HR: 09:15h
AN: A41E-06    [Abstracts]
TI: Regional Distribution of Metals and C and N Stable Isotopes in the Epiphytic Ball Moss (Tillandsia Recurvata) at the Mezquital Valley, Hidalgo State
AU: Zambrano-Garcia, A
EM: azambran@imp.mx
AF: Instituto Mexicano del Petróleo., Eje Central Lázaro Cárdenas 152, México, DF 07730, Mexico
AU: * López-Veneroni, D
EM: dglopez@imp.mx
AF: Instituto Mexicano del Petróleo., Eje Central Lázaro Cárdenas 152, México, DF 07730, Mexico
AU: Rojas, A
EM: arojas@imp.mx
AF: Instituto Mexicano del Petróleo., Eje Central Lázaro Cárdenas 152, México, DF 07730, Mexico
AU: Torres, A
EM: atorress@imp.mx
AF: Instituto Mexicano del Petróleo., Eje Central Lázaro Cárdenas 152, México, DF 07730, Mexico
AU: Sosa, G
EM: gsosa@imp.mx
AF: Instituto Mexicano del Petróleo., Eje Central Lázaro Cárdenas 152, México, DF 07730, Mexico
AB: As a part of the MILAGRO Field Campaign 2006, the influence of anthropogenic sources to metal air pollution in the Mezquital Valley, Hidalgo State, was explored by biomonitoring techniques. This valley is a major industrial- agriculture area located in central Mexico. An oil refinery, an electrical power plant, several cement plants with open-pit mines, as well as intensive wastewater-based agricultural areas, all within a 50 km radius, are some of the most important local sources of particulate air pollution. The concentrations of 25 metals and elements were determined by ICP-AES (EPA 610C method) for triplicate composite samples of the "ball moss" (T. recurvata ) collected at 50 sites. In addition, the ratios of two stable isotopes ((¹³C/¹²C and ¹⁵N/¹⁴N) were determined by continuous-flow isotope-ratio mass spectrometry in order to assess their potential as tracers for industrial emissions. Preliminary results showed high to very high average contents of several metals in the biomonitor compared to values from similar studies in other world regions, indicating a high degree of local air pollution. In contrast, most samples had Ag, As, Be, Se and Tl contents below detection levels (DL = 0.05 mg/kg of sample dry weight) indicating low levels of pollution by these metals. Metals such as Al, Ba, Ca, Fe, Li, Mo, Ni, Sr, Ti, V and Zn concentrated the most at the South portion of the valley, where the Tepeji-Tula-Apaxco industrial corridor is located. A transect parallel to the along-wind direction (N-S) showed a higher concentration of metals farther away from the sources relative to a cross-wind transect, which is consistent with the eolian transport of metal-enriched particles. Regional distribution maps of metals in the biomonitor showed that Al, Ba, Fe, Mo, Ni, Sr, Ti and V had higher levels at the industrial sampling sites; whereas K, Na and P were more abundant near to agriculture areas. Vanadium, a common element of crude oil, reflected better the influence from the local oil refinery and the oil- fueled power plant. Two distinct Ni:V scatterplot trends suggest that there are two main petrogenic emission sources in the region. Calcium and, to some extent, Mg were higher near the mining areas and a calcium carbonate factory. Lead had a diffuse distribution, probably related to former gasoline vehicle exhaust emissions, rather than to current emissions. Antimony was more abundant at sites far from agriculture and industrial areas, which suggests a natural origin (rocks or soils). The spatial distribution of stable isotopes also showed distinct patterns near the industrial sources with relatively ¹³C -depleted and ¹⁵N -enriched values near the oil refinery and the electrical power plant. Although it is not yet possible to provide quantitative estimates for emission contributions per source type, biomonitoring with T. recurvata provided for the first time a clear picture of the relative deposition patterns for several airborne metals in the Mezquital Valley.
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0365 Troposphere: composition and chemistry
DE: 0368 Troposphere: constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly