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N budgets and aquatic uptake in the Ipswich River basin, northeastern Massachusetts
Author(s) -
Williams Michael,
Hopkinson Charles,
Rastetter Edward,
Vallino Joseph
Publication year - 2004
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 - 10.1029/2004wr003172
Subject(s) - tributary , environmental science , hydrology (agriculture) , wetland , streams , denitrification , drainage basin , surface runoff , structural basin , nutrient , aquatic ecosystem , base flow , macrophyte , nitrate , nitrogen , ecology , geology , geography , biology , chemistry , computer network , paleontology , cartography , geotechnical engineering , organic chemistry , computer science
We calculated N budgets and conducted nutrient uptake experiments to evaluate the fate of N in the aquatic environment of the Ipswich River basin, northeastern Massachusetts. A mass balance indicates that the basin retains about 50% of gross N inputs, mostly in terrestrial components of the landscape, and the loss and retention of total nitrogen (TN) in the aquatic environment was about 9% of stream loading. Uptake lengths of PO 4 and NH 4 were measurable in headwater streams, but NO 3 uptake was below detection (minimum detection limit = 0.05 μM). Retention or loss of NO 3 was observed in a main stem reach bordered by wetland habitat. Nitrate removal in urban headwater tributaries was because of water withdrawals and denitrification during hypoxic events and in ponded wetlands with long water residence times. A mass balance using an entire river network indicates that basin‐wide losses due to aquatic denitrification are considerably lower than estimates from several recent studies and range from 4 to 16% of TDN in stream loading. Withdrawals for domestic use restrict the runoff of headwater catchments from reaching the main stem during low base flow periods, thereby contributing to the spatial and temporal regulation of N export from headwater tributaries.