Hezekiah B. Olaniyi

Air pollution in a large tropical city with a high traffic density — results of measurements in Lagos, Nigeria

Abstract The joint project, ‘Environmental Monitoring and Impact Assessment in Nigeria’ consisted of universities from Nigeria, Germany and Great Britain, and was funded by the European Union. Within the context of this project, an air monitoring station was purchased and placed in Lagos, the former capital of Nigeria. In addition to these permanent measurements, single samples were taken at different places in Lagos. A northern wind, the so-called Harmattan, transports much dust from the Sahara. But most of the identified air pollution in Lagos is caused by the traffic which can even be recognized without measurements, by strong turbidity, bad smell and eye irritation. This pollution is caused by the combination of many strongly emitting vehicles and frequent traffic jams. Diesel vehicles emit plumes of black smoke consisting of soot. Many petrol engined cars exhaust blue smoke which is caused by unburnt oil; market places are established especially around bus stops, and many people are exposed to unhealthily high concentrations of aromatic hydrocarbons, CO and particles. The results of measurements at such places are presented here. The measured CO values, for instance, often exceed the limits set by WHO guidelines. These initial results show that drastic measures are necessary to protect the population against this high pollution. The measured benzene concentrations cause a raised carcinogenic risk.

Traffic pollution: preliminary elemental characterisation of roadside dust in Lagos, Nigeria

Roadside dust collected from different parts of Lagos metropolis were analysed for heavy metals and other trace elements using a combination of instrumental neutron activation analysis (INAA), inductively coupled plasma-optical emission spectrometry (ICP-OES), and flame atomic absorption spectrometry (FAAS). The results show a positive correlation of the concentration of Pb and some other vehicular emission-related elements with the traffic density. Automotive emission was also found to be the main contributor to Pb concentration in the roadside dust but some elements which hitherto have been linked with automotive emission, such as cadmium and nickel, did not show any strong correlation with traffic density.

Characterization and source identification of airborne particulate loadings at receptor site-classes of Lagos Mega-City, Nigeria

Size segregated suspended particulate matter (PM2.5 and PM2.5-10) were collected using Gent low-volume air sampler at four different receptor site-classes in Lagos Mega City, Nigeria. The particulate mass loading was quantified and the concentration was analyzed to examine the pattern and variation from one receptor site-class to another. The PM2.5/PM10 ratio varied among the site-classes with the residential and marine sites having the least and highest ratio of 0.31± 0.13 and 0.49 ± 0.17 respectively. Particulate loading was higher on weekdays than on weekends (by a factor of about 1.5) in all but the marine site-class.The mean PM2.5/PM10 ratio is 0.41 ± 0.15, which suggests that traffic emission is not the principal source of the Particulate Matter (PM). The INAA assay of the particulates detected ten elements: As, Br, Ce, K, La, Mo, Na, Sb, Sm and Zn. Except for Br, Mo and Sb, the detected elements were more pronounced in the coarse-fractioned filter. Principal Component Factor Analysis (PCFA) of the detected elements identified some common sources (traffic-related, traffic emission, sea-salt and industrial emission) for both PM fractions at the four receptor site-classes. Implications: An assessment of the ambient air quality of the study area has been carried out. Some residential areas can have high particulate matter (PM) loading even more than industrial areas due to contributions from local and transport from neighboring sites. The site-classes have common PM sources and PM loadings are generally lower on weekends than on weekdays, with the coarse fraction being dominant. Measures should be put in place to reduce contributions to PM loading by biomass burning, traffic-related, and industrial emissions, as they have been identified as common and prominent anthropogenic sources of PM.

Determination of elemental composition of TSP from cement industries in Nigeria using EDXRF technique

Abstract Suspended dust particulates within and around cement industries in Nigeria were sampled and analyzed using EDXRF technique. The TSP concentrations ranged from 500 μg/m 3 to 1300 μg/m 3 within the factory, while outside the factory the range is from 100 μg/m 3 to 370 μg/m 3 . In major shop floors, particulate matter concentrations as high as 10 4 μg/m 3 were recorded. Elements detected include Na, Al, Si, K, Ca, Ti, V, Cr, Mn, Fe, Co, Zn, S, Cu and Pb. Highly enriched elements were Ca, S, Zn, Cu and Pb with enrichment factors 30–350, 75–200, 100–14 700 and 20–700 respectively. Elements such as Al, Fe, Mn, Na, V and Cr were moderately enriched. Source apportionment of the pollutants by chemical mass balance (CMB) and factor analysis methods revealed cement contributions up to 60% within the factory and 30% around the residential neighbourhoods. Control measures like electrostatic precipitators have been strongly suggested to these factories.

A complimentary tool in the determination of activity concentrations of naturally occurring radionuclides.

The determination of activity concentrations of radionuclides requires a reliable gamma spectrometry system, which also depends on the compulsory attainment of secular equilibrium amongst the progenies of the radionuclide of interest. This is often difficult to attain and hence a helium particle induced x-ray emission technique, not requiring the compulsory attainment of secular equilibrium, was used to determine the actual concentrations of the elemental content of tailings from the high background radiation tin mining area, Jos, Nigeria. The activity concentrations of the radionuclides of (40)K, (232)Th and (238)U were also calculated based on their elemental analyses, providing reliable information about the heads of uranium ((238)U) and thorium ((232)Th) series on the study area.

An optimization of PIXE procedure for high-Z species in a lower Z matrix.

Singly charged helium ((4)He(+)) induced PIXE technique was used for the elemental analysis of tin mining tailings. The procedure gave very good results especially when a correction was implemented for X-ray absorption in the low-Z region of the spectrum. The use of helium ions to induce X-ray emission was found to be adequate, especially in the case of the intermediate light elements (12<Z<21) where the nuclear reaction sensitivity decreases. Consequently, helium-induced X-ray emission analysis can be usefully applied for trace element detection of low-Z species in a higher Z matrix as well as high-Z species in a lower Z matrix.

Spatial and temporal variations of the particulate size distribution and chemical composition over Ibadan, Nigeria

Spatial and temporal variation of suspended particulate matter was measured in Ibadan, Nigeria during the raining and dry months of 2013 and 2014, respectively. Six different locations were considered, reflecting city-spread, population density, lifestyle, and vehicular- and industrial-related activities. Elemental characterisation of the samples were carried out using energy dispersive x-ray fluorescence (ED-XRF) spectroscopy, while the black carbon content was determined using an optical transmissometer. Backward trajectory analysis indicated that most air mass was of maritime origin except on few occasions that suggested the Sahara desert origin. Average PM2.5/PM10 ratio for the entire sampling period was 0.32 ± 0.04. This is slightly lower than the reported values in the coastal city of Lagos, partly because of more adequately paved and better road networks resulting in lower dust re-suspension and/or there are relatively finer fraction particulates from other sources, which might include marine, industrial, and secondary emission-related sources. Black carbon showed predominance in the fine fractions and was, majorly, of traffic origin. Major enriched elements of concern are S, Zn, As, and Pb aside from those of sea origin. Refuse burning was observed to be the principal source of Pb and Zn in all the sites except one, which showed major industrial-related activities source. This study will provide data for future measurement and modelling works as well as providing a benchmark for relevant agencies for policy making on setting emission standards for the country.

Radiological indices of technologically enhanced naturally occurring radionuclides: a PIXE approach

This paper reports an assessment of the level of the radionuclides (40)K, (232)Th and (238)U in environmental soil samples (process waste), and hence their calculated dose rates. For this purpose, the radioactivity from three natural radionuclides was determined in tin process-waste samples in Jos, Nigeria. This work is based on the particle induced x-ray emission (PIXE) approach, devoid of the secular equilibrium, and most of the resolution, interference, self-absorption, geometrical and density correction problems inherent in gamma spectrometry. Many potential environmental hazards have been observed and the data would be of use to the government in its remediation plan for the study area. The high hazard indices require taking adequate measures to check exposures, and an underground lining in the waste ponds to prevent direct contact with the waste pile is recommended. The use of the wastes as building materials should be stopped and use of soils around this area in any development projects should be discouraged until detailed studies on indoor radiation doses and the effects on the inhabitants of prolonged exposures have been carried out.

Characterization of pollutants around tin mining and smelting operations using EDXRF

Abstract Energy dispersive X-ray fluorescence (EDXRF) in combination with HpGe based passive gamma spectrometry is used to measure the concentration of toxic heavy metals and radionuclides in the soils around a lead/tin smelter and also air particulates and mining wastes collected from some tin mines and a tin mill. Toxic heavy metals like Sn, Pb, As, Zn, Bi and Ni were detected and found to be highly enriched in the soils, air particulates and mine wastes. The concentrations of Th and U ranged between 0.01 and 2.94%, and 0.002 and 0.11% in the tailings and between 2.25 and 9.09%, and 0.25 and 0.56% in the monazites respectively. The radiological waste management implications are discussed.

An ICP-OES, TXRF, and EDXRF analysis of airborne particulate samples in an iron and steel smelter environment

Elemental concentrations of air particulates collected by gravimetric method in a scrap iron and steel smelter industry were determined using a combination of four different techniques: total reflection X-ray fluorescence (TXRF), the conventional energy dispersive X-ray fluorescence (EDXRF), the modified (polarized) energy dispersive X-ray fluorescence ED(P)XRF, and the inductively coupled plasma optical emission spectroscopy (ICP-OES) analytical techniques. A number of elements were detected by all the techniques, some by one or two while some are better detected by a particular technique. The ICP-OES and TXRF techniques have low detection limits worth of consideration despite the risk of contamination possible during sample preparation. The techniques are observed to be adequate for analytes above K except for Br and Pb, which are significantly lost during digestion of samples. The Mo-target EDXRF, just like ICP-OES and TXRF, cannot detect elements below K but substitute well for them in the analysis of volatile elements like Br and Pb despite its higher detection limits for the said elements. The Mo-target EDXRF is also observed to be inadequate for rare earth elements with energies close to that of Mo as a result of possible poor resolution of the energy peaks. The ED(P)XRF is more adequate in the analysis of low Z elements as well as volatile ones. Where volatile elements like Cl, Br, and Pb and/or low Z elements are of primary interest, the use of techniques involving no elaborate sample preparation should be considered.