What is the typical pH range of natural freshwater?

What is the typical pH range of natural freshwater?

• A. Approximately 5.5 to 7.0
• B. Approximately 6.5 to 8.5
• C. Approximately 7.0 to 9.0
• D. Approximately 6.0 to 7.0

Answer: (B)

Natural freshwater is buffered by dissolved carbonates, which keeps its pH from swinging widely. This carbonate system (involving CO2, bicarbonate, and carbonate) tends to hold most rivers, lakes, and streams in a near-neutral to mildly basic range, commonly around 6.5 to 8.5. Daytime photosynthesis can raise pH a bit, while nighttime respiration can lower it, but the overall typical range stays within about 6.5 to 8.5. While some waters can be more acidic or more alkaline depending on geology and pollution, the range 6.5 to 8.5 best reflects what is usually observed in natural freshwater.

Natural freshwater is buffered by dissolved carbonates, which keeps its pH from swinging widely. This carbonate system (involving CO2, bicarbonate, and carbonate) tends to hold most rivers, lakes, and streams in a near-neutral to mildly basic range, commonly around 6.5 to 8.5. Daytime photosynthesis can raise pH a bit, while nighttime respiration can lower it, but the overall typical range stays within about 6.5 to 8.5. While some waters can be more acidic or more alkaline depending on geology and pollution, the range 6.5 to 8.5 best reflects what is usually observed in natural freshwater.