Numerical Simulation Of Water Quality In Lianjiang Sea Area Of Fujian Province Based On FVCOM

In recent decades,the pollution of living garbage and industrial waste has exacerbated the eutrophication of nearshore water,and has caused frequent occurrence of red tides.This has caused great economic losses on fishery breeding along the coastal seawater and undermined the sustainable development of coastal waters.The establishment of hydrodynamic-water quality coupling model can effectively predict the trend of water quality variables,and provide technical support for coastal fishery breeding.Based on FVCOM(An Unstructured Grid,Finite-Volume Coastal Ocean Model)model,the hydrodynamic model with high resolution of Lianjiang waters in Fujian Province has been established.A three-dimensional hydrodynamic-water quality coupling model has been established based on the credible hydrodynamic result.The model can simulate the physical variables such as water elevation,temperature and flow field in Lianjiang waters,and can also simulate the spatio-temporal distribution characteristics of water quality variables such as chlorophyll a,dissolved oxygen and nutrient.The zero dimension model was established by using the formula from WASP(The Water Quality Analysis Simulation Program)model,and the parameter sensitivity experiment was carried out for phytoplankton.The main results of this paper are as follows:(1)This tida type of waters belongs to the regular half-day tide type.The tidal wave transmits mainly along the northeast coast of Fujian from northeast to southwest.The smaller distance from the shore was,the bigger amplitude showed.The equidistant amplitude line and the equidistant epoch line of the cotidal chart were essentially vertical in the coastal waters.The tidal wave showed the characteristics of the standing wave system which rotated counterclockwise.The maximum possible tidal range was nearly parallel to shoreline,from 5.5m in the coast to 9m.(2)The tidal current type of the north of Pingtan belongs to the regular half-daytidal current type,and the south of Pingtan belongs to the irregular half-day tide current type.The area close to the shoreline showed the performance of reciprocating flow.The area showed the performance of the rotating flow,such as Xinghua Bay,Pingtan and Minjiang River.The current ellipse figure showed that the half-day component current and full-day component current mainly rotated counterclockwise.(3)The mean absolute difference of tide elevation is less than 0.2m.The mean absolute difference of velocity is less than 0.08m/s,and the mean absolute difference of current direction is less than 30°.The mean absolute difference of temperature is less than 1?.(4)The verification result was obtained by comparing the numerical simulation results of dissolved oxygen among the water quality state variables with the buoy data.The mean absolute difference was about 0.32mg/l.The spatio-temporal variations of monthly average for chlorophyll a,nitrate and nitrite,active phosphate in spring and summer were analyzed based on the simulation results.(5)Several sensitivity experiments of parameters were made for phytoplankton.The results showed that the higher sensitivity parameters included the optimum phytoplankton growth rate,the mortality rate of phytoplankton and phytoplankton respiration rate.