Publisher: Chemical Society of Nigeria

Influence of Herbicides On The Concentration of Some Selected Heavy Metals On Farmlands At Ibaji, Kogi State Nigeria.

E. Okorie, M. Acheneje, C. N. Omego, E. F. Chibugo
KEYWORDS: Herbicides, heavy metals, FAAS, soot, soil.

ABSTRACT:

The  influence  of  herbicide applications  on  the  presence  of  some  heavy  metals  on farmlands  in Ibaji,  Kogi State  was  investigated  using  flame  atomic  absorption  spectrometer.  Results  of  this  study  showed  that there  was  a  significant  increase  in  the  concentration  of  Cd,  Cr,  Cu  and  Pb  in  areas  where  herbicides application  is  in  use.  The  concentration  range  of  Cu,  Cd,  Cr  and  Pb  in  the  HTHPF  are  253.6±3.3  mg/Kg –329.5±2.4  mg/Kg  (Cu),  2.2±0.9  mg/Kg  –  21.2±0.7  mg/Kg  (Cd),  74.5±2.2  mg/Kg  –  153.7±  1.3mg/Kg (Cr)  and  0  –  126.9±1.4  mg/Kg  (Pb),  while  the  concentration  range  for  NHTF  are  135.6±2.7  mg/Kg    - 214.7±  2.9  mg/Kg(Cu),  0  –  12.6±1.1  mg/Kg  (Cd),  53.5±5.2  mg/Kg  –  114.2±1.1  mg/Kg  (Cr)  and  0  – 33.1±2.2  mg/Kg  (Pb).  A  variation in  the  distribution  of  these  metals  at  various  depths  was  also  observed. Cu  and  Cd  in  HTHPF  increased  with  an  increase  in  depth.  However,  no  Cd  was  observed at  depth  10  cm and  20  cm.  Cr  concentration  followed  a  downward  trend  from  153.7±1.3  mg/Kg  (topsoil)  to  74.5±2.2 mg/Kg  (15  cm),  but  increased  sharply  at  20  cm  depth  to  127.0±2.1mg/Kg.  The  concentration  of  Pb increased  from  42.0±2.9  mg/Kg  (topsoil)  to  49.2±1.5  mg/Kg  (5  cm)  and  decreased  from  126.9±1.4  (15 cm)  to  78.9±1.1  (20  cm).  At  10  cm  depth,  Pb  was  not  detected.  For  the  NHTF,  the  concentration  of  Cu are  135.6±2.7 mg/Kg (topsoil), 159.6±2.4 mg/Kg (5 cm), 182.6±1.6 mg/Kg (10 cm), 214.7±2.9 mg/Kg (15 cm)  and  213.9±3.8  mg/Kg  (20  cm).  Cd  was  not  detected  at  topsoil,  15  cm  and  20  cm  but  was  observed  at 5  cm  depth  (12.6±1.1  mg/Kg)  and  10  cm  depth  (0.60±1.8  mg/Kg).  Cr  decreased  gradually  as  the  depths increased  from  114.2±1.1  mg/kg  (topsoil),  79.2±3.2  mg/Kg  (5  cm),  73.8±1.5  mg/Kg  (10  cm),  57.0±2.2 mg/Kg (15 cm)  and 53.5±5.2 mg/Kg (20 cm). No Pb was observed from  topsoil  through 15  cm depths, but was  detected  at  20  cm  depth  (33.1±2.2  mg/Kg).Other  anthropogenic  sources  of  these  metals  were  also considered  with  increases  in  their  concentration  as  a  result  of  soot  discharge  from  exhaust  of  diesel powered  automobiles.  This  increase in  concentrations  of  these  metals  as  a  result  of  herbicide  application was  attributed  to  binding  thereby  increasing  the  metal-herbicide  association.  This  herbicide  use  may accumulate these  metals  in  the  soil  and eventually  lead  to  land  pollution  and  bioaccumulation  as  a  result of plant uptake. 


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