Heavy metal contamination of topsoil in Denizli Organized Industrial Zone, Western Anatolia, Turkey

Abstract

This paper deals with determination of the environmental pollution in Denizli Organized Industrial Zone and its surroundings. Denizli is one of the biggest industrial cities of Turkey hosting several factories with immense production, regularly shipped by a vast haulage system. The study area is traversed by one of the most crowded highways in the country, ensuring the transportation between Western and Central Anatolia. It is also traversed by a railroad connecting Denizli city to Izmir city located on the Aegean Sea coast. Therefore, covering an area of about 30 km2, 154 samples were collected to be subject of the magnetic susceptibility measurements end up at highlighting contaminated zones in the study area. The spatial distribution maps plotted for both magnetic susceptibility measurements acquired at high (χHF) and low (χLF) frequencies showed coherent anomalies following the direction of the roads (east-west). According to the magnetic susceptibility measurements, 40 initial samples were chosen to be chemically analysed by X-ray fluorescence (XRF) analysis. The soil nature was determined by examining 10 supplementary samples collected from the study area. Concentrations of copper (Cu), lead (Pb), nickel (Ni), chromium (Cr), zinc (Zn), and iron (Fe) and magnetic parameters were statistically analysed for the best understanding of the correlation of the heavy metal pollution and magnetic susceptibility values. The environmental status of the study area was evaluated by the aid of elaboration and interpretation of the contamination factor (CF), geoaccumulation index (Igeo), enrichment factor (EF), and the pollution load index (PLI) which allowed the comparison between the different polluted parts of the study area. The results obtained as maximum values from the calculation of the contamination factor were found as follows: Cr (31.12), Ni (12.88), Fe (11.42), Cu (11.20), Zn (4.71), and Pb (2.87). The maximum values obtained for the implemented geoaccumulation index were found for each element as follow: Cr (4.37), Ni (3.1), Fe (2.93), Cu (2.9), Zn (1.65), and Pb (0.9), while the enrichment factor’s results were found as follow: Fe (2.93), Cr (4.37), Ni (3.10), Zn (1.65), Cu (2.90), and Pb (0.93). Results showed that the Tomlinson pollution load index (PLI) calculated for the six elements is reflecting a heavy pollution of the study area by reaching the value of 6.41 as a mean of the total analysis results and 11 as a maximum value. The magnetic susceptibility and heavy metals distribution showed similar anomaly locations especially out of the area of Denizli organized industrial zone which seems to be less contaminated giving a sign of the liberation of industrial wastes into the surrounding areas. The farming lands were also found to be acting in the enrichment of the heavy metal content in the study area soils. The main anomalies introduce the contamination of the lower zones of the study area which is the result of the transportation of anthropogenic pollutants by wind and stream. Considering the study results, it is recommended to regularly evaluate the environmental status of the study area in order to prevent irremediable diseases.