Assessment and modeling of the effect of airborne deposition on the acidity of the Rio Grande Basin water

Airborne pollutants such as SO42- and NO3- that cause acid rain reach the earth surface via wet deposition or dry deposition, which can pollute the earth's valuable water resources. Recent studies shows the increasing concentration of SO 42- and NO3- in the Rio Grande River Basin. The objectives of this study are to assess the effect of airborne particulate pollutions on the water quality of the Rio Grande basin and to simulate the acidity of the Amistad Reservoir water using the CE-QUAL-W2 under different flow and precipitation conditions. The data study has indicated that the concentration of wet deposition ions decreases when the amount of precipitation increases. The higher concentration of SO4 2- and NO3- can increase the acidity while the higher concentration of Ca2+ and Na+ can decrease the acidity of the precipitation. The analysis of available field water quality data show that the pH in Rio Grande River decreases when the flow rate increases thereby decrease the buffering capacity of the river. Since the runoff from the precipitation increases the flow rate, the observation appears to suggest a direct relationship between precipitation and pH along the Rio Grande River. The pH simulations for Amistad Reservoir under different flow and precipitation conditions demonstrate that the water pH lies within the range of 7.4 to 8.2. The simulation has also indicated that the Reservoir pH is only marginally affected by the pH of the precipitation.