The release behavior of inorganic nitrogen and phosphorus in sediment during disturbance

Sediments and surface water were sampled in a tide flat in the Huiquan Bay,Qingdao,China in January 2004 to simulate the exchange of NH4-N/NO3-N/PO3-4 between sediments and surface water.A working system was designed with which samples were shaken at 60,120 and 150 revolutions per minute (r/min).Experiment results show that NH4-N concentration in water at shaking rate of 60r/min decreased gradually,while at 120r/min increased gradually.In resuspension,fine-grained sediments contributed most NH4-N to the seawater,followed by medium-grained and coarse-grained sediments.The NO3-N concentration in water had a negative relation with the shaking rate; the medium-grained sediments contributed more NO3-N to seawater than the coarse- and fine-grained sediments.The PO3-4 concentration is positively related with the shaking rate,the fine-grained sediments were the main N and P contributor to the seawater,followed by medium- and coarse-grained sediments.