ارزیابی اثرات آلودگی فلزات سنگین صنایع مهم شهرستان شازند بر محیط‌زیست اطراف

Abstract
Introduction
With the increase in population and the expansion of cities and their transformation into the heterogeneous population and social centers, various types of environmental pollution have been created, causing damage to the city and the excessive growth of cities. Therefore, with the increase in human activities along with the rapid expansion of urbanization in the past few decades, scientific monitoring of important industries is highly needed. When there are several pollutants in the air together, they stimulate each other's effect and have a more aggravating effect and finally multiply the damage caused to living beings, especially plants. In general, one pollutant may create the conditions for the impact of another pollutant, and in this situation, the organisms or the plant as a defenseless organism will be stressed, but which pollutant has the most significant impact on the organisms cannot be easily determined. Pollution in each of the water and soil sources is one of the serious problems that is inseparable from daily and modern civilization. According to international standards, heavy metals are known as the most dangerous group of contaminants created by humans due to their high toxicity and lethality, as well as their high persistence in the environment. Based on this, industries have a high pollution load, especially the release of suspended particles and heavy metals into the surrounding environment, which should be considered with special care in terms of their establishment and exploitation in order to avoid any risks and adverse effects on humans and other organisms. Therefore, the aim of this study was to investigate the environmental effects of the important industries of Shazand city on the surrounding environment.
Methodology
Shazand city is very important due to the presence of major industries such as gasoline refinery, petrochemical, and thermal power plant, being located on the west and south transit routes, and the national north-south railway line of the country. Therefore, this research was conducted with the aim of creating environmental concerns in the field of pollution caused by metals (including Cu, Zn, Mg, Fe, Cd, Pb, Cr, and Co) in the soil and plants within a five-kilometer radius of important industries in Shazand city. For this purpose, soil samples from a depth of 0-30 cm and plant samples from green areas (pine trees), fruit orchards (leaves and fruits of walnuts and almonds), wheat fields (including samples of roots, stems, leaves, and seeds), pastures (mountain rye (Secale montanum. L) and Euphorbia (Euphorbia helioscopia. L)) were prepared. From each of the tested ranges, 10 samples were selected and tested. A sampling of plants, soil, and water was done based on a random systematic method and the study area was divided into 5×5 km square grids. By examining the area, the areas where the intensity of land use was high or low, grid spacing of 2.5×2.5 square kilometers was selected for sampling. Extraction to determine the concentration of heavy metals in the soil was also done by HCl and HNO2 digestion methods. The concentration of heavy elements was measured using an atomic absorption device and a graphite furnace.
Results
The test results showed that the concentration of Cd, Pb, Co, and Cr in all the studied soils was higher than the permissible limit. Also, the concentration of Fe, Cu and Cr, Cd, and Co in all plant samples of green spaces, gardens, and pastures was beyond the allowed concentration. Although the concentration of Cr and Co in wheat grain exceeded the permissible limit, they were not in the critical range. From the analysis of the concentration of elements in the soil of each vegetation cover, it was found that the highest values of the transfer coefficient were observed in the soil of wheat fields, pastures, orchards, and green spaces, respectively. The concentration of elements in the soil of each vegetation cover was determined, and the highest ecological risk index was obtained in the soil of pastures, orchards, wheat fields, and green spaces, respectively. However, in all the sampled soils, the index value was calculated to be less than 150, which indicates the low ecological risk of the measured elements in the sampled soil. Based on the results, the transfer factor of manganese and cadmium was measured more than once, and these results indicate the bioaccumulation of these metals from soil to plants, and for the rest of the measured metals, this amount was calculated to be less than one. Based on this, it was reported that the transfer factor in gardens and pasture plants was higher than in wheat in the investigated area. The reason for this was the permanent presence of these plants in the region. Another noteworthy point was the accumulation of these elements in the seeds or fruits of plants, which was observed more than in other plant organs.
Conclusion
Due to the increasing importance of food, in recent years, the attention of the public and regulatory organizations in the food sector, especially the World Trade Organization, has been seriously focused on food safety and quality assurance. Based on the results obtained:
In pine leaves, the concentration of Cu, Co, Cd, Mg, and Cr elements exceeded the permissible limit, and only the concentration of Cu, Mg, and Cr elements was in the critical concentration range.
- In walnut leaves, the concentration of Cu and Cr elements exceeded the permissible limit and was in the critical concentration range, but the concentration of Cd and Co exceeded the normal limit. In almond leaves, the concentration of Cr and Co was higher than normal.
- In almond fruit, the concentration of Cr, Co and Cd elements was higher than normal, but it was not in the critical concentration range.
- In the investigation of the concentration of elements in wheat grain, it was found that the concentration of Cr and Co elements exceeded the permissible limit, but it was not in the critical range.
- The concentration of Cu, Co, Cd, and Cr elements in mountain rye and Euphorbia plants exceeded the permissible limits and were in the critical range. However, in mountain rye, the concentration of Cr element was higher than its normal level in plants and was in the critical range.
- The values of transfer factor were observed in the soil of wheat fields and pastures respectively higher than garden soil and green space. Also, the risk assessment index was obtained in the soil of pastures and orchards higher than wheat lands and green spaces, respectively.