Research on the evolutionary control of unsafe behavior of construction personnel based on multi-field coupled-homogeneous analysis model.

Unsafe behavior among construction personnel poses significant risks in petroleum engineering construction projects. This study addresses this issue through the application of a multi-field coupled homogeneous analysis model. By conducting case analyses of petroleum engineering construction accidents and utilizing the WSR methodology, the influencing factors of unsafe behaviors among construction personnel are systematically categorized into organizational system factors, equipment management factors, and construction personnel factors. Subsequently, employing Risk coupling theory, the study delves into the analysis of these influencing factors, discussing their coupling mechanisms and classifications, and utilizing the N-K model to elucidate the coupling effect among them. Furthermore, a novel approach integrating coupling analysis and multi-agent modeling is employed to establish an evolutionary model of construction personnel's unsafe behavior. The findings reveal that a two-factor control method, concurrently reinforcing equipment and construction personnel management, significantly mitigates unsafe behavior. This study provides valuable insights into the evolution of unsafe behavior among construction personnel and offers a robust theoretical framework for targeted interventions. Significantly, it bears practical implications for guiding safety management practices within petroleum engineering construction enterprises. By effectively controlling unsafe behaviors and implementing targeted safety interventions, it contributes to fostering sustainable development within the petroleum engineering construction industry.

The potential of enhanced phytoremediation to clean up multi-contaminated soil - insights from metatranscriptomics.

This study aimed to (i) investigate the potential for enhanced phytoremediation to remove contaminants from soil historically co-contaminated with petroleum hydrocarbons (PHs) and heavy metals (HMs) and (ii) analyze the expression of crucial bacterial genes and whole metatranscriptomics profiles for better understanding of soil processes during applied treatment. Phytoremediation was performed using Zea mays and supported by the Pseudomonas qingdaonensis ZCR6 strain and a natural biofertilizer: meat and bone meal (MBM). In previous investigations, mechanisms supporting plant growth and PH degradation were described in the ZCR6 strain. Here, ZCR6 survived in the soil throughout the experiment, but the efficacy of PH removal from all soils fertilized with MBM reached 32 % regardless of the bacterial inoculation. All experimental groups contained 2 % (w/w) MBM. The toxic effect of this amendment on plants was detected 30 days after germination, irrespective of ZCR6 inoculation. Among the 17 genes tested using the qPCR method, only expression of the acdS gene, encoding 1-aminocyclopropane-1-carboxylic acid deaminase, and the CYP153 gene, encoding cytochrome P450-type alkane hydroxylase, was detected in soils. Metatranscriptomic analysis of soils indicated increased expression of methane particulated ammonia monooxygenase subunit A (pmoA-amoA) by Nitrosomonadales bacteria in all soils enriched with MBM compared to the non-fertilized control. We suggest that the addition of 2 % (w/w) MBM caused the toxic effect on plants via the rapid release of ammonia, and this led to high pmoA-amoA expression. In parallel, due to its wide substrate specificity, enhanced bacterial hydrocarbon removal in MBM-treated soils was observed. The metatranscriptomic results indicate that MBM application should be considered to improve bioremediation of soils polluted with PHs rather than phytoremediation. However, lower concentrations of MBM could be considered for phytoremediation enhancement. From a broader perspective, these results indicated the superior capability of metatranscriptomics to investigate the microbial mechanisms driving various bioremediation techniques.

The impact of ozone treatment on the removal effectiveness of various refractory compounds in wastewater from petroleum refineries.

Large volumes of wastewater are generated during petroleum refining processes. Petroleum refinery wastewater (PRW) can contain highly toxic compounds that can harm the environment. These toxic compounds can be a challenge in biological treatment technologies due to the effects of these compounds on microorganisms. These challenges can be overcome by using ozone (O3) as a standalone or as a pretreatment to the biological treatment. Ozone was used in this study to degrade the organic pollutants in the heavily contaminated PRW from a refinery in Mpumalanga province of South Africa. The objective was achieved by treating the raw PRW using ozone at different ozone treatment times (15, 30, 45, and 60 min) at a fixed ozone concentration of 3.53 mg/dm3. The ozone treatment was carried out in a 2-liter custom-designed plexiglass cylindrical reactor. Ozone was generated from an Eco-Lab-24 corona discharge ozone generator using clean, dry air from the Afrox air cylinder as feed. The chemical oxygen demand, gas chromatograph characterization, and pH analysis were performed on the pretreated and post-treated PRW samples to ascertain the impact of the ozone treatment. The ozone treatment was effective in reducing the benzene, toluene, ethylbenzene, and xylenes (BTEX) compounds in the PRW. The 60-min ozone treatment of different BTEX pollutants in the PRW resulted in the following percentage reduction: benzene 95%, toluene 77%, m + p-xylene 70%, ethylbenzene 69%, and o-xylene 65%. This study has shown the success of using ozone in reducing the toxic BTEX compounds in a heavily contaminated PRW.

Production, characterization, and application of Pseudoxanthomonas taiwanensis biosurfactant: a green chemical for microbial enhanced oil recovery (MEOR).

Biosurfactants, as microbial bioproducts, have significant potential in the field of microbial enhanced oil recovery (MEOR). Biosurfactants are microbial bioproducts with the potential to reduce the interfacial tension (IFT) between crude oil and water, thus enhancing oil recovery. This study aims to investigate the production and characterization of biosurfactants and evaluate their effectiveness in increasing oil recovery. Pseudoxanthomonas taiwanensis was cultured on SMSS medium to produce biosurfactants. Crude oil was found to be the most effective carbon source for biosurfactant production. The biosurfactants exhibited comparable activity to sodium dodecyl sulfate (SDS) at a concentration of 400 ppm in reducing IFT. It was characterized as glycolipids, showing stability in emulsions at high temperatures (up to 120 °C), pH levels ranging from 3 to 9, and NaCl concentrations up to 10% (w/v). Response surface methodology revealed the optimized conditions for the most stable biosurfactants (pH 7, temperature of 40 °C, and salinity of 2%), resulting in an EI24 value of 64.45%. Experimental evaluations included sand pack column and core flooding studies, which demonstrated additional oil recovery of 36.04% and 12.92%, respectively. These results indicate the potential application of P. taiwanensis biosurfactants as sustainable and environmentally friendly approaches to enhance oil recovery in MEOR processes.

Structure and composition of microbial communities in the water column from Southern Gulf of Mexico and detection of putative hydrocarbon-degrading microorganisms.

This study assessed the bacterioplankton community and its relationship with environmental variables, including total petroleum hydrocarbon (TPH) concentration, in the Yucatan shelf area of the Southern Gulf of Mexico. Beta diversity analyses based on 16S rRNA sequences indicated variations in the bacterioplankton community structure among sampling sites. PERMANOVA indicated that these variations could be mainly related to changes in depth (5 to 180 m), dissolved oxygen concentration (2.06 to 5.93 mg L-1), and chlorophyll-a concentration (0.184 to 7.65 mg m3). Moreover, SIMPER and one-way ANOVA analyses showed that the shifts in the relative abundances of Synechococcus and Prochlorococcus were related to changes in microbial community composition and chlorophyll-a values. Despite the low TPH content measured in the studied sites (0.01 to 0.86 µL L-1), putative hydrocarbon-degrading bacteria such as Alteromonas, Acinetobacter, Balneola, Erythrobacter, Oleibacter, Roseibacillus, and the MWH-UniP1 aquatic group were detected. The relatively high copy number of the alkB gene detected in the water column by qPCR and the enrichment of hydrocarbon-degrading bacteria obtained during lab crude oil tests exhibited the potential of bacterioplankton communities from the Yucatan shelf to respond to potential hydrocarbon impacts in this important area of the Gulf Mexico.

Characteristics of inclusions in chang 7 member and shale oil accumulation stages in Zhijing-Ansai area, Ordos Basin.

In order to further clarify the shale oil accumulation period of the Chang 7 member of the Mesozoic Triassic Yanchang Formation in the Zhijing-Ansai area of the central Ordos Basin, Using fluid inclusion petrography analysis, microscopic temperature measurement, salinity analysis and fluorescence spectrum analysis methods, combined with the burial history-thermal history recovery in the area, the oil and gas accumulation period of the Chang 7 member of the Yanchang Formation in the Zhijing-Ansai area was comprehensively analyzed. Sixteen shale oil reservoir samples of the Mesozoic Triassic Yanchang Formation in seven typical wells in the study area were selected.The results show that the fluid inclusions in the Chang 7 member of Yanchang Formation can be divided into two stages. The first stage inclusions mainly develop liquid hydrocarbon inclusions and a large number of associated brine inclusions, which are mainly beaded in fracture-filled quartz and fracture-filled calcite. The fluorescence color is blue and blue-green, and the homogenization temperature of the associated brine inclusions is between 90-110°C. The second stage inclusions are mainly gas-liquid two-phase hydrocarbon inclusions, gas inclusions and asphalt inclusions. Most of them are distributed in the fracture-filled quartz, and the temperature of the associated brine inclusions is between 120-130°C. Fluid inclusions in Chang 7 member of the Yanchang Formation can be divided into two stages. The CO2 inclusions and high temperature inclusions in the Chang 7 member of the Yanchang Formation are mainly derived from deep volcanic activity in the crust.

The refinery of the future.

Fossil fuels-coal, oil and gas-supply most of the world's energy and also form the basis of many products essential for everyday life. Their use is the largest contributor to the carbon dioxide emissions that drive global climate change, prompting joint efforts to find renewable alternatives that might enable a carbon-neutral society by as early as 2050. There are clear paths for renewable electricity to replace fossil-fuel-based energy, but the transport fuels and chemicals produced in oil refineries will still be needed. We can attempt to close the carbon cycle associated with their use by electrifying refinery processes and by changing the raw materials that go into a refinery from fossils fuels to carbon dioxide for making hydrocarbon fuels and to agricultural and municipal waste for making chemicals and polymers. We argue that, with sufficient long-term commitment and support, the science and technology for such a completely fossil-free refinery, delivering the products required after 2050 (less fuels, more chemicals), could be developed. This future refinery will require substantially larger areas and greater mineral resources than is the case at present and critically depends on the capacity to generate large amounts of renewable energy for hydrogen production and carbon dioxide capture.

Imprints of ecological processes in the taxonomic core community: an analysis of naturally replicated microbial communities enclosed in oil.

It is widely assumed that a taxonomic core community emerges among microbial communities from similar habitats because similar environments select for the same taxa bearing the same traits. Yet, a core community itself is no indicator of selection because it may also arise from dispersal and neutral drift, i.e. by chance. Here, we hypothesize that a core community produced by either selection or chance processes should be distinguishable. While dispersal and drift should produce core communities with similar relative taxon abundances, especially when the proportional core community, i.e. the sum of the relative abundances of the core taxa, is large, selection may produce variable relative abundances. We analyzed the core community of 16S rRNA gene sequences of 193 microbial communities occurring in tiny water droplets enclosed in heavy oil from the Pitch Lake, Trinidad and Tobago. These communities revealed highly variable relative abundances along with a large proportional core community (68.0 ± 19.9%). A dispersal-drift null model predicted a negative relationship of proportional core community and compositional variability along a range of dispersal probabilities and was largely inconsistent with the observed data, suggesting a major role of selection for shaping the water droplet communities in the Pitch Lake.

Simultaneous production of biosurfactant and extracellular unspecific peroxygenases by Moesziomyces aphidis XM01 enables an efficient strategy for crude oil degradation.

Crude oil is a hazardous pollutant that poses significant and lasting harm to human health and ecosystems. In this study, Moesziomyces aphidis XM01, a biosurfactant mannosylerythritol lipids (MELs)-producing yeast, was utilized for crude oil degradation. Unlike most microorganisms relying on cytochrome P450, XM01 employed two extracellular unspecific peroxygenases, MaUPO.1 and MaUPO.2, with preference for polycyclic aromatic hydrocarbons (PAHs) and n-alkanes respectively, thus facilitating efficient crude oil degradation. The MELs produced by XM01 exhibited a significant emulsification activity of 65.9% for crude oil and were consequently supplemented in an "exogenous MELs addition" strategy to boost crude oil degradation, resulting in an optimal degradation ratio of 72.3%. Furthermore, a new and simple "pre-MELs production" strategy was implemented, achieving a maximum degradation ratio of 95.9%. During this process, the synergistic up-regulation of MaUPO.1, MaUPO.1 and the key MELs synthesis genes contributed to the efficient degradation of crude oil. Additionally, the phylogenetic and geographic distribution analysis of MaUPO.1 and MaUPO.1 revealed their wide occurrence among fungi in Basidiomycota and Ascomycota, with high transcription levels across global ocean, highlighting their important role in biodegradation of crude oil. In conclusion, M. aphidis XM01 emerges as a novel yeast for efficient and eco-friendly crude oil degradation.

Synthesis and characterization of iron oxide nanoparticles from Lawsonia inermis and its effect on the biodegradation of crude oil hydrocarbon.

Crude oil hydrocarbons are considered major environmental pollutants and pose a significant threat to the environment and humans due to having severe carcinogenic and mutagenic effects. Bioremediation is one of the practical and promising technology that can be applied to treat the hydrocarbon-polluted environment. In this present study, rhamnolipid biosurfactant (BS) produced by Pseudomonas aeruginosa PP4 and green synthesized iron nanoparticles (G-FeNPs) from Lawsonia inermis was used to evaluate the biodegradation efficiency (BE) of crude oil. The surface analysis of G-FeNPs was carried out by using FESEM and HRTEM to confirm the size and shape. Further, the average size of the G-FeNPs was observed around 10 nm by HRTEM analysis. The XRD and Raman spectra strongly confirm the presence of iron nanoparticles with their respective peaks. The BE (%) of mixed degradation system-V (PP4+BS+G-FeNPs) was obtained about 82%. FTIR spectrum confirms the presence of major functional constituents (C=O, -CH3, C-O, and OH) in the residual oil content. Overall, this study illustrates that integrated nano-based bioremediation could be an efficient approach for hydrocarbon-polluted environments. This study is the first attempt to evaluate the G-FeNPs with rhamnolipid biosurfactant on the biodegradation of crude oil.

Investigating the mechanism of interfacial tension reduction through the combination of low-salinity water and bacteria.

In the enhanced oil recovery (EOR) process, interfacial tension (IFT) has become a crucial factor because of its impact on the recovery of residual oil. The use of surfactants and biosurfactants can reduce IFT and enhance oil recovery by decreasing it. Asphaltene in crude oil has the structural ability to act as a surface-active material. In microbial-enhanced oil recovery (MEOR), biosurfactant production, even in small amounts, is a significant mechanism that reduces IFT. This study aimed to investigate fluid/fluid interaction by combining low biosurfactant values and low-salinity water using NaCl, MgCl2, and CaCl2 salts at concentrations of 0, 1000, and 5000 ppm, along with Geobacillus stearothermophilus. By evaluating the IFT, this study investigated different percentages of 0, 1, and 5 wt.% of varying asphaltene with aqueous bulk containing low-salinity water and its combination with bacteria. The results indicated G. Stearothermophilus led to the formation of biosurfactants, resulting in a reduction in IFT for both acidic and basic asphaltene. Moreover, the interaction between asphaltene and G. Stearothermophilus with higher asphaltene percentages showed a decrease in IFT under both acidic and basic conditions. Additionally, the study found that the interaction between acidic asphaltene and G. stearothermophilus, in the presence of CaCl2, NaCl, and MgCl2 salts, resulted in a higher formation of biosurfactants and intrinsic surfactants at the interface of the two phases, in contrast to the interaction involving basic asphaltene. These findings emphasize the dependence of the interactions between asphaltene and G. Stearothermophilus, salt, and bacteria on the specific type and concentration of asphaltene.

Influence of heavy Canadian crude oil on pristine freshwater boreal lake ecosystems in an experimental oil spill.

The overall impact of a crude oil spill into a pristine freshwater environment in Canada is largely unknown. To evaluate the impact on the native microbial community, a large-scale in situ model experimental spill was conducted to assess the potential role of the natural community to attenuate hydrocarbons. A small volume of conventional heavy crude oil (CHV) was introduced within contained mesocosm enclosures deployed on the shoreline of a freshwater lake. The oil was left to interact with the shoreline for 72 h and then free-floating oil was recovered using common oil spill response methods (i.e. freshwater flushing and capture on oleophilic absorptive media). Residual polycyclic aromatic hydrocarbon (PAH) concentrations returned to near preoiling concentrations within 2 months, while the microbial community composition across the water, soil, and sediment matrices of the enclosed oligotrophic freshwater ecosystems did not shift significantly over this period. Metagenomic analysis revealed key polycyclic aromatic and alkane degradation mechanisms also did not change in their relative abundance over the monitoring period. These trends suggest that for small spills (<2 l of oil per 15 m2 of surface freshwater), physical oil recovery reduces polycyclic aromatic hydrocarbon concentrations to levels tolerated by the native microbial community. Additionally, the native microbial community present in the monitored pristine freshwater ecosystem possesses the appropriate hydrocarbon degradation mechanisms without prior challenge by hydrocarbon substrates. This study corroborated trends found previously (Kharey et al. 2024) toward freshwater hydrocarbon degradation in an environmentally relevant scale and conditions on the tolerance of residual hydrocarbons in situ.

UHPM dominance in driving the formation of petroleum-contaminated soil aggregate, the bacterial communities succession, and phytoremediation.

This study focused on the effects of urea humate-based porous materials (UHPM) on soil aggregates, plant physiological characteristics, and microbial diversity to explore the effects of UHPM on the phytoremediation of petroleum-contaminated soil. The compositions of soil aggregates, ryegrass (Lolium perenne) biomass, plant petroleum enrichment capacity, and bacterial communities in soils with and without UHPM were investigated. The results showed that UHPM significantly increased soil aggregate content by 0.25 mm-5 mm, resulting in higher fertilizer holding capacity, erosion resistance capacity, and plant biomass and microbial number than the soil without UHPM mixed. In addition, UHPM decreased the absorption of petroleum by plants in the soil while increasing the abundance of degrading bacteria and petroleum-degrading-related genes in the soil, thereby promoting the removal of hard-to-degrade petroleum components. RDA showed that, compared with the unimproved soil, each soil indicator was positively correlated with a high abundance of degrading bacteria in the improved soil and was significant. UHPM can be regarded as a petroleum-contaminated soil remediation agent that combines slow nutrient release with soil improvement effects.

Insights into the response of electroactive biofilm with petroleum hydrocarbons degradation ability to quorum sensing signals.

Bioelectrochemical technologies based on electroactive biofilms (EAB) are promising for petroleum hydrocarbons (PHs) remediation as anode can serve as inexhaustible electron acceptor. However, the toxicity of PHs might inhibit the formation and function of EABs. Quorum sensing (QS) is ideal for boosting the performance of EABs, but its potential effects on reshaping microbial composition of EABs in treating PHs are poorly understood. Herein, two AHL signals, C4-HSL and C12-HSL, were employed to promote EABs for PHs degradation. The start-times of AHL-mediated EABs decreased by 18-26%, and maximum current densities increased by 28-63%. Meanwhile, the removal of total PHs increased to over 90%. AHLs facilitate thicker and more compact biofilm as well as higher viability. AHLs enhanced the electroactivity and direct electron transfer capability. The total abundance of PH-degrading bacteria increased from 52.05% to 75.33% and 72.02%, and the proportion of electroactive bacteria increased from 26.14% to 62.72% and 63.30% for MFC-C4 and MFC-C12. Microbial networks became more complex, aggregated, and stable with addition of AHLs. Furthermore, AHL-stimulated EABs showed higher abundance of genes related to PHs degradation. This work advanced our understanding of AHL-mediated QS in maintaining the stable function of microbial communities in the biodegradation process of petroleum hydrocarbons.

Biodegradation of aliphatic and aromatic hydrocarbons by bacteria isolated from Bahregan area.

Environmental pollution with aromatic and aliphatic hydrocarbons caused by oil and petrochemical industries has very toxic and carcinogenic effects on living organisms and should be removed from the environment. In this research, after analyzing the oil sludge of the Bahregan area, it was found that most aliphatic paraffin compounds are related to octadecane, most liquid aliphatic compounds are related to hexadecane, and most aromatic compounds are related to naphthalene, phenanthrene, fluoranthene, and anthracene. Then, we investigated the ability of native bacteria from this area, such as Thalassospira, Chromohalobacter, and a bacterial consortium, to biodegrade the dominant aromatic and aliphatic hydrocarbons found in oil sludge. The results of Gas Chromatography-Mass Spectrometry analysis showed that among the tested hydrocarbon sources, Thalassospira can completely remove octadecane and hexadecane, and Chromohalobacter can reduce hexadecane from 15.9 to 9.9%. The bacterial consortium can completely remove octadecane and reduce hexadecane from 15.9 to 5.1%, toluene from 25.6 to 0.6%, and phenanthrene from 12.93 to 6%. According to the obtained results, the bacterial consortium effectively plays a role in the biodegradation of aromatic and aliphatic hydrocarbons, making it a viable solution for treating hydrocarbon pollutants in various environments.

Genome-wide DNA methylation changes in Oryzias melastigma embryos exposed to the water accommodated fraction of crude oil.

The water accommodated fraction (WAF) of crude oil exerts considerable impacts on marine fish during embryonic stage. Clarifying changes in epigenetic modifications is helpful for understanding the molecular mechanism underlying the toxicity of embryonic WAF exposure. The aim of this study was to explore genome-wide DNA methylation changes in Oryzias melastigma embryos after exposure to the nominal total petroleum hydrocarbon concentration of 500 µg/L in WAF for 7 days. Whole-genome bisulfite sequencing revealed that 8.47 % and 8.46 % of all the genomic C sites were methylated in the control and WAF-exposed groups, respectively. Among the three sequence contexts, methylated CG site had the largest number in both the two groups. The sequence preferences of nearby methylated cytosines were consistent between the two groups. A total of 4798 differentially methylated regions (DMRs) were identified in the promoter region. Furthermore, Gene Ontology analysis revealed that DMR-related genes were enriched mainly for functions related to development and nervous system. Additionally, the Kyoto Encyclopedia of Genes and Genomes pathways enriched in DMR-related genes were related to nervous system and endocrine system. These novel findings provide comprehensive insights into the genome-wide DNA methylation landscape of O. melastigma following embryonic WAF exposure, shedding light on the epigenetic regulatory mechanisms underlying WAF-induced toxicity.

Diversity links to functionality: Unraveling the impact of pressure disruption and culture medium on crude oil-enriched microbial communities from the deep Eastern Mediterranean Sea.

Mesopelagic water from the deep Eastern Mediterranean Sea (EMS) was collected under disrupted (REPRESS) or undisturbed (HP) pressure conditions and was acclimated to oil (OIL) or dispersed-oil (DISPOIL) under in situ pressure and temperature (10 MPa, 14 °C). Decompression resulted in oil-acclimatised microbial communities of lower diversity despite the restoration of in situ pressure conditions during the 1-week incubation. Further biodiversity loss was observed when oil-acclimatised communities were transferred to ONR7 medium to facilitate the isolation of oil-degrading bacteria. Microbial diversity loss impacted the degradation of recalcitrant oil compounds, especially PAHs, as low-abundance taxa, linked with PAH degradation, were outcompeted in the enrichment process. Thalassomonas, Pseudoalteromonas, Halomonas and Alcanivorax were enriched in ONR7 under all experimental conditions. No effect of dispersant application on the microbial community structure was identified. A. venustensis was isolated under all tested conditions suggesting a potential key role of this species in hydrocarbons removal in the deep EMS.

Binary mixture of ionic liquid and span 80 for oil spill remediation: Synthesis and performance evaluation.

The synthesis of new surfactants helps to mitigate the environmental and financial effects of oil spills by providing efficient cleanup options. Herein, this study provides the development of a binary mixture of Span 80 and Choline myristate [Cho][Mys], a surface-active ionic liquid (SAIL) as green dispersant for oil spill remediation. The synergistic interaction at a 60:40 (w/w) ratio significantly lowered the critical micelle concentration (cmc) to 0.029 mM. Dispersion efficiency tests with Arab crude oil showed optimal performance at a 60:40 ratio of Span 80 and [Cho][Mys] (1:25 dispersant to oil ratio, v/v), achieving 81.16 % dispersion effectiveness in the baffled flask test. The binary mixture demonstrated superior emulsion stability (6 h) and the lowest interfacial tension (1.12 mN/m). Acute toxicity experiments revealed the dispersant's practical non-toxicity with an LC50 value of 600 mg/L. Overall, this environmentally benign surfactant combination shows promise as a safe and effective oil spill dispersant.

Development of a green and low-cost method to determine mercury content in sediments affected by oil spill on the Brazilian coast.

Tons of crude oil were found on the Brazilian coast in 2019, and studies assessing its chemical composition are still scarce. This study aimed to develop a new and simple technique of cold vapor generation using infrared irradiation coupled with atomic absorption spectrometry to determine mercury content in sediments contaminated by crude oil. Experimental conditions were evaluated, including formic acid concentration, reactor temperature, and carrier gas flow rate. The accuracy of the method was validated by comparison with mercury contents in a certified reference material (PACS-2). The detection limit was found to be 0.44 µg kg-1. The developed method was applied to determine the total mercury content in marine sediment samples collected from beaches in Ceará State. Mercury concentrations ranged from 0.41 to 0.95 mg kg-1. The proposed method is efficient, simple, low-cost, and adequate for its purpose.

Low dose phosphorus supplementation is conducive to remediation of heavily petroleum-contaminated soil-From the perspective of hydrocarbon removal and ecotoxicity risk control.

Biostimulation by supplementing of nitrogen and phosphorus nutrients is a common strategy for remediation of petroleum-polluted soils. However, the dosage influence of exogenous nitrogen or phosphorus on petroleum hydrocarbon removal and soil ecotoxicity and microbial function remain unclear. In this study, we compared the efficiencies of hydrocarbon degradation and ecotoxicity control by experiment conducted over addition of inorganic nitrogen or phosphorus at C/N ratio of 100/10, C/N/P ratio of 100/10/1, and C/P ratio of 100/1 in a heavily petroleum-contaminated loessal soil with 12,320 mg/kg of total petroleum hydrocarbon (TPH) content. A 90-day incubation study revealed that low-dose of phosphorus addition with the C/P ratio of 100/1 promoted hydrocarbon degradation and reduced soil ecotoxicity. Microbial community composition analysis suggested that phosphorus addition enriched hydrocarbon degrader Gordonia and Mycolicibacterium genus. The key enzymes EC 5.3.3.8, EC 6.2.1.20 and EC 6.4.1.1 which referred to degradation of long-chain hydrocarbons, unsaturated fatty acids and pyruvate metabolism were abundance by phosphorus supplementation. While nitrogen addition at C/N ratio of 100/10 or C/N/P ratio of 100/10/1 inhibited hydrocarbon degradation and exacerbated soil ecotoxicity due to promoting denitrification and coupling reactions with hydrocarbons. Our results suggested that low-dose phosphorus addition served as a favorable strategy to promote crude oil remediation and ecotoxicity risk control in heavily petroleum-contaminated soil. Hence, the application of suitable doses of exogenous biostimulants is an efficient approach to restore the ecological functions of organically contaminated soils.