Mobility, spatial variation and human health risk assessment of mercury
in soil from an informal e-waste recycling site, Lagos, Nigeria
Anselm, Oluwaseun H.
Cavoura, Olga
Davidson, Christine M. and
Oluseyi, Temilola O.
Oyeyiola, Aderonke O.
Togias, Konstantinos
Spatial variations and mobility of mercury (Hg) and Hg associations with
other potentially toxic elements (PTEs) were studied in soil samples
from Alaba, the largest e-waste recycling site in Nigeria and West
Africa. Total Hg concentration was determined in surface soil samples
from various locations using cold vapour atomic absorption spectrometry
(CVAAS) following microwave-assisted acid extraction, while sequential
extraction was used to determine operationally defined mobility. The
concentrations of the PTEs arsenic (As), cadmium (Cd), chromium (Cr),
copper (Cu), manganese (Mn), mercury (Hg), nickel (Ni), lead (Pb) and
zinc (Zn) metals were determined using inductively coupled plasma mass
spectrometry (ICP-MS) following microwave-assisted digestion with aqua
regia. Total Hg concentration ranged from<0.07 to 624 mg/kg and was
largely dependent on the nature and intensity of e-waste recycling
activities carried out. Mobile forms of Hg, which may be HgO (a known
component of some forms of e-waste), accounted for between 3.2 and 23%
of the total Hg concentration, and were observed to decrease with
increasing organic matter (OM). Non-mobile forms accounted for>74% of
the total Hg content. In the main recycling area, soil concentrations of
Cd, Cd, Cu, Hg, Mn, Ni, Pb and Zn were above soil guideline values
(Environment Agency in Science Report, 2009; Kamunda et al., 2016).
Strong associations were observed between Hg and other PTEs (except for
Fe and Zn) with the correlational coefficient ranging from 0.731 with Cr
to 0.990 with As in April, but these correlations decreased in June
except for Fe. Hazard quotient values>1 at two locations suggest that Hg
may pose health threats to people working at the e-waste recycling site.
It is therefore recommended that workers should be investigated for
symptoms of Hg exposure.
(EN)
