Effects of thermal desorption on ecotoxicological characteristics of heavy petroleum-contaminated soil.

This study comprehensively evaluates the ecotoxicity of high-concentration heavy petroleum (HCHP)-contaminated soil before and after thermal desorption (TD) remediation at different temperatures and times. The results showed that the detoxification of contaminated soil was effectively achieved by extending the remediation duration at 400-600 °C. After treatment at 400 °C for 60 min, the toxicological indicators including bioluminescence EC50 (acute toxicity), seed germination ratio (Gr) and plant biomass of Brassica juncea (subacute toxicity), and diversity of the microbial community (chronic toxicity) reached a maximum. The value of the SOS-Induction Factor (SOSIF), characterizing genotoxicity was below 1.5, indicating that it was non-toxic. Pearson's correlation analysis illustrated that the water-soluble fraction (WSF), ALK1-3 and ARO1-3 of petroleum hydrocarbons were the primary sources of ecotoxicity. Notably, although the total ratio of petroleum removed from the soil reached 87.26 ± 4.38 %-98.69 ± 1.61 % under high-temperature thermal desorption (HTTD, 500-600 °C), the ecotoxicity was not lower than that at 400 °C. The pyrolysis products of petroleum macromolecules and extreme changes in soil properties were the leading causes of soil ecotoxicity following HTTD. The inconsistency between the removal of petroleum pollutants and ecological health risks reveals the significance of soil ecotoxicological assessments for identifying TD remediation endpoints and process optimization.

Highly efficient screening and optimal combination of functional isolates for bioremediation of hydrocarbon-polluted soil.

The key to enhancing the efficacy of bioremediation of hydrocarbon-contaminated soil is the precise and highly efficient screening of functional isolates. Low screening effectiveness, narrow screening range and an unstable structure of the constructed microflora during bioremediation are the shortcomings of the traditional shaking culture (TSC) method. To improve the secondary screening of isolates and microflora implemented for alkane degradation, this work evaluated the characterization relationship between bacterial function and enzyme activity and devised an enzyme activity assay (EAA) method. The results indicated a substantial positive correlation (r = 0.97) between 24 candidate isolates and their whole enzymes, proving that whole enzyme activity properly reflects the metabolic functions of microorganisms. The functional analysis of the isolates demonstrated that the EAA method in conjunction with microbial abundance and metabolite determination could broaden the screening range of functional isolates, including aliphatic acid-metabolizing isolates (isolates H4 and H7) and aliphatic acid-sensitive isolates (isolate H2) with n-hexadecane degradation ability. The EAA method also guided the construction of functional microflora and optimized the mode of application using combinations of alkane-degrading bacteria and aliphatic acid-degrading bacteria successively (e.g., F1+H7+H7). The combinations maintained a high abundance of functional isolates and stable α diversity and community composition throughout the experiment, which contributed to more advanced alkane degradation and mineralization ability (p < 0.01). Assuming a workload of 100 tests, the screening efficiency of the EAA method is more than 16 times that of the TSC method, and the greater the quantity of isolates, the higher the screening efficiency, enabling high-throughput screening. In conclusion, the EAA method has a broad-spectrum, accurate and highly efficient screening ability for functional isolates and microflora, which can provide intensive technical support for the development of bioremediation materials and the application of bioremediation technology.

Effects of mineral species and petroleum components on thermal desorption behavior of petroleum-contaminated soil.

Thermal desorption (TD) behavior of high-concentration petroleum-contaminated soil (PCS) is affected by soil composition, especially inorganic minerals. In this study, the TD behavior of petroleum-contaminated quartz (original mineral) and kaoline (clay mineral) were compared with those of pure petroleum (Petro-free); their "saturate, aromatic, resin, and asphaltenes" (SARA) fractions were investigated using thermogravimetry and differential thermogravimetry (TG-DTG). The modelling of the petroleum removal kinetics was also analyzed to provide insights into the mechanism. The results revealed that the limiting factor controlling the desorption of petroleum from quartz (Petro-Qtz) and kaoline (Petro-Kln) is the minerals, which increased the effective TD temperature by 200 °C and decreased TD efficiency by 2%. Compared to Petro-Qtz, Petro-Kln showed a lower desorption efficiency of 5% and the process was accomplished at a higher temperature of 100 °C. The investigation on SARA fractions indicated that polar fractions (i.e., aromatics, resins, and asphaltenes) were strongly captured by the minerals. The increment of the TD temperature of petroleum (resins-160 °C > aromatics-20 °C > saturates-5 °C) increased with the polarity of petroleum components. These results could be validated by thermogravimetry-gas chromatography/mass spectroscopy (TG-GC/MS) through the delayed desorption of naphthalene and acenaphthene. Furthermore, the increment of the TD temperature of SARA fractions on kaoline was higher than those on quartz. This makes sense because the kaoline decreased the diffusion of hydrocarbons due to its porosity features and higher specific surface area (kaoline 5.3300 m2 g-1, quartz 0.1153 m2 g-1). In addition, the analysis of the desorption kinetic models showed that the observed hysteresis was related to the diffusion barrier caused by chemisorption (n＜1). In consequence, the Petro-Kln showed a lower desorption efficiency, a slower desorption, and as a result, a higher energy consumption (0.476 kW h) for thermal remediation than Petro-Qtz (0.238 kW h).

[Study on the quantitative change of anthraquinonoids of Rhei in the preparation of dachengqi].

OBJECTIVE: To study the scientific evidence of the traditional preparation of Dachengqi: "Boiling Aurantii Immaturus and Magnoliae Officinalis first, and then adding Rhei to decoct together. Discarding the dregs, adding Natrii Sulfas into the decoction and drinking the upper solution when the Natrii Sulfas has dissolved completely". METHOD: The concentrations of free and combined anthraquinonoids(emodin, rhein, chrysophanol, physcion) in different decoctions were determined with HPLC method respectively. RESULT: When Natrii Sulfas, Aurantii Immaturus and Magnolias Officinalis are decocted with Rhei in different schemes, the concentrations of anthraquinonoids were changed regularly. CONCLUSION: The scientific evidence of traditional preparation method greatly increased the concentrations of the active components in Dachengqi.