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Table 2 Mean concentration (ppb) of heavy metals in acidified and plain wastewater samples

From: Urban mosquitoes and filamentous green algae: their biomonitoring role in heavy metal pollution in open drainage channels in Nairobi industrial area, Kenya

Mean concentration Heavy metals analyzed (ppb or µg/l)
Hg (0.1)a Pb (0.1) Cr (0.5) Cd (0.05) Tl (0.01) Ni (0.2)
Wastewater samples       
 (a) Acidified with HNO3 acid:
Mean concentration ± SE
 < 0.1 ± 0.00 15.31 ± 3.39 8.12 ± 5.40 0.09 ± 0.01 0.05 ± 0.009 4.96 ± 2.13
 (b) Acidified with HCL acid:
Mean concentration ± SE
 < 0.1 ± 0.00 13.62 ± 2.91 3.08 ± 0.99 0.12 ± 0.02 0.05 ± 0.01 6.91 ± 2.69
 (c) Plain (not acidified):
Mean concentration ± SE
 < 0.1 ± 0.00 0.18 ± 0.08 7.49 ± 2.12  < 0.05 ± 0.00 0.03 ± 0.009 0.57 ± 0.29
Standard limits for wastewater       
 WHO [47,48,49] 1.0 10.0 5.0 3.0 20.0
 US EPA [50] 0.03 6.0 5.0 10.0 200.0
 Kenya [51] 5.0 10.0 5.0 10.0 300.0
  1. aThe value in bracket shows the method detection limit (MDL) measured in ppb (µg/l)