ژئوشیمی، پهنه‌بندی و ریسک اکولوژیک فلزات سنگین در گرد و خاک های مدارس منطقه صنعتی غرب بندرعباس

In this study, the dust of primary schools located around the industrial centers of western Bandar Abbas was analyzed. Samples were analyzed by induced coupled plasma spectroscopy (ICP-MS). Environmental index of lead, zinc, cadmium, arsenic, chromium and nickel were evaluated. The results indicate that the study samples, except for chromium, have moderate to very strong contamination factor compared to other heavy elements, with the highest amount belonging to cadmium and lead. The highest value of ecological risk index belonged to the element cadmium (285) and the lowest value of this index showed the element chromium (3.68). The mean geo accumulation index of cadmium was the lowest and lead was the highest. Concentration of these elements was zoned using geochemical analysis datas. Comparison of how metal change and the similarity of their patterns in school dust samples with the average pattern of industrial centers and geological formations confirms the results

Introduction
Heavy metals are considered as environmental pollutions that enter the living environment of humans and other living organisms directly or indirectly. These elements are known as the primary pollutants given their toxicity and durability in the environment (Tuzen, 2003; Krishna and Govil, 2004). Poisoning due to these elements through inhaling or swallowing has recently become a severe public health problem (CDC, 1991). Hence, extensive research has been conducted on these elements' concentration in various parts of the environment (Kim et al., 2015 & Sun et al., 2010). Personal and environmental health promotion is among the scopes included in the Fundamental Education Transformation document (the Fundamental Education Transformation, 2011). Few yet extremely valuable studies have been conducted in this regard on a national scale. The importance of environmental indices, specifically in places occupied by students for long periods, highlights the significance of studying the concentration of toxic and heavy elements in the dust deposited in schools, especially those in industrial areas. Thus, the present study seeks to determine the concentration of heavy metals in the dust and evaluate the environmental indices and zone the concentration of such elements in schools located in the region using information data services.
Materials and methods
The studied site resides between the longitude of 55 degrees and 59’:50.88” and the latitude of 27 degrees and 4’:40.19”, occupying an area of 217km2 in West Bandar Abbas. Convenience sampling was conducted in elementary schools located in the industrial region, and the geological formations of the studied area were surveyed and sent to Zarazma Company's laboratory in Tehran for ICP-MS analysis. Laboratory data were analyzed using ArcGIS and Excel software. Given the dispersion of the convenient samples and the lack of coverage of the entire study are, the present study took advantage of geostatistical and interpolation methods using ArcGIS10.6.1 software. Regularized Spline interpolation was used to compile the element concentration zoning maps so that interpolation results would cover the entire studied area.
Results
The mean concentration of all metals exceeds the average crust concentration. This ratio was over 4, 2, 3, 5, 2, 2, and 5 times in lead, nickel, arsenic, cadmium, chromium, copper, and zinc, respectively. Comparing these patterns can help identify the trend of changes in pollution with these elements. As expected, the highest concentration of the studied elements was revealed to be in the range of industrial centers. The schools in the proximity of industrial centers had a lead pollution factor of over 6 and extremely high pollution levels. Most schools indicated high arsenic contamination, while most of them had moderate levels of nickel contamination. The schools in the proximity of industrial centers had extremely high nickel contamination which declined as moved towards the city center. Chrome element revealed to have strong contamination in the school nearest to the power plant. One-third of the elementary schools suffered from extremely high zinc pollution and others had moderate levels of pollution with this element. The schools near the power plant had high copper pollution and others had moderate levels of pollution with this element. The highest enrichment factor was associated with lead (Pb) and the lowest was associated with chromium (Cr). A range of 0.5 to 1.5 in this factor indicates that metal genesis is most probably due to natural factors, while higher values indicate that the elements are most likely to be due to human activities (Wei et al., 2015). The mean enrichment factor of chromium was 0.54 in the studied samples while other elements had values higher than 1.5. The enrichment factor ranged from low to significant for lead and zinc, low to moderate for arsenic, cadmium, nickel, and copper, and low for chromium. Overall, the schools positioned closets to industrial centers had the highest enrichment factors for the studied heavy elements, and the enrichment factor declined as the distance between the school and industrial centers increased. The mean geoaccumulation index (Igeo) of cadmium was revealed to be negative, indicating that the samples from some schools were non-contaminated and the others had moderate contamination. The elements of nickel, arsenic, chromium, and copper had moderate geoaccumulation indices of 1≤ Igeo <2, while zinc and lead had moderate to high geoaccumulation indices of 2≤ Igeo <3. The environmental risk index of dust collected from schools was revealed to be the highest in cadmium and the lowest in zinc. Rare earth elements normalized patterns were used to find whether there was a genetic relationship between dust from the schools and geological formations in the region. The similarities between these patterns confirmed genesis links with the Mishan formation. Still, the trend of change in the heavy element content of dust indicated complete similarity with the average of samples obtained from industrial centers.
Conclusion
Despite the heavy metal trend in Mishan formation samples and dust from the industrial center being similar to other samples, Mishan formation had low content and the industrial sample had the highest content of the studied elements. Thus, industrial activities are the most essential source of these elements in the dust in schools located in the studied area.
Key words:
Ecological Risk, Heavy Metals, Dust, Industrial Zone, West Bandar Abbas