| With the acceleration of urbanization and industrialization,heavy metals pollution of the park environment presented more and more seriously for it is one of the important areas for the urban environment.Heavy metal pollution in the urban park not only has significant impact on the substances cycle among atmosphere,biosphere and hydrosphere,but also poses a potential health risk for human beings and surrounding ecosystems.This paper studied the pollution and migration characteristics and source apportionment of heavy metals in the soil,dust and plant of 32 parks in Xiamen,China,and further developed the quantitative migration model of heavy metals among the dust,soil and plant.This research is helpful for understanding heavy metals pollution sources and migration mechanism of the park environment,and has a much important scientific significance for the knowledge of environment chemical pollution,environmental quality and environment protection strategy,and can also support base data and scientific foundation for the modern planning and environmental pollution prevention in urban areas.The main conclusions of this thesis are revealed as follows:?1?The average values of heavy metals(mg·kg-1,summer/winter)in park dust in Xiamen,China were found to be in descending order as follows:Zn?911/1301?>Ba?906/887?>Cu?259/258?>Pb?202/134?>Cr?143/150?>Ni?52.0/52.4?>V?43.6/46.2?>Co?33.9/36.6?>As?12.0/11.3?>Cd?1.33/1.18?.Methods of comparing with their corresponding soil background values,enrichment factor?EF?,scanning electron microscope?SEM?,energy spectrum analysis?EDX?were used to analysis pollution levels of 10 heavy metals.The results showed that Cu,Pb,Cd,Ni,Cr,Co,As,and Ba in park dusts were mainly influenced by anthropogenic sources to some degree,while V was mainly originated from natural sources.Principle component analysis and multiple linear regression?PCA-MLR?found that heavy metals in park dusts were affected by traffic emissions,construction,fugitive dust,coal combustion and industrial emissions and soil dust.The Trajectory Model and the Pb isotope tracing results were in good agreement with the PCA-MLR analysis.The gastric-extractable fractions of Cu,Zn,Cd,and Pb by the SBRC method were significantly correlated with acid extractable fraction?F1?,the reducible fraction?F2?,the oxidizable fraction?F3?by the modified BCR method?p?0.01 or 0.05?,and illustrated that their gastric-extractable fractions were originated from F1,F2 and F3.The bioavailability index?K?indicated that they were classified as potential or bioavailable elements and threatened to local ecosystems and human health.The major contributing elements of Pb,Cr,and As as health risks mainly derive from coal combustion,traffic and construction dusts.?2?The average values of heavy metals(mg·kg-1)in park soil in Xiamen,China were found to be in descending order as follows:Mn?433?>Ba?340?>Zn?92.2?>Pb?49.5?>V?41.5?>Cu?19.8?>Cr?17.6?>As?11.8?>Ni?7.90?>Co?4.98?>Cd?0.24?.Cu,Zn,Cd,Pb,and As in parks soils were seriously impacted by human activities based on the methods of comparison with their corresponding soil background values and the class standard limits and calculating EFs.PCA-MLR was applied for source apportionment and results revealed that anthropogenic sources were the dominant contributors to the bioavailable fractions of most heavy metals,excluding Cr and Ni.However,55.1%-100%of the anthropogenic sources still contributed to the residual fractions of Cd,Pb,As,Ba,and Mn,which was confirmed by Pb speciation isotopes,SEM,EDX,and EFs.These results imply that anthropogenic sources influence both the bioavailable and residual fractions,but more significantly impact the bioavailable fraction.Correlations analysis revealed that the F1,F2 and F3 fractions contributed to the gastric-extractable fractions of Cu,Zn,Cd,and Pb by the SBRC method,and results of K?mean values>0.2?indicated that they were classified as potential or bioavailable elements and threatened to local ecosystems and human health.The major contributing elements of Pb,Cr,and As as health risks mainly originate from coal combustion,soil parent materials and pesticides and fertilizers.?3?The average values of heavy metals(mg·kg-1,summer/winter)in leaves of Ficus spp.from parks in Xiamen,China were found to be in descending order as follows:Ba?42.0/43.2?>Mn?36.9/36.6?>Zn?15.2/13.5?>Cu?4.13/3.66?>Pb?0.38/0.50?>Ni?0.34/0.17?>Co?0.10/0.08?>V?0.06/0.07??As?0.03/0.08?>Cd?0.01/0.02?.The average values of heavy metals(mg·kg-1,summer/winter)in leaves of Schefflera from parks in Xiamen,China were found to be in descending order as follows:Mn?187/156??Zn?127/85.8?>Ba?93.8/77.0?>Cu?3.64/3.77?>Pb?0.76/0.54?>Cd?0.29/0.18??Co?0.25/0.16??Ni?0.23/0.24?>As?0.08/0.06??V?0.07/0.05?.The Cd,Zn,and Mn concentrations in the leaves of Scheffera were much higher than those of Ficus spp.leaves.The correlation analysis,SEM,PCA-MLR and Pb isotopes were used to analyze the sources of heavy metals in plants in Xiamen parks of China.The results showed that the coal burning deposition,fertilizer,construction,traffic emissions,and soil parent materials were the main sources of heavy metals in the leaves of Ficus spp.and Scheffera.?4?The quantitative migration model of heavy metals among dust-soil-plant was build up by using PCA-MLR.Soil parameters of pH,TC,EC and heavy metals speciation in soils were the impact factors of migration between soil and plant for Cu,Ba,Pb in Ficus spp.and Cu,As,Cd in Scheffera.The migration of Ni,Cu,Pb between Ficus spp.and dust were affected by heavy metals speciation in dust.The migration of Co,Cu,Pb,Cd between Scheffera and dust were affected by heavy metals speciation in dust.The prediction of Cu was the best than that of other heavy metals,and they both reached significant levels?p<0.01,R2=0.55-0.84?for Ficus spp.and Scheffera among dust-soil-plant of park system in Xiamen,China. |
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