Study On The Assessment Methods Of The Red Tide Caused By Ships' Ballast Water

Now, it is the hot spots in the field of alien species invasion,while alien red tide algaes as the typical invasion species have gradually become an object of study. Most of the studies in China have been focusing on how to deal with ballast water,while it is difficult to find the relative risk assessment rather than quantitative evaluation system.So it needs to establish a reasonable risk assessment system to reduce the potential hazards.In this paper, Dalian port is used for the research object. Carry out a risk assessment to the ship from Qinhuangdao port to the port of Dalian. Constructe a risk assessment system of ballast water which causes red tide by using experimental method and mathematical model.Through experiments and case studies we can get the following conclusions:(1) In the conditions of no light, gas-liquid contact area and liquid volume ratio, the experimental temperature, the initial concentration of algae and nutrient levels all have affectes on the concentration changing of algal cells. With time exponentially,those factors and algal concentration have the exponential function relationship.To different algals, influence caused by factors is different.(2) When other factors remain unchanged, with the gas-liquid contact area and liquid volume ratio increasing, the concentration of algal cells increases; When other factors remain unchanged, with the experimental temperature ranging from 8 to 17℃increasing, algal cell concentration increases; When other conditions remain unchanged,with the initial concentration of algae increasing, algal cell concentration increases.(3) According to the simulated function and the parameters of the initial port (Qinhuangdao), the invasion risk value of red tide algae is 0.770,at a high risk level.(4) Comparing water temperature, air temperature, salinity and rainfall between Qinhuangdao port and Dalian port by using analogy deviation method, the environmental similarity value is 0.856, at a high risk level.(5)With selecting the water temperature, salinity, dissolved oxygen, total nitrogen and total phosphorus and using support vector machine approach, the risk value is 0.367, at a low risk level.(6) Calculating the risk causing by the vessel from Qinhuangdao port,the risk value is 0.623,at a moderate risk level.