NÄRSALTRETENTION I EN NYANLAGD DAMM I SKÅNE 1. MÄTRESULTAT / Nutrient retention in a created pond in southern Sweden I. Results
Mass-balance studies of nitrogen, phosphorus, and suspended matter have been carried out in a created pond. The pond is situated in the drainage basin of a farmland stream in Scania, southern Sweden. The investigation started shortly after the creation of the pond and has continued for three years. The aim of the study was to quantify the effect of the pond on the transport of nitrogen and Phosphorus. The retention of these nutrients varies considerably, both seasonally and annually. The annual variations have been interpreted as due to the changes properties of the pond and to different weather conditions principally precipitation. The retention efficiency of the pond has increased. It is estimated at about 1000 kg of nitrogen and 30 kg of phosphorus per hectare wet area during a year with normal runoff. Nitrogen retention is observed even during winter conditions, normal for this part of Sweden. Although relative retention then only amounts to a few per cent, absolute retention may be considerable due to the high nitrogen load. Methods of measurements and calculation are discussed in some detail. Continuous recording of water flow is one requisite for obtaining reliable mass-balances. Measurements of this kind have to pursued for a considerable period of time in order to assess the yearly meteorological and hydrological variations