Assessment of Lead Levels in Dust and Date Palm ( Phoenix dactylifera L.) in 6-10 Year-old School Children Environment in Riyadh City, Saudi-Arabia

Abstract

To assess lead levels in the school environment of 6-10 year-old
children in Riyadh City, swept-dust, soil and date palm (Phoenix
dactylifera L.) leaflets were obtained from 55 schools located in a
35 km section passing through the city centre. The study area was
divided into eastern, central, western and rural sections, the central
area (city centre) being the section where the impact of environmental
lead pollution is known to be the highest. Swept-dust
samples were obtained from the inside and outside of school buildings
in order  to assess the extent of lead migration from streets into
classrooms. Hence, samples were collected from school entrance
(SCL1), school playground (SCL2), first floor (SCL3) and second
floor (SCL4) of each school building. Soil and date palm (Phoenix
dactylifera L.) leaflets were taken from the inside perimeter of each
school. The leaflets were divided into washed (LFWS) and unwashed
(LFUW) subsamples. Soil samples were collected from the
top 5 cm of soil (SLA) and also at a depth of 30 cm, close to the
date palm trees (SLB). After digestion with concentrated nitric acid
at 80°C,. the samples were analysed for lead by flame atomic
absorption spectrophotometry.
The results showed that lead distribution is a reflection of traffic
density and pollution from automotive emissions. Analysis of
variance showed that mean lead concentrations for all variables in
the city centre, were significantly different from those of the eastern
and western sections. The dust-Pb means were found to be
the highest in the city centre, i.e., 367  μg g^-1, 273  μg g ^-1, 253  μg
g^-1 and 214  μg g^-1 (from SCL1 to SCL4). These are higher compared
with the eastern section (131  μg g^-1, 103  μg g^-1 , 117  μg
g^-1 and 130  μg g^-1) and the western section (164  μg g^-1, 135  μg
g^-1, 129  μg g^-1 and 135  μg g^-1). Lead pollution in the city centre
was also reflected in unwashed (east = 20  μg g^-1, centre = 40  μg
g^-1, west = 27  μg g^-1, rural = 15  μg g^-1) and washed leaflets
(east=9 μg g^-1, center = 18 μg g^-1, west = 11 μg g^-1, rural=7 μg
g^-1). Lead levels in unwashed leaflets showed a significant correlation
with washed leaflets (0.77) but a poor correlation with
SLB (0.32), suggesting metal absorption from the atmosphere.
From this study, it is concluded that in spite of the dilution of
windblown inhalable particulates and the reduction of Pb levels in
gasoline, undue pollution from this metal is shown to exist in the
6-10 year-old schoolchildren environment in Riyadh city centre.