Oregon State University

About: Oregon State University is a education organization based out in Corvallis, Oregon, United States. It is known for research contribution in the topics: Population & Gene. The organization has 28192 authors who have published 64044 publications receiving 2634108 citations. The organization is also known as: Oregon Agricultural College & OSU.

Dinitrogen fixation in the world's oceans

Abstract: The surface water of the marine environment has traditionally been viewed as a nitrogen (N) limited habitat, and this has guided the development of conceptual biogeochemical models focusing largely on the reservoir of nitrate as the critical source of N to sustain primary productivity. However, selected groups of Bacteria, including cyanobacteria, and Archaea can utilize dinitrogen (N2) as an alternative N source. In the marine environment, these microorganisms can have profound effects on net community production processes and can impact the coupling of C-N-P cycles as well as the net oceanic sequestration of atmospheric carbon dioxide. As one component of an integrated ‘Nitrogen Transport and Transformations’ project, we have begun to re-assess our understanding of (1) the biotic sources and rates of N2 fixation in the world’s oceans, (2) the major controls on rates of oceanic N2 fixation, (3) the significance of this N2 fixation for the global carbon cycle and (4) the role of human activities in the alteration of oceanic N2 fixation. Preliminary results indicate that rates of N2 fixation, especially in subtropical and tropical open ocean habitats, have a major role in the global marine N budget. Iron (Fe) bioavailability appears to be an important control and is, therefore, critical in extrapolation to global rates of N2 fixation. Anthropogenic perturbations may alter N2 fixation in coastal environments through habitat destruction and eutrophication, and open ocean N2 fixation may be enhanced by warming and increased stratification of the upper water column. Global anthropogenic and climatic changes may also affect N2 fixation rates, for example by altering dust inputs (i.e. Fe) or by expansion of subtropical boundaries. Some recent estimates of global ocean N2 fixation are in the range of 100−200 Tg N (1−2 × 1014 g N) yr −1, but have large uncertainties. These estimates are nearly an order of magnitude greater than historical, pre-1980 estimates, but approach modern estimates of oceanic denitrification.

Sources of fine organic aerosol. 3. road dust, tire debris, and organometallic brake lining dust: roads as sources and sinks

Abstract: Particulate matter emitted to the atmosphere due to motor vehicles arises from several sources in addition to tailpipe exhaust. In this study, the organic constituents present in fine particulate (d_p ≤ 2.0 µm) road dust, brake lining wear particles, and tire tread debris (not size segregated) are analyzed using gas chromatography/mass spectrometry. The objective is to characterize such traffic-related sources on an organic compound basis and to search for molecular markers that will assist the identification of traffic-associated dusts in the urban atmosphere. More than 100 organic compounds are quantified in these samples, including n-alkanes, n-alkanoic acids, n-alkenoic acids, n-alkanals, n-alkanols, benzoic acids, benzaldehydes, polyalkylene glycol ethers, PAH, oxy-PAH, steranes, hopanes, natural resins and other compound classes. Paved road dust acts as a repository for vehicle-related particles, which can then be resuspended by the passing traffic. To evaluate the contributions from major urban sources to the road dust complex, source profiles representing different types of vehicle exhaust, brake dust, tire debris, and vegetative detritus are compared, and their fractional contributions are estimated using several groups of organic tracer compounds. Likewise, the close relationship between airborne fine particulate organic constituents and road dust organic matter is discussed.

Carbon dioxide exchange of Alnus rubra

Abstract: The CO2 exchange response of plants to multiple environmental variables is often difficult to frame for purposes of comparison. In this paper, a nonlinear model relating CO2 exchange to light and temperature is derived from experimental curves determined in other investigations. Parameter values, determined from a least-squares fit of the model to CO2 exchange data, are useful for comparing responses to light and temperature in terms of seasonal phenology, population heterogeneity, or species variation. The model was fitted to CO2 exchange data of a group of 40 Alnus rubra Bong. (red alder) seedlings for steady-state combinations of light and temperature. The average deviation of the data from the model was ±6.7%. This steady-state expression satisfactorily predicted CO2 exchange for dynamic conditions of light and temperature occurring in a diurnal cycle.