Study On Spatial Distribution Of Metal Elements In Jinhua Urban Dust Based On Multifractal

At present,in the study of the urban environment,mainly in water,soil and urban atmospheric particles as the object of study.Urban dust as a carrier of the urban environment can indicate specific environmental information,which has many advantages such as strong representation,relatively convenient sampling,large spatial distribution range and close contact with non-point source pollution.Due to the influence of human activities such as industrial production,transportation,and urban construction,many heavy metal elements are constantly enriched in urban dust and have become one of the important pollutants in urban ecological environment pollution.The urban dust will not only cause urban environmental pollution,but also endanger the health of urban residents,and reduce people's lives and living quality.Therefore,it is very important to study the spatial distribution of heavy metals in urban dust and its influencing factors.The dust research on the city of heavy metal elements by domestic and foreign scholars,including the following aspects:the content,occurrence patterns,source analysis,spatial distribution and pollution evaluation of heavy metal elements.The study on spatial distribution of dust heavy metals mainly focuses on cities,and researches its spatial distribution characteristics on the "punctuation" "linear""surfaceshape" and affecting factors.In the previous work,the spatial statistical method is usually used to study the spatial variation of dust metal elements,and the probability distribution of dust metal elements is studied by means of probability distribution chart or frequency distribution histogram.The multifractal method can integrate these two functions into one.This method not only considers the spatial variability and correlation of the geochemical field,but also has a good effect on the enhancing local variability of the geochemical field and anomaly extraction.However,it is still rare to apply multifractal method to urban dust research.Revealing the distribution characteristics of chemical elements in the urban dust and extracting abnormal areas have a high reference value for urban environmental protection.In this paper,Jinhua urban area within the Second Ring is selected as the research area,and the urban dust in Jinhua city is taken as the research object.The contents of Pb,Zn,Cu,Cr,Ni and other heavy metals in the samples were measured,and the contents of Ca element that is influenced by human activities was also measured.Then,the spatial distribution of the above elements is analyzed,and the identification and extraction of the spatial anomalies are carried out by using the method of multifractal.Finally,the relationship between singularity index and traffic,business factors,industrial factors are analyzed emphatically.Through the above study,the page gets the following main conclusions:(1)The paper calculates the fractal dimension of Pb,Zn,Cu,Cr,Ni,Ca and other elements in Jinhua city dust in four different functional areas.By comparing the fractal dimensions of the different functional regions,it is found that the minimum values of the fractal dimensions(D)of Pb,Zn,Cu,Ni,and Cr are all in the industrial area except for the Ca element,indicating that the degree of uniformity of the five heavy metal elements in the industrial area is poor.The possibility of enrichment in the industrial area is greater.(2)The spatial distribution of dust heavy metals in Jinhua urban area was analyzed by using multifractal spectrum.The results show that the multifractal spectrum function curves of the six chemical elements studied in this paper are all upper convex asymmetric image.Among them,the shapes of Pb,Cu,Ni and Zn elements multifractal spectrum are all right hooked,indicating that the proportion of low content of heavy metal elements is high.While the shapes of the multifractal spectrum of Ca and Cr elements are left hooked,and left endpoint is higher than right endpoint,which indicates that the proportion of high content of Ca and Cr is larger.(3)The singularity index of the six elements studied were developed and calculated,and the geochemical anomalies of six elements such as Pb,Zn,Cu,Cr,Ni and Ca were extracted.The main pollution areas of heavy metals in Jinhua city include:Jiangnan core business circle,the trade and industry city in the northwest corner of Wucheng District-West Bus Station and the Jinhua City Industrial Park in the southwest corner of Wucheng District.The frequent human activities,industrial development and convenient transportation in these regions indicate that urban dust metals may be affected by human activities.(4)The paper uses the correlation analysis method to analyze the relationship between singularity index and influencing factors such as transportation,industry,and commerce.The results show that there is a negative correlation between the singularity index of metal elements in urban dust and the density of road network,which indicates that traffic is an important factor affecting the distribution of dust metal content in Jinhua city.The singularity index of dust metal elements can be used to indicate the traffic pollution situation;The relationship between Jinhua urban dust metal singularity index and the distances from sampling points to the industrial area center,or to the the commercial center are positively correlated.The distances are closer,the singularity index of the metal in dust is lower.we can see that the industrial and commercial factors have a great influence on the content of metal elements in the dust of Jinhua city.