Variations in streamwater nitrate concentrations and nitrogen budgets over 10 years in a headwater catchment in mid-Wales

摘要: Between 1980 and 1989, samples of bulk precipitation, soil water stream have been collected regularly from a small catchment within the headwaters River Wye at Plynlimon. Subsequent analysis for nitrate-N ammonium-N revealed that was present in precipitation but concentrations were below detection limit (< 0.1 mg 1−1N) waters streamwaters. Over 10 year period, no consistent trends observed concentration or wet deposition inorganic nitrogen compounds. 1983, varied irregularly over time, contrast to regular pattern summer minima winter maxima stream. Following dry 1984, large increases such during 1985, maximum increased by factor two ten as compared with previous years. Winter declined gradually following 3 years values similar those prior 1984. The variations streamwater nitrate are discussed relation processes controlling supply depletion channel. significance Plynlimon is on basis data an adjacent headwater simple mass balance comparing compounds exports Although leaching losses vary between 4 5 kg ha−1 year−1, there net retention catchment. also indicates transformations may generate average 0.34 kEq H+ year−1.