Pyrolytic Remediation and Ecotoxicity Assessment of Fuel-Oil-Contaminated Soil.

Oil-contaminated soil is a major societal problem for humans and the environment. In this study, the pyrolysis method was applied to oil-contaminated soil used as a landfill and gas station site in Korea. The removal efficiency of the main components of oil-contaminated soils, such as total petroleum hydrocarbons (TPH), polyaromatic hydrocarbons (PAHs), unresolved complex mixture (UCM), and alkylated PAHs (Alk-PAHs) were measured, and the effect of temperature, treatment time, and moisture content on pyrolysis efficiency was studied. In order to evaluate the risk of soil from which pollutants were removed through pyrolysis, integrated ecotoxicity was evaluated using Daphnia magna and Allivibrio fischeri. The chemical and biological measurements in this study include contaminants of emerging concerns (CECs). Results showed that the pyrolysis was more efficient with higher treatment temperatures, moisture content, and treatment times. In addition, toxicity was reduced by 99% after pyrolysis, and the degree of toxicity was evaluated more sensitively in Allivibrio fischeri than in Daphnia magna. This study shows that weathered oil-contaminated soil can be effectively treated in a relatively short time through pyrolysis, as well as provides information on efficient conditions and the assessment of ecotoxicity.

Hemoglobin peroxidase reaction of hemoglobin efficiently catalyzes oxidation of benzo[a]pyrene.

Its high molecular weight endows benzo[a]pyrene (BaP) with strong adsorption to soil, causing serious soil contamination. Our previous study has reported that hemoglobin (Hb) is able to oxidize organic pollutants in the presence of H2O2. This present study showed that Hb catalytic mechanism for BaP oxidation was similar to that of lignin peroxidase. 2-Methyl-3-vinylmaleimide was confirmed as a major degradation intermediate of BaP by Hb catalysis. In addition, BaP was shown to be degraded by heme (Hm)-catalyzed reaction, suggesting that Hm of Hb is the essential catalytic center. Rate constants (k) for BaP oxidation by Hm-catalyzed reaction were 0.4954 h-1. The major degradation intermediate by Hm-catalyzed reaction is 3,3',5,5'-tetramethylbiphenyl. While values of Km and Vmax of Hb and Hm are very similar, kcat values was 100 times higher with Hb than with Hm. But kcat value for Hb was much lower than that for lignin peroxidase H2. All the results above suggested that Hb-catalyzed reactions efficiently degrade BaP in aqueous condition. Thus, we suggest that Hb for oxygen carrier in blood could be employed as a biocatalyst (i.e., hemoglobin peroxidase) for BaP degradation in the environment, due to the high availability of Hb.

Sequential biowashing-biopile processes for remediation of crude oil contaminated soil in Kuwait.

The application of biological processes for remediation of the aged crude oil-contaminated soil of Kuwait can be an inefficient way, thus, this study developed 20 d-sequential biowashing and biopile processes where the biowashing step uses an enrichment culture of the indigenous soil bacterial community and the biopile step includes hemoglobin-catalyzed oxidation (HCO). The residual total petroleum hydrocarbons (TPH) concentrations and CO2 generation were measured to determine the removal efficiency, and the bacterial community changes were studied to investigate the effect of the sequential processes on the soil indigenous bacterial community. The enrichment culture grown on hemoglobin showed an increased surface activity, and this promoted desorption and emulsification of crude oil from the soil sample in the biowashing step resulting in 75% TPH removal. Potential surfactant-producing bacterial species were observed in the soil sample after biowashing. The HCO in the beginning of the biopile step removed 21% of the residual TPH, and further TPH removal was observed with a longer biopile period. Overall, the sequential biowashing and biopile processes removed 86% TPH. The results show that the developed sequential biowashing and biopile processes can be used to efficiently remediate the aged crude oil-contaminated soil of Kuwait.

Molecular-level investigation of soils contaminated by oil spilled during the Gulf War.

In this study, molecular-level chemical compositions of soils contaminated by oil spilled during the Gulf War were studied. Two soil samples, respectively collected at 0.1 m and between 0.5 and 1 m below the surface from an oil spill site, were extracted with organic solvents and water. The extracts were analyzed via ultrahigh resolution FT-ICR and two-dimensional gas chromatography/high resolution mass spectrometry. The data showed that the spilled oil was significantly affected by vaporization due to high surface temperatures in the desert. The data obtained with (+) atmospheric pressure photo ionization (APPI) and (-) electrospray ionization (ESI) coupled with ultrahigh resolution-mass spectrometry (UHR-MS) indicated that the degradation of aromatic compounds and increase in oxygen-containing classes occurred in the following order: surface soil > below surface soil > crude oil. The oxygenated compounds were confirmed by principal component analysis. The score and loading plots of Ox and SOx showed that they were the major contributors to differentiate the samples. However, a comparison with previously reported oceanic oil spills showed that less significant degradation occurred even after almost 30 years. Our data can provide an information basis for designing a strategy for clean-up and restoration efforts of Gulf War oil spills.

QSAR study using acute toxicity of Daphnia magna and Hyalella azteca through exposure to polycyclic aromatic hydrocarbons (PAHs).

Polycyclic aromatic hydrocarbons are organic chemicals consisting of a small number of benzene rings. PAHs are exposed to the environment by events such as Crude oil spills, even though they are substances present in the environment. Exposure of PAHs to the environment will affect not only the environment, but also the living organisms and the ecosystem as a whole. The effects of PAHs vary widely depending on the type of PAHs and have been studied for a long time. However, there are only 16 kinds of PAHs defined by US EPA, and there are more kinds of PAHs present in the environment. Therefore, it is time- and space-limited to judge the toxicity of all kinds of PAHs by evaluating them. In all cases, the tendency of research is shifting toward predicting toxicity evaluation through modeling rather than the direction of toxicity evaluation. In this study, we constructed a quantitative structure-activity relationship (QSAR) model, one of the molecular structure activation models, and predicted the correlation between the toxicity value and the logKow value of PAHs. Basically, as the logKow value increases, the median effective concentration (EC50) tends to decrease. Compared with the previous studies, Hyalella azteca showed this tendency, but Daphnia magna showed different results when exposed to Naphthalene. The RMSE(Root Mean Square Error) values of Daphnia magna and Hyalella azteca were 6.0049 and 5.9980, respectively, when the QSAR model was constructed using the toxicity data for PAHs. We confirmed the validity of the QSAR model in this study by comparing the results of exposing Daphnia magna to PAHs and the ECOSAR data, one of the existing models. The R2 value was found to be 0.9356. This study suggests that it may be helpful to predict the toxicity evaluation and to prepare countermeasures for accidents such as Crude oil spill. It is thought that if more data base is created by using additional types of PAHs and species in the same way as this study in the future, it will help to construct the modeling.

A study on the evaluation of water-bloom using image processing.

This study utilized remote sensing techniques using an unmanned aerial vehicle (UAV) with an attached multispectral sensor to monitor the Nakdong River. In this study, chlorophyll-a, an indicator of water quality and the normalization difference vegetation index (NDVI), which indicates the vitality of plant growth was employed. NDVI images were generated using georeferenced and Orthomosaic images. The data (field samples) used to conduct the study was collected in September 2017. The relationship between the chlorophyll-a concentrations and NDVI was then examined. The results of the relationship can be used in monitoring of green algae for water quality management.

Role of hemoglobin in hemoglobin-based remediation of the crude oil-contaminated soil.

This study investigated the changes in the indigenous microbial community structure with hemoglobin (Hb) application to determine the role of Hb in Hb-based remediation of crude oil-contaminated soil. The phylogenetic diversity of the bacterial community showed that the Hb addition selected surfactants-producing species, thereby, promoting TPH degradation. The significant increase in the CO2 generation, which can be related to the increase in the bacterial abundance inferred from the 16S rRNA gene copy number, supports the enhanced TPH degradation with Hb application. The similar residual TPH concentrations in the presence of only hydrogen peroxide (H2O2) and both Hb and H2O2 suggested that the role of Hb as a catalyst was not as significant as the role of Hb as a nutrient. Also, in the presence of H2O2, a greater recovery of the microbial community structure was observed with the double Hb injection than the single Hb injection. Overall, this study shows that the Hb-based remediation strategies via microbial metabolism can be successfully applied to remediate the crude-oil contaminated Kuwaiti soil.

Optimization of hydrogen peroxide-to-hemoglobin ratio for biocatalytic mineralization of polycyclic aromatic hydrocarbons (PAHs)-contaminated soils.

This study investigates the efficiency of hemoglobin (Hb)-catalyzed biocatalytic reactions for removal of polycyclic aromatic hydrocarbons (PAHs) in a historically PAHs-contaminated soil and of benzo(a)pyrene (BaP) in an artificially BaP-contaminated soil. PAHs removal tests at various H2O2-to-Hb mass ratios (0-3.7) showed that the PAHs removal was greater at H2O2-to-Hb mass ratio of ≥3. This was attributed to the greater removal of high molecular weight PAHs at higher H2O2-to-Hb mass ratios. The BaP removal increased from 36% to 85% with increasing H2O2-to-Hb mass ratio from 1 to 3, and further increase in H2O2-to-Hb mass ratio decreased the BaP removal. Thus, the optimal H2O2-to-Hb mass ratio for BaP removal was determined to be 3 in the artificially BaP-contaminated soil. The BaP removal in the presence of only Hb can be attributed to the capture of BaP by Hb. The increased BaP removal in the presence of H2O2 is likely due to BaP mineralization as the BaP removal and the CO2 generated showed a strong positive correlation (R2 = 0.999). Overall, this study shows that the Hb-catalyzed biocatalytic reactions can effectively remove PAHs in soil.

Toxicity identification and evaluation for the effluent from a nonmetallic mineral mining facility in Korea using D. magna.

Industrial wastewater has attracted increasing attention in recent years because of its impact on ecosystems and human health. Whole-effluent tests are generally used to monitor toxicities of unknown chemicals and conventional pollutants from industrial effluent discharges. This study described identification evaluation (TIE) procedures to determine the acute toxicity of a nonmetallic mineral mining facility effluent that was toxic to Daphnia magna. In the characterization step (TIE phase I), toxic effects of heavy metals, organic compounds, oxidants, volatile organic compounds, suspended solids, and ammonia were screened. Results revealed that the source of toxicity was beyond these toxicants. Chemical analysis (TIE phase II) of total dissolved solid showed that the concentration of chloride ion (15,302.5 mg/L) was substantially higher than the predicted EC50 value for D. magna. Chemical analysis for heavy metal and ionic materials used ion chromatography and induced coupled plasma-optic emission spectroscopy. In the confirmation step (TIE phase III), using spiking and deletion approaches, it was demonstrated that chloride ion was the main toxicant in this effluent. Concentrations of potassium (317.5 mg/L), magnesium (970.5 mg/L), sodium (8595.3 mg/L), and sulfate (2854.3 mg/L) were not high enough to cause toxicity to D. magna. Finally, we concluded that chloride was the main toxicant in the nonmetallic mineral mining facility effluent. Based on these results, advanced treatment processes such as ion exchange and reverse osmosis technology are recommended to treat wastewater in this and similar situations. Further research is needed to provide technical support for toxin identification and evaluation of various types of wastewater treatment plant discharge.