Distribution and sources of bioaccumulative air pollutants at Mezquital Valley, Mexico, as reflected by the atmospheric plant <i>Tillandsia recurvata</i> L.

• Main Authors: A. Zambrano García, C. Medina Coyotzin, A. Rojas Amaro, D. López Veneroni, L. Chang Martínez, G. Sosa Iglesias
• Format: Article
• Language: English
• Published: Copernicus Publications 2009-09-01
• Series: Atmospheric Chemistry and Physics
• Online Access: http://www.atmos-chem-phys.net/9/6479/2009/acp-9-6479-2009.pdf

Mezquital Valley (MV), a Mexican wastewater-based agricultural and industrial region, is a "hot spot" of regulated air pollutants emissions, but the concurrent unregulated ones, like hazardous metals and polycyclic aromatic hydrocarbons (PAH), remain undocumented. A biomonitoring survey with the epiphytic <i>Tillandsia recurvata</i> was conducted there to detect spatial patterns and potential sources of 20 airborne elements and 15 PAH. The natural &delta;¹³C and &delta;¹⁵N ratios of this plant helped in source identification. The regional mean concentration of most elements was two (Cr) to over 40 times (Ni, Pb, V) higher than reported for <i>Tillandsia</i> in other countries. Eleven elements, pyrene and chrysene had 18–214% higher mean concentration at the industrial south than at the agricultural north of MV. The total quantified PAH (mean, 572 ng g^&minus;1; range, 143–2568) were composed by medium (65%, phenanthrene to chrysene), low (28%, naphthalene to fluorene) and high molecular weight compounds (7%, Benzo(<i>b</i>)fluoranthene to indeno(1,2,3-<i>cd</i>)pyrene). The &delta;¹³C (mean, &minus;14.6&permil;; range, &minus;15.7&permil; to &minus;13.7&permil;) was consistently lower than &minus;15&permil; near the major petroleum combustion sources. The &delta;¹⁵N (mean, &minus;3.0&permil;; range, &minus;9.9&permil; to 3.3&permil;) varied from positive at agriculture/industrial areas to negative at rural sites. Factor analysis provided a five-factor solution for 74% of the data variance: 1) crustal rocks, 39.5% (Al, Ba, Cu, Fe, Sr, Ti); 2) soils, 11.3%, contrasting contributions from natural (Mg, Mn, Zn) and saline agriculture soils (Na); 3) cement production and fossil fuel combustion, 9.8% (Ca, Ni, V, chrysene, pyrene); 4) probable agricultural biomass burning, 8.1% (K and benzo(<i>g,h,i</i>)perylene), and 5) agriculture with wastewater, 5.2% (&delta;¹⁵N and P). These results indicated high deposition of bioaccumulative air pollutants at MV, especially at the industrial area. Since <i>T. recurvata</i> reflected the regional differences in exposition, it is recommended as a biomonitor for comparisons within and among countries where it is distributed: southern USA to Argentina.