نتایج جستجو برای: carbon and sulfur stable isotopes
تعداد نتایج: 16921217 فیلتر نتایج به سال:
Green coffee bean isotopes have been used to trace the effects of different climatic and geological characteristics associated with the Hawaii islands. Isotope ratio mass spectrometry (IRMS) and inductively coupled plasma mass spectrometry ((MC)-ICP-SFMS and ICP-QMS) were applied to determine the isotopic composition of carbon (δ13C), nitrogen (δ15N), sulfur (δ34S), and oxygen (δ18O), the isoto...
Sediment cores were collected to investigate multiple stresses on Clear Lake, California, USA, through the period of European occupation to the present day. Earlier workers suggested the hypothesis that the use of mechanized earthmoving equipment, starting in the 1920s and 1930s, was responsible for erosion, mercury (Hg) contamination, and habitat loss stresses. Cores (approximately 2.5 m in de...
Conspicuous global stable carbon isotope excursions that are recorded in marine sedimentary rocks of Phanerozoic age and were associated with major extinctions have generally paralleled global stable oxygen isotope excursions. All of these phenomena are therefore likely to share a common origin through global climate change. Exceptional patterns for carbon isotope excursions resulted from massi...
The measurement of isotope ratios in sedimentary rocks deposited over geological time can provide key insights to past environmental change over important intervals in the past. However, it is important to be aware that secondary alteration can overprint the original isotopic records. We demonstrate this principle using high-resolution carbon, sulfur, and oxygen isotope measurements in organic ...
We have known about the processes of methanogenesis and methanotrophy for over 100 years, since the days of Winogradsky, yet their contributions to the carbon cycle were deemed to be of negligible importance for the majority of that period. It is only in the last two decades that methane has been appreciated for its role in the global carbon cycle, and stable isotopes have come to the forefront...
Mountaintop mining (MTM) is the primary procedure for surface coal exploration within the central Appalachian region of the eastern United States, and it is known to contaminate streams in local watersheds. In this study, we measured the chemical and isotopic compositions of water samples from MTM-impacted tributaries and streams in the Mud River watershed in West Virginia. We systematically do...
Cellulose is usually isolated from the other components of plant material for analysis of carbon stable isotope ratios (dC). However, many studies have shown a strong correlation between whole-wood and cellulose dC values, prompting debate about the necessity of cellulose extraction for tree-ring studies. The dC values were measured in whole wood, extractive-free wood, purified cellulose, aceto...
Nitrogen and carbon stable isotope data sets are commonly used to assess complex population ecosystem responses natural or anthropogenic changes at regional global spatial scales, monthly decadal timescales. Measured in the tissues of consumers, nitrogen isotopes (δ15N) primarily estimate trophic position while (δ13C) describe habitat associations feeding pathways. Models both δ15N δ13C values ...
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