 Approximately 400 kg phosphorus is transported through the lake annually, of which some 80 per cent comes from the other lakes in the water system.Surface runoff adds some 50 kg phosphorus and 600 kg nitrogen, while roughly 24 kg phosphorus is released from lake sediments and atmospheric deposits adds some 120 kg of nitrogen.Most of metal contribution, copper, lead, and zinc, comes from Hammarbybacken where high levels of arsenic, chromium, phthalates, PCB, and Carbon tetrachloride have also been recorded.