title: Spatial and temporal patterns of dissolved nitrogen and phosphorus in surface waters of a multi-land use basin.
abstract: Research on relationships between dissolved nutrients and land-use at the watershed scale is a high priority for protecting surface water quality. We measured dissolved nitrogen (DN) and ortho-phosphorus (P) along 130 km of the Calapooia River (Oregon, USA) and 44 of its sub-basins for 3 years to test for associations with land-use. Nutrient concentrations were analyzed for spatial and seasonal patterns and for relationships with land-use and stream discharge. Ortho-P and DN were higher in lower-elevation sub-basins dominated by poorly drained soils and agricultural production compared with higher-elevation sub-basins dominated by well-drained soils and forests. Eight lower basins had at least one sample period with nitrate-N > 10 mg L(-1). The Calapooia River had lower concentrations of dissolved nutrients compared with lower sub-basins, often by an order of magnitude. Dissolved organic N represented a greater proportion of DN in the upper forested sub-basins. Seasonal nutrient concentrations had strong positive correlations to the percent of a sub-basin that was managed for agriculture in all seasons (p values ≤ 0.019) except summer. Results suggest that agricultural lands are contributing to stream nutrient concentrations. However, poorly drained soils in agricultural areas may also contribute to the strong relationships that we found between dissolved nutrients and agriculture.
authors.affiliation: Dept. of Crop and Soil Environmental Sciences, Virginia Tech, 330 Smyth Hall, Blacksburg, VA, 24061, USA, daniel76@vt.edu.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Evans
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Schoenholtz
authors.forename: Parker J
authors.initials: PJ
authors.lastname: Wigington
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Griffith
authors.forename: William C
authors.initials: WC
authors.lastname: Floyd
mesh_terms: D000383:Agriculture; D004784:Environmental Monitoring; D009584:Nitrogen / Q000032:analysis*; D009922:Oregon; D010758:Phosphorus / Q000032:analysis*; D045483:Rivers / Q000737:chemistry*; D062211:Spatio-Temporal Analysis; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014877:Water Pollution, Chemical / Q000706:statistics & numerical data; D014881:Water Supply
chemical_list: D014874:Water Pollutants, Chemical; D010758:Phosphorus; D009584:Nitrogen
references.citation: Ambio. 2002 Mar;31(2):88-96
references.pmid: 12078014
references.citation: J Environ Qual. 2004 Jan-Feb;33(1):201-9
references.pmid: 14964375
references.citation: J Environ Qual. 2003 Jan-Feb;32(1):162-70
references.pmid: 12549555
references.citation: Nature. 2002 Jan 24;415(6870):416-9
references.pmid: 11807551
references.citation: J Environ Qual. 2009 May 20;38(4):1473-82
references.pmid: 19465723
references.citation: Environ Manage. 2005 Mar;35(3):330-42
references.pmid: 15925975