Soil Total Petroleum Hydrocarbon Research Articles

Enhanced bioremediation of oil-contaminated soil in a slurry bioreactor by H2O2-stimulation of oil-degrading/biosurfactant-generating bacteria: performance optimization and bacterial metagenomics.

Oil-contaminated soil is the main challenge for oil-rich countries, and this study aimed to investigate the performance of the H2O2-stimulated slurry bioreactor for the bioremediation of real oil-contaminated soil. The effect of biomass concentration, soil to water (S/W) ratio, slurry temperature, pH, and H2O2 concentration were optimized for the removal of total petroleum hydrocarbons (TPH) from oil-contaminated soil. TPH removal efficiency, biosurfactants production, and peroxidase and dehydrogenase activities were measured. The optimum conditions for the complete biodegradation of 32 [Formula: see text] in the slurry bioreactor during 6days were biomass of 2250mg/L, S/W ratio of 20%, the temperature of 30°C, pH of 7, and an H2O2 concentration of 120mg/L. The highest peroxidase, dehydrogenase, surfactin, and rhamnolipid formation were also obtained under optimum conditions. The results pointed out that complete biodegradation of 32g/kg of TPH in oil-contaminated soil at a short reaction time of 6days is achievable in the developed process operated under optimum conditions. The GC/FID analysis of solid and liquid phases showed that the bioprocess completely biodegraded the different TPH fractions. H2O2 efficiently stimulated the biosurfactant-generating bacteria to produce peroxidase and thereby accelerating the bioremediation rate. Accordingly, an H2O2-mediated slurry bioreactor inoculated with biosurfactant/peroxidase-generating bacteria is a promising technique for cleaning up oil-contaminated soils.

Fast biodegradation of long-chain alkanes in heavily polluted soil by improving C/H conversion after pre-oxidation

This study aimed to explore the effects of Fenton pre-oxidation under different conditions on the indigenous bacterial communities and the mechanism of soil C/H conversion and rapid degradation of long-chain alkanes. The soil total petroleum hydrocarbons (TPH) content for this study was 27998 ± 883 mg/kg of soil. The results showed that the half-life period of the rapid long-chain degradation group was 266 days faster than that of the slow long-chain degradation group. After pre-oxidation, the number of bacteria in the fast group (5.07 log CFU/g) was higher than slow group (2.57 log CFU/g). Further studies showed that the consumption of ammonia nitrogen in the long-chain rapid degradation group was 1.37 times higher than that in the long-chain slow degradation group. The mapping characterization by DEEM revealed a high level of humic acid-like and organic matter produced by microbial metabolism in the fast group, and the long-chain degradation group had higher C/H conversion (35%), thus improving the degradation rate of long-chain alkanes (47%). High biomass and ammonia nitrogen consumption promoted higher C/H conversion. After proper pre-oxidation, the bacterial community changed, with an average relative abundance of 34% for Actinobacteria. This study has good engineering application value.

Study on the Enhanced Remediation of Petroleum-Contaminated Soil by Biochar/g-C3N4 Composites.

This work developed an environmentally-friendly soil remediation method based on BC and g-C3N4, and demonstrated the technical feasibility of remediating petroleum-contaminated soil with biochar/graphite carbon nitride (BC/g-C3N4). The synthesis of BC/g-C3N4 composites was used for the removal of TPH in soil via adsorption and photocatalysis. BC, g-C3N4, and BC/g-C3N4 have been characterized by scanning electron microscopy (SEM), Brunauer–Emmett–Teller surface area analyzer (BET), FT-IR, and X-ray diffraction (XRD). BC/g-C3N4 facilitates the degradation due to reducing recombination and better electron-hole pair separation. BC, g-C3N4, and BC/g-C3N4 were tested for their adsorption and photocatalytic degradation capacities. Excellent and promising results are brought out by an apparent synergism between adsorption and photocatalysis. The optimum doping ratio of 1:3 between BC and g-C3N4 was determined by single-factor experiments. The removal rate of total petroleum hydrocarbons (TPH) by BC/g-C3N4 reached 54.5% by adding BC/g-C3N4 at a dosing rate of 0.08 g/g in a neutral soil with 10% moisture content, which was 2.12 and 1.95 times of BC and g-C3N4, respectively. The removal process of TPH by BC/g-C3N4 conformed to the pseudo-second-order kinetic model. In addition, the removal rates of different petroleum components in soil were analyzed in terms of gas chromatography–mass spectrometry (GC-MS), and the removal rates of nC13-nC35 were above 90% with the contaminated soil treated by BC/g-C3N4. The radical scavenger experiments indicated that superoxide radical played the major role in the photocatalytic degradation of TPH. This work definitely demonstrates that the BC/g-C3N4 composites have great potential for application in the remediation of organic pollutant contaminated soil.

A Review of Techniques for the Determination of Total Petroleum Hydrocarbons in Soils

The Total Petroleum Hydrocarbon (TPH) is the total of different types of hydrocarbons in the crude oil mixture. It includes volatile petroleum hydrocarbons and extractable petroleum hydrocarbons. The TPH determination techniques are primarily grouped into spectroscopic (ultraviolet spectroscopy, raman spectroscopy, fluorescence spectroscopy, infrared spectroscopy) and non- spectroscopic (gravimetric, immunoassay, gas chromatography with mass spectrometric detection (GC/MSD), gas chromatography with flame ionization detection (GC-FID)) techniques. Solvent and the sample characteristics determine the efficiency of the techniques. This paper compares spectroscopic (fourier transform infrared spectroscopy and ultraviolet spectroscopy) and non-spectroscopic (gravimetric and gas chromatography) methods in the determination of TPH in soil. Spectroscopic and non-spectroscopic techniques are efficient, but the paper recommends spectroscopic techniques because the techniques are efficient with small operational time, and are safer in occupational health and safety issues. In addition their results are accurate and reliable.

Petroleum‐contamination drives the shift of microbiome through modifying soil metallome

AbstractSoil oil‐pollution is one of the most severe environmental issues at present. Shifts of soil metallome and microbiome are essential indicators for risk assessment and remediation of field soil pollutions. However, how soil metallome and microbiome react to petroleum‐contamination is not well studied. In this research, soil samples were collected from a short‐term and long‐term petroleum‐contaminated oil field. The soil physicochemical properties, metallome, microbiome, and soil microbial networks were investigated. Results showed that the contents of soil total petroleum hydrocarbon, total carbon, total nitrogen, total sulfur, total phosphorus, calcium, copper, manganese, lead, and zinc were increased by petroleum‐contamination because petroleum is rich in these elements. In contrast, the soil pH was lowered resulting from soil sulfur oxidation regardless of the petroleum pollution duration. Petroleum‐contamination also reduced bacterial and fungal α‐diversity indices because of the selective pressure of petroleum. Furthermore, bacterial α‐diversity was negatively correlated with soil total petroleum hydrocarbon content and electrical conductivity, and fungal α‐diversity was negatively correlated with soil electrical conductivity. Moreover, the relative abundances of Proteobacteria, Ascomycota, Oleibacter, and Fusarium in soil were increased by petroleum‐contamination. Network analysis showed that number of links, modules, and the network invulnerability decreased in short‐term contaminated soil, followed by the long‐term contaminated group, and the main reason should be the environmental disturbance caused by petroleum‐contamination. These results demonstrate that short‐term heavy petroleum contamination can cause shifts in soil physicochemical properties, metallome, and microbiome and assemble a less complex and vulnerable soil microbial network. Moreover, natural restoration can hardly amend soil properties and microbial network structure. This research emphasizes that the uncommonly studied soil metallome may play a vital part in the reaction of microbial communities to petroleum‐contamination.

The effect of different in situ chemical oxidation (ISCO) technologies on the survival of indigenous microbes and the remediation of petroleum hydrocarbon-contaminated soil

This study determines the effect of different in situ chemical oxidation (ISCO) technologies on soil microorganisms and total petroleum hydrocarbon (TPH) degradation. Permanganate is a moderate oxidant to the intrinsic microbes while persulfate causes severe bacterial death. TPH removal in the persulfate and permanganate systems is similar, which is higher than that in the hydrogen peroxide system. Permanganate is the most suitable oxidant for ISCO, followed by in situ bioremediation because of its persistence and low toxicity. Chemical oxidation dominates the removal of TPH throughout the experiment in the persulfate systems and during the initial stage in the hydrogen peroxide and permanganate systems. The toxicity of different catalysis/activation methods to in situ microbes decreases in the order: heat> Fe2+/citric acid> Fe2+>no catalysis/activation. If ferrous iron or citric acid is used to catalyze hydrogen peroxide, the pH must be controlled to prevent severe damage to the microbes. There is more dissolved organic carbon in solution in oxidation systems, which shows that the addition of an oxidant increases the solubility and bioavailability of the contaminant. Petroleum degraders are present in the contaminated soil and the addition of oxidants changes indigenous bacterial communities significantly.

Synergetic effects of microbial-phytoremediation reshape microbial communities and improve degradation of petroleum contaminants

Microbial-phytoremediation is an effective bioremediation technology that introduces petroleum-degrading bacteria and oil-tolerant plants into oil-contaminated soils in order to achieve effective degradation of total petroleum hydrocarbons (TPH). In this work, natural attenuation (NA), microbial remediation (MR, using Acinetobacter sp. Tust-DM21), phytoremediation (PR, using Suaeda glauca), and microbial-phytoremediation (MPR, using both species) were utilized to degrade petroleum hydrocarbons. We evaluated four different biological treatments, assessing TPH degradation rates, soil enzyme activities, and the structure of microbial community in the petroleum-contaminated soil. This finding revealed that the roots of Suaeda glauca adsorbed small amounts of polycyclic aromatic hydrocarbons, causing the structure of soil microbiota community to reshape. The abundance of petroleum-degrading bacteria and plant growth-promoting rhizobacteria (PGPR) has increased, as has microbial diversity. According to correlation research, these genera increased soil enzyme activity, boosted the number of degradation-functional genes in the petroleum hydrocarbon degradation pathway, and accelerated the dissipation and degradation of TPH in petroleum-contaminated soil. This evidence contributes to a better understanding of the mechanisms involved in the combined microbial-phytoremediation strategies for contaminated soil, specifically the interaction between microflora and plants in co-remediation and the effects on the structural reshaping of rhizosphere microbial communities.

Assessment of Ni Toxicity to Fungi and Bacteria in Oil Tainted Soils in Greater Port Harcourt Area, Nigeria


 
 
 Intensified urbanization and industrialization are rapidly triggering the release of pollutants to the environment. This study determined the extent of soil contamination with Nickel (Ni) in oil mining areas and its effect on the levels of Ni tolerance by fungi and bacteria. The total CFUs/g of soil were enumerated after a culture period of 7 days at 28°C and LC50 was determined using probit and regression analysis. The mean values of Ni were 1.38±0.23 in industrial area, 1.41±0.36 ppm in agricultural area and 1.02±0.64 in urban area. The mean values of Total Petroleum Hydrocarbon (TPH) were 4,405.46 ppm in industrial area, 55.65 ppm in agricultural area and 1,304.53 ppm in urban area. Nickel’s peak concentration indicating growth of both fungi and bacteria at 150 ppm. There was significant difference (p ≤ 0.000) in the mean levels of LC50 for fungi among the study sites. There was no significant correlation between the concentration of TPH in soil and LC50 of fungi (r = -0.169) and bacteria (r = 0.042). In conclusion, TPH influenced the levels of fungi and bacteria tolerance to Ni in soils. Moreover, it was observed that LC50 can be a reliable method for monitoring chemically resistant microorganisms directly in the environment to improve the use of microorganisms for the bioremediation of oil contaminated soils and in monitoring of antibiotic resistant microorganisms in natural ecosystems.
 
 

Physicochemical Indices of Phyto Remediated Hydrocarbon Polluted Soil and the Effect of Bio-nutrient Amendment

Aim: To assess the Physicochemical indices of Phytoremediated Crude Oil polluted amended soil using grass plant Cyperus esculentus (Cyp) and Phyllanthus amarus (Phy).
 Study Design: The study employs experimental design, statistical analysis of the data and interpretation.
 Place and Duration of Study: Rivers State University demonstration farmland in Nkpolu- Oroworukwo, Mile 3 Diobu area of Port Harcourt, was used for this study. The piece of land is situated at Longitude 4°48’18.50” N and Latitude 6ᵒ58’39.12” E measuring 5.4864 m x 5.1816 m with a total area of 28.4283 square meter. Phytoremediation process monitoring lasted for 240 days; analyses were carried out monthly at 30 days’ interval.
 Methodology: The study was carried out on Crude Oil Polluted soil (PS) amended with bio-nutrient supplements (Spent Mushroom Substrate (SMS) and selected fungi (Aspergillus niger(AN) andMucor racemosus (MR)) used to stimulate and augment the indigenous microbial population present in a crude oil polluted soil thereby enhancing hydrocarbon reduction in pari per sue with phytoremediation (uptake of Crude oil by test plants) over a period of 240 days. Ten (10) experimental plots (two Control (Unpolluted and polluted soil without amendment) and eight polluted amended/treated plots) employing Randomized Block Design (each having dimensions: 100 x 50 x 30 cm LxBxH); formed and mapped out on agricultural soil and left fallow for 6 days before contamination on the seventh day; after which it was allowed for 21 days for proper contamination and exposure to natural environmental factors (to mimic soil crude oil spill site); thereafter nutrients/organics (biostimulating agents) and bioaugmenting organisms were applied. Baseline studies were carried out on soil profile before and after contamination, major parameters monitored and assayed were Total Petroleum Hydrocarbon (TPH) uptake by plant roots and stem, Polycyclic Aromatic Hydrocarbons (PAHs) and TPH reduction in soil. Other physicochemical properties analyzed in the soil from different plots were pH, Electrical Conductivity, Moisture Content, Total Nitrogen, Available Phosphorus, Potassium, Total Organic Carbon, Plant Height, Iron, Lead and Zinc at regular intervals; days 1, 60, 90, 120, 150, 180, 210 & 240. The rate of phytoremediation was estimated from percentage (%) uptake of Total petroleum hydrocarbon (TPH) in plant roots and stem from day 1 -240; while percentage (%) reduction of TPH and PAHs in soil was estimated from day 1 to the residual at day 240.
 Results: The test plants decreased significant amount of crude oil as revealed in TPH uptake in their roots and Stem. Mean amount and percentage Total Petroleum Hydrocarbon (TPH) uptake by Cyperus esculentus roots and stem were; 152.33±50.34mg/kg, 12.57±4.16% and 201.13±8.80mg/kg, 13.27±0.58% respectively; while that of Phyllanthus amarusroots and stem were 141.50±35.62mg/kg, 11.68±2.94% and 174.44±19.98mg/kg, 11.51±1.32% respectively; revealing higher Uptake of TPH in plant stem than roots. From the initial TPH contamination value of 5503.00mg/kg, it was observed that plots planted with Cyperus esculentus (TPH 5492.75±76.36mg/kg) showed higher reduction of TPH from soil than those planted with Phyllanthus amarus(TPH 5449.72±18.27mg/kg); while PAHs degradation/reduction showed a reverse trend with plots planted with Phyllanthus amarus (PAHs 28.72±2.74mg/kg; 60.46±5.77%) higher than plots planted with Cyperus esculentus
 s (PAHs 25.77±2.12mg/kg, 54.24±4.47%).
 Conclusion: Plots planted with Cyperus esculentus showed higher reduction of TPH from soil than those planted with Phyllanthus amarus while PAHs degradation/reduction in plots planted with Phyllanthus amarus was higher than plots planted with Cyperus esculentus. TPH uptake was higher in plant stems than roots; more so, plots amended with nutrient supplements showed significant higher percentage reduction in hydrocarbon in the polluted soil than unamended polluted soil. It is therefore recommended that Cyperus esculentus is a suitable plant species for phytoremediation of crude oil contaminated soil with high TPH value while Phyllanthus amarusis the best option in phytoremediation of polluted soil with high PAHs value, both in combination with bio-nutrient supplement.

Assessing the degradation potential of light petroleum hydrocarbons using bacterial activity (Pseudomonas aeruginosa) and root exudate of Conocarpus (Conocarpus erectus)

Petroleum hydrocarbons are one of the most common environmental pollutants, leading to serious environmental problems; and phytoremediation is an environmentally friendly way to remove petroleum pollutants from the soil. This research was designed based on the relatively high salinity of Ahwaz soil, the resistance of Conocarpus to soil salinity, and the presence of Pseudomonas bacteria in most environments. The aim of this study was to assess the effect of Conocarpus erectus and Pseudomonas aeruginosa on the removal efficiency of total petroleum hydrocarbons (TPHs) from contaminated soils with Bangestan crude oil in the phytoremediation process during 275 days under non-laboratory condition. After pedological studies and the selection of evaporation pond in crude oil desalination plant with suitable conditions for phytoremediation, this study was conducted in a factorial experiment with two factors based on completely randomized design with three replications. The factors used in this experiment include the treatment types (plant, bacteria, plant–bacteria cultivated in the soil, and soil with no plant and bacteria (control)) and the concentration of contaminant (Bangestan crude oil) with 5 levels (0, 0.5, 1, 2.5 and 5 wt%). TPHs were measured in soil samples collected from the rhizosphere of Conocarpus using gas chromatography with a flame ionization detector (GC-FID). The degradation rate of TPHs in soil with Conocarpus, Pseudomonas, and Conocarpus-Pseudomonas was 38.1%, 35.95%, and 70.54%, respectively. The results of the experimental factors showed that although plant and bacteria individually had a positive effect on the degradation of TPHs, the combination of bacteria and plants led to a more positive and significant effect on the degradation of TPHs ( P < 0 . 05 ).

Biogenic iron oxide nanoparticles and activated sodium persulphate for hydrocarbon remediation in contaminated soil

Biogenic iron oxide nanoparticles synthesized from a locally sourced, readily available plant — Azadirachta indica, were used synergistically with sodium persulphate (PS) to degrade total petroleum hydrocarbons (TPHs) in contaminated soil. A chemometric approach to optimizing the conditions for the degradation of TPH was developed using central composite design (CCD). Characterization of iron oxide nanoparticles was carried out with X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and selected electron area diffraction (SAED). Analysis of TPH was carried out with gas chromatography flame ionization detector (GC-FID). The optimum condition for the complete degradation of TPH was achieved at pH 6.0 and oxidant dosage of 0.74 M within 14 h and 5 days. Iron nanoparticles AZA FeNP (1:1) and AZA FeNP (2:1) were synthesized by varying the ratio of extract/precursor. The nanoparticles displayed heterogeneous, amorphous morphology with increased agglomeration in AZA FeNP (1:1). AZA FeNP (2:1) XRD spectra exhibited characteristic peaks at 27.0°, 35.4° and 44.5°, which are attributed to iron nanoparticles. TEM and HR-TEM images confirmed spherical nanoclusters’ presence with an average size of 9.3 and 10.0 nm for AZA FeNP (1:1) and AZA FeNP (2:1), respectively. The EDX spectra displayed intense peaks of oxygen, carbon, and iron at 0.4, 0.6 and 6.4 KeV confirming the presence of FeNP. Under optimized conditions, PS alone degraded 68% TPH while 0.07 and 0.15 g/L FeNP achieved ∼93 and 95% degradation, respectively. Additionally, 0.07 and 0.15 g/L FeNP-activated PS achieved ∼99 and 100% TPH degradation, respectively. The outcome of these findings suggests that FeNP synthesized using A. indica successfully catalyzed PS for complete degradation of TPH in crude oil-contaminated soil.

Organic stimulants for enhancing phytoremediation of crude oil polluted soil: A study on cowpea

Petroleum hydrocarbon (PH) contamination of soils remains a major threat to environmental health and food security. A two-years phytoremediation study was conducted on a crude oil polluted soil to assess changes in soil total petroleum hydrocarbon concentration (TPHsoil) following use of pawpaw seed powder (PSP), moringa seed powder (MSP) and their combination (PSP + MSP) as organic stimulants in cowpea cultivation. The stimulants were tested at different application rates (100, 150, 200 and 250 g m−2), with the control (No stimulant) for their effectiveness in reducing TPHsoil and accelerating the removal rate (R) of PH from soil. The TPHsoil did not differ significantly (p < 0.05) among the treatments in year 1, but was highest in the control (11,600 mg kg−1) and least in 200 g m−2 PSP (7400.0 mg kg−1). In year 2, mean TPHsoil varied significantly (p < 0.05) and remained highest in control (7100 mg kg−1) but lowest in 150 g m−2 PSP (2700 mg kg−1). Application of 150 g m-2 PSP gave the highest R (78.2%), followed by 150 g m-2 PSP+MSP (77.4%), and least by the control (42.7%) over two years of study. The average fresh pod yield of cowpea over two years was highest in 250 g m−2 PSP (2416.67 kg ha−1), followed by 150 g m−2 PSP (2173.34 kg ha−1) and least in control (1302.22 kg ha−1). There was significant negative association between TPHsoil and fresh pod yield (r = −0.403; p < 0.01). However, application of 150 g m−2 PSP appeared most effective for enhanced phytoremediation of crude oil polluted soil and improvement of cowpea yield.

Soil microbial community and association network shift induced by several tall fescue cultivars during the phytoremediation of a petroleum hydrocarbon-contaminated soil

Biodegradation of soil contaminants may be promoted near plant roots due to the “rhizosphere effect” which may enhance microbial growth and activity. However, the effects of different plant cultivars within a single species on degradation remains unclear. Here, we evaluated the removal of soil total petroleum hydrocarbons (TPHs) by ten different cultivars of tall fescue grass (Festuca arundinacea L.) and their associated rhizosphere microbiomes. TPH removal efficiency across the ten different cultivars was not significantly correlated with plant biomass. Rhizing Star and Greenbrooks cultivars showed the maximum (76.6%) and minimum (62.2%) TPH removal efficiencies, respectively, after 120 days. Significant differences were observed between these two cultivars in the composition of rhizosphere bacterial and fungal communities, especially during the early stages (day 30) of remediation but the differences decreased later (day 90). Putative petroleum-degrading bacterial and fungal guilds were enriched in the presence of tall fescue. Moreover, the complexity of microbial networks declined in treatments with higher TPH removal efficiency. The relative abundances of saprotrophic fungi and putative genes alkB and C12O in bacetria involved in petroleum degradation increased, especially in the presence of Rhizing Star cultivar, and this was consistent with the TPH removal efficiency results. These results indicate the potential of tall fescue grass cultivars and their associated rhizosphere microbiomes to phytoremediate petroleum hydrocarbon-contaminated soils.

Remediation of Crude Oil Contaminated Soil, Using Organic Supplement: Effects on Growth and Heavy Metal Uptake in Cassava (Manihot esculenta Crantz)

Field experiments were conducted in 2016 and repeated in 2017 to evaluate the effectiveness of Oil Palm Bunch Ash (OPBA) and Dried Poultry manure (DPM) as organic supplement, applied singly and in combination on growth properties and heavy metal uptake of cassava cultivars grown in crude-oil contaminated soil of the Niger Delta Region, Nigeria. There were four different organic amendments viz: DPM, OPBA, OPBA +DPM and control using TMS 30572, NR8082 and local variety as test crops. Results were elaborated statistically with the use of three-by-four factor variance analysis with ANOVA. Effect of various application of amendment on morphometric parameters of cultivars revealed in 2017 that at 36 weeks after sprouting (WAS), DPM and OPBA +DPM significantly (P≤ 0.05) enhanced plant heights of TMS 3572 and LV but had no influence on number of nodes, stem girth and leaf area. However, the interactions resulted in significant (P≤ 0.05) uptake and concentration of the heavy metals Fe, Cu, and Pb in leaves and Fe in roots ofTMS30572 and NR8082, indicating efficient metal removal by these varieties. Results of amendment also revealed remarkable increment in bacterial and fungal (from 104 to 106 and 103 to 104 ) populations respectively, correlating with reduction in soil total petroleum hydrocarbon (TPH) from 156.45 mg/kg to 146.73 mg/Kg. This is observed to diminish oil toxicity and improve soil status. The response of these cassava varieties to crude oil contamination appears to be optimistic. Consequently crop farmers are adviced against planting cassava and other arable crop at crude oil impacted soil for the risk of uptake of heavy metal in crop tissues. &#x0D; Keywords: Remediation, Heavy metal, Oil-contaminated soil, Organic amendment, Growth properties, Cassava

Bioremediation of diesel polluted soils with Eichhornia crassipes (water hyacinth)

Diesel oil contamination is a growing environmental concern in most crude oil processing regions of the world. This study assessed the efficacy of both fresh and powdered Eichhornia crassipes (water hyacinth) as potential biostimulants in the remediation of diesel oil contaminated soils using three test concentrations (50 g, 100 g and 150 g) and a control (0 g). The remediation process was monitored by assaying the total organic carbon (TOC), total petroleum hydrocarbon (TPH), and soil pH before and after amendment with the fresh and powdered E. crassipes for 90 days. The result showed increase in soil pH, TOC, TPH and volatile matter (VM) in comparison with the control due to soil contamination by diesel oil. However, there was a significant reduction (p &lt; 0.05) in soil pH and TOC with the introduction of fresh and powdered E. crassipes at different concentrations. Contaminated soil amended with 100 g of fresh E. crassipes showed the highest TOC loss (59.7%) alongside soil amended with 100 g of powdered E. crassipes (47.36%) while the control showed the least TOC loss (0.91%). Similarly, soil TPH decreased significantly across all concentrations after amendment (p &lt; 0.05). Overall, soil amended with fresh E. crassipes showed higher TPH loss than soil amended with powdered E. crassipes. This study reveals the potentials of using E. crassipes in the remediation of diesel oil contaminated soils. Above all, we demonstrate that fresh E. crassipes is a potentially stronger biostimulant than powdered E. crassipes.

Stimulating the Rate of Phytoremediation of Chromolaena odorata in Crude Oil Contaminated Soil Using Inorganic Urea

Investigation on the use of urea in stimulating the phytoremediation of Chromolaena odorata in a crude oil contaminated soil was carried out at a crude oil spilled site at Botem-Tai, Ogoni, Nigeria. Three phytoremediation treatments labeled A – C in addition to the control (D) were used. The treatments were: A (Chromolaena odorata only), B (Chromolaena odorata + 20 g/m2 urea), C (Chromolaena odorata + 40 g/m2 urea), D (polluted soil without phytoremediation) arranged using Latin Square Design (LSD). Total petroleum hydrocarbon (TPH) and Total hydrocarbon content (THC) in soil and plant samples from the different treatment plots in addition to other soil nutrients were analyzed. The percentage reduction in TPH and THC in soil were as follows: Treatment B, {TPH (92.08%) and THC (95.37%)} &gt; treatment A {TPH (88.95%) and THC (93.37%)}&gt; C {TPH (78.78%) and THC (83.29%)} &gt; Control {TPH (14.76%) and THC (32.90%)}. Treatment C had the highest TPH (2.67 mg/kg) and THC (20.57 mg/kg) accumulation in test plant. Combining stimulant (urea) with phytoremediation also improved soil properties such as pH, Nitrogen and Potassium. With the highest reduction of TPH and THC in treatment B (phytoremediation with 20 g/m2 urea) than other treatments is an indication that low concentration of urea has a stimulatory effect on phytoremediation of crude oil by Chromolaena odorata.

Removal of TPH, UCM, PAHs, and Alk-PAHs in oil-contaminated soil by thermal desorption

Oil-contaminated soils from a former landfill and gas station site in Korea were treated by thermal desorption. The removal efficiencies of the different oil components such as total petroleum hydrocarbons (TPH), polyaromatic hydrocarbons (PAHs), unresolved complex mixtures (UCM), and alkylated PAHs (Alk-PAHs) by thermal desorption were determined. The effects of temperatures (200, 400, and 600 °C) and treatment times (15, 30, 45, and 60 min) on the thermal desorption efficiency were studied. The treatment efficiency increased with increasing temperature from 200 to 400 °C and with increasing treatment time. Almost complete removals of TPH, UCM, PAHs, and Alk-PAHs were observed after 15 min at 400 °C. The treatment temperatures of 400 and 600 °C did not show a significant difference (p-value > 0.05). Overall, this study shows that the different components of oil in the oil-contaminated soils can be treated effectively in a relatively short time by thermal desorption, and such high removal efficiency in a relatively short time for the oil-contaminated soils can be of advantage for the treatment of highly contaminated or weathered soils where biological treatment efficiency is low.

Spatial ecological risk assessment for contaminated soil in oiled fields

Soil total petroleum hydrocarbon (TPH) pollution in oil fields is a worldwide environmental problem. In particular, the dense distribution of oil wells in low-permeability oil reservoirs has caused regional pollution superposition. We proposed a feasible method for the spatial ecological assessment for soil pollution in oil fields. Typical TPH-contaminated soil in the Shengli oil field was examined according to the classification of oil well properties, including the spatial structure, distribution density, and exploitation history. Soil TPH concentrations of each oil filed site was calculated by Monte Carlo simulation. The risks were assessed according to multiple receptors and risk sources. The results indicated that the average TPH concentration was greater than 2100 mg·kg−1. The differences of TPH concentrations were mainly correlated to the exploitation period. The soil TPH content demonstrated a spatial cluster pattern according to the Anselin Local Moran’s Index (p < 0.01). The risk for wheat and earthworms showed that more than 98% of the study area was under a low risk level. However, high risk accounted for only 0.9% when bacteria was used as a bioindicator, and the composition of different risk levels was similar to that of the ecological risk assessed based on the soil quality index.

Effects of Oil Pollution on Indigenous Bacterial Diversity and Community Structure of Soil in Fushun, Liaoning Province, China

Four hundred fifty four pyrosequencing was used to analyze the microbial community and diversity of oily farmland soil from Fushun, Liaoning Province, China. The results showed that a total of 114 Phyla, 262 Classes, 430 Orders, 685 Families, 869 Genera, and 294 Species were detected and summarized in the soil microbe. The petroleum hydrocarbons significantly changed the structure and diversity of soil microbial communities. Proteobacteria, Bacteroidetes, Actinobacteria, Acidobacteria, Gemmatimonadetes, Nitrospirae, Firmicutes, Verrucomicrobia, Elusimicrobia became the dominant flora in oil-contaminated areas. And the changes in the main bacterial flora in the soil were highly correlated with soil TPH (total petroleum hydrocarbon), pH and SOM (soil organic matter). The prediction of community metabolism function exhibited that 8 KEGG pathways were significantly enriched in petroleum contaminated soil, and the abundance of Proteobacteria, Moraxellaceae, Enterobacteriales and Sphingobacteriales significantly decreased under the stress of oil pollution. This research provided a theoretical and technical basis for the development and application of functional strains in the future.

Enhanced degradation of total petroleum hydrocarbons in real soil by dual-frequency ultrasound-activated persulfate

Ultrasound (US) can be employed to activate persulfate (PS) for degrading total petroleum hydrocarbons (TPH). In this study, to improve the degradation efficiency, PS is combined with dual-frequency US (DFUS) towards synergistic degradation of TPH in real soil. After 180 min, the degradation percentages for DFUS/PS, DFUS, high-frequency US and high-frequency US/PS are around 88.9%, 38.7%, 7.3% and 54.2%, respectively. Additionally, the influence of US power, PS content, slurry pH and temperature, and TPH components on the degradation percentage in the DFUS/PS process are explored. Scanning electron microscopy (SEM) images and the results of specific surface area verify that the DFUS can break the soil aggregates more effectively than the single-frequency US, and thus enhance the TPH desorption and accelerate the oxidant diffusion. Moreover, the investigation of the mechanism is further evaluated through quenching and electron spinning resonance spectrum (ESR) tests. The results indicate that the generation of SO4− and OH in DFUS/PS is ~1.6 times and ~2.5 times as much, respectively, as in high frequency US/PS. The relative contributions to the synergistic TPH degradation in the DFUS/PS system are: SO4− (PS activation via the heat induced by US) > pyrolysis inside the bubbles (hydrophobicity of TPH) > SO4− (PS activation via US cavitation) >OH. Finally, the hypothesis is confirmed via the evaluation of the degradation kinetics, which shows that the combined process of DFUS/PS is not a simple addition of the US and PS, but provides a highly effective process of synergistic degradation.