نوع مقاله : مقاله کامل علمی پژوهشی
نویسندگان
1 هیات علمی
2 گروه علوم خاک- دانشکده کشاورزی و منابع طبیعی- دانشگاه یاسوج
3 گروه علوم و مهندسی طبیعت- دانشکده کشاورزی و منابع طبیعی- دانشگاه یاسوج
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Background and objectives: The classification of Cd as the Group I carcinogenic and its position among the most toxic metals highlights the need of understanding and mitigate its effects in agricultural and natural ecosystems. Cadmium in soil exist as soluble, exchangeable, carbonate bonded, and associated with FeMn oxides forms, which play an important role in the mobility, bioavailability, and potential toxicity of cadmium. Knowledge about the distribution and behavior of cadmium fractions is essential for efficient environmental management and remediation strategies aimed at reducing Cd bioavailability in soil and protecting food production systems. This study was conducted to investigate the changes in cadmium fractions due to its addition to several calcareous soil samples over time.
Materials and Methods: The experiment was conducted as a 2-factor factorial design with 13 soil samples and two levels of cadmium (12.5 and 25 mg/kg soil) with two replications in a completely randomized design. The total number of samples was 52. Soils were contaminated with 12.5 and 25 mg Cd Kg in duplicate and stored at laboratory temperature and 20% w/w moisture content. At 40 and 90 days after incubation, a wet sample about 2 g was taken and its dry weight was calculated using moisture content of the samples. Sequential extraction with F1) distilled water (solution form), F2) neutral 1M ammonium acetate (NH4OAc) (exchangeable form), F3) 1M NH4OAc at pH 5 (carbonate form); F4) 0.04 M hydroxylamine hydrochloride in 25% v/v acetic acid at pH 3 (associated with iron and manganese oxides); F5) 30% hydrogen peroxide pH 2 with 5 ml 0.3M NH4OAc in 20% v/v nitric acid (form bonded to organic matter); and F6) 7 M nitric acid (residual form) were performed and the cadmium concentration of the extracts was measured by atomic absorption spectrometry.
Results: Cadmium added to soils was recovered mainly in Exch-Cd, Car-Cd and FeMn oxides forms. The sum of Exch-, Car- and FeMn oxides forms constituted more than 90% of the cadmium added to the soils. On the day 40 of incubation at 12.5 and 25 mg cadmium levels, the average exchangeable cadmium was 2.41 and 5.68 mg kg-1, respectively, equivalent to 19 and 23 percent of the added Cd. A large portion of applied Cd was recovered in carbonate form at the both times of incubation. The average cadmium carbonate at the levels of 12.5 and 25 mg/kg on day 40 was 7.15 and 14.65 mg/kg, respectively. At both levels of Cd, approximately 58% of Cd was recovered as Car-Cd on 40d of incubation, which decreased to approximately 40% by 90d. Average content of FeMn oxid bonded Cd on the day 40 was 0.98 and 3.3 mg kg-1 at 12.5 and 25 cadmium levels, respectively, constituted 8 and 13% of the added Cd. On day 90, FeMn oxides-Cd increased to an average of 2.98 and 6.68 mg/kg, which was 24 and 27% of the applied Cd, respectively.
Conclusion: In the present study, the mobility of cadmium was high and the soil potential to stabilize Cd was low despite the calcareous nature of the studied soils. It seems that CEC and OM content are the soil properties that may influence Cd fractions transformation, and the increase of these two properties could reduce Cd mobility in soil.
کلیدواژهها [English]
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