Denitrification is a process that reduces nitrogen levels in headwaters and other streams. We compared nirS and nirK abundances with the absolute rate of denitrification, the longitudinal coefficient of denitrification (i.e., Kden, which represents optimal denitrification rates at given environmental conditions), and water quality in seven prairie streams to determine if nir-gene abundances exp...

We show the dependence of the Bayesian and the N2-derived oxygen abundances on the N-enrichment history of the star-forming galaxies. We select 531 metal-poor and ∼20,000 metal-rich galaxies from the SDSS database for this study. Their “accurate” O/H abundances are obtained from Te and P method, respectively. The discrepancies of the Bayesian and N2-derived abundances from these two “accurate” ...

A broad array of interstellar absorption features that appear in the ultraviolet spectra of bright sources allows us to measure the abundances and ionization states of many important heavy elements that exist as free atoms in the interstellar medium. By comparing these abundances with reference values in the Sun, we find that some elements have abundances relative to hydrogen that are approxima...

We report results from the third in a series of nebular abundance studies of emission-line galaxies from the KPNO International Spectroscopic Survey (KISS). Galaxies with coarse metallicity estimates of 12 + log(O/H) less than 8.2 dex were selected for observation. Spectra of 14 galaxies, which cover the full optical region from [OII]λλ3727,3729 to beyond [SII]λλ6717,6731, are presented, and ab...

Recent developments in the study of abundances of light elements and their relevance to cosmological nucleosynthesis are briefly reviewed. The simplest model, based on standard cosmology and particle physics and assuming homogeneous baryon density at the relevant times, continues to stand up well.

We have computed a set of multiphase chemical evolution models in which the radial mass distribution of each theoretical galaxy is calculated using the universal rotation curve from Persic, Salucci & Steel (1996). We obtain the chemical evolution for galaxies of different masses and morphological types by changing the efficiencies to form molecular clouds and stars according with these types. W...