LA CORTEZA ARBÓREA COMO BIOMONITOR DEL DEPÓSITO ÁCIDO EN LA CUENCA DE MÉXICO

Resumen

The atmospheric deposit and the washing of the leaves influence soil chemistry as the K, Ca, Mg and Mn lixiviation modifies its acid condition. Tree bark captures part of this product that is measured through electric conductivity (A), hydrogen potential-(pH) and average buffering capacity (P0); its quantification explains the chemical dynamics and its removal. The total atmospheric acid deposit in Mexico City varíes from a pH of 3.5 to 5.0; during the rainy season, it goes from 5.0 to 5.6, and in the dry months, from 3.0 to 5.6. In 1995 and the dry season of 1996, field work was carried out in the forests of Villa del Carbón, lzta-Popo and Zoquiapan all of which belong to Estado de Mexico, and in the Desierto de Los Leones park, Distrito Federal, in order to monitor the atmospheric deposit present in the tree barks of Pinus montezumae (pine), Cupressus lindleyi (white cedar) and Abies religiosa (Sacred fir). Results showed that the deposited acidity in the pine species varied from 3.15 to 3.6 of pH; from 4.0 to 4.35 in fir trees and from 4.3 to 6.3 in cedar trees. The forests inside the Mexican basin revealed a variation from 2 to 4 pH units; outside of it, the difference was of one unit. lt was concluded that there is acid homogeneity in the forests that belong to the Valle de Mexico basin, but not in Mineral El Chico. Cupressus lindleyi showed the highest buffering capacity and is resistant to the acid effect.