Factors Affecting Nitrate Distribution in Shallow 10 Groundwater under a Beef Farm in South Eastern Ireland

22 Groundwater contamination was characterised using a methodology which combines 23 shallow groundwater geochemistry data from 17 piezometers over a 2 yr period in a 24 statistical framework and hydrogeological techniques. Nitrate-N (NO3-N) 25 contaminant mass flux was calculated across three control planes (rows of 26 piezometers) in six isolated plots. Results showed natural attenuation occurs on site 27 although the method does not directly differentiate between dilution and 28 denitrification. It was further investigated whether NO3-N concentration in shallow 29 groundwater (<5 m below ground level) generated from an agricultural point source 30 on a 4.2 ha site on a beef farm in SE Ireland could be predicted from saturated 31 hydraulic conductivity (Ksat) measurements, ground elevation (m Above Ordnance 32 Datum), elevation of groundwater sampling (screen opening interval) (m AOD) and 33 distance from a dirty water point pollution source. Tobit regression, using a 34 background concentration threshold of 2.6 mg NO3-N L -1 showed, when assessed 35 individually in a step wise procedure, Ksat was significantly related to groundwater 36