Basic precipitation or Alkaline precipitation occurs when calcium oxide or sodium hydroxide are emitted into the atmosphere, and are absorbed by water droplets in clouds, which then fall as rain, snow, or sleet. This can increase the pH of soil or bodies of water, which can lead to increased fungal growth.
The principal cause of basic rain is emissions from factories and waste deposits. Basic rain can be viewed as opposite to acid rain. Acid rain has posed a serious threat to numerous ecosystems surrounding rivers, lakes and forests.