The first report on oxidant-induced plant damage in the Valley of Mexico was presented over 30 years ago. Ozone is known to occur in the Mexico City Metropolitan Area and elsewhere as the cause of chlorotic mottling on pine needles that are 2 years old or older as observed in 1976 on Pinus hartwegii and Pinus leiophylla. Visible evidences for the negative effects of ozone on the vegetation of central Mexico include foliar injury expressed as chlorotic mottling and premature defoliation on pines, a general decline of sacred fir, visible symptoms on native forest broadleaved species (e.g. Mexican black cherry). Recent investigations have also indicated that indirect effects are occurring such as limited root colonization by symbiotic fungi on ozone-damaged P. hartwegii trees and a negative influence of the pollutant on the natural regeneration of this species. The negative ozone-induced effects on the vegetation will most likely continue to increase. Ozone induced symptoms, poor tree regeneration and limited root colonization by mycorrhiza fungi observed in the valley of Mexico.

The biomass from Abies religiosa was conditioned and characterized. The adsorption kinetic data indicated sorbate-adsorbent interaction by chemical bonds. The maximum adsorption capacity of the biomass is four times higher for U(VI) (44.7 ± 0.3 mg g⁻¹) than La(III) (12.7 ± 0.2 mg g⁻¹). The pHₑq tends to the point of zero charge of the biomass. These adsorption capacities decreased as both the biomass dosage and ionic strength increased. The adsorption is a spontaneous and exothermic process. Adsorption may be due to the bonding of the metal ions to hydroxyl and carbonyl groups of the biomass. The fluorescence spectra of the U(VI) biomass reveal indirectly the presence of uranyl ions and it suggests an energy transfer from the uranyl to the biomass forming a bond of ionic character. Moreover, the unusual fluorescence of the uranyl solutions after contact with the biomass indicates the coexistence of uranyl(V) with uranyl(VI).