Assessing the sources and magnitude of diurnal nitrate variability in the San Joaquin River (California) with an in situ optical nitrate sensor and dual nitrate isotopes - Pellerin, Brian; Downing, Bryan; Kendall, Carol; Dahlgren, Randy A.; Kraus, Tamara; Saraceno, John Franco; Spencer, Robert G. M.; Bergamaschi, Brian A. (Freshwater Biology, 2009)