Nitrogen concentrations in a small Mediterranean stream: 1. Nitrate 2. Ammonium

Abstract

The importance of storm frequency as well as the groundwater and hyporheic inputs on nitrate (NO 3 -N) and ammonium (NH 4 -N) levels in stream water were studied in a small perennial Mediterranean catchment, Riera Major, in northeast Spain. NO 3 -N concentrations ranged from 0.15 to 1.9 mg l -1 . Discharge explained 47% of the annual NO 3 -N concentration variance, but this percentage increased to 97% when single floods were analysed. The rate of change in nitrate concentration with respect to flow, ∆NO 3 -N/∆Q, ranged widely from 0 to 20 µg NO 3 -N s l -2 . The In contrast, NO 3 -N concentration in hyporheic water was identical to that in stream water. The role of the hyporheic zone as source or sink for ammonium was studied hyporheic was studied comparing its concentrations in stream and hyporheic zone before and after a major storm occurred in October 1994 that removed particulate organic matter stored in sediments. Results showed high ammonium concentrations (75±28 s.d. µg NH 4 -N l -1 ) before the storm flow in the hyporheic zone. After the storm, the ammonium concentration in the hyporheic dropped by 80% (13.6±8 µg NH 4 -N l -1 ) and approached to the level found in stream water (11±8 µg NH 4 -N l -1 ) indicating that indisturbed hyporheic sediments act as a source for ammonium. After the storm, the ammonium concentrations in the stream, hyporheic and groundwater zones were very similar suggesting that stream ammonium concentrations are sustained mainly by input from groundwater. The present study provides evidence that storm flow magnitude is an important source of variability of nitrate concentration and fluxes in Mediterranean streams subjected to an irregular precipitation regime with prolonged dry periods.

Seasonal and Annual Fluxes of Inorganic Constituents in a Small Catchment of a Japanese Cedar Forest near the Sea of Japan

“…The counterclockwise hysteresis in NO À 3 concentrations during heavy rainfall (Fig. 6-b) suggests the contribution of groundwater to the NO À 3 concentration in streams (Butturini and Sabater 2002). Thus, heavy rainfall events cannot be ignored in studies of NO À 3 fluxes.…”

Spatial variability in dissolved organic matter and inorganic nitrogen concentrations in a semiarid stream, San Pedro River, Arizona

“…Nutrient and solute concentrations in stream ecosystems generally are related to the characteristics of the surrounding watershed [ Aiken and Cotsaris , 1995; Allan and Johnson , 1997; Aryal et al , 2003; Boyer et al , 2000; Findlay et al , 2001; Heiny and Tate , 1997] and changes in land cover and land use often are reflected in stream and river chemistry. Semiarid regions throughout the world are experiencing substantial population growth and consequently urban expansion, which ultimately alters the characteristics of the watershed [ Butturini and Sabater , 2000, 2002; Parks and Baker , 1997; Steiner et al , 2000; Stromberg et al , 1996; Westerhoff and Anning , 2000], but how and if this land use change affects stream biogeochemical cycling remains an open question. The conversion of the natural landscape to agricultural or residential land uses can cause an increase in sedimentation and nutrient, particularly nitrogen, concentrations, especially when combined with the encroachment of nitrogen‐fixing species such as mesquite [ Allan and Johnson , 1997; Findlay et al , 2001].…”

Effects of storm flow samplings on the evaluation of inorganic nitrogen and sulfate budgets in a small forested watershed

“…First, storm flow induces hysteresis in the instantaneous interaction of stream discharge and DIN and SO 4 2 exports, which leads to large errors in estimates of annual DIN and SO 4 2 exports (Takeda, 2001). The hysteresis pattern is caused by the different concentrations between rising and receding limbs of a hydrograph for DIN (Ávila et al, 1992;Evans et al, 1999;Butturini and Sabater, 2002;Zhang et al, 2007) and SO 4 2 (Ávila et al, 1992;Rose, 2003). Second, storm flow sampling is time consuming, which increases the costs related to water sampling and chemical analysis.…”

“…It has also been suggested that concentrations are different between storm 632 M. CHIWA ET AL. and low flow periods for NO 3 (Edwards, 1973;Muraoka and Hirata, 1988;Ávila et al, 1992;Murdoch and Stoddard, 1993;Creed and Band, 1998;Ohrui and Mitchell, 1998;McHale et al, 2000;Butturini and Sabater, 2002;Yusop et al, 2006) and SO 4 2 (Edwards, 1973;Ávila et al, 1992). Therefore, estimates of DIN and SO 4 2 exports that were extrapolated from concentrations during low flow periods and storms would be biased, unless the relationship between discharge and DIN or SO 4 2 concentration in stream water was similar between the low and storm flow periods.…”