Using 224Ra to track coastal water mixing process and nutrients source in Qingdao Coast

In this study,we investigated the spatio-temporal distribution of excess 224Ra (224Raex) and its influence factors in the Qingdao coast,and further used it as tracer to evaluate the water mixing process and nutrients source.The following informations were obtained:the activity of 224Raex range from 1.30.2 dpm/100 L to 10.21.3 dpm/100 L.High radium concentrations were found in nearshore and ebb tide,and low values were in offshore and high tide.We found that 224Ra-salinity was a better choice to track the water mixing process in the study area than salinity-temperature pair.The correlation of 224Raex and salinity with nutrients were used to discuss the nutrients souces.In March 2013,DIP and DSi concentrations were mainly controlled by tidal mixing in the Qingdao coast,but DIN might have multi-sources,such as riverine input,industrual and domestic wastewater,tidal mixing and submarine groundwater discharge.