Chemical Characters and Stability Analysis for the Rainwater in Southeast Region of Beijing City

Based on the test results of water quality for seventeen times rain and rainfall in Southeast Region of Beijing city,it was conducted for a comprehensive water quality investigation of the rain-water and rain-runoff in the area,including characterization of their chemical properties and analysis of the water stability.The in- vestigation results show that the collected rain-water and surface runoff water are soft and Type-Ⅰwater within the category of bicarbonate calcium.The results also show that the pH is well related with alkaline par- ticles in the rain-water and runoff water within this area.It indicates that the rain-water and runoff water within this area have been contaminated to a certain degree by a nitrogen-compounds or a hydrocarbons from intensive human activities.Water stability analysis in this study focuses on its potential of precipitation and dissolution,in which carbonate calcium (CaCO₃)plays a dominant role.The results show that only runoff water on traffic roads prefers to precipitate while rain-water and other runoff water in the areas are character- istic of their solubility.Therefore,the problems of polluted rain-water and engineering installations corrosion should be especially awared of during the rain-water usability.