Effects of heavy metal contaminants of traffic origin on some soil enzyme activities in Gaziantep (Türkiye)

This study aims to investigate the impact of potentially toxic elements (PTEs) originating from traffic on the microbial and enzymatic activities of soils. For this purpose, 80 soil samples were collected from mixed pistachio (Pistacia vera L.) and olive (Olea europaea L.) orchards along roadsides and selected general properties, nutritional elements, PTE contents and soil microbial and enzymatic activities of the samples were analyzed. The sources of PTEs were determined using multiple statistical methods, and pollution levels were evaluated according to ecological and environmental indices. It was found that the abundance of PTEs was in the order of Fe>Mn>Ni>Cr>Zn>Pb>Cu>Co>Cd. It has been determined that 53.13% of the soils exceeded legal limits for Ni and 15.63% for Cr. Based on the results of multiple statistical analyses, it was identified that Co, Cr, Cu, Fe, Mn, Ni, and Pb are lithogenic, whereas Cd and Zn are anthropogenic origin. The soil fertility in terms of agricultural productivity was found to have decreased due to moderate levels of Ni and Pb pollution and light levels of Cd and Cr pollution. It has been determined that Cd, one of the PTEs determined to be enriched because of inorganic and organic fertilization, has a negative effect on ALP, while Zn has a positive effect. Also, lithogenic PTEs were found to have a negative effect on ASP and URA, but a positive effect on CAT, ALP, BSR and C/N. The study concluded that vehicle traffic emissions did not significantly impact microbial and enzymatic activities.