national monument. noun. Definition of national monument for English Language Learners. : a place (such as an old building or an area of land) that is owned and protected by a national government because of its natural beauty or its importance to history or science. Britannica.com: Encyclopedia article about national monument.
Brown or discolored water is caused by minerals, sediment, or rust that may accumulate in the water mains over time. When the water from your tap is brown this indicates a disturbance in the water main that stirs up these deposits.
Key Concepts. 1  Carbon dioxide (CO2) gas dissolved in water can cause water to become acidic. 2  The acidity of water from dissolved CO2 can be reduced by a base such as baking soda (sodium bicarbonate).