Heavy Metals in Soils and Road Dusts in Akure City, Southwest Nigeria: Ecological and Health Risks

10 Expanded urbanization particularly in developing nations have as of late become a 11 significant source of worry because of their adverse consequences on the environment. This 12 study was conducted to determine the extent of pollution, sources, and potential ecological 13 and health risks associated with heavy metals in Akure region, Nigeria's soils and street dusts. 14 Thirty-four samples including 16 soils and street dusts samples each were gathered with two 15 control samples gathered from a suburb a long way from the city. To collect fine particles, 16 they were air dried and sieved. Chemical analysis of samples werecarried out utilizing 17 Atomic Absorption Spectrometer (AAS) at Sustainable laboratory, a certified laboratory in 18 Akure, Nigeria. Metals analysed were: As, Cd, Co, Cr, Cu, Ni, Pb, Zn and Fe. Contamination, 19 ecological and health hazard evaluations were carried out utilizing universally acceptable 20 indices. Potential sources were disentangle utilizing measurable technique like bivariate, 21 factor and hierarchical cluster analyses. Results uncovered that the mean amount of Pb, Zn 22 and Fe in street dusts were: 32.33 mg/kg, 72.53 mg/kg, and 115.21 mg/kg separately while in 23 soil tests it was 34.34 mg/kg, 67.76 mg/kg, and 115.21 mg/kg. The examination further 24 showed that metals particularly Cr present slight to high ecological dangers. Health hazard 25 evaluation uncovered that the occupants of the area particularly kids are more inclined to 26 non-cancer-causing health risks. Metals were mostly from anthropogenic sources. To reduce 27 the impact of toxic metals in the city, it is proposed that ecological enactment and mindfulness be practiced..


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Soil is a fundamental natural resource on account of its capacity to go about as a Global Positioning System (GPS). Street dusts were gathered along significant roads and 106 created street side asphalts in the city. They were gathered with a brush on a spotless parker.

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Up to 5kg composite of each example were gathered on each road side. Samples were set in a 108 perfect all around named ziplock sack. Prior to inspecting, the hand scoop was entirely 109 washed with refined water and permitted to dry before the following sample is taken.

Geo-accumulation index (Igeo)
139 The geo-accumulation index (Igeo) was developed to evaluate metal enrichment 140 above baseline values in order to determine contamination of a specific metal in soils.

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Equation 1 was used to calculate Igeo (Muller, 1969    The Contamination Degree is Cd, while the Contamination Factor is CF.

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6 is used to calculate ER.
The toxic-response factor is Tr, while the single-element pollution factor is CF. The

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Equation 7 (Wang et al., 2015) can be used to express it: where ER denotes a single element's potential ecological risk. The following are the RI  C is the concentration of heavy metal in mg/kg for soil/dust, and ADIing is the average daily 207 intake of heavy metals eaten from soil in mg/kg-day. The intake rate is measured in 208 milligrams per day. The exposure frequency is measured in days per year. The exposure 209 duration (ED) is measured in years. BW is the exposed person's body weight in kilograms.

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The time period over which the dose is averaged in days is referred to as AT. The conversion 211 factor in kg/mg is CF (Supplementary 1).

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Equation 9 shows the average daily intake of heavy metals by soil breathing.
Where ADIdems is the exposure dosage in mg/kg/day by dermal contact. The heavy metal 223 concentration in soil is measured in milligrams per kilogram (mg/kg). The exposed skin area 224 (SA) is measured in square centimeters (cm 2 ). The percentage of the dermal exposure ratio in 225 soil is called FE. The soil adherence factor (AF) is measured in milligrams per square meter.

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The proportion of the dermal dosage absorbed over the skin is referred to as ABS. Equation 9 227 defines the terms EF, ED, BW, CF, and AT. The exposure parameters utilized for the health 228 risk assessment for a standard home exposure scenario along several exposure paths are 229 shown in supplementary 1.

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The hazard quotient is a concept used to describe non-carcinogenic dangers (HQ). The The Hazard index (HI) is a word used by the USEPA to describe the sum of all HQs (1989).

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The mathematical expression of HI is Equation 12.
The values of heavy metal k are HQk, ADIk, and RfDk (Supplementary 2). The exposed 239 population is unlikely to suffer negative health impacts if the HI value is less than one. If the 240 HI value is more than one, there may be cause for concern about non-carcinogenic effects 241 (USEPA, 1989).   Where Risk(ing), Risk(inh), and Risk(dermal) denote risk contributions by ingesting, 253 inhalation, and dermal routes, respectively. 254

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Supplementary 3 shows the percentage particle size distribution of soil and road dust 257 samples taken from the research area.   The average daily intake (ADI) for heavy metals in soils and road dusts in children 320 and adults for non-carcinogenic diseases are shown in Figure 5. Figure 5 showed that the total 321 daily heavy metal intake from soil via ingestion, dermal contact and inhalation for non-  Figure 5 depicts the average daily intake (ADI) of heavy metals in soils and road 329 dusts in children and adults with non-carcinogenic disorders. Figure 5 shows that for non-  Figure 5 shows the average daily intake (ADI) of heavy metals in soils and road dusts 345 for carcinogenic illnesses in children and adults. Figure 5 shows the total daily heavy metal 346 intake from soil for carcinogenic disorders in children by eating, cutaneous contact, and 347 inhalation

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The hazard quotient (HQ) and hazard index (HI) for heavy metals in soils and road 384 dusts in children and adults for carcinogenic diseases are presented in Figure 6. Figure 6 385 showed that the total HQ and HI for heavy metals in soil via ingestion, dermal contact and 386 inhalation for carcinogenic diseases in children are: As: 2.80E-5; Cd: 4.99E-10; Co: 1.13E-9; 387 Cr: 2.80E-5; Pb: 3.19E-6. The total HI is 4.19E-05.

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The concentrations of As and Cr in the area's soils and road dusts were found to be 428 higher than the USEPA (2002) standard and the background sample (Table 1)

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According to the geo-accumulation index proposed by Muller (1969), the soils of

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Akure are unpolluted to moderately contaminated by As, Co, Cr, Cu, Pb, Zn, and Fe, but 486 moderately-heavily polluted by Cd and Ni. Co, Cu, Pb, and Fe were unpolluted to moderately 487 polluted in road dusts from this location, while As and Zn were moderately to moderately-488 heavily polluted (Table 3). They were moderately to heavily contaminated with Cd and Cr.

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The enrichment factor is a measurement of how much of a given element is found in the  (Table 3). Also, Cr showed a low to 499 considerable degree of contamination while Ni posed a low to very high degree of 500 contamination. The study further revealed that Cd poses a moderate to very high 501 contamination. For road dusts in the area, Cd and Cr pose very high contamination while As 502 caused considerable to very high contamination. Also, Co and Ni caused low to considerable 503 contamination while Cu, Pb, Zn and Fe pose moderate to considerable contamination (Table   504 3). Heavy metals in the soils of the area, according to Hakanson (1980), pose a moderate to  (Table 3). This 508 further showed that the area is been detoriated by these potentially toxic metals. Enrichment study showed that children bioaccumulate more heavy metals than adults from both soils and 574 road dusts ( Figure 5). In this study, it was observed that health quotients (HQ) for Co and Pb 575 for both soils and road dusts were above >1 for children as suggested by USEPA (2008) 576 ( Figure 6). The hazard index (HI) for non-carcinogenic health concerns from dusts was larger 577 than 1 for both children and adults, whereas the HI for heavy metals in soils was greater than 578 1 for both children and adults ( Figure 6). Study in Nigeria revealed that prenatal burden exposure to Pb through maternal blood and 603 cord was higher than 10 ug/dl (Obi et al. 2014) and this has been linked to miscarriages in

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The contamination of the environment, which is exacerbated by increased human presence of heavy metals, particularly Cd, may represent a harm to the environment, 628 according to an ecological risk assessment. The city's residents are more susceptible to non-629 carcinogenic health risks than carcinogenic health risks, according to a risk assessment.

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Children are also more exposed to non-carcinogenic health concerns than adults, according to Mean ADIs for non-carcinogenic and carcinogenic health risks of potentially toxic metals in soils and dusts in the study area Average hazard quotient (HQ) and hazard index (HI) for non-carcinogenic and carcinogenic health risks of potentially toxic metals in soils and dusts in the study area Supplementarydata.docx