نتایج جستجو برای: anthropogenic source
تعداد نتایج: 440868 فیلتر نتایج به سال:
An advantage of using chlorofluorocarbons (CFCs) and sulfur hexafluoride (SF6) as tracers of ocean circulation is that the time-dependent source functions permit calculation of rates for ocean processes. These compounds are also sensitive indicators highlighting interior ocean regions where surface-derived anomalies can be transported on timescales of decades. Significant applications for CFCs ...
Genes encoding resistance to antibiotics appear, like the antibiotics themselves, to be ancient, originating long before the rise of the era of anthropogenic antibiotics. However, detailed understanding of the specific biological advantages of antibiotic resistance in natural environments is still lacking, thus limiting our efforts to prevent environmental influx of resistance genes. Here, we p...
Humans have more than doubled the amount of reactive nitrogen (Nr) added to the biosphere, yet most of what is known about its accumulation and ecological effects is derived from studies of heavily populated regions. Nitrogen (N) stable isotope ratios ((15)N:(14)N) in dated sediments from 25 remote Northern Hemisphere lakes show a coherent signal of an isotopically distinct source of N to ecosy...
We evaluate the impact of anthropogenic and natural NO(x) sources over the contiguous United States on tropospheric NO(x) and O(3) levels by using a global 3D chemical transport model. The effects of major U.S. surface NO(x) emission sources (including anthropogenic, biomass burning, and soil emissions) are compared with that of lightning-produced NO(x). Summer lightning is shown to play a domi...
Coal combustion is the primary anthropogenic source of atmospheric iodine, which has important environmental and health effects. The iodine distribution in Chinese coals and the atmospheric iodine emission factors of coal-fired boilers are studied to estimate the iodine atmospheric flux from coal combustion in China from 1995 to 2009. The national average iodine content weighted by coal yield f...
arth's climate is greatly influenced by carbon dioxide conE centrations in the atmosphere, which have increased by approximately 25% since the dawning of the Industrial Revolution, when fossi l fuel combustion accelerated greatly (IPCC 1990). Another important anthropogenic source of atmospheric carbon is associated with deforestation, especially in primary forests, which can store large amount...
We report the first measurements of Pb isotopes in Antarctic snow, which show that even recent snow containing 2.3 pg/g is highly polluted with anthropogenic Pb. This follows from a comparison of isotope abundances of Pb in surface snow and terrestrial dust extracted from ancient Antarctic ice (Dome C, depth 308 m, approximate age 7,500 a BP), the latter being distinctly more radiogenic. This r...
At the “Pašino vrelo” source, groundwater is exploited by means of wells which tap a carbonate aquifer of Badenian age. The natural quality of groundwater complies with the provisions of the Regulation on health and safety of drinking water. However, anthropogenic impacts in the form of microbiological pollution have been observed. Extensive hydrogeological investigations have been conducted in...
Dust is one of the environmental problems in Kerman city. Due to the major aspect of mineralogy in environmental studies, mineralogy and chemical studies of dust in different regions of the city performed by microscopic thin sections, x ray diffraction (XRD) and ICP-MS. In all areas of the city, minerals such as calcite, quartz, feldspar, pyroxene, micas, Jaffeite, gismondine and clay mineral w...
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