| The Yellow River Delta is a typical estuarine and coastal wetland ecosystem,as well as one of the important oil and gas exploration area in China.Oil pollution is inevitably in the process of oil exploitation,processing and transportation,which has a negative impact on the surrounding agricultural production and human life.With the rapid development of economy and the intensification of human activities in estuary area,pollution of oil and heavy metal are becoming more and more serious in the study area.As wetland plants,Phragmites australis and Suaeda salsa have certain enrichment capacity for heavy metals.Therefore,the study of the impact of oil pollution on the accumulation of heavy metals in wetland plants will provide scientific basis and theoretical value for the bioremediation of oil-heavy metal complex pollution in the Yellow River Delta.In this thesis,through filed sampling and the analysis of heavy metals in soil,total petroleum hydrocarbons?TPH?,polycyclic aromatic hydrocarbons?PAHs?and wetland plants?Phragmites australis,Suaeda salsa?rhizomes and leaves,the pollution status of heavy metals?Pb,Mn,Fe,Co,Ni,Zn?and petroleum hydrocarbons in the study area were explored,and the source analysis of PAHs was carried out.In addition,by studying the effect of TPH on the accumulation and migration of heavy metals in plants,the influence of oil pollutants in different oil fields on the accumulation of heavy metals in plants were further discussed.Under the same concentration of oil pollution,comparing the enrichment and migration coefficients of heavy metals of Phragmites australis and Suaeda salsa to analyze their tolerance to oil pollution,and to explore which plant is more suitable to enrich heavy metals in oil pollution areas.The results showed that:?It shows a lower degree of surface petroleum hydrocarbons pollution in the study area.The concentration of Pb,Mn,Fe,Co,Ni and Zn in the surface layer was lower than the first-class national soil quality standard and the background value of Shandong soil.The main vertical direction of Pb,Mn,Fe,Co and Zn in oil fields reached the maximum concentration of heavy metals in 10—20 cm soil layer,while the vertical variation of heavy metals in non-oil well area was irregular.This may be due to the accumulation of heavy metals in shallow layers because of the role of oil pollutants.As an important component of oil pollutants,PAHs showed a medium pollution level in China and were mainly derived from mixed sources of petroleum pollution and combustion.?Phragmites australis:The distribution of essential elements Zn and Mn was more balanced in the above-ground and underground parts,while the Pb,Fe,Co and Ni was mainly concentrated in the root but less in the stem and leaf.In old and new oil fields,the overall enrichment coefficients of heavy metals in Phragmites australis showed a trend of first increasing,then decreasing and finally increasing with the increase of TPH concentration,which was related to the different effects of TPH on plants at different stages.In compared with the control,TPH can promote the migration of Zn and Mn in the range of concentration,while for the other four heavy metals,the migration was promoted by low TPH concentration(<400?g·g-1)and inhibited by high TPH concentration.Suaeda salsa:Essential element Zn mainly distributed in the above-ground parts,while the other heavy metals mainly distributed in roots.Of all heavy metals,Suaeda salsa showed strong enrichment ability at low concentration,and gradually decreased with the increase of TPH.This may be due to the biger influence of high TPH on the root of Suaeda salsa.Under oil pollution,the migration ability of Zn in Suaeda salsa was better,which was greater than 1 and larger than the control area,while for the other five heavy metals the migration ability was poor.The root of Suaeda salsa was more sensitive to TPH.High TPH concentration was not conducive to the absorption of heavy metals in root.However,compared with Phragmites australis,Suaeda salsa had a larger accumulation and migration coefficient of Pb,Fe,Co,Ni and Zn,which indicated that Suaeda salsa had better migration and enrichment characteristics of heavy metals than Phragmites australis in oil filed.Within the concentration range studied,Suaeda salsa has better tolerance to oil pollutants.Previous studies on the effects of petroleum hydrocarbons on plants mainly used the method of simulation experiments,and it mainly focused on its physiological characteristics and activities of enzymes in vivo.Few studies have been conducted on the influence of primary environment on the enrichment and migration of heavy metals.In this thesis,the heavy metal enrichment of Suaeda salsa and Phragmites australis under oil pollution was investigated by field sampling.Different from simulation experiments,although the actual concentration range of petroleum hydrocarbons is narrow,it is generally helpful to judge the actual situation.It is expected to provide a theoretical basis for the bioremediation of oil-heavy metal complex pollution. |
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