Assessment and Distribution of Metal Pollutants in Fadama Soils along River Ngadda and Alau Dam in Maiduguri, Borno State, Nigeria

Elemental metal pollutants concentration levels and their distribution in soils obtained from farmlands along the bank of river Ngadda and Alau dam in Maiduguri, BornoState, and North-East of Nigeria is presented.  The  study  was  aimed  at  determining  the  levels  of  contamination  of  soils  with  metal pollutants used for fadama farming along the bank of river Ngadda and Alau dam with the objectives of assessing the contamination levels of the soils with metal pollutants from the various farmlands at the various sampled sites of study, and the distribution of the various metal pollutant in the various sampled sites. Soil samples were collected from thirteen different sites on the farmlands along the bank of the river and  the  dam.  The samples were analyzed using Instrumental  Neutron  Activation Analysis (INAA) and the result obtained indicate that the concentration level of some of the elements determined were above maximum allowable concentration (MAC) value while some below the (MAC) values for example the concentration range for Cr was (16 ± 2 –47 ±3) ppm, Sb was (0.18 ± 0.04 –14.2 ± 7) ppm, Zn was (21.8 ± 4 –145 ± 7) ppm and the maximum values for these ranges exceed the (MAC) value recommended for Agricultural soils while the concentration ranges for As was (0.46 ± 0.12 –1.0 ± 0.2)ppm, Co was (1.6 ± 0.3 –5.3 ± 0.4) ppm, Vn was (14.6 ± 2.32 –29 ± 2) ppm with the maximum value for these ranges being below the MAC values given by some countries. The elements obtained from samples collected from different study areas along the bank of river Ngadda and Alau dam  were  analyzed  for  similarity  distribution    of  the  study  area  using  mathematical  tool  of  cluster analysis technique employing hierarchical procedure and using WARD’s method. The result obtained produce a dendrogram consisting of two clusters comprising of six and seven sites with percentage similarity of 96.5% and 90.8% respectively with one site as an outlier. It is recommended that since some  of  the  trace  metals  namely  Cr,  Sb,  and  Zn  assessed  in  the  fadama  soils  indicates concentrations above the MAC values, they can posed negative health implications to consumers of food which were cultivated on soils from the study area, therefore there is the need to condition the soils before using it  for farming so as to make it suitable for food  crop farming.  From the results obtained from this and presented, it can be clearly observed that the concentrations of some of the toxic  trace  elements  analyzed  and  determined  in  this  research  were  found  to  be  above  the  MAC values given by some countries for soils to be used for agricultural purposes while others were within the range of the MAC values and some were below the limit given by some countries. However, even for soil samples that were having concentration below the MAC values since the soils were used for agricultural purposes it will be of great importance that such studies and investigations on such soils be carried out periodically so as to ascertain and monitor the levels of this metal toxicants and where the level of metal pollutants were above the MAC values there is the need to conditioned the soils so as to remedy the concentration of the pollutants before using the soils for agricultural purposes since the  plants  may  absorb  these  metal  toxicants  and  it  will  accumulate  above  threshold  level  thereby causing negative effect on the use of the soils.

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