EFFECT OF LANDUSE TYPES ON GEOCHEMISTRY OF SOIL IN THE NORTHERN GUINEA SAVANNA OF NIGERIA

EFFECT OF LANDUSE TYPES ON GEOCHEMISTRY OF SOIL IN THE NORTHERN GUINEA SAVANNA OF NIGERIA

Abstract:

Evaluating the distribution (species and concentration) of chemical elements in the biosphere (rock, soil, water, plants, and air) and the study of chemical processes and reactions that govern the composition of and chemical flux between various states is essential in determining the fate and transport characteristics of elements, as well serving as an important facet of understanding the urban environment. Forty samples from surface soils (0 – 20cm) and profile pit were collected to evaluate the anthropogenic (human activities) and pedological (parent material) factor that influenced the natural abundance, distribution and behavior of Cu, Fe, Mn, Pb, Zn and Ti under four different land use (Pasture field, fertilized cropland, vegetable garden treated with municipal waste and forest land) in Zaria and Afaka, Northern Guinea Savanna of Nigeria. Soil pHwas slightly acidic. Sabo vegetable garden soil had the highest pH which is similar to Afaka forest while fertilized IAR farm though similar to NAPRI pasture field had the least. Exchangeable Ca was highest at Sabo vegetable garden which was not different from NAPRI pasture and fertilized IAR farm while Afaka forest had the least Ca content. Trend for Mg concentration is NAPRI pasture field > fertilized IAR farm > Sabo vegetable garden > Afaka forest. CEC values were lowest for Afaka forest and highest for Sabo vegetable garden with relatively higher values for fertilized IAR farm and NAPRI pasture field. Afaka forest had the highest OC and fertilized IAR farm had the least while NAPRI pasture field and Sabo vegetable garden had similar values. X-ray florescence spectrometry of the trace elements revealed that the concentration of these elements were lower than their common range in soil (WHO/Lindsay 1979) Pb (0.0 – 4400mg/kg), Ti (1580 – 2590mg/kg),Cu (40 – 50mg/kg), Fe (6180 – 23050mg/kg), Mn (10 – 90mg/kg) and Zn (0.0 – 40mg/kg),Assessment of contamination using contamination factor (Cf) and geo accumulation index (Igeo) showed no evidence of contamination by the studied elements. Enrichment factor (EF) revealed that the elements originated from natural source. Geochemical balance (%) indicated depletion of most of the elements across the locations while Cu, Mn, Fe and Pb accumulation in some locations indicated high concentration of these metals in the localized parent material. Correlation matrix for NAPRI soil showed significant relationship between all the trace elements and pH, OC, Fed,Ald and Alo while clay correlated with Fe, Zn correlated Ti and Feo. In fertilized IAR farm, OC correlated with all trace elements, pH with Pb, clay and Fed with Mn, Pb, Zn and Ti, Feo with all elements except Pb and Zn, Ald with all element while Alo with Mn and Ti. In Sabo vegetable garden, the elements correlated with each other and with clay, pH, Fed, Feo and Alo, OC correlated with only Pb, Zn and Ti while Ald correlated only with Zn. Afaka forest revealed significant inter-element correlation as well as correlation of the metals with free Fe and Al oxides, OC correlated with Cu, Mn and Ti, clay with Fe, Pb and Ti while pH with Fe and Pb. Zn did not correlate with any of the elements and soil properties. Factor analysis for the different land use showed that the studied elements though be influenced by different pedogenic processes are of similar origin. Clay mineralogy of the soils revealed that NAPRI pasture field was dominated by 2:1 non-expanding clay mineral with traces of 1:1 clays, fertilized IAR farm had a wide variation of minerals, Sabo vegetable garden had 2:1 clay mineral dominating the surface horizon while the subsurface horizon is dominated by hematite. The mineralogy of Afaka forest is dominated by hematite at the surface horizon while 1:1 clay dominated the subsurface horizon

EFFECT OF LANDUSE TYPES ON GEOCHEMISTRY OF SOIL IN THE NORTHERN GUINEA SAVANNA OF NIGERIA