Verifiable metamodels for nitrate losses to drains and groundwater in the Corn Belt, USA

Nolan, B. T.; Malone, R. W.; Gronberg, J. A.; Thorp, K. R.; Ma, L.

Abstract:

Nitrate leaching in the unsaturated zone poses a risk to groundwater, whereas nitrate in tile drainage is conveyed directly to streams. We developed metamodels (MMs) consisting of artificial neural networks to simplify and upscale mechanistic fate and transport models for prediction of nitrate losses by drains and leaching in the Corn Belt, USA. The two final MMs predicted nitrate concentration and flux, respectively, in the shallow subsurface. Because each MM considered both tile drainage and leaching, they represent an integrated approach to vulnerability assessment. The MMs used readily available data comprising farm fertilizer nitrogen (N), weather data, and soil properties as inputs; therefore, they were well suited for regional extrapolation. The MMs effectively related the outputs of the underlying mechanistic model (Root Zone Water Quality Model) to the inputs (R 2 = 0.986 for the nitrate concentration MM). Predicted nitrate concentration was compared with measured nitrate in 38 samples of recently recharged groundwater, yielding a Pearson‘s r of 0.466 (p = 0.003). Predicted nitrate generally was higher than that measured in groundwater, possibly as a result of the time-lag for modern recharge to reach well screens, denitrification in groundwater, or interception of recharge by tile drains. In a qualitative comparison, predicted nitrate concentration also compared favorably with results from a previous regression model that predicted total N in streams. ?? This article not subject to U.S. Copyright. Published 2011 by the American Chemical Society.

Genre:

Article

ProdID:

70032658

Citation Author:

Nolan, B. T.; Malone, R. W.; Gronberg, J. A.; Thorp, K. R.; Ma, L.

Citation Contributing Office:

Citation Datum:

Citation Day:

Citation Edition:

Citation Editor:

Citation End Page:

908

Citation Issue:

Citation Keywords:

Citation Language:

English

Citation Larger Work Title:

Environmental Science and Technology

Citation LatN:

Citation LatS:

Citation LonE:

Citation LonW:

Citation Month:

Citation No Pagination:

Citation Number Of Pages:

Citation Online Only Flag:

Citation Phsyical Description:

Citation Projection:

Citation Public Comments:

Citation Publisher:

Citation Series:

Citation Series Code:

Citation Series Number:

Citation Search Results Text:

Verifiable metamodels for nitrate losses to drains and groundwater in the Corn Belt, USA; 2012; Article; Journal; Environmental Science and Technology; Nolan, B. T.; Malone, R. W.; Gronberg, J. A.; Thorp, K. R.; Ma, L.