BEHAVIOUR OF MICROPOLLUTANTS IN SOILS AND THEIR INTERACTIONS WITH SOIL CONSTITUENTS IN THE VICINITY OF DYE PITS, ZARIA CITY, NIGERIA
BEHAVIOUR OF MICROPOLLUTANTS IN SOILS AND THEIR INTERACTIONS WITH SOIL CONSTITUENTS IN THE VICINITY OF DYE PITS, ZARIA CITY, NIGERIA
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Date
2015-03
Authors
RAMADAN, Murshida Adejoke
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Abstract
The behaviour of micropollutants in soil and their interactions with soil constituents was investigated under the influence of textile dye waste pits in Zaria city. A total of 90 soil samples were collected from six different dye sites. The physicochemical properties were analyzed by on standard analytical procedures. The soil microbial biomass carbon and nitrogen was estimated by the chloroform fumigation method, colony count was used for microbial enumeration, while the distribution of lead, cadmium, copper and chromium was determined after triple acid digestion. The sequential extraction procedure was used to fractionate the soil into six operationally defined species. The pH of the contaminated samples ranged from 8.59-9.98 which indicate alkalinity. Organic carbon ranged from 0.29 – 0.58 g/kg, total nitrogen ranged from 0.10 – 0.16 g/kg, available phosphorus ranged from 8.10 - 12.24 g/kg. Microbial biomass carbon and nitrogen ranged from 170.82 - 334.44 mg/kg, and 16.89 - 37.28 mg/kg respectively. Microbial enumeration showed the abundance of bacterial and fungal counts, this is an indication that soils with the highest alkalinity level had the lowest MBC, MBN, bacterial and fungal counts. The dominant genera of bacterial and fungal counts were Bacillus and Aspergillus. Total concentrations of Lead, Chromium and Cadmium recorded maximum values of 181.57, 228.57 and 40.55 mg kg-1, respectively. However, the concentration of Copper was within acceptable limit of 63 mg kg-1 whereas concentrations of Pb, Cd, and Cr were above the threshold levels (70, 6.4 and1.4 mg kg-1). No uniform trend was observed horizontally, although, metal concentrations increased down the soil profile; these were attributed to facilitated transport and ground-water enrichment. Speciation of the heavy metals constituted that 50-80% of the metals that were associated with the resistant soil fraction; thus represent heavy metals held in the crystal lattices of minerals with strong bindings affinity and consequently are not
easily released into the environment. However, the effect of chemicals in the dye effluent, under the influence of pH, could release these metals into the soil-exchange site thereby increasing the concentrations of labile Cd, Cr and Pb in soils and consequently aggravate the potential hazard for the redistribution and subsequent translocation of these metals into the food chain and aquifer. It can be concluded that soil from the dye pits in Zaria city are highly coloured, foul smelling, alkaline in nature and contained trace metal ions where concentrations were higher than minimum allowable contaminant levels. The effluents from the dye areas were the major source of pollutants impacting on the soil properties in the study area. Thus, there is need for treatment of dye effluent by the dyers before discharge into the environment.
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A THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES, AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL FULFILMENT OF THE REQIREMENTS FOR THE AWARD OF A MASTER DEGREE IN BIOLOGY.
Keywords
BEHAVIOUR,, MICROPOLLUTANTS,, SOILS,, INTERACTIONS,, SOIL CONSTITUENTS,, VICINITY,, DYE PITS,, ZARIA CITY,, NIGERIA