Polycyclic aromatic hydrocarbons are toxic pollutants which persist in the environment. Extraction of polycyclic aromatic hydrocarbons requires large volumes of toxic organic solvents, but the use of non-hazardous solvents provides a potentially cleaner approach to quantifying polycyclic aromatic hydrocarbons in environmental matrices. Here we investigated the efficiency of eucalyptus oil to extract polycyclic aromatic hydrocarbons from spiked soil and sediment. Eucalyptus oil extraction conditions including temperature, time, and volume of oil were optimized employing a Box–Behnken experimental design, and the desorption kinetics of phenanthrene, pyrene, chrysene, and benzo[a]pyrene were evaluated using an empirical first order kinetic model. Results show that extraction efficiency from soil, of 112% for phenanthrene, 108% for pyrene, 102% for chrysene and 98% for benzo[a]pyrene, is higher than that from sediment, of 90, 111, 84 and 82%, respectively. This may be due to soil possessing 12 times more organic carbon. Recoveries higher than 77% were obtained over the concentration range 0.5–10 mg/kg for the tested polycyclic aromatic hydrocarbons, with limits of detection lower than 63 µg/kg and limits of quantitation lower than 125 µg/kg. These findings suggest that eucalyptus oil has potential as a safer solvent to extract hydrophobic contaminants.
The study was conducted to evaluate the effects of parboiling treatment on the minerals and heavy metals of six Sri Lankan traditional rice varieties; Kalu heenati, Pokkali, Gurusinghe wee, Kahawanu, Sudu murunga and Unakola samba. Metals were determined by using ICP-AES and AAS. Parboiling can be considered as a suitable rice processing method for Pokkali and Kahawanu and not for Kalu heenati and Unakola samba in order to furnish the recommended daily intake of the micronutrients. Un-parboiled Kalu heenati and both un-parboiled and parboiled Kahawanu can be considered as the most suitable rice varieties for daily consumption in order to maintain the recommended daily intake of iron. It was identified that Pokkali rice contained the highest iron content of 29.5 mg/100 g. This amount has further increased by 66.7% after parboiling. Therefore both parboiled and unparboiled Pokkali can be considered as the best dietary supplement among these rice varieties for iron deficiency and for pregnant mothers. Selected heavy metals including As, Cd, Pb and Cu were not detected in the selected Sri Lankan traditional rice varieties.
The potential for biosurfactant-mediated desorption of polyaromatic hydrocarbons (PAHs) was evaluated using PAH-spiked soil and sediment. PAH desorption behaviors and toxicity of novel saponin biosurfactant extracted from Eucalyptus camaldulensis leaves and sophoro-lipid biosurfactant were investigated. Their PAH desorption efficiencies were compared with rhamnolipid biosurfactant and the industrial-chemical surfactant, Tween 20. Based on the emulsification indices, the salt tolerance of surfactants up to 30 g/L NaCl followed the order of saponin > Tween 20 > sophorolipid > rhamnolipid, while the thermal stability over the range of 15 to 50 °C was in the order of sophorolipid > rhamnolipid > saponin > Tween 20. The saponin biosurfactant emulsion demonstrated the highest stability under a wide range of acidic to basic pHs. PAH extraction percentages of saponin and sophorolipid under the optimized surfactant concentration, volume, and incubation time were 30–50% and 30–70%, respectively. PAH desorption capacities of saponin and sophorolipid were comparable to that of rhamnolipid and Tween 20 for all matrices. Sophorolipid more efficiently desorbed low molecular weight PAHs in soil and sediment compared to the other three surfactants. Microbial respiration was used to determine biosurfactant toxicity to the soil/sediment microbiome and indicated no inhibition of respiration during 60 days of incubation, suggesting that sophorolipid- and saponin-mediated remediation may be sustainable approaches to remove PAHs from contaminated soils and sediments.
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