| To study the pollution characteristics of xi'an ancient town all kinds of medium and its possible environmental risks, provide scientific basis for xi'an urban ecological pollution. Collecting the corresponding points of soil, water, dust, plants in xi'an ancient city wall district by random sampling, through determination of the heavy metal content in the sample, accumulation of pollution situation of medium in xi'an ancient city can be acquired, applying ecological risk index method of potential ecological harm evaluation and using the method of risk assessment of the environmental protection agency issued evaluate its activities in the people's health risks. The results show that:(1) Urban soil heavy metal Pb and Co is one of the main regional ecological risk factor, Pb and Co in the medium level of risk; The average total potential ecological risk evaluation index RI is 52.67, belong to medium risk. Exposure levels of Sr in eight kinds of heavy metal is the largest, As, Cr, Pb, Co for children have some non-cancer health risk, Cr, Co, As, Ni cancer risk can be ignored, belong to low risk. By correlation analysis and principal component analysis of soil heavy metals can be concluded that the As, Cr and Ni is affected by the same sources, Cu, Pb, Zn is affected by the same sources.(2) The As, Cu, Pb in dust is the ancient city of xi'an city's main ecological risk factor, Pb in strong risk level, Cu and As in the medium level of risk; The average total potential ecological risk evaluation index RI is 64.26, belong to medium risk. Urban dust health risk assessment, in exposure levels in three kinds of exposure pathways, HI of Cr in the ancient city surface dust is the biggest, As, Cr, Pb, Cu for children have some non-cancer health risk. Co, Ni, Cr, As will not cause cancer risk to urban residents. Cu and Ni, As and Zn, Ti and V are affected by the same sources more likely.(3) The average content of Cr, Pb, Zn in Buxus sinica var. parvifolia M. Cheng leaves are greater than the Sophora japonica Linn, the average content of Ni in Sophora japonica Linn leaf is greater than Buxus sinica var. parvifolia M. Cheng, Ni more easily in the enrichment of the Sophora japonica Linn, The concentration of Cr, Pb, Zn in Buxus sinica var. parvifolia M. Cheng is more easy. The enrichment coefficient of Ni and Zn is greater than 1. Cr and Pb enrichment coefficient is less than 1. The correlation coefficient of Pb and Cd in The Sophora japonica Linn tree content is 0.56, significantly related; the correlation coefficient of Pb and Zn in Buxus sinica var. parvifolia M. Cheng leaves content is 0.87, highly correlated.(4) The risk degree of Cr, Cd, Pb, Cu does not exceed the recommended standards of the international commission on radiation protection risk degree of 5.00 × 10-5a-1, won't cause harm to human body health.Drinking water of heavy metal pollutants in the health hazards caused by carcinogens Cd and Cr is far higher than the carcinogen caused the health hazards of Pb and Cu.(5) Cu and Pb in soil and dust exists significant correlation, and Cr, Niand Zn in soil and dust, there is no significant correlation. Cu and Pb source could be the same like the urban traffic pollution in the two kinds of medium, Cr, Ni, Zn sources of these elements in the two kinds of medium, there is a big difference between source is relatively complex, the Zn dust and Pb content in Buxus sinica var. parvifolia M. Cheng leaf is extremely significant correlation (p?0.01), the correlation coefficient is 0.46, indicating that Pb content in the Buxus sinica var. parvifolia M. Cheng leaves increases with the increase of the content of Zn in dust, dust in the Zn plant absorption of Pb synergy, to produce the composite effect of increasing the absorption of Pb. |
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