Heavy metals in road deposited sediments and road dusts of Colombo Capital, Sri Lanka

Abstract

Road deposited sediment (RDS) and road dust analyses are useful techniques to understand the heavy metal (HM) pollution in an urban area. Therefore, this study focused on the chemical characteristics of RDS and road dust in order to evaluate the pollution conditions in the Colombo Metropolitan Region (CMR) in terms of HMs. Forty six (46) RDS samples and forty eight (48) road dust samples were collected, and elemental concentrations of Zn, Cu, Pb, Fe, Mn and Cr were determined. Out of these measured elements, the most abundant element in all the samples was Fe, which is a common element in the basement lateritic soil in the area. Cu, Pb, Fe and Cr concentrations in RDS are high in industrial areas, while Zn and Mn are high in commercial areas. Except Fe, all the other element levels were higher in road dust than in RDS. Data analysis revealed that vehicle-related activities are the dominant source for the metals in the city. Zn, Cu, Mn and Fe contents were significantly higher than the background levels of the area. Statistical analysis reconfirms that road dust is more polluted than RDS in terms of Zn and Cu. According to the geoaccumulation index, road dust is moderate to strongly polluted and RDS are moderately polluted. Higher pollution conditions of road dust may be due to the resuspension of dust particles. Spatial distribution patterns show that HMs of anthropogenic origin were accumulated towards the North and Northwestern parts where the transportation related activities are centered in the CMR. However, the prevailing natural conditions such as wind direction, geomorphology and basement soil also control the level of contamination in the area.

An Urban Heat Island Study of the Colombo Metropolitan Area, Sri Lanka, Based on Landsat Data (1997–2017)

“…The average annual rainfall is 2300 mm. The mean annual temperature is approximately 28 • C [33]. January is the warmest and driest month of the year [31].…”

Spatial Changes of Urban Heat Island Formation in the Colombo District, Sri Lanka: Implications for Sustainability Planning

“…Hence, the period from December to early March can be considered as a dry period of the study area. The average annual rainfall is 2300 mm [4], and the mean annual temperature is approximately 28 • C [37]. Mean daily sunshine varies from 9 h in February to 5 h in June [38].…”

Assessment of pollution in roadside soils by using multivariate statistical techniques and contamination indices

“…where Cs and Cb are the contents of HMs in the samples and background environment, and the constant 1.5 represents the feasible alterations in the reference values of heavy metals because of lithogenic effects in the soil. The grades for classifying the level of contamination are Igeo ≤ no contamination, unpolluted to average contamination (0-1), average to contamination (1-2), average to strong contamination (2-3), maximum contamination (3-4), high to very contamination (4-5) and very high contamination (5). The Enrichment factor (EF %) was calculated by applying the equation suggested by Zonta et al [34]:…”

“…However due to the rapid urbanization, industrialization and extensive application of fertilizers and pesticides leads to contamination of soil health [2][3][4]. Transportation service is a significant pollution source of heavy metals in surroundings soils near the highways, which are produced by vehicles and dust, entering the soil through natural sedimentation [5,6]. HMs may be harmful to humans and other living organisms due to their toxicity, perseverance, nonbiodegradable and non-thermodegradable properties [7].…”