The Mutual Effect of Cadmium and Magnetic Iron Nanoparticles in the Distribution of Chemical Forms of Cadmium in a Contaminated Soil

IntroductionThe contamination of agricultural soils with heavy metals is considered as a fundamental problem of industrial and non-industrial societies all over the world, which is increasing significantly with technological advances and is considered a serious threat to the environment, soil and human health. One of these heavy metals is cadmium, which has entered the environmental cycle due to various industrial activities such as metal smelting, battery manufacturing, paints, and plastic production. One of the suitable methods for cleaning the soil contaminated with heavy metals is to stabilize the elements by adding a modifier to the soil, which leads to a decrease in their mobility and bioavailability during the processes of absorption, oxidation and reduction, complexation or deposition. The use of iron nanoparticles is a new generation of environmental cleaning technology that can be an economic solution to some problems caused by pollutants, unlike traditional methods. Considering the importance of soil as a plant food holder and its special role in the food chain and the harmful effects of pollutants such as heavy metals in the soil, this research seeks to explore the potential of magnetic iron nanoparticles in remediating cadmium-contaminated soil. The study aims to investigate the effectiveness of these nanoparticles in reducing cadmium levels and their impact on the distribution of cadmium in different soil components. Materials and MethodsThe experiments were carried out in the chemical and biological research laboratory of the Department of Soil Science and Engineering of Maragheh University. To conduct the experiment, a soil sample from Ajabshir city with a geographic location of 54 degrees 46 minutes 51.7 seconds east longitude and 37 degrees 24 minutes 34 seconds north latitude located in East Azarbaijan province with an altitude of 1451 meters above sea level, with this The target of extractable cadmium less than 1.16 mg/kg of dry and textured soil (loam) was selected. This experiment is factorial based on random design with two factors of heavy metal cadmium from cadmium sulfate source including cadmium concentrations at three levels of zero, 6 and 12 mg/kg of soil and the factor of magnetic iron nanoparticles at three levels of zero, 1 and 2% in The time was four weeks after the addition of cadmium treatments and it was implemented in three repetitions. After measuring some physical and chemical properties of soil, cadmium concentrations in different species and ionic fractions were measured according to the method provided by Tisser. Finally, the obtained data were analyzed using SPSS and MSTATC software and the means were compared with Duncan's multiple range test at the level of five and one percent probability and the results were interpreted. Discussion and ConclusionBy increasing the amount of cadmium treatment levels from 6 to 12 mg/kg, the amount of cadmium absorption in the exchange phase decreased. Therefore, the increase in the amount of cadmium levels in different levels of iron nanoparticles reduced the absorption of cadmium in the exchange phase, which in turn reduced the ability of the plant to absorb cadmium and removed cadmium from the plant. By increasing the amount of cadmium in the soil by 1%, nanoparticles increased the amount of cadmium extracted from the carbonate phase. Increasing the amount of cadmium added to the soil at different levels of nanoparticles, the amount of cadmium absorption extracted from the carbonate phase increased, and at the level of 12 mg cadmium/kg, the amount of cadmium extracted from the carbonate phase increased compared to the level of 6 mg cadmium/kg. In cadmium treatments at the level of 12 mg/kg, the amount of cadmium extracted from the phase of iron and manganese oxides were increased compared to cadmium at the level of 6 mg/kg, and in the same treatments at the level of 12 mg/kg, the amount of cadmium extracted was increased with the increase in the amount of nanoparticles. The results showed an increase in the phase of iron and manganese oxides, which may reduce the amount of cadmium available to the plant. In cadmium treatments at the level of 6 mg/kg at the level of 1% of nanoparticles, compared to the other two treatments, an increase in the amount of cadmium extracted from the oxide phase was observed. In the treatment of cadmium at the level of 12 mg/kg, the amount of cadmium extracted from the phase of organic matter increased compared to the treatment of cadmium at the level of 6 mg/kg. Indeed, the research findings reveal an interesting trend in the impact of increasing iron nanoparticles at both cadmium levels of 6 and 12 mg/kg. Specifically, the changes in the amount of cadmium extracted from the organic phase of the soil follow a consistent pattern. Initially, as the iron nanoparticles were introduced, the cadmium extraction from the organic materials decreased. However, at higher levels of nanoparticles, the cadmium extraction started to increase again.This trend suggests that the presence of a higher concentration of nanoparticles may play a role in stabilizing cadmium in the organic matter of the soil. As a result, it may reduce the accessibility of cadmium to plants. In the treatment of cadmium at the level of 12 mg/kg, the amount of cadmium extracted from the residual phase increased compared to cadmium at the level of 6 mg/kg. In the examination of cadmium extracted from the residual phase, it was found that, unlike other phases, the difference between treatments at zero cadmium level and other treatment levels of cadmium in the remaining phase was less compared to other phases, so that the amount of cadmium absorbed in the remaining phase 6 and 12 mg of cadmium per kilograms of soil have the lowest values among different absorption phases. Also, another noteworthy point about this examination was the trend of changes in extracted cadmium according to the levels of nanoparticles in all three levels of cadmium, so that with the increase of nanoparticles from zero to 1% in all levels of cadmium, there was a decreasing trend and with the increase of non-particles to two percent, an increasing trend was observed. ConclusionThe results showed that in general, with increasing the level of iron nanoparticles, treatment of 12 kg of cadmium, the amounts of residual cadmium, carbonate, organic and oxide phases increased. Increasing the level of cadmium in different levels of iron nanoparticles reduced the absorption of cadmium in the exchange phase, which reduces the ability of the plant to absorb cadmium and removes cadmium from the plant, so that in the treatment with cadmium at the level of 12 mg/kg, the amount of cadmium extracted from the exchange phase reduced. Also, in the cadmium treatment at the level of 6 mg/kg with increasing the amount of nanoparticles, the amount of cadmium extracted from the exchange phase first increased and then a slight decrease in the amount of absorbed cadmium was observed, while at the level of 12 mg of cadmium, the amount of cadmium increased, absorption reduced, and thus removing cadmium from the plant.