अम्ल वर्षा का pH मान क्या होता है? 5.5 या उससे कम 12.5 या अधिक 10.5 या अधिक 8.5 या अधिक

Normal rain is slightly acidic (pH about 5.6) because of dissolved CO₂. Rain with a pH of about 5.5 or lower is called acid rain; it is caused by sulphur dioxide and nitrogen oxides forming acids in the air.