HYDROLOGICAL PROCESSES Hydrol. Process. 20, 2077–2081 (2006) Published online 24 March 2006 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/hyp.6143 Short Communication Potential nitrate leaching to groundwater from house building Fernando T. Wakida 1 * and David N. Lerner 2 1 Facultad de Ciencias Qu´ ımicas e Ingenier´ ıa, Universidad Aut´ onoma de Baja California, Calzada Tecnol´ ogico 14418, Mesa de Otay, Tijuana, Baja California, Mexico 2 Groundwater Protection and Restoration Group, Department of Civil & Structural Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD, UK Abstract: Nitrate pollution has been identified as a major water quality issue in the UK. This study aimed to determine the potential additional loading of nitrate that could arise from the disturbance caused by house construction. The study is centred around the towns of Nottingham and Mansfield, UK, which are situated on a Triassic Sandstone aquifer. Soil samples up to a depth of 2Ð70 m were taken from seven sites under construction and other land uses. The average nitrogen load was 59 kg ha 1 , which is slightly higher than the nitrate leaching observed when temporary grassland is ploughed in temperate climates. The most important factors involved in nitrogen loss from house building are expected to be previous land use, quantity of total nitrogen after topsoil stripping, and seasonal timing of construction. Copyright  2006 John Wiley & Sons, Ltd. KEY WORDS nitrate leaching; ploughing; urban groundwater; Nottingham; construction INTRODUCTION Nitrate is usually seen as an agricultural pollutant, given that it often arises from the use of fertilizer. Consequently, a large difference in its concentration in aquifers beneath cities and agricultural land might be expected. However, studies conducted by Lerner et al. (1999) in the UK have shown that this difference can be small. They also used recharge and nitrogen concentration data to estimate the total nitrate loading in the Nottingham urban area to be 21 kg ha 1 year 1 . Thus, there are non-agricultural sources that contribute to nitrate concentrations in groundwater. Most of these sources are related to urban development (Wakida and Lerner, 2005). Nitrate leaching as a result of soil disturbance by house building falls into this category and, to our knowledge, has not been researched. House construction is as destructive of vegetation and soil organic matter as ploughing of pasture or other ways of clearing vegetation. The processes are not entirely similar, because house building involves the stripping of topsoil from the sites. However, organic matter is left below the soil surface (including roots and macro-organic matter fractions), which can be mineralized to nitrate and potentially leach with drainage of excess water. Topsoil disturbance by ploughing increases soil aeration and mixes the available carbon and nitrogen sources with soil organisms. This process leads to nitrate accumulation in the soil due to mineralization and nitrification processes. When the soil is left fallow during winter, nitrate is leached by drainage of excess water (McLenaghen et al., 1996). * Correspondence to: Fernando T. Wakida, PMB 184, 710 East San Ysidro Blvd, San Ysidro, CA 92173, USA. E-mail: fwakida@uabc.mx Received 18 February 2002 Copyright  2006 John Wiley & Sons, Ltd. Accepted 10 August 2005