| Oil is the pillar of the world's economic development,and oil exploitation plays a vital role in social and economic development.Landfall crude oil is the main cause of soil pollution in oil fields.It diffuses through surface runoff and pollutes the surrounding soil,surface water,sea water and tidal flat.On the one hand,many oil fields in the world are mostly distributed in the saline-alkali flats or inland saline-alkali soil areas.On the other hand,the discharge of salt-bearing produced water from oil exploitation will also cause the salinization of the soil in the oilfield exploitation area.Therefore,the restoration of oil-polluted saline-alkali soil has become a research hotspot at home and abroad in recent years.Salinization has changed the physical and chemical properties of soil and inhibited the growth and metabolism of soil microorganisms,which has become the main difficulty in realizing microbial remediation of petroleum contaminated saline-alkali soil.Because of its economy and environmental protection,microbial remediation has become one of the main methods for remediation of petroleum pollution.However,the problem of remediation of oil-contaminated saline-alkali soil requires further research on the screening of functional microorganisms that can withstand saline-alkali stress and the regulation of their growth conditions.In this paper,we study the following content:first of all the production plant of daqing oil Wells mouth nearby soil sampling,analysis of ground crude oil migration patterns,the degree of saline soil and the physical and chemical properties,and then screening salt-tolerant petroleum hydrocarbon degradation microbes,and the growth,the degradation conditions on screening of strain response surface optimization,the screening of strains was applied to oil pot simulation of saline soil bioremediation experiment.Production wellhead sampling research results show that the wellhead sampling points around petroleum hydrocarbon content up to 15.32 g·kg-1,petroleum hydrocarbon oil hydrocarbon migration in gentle zone is slow and reduce with the increase of distance,petroleum hydrocarbon content in the 10-20 m minimum 0.76g·kg-1,surface water in the lakes and other low-lying petroleum hydrocarbon pollutants in the soil will gradually accumulate,petroleum hydrocarbon content accumulated up to 4.26 g·kg-1;The determination of soil p H showed that the soil p H was between 8.3-10.0,and the soil was divided into alkaline soil and alkaline soil according to the classification standard of soil alkalinity.Based on the analysis of water-soluble salt content in soil,the soil was divided into mild salinization soil according to the classification standard of soil salinization.Bacteria content in soil is less,mainly in the 10~5-10~6 CFU·g-1,where high oil content,high moisture content of the bacteria were significantly higher;PH and salt content had no significant effect on the number of bacteria in the soil,indicating that the bacteria in the soil were mainly saline-tolerant bacteria and could tolerate a small range of saline-alkali changes.Saline-resistant petroleum hydrocarbon degrading bacteria were isolated from the oil-contaminated soil near the well head by means of saline-alkali stress.The results of the isolation and screening of saline-alkali oil-degrading bacteria showed that LD2,LD8 and D2 were obtained,and the biodegradation rates of 7 days were38.31%,39.18%and 41.27%,respectively.After morphological observation,physiological and biochemical identification,and 16S r DNA identification,strain LD2 was Stenotrophomonas Maltophilia with the login number MN192109,strain LD8 was Bacillus with the login number MN192115,and strain D2 was Acinetobacter with the login number MW048780.Through the growth curves of strains LD2,LD8 and D2,the optimal inoculation time,i.e.,the stable period,was 18h,36 h and 21 h,respectively.The response surface optimization study on the growth of strain D2 showed that the optimal carbon and nitrogen sources of strain D2 were glucose and ammonium sulfate respectively,and when glucose and ammonium sulfate were used as the carbon and nitrogen sources,the optimal ratio of carbon,nitrogen and phosphorus for the growth was 100:10:1.The results of single factor experiment of crude oil degradation showed that when the p H of fungus D2 was 9.0,the biodegradation rate reached the maximum value of 40.48%,that is,the optimum p H was 9.0,and fungus D2 was an alkaloid bacterium.The optimal concentration of Na CI is 1%(that is,the salt content is 13.27 g·kg-1),a mild halophilic bacteria strains;When the glucose concentration was 0-4%,the proportion of glucose in the carbon source utilization gradually increased,and when the glucose concentration was 4-5%,the proportion of glucose in the carbon source utilization gradually stabilized.The degradation rate decreased significantly faster after the crude oil concentration reached 3%,indicating that the growth of D2 was inhibited after the crude oil concentration reached 3%.Strain D2ideal biodegradation conditions is therefore in the p H=9.0,Na CI concentration was1%(that is,the salt content is 13.27 g·kg-1),glucose concentration 0%,crude oil under 3%.And four kinds of influence factors on the strain D2 oil degradation rate of response surface optimization results show that in the p H=9.0,1%NaCI concentration(that is,the salt content is 13.27 g·kg-1),crude oil concentration and glucose concentration 0%,0.5%crude oil biodegradation rate reached a maximum50.68%;Different p H,Na CI concentration,crude oil concentration and glucose concentration have a significant impact on the biodegradation rate of crude oil.Among them,Na CI concentration and crude oil concentration have a higher reaction sensitivity,while glucose concentration has a slightly lower sensitivity,while p H sensitivity is the lowest.In addition,when p H,Na CI concentration and crude oil concentration increased,the biodegradation rate first increased and then decreased,while when glucose concentration increased,the biodegradation rate gradually decreased.The simulated remediation experiment results of the oil-polluted saline-alkali soil showed that the degradation rates of LD2,LD8 and D2 at 120 d reached 69.42%,71.64%and 80.90%,respectively.In the range of n C13-n C30,n C14 had the highest degradation rate(88.57%),n C19 was the hydrocarbon with the lowest degradation rate(65.65%),n C15,n C16,n C30 and n C24-n C28 had degradation rates of 70-79%,n C13 and n C17-n C23 were degradation rates of 65-70%.In the range of n C12-n C30,n C14 had the highest degradation rate(86.59%),n C20 and n C22 had the lowest degradation rate(67.98%),n C15-n C17 and n C25-n C30 had degradation rates(70-79%),and n C18-n C24 had degradation rates(67-70%).In the range of n C12-n C29,the most biodegradable agent D2 was n C14,with a degradation rate of 92.14%.n C20was the hydrocarbon with the lowest degradation rate,with a value of 77.31%.n C15,n C16,n C24 and n C26-n C29 had degradation rates between 80%and 87%,n C25 and n C17-n C23 between 77%and 80%.It showed that n C14 was the most biodegradable,followed by n C20.Generally speaking,low carbon number(i.e.low molecule number)is easy to be degraded,while high carbon number(i.e.high polymer number)is difficult to be degraded.The high n C20 degradation rate is mainly due to the fact that the main intermediate products generated by polymer degradation are lower than n C20,resulting in the higher measured degradation rate of low carbon hydrocarbon than the actual value. |
PDF Full Text Request