title: A spatial analysis of phosphorus in the Mississippi river basin.
abstract: Phosphorus (P) in rivers in the Mississippi River basin (MRB) contributes to hypoxia in the Gulf of Mexico and impairs local water quality. We analyzed the spatial pattern of P in the MRB to determine the counties with the greatest January to June P riverine yields and the most critical factors related to this P loss. Using a database of P inputs and landscape characteristics from 1997 through 2006 for each county in the MRB, we created regression models relating riverine total P (TP), dissolved reactive P (DRP), and particulate P (PP) yields for watersheds within the MRB to these factors. Riverine yields of P were estimated from the average concentration of each form of P during January to June for the 10-yr period, multiplied by the average daily flow, and then summed for the 6-mo period. The fraction of land planted in crops, human consumption of P, and precipitation were found to best predict TP yields with a spatial error regression model ( = 0.48, = 101). Dissolved reactive P yields were predicted by fertilizer P inputs, human consumption of P, and precipitation in a multiple regression model ( = 0.42, = 73), whereas PP yields were explained by crop fraction, human consumption of P, and soil bulk density in a spatial error regression model ( = 0.49, = 61). Overall, the Upper Midwest's Cornbelt region and lower Mississippi basin had the counties with the greatest P yields. These results help to point out specific areas where agricultural conservation practices that reduce losses to streams and rivers and point source P removal might limit the intensity or spatial occurrence of Gulf of Mexico hypoxia and improve local water quality.
authors.affiliation: Dep. of Natural Resources and Environmental Sciences, Univ of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Linda M
authors.initials: LM
authors.lastname: Jacobson
authors.forename: Mark B
authors.initials: MB
authors.lastname: David
authors.forename: Laurie E
authors.initials: LE
authors.lastname: Drinkwater
mesh_terms: D000383:Agriculture; D003247:Conservation of Natural Resources; D004784:Environmental Monitoring; D005308:Fertilizers; D006802:Human Activities; D006801:Humans; D008962:Models, Theoretical; D010758:Phosphorus / Q000032:analysis*; D011891:Rain; D045483:Rivers; D012987:Soil; D014481:United States; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D005308:Fertilizers; D012987:Soil; D014874:Water Pollutants, Chemical; D010758:Phosphorus