response of the detector and concentration of permethrin isomers over a wide concentration range for both isomers (0.55 mg L?1 ?4.40 mg L?1). Experimental data showed mean recoveries between 93.95% and 96.58% with RSD values in range: 0.89% ?3.69%. The effect of ethanol content in the solvent on permethrin isomers peak areas was also studied and 60% v v?1 ethanol was found to be optimal for sample preparation. The method was successfully tested on 20 commercial wine samples from the market in which no permethrin was detected. Thus, it was proved that it is suitable for routine permethrin residues analysis. The proposed method is suitable for routine analysis because of the simple sample preparation, acceptable run-time, low cost and its applicability with conventional instruments. 相似文献
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Filipić Arijana Primc Gregor Zaplotnik Rok Mehle Nataša Gutierrez-Aguirre Ion Ravnikar Maja Mozetič Miran Žel Jana Dobnik David 《Food and environmental virology》2019,11(3):220-228
Food and Environmental Virology - While one of the biggest problems we are facing today is water scarcity, enormous quantities of water are still being used in irrigation. If contaminated, this... 相似文献
55.
The major metabolite of 1-propyl-3,5-diethyl-6-chlorouracil has been identified as 6,8-diethyl-2-methyl-tetrahydrooxazolo[3,2-c]pyrimidine-5,7(4H,6H)-dione. The biotransformation to this bicyclic barbituric acid derivative takes place via substitution of the chlorine by ß- and not by α-hydroxy group of the intermediate hydroxypropane. 相似文献
56.
The major metabolite of 5-ethyl-2′-deoxyuridine in rats has been isolated and purified by preparative thick layer and column chromatography. By mass and 1H NMR spectroscopy, it was identified as 5-(1-hydroxyethyl) uracil; the structure was confirmed by comparison with an authentic sample. 相似文献
57.
Why GIWA? Six years ago several people had their doubts as to whether a Global International Waters Assessment would be worth the money and effort. Nowadays, it is no longer necessary to justify the creation of GIWA. On the contrary, we will show how important it was that the Global Environmental Facility (GEF) and UNEP, constituted GIWA. Countless water-related assessments focus on specific regions and/or specific issues. But GIWA is unique in its global and holistic policy-oriented approach applying a common methodology to address the major problems in all parts of the global hydrosphere. One major achievement of GIWA will be the GIWA publications which provide advice to GEF and other decision-making organizations. Further assets include the network of regional focal points and teams. GIWA encompasses marine, surface freshwater, and groundwater systems, following the flow of water from the sources in the mountains through the rivers and estuaries into the coastal waters and the shelf seas. GIWA studies the physical, chemical and biological properties of those waterbodies and living resources in relation to the human activities, combining ecological and socioeconomic considerations. 相似文献
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