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Generally,compositions and sources of the heavy metals of the precipitation samples were studied by means of filtered samples.This method has some shortcomings due to dissolution abilities of different metals are different,which naturally maybe induce incorrect or inappropriate final conclusions.Therefore,in this study,both filtered and unfiltered precipitation samples of two cities-Lhasa and Chengdu in China were studied and compared.Chengdu is a relatively heavily air polluted city compared to Lhasa-a typical tourism city.The results indicated that: Firstly,Enrichment factors(EF)of most heavy metals(e.g.Cu,Zn,Ni)and even some major elements(e.g.Na and Mg)of filtered samples of these two cities were much higher than those of unfiltered samples,reflecting mainly these metals were more easily dissolved into fresh water than the reference element of Al.Meanwhile,EF values of several heavy metals(e.g.Co,Ni and Cu)of filtered samples of Lhasa were even higher than those of Chengdu,which is against the general pollution status of these two cities.Furthermore,Principal components analysis results for the studied elements of filtered and unfiltered samples were also different.Some heavy metals previously fall into anthropogenic sources in filtered samples were classified into natural dust sources in unfiltered samples.Normally,unfiltered precipitation samples include almost all the information of atmospheric environment.Additionally,filtering process will produce some potential contamination inevitably.Therefore,it is suggested that unfiltered precipitation samples can reflect the atmospheric environment of a given area more realistic than that of filtered samples,which can avoid the potential influence of different abilities to dissolve of different elements at large extent.Finally,it is suggested in this research to use unfiltered precipitation samples for the related studies in the future.