| Urban soil is one of the most important resources to the human.it is also an important part of the ecosystem.Due to the development of social economy,the accelerating urbanization and human activities makes the variety of heavy metal elements in urban soil and the surface sediment which pose a threat to urban ecological system and human health.A total of 181 samples were collected from surface soil in the main urban area of Yongkang city(the Hardware City of China),and 37 samples were collected from surface sediment of yongkang river,the contents of 9 heavy metals including Ti?Cr?Mn?Co?Ni?Cu?Zn?As and Pb were determined.Use the index of single-factor pollution index?Nemerow Pollution Index?Sediment quality guidelines?enrichment factor and Hakanson risks index to analyst the characteristic of heavy metal pollution and potential ecological risks.Multivariate analysis and geostatistics were applied to examine the spatial distributions of heavy metals in yongkang,The results showed :1)The average contents of heavy metals in the surface soil were as follow: Ti(5677)>Mn(513)>Cr(121)>Zn(95)>Pb(40)>Ni(23)>Cu(21)>Co(10)>As(6)mg·kg-1.Obvious differences in contents between various points,The Ti and Ni were belong to medium variationsl,the other elements belong to strong mutation.The average contents of heavy metals in the surface sediment of yongkang river were as follow: Ti(4040)>Mn(755)>Zn(414)>Cr(201)>Cu(95)>Pb(35)>Ni(47)>As(8)>Co(7)mg·kg-1.The Fnrichment factor showed that the heavy metals had different degree of enrichment phenomenon in different places,especially the Ni?Cu and Zn.2)The Single-factor pollution index indicated that the pollution degree of heavy metals in surface soil of Yongkang was in low level.Most of the metals were in potential pollution except Cr,which was in light pollution level.The average of Single-factor pollution index were as follow: Cr(2.58)>Ni(1.82)>Co(1.42)>Ti(1.39)>Mn(1.36)>Cu(1.36)>Zn(1.31)>Pb(1.14)>As(1.02).The pollution in surface sediment was more serious than that in surface soil.The pollution of Ti?Mn?Co?As was light,and the pollution of Cr?Ni?Cu?Zn was serious.The average of Single-factor pollution index were as follow: Zn(5.74)>Cu(5.28)>Cr(4.43)> Ni(3.80)>Pb(2.14)>Mn(2.00)>As(1.27)>Co(1.01)>Ti(0.99).3)The Nemerow Pollution Index showed that the surface soil in Yongkang is generally in moderate pollution.Industrial land and park were serious pollution,The other 6 types of land use were in moderate pollution level.The averages of Nemerow Pollution Index in different places were asfollow: Industrial land(3.47)> park(2.81)> abiding place(2.81)>other land(2.33)>forest(2.19)>farmland(2.09)> Municipal Land(1.93)> plantation(1.93).4)The average Hakanson risk index of surface sediments in Yongkang river is 91.50,which was higher than the index of surface soil(48.05),most of the samples were in the low ecological risk,but some places were in medium risk.The averages of Hakanson risk index in different places were as follow: Industrial land(65.12)> park(56.39)> abiding place(55.31)> other land(47.88)>Municipal Land(47.87)>farmland(41.37)>foreast(40.43)> plantation(38.20).The RI values of heavy metals in surface sediments of each place were as fallow: the first tributary(108.70)> Midstream(104.14)>downstream(99.31)> the second tributary(86.82)> upwnstream(71.14)> the third tributary(51.32).5)The high value areas of Ti?Cr?Ni?Cu?Co and As were mainly concentrated in the vicinity of the industrial district.The distribution map of Zn?Pb were same as the urban road map.In the surface sediments,the pollution index of Ti?Mn?Co?Cu?As and Pb were higher in master stream than the index of tributarys,In contrast Cr?Ni and Zn were Serious pollution in tributarys.6)From the analysis of the correlation between landscape pattern and ecological risk of heavy metals in the soil,with the increasing of interference intensity of human activities,the Hakanson risk index of Cr?Ni and Cu will be increased.7)Sources of heavy metals in sediments from the surface soil and surface river in Yongkang is mainly divided into three categories: Cr,Ni,Cu,Co,As mainly accumulated by industrial production,Zn and Pb elements are mainly affected by the accumulation ? transportation activities;Ti,Mn accumulated from metallurgical industry and manufacturing activities,but also influenced by the soil.To research the pollution situation and distribution characteristics of soil and surface sediment in Yongkang city,to explore the relationship between landuse and heavy metal pollution indexs,which is of guiding significance for the prevention and control of heavy metal pollution and rational development of land resources. |
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