The Impact Of Bioturbation On Sediment-associated Petroleum Hydrocarbons Degradation In Marine Environment

The development of oil transportation and oil exploration lead marine oil pollution continues input,a series of physical and chemical changes will happen after oil pollutants into the marine environment,eventually oil pollutants will settle into the sediment and make the marine sediments become petroleum contaminants sink.Bioturbation can change the structure of the deposited layer,promote the migration of particulate matter,thereby it can affect the migration of contaminants in sediments and release of contaminants into the water layer.Bioturbation process changes the redox environment of the deposited layer,influence sediment geochemical processes and change the composition and vitality of microflora in the sedimentary environment,which contributing to the degradation of petroleum hydrocarbons in sediments.This thesis focus on petroleum hydrocarbon pollution problems in coastal sediments,we study the bioturbation of Perinereis aibuhitensis's influnce on release of petroleum hydrocarbons contamitation buried different depth and also study the migration and degradation of petroleum hydrocarbons in the sediment by indoor microcosm experimental systems.The main conclusions are as follows:The bioturbation of P.aibuhitensis promotes the resuspension of deposition particulate matter,so the concentrations of total suspended particles(TSS)and dissolved organic carbon(DOC)in overlying water are significantly increased.The content of TSS in overlying water of bioturbation group is significantly higher than the control group;DOC in overlying water of bioturbation group is also higher than the control group,with the experiment continue,the content of DOC in overlying water shows a rising trend.By correlation analysis of TSS and DOC,TSS and DOC in upper water is significantly correlated(P<0.05)and irrelevant in lower water(P>0.05).Bioturbation can significantly promote the release of pollutants into the water,after 30 days experiment,the fluxes of pristane,nonadecanoic,phenanthrene and pyrene are 3046.44 ng m-2 day-1,612.88 ng m-2 day-1,369.32 ng m-2 day-1,124.33 ng m-2 day-1 in deep burial bioturbation group.In shallow burial bioturbation group,the fluxes of pristane,nonadecanoic,phenanthrene,and pyrene are 3506.78 ng m-2 day-1,810.06 ng m-2 day-1,60.51 ng m-2 day-1,75.69 ng m-2 day-1.In the deep and shallow burial biotubation group,the release of pollutants is mainly in form of particulate,respectively accout for 56%-99%and 47%-99%of total emissions,which indicate that bioturbation can promote the resuspension of deposition particulate matter,increase the content of pollutants in water.Within the bioturbation range,the emissions of pollutants is no significant difference in different burial depths,this means the release has no correlation with the pollutant's burial depth.Bioturbation have a significant impact on the vertical migration of contaminants in sediments.In deep burial experimental group,the migration range of contaminants can reach the sediment surface,the initial placement of each contaminants set at 10cm from the surface,after 30 days experiment,the longitudinal distribution of contaminants range from the surface to 15cm,mobility of pristane,nonadecanoic,phenanthrene and pyrene are 10.3%,6.5%,11%and 5.8%,respectively.In shallow burial experimental group,the migration range of contaminants can reach the sediment bottom,the initial placement of each contaminants set at 2cm from the surface,after 30 days experiment,the longitudinal distribution of contaminants range from the surface to 15cm,mobility of pristane,nonadecanoic,phenanthrene and pyrene are 12%,11.7%,11.9%and 17.3%,respectively.In no P.aibuhitensis control group,the migration of contaminants in the range of 2-4cm.Bioturbation on the migration of aromatic hydrocarbons are more obvious,which may be related to the characteristic of the contaminant itself.After 30 days experiment,pollutants in P.aibuhitensis bioturbation group is significantly lower than the levels of no P.aibuhitensis control group,which indicate bioturbation can promote the degradation of sediments pollutants.In deep burial experimental group,the degradation rate of pristane,nonadecanoic,phenanthrene and pyrene are 39%,54%,33%and 35%,respectively.In shallow burial experimental group,pristane,nonadecanoic and phenanthrene degradation rates are 52%,73%,65%and 65%,respectively.Compare deep 'burial experimental group with shallow burial experimental group,the degradation of shallow burial group is more effective.This may be because the shallow sediments' oxidizing environment is more conducive to microbial flora of aerobic degradation.