Heavy Metal Contamination of Forest Soils by Vehicular Emissions: Ecological Risks and Effects on Tree Productivity
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Date
2022-01-29
Journal Title
Journal ISSN
Volume Title
Publisher
springer
Abstract
An ecological study was conducted to evaluate the levels and effects of heavy metals
on forest surface soils along highways. We hypothesized that vehicles in highways emit
considerable levels of metals, affecting plant diversity and productivity. Pearson correla-
tion, cluster, and regression analysis were used to prove these relationships. Furthermore,
ecological risk assessments were quantified using the geo-accumulation index, pollution
index, pollution load index, and ecological risk index. Results indicated soil samples from
Site II (roadway) had higher levels of metals than Site I (control), suggesting that highway
traversing via forests emit considerable amounts of metals into the surface soil. The most
intriguing aspect is that species such as Bidens Pilosa and Arundo donax were frequently
recorded at Site II. The predominance of such species indicates contaminated sites favour-
ing metal tolerance species. Ecological risk indices revealed that Cd, Mn, and Pb contrib-
uted to ecological risk; their pollution ranged from unpolluted to heavily polluted ecosys-
tem. Correlation analysis found a pronounced negative link between metals and diversity;
the correlation matrix was −83%, −94%, −65%, −75%, −47%, −57% and − 38% for grass
diversity, and − 59%, −74%, −89%, −66%, −81%, −81% and − 83% for forb diversity with
Cd, Cr, Ni, Pb, Zn, Cu and Mn, respectively. Furthermore, negative correlations for tree
production of −80%, −79%, −76%, −71%, −67%, −53% and − 41% were recorded with
Cd, Cr, Ni, Pb, Zn, Cu and Mn, respectively. Nevertheless, metals accounted for 74% vari-
ance in tree productivity. The strong negative link observed in this study demonstrates the
effects of metals on diversity and productivity, which requires monitoring for preventing
serious environmental consequences.
Highlights
• Excessive road traffic contributes to the release of heavy metal in forests.
• Heavy metals in surface soils threaten plant diversity and productivity.
• Cd, Mn and Pb are the most substantial contributors to ecological risks.
Description
This article was published by Springer in 2022