Investigation On The Interactions Between Macroalgae And Several Important Nuclides And Its Applications

Recent years have witnessed worldwide increase in the number of nuclear power plants(NPPs)along coastal regions.Following the Fukushima 1 Nuclear Power Plant(F1NPP)accident,the issue of marine radionuclide pollution has attracted special public attention.Radionuclide pollution would have a serious impact on coastal ecological environment and even human health.Several methods have been developed to remove radionuclides from aqueous solution,including physical,chemical and biological remediation.Bioremediation has the advantages of high efficiency,low cost,easy operation and environmental friendliness.Aiming at the problem of marine nuclide pollution,the present study investigated the stress of several prime nuclides on macroalgae growth,the adsorption of algae to nuclides and the application of macroalgae in the remediation of seawater nuclide pollution.Studies on the stress of cobalt on different growth stages of macroalgae Saccharina japonica and Undaria pinnatifida showed that high concentration of cobalt can inhibit the spore germination,gametophyte vegetative growth,gametogenesis,juvenile sporophyte formation,sporophyte vegetative growth and chlorophyl fluorescence efficiency of S.japonica and U.pinnatifida.Sensitivity of algae to the nuclide cobalt at different growth stages was ranked as follows:gametogenesis > gametophyte vegetative growth(sporophyte vegetative growth)>spore germination.Gametogenesis stage is the transition process of algae from microscopic gametophyte generation to macroscopic sporophyte generation.The inhibition of this stage will seriously affect the formation of sporophyte population and thus affect the coastal ecological environment.Studies on the nuclides adsorption by algae have shown that the adsorption capacity of different algae to nuclides is very different,so the selection of algae species is very important.Sargassum horneri and S.japonica have strong adsorption capacity of strontium,with the adsorption equilibrium state conforming to the Langmiur equation and Freundlich equation and the adsorption kinetics conforming to the pseudo-second-order kinetic equation.The cesium content in algae increased significantly,with the increase of cesium concentration in seawater.S.japonica also has strong ability to remove iodide from seawater.The results of tank simulation experiments showed that the adsorption rate of adult S.japonica to the nuclides strontium,cesium and iodine was much higher in the first 24 hours.After that,algae biomass could be repeatedly replaced by fresh biomass until the corresponding nuclides were reduced to the required concentration range.Obtaining large biomass in a short period is one of the main technical bottlenecks in the application of live macroalgae to the marine nuclide pollution remediation.The floating S.horneri and Ulva prolifera are the causative algae in the "golden tide" and "green tide" which occur frequently in recent years.With the purpose of transforming these waste to possibly exploitable material,this study investigated the remediation ability of S.horneri and U.prolifera to artificially simulating nuclides-polluted seawater and the adsorption dynamics.The results showed that S.horneri had a good removal effect on all the three nuclides in the seawater polluted by polynuclides(strontium,cobalt and manganese).U.prolifera has a good recovery effect on the seawater polluted by nuclide cesium and cobalt.In addition,by analyzing the genetic structure of different populations of S.horneri,we found that there was no significant genetic correlation between the newly formed benthic population and the nearby floating population that appeared later,and the reproduction mode of floating S.horneri biomass was mainly asexual.In summary,the present study systematically explored the interations between several prime nuclides and the common macroalgae in China,as well as the remediation potential and application prospect of these macroalgae in nuclide pollution.The results of these study can provide certain theoretical basis and technical guidance for remediation plan of marine radionuclide pollution in case of leakage accident of nuclear power plant.