| Urban fringe plays an important role in the development of city and the food service of people.The quality of environment has great influence on the health of people and city sustainable development.Urban fringe heavy metal pollution not only destroys ecology such as animals and crop, but also does harm to human health by food chain.The study of the distribution of heavy metal pollution in urban fringe has great theoretical and practical significance,and it is important for us to make a good plan for land use of urban fringe and to keep human health.Based on complete investigation of urban fringe in Fuzhou, the article choosed vegetable plot,orchard, rice field,woodlot,stream,pool and reservoir in Min hou,Gu lou,Jin an,Ma wei,Cang shan as research objects. The experiment collected 200 soil samples and 102 water samples and determined the content of heavy mental (Zn,Cr,Mn,Pb,Cu,Cd). The spatial distribution of heavy metals in different land use was analyzed from the horizontal and vertical angle. Difference among DTPA extraction or HCl extraction in different land use was compared, so was its correlation with the whole amount.On the basis of overall analysis of the heavy mental distribution in water,the regulation of month dynamic change about the stream which was mainly polluted from domestic sewage was studied,and the correlation with all kinds of heavy mental was studied too.Using national soil environmental quality standard,Fujian soil environmental background values,green food product locality environmental quality standard and edible agricultural products environmental quality standard as soil environmental quality standards, this paper evaluated heavy metal pollution status and potential ecological risk in different land use soils\water by the N.L.Nemerow comprehensive pollution index and potential ecological risk index.The main results were as follows:(1)The study of spatial distribution characteristic of heavy metals in different land use in Fuzhou urban fringe showed that the content and the kind of the heavy metal varied in different land use regions: The contents of heavy metal in vegetable plot and orchard were much higher than that in woodlot and rice field.The contents of heavy metal were proportional to intensity of agricultural production.The contents of heavy metal in four kinds of land use generally showed:vegetable plot>orchard>rice field>woodlot. Contents of the heavy metals in samples from lands around Fuzhou city(Kuaian industrial area in Mawei,Jin shan industrial area,Cheng men industrial area and Fu zhou high-speed line of Shen hai highway,104,324,316 national road and 203,103 provincial road etc )were general higher than those in other areas.(2)The contents of soil heavy metals varied in vertical distribution in different land use. The contents of Zn,Cr,Cu,Cd decreased as soil layer increased in vegetable plot,while the content of Mn was opposite to those, content of Pb was with no significant change in vertical distribution. In orchard, the contents of Zn and Pb were with no significant change in vertical distribution, while the contents of Cr and Mn increased to certain extent as the soil layers increased,with enrichment in 40-60cm,the contents of Cu and Cd were with no similar change law.In woodlot,the average content of Zn and Cu decreased gradually as the soil layers went deeper.The change law showed with 0-20cm>20-40cm>40-60cm,while the content of Cr,Pb showed with 20-40cm>0-20cm>40-60cm.The content of Mn increased as the soil layers went deeper.The content of soil heavy metal was with no similar change law as altitude varied.In rice field, the content of Zn,Cu showed significant enrichment in surface layer. The content of Cr and Mn was lowest in 0-20cm soil layer,the maximum value was in 20-40cm or 40-60cm respectively. The content of Pb,Cd was with no significant change in vertical distribution.(3) The study on the content of soil heavy metal distribution with different distance from road showed: In orchard,the farer distance from the road the lower content of Zn,Mn was in each layer,but there was no significant change in the content of Cr,Pb,Cu,Cd.In rice field, there was no significant change in the content of Zn as the distance changed, but the content of Cr from 100m distance was higher than that which was from 50m and 200m.On 0-20cm layer,the content of Mn decreased as the distance got farther,but it both increased on 20-40cm and 40-60cm as the distance got farther,and the deeper layer was,the farther distance was,the more significant growth trend was.The content of Cu,Pb decreased slightly as the distance got farther. The content of Cd increased as the distance got farther.(4)There were different soil heavy metals distribution among different land use,different elements\different soil depth,different extracting agent.Both the extraction content of soil heavy metals in different land use and extraction rate were consistent with its total content: vegetable plot>orchard>rice field >woodlot, the extraction content of soil heavy metals and extraction rate showed with 0-20cm>20-40cm>40-60cm.Content of DTPA extraction was consistent with that of HCl extraction.And HCl extracting effect was better.(5)The study on correlation between land use and heavy metal elements showed: there was a significantly positive correlation between soil PH and total Mn in vegetable plot and orchard;while there was no significant correlation between soil PH and total Mn in woodlot and ricefield.There were combined pollution (with different heavy metals) by different degree in each land use.There was a quite significant difference between heavy metal extraction and heavy metal total content in different land use:The correlation between heavy metal HCl extraction and heavy metal total content in vegetable plot and orchard were higher than those in woodlot and rice field. There was positive,negative correlation among heavy metal total content,HCl extraction\DTPA extraction to some different degree.(6)The study on water organic pollution showed: Different sampling section showed different distribution law with NH3-N,COD and total P change.The self-purification of the stream water alleviated and weakened water organic pollution which mainly polluted by domestic sewage, while the self-purification did not play an importanr part in improving quality of water environment; water organic pollution in four different land use showed:Pool>stream>industrial area>reservoir.(7)Dynamic study on water heavy metal pollution status showed: There are different levels of different heavy metals pollution.The general result showed: industrial area>stream>pool>reservoir. The self-purification of the stream water did not play an importanr part in the distribution of water heavy metals which enriched from upper to downstream among Qitou river,Wu long river,Min river. There was close relationship between water heavy metals and industrial production, agricultural production, culture,transportation etc. The average content of heavy metal monthly dynamic change in Qitou river showed: the content of Zn,Cr and Cu in wet season were higher than those in dry season while the content of Mn was in opposite distribution.The content of Pb,Cd was with no significant change.(8)According to certain evaluation standards of national soil environmental quality standard,Fujian soil environmental background values, green food product locality environmental quality standard and edible agricultural products locality environmental quality standard,the result was basically identical.The general results of the soil heavy metal pollution status and potential ecological risk in four different land use showed with vegetable plot>orchard>rice field>woodlot;lands located in indusrial area,economic development zone,main traffic line were much more seriously polluted by heavy mentals and with higher potential ecological risk.Besides, the threshold of heavy metals according to Fujian soil environmental background values was lower,so the results showed that the pollution and potential ecological risk was much more severe.(9) In this paper we took environmental quality standards of surface water as evaluation basis and evaluated 9 water quality indexs of main waters in urban fringe of Fuzhou.The result showed that there were organic pollution of heavy metals inordinately in all waters,and Pb,Cr,Cd and COD pollutions were the most outstanding, what was more ,each index of water quality hiberarchy had obvious differences.
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