Application of pollution indices for the assessment of heavy metal hazards in soil using GIS approach

Abstract

The current research focuses on the identification of heavy metals’ intensity in the soil and their spatial distribution along the Hudiara drain through different pollutant indices using Geographical Information System (GIS) techniques. A total of 27 soil samples (in nine transects) were collected through GIS-based equidistant sampling along the drain and its 1-km buffer for Fe, Mn, Zn, Pb, Cr, Cu, Co, Cd, and As elements. Numerous soil pollution indices like contamination enrichment factor (EF), geo-accumulation index (Igeo), summary pollution index (Zc), pollution load index (PLI), potential ecological risk factor (RI), and potential ecological risk factor for single metal ( $$ {E}_r^i $$ ) have been calculated individually in a spatial domain. All these soil indices were combined in spatial overlay analysis to delineate potential soil pollutant sites and sources. The mean value of heavy metals found in the soil in the drain vicinity can be arranged in decreasing order as Fe > Mn > Zn > Pb > Cr > Cu > Co > Cd > As. The spatial distribution maps of heavy metal concentration and soil pollution indices revealed that most of the extremely polluted region existed close to industrial and residential sites along the Hudiara drain. Similarly, spatial overlay analysis based on the developed soil indices also suggested the highly polluted soil area mostly dominated by industrial or anthropogenic activities. These results highlighted the possibilities of seepage/percolation of the drain’s industrial effluents into surrounding soil and aquifer. The situation would not only deteriorate the local environment but also put the health of local residents at high risk. The study recommends the pretreatment of industrial and municipal effluents particularly regarding heavy metals before directly discharging into the drain to avoid further deterioration. The study also encourages the establishment of flora surrounding the drain to treat wastewater naturally and to minimize seepage/percolation from the drain water into soil and aquifer. The study results can be utilized to monitor and plan to minimize the soil deterioration by assessing potential polluted sites and sources efficiently.