Abstract
A good understanding of urban soil contamination with metals and the location of pollution sources due to industrialization and urbanization is important for addressing many environmental problems. The results are reported here of an analysis of the metals content in urban soils samples next toindustrial locations in the Greater Toronto Area (GTA) in Ontario, Canada. Theanalyzed metals are Cr, Mn, Fe, Ni, Cu, Zn, and Pb. Multivariate geostatistcalanalysis (correlation matrix, cluster analysis, principal component analysis) is used to estimate soil chemical content variability. The correlation matrix exhibits a positive correlation with Mn, Fe, Cu, Zn, Cd, and Pb. The principal component analysis (PCA) displays two components. The first component explains the major part of the total variance and is loaded heavily with Cr, Mn, Fe, Zn,and Pb, and the sources are industrial activities and traffic flows. The second component is loaded with Ni, and Cd, and the sources could be lithology andtraffic flow. The results of the cluster analysis demonstrate three major clusters: 1) Mn-Zn, 2) Pb-Cd-Cu and Cr, 3) Fe-Ni. The geo-accumulation index and the pollution load index are determined and show the main I geovalues to be in the range of 0-1.67; the values indicate that the soil samples studied for industrial locations in the GTA are slightly to moderately contaminated with Cr, Fe, Cu, Zn, and Cd, and moderately contaminated with Pb,while Ni, and Mn fall in class 0. Regarding the pollution load ingindex (PLI), the lowest values are observed at stations 6, 7, 9, 10, 11, 12,25, 27 and 28, while the highest values are recorded for stations 1, 5, 6, 13,14, 16, 17, 18, 20, 22 and 24, and very high PLI readings are seen for stations 5, 13, 16, 17, 18, 22 and 24. These data confirm that the type of industries, especially metallurgical and chemical related ones, in the study area, in addition to high traffic flows, are the main sources for soil pollution in the GTA.
Highlights
In recent years, much concern has been expressed over the problem of urban soil contamination with heavy metals due to rapid industrialization and urbanization (SUN et al, 2008).Many studies indicate that urban soils are contaminated by heavy metals, and this phenomenon has been attributed mainly to modern industries, traffic and mining activities in urban areas (NAZZAL et al, 2012, 2014; XIAOYU LI et al, 2013; DE KIMPE & MORAL, 2000; GALLAGHER et al., Geologia Croatica 68/22008)
A comparison of the data shows that the average concentration of the investigated heavy metals in the analyzed soil samples are in many locations, higher than their corresponding values in the average world soils (Table 3)
For Ni and Mn, Igeo falls in class 0, indicating that no pollution from these metals was recognized in the studied samples. These results indicate that the soil samples for the studied industrial locations in the greater Toronto area (GTA) are enriched with potentially toxic metals from anthropogenic sources such as industry and traffic flow
Summary
Much concern has been expressed over the problem of urban soil contamination with heavy metals due to rapid industrialization and urbanization (SUN et al, 2008).Many studies indicate that urban soils are contaminated by heavy metals, and this phenomenon has been attributed mainly to modern industries, traffic and mining activities in urban areas (NAZZAL et al, 2012, 2014; XIAOYU LI et al, 2013; DE KIMPE & MORAL, 2000; GALLAGHER et al., Geologia Croatica 68/22008). A trend has been noted towards higher concentrations of heavy metals on streets where traffic is more likely to undergo stop-start operations, e.g., at traffic lights (AKHTER & MADANY, 1993; ELLIS & REVITT, 1982; FERGUSSON et al, 1980); DYKE et al, 1989; JOHNSTON et al, 1985; HAMILTON et al, 1984; HOWARI & BANAT, 2001; ABU-RUKAH, 2002; WEI & YANG, 2010; WEI et al, 2009; DAO et al, 2010; MORTON-BERMEA et al, 2009) Most of these studies indicate that metal deposition peaks closest to the roadside and diminishes rapidly with increasing distance from the road
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