Environmental Challenges (Dec 2021)
Variations in reference values utilized for the evaluation of complex pollution indices of potentially toxic elements: A critical review
Abstract
The study provides a critical evaluation of different background values commonly utilized in assessing the complex pollution indices (CPI) of potentially toxic elements in environmental components. Contamination indices offer helpful information about the health and quality status of various ecological systems. In this study, twelve CPI were studied, with eight indirectly requiring background values for computation (sum of pollution index, pollution load index, average pollution index, vector modulus of pollution index, background enrichment factor, potential ecological risk index, degree of contamination, nemerow pollution index), while the other four which do not require background values for computation (contamination security index, multi-element contamination degree, exposure factor, probability of toxicity), were used to assess the ecological effects of copper, zinc, manganese, lead, chromium and nickel in soil. Analysis of the indices that required reference values for computation showed significant variations in mean values, except for median mean (MM) and geometric mean (GM) consideration that showed no significant differences. The values of GM and MM showed high statistical similarity using Ward's hierarchical cluster analysis (HCA) and Pearson Correlation as compared to other background values. Furthermore, the reliability analysis revealed that combined background values provide a better tool for assessing environmental components, with a Cronbach's Alpha of 0.811. Another effective approach for risk assessment was observed with calculations involving the use of control values, showing a Cronbach's Alpha of 0.747. Of all the background values evaluated, the reliability index depicted the potential ecological risk index as the most crucial for assessing ecological risk, with a Cronbach's Alpha range of 0.881 – 0.905 when an item is deleted. Therefore, we recommend the utilization of control values as background concentration, whilst potential ecological risk index should be strongly considered for the environmental risk assessment of trace metal micro-pollutants.
