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. 2013 Jun 17;4:147. doi: 10.3389/fmicb.2013.00147

Figure 2.

Figure 2

Spatial variation of physico-chemical parameters from sampling locations on the San Pedro River. Permissible maximum limits are shown in dotted lines. pH values between 6.5 and 8.5 units are considered as good quality in potable water (NOM-127-SSA1-1994). Conductivity values above 2000 μS/cm are exceeding the permissible limits. Nitrogen values above 40 mg/L are exceeding the permissible limits. Phosphorus levels rating higher than 20 mg/L is considered as poor water quality. Total solid suspended has a permissible value of 120 mg/L. Dissolved oxygen concentration limits are between 5.5 and 8.0 mg/L (Gúzman-Colis et al., 2011). BOD and COD concentrations limits are 150 and 100 mg/L respectively according to Mexican norms NOM-003-ECOL-1997 and NOM-001-ECOL-1996.