Research Of The Influence Of Dispersant On Oil Spill Behavior And Characteristic Components

After oil spill happened at sea dispersant,as a kind of preferred emergency treatment measures besides mechanical recovery,plays an irreplaceable role.However,spilled oil is just dispersed into water by dispersant,not completely disappearing,it is possible to refloat to the water surface.Ups and downs behavior of oil spill,weathering path and environmental fate of some oil components,and fingerprint information and traceability of oil spill are likely to be changed when spilled oil mixed with dispersant.In view of this,dispersion behavior of oil spill was studied in a small tank in this paper.The influence of dispersant on alkane components weathering,alkane diagnostic ratio stability and digitalization identification results of oil spill based on stability diagnostic ratios was mainly investigated.The research results obtained are as follows:1.The influence of dispersant on oil spill dispersion behavior was studied by investigating dispersant content in oil slick and concentration of dispersed oil in water changing with time.The results indicate that dispersant is slowly away from oil slick with dispersion time increases,the greater the initial content,the faster the escape speed,and residual amount of dispersant in oil slick conforms to the cubic function.The detachment speed of dispersant basicly keeps water body of adding seawater the greatest,followed by replacing seawater and invariable seawater.The former two have fallen by 90%and 50%in 9 days respectively,and the third one is about 90%within 30 days.The corresponding oil concentration decreases gradually with dispersion time increases,and the decreasing trend is more in line with logarithmic function.In addition,dispersant separates from spilled oil mainly through the progress of dissolution and diffusion,evaporation is weaker.Open water body can speed up dispersant separating from oil slick,strengthen dispersant's redispersibility,accelerate dispersed oil diffusing into water,and improve the dispersion effectiveness.Dispersant that has been soluble in water has certain stability for the dispersed oil droplets.2.The influence of dispersant on alkane component weathering of oil spill was quantified by calculating weathering index(WI),evaporation index and biological degradation index,fitting WI with the exponential decay equation and comparing actual value with estimated value of WI.The results demonstrate that oil slick quickly disappears mainly by dispersant accelerating dissolution and evaporation.Dispersant interferes with oil weathering,leading to weathering path more or less deviating from the original one.What's more,weathering characteristics of dispersant may also affect weathering law and kinetic characteristics of oil spill.Biodegradation of simulated oil spill is non-significant,so the changes of alkane components are mainly caused by evaporation and dissolution.The influence of dispersant on C18 and Ph is also very weak,and the two nearly keeps same low weathering rate.3.10 stable diagnostic ratios resistance to dispersant interference and weathering were selected from 19 ones in a step by step way through repeatability limit method that is adjusted for processing large quantities of data.They are C17/(C17+Pr),C18/(C18+Ph),Pr/(Pr+Ph),CPI.(x=0,1,2,3 or 4)and OEPx(x=3 or 4).Based on these,simulated oil samples at different weathering stages were identified by digitization analyses methods.The results manifest that different kinds of oil(crude oil and fuel oil)weathering for 90 days or less can be clearly classified,identification scopes of oil samples mixed dispersant are significantly narrowed and the traceability efficiency is improved by principal component analysis,multidimensional scaling analysis and clustering analysis.Gray correlation analysis results through quantifying closeness relationship between oil samples and sources show that oil samples(weathering for 90 days or less)without dispersant are always intimately related to their actual oil source.For oil samples mixed with dispersant and weathering for 15 days or less,the relativity between oil samples and source along with dispersant content increasing is weak.When weathering time increasing to 90 days,the relativity between oil samples and source presents irregular change and classification result is very unstable,which is enough to prove that the influence of dispersant on oil spill digitalization identification results exists certainly.Therefore,gray correlation analysis is more suitable for oil spill identification with long-term weathering than the fomer three methods,and it is also an effective method for clearly confirming oil spill traceability is indeed affected by dispersant.