Total Petroleum Hydrocarbons Levels Research Articles

Assessing petroleum contamination in parts of the Niger Delta based on a sub-catchment delineated field assessment.

The Niger Delta in Nigeria is a complex and heavily contaminated area with over 150,000 interconnected contaminated sites. This intricate issue is compounded by the region's strong hydrological processes and high-energy environment, necessitating a science-based approach for effective contamination assessment and management. This study introduces the concept of sub-catchment contamination assessment and management, providing an overarching perspective rather than addressing each site individually. A description of the sub-catchment delineation process using the digital elevation model data from an impacted area within the Delta is provided. Additionally, the contamination status from the delineated sub-catchment is reported. Sediment, surface water and groundwater samples from the sub-catchment were analyzed for total petroleum hydrocarbons (TPH) and polycyclic aromatic hydrocarbons (PAHs), respectively. Surface sediment TPH concentrations ranged from 129 to 20,600mg/kg, with subsurface (2-m depth) concentrations from 15.5 to 729mg/kg. PAHs in surface and subsurface sediment reached 9.55mg/kg and 0.46mg/kg, respectively. Surface water exhibited TPH concentrations from 10 to 620mg/L, while PAHs ranged from below detection limits to 1mg/L. Groundwater TPH concentrations spanned 3 to 473mg/L, with total PAHs varying from below detection limits to 0.28mg/L. These elevated TPH and PAH levels indicate extensive petroleum contamination in the investigated sediment and water environment. Along with severe impacts on large areas of mangroves and wetlands, comparison of TPH and PAH concentrations with sediment and water quality criteria found 54 to 100% of stations demonstrated exceedances, suggesting adverse biological effects on aquatic and sediment biota are likely occurring.

Enhancing in situ remediation of clayey soils contaminated with total petroleum hydrocarbons by combining pneumatic fracturing, plasma blasting, and vacuum extraction: A comprehensive field investigation

Oxidant injection technology is widely used in soil remediation; however, subsurface conditions, including soil properties and permeability, significantly influence its effectiveness. In this study, the potential of the combination of pneumatic fracturing, plasma discharge, and vacuum extraction (PPV) in enhancing soil permeability and remediating field-scale silt/clayey soils contaminated by total petroleum hydrocarbon (TPH) was studied. Improved soil permeability was assessed by measuring the chlorine and H2O2 concentrations in soil samples, and the remediation efficiency of PPV was evaluated by analyzing the TPH concentrations in the soil samples. The initial highest TPH concentration was 6,922mgkg-1; after a 42-day operation period, the TPH levels decreased to 541mgkg-1. The economic assessment of PPV revealed it to be cost-effective, with a total operating cost of US$ 3,077 for remediating 265m³ of contaminated soil, equating to US$ 11.6 per ton of soil. Since PPV requires a short operational period, is inexpensive, and is suitable for purifying low-permeability soil, it is a promising and economically advantageous approach for soil purification. Overall, PPV demonstrated the ability to enhance oxidizing agent transfer by increasing soil permeability, suggesting its potential for efficient and targeted soil remediation.

Biostimulation potentials of spent milled maize and cowblood on a crude oil polluted soil

This study was carried out to investigate the biostimulation effect of the application of spent milled maize and cow blood to crude oil polluted soil. The treatment groups were; Control (0 L crude oil (CO) + 0 kg spent milled maize (SMM)), group 1 (1 L CO + 1 kg SMM + 1 L cow blood), group 2 (2 L CO + 2 kg SMM) and group 3 (5 L CO + 5 kg SMM). The experiment was laid out in a completely randomized design A total of four treatment combinations were applied and replicated 3 times giving a total of 48 plots.The physicochemical properties and bacterial load of the soil were determined before pollution, two weeks after pollution, four weeks and eight weeks after remediation. The results for physicochemical properties of soil indicates a decrease in total organic carbon and nitrogen while there was an increase in the levels of cation exchange capacity, phosphorus and electrical conductivity after crude oil pollution. The mean levels of total petroleum hydrocarbon and polycyclic aromatic hydrocarbon reduced after the pollution. The application of the spent milled maize and cow bloodwere observed to improve the physicochemical properties of soil. There was also an increased bacterial count for the treated groups compared to the control; the values ranged from 1.3 x 103cfu/g to 1.24 x 108cfu/g. The identified bacteria were Flavobacterium, Pseudomonas, Bacillus, Micrococcus, Proteus, Clostridium and Nocardia species.Generally, this study has revealed that spent milled maize and cow blood are effective in the restoration of crude oil polluted soil.

Residual hydrocarbons in long-term contaminated soils: implications to risk-based management

Petroleum hydrocarbon (PHC) contamination is a widespread and severe environmental issue affecting many countries’ resource sectors. PHCs are mixtures of hydrocarbon compounds with varying molar masses that naturally attenuate at different rates. Lighter fractions attenuate first, followed by medium-molar-mass constituents, while larger molecules remain for longer periods. This results in significant regulatory challenges concerning residual hydrocarbons in long-term contaminated soils. This study examined the potential risks associated with residual PHC and its implications for risk-based management of heavily contaminated soils (23,000–26,000 mg PHC/kg). Ecotoxicological properties, such as seedling emergence and growth of two native plant species—small Flinders grass (Iseilema membranaceum) and ruby saltbush (Enchylaena tomentosa)—and earthworm survival tests in PHC-contaminated soils, were assessed. Additionally, the effects of aging on the attenuation of PHC in contaminated soils were evaluated. Toxicity responses of plant growth parameters were determined as no-observed-effect concentrations: 75%–100% for seedling emergence, < 25%–75% for plant shoot height, and 75%–100% for earthworm survival. After 42 weeks of aging, the total PHC levels in weathered soils decreased by 14% to 30% and by 67% in diesel-spiked soil due to natural attenuation. Dehydrogenase enzyme activity in soils increased during the initial aging period. Furthermore, a clear shift of bacterial communities was observed in the soils following aging, including enrichment of PHC-resistant and -utilizing bacteria—for example, Nocardia sp. This study underscores the potential of natural attenuation for eco-friendly and cost-effective soil management, underlining that its success depends on site-specific factors like water content and nutrient availability. Therefore, we recommend detailed soil assessments to evaluate these conditions prior to adopting a risk-based management approach.

Seasonal Population Trends of Microbial Communities in Oil Tainted Soils in Greater Port Harcourt Area, Nigeria

The utilization of oil in industries has devastating effect to the environment. Industrial effluents and oil spills are continuously contaminating the soil. Further, seasonality influences the distribution of pollutants in soil. Consequently, soil microbial biota and ecological processes are affected. This study assessed the effect of seasonality on soil fungal and bacterial communities in oil contaminated soils in 12 selected sites in Greater Port Harcourt Area. Standard analytical procedures were used to obtain bio-physicochemical data from the soil samples and t test was used to analyse data. The levels of total petroleum hydrocarbons (TPH) were above 5000 ppm (DPR recommended limit). There was significant difference (p ≤ 0.000) between the means of TPH in wet and dry seasons. Seasonality influenced % HUF and % HUB in the soils of urban, industrial and agricultural sites. Generally, the seasonality trends showed that there was a declining population of THB, HUB, TF, and HUF from the wet season to the dry season. However, the results show that there was a stable trend in % HUB as compared to oscillations observed in % HUF in oil tainted soils across a seasonal divide. We recommend characterization of the microorganism to identify the best candidate for bioremediation of oil tainted soils across a seasonal divide.

Assessing the Presence of Petroleum Hydrocarbons in the Punta Carnero Estuary (Ecuador)

Chronic hydrocarbon spills are a threat to coastal ecosystems, and their impact on the water quality along watercourses should be characterised to medium long term in order to assess the risk and define cost-effective and sustainable remediation strategies. For this purpose, a methodology for the measurement of total petroleum hydrocarbons (TPH) on a spatio-temporal scale was designed, implemented and validated in the Punta Carnero estuary, in the Santa Elena province, western Ecuador, which is affected by hydrocarbon pollution. The selection of monitoring stations was made according to the different inflows along the water system corresponding to the different anthropogenic activities in the area, in order to assess whether the effluents involve critical levels of pollution. Measurements of hydrodynamic, environmental and vegetation cover parameters were also carried out to assess their possible variations as a consequence of the impact of the spatio-temporal TPH concentrations. An increase in hydrocarbon concentrations was observed from 2013 to 2021. Mean annual TPH levels were above the maximum allowable limit for the protection of aquatic and other wildlife in estuarine waters according to the Ecuadorian regulation for environmental quality. An increase in mangrove tree cover could contribute to an exponential decrease in contamination levels. The methodology used in this study may support the quantifying of TPH content in future applications, which is a priority task for the restoration of degraded ecosystems.Graphical abstract

Performance evaluation of electrokinetic bioremediation for weathered petroleum hydrocarbon-contaminated soil

This study investigates the impact of Electrokinetic Remediation (EKR) time on total petroleum hydrocarbons (TPH) removal from soil, focusing on electroosmotic phenomena guided by Helmholtz-Smoluchowski theory. Soil samples were exposed to a constant 2 V/cm voltage gradient for 8, 16, and 24 hours, utilizing a 0.05 M Na2SO4 solution as an electrolyte to enhance soil conductivity. Biostimulation was combined with EKR, and TPH levels and microbial colonies (TPC) were monitored over a 4-week period. Maintaining optimal conditions (25-40°C, pH 6-8, 30-60% water content) was crucial for effective biodegradation. Results showed that a 24-hour EKR duration was most effective, achieving an 87.9% removal rate. The 16-hour duration closely followed at 85.7%, while the 8-hour duration exhibited lower effectiveness at 62.5%. TPC counts increased in the fourth week for the 16-hour and 24-hour durations but decreased for the 8-hour duration. Post-EKR, a gradual decline in TPH levels indicated electroosmotic flow’s (EOF) positive impact on TPH desorption and biodegradation. Electroosmosis influence was evident in varying TPH concentrations among segments after EKR, with higher levels near the cathode in the 16-hour and 24-hour durations. Lower TPH near the cathode in the 8-hour variation suggested electroosmosis-induced desorption, while reduced concentrations in regions A (near anode) and B (middle) resulted from biodegradation and microbial mobility due to electrophoresis. Confirmation of electroosmosis across all durations was supported by observed water content and EOF volume. The 24-hour duration exhibited the highest EOF proportion in the cathode chamber at 22.2%, followed by 16 hours at 16.1%, and 8 hours at 8.6%.

DETERMINATION OF HEAVY METALS AND TOTAL PETROLEUM HYDROCARBONS IN SOIL SAMPLES AND PLANT LEAVES AROUND OIL REFINERIES LOCATED ON ERBIL-GWER ROAD

Several refinery complexes exist in the Kurdistan Region of Iraq that produce various kinds of petroleum products. During the refining process, different types of gases, metals, hydrocarbons, and liquids are discharged into the environment. This study aimed to determine the concentration of eight heavy metals in soil and plant leaves collected around the refineries along Erbil-Gwer Road on two occasions throughout the study period. Additionally, we aimed to evaluate the levels of Total Petroleum Hydrocarbons (TPH) in the soil samples from the area. The results of the analysis revealed significant differences (P&lt;0.05) in the concentrations of Pb, Ni, Cd, Cr, As, and Mn between the dry and wet seasons in the soil samples. However, no significant differences were observed for Cu and Zn between the two seasons. The levels of metals for both periods were as follows: Mn&gt; Cr&gt; Zn&gt; Ni&gt; Cu&gt; Pb&gt; As&gt; Cd in successive forms. Regarding the plant leaves, significant differences (P&lt;0.05) were found between the study periods for Pb, Cu, Zn, and Cd, whereas no significant differences were observed for the other metals. Furthermore, the concentration of TPH in the soil samples located alongside the refinery effluent stream was higher compared to the other areas.

Spatial distribution of total petroleum hydrocarbons in the seawater and sediment of Southeast coast of India.

The spatial distribution of total petroleum hydrocarbons (TPH) were analysed in the seawater and sediment samples collected from 27 locations along the Southeast coast of India. A first-time assessment was carried out on the distribution of TPH in both water and sediments for the entire coastline of Tamil Nadu. The concentration of TPH in seawater showed large spatial variation ranging from below detection level (BDL) to 47.5μg/L and 0.01 to 53.12μg/L in the surface and bottom waters, respectively. TPH levels exceeded the regulatory limits specified by FAO, China's Marine Monitoring Standards and the European Community in the seawater samples of Thoothukudi harbour (S2 station). The results showed that seawaters of southern stations were comparatively more polluted with TPH. TPH values in sediment were between 2.33 and 30.07μg/g, and their levels remained below the Marine Sediment Quality Standard (500μg/g). The spatial profile of TPH in sediments were contrasting to that observed for seawater. Higher TPH values were observed in sediments of the northern region than southern. TPH contents are strongly correlated with clay (R2 = 0.776; P < 0.001) and silt (R2 = 0.648; P < 0.001); conversely, there is a significant negative correlation between TPH and sand (R2 = 0.753; P < 0.001). ANOVA analysis demonstrated a significant difference (F = 11.75; p < 0.01) between the TPH concentrations of water and sediments. Non-metric multidimensional scaling (nMDS) was performed to determine the similarity among sampling stations that formed five crusted groups. Sediment along the southeast coast can be categorised as slightly polluted with respect to TPH as per the ATSDR standards.

Electron beam remediation of soils impacted with heavy hydrocarbons

During electron beam (EBeam) irradiation, high-energy electrons can generate physical and chemical changes in a substance such as chain scission and cross-linking. Irradiation of soil is shown to be an effective technology for rapid reduction of Total Petroleum Hydrocarbons (TPH) in crude oil impacted soils. An experimental apparatus for batch treatment of 100 g soil samples was built and tested using a 10 MeV, 15 kW electron beam. The samples were a variety of crude oil impacted soil samples with TPH contents ranging between 1.6 and 32% by mass. Soils of initial TPH up to 9.1% (dry weight basis) TPH levels were reduced to below a target cleanup level of 1% with irradiation doses ranging from 700 kJ/kg to 1100 kJ/kg and treatment times less than 200 s, with maximum soil temperatures less than 450 °C. Soils with elevated moisture content required higher dosages or preliminary drying. EBeam treatments resulted in 1) reduction for both light and heavy hydrocarbon, 2) generation of new light hydrocarbons, and 3) generation of fixed carbon, indicating that the mechanisms of electron beam remediation include radical induced reactions at relatively low temperature and relatively short time scales and not simply thermal desorption effects.

Total petroleum hydrocarbon analysis in water, tilapia and sediment samples from ARAC environment (Aluu), Rivers State

The contamination of aquatic environments by Total Petroleum Hydrocarbons (TPHs) presents significant environmental and health concerns. This study aimed to assess the levels of TPHs in water, tilapia, and sediment samples collected from the African Regional Aquaculture Center in Aluu, Nigeria. Chromatographic techniques were employed for TPH extraction and detection. The results revealed elevated TPH concentrations in the study area, with the highest levels observed in sediment samples. The results revealed that the concentration of TPH was high during the dry season (September to November) compared to raining season (May to July). Also, the results indicated that TPH concentration was higher in sediment compared to fish and water with average concentration of 0.206667mg/kg, 0.17666mg/kg7, and 0.148333mg/kg in sediment, fish and water respectively. TPHs was observed to be in sediment from 0.18 – 0.25mg/kg, whereas in water it had variation of 0.11mg/kg making it the lowest. TPHs variation in fish was also observed to be between 0.15 – 0.22mg/kg. It was observed that the concentrations of TPHs in fish positively correlated with THPs in the aquatic water (y = 12.56x + 168.32). This correlation is statically significant (p &lt;0.5). The results also revealed that concentration of TPH in sediments was positively correlated (y = 2.83 x 154.26) with the water at p&lt; 0.5 significant level. There was a positive correlation between TPH concentrations in fish and water, as well as between TPH concentrations in sediment and water. The findings emphasized the need for prompt intervention to mitigate TPH pollution and protect the environment and human health.

Rapid Determination of the Total Petroleum Hydrocarbon Content of Soils by Handheld Fourier Transform Near-Infrared Spectroscopy.

For successful soil remediation and hydrocarbon exploration operations, determining the total petroleum hydrocarbon (TPH) content of soils is an indispensable process step. This paper reports on the performance of a handheld Fourier transform near-infrared (FT-NIR) spectrometer for rapid and quantitative determination of TPH content of soils from two different sites by diffuse reflection measurements. For rapid decisions for exploration work or environmental site assessment projects, a quick─preferably on-site─determination of TPH content is valuable. Diffuse reflection NIR spectra were recorded from soil samples of two different sites with TPH reference values ranging from 350 to 30,000 ppm, as determined by capillary gas chromatography and flame ionization detection with hydrocarbon fingerprinting C1-C44. However, this paper not only addresses the development of site-specific partial-least squares (PLS) calibrations but also demonstrates the locally-weighted PLS (LW-PLS) technique, which can be used to develop global, site-independent PLS calibrations without significant penalty in calibration performance. As a first step, the diffuse reflection spectra were used to develop conservative, site-specific PLS calibration models with root-mean-square calibration/cross-validation errors (RMSEC/RMSECV) of 1043/1106 and 741/785 ppm TPH, respectively, and the average absolute prediction errors for samples not contained in the calibration set were 451 and 293 ppm for the two sites, respectively. In a further step, significant degradation of the RMSE values of a conservative PLS model based on the NIR spectra of both sites was then compared to the application of the LW-PLS method, with only a slight loss of the prediction accuracy relative to the site-independent models. This study confirms the ability of next-generation portable FT-NIR spectrometers to predict low TPH levels in various soil types through both─soil-specific and site-independent─calibrations, giving these spectrometers the potential to become rapid screening tools in the field.

Spatial distribution and driving factors of groundwater chemistry and pollution in an oil production region in the Northwest China

Concerns have been raised on the deterioration of groundwater quality associated with anthropogenic impacts such as oil extraction and overuse of fertilizers. However, it is still difficult to identify groundwater chemistry/pollution and driving forces in regional scale since both natural and anthropogenic factors are spatially complex. This study, combining self-organizing map (SOM, combined with K-means algorithm) and principal component analysis (PCA), attempted to characterize the spatial variability and driving factors of shallow groundwater hydrochemistry in Yan'an area of Northwest China where diverse land use types (e.g., various oil production sites and agriculture lands) coexist. Based on the major and trace elements (e.g., Ba, Sr, Br, Li) and total petroleum hydrocarbons (TPH), groundwater samples were classified into four clusters with obvious geographical and hydrochemical characteristics by using SOM - K-means clustering: heavily oil-contaminated groundwater (Cluster 1), slightly oil-contaminated groundwater (Cluster 2), least-polluted groundwater (Cluster 3) and NO3− contaminated groundwater (Cluster 4). Noteworthily, Cluster 1, located in a river valley with long-term oil exploitation, had the highest levels of TPH and potentially toxic elements (Ba, Sr). Multivariate analysis combined with ion ratios analysis were used to determine the causes of these clusters. The results revealed that the hydrochemical compositions in Cluster 1 were mainly caused by the oil-related produced water intrusion into the upper aquifer. The elevated NO3− concentrations in Cluster 4 were induced by agricultural activities. Water-rock interactions (e.g., carbonate as well as silicate dissolution and precipitation) also shaped the chemical constituents of groundwater in clusters 2, 3, and 4. In addition, SO42−-related processes (redox, precipitation of sulfate minerals) also affected groundwater chemical compositions in Cluster 1. This work provides the insight into the driving factors of groundwater chemistry and pollution which could contribute to groundwater sustainable management and protection in this area and other oil extraction areas.

Efficacy of E-Safe Product in Decontamination of Hydrocarbon Contaminated Soil

Effectiveness of E-safe© product in the recovery of soil contaminated with total petroleum hydrocarbon (TPH) was investigated at the Teaching and Research Laboratory of the Department of Microbiology, Hezekiah University, Umudi, Imo State. The study was conducted on soil sample collected from aged crude oil polluted site in Rivers State.The top soil (0-30cm) was sieved using a 5mm mesh to remove gravel and debris prior to analysis. The pH, Phosphate, Nitrate, and TPH levels in the soil were analyzed using well established standard analytical protocols. E-safe product was artificially spiked in each of the 4kg soil at 0 ml, 6 ml, 12 ml, 24 ml, and 48 ml and arranged in a Completely Randomized Design. The percentage degradation of TPH in soil was monitored for a period of four (4) weeks. Results obtained showed that the soil pH was slightly acidic to basic. The findings showed Nitrate (4.97 – 24.42 ppm) and phosphate (0.134 – 0.53 ppm) ranges for both treated and control soils within the period. About 88.41% TPH degradation was achieved at 48 ml followed by 24 ml (75.63%) while the least percentage removal of TPH was recorded in the control (2.30%). The study further showed that soils contaminated with petroleum hydrocarbon altered soil physicochemistry, but more than 50% of the polluted soils were recovered by treatment with E-safe product at 48 ml, 24 ml and 12 ml respectively. The mineral components of the E-safe product could have acted as effective substance in the total removal of oil contaminants in the contaminated soil.

Evaluating the Spatial Distribution of Some Toxic Substances Concentration with the Microbial Contamination of Wetland Water, Sediment and Fishes, and Their Potential Health Hazards

This study evaluated the impact of anthropogenic factors on the accumulation of toxic materials in wetland. The wetland was micro-zoned into five sub-regions, namely; NDE, ISN, ISS, UGS and BUR. Sediment, water and fishes (catfish and tilapia) were sampled from each locality. Heavy metals (Cd, Cr, Cu, Ni, Fe, Pb and Zn) and total petroleum hydrocarbon (TPH) of the samples were determined. The pollution indices (Bioaccumulation quotient “BQ”, contamination factor “CF”, geoaccumulation index “Igeo”, enrichment factor “EF” and Pollution load index “PLI”) and potential health risks (Metal Pollution Index “MPL”, Estimated Daily Intake “EDI”, Total Health hazard quotient “THQ” and Hazard index “HI”) of the water, sediment and fish flesh were calculated appropriately. The results revealed that the wetland fishes contained viable bacteria which ranged between 1362.0 cfu/g and 2634.3 cfu/g. Heavy metal level ranking in the sediment and water was Fe &gt; Zn &gt; Cu &gt; Pb &gt; Ni &gt; Cr &gt; Cd. Spatially, the heavy metals concentration in the water, sediment and fish followed the order: BUR &gt; UGS &gt; ISN &gt; ISS &gt; NDE. The TPH concentration in water, sediment and fishes differed significantly across the five sub-regions (p≤ 0.05), and its value ranged from 3.44 mg/kg to 99.38 mg/kg for the catfish, 2.08 mg/kg to 83.73 mg/kg for the tilapia, 25.34 mg/kg to 718.87 mg/kg for the sediment and 0.016 mg/kg to 1.099 mg/kg for the water. Spatial ranking of the TPH levels in the fish flesh was BUR &gt; UGS &gt; ISN &gt; NDE &gt; ISS; sediment TPH level ranked BUR &gt; UGS &gt; NDE &gt; ISN &gt; ISS; and the water TPH level ranked BUR &gt; UGS &gt; ISN &gt; ISS &gt; NDE. Human health risks associated with the consumption of the wetland fish ranked thus BUR &gt; UGS &gt; ISN &gt; NDE &gt; ISS. It was evident from the results that anthropogenic actions from resulting poor regional planning had significant effect on environmental health. The results called for environmental protection for public interest in order to prevent disease epidemics.

Impact of Artisanal Crude Oil Refinery on Physicochemical and Microbiological Properties of Soil and Water in Igia-Ama, Tombia Kingdom, Rivers State, Nigeria

This study aimed to determine the impact of artisanal refinery operations on the physicochemical and microbiological properties of soil and water in Igia-Ama, Tombia Kingdom, Rivers State, Nigeria. Physicochemical parameters along with concentrations of heavy metals, polyaromatic hydrocarbons (PAHs), total petroleum hydrocarbon (TPH), benzene, toluene, ethylbenzene and xylene (BTEX), and polychlorinated biphenyls (PCB) were determined in soil and water samples using standard methods. Microbial populations were determined using standard plate count. Microbial isolates were identified based on their cultural, morphological and biochemical characteristics. Results show that concentrations of monitored physicochemical parameters differed significantly (p&lt;0.05) between impacted sites and control as well as between dry and wet season. Heavy metals, PAHs, TPH, BTEX and PCB concentrations were higher in the impacted sites than in the control (significant, p&lt;0.05), and also differed significantly between dry and wet season. Microbial counts varied between polluted samples and control as well as between dry and wet season, though not significantly different (p&gt;0.05). Bacterial isolates in polluted soil samples were identified as Enterobacter sp., Bacillus sp., Micrococcus sp., Staphylococcus sp. and Pseudomonas sp. Bacteria in polluted water samples were identified as Staphylococcus sp. and Escherichia coli. Fungi in polluted soil samples were identified as Aspergillus sp., Penicillium sp. Fusarium sp., Rhodotorula sp., Exophiala sp. and Crypotococcus sp. While only Penicillium sp. was isolated in polluted water sample. Artisanal crude oil refinery operations significantly impacted the physicochemical properties of soil and water in the study area but not the microbiological properties. The levels of heavy metals, PAHs, TPH and BTEX in the soil and water suggest the need for remediation of the impacted environment.

Ecological risk assessment of heavy metal pollutants and total petroleum hydrocarbons in sediments of the Bohai Sea, China.

Heavy metals and organic pollutants like total petroleum hydrocarbons (TPHs) in coastal marine sediments are receiving extensive attention, as they may pose a serious threat to the aquatic environment and ecosystem health. To date, however, data on the long-term variations in the levels of sedimentary heavy metals and TPHs as well as their ecological risks are relatively limited. Here, we conducted 12 cruises spanning 3years in the Bohai Sea and obtained ~1400 sediment samples to explore the long-term variations of heavy metals (i.e., Hg, As, Cu, Zn, Pb, Cd) and TPHs, and to assess their potential ecological risks. The results suggested that the ranges for the levels of Hg, As, Cu, Zn, Pb, Cd, and TPHs in sediments between 2019 and 2021 were <0.01-0.07, 0.23-10.72, 8.07-20.67, 25.52-46.55, 10.94-28.19, 0.14-0.56, and 9.14-18.41mgkg-1, respectively. Based on the single factor evaluation (Fi) for sediment quality, we found that most of the evaluation factors in the study area met the requirements of sediment quality standard (i.e., Fi<1), except for the factor of metal Cd in some cases. The implication is that the sediment in the Bohai Sea was fairly clean in terms of heavy metals and TPHs. However, the concentration of metal Cd exceeded the sediment quality standard during May 2019 and 2020 (i.e., Fi>1), indicating that Cd could be identified as a major pollutant in surface sediments. Also, based on the ecological risk assessment (Ei) of heavy metal pollutants, we found that the metal Cd had reached a level with potential ecological risk in some cases (80≤Ei<160). As such, we further suggested that the Cd contamination might have a potential risk on the Bohai Sea' ecosystem.

Metagenomic signature and total petroleum hydrocarbons distribution in a crude oil contaminated ultisol remediated with biochar–humus sediment slurry

AbstractUltisols are peculiar soils generally known for their poor nutrient status. When contaminated, remediation of ultisols present the additional challenge of nutrient and ecological restoration. In this study, we report the distribution of total petroleum hydrocarbons (TPHs) in a simulated crude oil‐contaminated ultisol amended with biochar (BC)/humus sediment (HS) slurry. We also investigated the microbial abundance, diversity, and enzyme expression in the treatment medium that gave the optimum remediation results. We recorded lowest TPH levels in remediant amendments with BC produced at 700°C. Majority of the OTUs (27.96%) found in the remediated ultisol belonged to Firmicutes (27.96%), Proteobacteria (25.88%), and Gemmatimonadetes (23.32%) while enzymes (AlkM, alkB, AlmA, PRM, cP450, MMO/AMO subunits A, B, and C, and Genes ssuD, ssuC, dszC, dszA, and dszB) encountered in this study were expressed mainly by bacteria belonging to the order Actinomycetales and Bulkhoderiales.

Effect of Feedstock Type on Biostimulation Efficiency and Microbial Community Structure during Biochar-Facilitated Remediation of Petroleum Contaminated Soil

This study investigated the effect of plant feedstock– and animal feedstock–derived biochar at 10%w/w and 15%w/w amendment levels on the biostimulation efficiency and the cultivable microbial community in the soil during biochar-facilitated remediation of petroleum contaminated soil using standard techniques. Biostimulation was most effective with the animal-based biochar (ABB) treatment while total petroleum hydrocarbon (TPH) removal was greatest in the plant-based biochar (PBB) amended soil. Observed mean TPH levels on Day 60 ranged from about 7000 mg/kg – 7800 mg/kg for the PBB and 11000 mg/kg – 14000 mg/kg for ABB representing removal levels of roughly 51.0%, 57.7%, 72.4% and 73.7% in 10% ABB, 15% ABB, 10% PBB and 15% PBB amended contaminated soils respectively. The cultivable bacterial diversity for both feedstock types shifted from the combination of Firmicutes, Actinobacteria and Proteobacteria phyla at the onset of the study to predominantly Proteobacteria by the end of the study with a distinct reduction in diversity observed with increasing contact time. The dominant cultivable heterotrophic bacterial isolates were Bacillus spp., Pseudomonas spp. and Staphylococcus aureus for ABB and Pseudomonas spp., Klebsiella pneumoniae and Bacillus spp. for PBB. Amongst the cultivable hydrocarbon utilising bacteria obtained, Klebsiella pneumoniae, Pseudomonas spp. and Enterobacter spp. dominated. There were significant differences in TCHB and CHUB abundance and TPH removal efficiency between PBB and ABB amendments at 95% confidence interval. The study established that application of biochar effectively manages petroleum pollutants in soil by stimulating the proliferation and activities of relevant degradative species.

Response of soil microbial communities to petroleum hydrocarbons at a multi-contaminated industrial site in Lanzhou, China

Total petroleum hydrocarbon (TPH) contamination poses threats to ecological systems and human health. Many studies have reported its negative impacts on soil microbes, but limited information is known about microbial change and response to multiple TPH contamination events. In this study, we investigated TPH contamination level, microbial community structure and functional genes at a multi-contaminated industrial site in Lanzhou, where a benzene spill accident caused the drinking water crisis in 2014. TPHs distribution in soils and groundwater indicated multiple TPH contamination events in history, and identified the spill location where high TPH level (6549 mg kg−1) and high ratio of low-molecular-weight TPHs (>80%) were observed. In contrast, TPH level was moderate (349 mg kg−1) and the proportion of low-molecular-weight TPHs was 44% in soils with a long TPH contamination history. After the spill accident, soil bacterial communities became significant diverse (p = 0.047), but the dominant microbes remained the same as Pseudomonadaceae and Comamonadaceae. The abundance of hydrocarbon-degradation related genes increased by 10–1000 folds at the site where the spill accident occurred in multi-contaminated areas and was significantly related to 2-ring PAHs. Such changes of microbial community and hydrocarbon-degradation related genes together indicated the resilience of soil indigenous microbes toward multiple contamination events. Our results proved the significant change of bacterial community and huge shift of hydrocarbon-degradation related genes after the spill accident (multiple contamination events), and provided a deep insight into microbial response at industrial sites with a long period of contamination history.