| Based on the heavy metal pollution of Qingdao's coastline,this study used the Nemerow index method,potential ecological risk index method,and geo-accumulation index method to determine the composition and content of heavy metals in the soil of Qingdao's coastline.The evaluation and analysis of heavy metal pollution found that the soil pollution of Qingdao's coastline is relatively serious and there is a greater ecological risk.The analysis shows that the most important heavy metal causing this pollution is Cd.Therefore,the sample plots containing heavy metal Cd were re-investigated.,Conduct field surveys and statistics on plants in the sample plots,analyze,compare and summarize the characteristics of soil heavy metal Cd pollution concentration in the coastal coastline of Qingdao and the diversity pattern of typical natural plant communities;through the quantitative determination of soil heavy metal Cd content and soil salinity,analysis The influence of soil salinity characteristics and heavy metal Cd content on the distribution of plant community types in the study area.It is preliminarily determined that the heavy metal Cd content of Qingdao's coastline has an extremely significant impact on the distribution of community types;through the study of natural plant communities in the study area,research and analysis Community structure characteristics of three typical natural plant communities of Phragmites australis,Suaeda salsa,and Setaria viridis under different levels of heavy metal Cd pollution,and the growth of plant communities under different levels of heavy metal Cd pollution There are significant differences in order to screen out heavy metal-tolerant plants suitable for the heavy metal Cd-contaminated shoreline soil environment of Qingdao City and potential plants that can repair heavy metal Cd-contaminated soil,and finally summarize and screen the nature suitable for the heavy metal Cd-contaminated shoreline soil in Qingdao City.Plant community model,and finally ecological landscape plant restoration.It is expected to provide certain theoretical guidance and basis for the ecological restoration of heavy metal Cd contaminated coastal soils:(1)Through Nemerow index method,potential ecological risk index method,and geo-accumulation index method,it can be concluded that the coastline soil of Qingdao City has a relatively large ecological risk and serious pollution.The most important heavy metal causing this situation is Cd.(2)Conduct survey and statistics of natural plant communities in 47 plots polluted by heavy metals on the coastline of Qingdao City,and count the names,heights,number of plants,etc.of various plants in the plots.A total of 82 species of plants belonging to27 families and 66 genera were recorded.Among them,Compositae and Gramineae have obvious advantages in the survey site.(3)The three typical natural plant communities of Phragmites communis,Suaeda salsa community and Setaria salsa community showed that the index analysis of plant species diversity showed that the largest Shannon-Wiener diversity index is Phragmites communis(1.809),which is similar to that of Suaeda salsa.The difference between the community and the setaria community is not significant(P>0.05);the highest Patrick's richness index is the setaria community(1.008),which is not significantly different from the reed community and the setaria community(P>0.05);the Pielou evenness index reed community>salt soil Suaeda salsa community> Setaria viridis community,respectively 0.918,0.911,0.880,the difference between the three communities is not significant(P>0.05);the highest in the Simpson dominance index is the setaria community,the Suaeda salsa community is the second,and Phragmites australis The community was the lowest,0.811,0.775,0.769,and the difference between the three communities was also not significant(P>0.05).(4)According to data analysis,the average total salt content of the heavy metal Cd pollution area of Qingdao coastline is 0.180%,the average pH is 7.528,and the average heavy metal Cd content is 16.004 mg/kg.According to the difference test results,when the total salt content is controlled within the average value of 0.180%(±5%)and the pH value is controlled within the average value of 7.528(±5%),the content of heavy metal Cd is the influence on the type of plant community under this condition.Main factors(P<0.01).(5)When ensuring that the total salt content and pH value of the selected sample plots are both at the average level,it is judged by the change of its diversity index that the three typical natural plant communities in this study have shown a certain tolerance to heavy metal Cd on the site.,Its tolerance to different pollution levels is measured according to the plant community diversity index.When the heavy metal Cd concentration is low,when the reference heavy metal Cd content is 6.89?Cd<11mg/kg,each index of the plant community is represented by a setaria community> Phragmites communis> Suaeda salsa community;and with the increase of heavy metal Cd content and the measurement value range is 15.2?Cd<25.4mg/kg,the dominance of the Suaeda salsa community gradually manifests.At this time,the various indicators of the plant community It is shown as Suaeda salsa community>Reed community>Setaria community;when the measurement value range is 25.4?Cd<46.5mg/kg,only the reed community remains among all the measured plant communities,and the reed community shows an absolute Advantage.It can be seen that the Phragmites australis community can show good tolerance to heavy metal Cd in both light and heavy heavy metal Cd pollution.The Suaeda salsa community and the Setaria sylvestris community are in the middle zone III and II heavy metal Cd respectively.It shows advantages in contaminated soil environment and is more suitable for growth in this type of environment.(6)Through the plant investigation and study of the heavy metal Cd pollution coastline research area of Qingdao City and the summary analysis of plant community diversity indicators,referring to the principle of plant configuration,according to the species dominance and herb importance value,etc.,screen out suitable for different heavy metal Cd pollution A total of 15 plant species are classified.Combining the environment with different heavy metal Cd pollution levels,the landscape ecological plant configuration design mode was studied.A total of four types of five plant configuration modes were designed for the environment with four different heavy metal Cd pollution levels. |
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