Bioscience Methods 2017, Vol.8, No.1, 1-17
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1980; Sutherland, 2000; Tijani et al., 2004; Yu et al., 2004; Qingjie et al., 2008; Wang et al., 2010, 2016; Liang et
al., 2011; Suresh et al., 2011; Yang et al. 2011; Sarala and Sabitha, 2012; Zhu et al., 2012; Fiori et al., 2013;
Swarnalatha et al., 2013; Elias et al., 2014; Jiang et al., 2014; Singovszka et al., 2014; Tang et al., 2014; Uriah and
Shehu, 2014; Vowotor et al, 2014; Al-Anbari et al., 2015; Ghaleno et al., 2015; Ghazaryan et al., 2015; Karydas et
al., 2015; Soliman et al., 2015; Hassaan et al., 2016; Mohseni-Bandpei et al., 2016; Todorova et al., 2016;
Bhutiani et al., 2017). But information on pollution load of heavy metals resulting from the discharge of cassava
mill effluents into the soil is scanty in literature. Therefore, this study is aimed at investigating the pollution load
of heavy metals in cassava mill effluents contaminated soil in a rural community in the Niger Delta region of
Nigeria. The study applied several pollution indices viz: contamination factor (CF), contamination degree (CD),
pollution load index (PLI), pollution index (PI), Pollution index/ Contamination Index (PI/CI), Metal pollution
Index (MPI), Sum of pollution index (SPI), Average Pollution Index (API) and Newmerow integrated pollution
index (NIPI). The findings of this study may be useful to environmentalist and policy makers in Nigeria and other
cassava processing countries of the world.
1 Methodology
1.1 Study area
Ndemili Umusadege, Utagba-Uno is one of the communities in Ndokwa-West local government area of Delta
state. Ndemili lies between latitude N06º01’ and longitude E006º17’. Like other regions of the Delta state, the
average annual precipitation of the area is about 1900 mm (Orji and Egboka, 2015). The atmospheric temperature
and relative humidity of the area is approximately 28±6ºC and 50 – 95% respectively all year round. Major
economic activities in the area include farming. Some of the major crops farmed in the area are food crops such as
cassava, yam, maize, oil palm etc (Izah et al., 2017d). The cassava cultivated in the study area are typically
processed into gari (cassava flakes) and Akpu (a food made from slurry of fermented cassava tuber).
1.2 Data source
Secondary data was used for the determination of pollution load indices of heavy metals in cassava mill effluents
contaminated soil. The background mean values (geometric and median mean) and concentration of heavy metals
based on two seasons data from five locations previously reported by Izah et al. (2017d) (Table 1). The values
were used to calculate the pollution load indices based on seasons (viz dry and wet) at the different locations.
1.3 Pollution load assessment model
Pollution by heavy metals has been widely studied using several indices including CF, CD, PLI, PI, PI/CI, MPI,
API, SPI and NIPI. The basis of determining the pollution load is to quantify the extent of heavy metals pollution
by cassava mills effluents in receiving soil in comparison to its natural background. Several mean data have been
recommended/ suggested to be used as natural background reference value for the assessment of pollution load
and ecological risk assessment. Some of these means include geometric mean (BGM) (Thambavani and Uma
Mageswari, 2013; Bhutiani et al., 2017) and median mean (BMM) (Sarala and Sabitha, 2012; Monakhov et al.,
2015; Bhutiani et al., 2017). According to Sarala and Sabitha (2012), the use measures of the central tendency
such as median instead of an arithmetic mean shows the main trend in the index values for management purpose.
Furthermore, BGM and BMM have been applied in determining pollution load in environmental components.
Based on the values presented in Table 1, CF, CD, PLI, PI, PI/CI, MPI, API, SPI and NIPI were calculated and the
resultant values was compared to the criteria presented in Table 2, Table 3a, Table 3b, and Table 4.
