 Local storm water pipes, occasionally fouled with oil of unknown origin, produces most of the affluent, with remaining contributions coming from local roads and run-off from residential areas, the latter bringing mostly nutrients to the lake with minor contributions of zinc and copper (from roofs).High levels of phosphorus have been recorded during late winters and summer.Reports in 1991-1997 of metal content in lake sediments noted moderate levels of copper, the highest levels of lead in any lake in Stockholm, and raised levels of organic compounds such as PAHs and PCB in lower sediments.