Dynamics of added nitrate and phosphate compared in a northern California woodland stream
Injections of NO 3 and PO 4 were made during September 1975 into Little Lost Man Creek, a small pristine stream in Redwood National Park, California. Chloride, a conservative constituent, was added in a known ratio to the nutrients. Nutrient loss at a downstream point was calculated using concentration of added Cl as a reference. Nitrate nitrogen (NO 3 ‐N), added for 4 h, reached 920 μg/1 (above 5 μg/1 background) just below the injection point, but increased only to 405 μg/1 at 310 m downstream. The concentration decrease was attributed to dispersion and to uptake by stream biota. Percent of NO 3 ‐N lost decreased with increasing concentration of NO 3 ‐N. Phosphate phosphorus (PO 4 ‐P) was added a week after the NO 3 ‐N for 3 h, causing a concentration increase of 296 μg/1 (above 13 μg/1 background) just below the injection point, of 161 μg/1 at 90 m downstream, and of 98 μg/1 at 310 m. Percent loss of PO 4 ‐P at downstream sites increased with increasing PO 4 ‐P concentration and also for a short period after peak concentration occurred, but then decreased as PO 4 ‐P concentration continued decreasing. Differences in stream response to added NO 3 ‐N and PO 4 ‐P are attributed to differing rates of reaction with biota and differing degrees of interaction with abiotic stream solids.