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Table 3

Level of pH, alkalinity, and hardness in water collected from Carajás upland lakes and their classification.

Lakes pH Alkalinity Hardness

  Range Categories* Concentrations (mg/L) Acid-rain sensitivity*** Concentrations mg/L CaCO3 Class**
Vl 4–7.3 Low-moderate <2 (low) high <5 soft
Am 4–6.7 Low-moderate <2 (low) high <5 soft
TI1 4.8–6.2 Low <2 (low) high <5 soft
TI2 4.8–5.7 Low <2 (low) high <5 soft
TI3 3.6–5.55 Low <5 (low) high <5 soft

pH: low (<6.5); moderate (6.5–9); high (>9); total alkalinity (mg/L as CaCO3): low (<23); moderate (23–148); high (>148) (Michigan Department of Environmental Quality, 2013).


Levels of hardness (mg/L CaCO3): soft (0–60); moderate (61–120); hard (121–180); very hard (>180) (Michigan Department of Environmental Quality, 2013).


Sensitivity of lakes acid rain (Taylor, 1984) based on alkalinity (mg/l as CaCO3): high (0–2); moderate (2–10); low (10–25); nonsensitivity (>25).

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