Total Petroleum Hydrocarbon Degradation Research Articles

Biochar-bacteria-plant combined potential for remediation of oil-contaminated soil

Oil pollution is a common type of soil organic pollution that is harmful to the ecosystem. Bioremediation, particularly microbe-assisted phytoremediation of oil-contaminated soil, has become a research hotspot in recent years. In order to explore more appropriate bioremediation strategies for soil oil contamination and the mechanism of remediation, we compared the remediation effects of three plants when applied in combination with a microbial agent and biochar. The combined remediation approach of Tagetes erecta, microbial agent, and biochar exhibited the best plant growth and the highest total petroleum hydrocarbons degradation efficiency (76.60%). In addition, all of the remediation methods provided varying degrees of restoration of carbon and nitrogen contents of soils. High-throughput sequencing found that microbial community diversity and richness were enhanced in most restored soils. Some soil microorganisms associated with oil degradation and plant growth promotion such as Cavicella, C1_B045, Sphingomonas, MND1, Bacillus and Ramlibacter were identified in this study, among which Bacillus was the major component in the microbial agent. Bacillus was positively correlated with all soil remediation indicators tested and was substantially enriched in the rhizosphere of T. erecta. Functional gene prediction of the soil bacterial community based on the KEGG database revealed that pathways of carbohydrate metabolism and amino acid metabolism were up-regulated during remediation of oil-contaminated soils. This study provides a potential method for efficient remediation of oil-contaminated soils and thoroughly examines the biochar–bacteria–plant combined remediation mechanisms of oil-contaminated soil, as well as the combined effects from the perspective of soil bacterial communities.

Costus speciosus (Koen ex. Retz.) Sm.: a suitable plant species for remediation of crude oil and mercury-contaminated soil.

The aim of this study was to evaluate the efficiency of Costus speciosus (Koen ex. Retz.) Sm. in the degradation of crude oil and reduction of mercury (Hg) from the contaminated soil in pot experiments in the net house for 180days. C. speciosus was transplanted in soil containing 19150mgkg-1 crude oil and 3.2mgkg-1 Hg. The study includes the evaluation of plant biomass, height, root length, total petroleum hydrocarbon (TPH) degradation, and Hg reduction in soil, TPH, and Hg accumulation in plants grown in fertilized and unfertilized pots, chlorophyll production, and rhizospheric most probable number (MPN) at 60-day interval. The average biomass production and heights of C. speciosus in contaminated treatments were significantly (p < 0.05) lower compared to the unvegetated control. Plants grown in contaminated soil showed relatively reduced root surface area compared to the uncontaminated treatments. TPH degradation in planted fertilized, unplanted, and planted unfertilized pot was 63%, 0.8%, and 38%, respectively. However, compared to unvegetated treatments, TPH degradation was significantly higher (p < 0.05) in vegetated treatments. A comparison of fertilized and unfertilized soils showed that TPH accumulation in plant roots and shoots was relatively higher in fertilized soils. Hg degradation in soil was significantly (p < 0.05) more in planted treatment compared to unplanted treatments. The fertilized soil showed relatively more Hg degradation in soil and its accumulation in roots and shoots of plants in comparison to unfertilized soil. MPN in treatments with plants was significantly greater (p < 0.05) than without plants. The plant's ability to produce biomass, chlorophyll, break down crude oil, reduce Hg levels in soil, and accumulate TPH and Hg in roots and shoots of the plant all point to the possibility of using this plant to remove TPH and Hg from soil.

Unveiling the capacity of bioaugmentation application, in comparison with biochar and rhamnolipid for TPHs degradation in aged hydrocarbons polluted soil

Persistent, aged hydrocarbons in soil hinder remediation, posing a significant environmental threat. While bioremediation offers an environmentally friendly and cost-effective approach, its efficacy for complex contaminants relies on enhancing pollutant bioavailability. This study explores the potential of immobilized bacterial consortia combined with biochar and rhamnolipids to accelerate bioremediation of aged total petroleum hydrocarbon (TPH)-contaminated soil. Previous research indicates that biochar and biosurfactants can increase bioremediation rates, while mixed consortia offer sequential degradation and higher hydrocarbon mineralization. The present investigation aimed to assess whether combining these strategies could further enhance degradation in aged, complex soil matrices. The bioaugmentation (BA) with bacterial consortium increased the TPHs degradation in aged soil (over 20% compared to natural attenuation - NA). However, co-application of BA with biochar and rhamnolipid higher did not show a statistically prominent synergistic effect. While biochar application facilitated the maintenance of hydrocarbon degrading bacterial consortium in soil, the present study did not identify a direct influence in TPHs degradation. The biochar application in contaminated soil contributed to TPHs adsorption. Rhamnolipid alone slightly increased the TPHs biodegradation with NA, while the combined bioaugmentation treatment with rhamnolipid and biochar increased the degradation between 27.5 and 29.8%. These findings encourage further exploration of combining bioaugmentation with amendment, like biochar and rhamnolipid, for remediating diverse environmental matrices contaminated with complex and aged hydrocarbons.

Activation of persulfate by g-C3N4/nZVI@SBC for degradation of total petroleum hydrocarbon in groundwater

In this study, we synthesized a high removal efficiency catalyst using biochar-supported nanoscale zero-valent iron and g-C3N4, denoted as g-C3N4/nZVI@SBC, to activate persulfate (PS) for the degradation of total petroleum hydrocarbon (TPH) in groundwater. We characterized the morphology and physiochemical properties of g-C3N4/nZVI@SBC with scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), BET surface area analysis, and X-ray photoelectron spectroscopy (XPS). To assess the performance of the g-C3N4/nZVI@SBC catalyst, we investigated various reaction parameters, such as the mass ratio of g-C3N4 to nZVI@SBC, PS concentration, initial pH, initial TPH concentration, and the presence of coexisting ions in the system. The results from batch experiments and repeated use trials indicate that g-C3N4/nZVI@SBC exhibited both excellent catalytic activation capability and impressive durability, making it a promising choice for TPH degradation. Specifically, when the PS concentration reached 1 mM, the catalyst dosage was 0.3 g/L, and the g-C3N4 to nZVI@SBC mass ratio was 2, we achieved a remarkable TPH removal efficiency of 93.8%. Through electron paramagnetic resonance (EPR) testing and quenching experiments, we identified sulfate radicals, hydroxyl radicals, and superoxide radicals as the primary active substance involved in the TPH degradation process. Moreover, the g-C3N4/nZVI@SBC composite proved highly effective for in-situ TPH removal from groundwater and displayed an 86% removal rate, making it a valuable candidate for applications in permeable reactive barriers (PRB) aimed at enhancing environmental remediation. In summary, by skillfully utilizing g-C3N4/nZVI@SBC, this study has made notable advancements in synthesis and characterization, presenting a feasible and innovative approach to addressing TPH pollution in groundwater.

Bioaugmentation and vermicompost facilitated the hydrocarbon bioremediation: scaling up from lab to field for petroleum-contaminated soils.

The biodegradation of total petroleum hydrocarbon (TPH) in soil is very challenging due to the complex recalcitrant nature of hydrocarbon, hydrophobicity, indigenous microbial adaptation and competition, and harsh environmental conditions. This work further confirmed that limited natural attenuation of petroleum hydrocarbons (TPHs) (15% removal) necessitates efficient bioremediation strategies. Hence, a scaling-up experiment for testing and optimizing the use of biopiles for bioremediation of TPH polluted soils was conducted with three 500-kg pilots of polluted soil, and respective treatments were implemented: including control soil (CT), bioaugmentation and vermicompost treatment (BAVC), and a combined application of BAVC along with bioelectrochemical snorkels (BESBAVC), all maintained at 40% field capacity. This study identified that at pilot scale level, a successful application of BAVC treatment can achieve 90.3% TPH removal after 90 days. BAVC's effectiveness stemmed from synergistic mechanisms. Introduced microbial consortia were capable of TPH degradation, while vermicompost provided essential nutrients, enhanced aeration, and, potentially, acted as a biosorbent. Hence, it can be concluded that the combined application of BAVC significantly enhances TPH removal compared to natural attenuation. While the combined application of a bioelectrochemical snorkel (BES) with BAVC also showed a significant TPH removal, it did not differ statistically from the individual application of BAVC, under applied conditions. Further research is needed to optimize BES integration with BAVC for broader applicability. This study demonstrates BAVC as a scalable and mechanistically sound approach for TPH bioremediation in soil.

Synergistic removal of total petroleum hydrocarbons and antibiotic resistance genes in Yellow River Delta wetlands contaminated soil composting regulated by biogas slurry addition

The interactive effects between the emerging contaminant antibiotic resistance genes (ARGs) and the traditional pollutant total petroleum hydrocarbons (TPHs) in contaminated soils remain unclear. The synergistic removal of TPHs and ARGs from composted contaminated soil, along with the microbial mechanisms driven by the addition of biogas slurry, have not yet been investigated. This study explored the impact of biogas slurry on the synergistic degradation mechanisms and bacterial community dynamics of ARGs and TPHs in compost derived from contaminated soil. The addition of biogas slurry resulted in a reduction of targeted ARGs and mobile genetic elements (MGEs) by 9.96%–95.70% and 13.32%–97.66%, respectively. Biogas slurry changed the succession of bacterial communities during composting, thereby reducing the transmission risk of ARGs. Pseudomonas, Cellvibrio, and Devosia were identified as core microorganisms in the synergistic degradation of ARGs and TPHs. According to the partial least squares path model, temperature and NO3− indirectly influenced the removal of ARGs and TPHs by directly regulating the abundance and composition of host microbes and MGEs. In summary, the results of this study contribute to the high-value utilization of biogas slurry and provide methodological support for the low-cost remediation of contaminated soils.

Study on the co-catalytic performance and mechanism of MoO2 in oil-contaminated wastewater treated by Fenton system

BackgroundIn the treatment of organic wastewater, Fenton technology often produces iron sludge due to iron circulation obstruction, which inhibits the treatment efficiency and causes secondary pollution to the actual water. MethodsIn this study, MoO2 was used as a cocatalyst to promote the effective cycling of Fe2+/Fe3+ in the Fe2+/H2O2 system, thus efficiently degrading total petroleum hydrocarbons (TPHs). The superiority of MoO2 as co-catalyst was verified under different reaction conditions, and its mechanism was discussed. FindingsThe degradation rate of TPHs in the Fe2+/H2O2/MoO2 system (0.069 min−1) was about 14 times that of Fe2+/H2O2 system (0.005 min−1). Compared with the Fe2+/H2O2 system, the Fe2+/H2O2/MoO2 system not only had a wider pH adaptation range, but also could effectively remove TPHs under the interference of co-existing organic and inorganic anions. MoO2 did not change the types of reactive species in Fenton system, but it enhanced the production of reactive oxygen species (ROS) by promoting the Fe2+/Fe3+ cycling in the reaction system, and ·OH was the main reactive species of TPHs degradation.

Sulfur-containing iron carbon nanocomposites activate persulfate for combined chemical oxidation and microbial remediation of petroleum-polluted soil

In this study, sulfur-containing iron carbon nanocomposites (S@Fe-CN) were synthesized by calcining iron-loaded biomass and utilized to activate persulfate (PS) for the combined chemical oxidation and microbial remediation of petroleum-polluted soil. The highest removal efficiency of total petroleum hydrocarbons (TPHs) was achieved at 0.2% of activator, 1% of PS and 1:1 soil-water ratio. The EPR and quenching experiments demonstrated that the degradation of TPHs was caused by the combination of 1O2,·OH, SO4·-, and O2·-. In the S@Fe-CN activated PS (S@Fe-CN/PS) system, the degradation of TPHs underwent two phases: chemical oxidation (days 0 to 3) and microbial degradation (days 3 to 28), with kinetic constants consistent with the pseudo-first-order kinetics of chemical and microbial remediation, respectively. In the S@Fe-CN/PS system, soil enzyme activities decreased and then increased, indicating that microbial activities were restored after chemical oxidation under the protection of the activators. The microbial community analysis showed that the S@Fe-CN/PS group affected the abundance and structure of microorganisms, with the relative abundance of TPH-degrading bacteria increased after 28 days. Moreover, S@Fe-CN/PS enhanced the microbial interactions and mitigated microbial competition, thereby improving the ability of indigenous microorganisms to degrade TPHs.

POTENTIAL OF MYCORRHIZAL INOCULATION AND CATTLE RUMEN DIGESTA IN THE BIOREMEDIATION OF SPENT ENGINE OIL CONTAMINATED SOIL

Soil pollution by crude oil contamination has become a major constraint on agricultural productivity. Physicochemical techniques are often expensive. However, bioremediation of petroleum hydrocarbon polluted soil is cost-effective. Therefore, the study was carried out to analyze the influence of mycorrhiza and cattle rumen digesta on bioremediation of Spent Engine Oil (SEO) contaminated soil in Dutse, Jigawa state. Soil samples were randomly collected from the University Research and Teaching Farm. About 2.5 kg of sterilized topsoil (0–15 cm) was filled into pots and arranged in a 2×2×3 factorial experiment in completely randomized design with three replications. Mycorrhiza and cattle rumen digesta were at two levels, while SEO was at three levels. Data were collected on the total petroleum hydrocarbon (TPH) content, bacterial and fungal colony count. Data were analyzed using ANOVA at α 0.05. Results obtained from the study show that mycorrhiza and cattle rumen digesta increased the colonies of fungi and bacteria resulting in significantly enhanced TPH degradation in the contaminated soil. However, cattle rumen digesta significantly (p&lt;0.05) enhanced TPH degradation, bacterial and fungal population the most compared to mycorrhiza alone. Combined cattle rumen digesta and mycorrhiza application resulted in significantly (p&lt;0.05) lower residual TPH content in the contaminated soil compared to using cattle rumen digesta or mycorrhiza alone. Thus, cattle rumen digesta and mycorrhiza should be used in bioremediation of petroleum hydrocarbon impacted soils.

Water conditions and arbuscular mycorrhizal symbiosis affect the phytoremediation of petroleum-contaminated soil by Phragmites australis

Phytoremediation of petroleum-contaminated soils using the synergistic functions of plants and rhizosphere microorganisms is a promising technology. However, successfully applying this approach presents challenges under certain conditions (submerged environments). This study analyzed the potential role of Phragmites australis in symbiosis with arbuscular mycorrhizal (AM) fungi during petroleum remediation at two water levels. AM inoculation promoted P. australis aboveground growth under non-flooded conditions, whereas flooding significantly increased P. australis biomass. The highest total petroleum hydrocarbon (TPH) degradation efficiency was observed in non-flooded soils, whereas submergence severely inhibited TPHs dissipation. Plants with AM inoculation treatments substantially enhanced the removal of TPHs under flooded conditions. TPH removal was positively correlated with dehydrogenase activity but negatively correlated with easily extracted glomalin-related soil proteins. Moreover, different petroleum-hydrocarbon-decaying candidates contributed to TPH removal in these two cultured soils. These findings provide valuable information for the remediation of future TPH-contaminated soils, especially applied in intermittently submerged environments.

Unraveling the functional instability of bacterial consortia in crude oil degradation via integrated co-occurrence networks.

Soil ecosystems are threatened by crude oil contamination, requiring effective microbial remediation. However, our understanding of the key microbial taxa within the community, their interactions impacting crude oil degradation, and the stability of microbial functionality in oil degradation remain limited. To better understand these key points, we enriched a crude oil-degrading bacterial consortium generation 1 (G1) from contaminated soil and conducted three successive transfer passages (G2, G3, and G4). Integrated Co-occurrence Networks method was used to analyze microbial species correlation with crude oil components across G1-G4. In this study, G1 achieved a total petroleum hydrocarbon (TPH) degradation rate of 32.29% within 10 days. Through three successive transfer passages, G2-G4 consortia were established, resulting in a gradual decrease in TPH degradation to 23.14% at the same time. Specifically, saturated hydrocarbon degradation rates ranged from 18.32% to 14.17% among G1-G4, and only G1 exhibited significant aromatic hydrocarbon degradation (15.59%). Functional annotation based on PICRUSt2 and FAPROTAX showed that functional potential of hydrocarbons degradation diminished across generations. These results demonstrated the functional instability of the bacterial consortium in crude oil degradation. The relative abundance of the Dietzia genus showed the highest positive correlation with the degradation efficiency of TPH and saturated hydrocarbons (19.48, 18.38, p < 0.05, respectively), Bacillus genus demonstrated the highest positive correlation (21.94, p < 0.05) with the efficiency of aromatic hydrocarbon degradation. The key scores of Dietzia genus decreased in successive generations. A significant positive correlation (16.56, p < 0.05) was observed between the Bacillus and Mycetocola genera exclusively in the G1 generation. The decline in crude oil degradation function during transfers was closely related to changes in the relative abundance of key genera such as Dietzia and Bacillus as well as their interactions with other genera including Mycetocola genus. Our study identified key bacterial genera involved in crude oil remediation microbiome construction, providing a theoretical basis for the next step in the construction of the oil pollution remediation microbiome.

In‐situ remediation of TPH‐polluted soil by Na2FeO4 in the Loess Plateau of China

AbstractIn recent years, the oil pollution problem on the Loess Plateau in western China is becoming increasingly serious, therefore, the use of hydroxyl radical (·OH) advanced oxidation process has increased due to its ability to efficiently degrade total petroleum hydrocarbon (TPH) in soil. However, the ability to produce ·OH of different oxidants varies widely, and the removal effect of specific pollutants has fluctuations and differences. The objective of this study is to screen the best oxidant according to the physico‐chemical properties and pollution situation of polluted soil, and to reveal the degradation mechanism of pollutants. In this study, we employed sodium ferrate (Na2FeO4) to produce ·OH for the degradation of TPHs in aged oil‐polluted soil located in the western part of the Loess Plateau in China. The results showed that the removal rates of TPH in the soil samples by hydrogen peroxide (H2O2), sodium persulfate (Na2SO4) and Na2FeO4 could reach 45.5%, 62.4%, and 65.6% respectively. The ·OH produced during the process played a major role in TPH oxidation with a contribution of more than 80%; H2O2 was intermediate substance that generated ·OH, biochar could induce the production of ·OH, the addition of biochar could activate H2O2 to promote the generation of ·OH and the removal rate is significantly increased by 19.2%. In situ remediation of polluted soil on the Loess Plateau using Na2FeO4, with a TPH degradation rate of 87.5%. The results of this study will provide a new method for the efficient degradation of TPH in loessial soil.

Synergistic effect of process parameters and nanoparticles on spent lubricant oil waste biodegradation by UV-exposed Scenedesmus vacuolatus: Process modelling, kinetics and degradation pathways

The study examines the impact of process parameters and nanoparticles (NPs) on the degradation of spent coolant waste (SCW) by UV-exposed S. vacuolatus. The model was experimentally optimized using response surface methodology (RSM) with high coefficient of determination (R2) >0.99. Upon validation of the model, total petroleum hydrocarbon (TPH) degradation of 100 % was obtained after 15 days under the optimized conditions of 25 °C temperature, 10 % (v/v) substrate concentration and 10 % (v/v) inoculum concentration. Moreover, the sensitivity of the process parameters on the degradation process assessed using artificial neural network (ANN) revealed high sensitivity of the degradation process to operational temperature. Metabolites obtained provide strong evidence for terminal oxidation and subterminal oxidation metabolic pathways in SCW degradation. In addition, the incorporation of NPs in the SCW degradation significantly enhanced the biodegradation efficiency of UV-exposed S. vacuolatus resulting in shortened degradation period from 15 to 12 days. Likewise, the inclusion of NPs substantially improved UV-exposed S. vacuolatus affinity (1/Ks) for SCW, growth constant (Kg) and maximum specific growth rate (μmax). The degradation kinetics followed the second-order reaction with degradation rate constant (K) in the range of 0.029 to 0.288 m−1 t−1 for monoaromatics and 0.972 to 4.130 m−1 t−1 for PAHs, at half-life (T1/2) ranges of 0.75 to 1.52 day−1 and 0.08 to 0.23 day−1, respectively. This knowledge will enhance the design of waste pollutant degradation towards sustainable green environment.

Potential natural attenuation of petroleum hydrocarbons in fuel contaminated soils: Focusing on anaerobic fuel biodegradation involving microbial Fe(III) reduction

Liquid fossil fuels, collectively known as total petroleum hydrocarbons (TPHs), are highly toxic and frequently leak into subsurface environments due to anthropogenic activities. As an in-situ biological remedial option for TPH contamination, aerobic TPH biodegradation is limited due to oxygen's low solubility in water, and because it is consumed quickly by aerobic bacteria. Thus, we investigated the potential of anaerobic TPH degradation by indigenous fermenting bacteria and Fe(III)-reducing bacteria. Twenty 6–10 m soil cores were collected from a closed military base subject to ongoing TPH contamination since the 1980s. Physicochemical and microbial properties were determined at 0.5-m intervals in each core. To assess the relationship between TPH degradation and microbial Fe(III) reduction, soil samples were grouped into high-TPH (>500 mg kg−1) and high-Fe(II) (>450 mg kg−1), high-TPH and low-Fe(II), low-TPH and high-Fe(II), and low-TPH and low-Fe(II) groups. Alpha diversity was significantly lower in high-TPH groups than in low-TPH groups, suggesting that high TPH concentrations exerted a strong selective pressure on bacterial communities. In the high-TPH and low-Fe(II) group, fermenting bacteria, including Microgenomatia and Chlamydiae, were more abundant, suggesting that TPH biodegradation occurred via fermentation. In the high-TPH and high-Fe(II) group, Fe(III)-reducing bacteria, including Geobacter and Zoogloea, were more abundant, suggesting that microbial Fe(III) reduction enhances TPH biodegradation. In contrast, the fermenting and/or Fe(III)-reducing bacteria were not statistically abundant in the low-TPH groups.

A comprehensive study on diesel oil bioremediation under microcosm conditions using a combined microbiological, enzymatic, mass spectrometry, and metabarcoding approach.

This study aims at the application of a marine fungal consortium (Aspergillus sclerotiorum CRM 348 and Cryptococcus laurentii CRM 707) for the bioremediation of diesel oil-contaminated soil under microcosm conditions. The impact of biostimulation (BS) and/or bioaugmentation (BA) treatments on diesel-oil biodegradation, soil quality, and the structure of the microbial community were studied. The use of the fungal consortium together with nutrients (BA/BS) resulted in a TPH (Total Petroleum Hydrocarbon) degradation 42% higher than that obtained by natural attenuation (NA) within 120days. For the same period, a 72 to 92% removal of short-chain alkanes (C12 to C19) was obtained by BA/BS, while only 3 to 65% removal was achieved by NA. BA/BS also showed high degradation efficiency of long-chain alkanes (C20 to C24) at 120 days, reaching 90 and 92% of degradation of icosane and heneicosane, respectively. In contrast, an increase in the levels of cyclosiloxanes (characterized as bacterial bioemulsifiers and biosurfactants) was observed in the soil treated by the consortium. Conversely, the NA presented a maximum of 37% of degradation of these alkane fractions. The 5-ringed PAH benzo(a)pyrene, was removed significantly better with the BA/BS treatment than with the NA (48 vs. 38 % of biodegradation, respectively). Metabarcoding analysis revealed that BA/BS caused a decrease in the soil microbial diversity with a concomitant increase in the abundance of specific microbial groups, including hydrocarbon-degrading (bacteria and fungi) and also an enhancement in soil microbial activity. Our results highlight the great potential of this consortium for soil treatment after diesel spills, as well as the relevance of the massive sequencing, enzymatic, microbiological and GC-HRMS analyses for a better understanding of diesel bioremediation.

Activation behavior of Cu0/FeS/N-graphene derived from waste soybean residue for peroxymonosulfate: Performance and mechanism

Nitrogen-enriched graphene grown on zero valent copper (Cu0) and loaded with iron sulfide (FeS) was prepared through a pyrolysis-liquid phase exfoliation process using waste soybean residue as the precursor biomass. Graphene-based catalyst (GBC) exhibits exceptional proficiency as a peroxymonosulfate activator, displaying a remarkable removal surpassing 90% of total petroleum hydrocarbons (TPHs) in 180 min. Reactive oxygen species were identified through masking experiments and electron paramagnetic resonance analysis in the Cu0/FeS/BC-900/PMS system. S(II) was the source of power for the conversion of Fe(III) to Fe(II), and it was also the reason for the continuous generation of SO4•− in the system. Density functional theory calculations revealed the active sites for adsorption and reaction. The presence of SO4•−, O2•−, and 1O2 species was attributed to the elongation of S–O and O–O bonds, as well as enhancement of electrons in sulfur and sp2 hybrid carbon atoms, respectively. The degradation of TPHs was ascribed to various radical and non-radical pathways of ROSs, with SO4•− serving as the primary oxidizing species. It was fascinating that the Cu0/FeS/BC-900/PMS system exhibited good resistance to inorganic anions and surfactants, and the treatment effect on real oilfield produced wastewater was satisfactory.

Potential of biochar for hydrocarbon degradation of crude oil-contaminated soils.

A greenhouse experiment was conducted to assess the effect of phytoremediation and biochar application on hydrocarbon degradation in crude oil-contaminated soils. The experiment consisted of four levels of biochar application (0, 5, 10, and 15 t/ha) and the presence or absence of Vigna unguiculata (cowpea; +C, -C) replicated thrice and arranged in a 4 × 2 × 3 factorial completely randomized design. Samples were taken on days 0, 30, and 60 for total petroleum hydrocarbon (TPH) analysis. A significantly higher TPH degradation efficiency of 69.2% (7033mg/kg) was observed in contaminated soils amended with 15 t/ha biochar only after 60 days of incubation. Highly significant interactions were observed between biochar × plant (p<0.001) and biochar × days (p=0.0073). Biochar also improved the growth of plants in contaminated soils, with the highest height of 23.50cm and stem girth of 2.10cm obtained when plants were amended with 15 t/ha biochar at 6weeks after planting. The potential of biochar to increase the degradation efficiency of hydrocarbons should be explored in the long run for the cleanup of crude oil-contaminated soils.

Assessment of Vinca rosea (Apocynaceae) Potentiality for Remediation of Crude Petroleum Oil Pollution of Soil

Petroleum oil pollution is a worldwide problem that results from the continuous exploration, production, and consumption of oil and its products. Petroleum hydrocarbons are produced as a result of natural or anthropogenic practices, and their common source is anthropogenic activities, which impose adverse effects on the ecosystem’s nonliving and living components including humans. Phytoremediation of petroleum hydrocarbon-polluted soils is an evolving, low-cost, and effective alternative technology to most traditional remediation methods. The objective of this study is to evaluate the phytoremediation potentiality of Vinca rosea for crude oil-contaminated soil by understanding its properties and involvement in the enhanced degradation of crude oil. The remediation potentiality was determined by evaluating the total petroleum hydrocarbon degradation percentage (TPH%) and changes in the molecular type composition of saturated and aromatic hydrocarbon fractions. TPH% was estimated gravimetrically, and changes in the molecular type composition of saturated and aromatic fractions were measured using gas chromatography and high-performance liquid chromatography, respectively. Sulfur concentration was measured using X-ray fluorescence. Cadmium and lead quantification was measured using Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES). The results revealed that V. rosea enhanced total petroleum hydrocarbon (TPH) degradation and altered the molecular composition of the crude oil. The saturated hydrocarbons increased and the aromatic hydrocarbons decreased. The saturated hydrocarbon fraction in the crude oil showed a wider spectrum of n-paraffin peaks than the oil extracted from unplanted and V. rosea-planted soils. Polyaromatic hydrocarbon degradation was enhanced in the presence of V. rosea, which was reflected in the increase of monoaromatic and diaromatic constituents. This was parallel to the increased sulfur levels in planted soil. The determination of sulfur and heavy metal content in plant organs indicated that V. rosea can extract and accumulate high amounts from polluted soils. The ability of V. rosea to degrade TPH and alter the composition of crude petroleum oil by decreasing the toxicity of polyaromatic hydrocarbons in soil, as well as its capability to absorb and accumulate sulfur and heavy metals, supports the use of plant species for the phytoremediation of crude oil-polluted sites.

Dose–effect of nitrogen regulation on the bioremediation of diesel contaminated soil

Nitrogen regulation is an effective method to enhance the bioremediation of hydrocarbon contamination. In this study, various dosages of two types of nitrogen sources were spiked to the diesel contaminated soil in a 60-day microcosmic experiment. The results showed that the total petroleum hydrocarbon (TPH) degradation rate improved from control test of 32.03% to the highest of 44.74% with nitrogen spiking. Peptone and KNO3 significantly improved the bioremediation of diesel-contaminated soil, peptone was more effective than KNO3 at low dosage. The soil C:N ratio of 20:1 (T1 treatment with the addition of peptone) was the optimal treatment. The effect of two nitrogen on soil pH was reverse, high dose of peptone addition significantly increased soil pH, but KNO3 addition significantly decreased soil pH. The soil bacteria diversity decreased significantly in the high dose Peptone treated soil, while the changes of bacteria diversity of KNO3 treated soil was just opposite. Furthermore, nitrogen regulation significantly changed the structure of soil bacterial community, Rubrobacter, Solirubrobacter and Gaiella, which belonging to Actinomycetota, were identified as the three common genus with hydrocarbon degrading ability in different nitrogen amended soil. Peptone and KNO3 had different mechanisms on the bioremediation of diesel contaminated soil. The properties of these two nitrogen sources provides us with more options for the bioremediation of hydrocarbon contaminated acid or alkaline soil.

Efficacy of bioadmendments in reducing the influence of salinity on the bioremediation of oil-contaminated soil

This study aimed to investigate the potential of three bioamendments (rice husk biochar, wheat straw biochar, and spent mushroom compost) to enhance microbial degradation of crude oil in saline soil. A soil microcosm experiment was conducted, comparing the response of soil microorganisms to crude oil under saline (1 % NaCl) and non-saline conditions. The soils were amended with different bioamendments at varying concentrations (2.5 % or 5 %), and degradation rates were monitored over a 120-day period at 20 °C. The results showed that the bioamendments significantly influenced the degradation of total petroleum hydrocarbons (TPH) in both non-saline and saline soils by 67 % and 18 % respectively. Non-saline soils exhibited approximately four times higher TPH biodegradation compared to saline soils. Among the bioamendments, rice husk biochar and spent mushroom compost had the greatest impact on biodegradation in saline soil, while wheat straw and rice husk biochar combined with spent mushroom compost showed the most significant effects in non-saline soil. The study also revealed that the bioamendments facilitated changes in the microbial community structure, particularly in the treatments with rice husk biochar and wheat straw biochar. Actinomycetes and fungi were found to be more tolerant to soil salinity, especially in the treatments with rice husk biochar and wheat straw biochar. Additionally, the production of CO2, indicating microbial activity, was highest (56 % and 60 %) in the treatments combining rice husk biochar or wheat straw biochar with spent mushroom compost in non-saline soil, while in saline soil rice husk biochar treatment (50 %) was the highest. Overall, this research demonstrates that the application of bioamendments, particularly rice husk biochar and wheat straw biochar combined with spent mushroom compost, can effectively enhance the biodegradation of crude oil in saline soil. These findings highlight the potential of such bioamendments as green and sustainable solutions for soil pollution, especially in the context of climate change-induced impacts on high-salinity soils, including coastal soils.