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Table 2 Water parameters (mg/l) and seasonal variations of heavy metals concentrations (mg/l) in three water samples per season of fish cultures in Kafr El-Sheikh governorate

From: Seasonal assessment of some heavy metal pollution and Metallothionein gene expression in cultured Oreochromis niloticus

Water parameter/heavy metal Winter Spring Autumn Summer Permissible limits
pH value 8.03 7.33 7.62 7.5 7–8.5
Temperature 18 +  0.5 °C 20 + 0.5 °C 22 +  1 °C 25 +  1 °C  
Chemical oxygen demand (COD) (mg/l) 10 20 30 35 ≤ 10
Dissolved oxygen (DO) (mg/l) 5.05 4.59 4.6 4.3 ≥ 5
Alkalinity (mg/l) 140 120 110 90 20–150
Total hardness (mg/l) 70 90 175 230 30–180 (Santhosh and Singh 2007)
Ammonia (NH3) (mg/l) 1.1 3.6 3.2 4.8 0.5
Nitrite (NO2) (mg/l) 0.42 0.3 0.4 0.3 < 0.2 (OATA 2008)
Cadmium < 0.001 < 0.001 < 0.001 < 0.001 ≤ 0.003
Copper < 0.01 < 0.01 < 0.01 < 0.01 ≤ 1
Lead < 0.001 < 0.001 < 0.001 < 0.001 ≤ 0.5
Zinc < 0.001 < 0.001 < 0.001 0.59 ≤ 2
  1. Data represented as an average of three samples