Assessment Of Heavy Metals And Polycyclic Aromatic Hydrocarbons In Water, Fish And Sediments Of Rivers Niger And Benue Confluence, In Lokoja, Kogi State, Central Nigeria.

ABSTRACT

The concentration of six heavy metals and six of sixteen (16) US EPA priority polycyclic aromatic

hydrocarbons (PAHs) in water, fish and sediment samples of the confluence of rivers Niger and

Benue were investigated in triplicates using atomic absorption spectrophotometer (AAS) for the

heavy metals determination and gas chromatography coupled with mass spectrometer detector for

the PAHs after acid digestion of the samples for heavy metals,liquid-liquid and solid-liquid

extraction for the PAHs samples. The heavy metals were profiled for dry and rainy seasons whereas,

the PAHs concentration in the samples were profiled for only rainy season in five sample locations.

The concentration of the metals in water across the locations ranged from Cd (0.038 to 0.089),

Cr(0.106 to 0.240), Cu(0.092 to 0.0164), Fe(0.682 to 0.878), Pb(0.058 to 0.309) mg/L with

distribution pattern of Zn>Fe>Pb>Cr>Cu>Cd for the dry season water samples and Cd(ND to

0.027), Cr(ND), Cu(ND to 0.021), Fe(2.236 to 13.634), Pb(0.119 to 0.205) and Zn(0.121to 0.216)

mg/L with distribution patter of Fe>Zn>Pb>Cd>Cu>Cr during the rainy season.The sediments’

metals concentration across locations ranged from Cd(2.189 to 2.893), Cr(4.367 to 9.927),

Cu(3.433 to 6.780), Fe(233.210 to 254.160), Pb(8.967 to 17.420) and Zn(6.027 to 20.380) mg/kg

with distribution pattern of Fe>Zn>Pb>Cr>Cu>Cd during the dry season and Cd (0.321 to 1.024),

Cr(0.456 to2.662), Cu(ND to 8.599), Fe(1.234 to 2.062), Pb(8.721 to 17.737) and Zn(12.350 to

66.343)mg/kg with distribution pattern of Zn>Pb>Cu>Cr>Fe>Cd for the rainy season samples.The

mean concentration of the metals in Catfishduringthe dry and rainy seasons were Cd(3.367 and

0.666) Cr(- and 0.293), Cu(7.050 and 4.952), Fe(44.775 and 1.230), Pb(3.842 and 8.683) and

Zn(63.625 and 85.266)mg/kg and the Tilapia mean concentration values for dry and rainy seasons

were as follows Cd(4.850 and 0.453), Cr(- and 0.164), Cu(8.042 and 1.658), Fe(44.108 and 0.198),

Pb(4.717 and 6.704), Zn(63.742 and 40.680) mg/kg.The concentrations of the PAHs in water across

locations ranged from Nap(ND to 0.543), Ph(ND to 0.083) Ant (ND to 0.083), BbF(0.080 to 0.093),

BkF(0,083 to 0.093) and BaP(0.083 to 0.113) mg/L with distribution pattern of

Nap>BaP>BbF=BkF>Ant=Ph.The concentration of PAHs in sediment across the locations ranged

as follows Nap(ND to 2.210), Ph(ND to 0.053), Ant(ND to 0.053), BbF(0.053 to 0.383), BkF(0.053

to 0.110) and BaP(ND to 0.053)mg/kg with distribution pattern of

Nap>BbF>BkF>Ph=Ant=Bap.The mean concentration value of PAHs in Catfish and Tilapia were

Nap(2.383 and 1.947), Ph(0.050 and 0.057), Ant(0.057 and 0.057), BbF(0.043 and ND), BkF(0.043

and ND) and BaP(0.050 and ND).The result of the heavy metals in water and fish samples were

tested for non-carcinogenic and carcinogenic health risk using health risk assessment models such

as hazard quotient (HQ), Total hazard index(THI) cancer risk(CR) and cancer risk index(CRI). The

health risk assessment showed that Cd andPb are of great concern.The ecological risk factors for

the concentration of heavy metal and PAHs in sediment were estimated using ecological risk models

such as geo-accumulation index (I-geo), contamination factor (CF), single ecological risk factor(ER),

ecological risk index (RI), pollution load index (PLI) and polycyclic aromatic hydrocarbons

pollution index (PPI).The results showed that sediment pollution ranged from no heavy metals

pollution, low risk and very high risk pollution.The heavy metals and PAHs data were subjected to

ANOVA at probability values less than 0.05 (P