Heavy metal contamination of roadside topsoil in Osogbo, Nigeria: its relationship to traffic density and proximity to highways

Abstract

The levels of lead, cadmium, copper, nickel and zinc were determined in the roadside topsoil in Osogbo, Nigeria, with the view to determining the effect of traffic density and vehicular contribution to the soil heavy metal burden. The levels of the metals at the high density roads were significantly higher than the corresponding levels at the medium and low traffic density roads. The average levels of Pb, Cd, Cu, Ni, and Zn in all road locations at a distance of 5 m from the roads were 68.74±34.82, 0.60±0. 31, 21.19±11.34, 8.38±2.40, and 42.45±17.68 mg/kg, respectively. Pb, Cd, and Cu were of average levels of 92.07±21.25, 0.76±0.35 and 27.69 mg/kg, respectively at a distance of 5 m from the road at high traffic density roads, while the levels of Ni and Zn averaged 9.65±2.61 and 56.27±11.58 mg/kg, respectively. There was a rapid decrease in the level of the metals with distance, with the metal levels at a distance of 50 m from the road almost reaching the natural background levels of the metals at the control sites. The levels of the metals were also determined at the four major motor parks and at the seven mechanic workshop settlements. The levels of the metals at the motor parks and mechanic workshops were far above the levels at the control sites. The levels of Pb, Cd, Cu, Ni, and Zn at the motor parks were 519±73.0, 3.6±0.8, 37.9±12.5, 17.3±4.6 and 71.9±11.3 mg/kg, respectively, with the levels of Pb, Cd, Cu, Ni, and Zn at the mechanic workshops averaging 729.57±110.93, 4.59±1.01, 116.6±26.8, 30.21±9.40, and 88.74±28.11 mg/kg, respectively.

An Assessment of Heavy-Metal Contamination in Soils within Auto-Mechanic Workshops Using Enrichment and Contamination Factors with Geoaccumulation Indexes

“…As noted earlier, the very few studies were based on top 0 -15 cm soil depth. Apart from Pb which was found within the range reported [17], mean concentrations of all the other metals were above levels recorded in literature [3] [28]. …”

Accumulation of heavy metals inAzadiractha indicafrom Akungba-Akoko, Nigeria

“…These high values of correlation coefficients further show that the metals could have probably emanated from common anthropogenic sources. In comparison with data from investigations conducted in other parts of South West (Nigeria), the levels of Cd, Cu, Pb, and Zn obtained in our study were lower than those of Ikeja soils [10] but comparable to those of Osogbo soils [11]. Heavier road traffic coupled with several industrial activities and presence of two airports would probably explain the higher metal burdens in the Ikeja soils.…”

“…Automobiles constitute a major source of environmental pollution in roadside soil and vegetation [1][2][3][4][5][6][7]. In Nigeria, most of the investigations [8][9][10][11][12] have been largely confined to urban areas, with minimal information about the status of pollution in the rural areas.…”

Assessment of Heavy Metal Contamination in Roadside Soils Along the Shenyang-Dalian Highway in Liaoning Province, China

“…As shown in Table 3, the mean Pb concentrations in the five cities in 1999 were below or slightly above the background values, indicating that the [33]. Traffic density can be characterized as follows [35]: low traffic -less than 250 vehicles per hour, medium traffic -250-1,500 vehicles per hour, and high traffic -more than 1,500 vehicles per hour. According to this classification, the traffic in Shenyang-Dalian Highway in 2007 was medium, and in 2013 heavy.…”