| Abstract: |
Net anthropogenic nitrogen inputs (NANI), composed of oxidized N deposition, fertilizer N application, agricultural N fixation, and net food and feed imports, estimate human-induced nitrogen inputs to a region and have been shown to have a strong relationship with riverine nitrogen export. Since its first introduction, it has been applied to various regions of the US, including the subbasins of the Chesapeake Bay watershed, and the world by numerous researchers. Comparison and synthesis of these studies have been somewhat problematic due to discrepancies in the data sources and assumptions applied in their calculations. To address this problem, it would be useful to have a set of tools for calculating NANI from a standardized dataset allowing the user to clearly see the assumptions behind the calculations and alter them to test their sensitivity. Here we present a prototype of such a toolbox, the NANI Calculator Toolbox. The toolbox is composed of three sets of tools: (1) a GIS tool overlaying a watershed map with various data maps to calculate overlaying proportions, (2) a set of Excel based tools extracting necessary data from various standardized datasets (Agricultural Census, Census, USGS fertilizer input estimates, and CMAQ N deposition estimates), and (3) an Excel based tool calculating the NANI budget and other related components (e.g., manure production by animals) from the extracted data. All the datasets are included in this package, allowing the user to calculate NANI anywhere in the US from the watershed map of interest. As a demonstration, we present county-scale NANI estimates for the entire continental US and also for the subbasins of the Chesapeake Bay watershed. Possible extension of the datasets to European countries and the use of the outputs for parameterizing the regional hydrology and nutrient loading model ReNuMa (Regional Nutrient Management) are discussed. |
