S.O. Ajayi

Trace metal levels in tree barks as indicators of atmospheric pollution

Abstract Barks of six species of trees were sampled at thirty-nine different locations in Ibadan, Nigeria and were analysed for the trace metals lead, cadmium, cobalt, copper, zinc, manganese, and iron. Lead levels in barks from areas with relatively high traffic density were generally higher than lead levels in barks from areas with low traffic density. The lead level recorded in the high traffic density areas, 40–140 μg/g, is low compared to values reported for barks of trees along busy roads in developed countries. For the other metals, no correlation with traffic density was observed.

Pollution studies on Nigerian rivers, II: Water quality of some Nigerian rivers

Abstract Twenty-six Nigerian rivers were sampled during the dry season periods of 1977 and 1978. The samples were analysed for Biochemical Oxygen Demand (BOD5); Chemical Oxygen Demand (COD), pH, dissolved oxygen, ammonia, nitrite and phosphate. Seventeen of the river examined were found to be more or less unpolluted six of them being of high quality. The remaining nine were found to be ‘polluted naturally’.

Trace metal content of fish and shellfishes of the Niger delta area of Nigeria

The trace metal contents of various fish and shellfishes from the Niger delta area of Nigeria were determined. The levels in the shellfishes were higher than those in the fish, which could be due to their being bottom feeders. The levels of fish varied from <0.01-0.10 ..mu..g/g for Cd, < 0.05-3.69 ..mu..g/g for Cu, 0.49-16.52 ..mu..g/g for Fe, and 0.08-6.90 ..mu..g/g for Zn. 15 references, 1 figures, 2 tables.

Pollution studies on Nigerian rivers: The onset of lead pollution of surface waters in Ibadan

Abstract Lead levels in the waters and sediments of the lake of the International Institute of Tropical Agriculture, Agodi Lake, Oba Lake, at three stations on Ogunpa stream, and at three stations on Ona River were measured from October 1977 to June 1978, using the combined APDC-MIBK-flame atomic absorption spectrophotometry technique. The lead levels recorded ranged from 0.2 to 46 μg/L for the aqueous phases; however, the levels in the sediments were much higher, ranging from about 18 to 85 mg/kg (dry weight). Although there is nothing alarming about these levels, the levels of lead in water bodies located in areas with high traffic density were consistently higher than levels for comparable waters in low traffic density areas. Similarly, lead levels were significantly higher in the fresh sediments of water bodies in areas with high traffic density, clearly indicating the onset of lead pollution for those high traffic density areas.

Pollution studies on Nigerian rivers: Toxic heavy metal status of surface waters in Ibadan City

Abstract The levels of the heavy elements cadmium, copper, cobalt, iron, manganese, nickel, lead, and zinc in the major streams and man-made lakes in and around Ibadan City were determined at roughly two monthly intervals between August 1977 and February 1979. They were found to be in the ppb and sub-ppb level except for iron and manganese which were in the ppm range. To assess the quality of these waters with respect to heavy metal contamination, a comparison is made between our results, world averages for both freshwater and seawater, and international water quality standards for drinking water. All elements, except iron manganese, were well within the safety limits. The low level of industrialization in Ibadan has kept its streams and lakes relatively free from heavy metal contamination.

Heavy metal contents of epiphytic acrocarpous mosses within inhabited sites in Southwest Nigeria

Abstract The levels of the metals Pb, Zn, Cu, Cd, Ni, Mn, and Fe accumulated in acrocarpous mosses within inhabited parts of villages and towns in the southwest region of Nigeria were determined, and then used for a classification of the area into relative pollution zones. Ibadan City was found to be the most polluted in the study area. Other zones of “low” and “medium” polluted villages and towns were identified. The zonations based on metal levels in these mosses were to some extent similar to that already obtained in a separate study of the same area with epiphytic forest mosses. The enrichment factors show that the gradients between zones of different pollution levels were higher in mosses within the inhabited sites.

Comparison of Digestion Methods for Trace Metal Determination in Fish

Abstract The analytical comparison of some digestion methods used for trace metals determination in fish by flame atomic absorption spectrophotometry (AAS) was studied. The results were also compared with those obtained for metals analysis by inductively coupled argon plasma-atomic emission spectrometric technique (ICP[sbnd]AES). Both techniques showed good correlation. The average metal levels found in the fishes and shellfishes analysed from the study area by AAS technique were much lower than the World Health Organisations acceptable limits for metals in foods.

Accumulation patterns of heavy metals in forest mosses from the south-West region of Nigeria

Abstract The accumulated levels of the metals, Pb, Cd, Cu, Ni, Zn, Mn and Fe were determined in forest mosses from south-west Nigeria. Distinct gradients were observed only with Pb and Zn, and a small zone of random contamination with Cu was identified in parts of the east and the south-east. This contamination was possibly a result of the use of copper-based fungicides and pesticides in cocoa farms in the area. The levels of the metals are compared with those in forest mosses in some other parts of the world.

Analytical application of inorganic salt standards and mixed-solvent systems to trace-metal determination in petroleum crudes by atomic-absorption spectrophotometry

The determination of Ni, Cu, Zn, Na, Pb, Cd and Fe in petroleum crudes by means of a toluene-acetic acid mixed-solvent system, inorganic salt standards and atomic-absorption spectrophotometry is presented. The low systematic errors and good burning characteristics of this mixed-solvent system led to its choice. Good recoveries of metals added to petroleum crudes are demonstrated. Coefficients of variation of 8.4 for Ni, 7.0 for Cu, 7.8 for Zn, 11.2 for Na, 9.8 for Pb, 10.2 for Cd and 13.9% for Fe are obtained. The validity of the method is shown by comparison of results obtained with those of an established method.

Determination of traces of phenol in waters by molecular emission cavity analysis

Abstract Tribromophenol is produced from phenol (10 -5 —10 -6 M), filtered off and determined by production of InBr emission at 376 nm in an air—hydrogen—nitrogen flame. Recoveries of 97—99% were obtained from spiked lake water.