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Low Transient Storage and Uptake Efficiencies in Seven Agricultural Streams: Implications for Nutrient Demand
Author(s) -
Sheibley Richard W.,
Duff John H.,
Tesoriero Anthony J.
Publication year - 2014
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2014.01.0034
Subject(s) - nutrient , streams , environmental science , residence time (fluid dynamics) , ammonium , hydrology (agriculture) , groundwater , nitrate , chemistry , environmental chemistry , environmental engineering , computer network , geotechnical engineering , organic chemistry , computer science , engineering
We used mass load budgets, transient storage modeling, and nutrient spiraling metrics to characterize nitrate (NO 3 − ), ammonium (NH 4 + ), and inorganic phosphorus (SRP) demand in seven agricultural streams across the United States and to identify in‐stream services that may control these conditions. Retention of one or all nutrients was observed in all but one stream, but demand for all nutrients was low relative to the mass in transport. Transient storage metrics ( A s / A , F med 200 , T str , and q s ) correlated with NO 3 − retention but not NH 4 + or SRP retention, suggesting in‐stream services associated with transient storage and stream water residence time could influence reach‐scale NO 3 − demand. However, because the fraction of median reach‐scale travel time due to transient storage ( F med 200 ) was ≤1.2% across the sites, only a relatively small demand for NO 3 − could be generated by transient storage. In contrast, net uptake of nutrients from the water column calculated from nutrient spiraling metrics were not significant at any site because uptake lengths calculated from background nutrient concentrations were statistically insignificant and therefore much longer than the study reaches. These results suggest that low transient storage coupled with high surface water NO 3 − inputs have resulted in uptake efficiencies that are not sufficient to offset groundwater inputs of N. Nutrient retention has been linked to physical and hydrogeologic elements that drive flow through transient storage areas where residence time and biotic contact are maximized; however, our findings indicate that similar mechanisms are unable to generate a significant nutrient demand in these streams relative to the loads.