Perspectives of heavy metal pollution indices for soil, sediment, and water pollution evaluation: an insight

Abstract

The paper reviews the widely used heavy metal pollution indices (HPIs) in water, soil, and sediments and presents their numerical equation and application in various fields. HPIs are an essential and efficient tool to measure metal contamination in the environmental system. The present study includes twenty pollution indices from water, soil, and sediments for their comparative study with their ranges. In addition, the regional distribution of publications has been reviewed, and it observed that 68% were published from Asia, followed by other continents. The merits and demerits of each index have been presented, and a comprehensive method for selecting the appropriate pollution index is evaluated in order to better interpret the pollution level in soils and water systems. Among water quality indices HPI, HEI and HI have been used widely due to precise scale, easy to use, less limitations and provide efficient results. Among single indices, EF, Igeo, and CF are widely used and can be used in a simple manner for soil quality assessment, whereas in combined indices PLI and INemerow are found to be useful as it is easy to apply and have precise scale. In integrated indices, Cd and IAvg are found to be useful as it is easy to apply, and there is no limitation for heavy metals. Selection of appropriate geochemical background (GB) must be established, and the nature of fluctuation in GB may give a false result. The ecological risk index (ERI) is a unique index used to represent the ecological risk of metal pollution in water, soil, and sediment systems. A comprehensive approach and guidelines for using metal pollution indices in soil and sediment considering different sectors may be developed for each nation. The widespread application of HPI makes the study more accessible, and a well-defined result can be presented.