Research On The Formation Of Oil-suspended Particulate Matter Aggregates On Jiaozhou Bay

With the vigorous development of offshore oil industry and oil transportation industry,the oil spill accident in Jiaozhou Bay area has been frequent,which has brought serious harm to the local economy and environment.The oil spill will eventually be degraded by microbes and thoroughly removed.The natural suspended particulate matter in the ocean will form Oil-Suspended Particulate Matter Aggregates?OSAs?with spilled oil under marine hydrodynamic conditions,which can promote the biodegradation of oil spills.However,it is necessary to further explore the mechanism of how suspended particulate matter can promote biodegradation.This experiment selected the suspended particulate matter in Jiaozhou Bay,kaoline and bentonite as experimental particles,Shengli crude oil,crude oil 1#and Venezuela crude oil as the representative oil,meanwhile simulating the ocean wave environment for researching on the formation characteristics of oil-suspended particulate matter with constant temperature oscillation.This experiment mainly investigated the composition and physicochemical properties of representative suspended particulate matter and oil on Jiaozhou bay and the effects of different concentration of suspended particulate matter,suspended particulate matter size,salinity,pH,weathering degree and oil dispersant on the properties of oil/water interface and the degradation characteristics of spilled oil.The experimental results showed that density and concentration of suspended particulate matter increased with the increase of water depth from 0-8 meters,and the concentration of suspended particulate matter in bay mouth was larger than in the bay.The content of organic matter decreased with the increase of depth;for the petroleum hydrocarbon content,the content of petroleum hydrocarbon in the wharf area was the highest,up to 32.12 mg�kg^-1.The surface tension between crude oil and seawater could be reduced from 14.9 mN�m^-1to 4.5 mN�m^-1 and Zeta potential of emulsion increased from -11.8 mV to -3.8 mV with different concentrations of suspended particulate matter.The smaller of the particles size,oil/water interfacial tension would be smaller and and Zeta potential would be bigger.The oil/water interfacial tension decreased and Zeta potential increased with the increase of salinity.The oil/water interfacial tension and Zeta potential decreased first and then increased increasing of pH.The oil/water interfacial tension can be further reduced to 0.1mN�m^-1 and Zeta potential can be increased to -1.9 mV under the condition of added oil dispersant.The microbial clearance efficiency of spilled oil was 34.81%.After adding natural suspended particulate matter,bentonite and kaoline,the microbial clearance efficiency of spilled oil can reach at 40.50%,43.34% and 46.89%,respectively.With the increase of concentration and decrease of the size particle,the microbial clearance efficiency of spilled oil was gradually increased.When the salinity was between 0-5 ppt,the low salinity resulted in the low microbial clearance efficiency of spilled oil.The microbial clearance efficiency of spilled oil could reach a maximum at 49.20% and 48.40%,respectively.Particulates were basically no effect on the microbial clearance efficiency of spilled oil as weathering.For Venezuelan crude,Shengli crude and crude 1#,the minimum microbial clearance efficiency of spilled oil were 25.00%,15.63% and 8.86%,respectively.When kaoline was added,the removal efficiency of the spilled oil was the highest,up to 63.86%.The addition of oil elimination agent could promote the spilled oil removal efficiency of OSAs,which can reach a maximum of 68.00%.Added natural suspended particulate matter,bentonite and kaoline can cause the size of the OSAs was 31.62?m,27.21?m and 21.32?m,respectively and oil droplet size reducsed from 17.62?m to 12.31?m,11.47?m and 10.17?m.The oil droplets become more dispersed in OSAs when added kaoline.Bentonite led to elongation type OSAs increased and natural suspended particles led to hollow shape OSAs.With the decrease of the size and the increase of concentration,OSAs size and oil droplet size decreased,meanwhile the formation of OSAs increased.There was no OSAs formation and oil droplet size was very large,when salinity was too low.With the increase of DOR,the size of OSAs reached at 14.34?m and the minimum oil droplet size reached at 1.94?m.The OSAs formation rate decreased gradually with the weathering and the size of OSAs reached to 41.00?m and oil droplet size reached to 25.03?m.Under the affect of microorganisms,the carbon content components between C8?C12disappeared.Aromatic hydrocarbon derivatives were very high proportion,when salinity was 0 and 3 ppt.Weathering caused light components volatilization and the proportion of high carbon content increased.With the increased of DOR,promoted the oil spilled,the proportion of n-alkanes and aromatic hydrocarbons gradually decreased,and the proportion of hydrocarbon derivatives increased gradually.