Neutralization of acid rain by yellow-sand in East Asia; A Numerical study

Terada, Hiroaki   ; Ueda, Hiromasa*; Wang, Z.*

The neutralization of acid rain by yellow-sand in East Asia was investigated numerically by an Air Quality Prediction Modeling System (AQPMS). AQPMS consists of advection, diffusion, dry and wet deposition, gas-phase chemistry and the liquid-phase chemistry. Different from the previous ones for Sahara and Australian deserts, a new deflation module of the yellow-sand was designed here, and this module was linked to the AQPMS. Firstly, for model validation, predicted various values were compared with measured values at atmospheric monitoring stations, and a reasonable agreement was obtained for April 1995. Secondly, a sensitivity experiment about chemical effects of yellow-sand was made and the result of it exhibited a strong neutralization of the precipitation by the yellow-sand. The monthly mean pH values in the northern China showed a remarkable increase of 0.6-1.8 by neutralization effect of the yellow-sand, while the increases in the southern China were less than 0.1. Even in Korea and Japan the yellow-sand caused the increase of the pH value of rain by 0.1-0.2.