|Title||Advancing the food-energy-water nexus: Closing nutrient loops in arid river corridors|
|Publication Type||Journal Article|
|Year of Publication||2016|
|Authors||Mortenson JG, González-Pinzón R, Dahm CN, Wang J, Zeglin LH, Van Horn DJ|
|Journal||Environ Sci Technol|
|Date Published||In Press|
Closing nutrient loops in terrestrial and aquatic ecosystems is integral to achieve resource security in the food-energy-water (FEW) nexus. We performed multiyear (2005−2008), monthly sampling of instream dissolved inorganic nutrient concentrations (NH4−N, NO3−N, soluble reactive phosphorus-SRP) along a ∼ 300-km arid-land river (Rio Grande, NM) and generated nutrient budgets to investigate how the net source/sink behavior of wastewater and irrigated agriculture can be holistically managed to improve water quality and close nutrient loops. Treated wastewater on average contributed over 90% of the instream dissolved inorganic nutrients (101 kg/day NH4−N, 1097 kg/day NO3−N, 656 kg/day SRP). During growing seasons, the irrigation network downstream of wastewater outfalls retained on average 37% of NO3−N and 45% of SRP inputs, with maximum retention exceeding 60% and 80% of NO3−N and SRP inputs, respectively. Accurate quantification of NH4−N retention was hindered by low loading and high variability. Nutrient retention in the irrigation network and instream processes together limited downstream export during growing seasons, with total retention of 33−99% of NO3−N inputs and 45−99% of SRP inputs. From our synoptic analysis, we identify trade-offs associated with wastewater reuse for agriculture within the scope of the FEW nexus and propose strategies for closing nutrient loops in arid-land rivers.