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.

Quality evaluation of the k 0 -standardized neutron activation analysis (k 0 -NAA) at Dalat research reactor (DRR) has been implemented by analyzing the SMELS, a synthetic multi-element standard material as well as the certified reference materials for purposes of validation and verification of the method. The results revealed that the k 0 -NAA established at DRR has met the requirements of multi-element analysis for the intended applications with about 42 elements: Al, As, and Zr in matrices of environment, geology and biology among others. Evaluation criteria for the laboratory quality used in this work are the statistical analysis parameters namely: u-scores, laboratory result/certified value ratios and relative biases as well as the control charts those are shown in the paper.

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