Tracing Water Mixing And Submarine Groundwater Discharge Of Jiaozhou Bay By Radium

Bay is an important part of the coastal ecosystem, which is also affected by human activities seriously. Analysis the activity level and distribution characteristics of radium isotopes of jiaozhou bay, and take use of radium isotopes to tracer water mixing, water age and submarine groundwater discharge are the effective ways to study the source and balance of payments of materials of Jiaozhou Bay. In this study the methods of determining 224Ra by RAD7 was established. The Time and space distribution characteristics of 224Ra and 223Ra of Jiaozhou Bay was analyzed. Radium isotopes were used as tracers to quantify water mixing processe. Water age of surface water was calculated via"Apparent Radium Ages Model" and compares the calculation results of the tidal prism method; Final this study take use of’ Radium isotope mass balance modeF" to estimate SGD and nutrients fiux of diffent season.This research mainly get the following conclusion:(1)when using RAD7 determine 224Ra activity, The more dry column in system the greater the influence on the precision of the measurement. Extending the time of measurement can improve the precision of the measurement. Useing a small dry column, for 60 min test time can get the best effection of test, The average efficiency is6.57±0.19%(n=7)(2)High 224Ra concentrations were found ebb tide, and low values were in high tide in Jiaozhou Bay, but the activity of 223Ra don’t Show the obvious regularity.224Ra and 223Ra activity have obvious seasonal characteristics, And is closely related to the corresponding season precipitation. The estuary around Jiaozhou bay and shallow area of Jiaozhou bay have the higher activity of 224Ra and 223Ra. For 224Ra, the distribution characteristics of the summer and autumn are same, that at the top of the bay and at the esturay where have the highest activity. In winter and spring 224Ra distribution characteristics are same, that low activety of 224Ra in the most area of the bay. For 223Ra, Autumn, spring and winter (except in September 2013), the activity distribution is more homogeneous in surface water; But in summer the 223Ra activity are higher obviesly than sping, autumn and winter. The distribution in summer of 223Ra is the same as 224Ra in the same season.(3)The distribution of 224Ra and salty combine with T-S indicator can tracer water mixing of Jiaozhou Bay and water out of the bay. In the spring of 2013 the phosphate (DIP) and silicate (DSi) concentration variation of Jiaozhou Bay is mainly controlled by the water out of the Bay, but the factor, which influences Total nitrogen(DIN), are complex. NH4+and NO2- are positively correlated with the 224Ra, negative correlation with salinity, illustrates two kinds of reducing nitrogen nutrient is likely to be the major source of SGD. In 2014,the main factor controlled DIP and DSi is the same with 2013, but the factor which controlled DIN of 224Ra is different with 2013. Terrigenous input and human activities on the jiaozhou bay in spring in 2013 had a great effect on surface water’s DIN, but in the spring of 2014 SGD has significant effects on DIN. The water age of Jiaozhou Bay of different season is as follows:Spring is 10.0 day, summer is 12.9 day, autumn is 9.6 day, winter is 16.9 day.(4)SGD is a important source of 224Ra of Jiaozhou Bay, the 224Ra which from SGD is account for 45.9%～75.9%. SGD flux of Jiaozhou Bay is more higher than river around the study area, which range from 4.37cm/d～12.02cm/d. The SGD flux of summer and autumn is ecqual, the sum SGD flux of summer and autumn account tor about 70% of all year. The flux of spring is a little higher than winter, the sum SGD flux of spring and winter is acount for about 30% of a year.The nutrients from SGD is important source of Jiaozhou Bay. The nutrients from SGD is concentrated in summer and autumn, The DIN, DIP and DSi from SGD is all account for 70% of the amount flux in a year. NH4-N is main form of DIN which from SGD. In a year, NH4-N account for 75.7% of DIN,which from SGD.(5) There was a positive correlation among DIN, DSi, NO2-, NO3-with 224Ra in spring. In summer, exceept DSi, the rest of the nutrients have good positive correlation with 224Ra, besides the r2 of DIP and NH4+ with 224Ra are higher than that in sping, which indicates that the control degree of SGD to DIP and NH4+ is higher than that in spring. All nutrients have significantly positive correlation with 224Ra in autumn, which indicate that in autumn SGD control all the nutrients. In winter, all nutrients have significantly positive correlation with 224Ra. Nutrients are highly controlled by SGD, because the rivers flow is reduced grently in winter.