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Modeling Influence of Sediment Heterogeneity on Nutrient Cycling in Streambeds
Author(s) -
Pescimoro Eugenio,
Boano Fulvio,
Sawyer Audrey H.,
Soltanian Mohamad Reza
Publication year - 2019
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2018wr024221
Subject(s) - hyporheic zone , biogeochemical cycle , silt , environmental science , nutrient , hydrology (agriculture) , sediment , nitrate , total organic carbon , nutrient cycle , environmental chemistry , soil science , ecology , geology , environmental engineering , chemistry , surface water , geomorphology , geotechnical engineering , biology
Abstract Rivers and their hyporheic zones play an important role in nutrient cycling. The fate of dissolved inorganic nitrogen is governed by reactions that occur in the water column and streambed sediments. Sediments are heterogeneous both in term of physical (e.g., hydraulic conductivity) and chemical (e.g., organic carbon content) properties, which influence water residence times and biogeochemical reactions. Yet few modeling studies have explored the effects of both physical and chemical heterogeneity on nutrient transport in the hyporheic zone. In this study, we simulated hyporheic exchange in physically and chemically heterogeneous sediments with binary distributions of sand and silt in a low‐gradient meandering river. We analyzed the impact of different silt/sand patterns on dissolved organic carbon, oxygen, nitrate, and ammonium. Our results show that streambeds with a higher volume proportion of silt exhibit lower hyporheic exchange rates but more efficient nitrate removal along flow paths compared to predominantly sandy streambeds. The implication is that hyporheic zones with a mixture of inorganic sands and organic silts have a high capacity to remove nitrate, despite their moderate permeabilities.