Results 171 to 180 of about 24,017 (211)
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Stable isotope studies of soil nitrogen
2020Sound generalisations and predictions of soil processes are difficult to make with confidence because of the chemical, physical and biological variations that occur in soil at all scales in both space and time. Natural abundance studies have been used in a wide range of soil-nitrogen (N) investigations and have provided some insights to the complexity ...
D.W. Hopkins, R.E. Wheatley, D. Robinson
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Journal of Forensic Sciences, 2008
Abstract: There remains significant uncertainty in illicit marijuana cultivation. We analyzed the δ13C and δ15N of 508 domestic samples from known U.S.A. counties, 31 seized from a single location, 5 samples grown in Mexico and Colombia, and 10 northwest border seizures. For a subset, inflorescences and leaves were analyzed separately.
Jason B, West +2 more
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Abstract: There remains significant uncertainty in illicit marijuana cultivation. We analyzed the δ13C and δ15N of 508 domestic samples from known U.S.A. counties, 31 seized from a single location, 5 samples grown in Mexico and Colombia, and 10 northwest border seizures. For a subset, inflorescences and leaves were analyzed separately.
Jason B, West +2 more
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Stable nitrogen isotope composition of NOx of biomass burning in China
Science of The Total Environment, 2022Owing to the local characteristics of stable nitrogen isotopes in nitrogen oxides (δ15N-NOx) emitted from biomass burning, the lack of data on δ15N-NOx values associated with biomass burning in China limits the use of this parameter in identifying and quantifying the sources of atmospheric nitrate (NO3-) and NOx.
Yasheng, Shi +5 more
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Forest cover controls the nitrogen and carbon stable isotopes of rivers
Science of The Total Environment, 2022Deforestation affects the ecological integrity of rivers and streams, threatening biodiversity and ecosystem services worldwide. However, few studies have strictly analyzed the effect of the functional responses of tropical streams to changes in forest cover since deforested basins are usually also influenced by confounding anthropogenic inputs.
Fausto, Machado-Silva +3 more
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Stable Nitrogen Isotope Analysis by Optical Spectroscopy
Analytical Chemistry, 1958Optical spectroscopy with photo-electric detection provides a rapid and precise micromethod for determining the nitrogen isotopic concentration of nitrogen gas and of nitric oxide gas. This paper describes the effect of operating conditions on the precision and the accuracy of such measurements.
H. P. Broida, M. W. Chapman
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STABLE NITROGEN AND SULFUR ISOTOPES IN ATMOSPHERIC CHEMISTRY
2021SO2 and NOx (NO+NO2) are important trace gases in the atmosphere as they adversely affect air quality and are precursors to sulfate and nitrate aerosols in the atmosphere. However, there are significant uncertainties in the emission inventories and the atmospheric chemistry processes of both gases.
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Journal of Phycology, 2014
In our research, we collected and analyzed numerous macroalgal specimens (738) for isotopic analysis sampled over a year at monthly intervals across 20 sites within the Urías lagoon complex, a typical subtropical coastal ecosystem located in the Gulf of California.
María Julia, Ochoa-Izaguirre +1 more
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In our research, we collected and analyzed numerous macroalgal specimens (738) for isotopic analysis sampled over a year at monthly intervals across 20 sites within the Urías lagoon complex, a typical subtropical coastal ecosystem located in the Gulf of California.
María Julia, Ochoa-Izaguirre +1 more
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Stable isotopes of carbon and nitrogen in soil ecological studies
Biology Bulletin, 2007The development of stable isotope techniques is one of the main methodological advances in ecology of the last decades of the 20th century. Many biogeochemical processes are accompanied by changes in the ratio between stable isotopes of carbon and nitrogen (12C/13C and 14N/15N), which allows different ecosystem components and different ecosystems to be
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Primary Consumer Stable Nitrogen Isotopes as Indicators of Nutrient Source
Environmental Science & Technology, 2005Non-point source loading of nitrogen and phosphorus is a primary cause of eutrophication of inland waters, although the diffuse and variable nature of nutrient inputs makes it difficult to trace and identify nutrient pathways. Stable nitrogen isotope values (delta15N) in aquatic biota are thought to reflect anthropogenic nutrient inputs, and they may ...
Zanden, M. J. Vander +3 more
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Effects of Preservation Method on Stable Carbon and Nitrogen Isotope Values
Physiological and Biochemical Zoology, 2008Some methods of tissue preservation have significant effects on values of stable isotopes of carbon (delta(13)C) and nitrogen (delta(15)N), but studies on this topic are scattered in the literature. The goals of this study were to (1) summarize the results from studies of preservation effects in the literature and (2) test the effects of four common ...
Lindy M, Barrow +2 more
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