TECHNICIANS' KNOWLEDGE AND PRACTICES OF ELECTRONIC WASTES MANAGEMENT AND ASSESSMENT OF HEAVY METAL CONCENTRATION IN SOILS IN IBADAN, NIGERIA

Abstract

Electronic wastes (e-wastes) are increasingly being generated in Nigeria and their indiscriminate disposal has potentiai for environmental degradation. However their effects on the soil are yet to be well studied. The study, therefore, assessed technicians' knowledge and practices of e-wastes management as well as the characteristics of e-wastes and heavy metal concentration in soils from dumpsites in Ibadan. A two-stage random sampling technique was used to select 200 respondents consisting of 40 computer, 60 mobile phone, and 100 transmitter technicians from clusters of technicians at Dugbe, Ogunpa and lyaganku areas of Ibadan. The technicians' knowledge and practices of e-wastes management was assessed using a validated semi-structured questionnaire. Samples of e-wastes collected from purposively selected Pure stream E-wastes Dumpsite (PED), Mixed Dumpsite (MD) and Zero E-wastes Dumpsite (ZED) were characterized using gravimetric method. Soil samples from the dumpsites were analyzed for heavy metals and the results were compared with the National Guideline Limits (NGL). The generated data were analyzed using descriptive statistics, ANOVA and Mann Whitney U test. The respondents mean age was 30.0±8.6 years and 95.7% were males. The mean knowledge scores obtained by computer, mobile phone and transmitter technicians were 5.5±2.4, 4.8±1.9, and 4.1±1.2 respectively out of a maximum of ten points (p<0.05). Burning was a preferred method of e-wastes disposal by computer (42.5%), mobile phone (54.3%) and transmitter (65.5%) technicians. Proportions of the computer, mobile phone and transmitter technicians who separated e-wastes from other wastes were 45.5%, 34.3%, and 32.5% respectively. The main e-wastes components at the dumpsites were: glass (PED - 89.2%; MD - 75.3%), ferrous wastes PED-65.0%; MD- 53.1%) and plastics (PED - 55.0%; MD-45.6%); no e-wastes were recorded at the ZED. At PED, the mean heavy metal concentrations are as follows: cobalt (5.7±0.2 mg/kg); lead (5.1±2.7 mg/kg) arsenic (0.17±0.01 mg/kg); cadmium (0.08 ±0.01 mg/kg) and chromium (0.32±0.1 mg/kg). The heavy metal concentrations obtained from MD soils were cobalt (0.38 ± 0.3 mg/kg), lead (0.17±0.1 mg/kg), arsenic (0.11±0.09 mg/kg), cadmium (0.03±0.02 mg/kg) and chromium (0.28±0.19 mg/kg), while the mean heavy metal concentrations at ZED were cobalt (0.26±0.2 mg/kg), lead (0.06±0.04 mg/kg), arsenic (0.07±0.05 mg/kg), cadmium (0.02±0.01 mg/kg) and chromium (0.1±0.01 mg/kg). Significantly lower concentrations of cobalt, lead, arsenic, cadmium and chromium were recorded in soils from MD compared to values from PED (p<0.05), while heavy metal concentrations recorded at ZED showed that cobalt, lead arsenic, cadmium and chromium in the soils had significantly lower values compared with the PED (p<0.05). All heavy metal concentrations obtained from soil samples from the three dumpsites were lower than the NGL, for cobalt (50 mg/kg), lead (140 mg/kg), arsenic (12 mg/kg), cadmium (10 mg/kg) and chromium (64 mg/kg). Electronic technicians' knowledge of e- wastes management was low. Soils in e-wastes dumpsites were polluted with heavy metals. Public enlightenment interventions are required for controlling heavy metal contamination in the dumpsites.