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

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

Mean concentration	Heavy metals analyzed (ppb or µg/l)
Mean concentration	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

^aThe value in bracket shows the method detection limit (MDL) measured in ppb (µg/l)

ISSN: 2730-7182