Elemental Concentration of Inhalable and Respirable Particulate Matter in Urban Area During Wet Season

: Previously, the capture of suspended particulate matter focused on the total suspended particulate matter, until recent research into the health impacts of suspended particulate matter suggests that minute particles that have toxic substances adsorbed onto their surface are insidious and deleterious for human health and vegetation. The Inhalable fraction and respirable fraction were captured between the month of May 2009 to October 2009 using SKC Air Check Gravimetric Sampler- Model 210-5000 serial No. 20537 and respirable foam for I.O.M sampler. The elemental composition (Co, Ni, Zn, Cu, Fe, Pb, Cr, Mn and Cd) were analyzed by using Atomic Absorption Spectrophotometric (AAS). The data generated were subjected to descriptive analysis. In inhalable fraction,the enrichment factor ranged from 1-73.3 while in respirable ,it was 1- 72.9.Lead had the highest mean concentration in both inhalable and respirable fraction. From the enrichment factor

http://dx.doi.org/10.4314/jasem.v18i1.11 Introduction: Precipitation is one of the most scavenging processes of particulate matter. Particulate that could possibly re-suspend are suppressed as a result of torrential down pour. This will in turn reduce the amount of trace metals in the atmosphere.
The most widespread metals in airborne particulates from the most large cities and urban areas which are usually associated with the vehicular traffic and other anthropogenic sources such as stationary fossil fuel combustion and refuse incineration plant (Pacyna and Pacyna 2001;Lee et al., 2007).
There is a direct association between atmospheric Inhalable particulate matter (PM 10) and people's health (Schwartz et al .,1996). Exposure to increased PM 10 shows a high correlation with increase of respiratory diseases pulmonary damage and mortality among the population (Ilabaca et al 1999, Harrison andYin 2000;Cifuentes et al., 2000).
Respirable fraction (fine fraction) of particulate matter (PM2.5 and less) are retained in the alveolar region of the lungs and are able to diffuse into the blood circulation, and may subsequently induce inflammation, oxidative stress (Soeren Sen et al., 2003), and increased coagulation of the blood (Segaton et al., 1995).
Consequently, the study is designed to obtain a baseline concentration of the trace metal in respirable and inhalable suspended particulate matter and to compute the enrichment factors.
Apart from the deleterious effect of particulate matter on health, it also reduces visibility and plays an important role in the deterioration of monuments and buildings. The particulate matter impact on climate is primarily a cooling effect due to increased scattering to space as the atmospheric particulate matter burden increases. According to IPCC 2001, the overall cooling by particulate matter may counter balancing global warming by green house gases and its effect on cloud condensation (Levin et al., 2003).
Sapele is located near the junction of Jamieson and Ethiope rivers and about 80 mile (144 kilometers) from the sea, well closer into the timber yielding forest of the interior. Sapele is one of the first-rate wood industries in this region. However, it is a commercial city with four petroleum and allied industries. The climate is tropical with two distinct seasons, wet and dry. The major activities among the people of Sapele that generate particulate pollution are usually bush burning as a pre planting preparation, welding and vulcanizing combustion of solid waste as a means of waste disposal, gas flaring, re-suspension of dust from unpaved road, and the production of charcoal which involves the burning of wood in an open space from dawn till dusk in four different locations in the city. These charcoal are usually exported to other countries and sometime nearby cities.  In line with the objectives of the study, ten monitoring sites were carefully selected to represent all the quarters of the city with high air pollution sources. These sites were created within the vicinities to reflect variation in traffic volume and human activities.

Sample Digestion And Measurement:
The trace metals Pb, Cd, Ni, Cu, Co, Fe, Zn, Cr and Mn were determined by AAS (Thermo electron corporation Atomic Absorption spectrometry, S. Series) A portion of the effective filter and respirable foam were digested separately with 20ml 1:1 HNO 3 in a beaker and covered with a watch glass which was concentrated to about 5ml on a hot plate at 150-180 0 C. 10ml of 1:1 HNO 3 was added to repeat it. The extract was filtered through a 541 filter paper, the filter paper and the beaker was washed with 0.25M HNO 3 . The filtrate was transferred and washed into 50ml volumetric flask. The chemical and reagents used for analysis were analar grade. (Harrison,1986) Data Analysis: The results gotten from this work were subjected to descriptive statistics and enrichment factor computation. In this work, Iron was chosen as the reference element during the computation of enrichment factor. Jian et al., (2004), Ukuo and Udiokwere.,(2005) used Iron as a reference.
crust Fe where 1 C is the concentration of the element considered in the Inhalable or respirable of the crust and Fe C is the concentration of the reference element (Fe).Iron was chosen as reference element because is one of numerous crustal elements for the computation of enrichment factor The elemental concentration in the crust used in this study was got from Wedephol 1968. An enrichment factor close to 1 indicates that the relative concentration of a given element is identical to that which is present in the soil. An enrichment factor greater than 1 indicates that the element is more abundant in the air relative to that found in the soil, while values less than 1 suggests a depletion of the element in the air over that found in soil.

RESULTS AND DISCUSSION
The major sources of Cd are metal industries engage in extraction, refining, machine, electroplating and welding of Welding of Cadmium materials. By product of refining Lead, Zinc and Copper pesticides, fertilizers, Cadmium -Nickel batteries, reactor poising in nuclear fission plants and in production of tetraethyl lead gasoline. The Chronic and acute poisoning inhalation of fumes and vapors of Cd cause damage to the kidney, emphysema, bronchitis, cancer, gastric and intestinal disorder, disease of the heart, liver and brain. While the major sources of Pb are automobile emission, lead smelters, combustion of coal, fuel oil and lead -arsenate pesticides. Pb is absorbed through gastro-intestinal respiratory tract and deposited in mucous membrane of nose, throat and in the lung.
The World Health Organization (WHO) has established air quality guidelines (WHO, 2000) similarly European Union has set annual limits on selected trace metals such as 500ng/m 3 for Pb, 6ng/m 3 for As, Ni 20ng/m 3 and Cd 5ng/m 3 .  Tables 3 and 4 show the descriptive statistics and the enrichment factor for inhalable and respirable suspended particulate matter respectively. The total mean concentration values of the analyzed trace metals follow the order: Pd>Fe>Cr>Cd>Cu>Zn.
From Table 3, Cd is highly enriched while Pb is moderately enriched. While in the respirable concentration Cd was also highly enriched and Pb was moderately enriched. The data obtained in this study is compared with data from previous studies by other authors (Ukuo and Ndiokwere ,2005;Chow et al.,1994;Dongarra et al 2007;Obioh et al 2005;Yele et al., 2004;Martin et al., 2007). Figure 2 shows the comparison of Mean inhalable and respirable for the different trace metals; from it we see that Pb has the highest concentration. The mean of the three meteorological parameters measured in this work. The mean ambient temperature was in the range of 27.9 -29.9 0 C, the relative humidity was in the range of 75 -85% and the mean wind speed was in the range of 0.85 -0.95m/s.