Soil science
A. Barikloo; P. Alamdari; A. Golchin
Abstract
IntroductionHeavy metals such as lead, aluminum, mercury, copper, cadmium, nickel, and arsenic are now commonly found worldwide. Among these, cadmium and lead are the most hazardous, posing significant risks to both the environment and human health. Cleaning soils contaminated with organic and inorganic ...
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IntroductionHeavy metals such as lead, aluminum, mercury, copper, cadmium, nickel, and arsenic are now commonly found worldwide. Among these, cadmium and lead are the most hazardous, posing significant risks to both the environment and human health. Cleaning soils contaminated with organic and inorganic contaminants is one of the most significant and fundamental challenges facing society today. One effective method for soil purification is to extract or immobilize the contaminant within the soil. Materials and MethodsIt is unclear how water-soluble polymers contribute to the immobilization of heavy metals. The purpose of this study is to examine how various polymers affect the immobilization of lead, zinc, and cadmium in the soil near a lead and zinc mine in the province of Zanjan. A factorial experiment with three replications was conducted using a randomized complete block design. The experimental treatments included one type of soil and three different kinds of acrylic polymers (cationic, nonionic, and anionic) applied at four different levels (0, 0.05, 0.1, and 0.2). The absorbable amounts of lead, zinc, and cadmium were tested at various intervals after the polymers were applied to the soil samples. After that, SAS statistical software was used to examine the data. To do this, the Duncan multiple range test was used to compare the means. The necessary tables and graphs were then created using Excel. Results and DiscussionThe findings demonstrated that, at 1% probability level, the kind of polymer had a considerable impact on the amount of lead, zinc, and cadmium that may be absorbed in the soil. The average concentration of soil-absorbable lead for the different types of polymers employed was 239.8, 260.15, and 267.65 mg/kg; anionic polymer had the lowest concentration. Stated differently, anionic polymer decreases the capacity to absorb lead and stabilizes more lead in the soil than the other two forms of polymer. Anionic polymers most likely have a stronger impact on soil granulation. Additionally, at 1% probability level, the impact of acrylic polymer intake on the amount of lead, zinc, and cadmium absorbable in the soil was considerable. With an increase in the amount of polymer utilized in the soil, the greatest absorbable lead concentration (301.58 mg/kg) in the control treatment dropped to the lowest absorbable lead concentration (0.2). It was possible to determine the polymer percentage and the lead concentration, which came out to be 205.9 mg/kg of soil. Zinc concentration dropped as acrylic polymer consumption increased; in the control treatment, absorbable zinc concentrations ranged from 0.2 to 83.5 mg/kg of soil, with 0.2 being the highest concentration. At 1% probability level, the impact of the polymer's contact time with the soil on the amount of lead, zinc, and cadmium that the soil may absorb was significant. As a result, the tested soil had 414.52 mg of these elements at the initial stage of polymer treatment. The quantity of absorbable lead in the soil became 66% immobilized after a month, and after 720 hours, the amount of absorbable lead dropped to 141.83 mg/kg. As the polymer's contact time with the soil increased, so did the concentration of absorbable zinc in the soil. At 1% probability level, there was a strong correlation between the kind and amount of acrylic polymers and the amount of lead, zinc, and cadmium that may be absorbed in the soil. The ingestion of 0.2% anionic polymer resulted in the largest amount of lead immobilization, lowering the soil's absorbable lead concentration from 300 to 192 mg/kg of soil. A higher amount of anionic polymer immobilized the lead, and both cationic and non-ionic polymers were positioned after it. Additionally, anionic polymer was more prevalent than cationic polymer. It caused the non-ionic polymer's absorbable zinc to become immobile. Following 720 hours of polymer treatment, the soil's absorbable zinc element was immobilized to a greater extent by the anionic polymer (20%) than by the cationic and non-ionic polymers (26%), respectively. In comparison to the original concentration, the largest amount of immobilization by anionic polymer after one month was 78%, and the lowest amount of immobilization by nonionic polymer was 61%. Anionic polymer was 27% more effective than non-ionic polymer, 18% more effective than cationic polymer, and stabilized more cadmium. Conclusion The results of this study showed that with increasing the duration of contact of polymers used with the soil, the amount of mobility of heavy metals in the soil decreased and also with increasing the amount of polymer consumption, the rate of metal stabilization in the soil increased. Anionic polymers immobilize more lead, zinc and cadmium in soil. To reduce the mobility of lead, zinc and cadmium and improve the stability and increase aggregation in soil, the use of acrylic polymer in contaminated soil is recommended.
