| atmire.cua.enabled | High population density, industrialization and increased vehicle use have led to severe deterioration of air quality in most urban centres. The most obvious air pollutant is the increased load of suspended particulate matter, which is known to have serious implication on human health. Health effects are mostly associated with particles i„ ule sjze ran„e of about 10 micrometres and below. It was therefore the aim of this study to determine the levels of suspended particulate matter in Kibera, the variation of the particulate matter levels with weather parameters such as rainfall, humidity and temperature, tj,eir heavy metal content and to correlate these levels with incidences of acute respiratory infections (ARI) of children under five years of age. Dustfall in a typical office working environment was also monitored by way of exposing preweighed coarse filters in the office and laboratory environment.
In this study, data on suspended particulate matter (SPM) collected over a one year period in Kibera, a suburban area of Nairobi is presented and discussed. The SPM was monitored as PMio using the “Gent” Stacked Filter Unit (SFU) at heights of two (2) and four (4) metres above the ground level. The suspended particulate matter (SPM) was analysed by gravimetric, atomic absorption spectrometry (AAS) and energy dispersive X-ray fluorescence (EDXRF) techniques. The data analysis included calculation of interelement correlations (pearson-product moment) and enrichment factors.
For the acute respiratory infections (ARI) incidences, a questionaire administered to the
mother elicited information on the symptoms. A total of 146 children were followed throughout the year. The ARI incidences ranged from (29,9-59.6%).
The mean PM.o values varied from (77.6-159.lpg/m3) for samples collected at a height -of two (2) metres and (60.9-138pg/mJ) at four (4) metres above the ground. These values are higher than previous data (30-80pg/m3) reported for a sub-urban site in Nairobi. The PMm data obtained in this work is lower than that reported in urban sites in Asia (15-2l9pg/rn3) and higher than that reported in urban and sub-urban sites in United States of America (1- 97pg/m3) and Europe (2.l-74.2f.ig/nr3). The PMio levels also varied with the weather conditions. The levels of particulate matter were found to increase with temperature, while low values were registered during high humidity. Samples collected after a rainy day and during a drizzle recorded low SPM values (10.8-22.7pg/m3) for coarse particles and (8.10- 14.3pg/m3) for fine particles. This was probably due to the washing away of some of the particulate matter. Mean monthly values showed a strong seasonal trend with the highest values being observed in the cold (51.3-227.4pg/m3) and dry (60.8-269.6pg/m3) seasons. This was probably due to the high levels of soil dust during the dry season and increased residential emissions from the domestic heating ( mainly wood/charcoal and kerosine fuels) during the cold season.
Concentrations in (pg/m3) for elements analysed varied as follows:- potassium (1.435- 4.533), calcium (5.185-7.109), titanium (0.387-0.809), manganese (0.381-0.790), iron (3.485-6.025), copper (0.119-0.169 ), zinc (0.143-0.247), lead (0.168-0.337), bromine (0.029-0.064), and zirconium (0.046-0.152) for coarse particle samples collected at a height of two (2) metres.
Higher values (0.046-7.1 lpg/m3) were observed in the coarse particle fraction for
elements calcium, potassium, iron, titanium and manganese which are associated with crustal
dust. The elements copper, zinc, bromine and lead which are associated with anthropogenic
origin had lower levels (0.029-0.337pg/m3). Most of the highest concentrations were
observed in the dry period ( September- October). For most of the sites calcium, titanium,
zirconium, potassium, iron and manganese showed high correlations (0.612-0.984) with the
suspended particulate matter (SPM) in the coarse particle fraction suggesting soil dust to be the probable source. For some of the sites potassium and calcium also registered low correlations (-0.642-0.482) with SPM. This pointed to other possible sources for these elements apart from soil dust, e.g, burning of urban refuse and residential emissions. Copper, zinc, bromine and lead had low correlations (-0.793-0.386) with SPM in the coarse particle fraction indicating possible anthropogenic sources. However lead and zinc registered high correlations (0.658-0.773) with SPM in the coarse particle fraction for some of the sites.
At the height of four (4) metres the variation (pg/m3) was as follows:- potassium (3.83- 4.75), calcium (1.55-1.97), titanium (0.233-0.541), manganese (0.277-0.656), iron (2.31- 6.29), copper (0.095-0.117), zinc (0.118-0.165), lead (0.120-0.222), bromine (0.045- 0.054), and zirconium (0.036-0.095) fof coarse particulate samples.
Lower concentrations were observed for most elements in the coarse particulate fraction for samples collected at four (4) metres height than at two (2) metres. However, bromine registered a slight increase in concentration at four (4) metres height. The elements calcium, titanium and zirconium showed reduction in concentration by higher factors (0.288- 0.704) than for copper, zinc, and bromine (0.745-1.2) in the coarse particulate fraction. This pointed to resuspended soil dust at two (2) metres height as being responsible for the high levels observed for these elements in the coarse particulate fraction.
For fine particulate samples collected at two (2) metres height Concentration (pg/m3) •*
for elements analysed varied as follows:- potassium (1.503-2.25), calcium (4.77 6.298), titanium (0.133-0.280), manganese (0.079-0.110), iron (0.862-1.102), copper (0.075-0.135), zinc (0.106-0.150), lead (0.165-0.250), bromine (0.031-0.055) and zirconium (0.01 ML027).
The elements potassium, calcium, titanium and iron still registered higher values (0.133-6.3pg/m3) than most of the other elements. Potassium, calcium, titanium, manganese and iron showed both high (0.515-0.925) and low (-0.981-0.453) correlations with SPM at different sites. This may suggest various sources for these elements in the fine particulate fraction (e.g, soil dust, residential emissions and metal/welding works in the area). Zirconium registered high correlations (0.570-0.927) with SPM at all the sites.
For the fine particulate samples collected at height of four (4) metres the variation (pg/m3) was as follows:- calcium (1.45-1.65), titanium (0.222-0.245), manganese (0.107- 0.192), iron (0.326-0.818), copper (0.088-0.115 ), zinc (0.081-0.116), lead (0.162-0.225), bromine (0.031-0.034), and zirconium (0.012-0.022).
Levels for most elements remained in the same range as observed at two (2) metres height except for calcium, bromine and iron. Higher reduction factors were observed for calcium (0.262-0.303), bromine (0.618) and iron (0.378-0.742) than for titanium, copper, zinc, lead and zirconium (0.773-0.900). Manganese registered an increase in concentration at this height.
Low enrichment factors were observed at both heights for potassium (0.265-1.699), calcium (0.401-9.637), titanium (0.790-6.42), manganese (3.476-17.02) and zirconium (2.43-9.24) suggesting soil dust to be the main origin. However marginal enrichment for calcium (6.28-9.64) in the fine particulate samples at two (2) and manganese (10.48-17.02) at four (4) metres height were observed hinting at other possible sources apart from soil dust. The high enrichment factors observed for copper (10.77-228.3), zinc (12.385-124.6), lead (59.37-1967.0) and bromine (152.49-3038.7) at both heights suggested anthropogenic activites (i.e, industrial operations, automobile exhausts and residential emissions) tp be the major contributors.
Elemental concentrations in this study were found to be higher by factors ranging from (1.3 to 6.0) for most elements (calcium, potassium, titanium, manganese, iron, zinc and zirconium) except for copper, bromine and lead than previous reported case for a sub urban site in Nairobi. Compared to studies in other parts of the world (Europe and Asia) data obtained from this study was found to be higher.
The average Acute Respiratory Infections (ARI) incidences was 8.49±4.01 episodes pet- child per year. The ARI incidences point prevalence showed a seasonal trend with both the cold and dry seasons having high point prevalence. Regressional analysis of monthly mean ARI incidences of children under five (5) years of age on PMio and the fine particulate levels showed no significant correlation.
Dustfall sampled in a typical working office environment varied from (0.449 to 2.03pg/cm2/day). The levels of dustfall sampled in the various offices (four) were found to depend on the position of the filter in the room (near windows, doors and height from floor), opening of windows, doors and the use of dust blowers and floor sweeping.
Bromine/lead ratios varying from (0.137-0.392) were observed at both heights hinting
at vehicular emissions as the major sources of these elements at some of the sites.
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