Increase in platinum group elements in Mexico City as revealed from growth rings of Taxodium mucronatum ten
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Tree rings may be used as indicators of contamination events providing information on the chronology and the elemental composition of the contamination. In this framework, we report PGEs enrichment in growth rings of Taxodium mucronatum ten for trees growing in the central area of Mexico City as compared to trees growing in a non-urban environment. Concentrations of PGE were determined by ICP-MS analysis on microwave-digested tree rings. The element found in higher concentrations was Pd (1.13–87.98 μg kg−1), followed by Rh (0.28–36.81 μg kg−1) and Pt (0.106–7.21 μg kg−1). The concentration trends of PGEs in the tree-ring sequences from the urban area presented significant correlation values when comparing between trees (r between 0.618 and 0.98, P < 0.025) and between elements within individual trees (r between 0.76 and 0.994, P < 0.01). Furthermore, a clear increase was observed for rings after 1997, with enrichment of up to 60 times the mean concentration found for the sequence from the non-urban area and up to 40 times the mean concentration for the pre-1991 period in the urban trees. These results also demonstrate the feasibility of applying T. mucronatum ten to be used as a bioindicator of the increase in PGE in urban environments.
KeywordsPlatinum group elements Biomonitoring Dendrochronology Mexico City
We thank DGAPA (Dirección General de Asuntos del Personal Académico, UNAM) for the financial support of this study (Projects IN106113 and IN101612). Support from José Villanueva (Laboratorio Nacional de Dendrocronología, INIFAP), for helping with both dendrochronologies, is gratefully acknowledged. The authorities of Bosque de Chapultepec are thanked for granting sampling permission.
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