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Performance assessment of rhamnolipid MR01biosurfactant and Triton X-100 chemical surfactant in removal of phenanthrene from soil
Masoumeh Golshan, Simin Nasseri, Mahdi Farzadkia, Ali Esrafili, Roshanak Rezaei Kalantary, Leila Karimi Takanlu,
Volume 7, Issue 2 (10-2014)
Abstract

Background and Objectives: The use of surfactants enhance the bioavailability of nonbiodegradable contaminants such as PAHs. Biosurfactants are more environmental friendly. In this study the ability of removing phenenthrene from soil by biosurfactant was assessed and compared with that of chemical surfactant. Materials and Methods: A soil sample free of any organic or microbial contamination was artificially spiked with phenanthrene at two concentrations. Then, mineral salt medium at constant concentration of chemical surfactant TritonX-100 and rhamnolipid MR01biosurfactant was added to it in order to have the proportion of 10% w:v (soil:water). A microbial consortium with a potential of phenanthrene biodegradation was inoculated to the soil slurry in two densities (OD=1 and 2) and then it was aerated on a shaker. After eight weeks, the residual concentration of phenanthrene in the soil was extracted by ultrasonic and was analyzed using HPLC. MPN test was used for measuring microbial population. This study was conducted based on the two level full factorial design of experiment. Results: It was found that chemical surfactant exhibited higher PHE removal efficiency than the biosurfactant. Using 120 mg/L of TritonX-100 and rhamnolipid, the PHE removal for the soil contaminated with 50 mg PHE/kg dry soil was 98.5 and 88.7% respectively, while the removal efficieny was decreased to 87 and 76% respectively for the soil contaminated with 300 mg PHE/kg. In the absence of surfactant, the removal efficiency at concentrations of 50 and 300 mg PHE/kg dry soil was achieved 60.76 and 51% respectively. The phenanthrene removal efficiency in OD=2 was more higher than OD=1. In the presence of rhamnolipid, the maximum microbial populations was observed in the second week, while it decreased in the presence of TritonX-100. Conclusion: Use of biosurfactants can be considered as a suitable option in low level pollutant sites. Chemical surfactants as ex-situ has achieved more satisfactory results in high level contaminant sites.


Chemical speciation and bioavailability of potentially toxic elements in agricultural soils (case study: south of Hamedan province)
Iraj Asadi, Mehrdad Cheraghi, Bahareh Lorestani, Hajar Merrikhpour, Soheil Sobhanardakani,
Volume 17, Issue 4 (3-2025)
Abstract
Background and Objective: Evaluating the chemical speciation and bioavailability of heavy metals, along with identifying the effective parameters influencing their bioavailability, plays a key role in soil management and the improvement of agricultural lands. Therefore, this research was conducted to determine the origin, chemical speciation, and bioavailability of potentially toxic elements (PTEs) in the agricultural soils of the southern cities of Hamedan province.
Materials and Methods: In this study, 90 surface soil samples were randomly collected from a depth of 0–20 cm in agricultural lands. After preparing the samples in the laboratory, the elemental content was measured using an atomic absorption device. Texture characteristics, acidity (pH), salinity (EC), calcium carbonate content, organic matter, and exchangeable cations were determined using methods proposed by the Environmental Protection Organization. The relationships between the bioavailability of heavy metals and these characteristics were investigated using Spearman's correlation test.
Results: The average concentrations of manganese, cadmium, iron, cobalt, chromium, copper, nickel, antimony, and arsenic in the three studied cities were 267.63, 0.19, 4.20, 20.65, 90.49, 35.86, 70.84, 3.78, and 17.82 mg/kg, respectively. Sequential extraction results showed that manganese, copper, and nickel had the highest bioavailability, with concentrations of 6.76, 2.91, and 3.77 mg/kg, respectively. More than 70% of the bonds between heavy metals and soil were in resistant and residual fractions, indicating that heavy metals in the soil have a natural background.
Conclusion: The bioavailability of heavy metals in the soil environment is low, suggesting minimal potential for these metals to enter water, soil, and crops, and thus does not pose significant concern.
 

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