Evaluation of the Pollution Level of Ecosystems in the Industrial Area of West Bandar Abbas by a Resilience Approach against Heavy Metals

Heavy metals are elements that have an atomic mass of more than 55.8 g/mol; these elements have little biodegradability, but their ability to bioaccumulate is very high, and when their concentration exceeds the threshold, they threaten the health of the environment with the risk of toxicity and pollution. West Bandar Abbas industrial area consists of several industrial complexes located less than 5 km from Shahid Rajaei wharf, and the high-traffic transport axis passes through these industries. The concentration of these industries and traffic of the transport road have caused severe pollution of the environment and ecosystems in this area, but the level of pollution in various aspects remains unknown. Although studies have been conducted on air pollution or environmental assessment, the assessment of soil pollution, heavy metals and their effects on the plants of the region, which are biological markers, have not been investigated since it is possible to reveal the level of environmental pollution by evaluating the level of pollution in plants. Therefore, the main approach of the current research is to evaluate the level of environmental pollution in the industrial area of west of Bandar Abbas by examining heavy metals in the soil and leaves of Acacia in the area, and also investigating the reaction of Acacia, which are native to this area, against pollution.

The experiment was implemented in the RCBD plan. From each location, 10 soil samples (replicates) were taken at a depth of 0 to 10 cm and placed in an envelope and labeled. Soil samples were transferred to Bandar Abbas soil laboratory to measure the concentration of heavy metals including lead (Pb), cadmium (Cd), zinc (Zn), copper (Cu), chromium (Cr) and nickel (Ni), which were evaluated by Igeo, CF, PLI, BCF, MAI and RI indexes. Biochemical reactions of Acacia, including its photosynthetic pigments, proline, ascorbic acid and relative leaf water against pollution were measured. Finally, APTI was obtained for Acacia.

In this study, the level of heavy metal pollution caused by industries in the target area was evaluated by inspecting some pollution indicators. According to the Igeo index, the areas close to the industries and the area of industrial factories and Bandar Abbas oil refinery are the most polluted areas and contain much higher heavy metals than the standard heavy metals in the soil. Evaluation of Igeo for zinc and copper metals is low and it is in the class of non-pollution to moderate pollution, but for cadmium, lead, chromium and nickel in the measured points, it is mostly moderate to very severe pollution, and in the places close to the industries, mainly for all metals, the level of pollution is moderate to severe. Away from the industrial factories, the concentration of pollutants and the risk of pollution decrease. The CF is also high for cadmium, lead, chromium and nickel, and the pollution level is significant, moderate and severe. The PLI in this study showed that the points near Shahid Rajaei industries and wharf have high pollution loads, but with the distance from the industries, the numerical value of this index decreases and the pollution load also decreases. In this study, the biochemical reaction of Acacia against heavy metal contamination was also measured. Pollution has an effect on the content of photosynthetic pigments of Acacia in the industrial area of west of Bandar Abbas to the extent that the amount of chlorophyll a, b and total chlorophyll in the polluted areas and near the industries compared to the clean and control areas and the areas far from the industries showed a significant decrease at 99% level. The results of this research also indicated that pollution can reduce photosynthesis in plants by reducing pigments. In addition, it was found that in Acacia under the stress of heavy metal pollution, the concentration of ascorbic acid and proline differed by 99% and increased compared to the control condition. This increase helps the Acacia to continue its physiology and mechanism and survive under the stress of pollution. Furthermore, APTI was calculated in the Acacia in the studied locations and the results showed that in the highly polluted sites in Shahid Rajaei Wharf, Bandar Abbas Oil Refinery and Industrial Area, the concentration of heavy metals in the soil as well as the air pollution is very high. APTI is reduced and reaches 7; however, in the eastern slope of Salt Dome, Shahid Bahonar Wharf and Point Shahid, the APTI of Acacia plant is more than 9 which is evaluated as good and suitable.

By absorbing heavy metals in the soil and accumulating elements in the plant organ, which is a medium accumulator, Acacia plays a crucial role in removing the pollutants from the ecosystems of the region and can be useful in phytoremediation. In this study, the biochemical response of Acacia to heavy metal pollution was investigated and the results showed that although the concentration of chlorophyll in infected Acacia decreased compared to the control condition, the amount of ascorbic acid and proline in the plant increased which strengthens the plant's resistance against pollution; in fact, it can be said that Acacia trees have the ability to react optimally against heavy metal pollution. Nevertheless, in Bandar Abbas, unfortunately, the invasive species of American Acacia has been planted among native Acacia, and due to the deep roots of this invasive species, the health of the native species has been endangered. On the whole, the results of this research showed that Acacia, which is a native species, has the ability to absorb heavy metals and remove them from the environment. Therefore, it is suggested that by spreading Iranian Acacia and removing the invasive American species, we can revive the ecosystem of the industrial area, prevent environmental pollution and take positive steps towards environmental protection.