Total Petroleum Hydrocarbon Concentration Research Articles

Geospatial Variability and Distribution of Total Petroleum Hydrocarbons (TPH) in Soot-Contaminated Rain and Rivers at Oyigbo, Niger Delta, Nigeria

This comprehensive study delves into the analysis of Total Petroleum Hydrocarbon (TPH) concentrations in soot-contaminated rain and rivers within Oyigbo, Rivers State, Niger Delta, Nigeria, with a primary focus on unraveling the geospatial variability and distribution of TPH in the impacted water sources. The study adopts a multifaceted methodology, incorporating fieldwork, sampling, laboratory analysis, and geospatial mapping using ArcGIS 10.4 software to elucidate spatial variations. Results spotlight the highest rainwater TPH concentrations at MKT 7 - Umuosi Market (128.179 mg/L) and the lowest at SET 13 - Okpontu Settlements (8.976 mg/L), situated in the Okoloma and Umu Agbai-Obete axis, respectively. Likewise, river water exhibits the highest TPH at RVR 5 - Imo River (37.118 mg/L), and the lowest at RVR 6 - Imo River (187.118 mg/L), at Okoloma and Umu Agbai-Obete axis. Analysis of the 41 samples indicates that 19 locations surpass the 50 mg/L acceptable limits set by the World Health Organization (WHO, 2017), and the Department of Petroleum Resources (DRP - EGASPIN, 2018), Nigeria standards, with 10 locations recording concentrations above, and 12 locations falling below 30 mg/L. These findings underscore approximately 46% exhibiting high, 24% displaying medium, and 29 % showcasing low concentrations across the study area, following a spatial pattern with higher pollution dispersion in the Northern and North-western regions at Okoloma and Obigbo axes, and lower pollution levels in the Eastern regions at Umu Agbai-Obete axis. In essence, this study provides a comprehensive insight into TPH in soot-contaminated water resources in Oyigbo, contributing significantly to the advancement of knowledge regarding spatial variation, distribution, and implications for water quality management. Furthermore, it serves as a valuable resource for policy development, offering evidence for targeted environmental programs and practical assistance to environmentalists, researchers, government agencies, and the public in the assessment and enhancement of water quality in affected communities.

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<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<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.

Investigation of the hydrocarbon contamination of the Dibdibba aquifer in Al-Zubair area, southern Iraq

The importance of Al-Zubair area in Basra governorate is highlighted by the presence of agricultural activities. The Dibdibba aquifer is the main supplier of water which used for irrigation, livestock and some different industries are scattered around the region. This research aims to investigate the extent and impact of hydrocarbon contamination of the Dibdibba aquifer in Al-Zubair region, southern Iraq, due to its proximity to oil fields sites. 18 groundwater samples from different locations within the aquifer were collected in dry and wet season to determine their chemical and physical properties and total petroleum hydrocarbon (TPH) including petroleum-based compounds and their derivatives. The analytical results revealed that the Dibdibba groundwater in this area is polluted with TPH and have high levels of electrical conductivity (EC) and total dissolved salts (TDS) due to the high content of salts along with the high concentrations of calcium and magnesium ions. The overall outcomes of the main elements of water showed that it is unfit for human use due to the high levels of the above parameters. All the water tests carried out indicate the presence of contamination with petroleum hydrocarbons, surpassing the allowable limits set by the World Health Organization (2008) and Iraqi Quality Standard (2009). This observed particularly in areas adjacent oil spills, where the TPH concentrations exceeding 35 μg/l in the northwest of Al-Zubair area near the Rumaila oil field. Significantly, this investigation indicated a clear evidence of hydrocarbon contamination in the study area.

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

Bacteria Isolation of Kerosene Contaminated Asphalt Waste (Asbuton)

Kerosene is a type of hydrocarbon commonly known as paraffin oil which is usually used as a home heating fuel, lamp and asphalt solvent. The presence of kerosene in the asphalt production can potentially cause environmental pollution, one of which affects soil conditions. Some bacteria that have specific ability to degrade hydrocarbon content in soil are called hydrocarbonoclastic bacteria. This study aims to determine the proportion of the presence of bacteria that have the potential to degrade hydrocarbons, in this case kerosene, in polluted soil at the location of one of the largest asphalt manufacturing companies in Indonesia and to determine the morphological characters of bacterial isolates. Based on the results of the study, Hydrocarbonoclastic bacteria isolated from asbuton had 5 dominant isolates and were identified by PCR analysis. The results of this study were that the five bacterial isolates were Bacillus sp. with 3 of them being Bacillus subtilis and 2 others being Bacillus cereus. This result has an Entiren stiffness of 99.62% - 100%. The type of bacteria Bacillus sp. are capable of reducing the Total Petroleum Hydrocarbon (TPH) and still able to survive and potentially degrade the TPH content in it.

The effects of the rock stratigraphy on TPH/PAH absorption and transmission in some sections of the Gokana and Khana Local Government Areas

Concentration of TPH/PAH in soils in parts of Gokana and Khana local government areas of Rivers state were examined using samples from 30 shallow wells drilled with hand auger. The core intervals penetrated, ranged between 0 on the surface to 100cm at total depth and was composited into two sections corresponding to upper 0 – 0.5m and lower 0.51 – 0.1m sections respectively. The samples were described to determine their sedimentological characteristics and effect on absorption and transmission of fluids. The total hydrocarbon content in samples of the study area were determined following the EPA 1664 Hexane Method (Method No: EPA 418.1/413.2 & EPA 1664). Individual concentrations of identified PAH congeners were noted and combined to generate the PAH concentrations in each of the two composited sections of the 30 sampled locations. The sedimentology of the logged sections consists mostly of peaty clay, clayey sands and organic clay in the upper section and clayey silt and clayey sand in the lower section. TPH in the study area ranged between 20612mg/kg at Location 15 to 37.09mg/kg at Location 11 for the upper (0 – 0.5m) sections and 14731mg/kg at Location 12 to 14.67mg/kg at Location 17 for the lower (0.51 – 1m) section. PAH ranged from 9.55mg/kg at Location 12 to <0.01mg/kg at several other Locations for the upper (0 – 0.5m) sections and 5.71mg/kg at Location 11 to <0.01mg/kg at several other Locations for the lower (0.51 – 1m) section. Correlation of sedimentology descriptions with the geochemical analysis indicates high concentrations of total petroleum hydrocarbon (TPH) and polycyclic aromatic hydrocarbon (PAH) within the upper (0 – 0.5m) sections than in the lower (0.51 – 0.1m) sections in consonant with the stratigraphy of the logged section.

Analyzing the Presence and Dispersion of Hydrocarbons at Mechanic Workshop Dumpsites, Port Harcourt, Rivers State, Nigeria

The study aimed to analyze the presence and dispersion of hydrocarbons in dumpsites at mechanic workshops in Port Harcourt, Rivers State, Nigeria. Soil samples were collected from within 15-25 cm soil depth from three mechanic workshops in Port Harcourt, situated at Elekahia, Rumeme and Eleme Local Governments. The total petroleum (TPH) and Polycyclic aromatic hydrocarbons (PAHs) concentrations in the soil samples were determined using standard methods. Total TPH concentration in mechanic workshop dumpsites ranged from 9508.18 ppm to 10342.41 ppm, while in the control the concentration was 424.41 ppm. Total PAH concentration in mechanic workshop dumpsites ranged from 312.45 ppm to 1654.08 ppm, while in the control the concentration was 157.89 ppm. All the dumpsites had high levels of PAHs, which was several folds more than in the control. Results revealed that soil at mechanic workshop dumpsites was highly contaminated with hydrocarbons, exceeding the allowable limit 50 mg/kg by the Department oof Petroleum Resources (DPR). Remediation of the soil is recommended, as well as proper management of waste, where relocation of the dumpsite is not possible.

Evaluation of the potentials of <i>Pennisetium glaucum</i> and <i>Vigna unguiculata</i> for phytoremediation of Spent-engine oil contaminated soil

One promising technique for cleaning up soil polluted by spent engine oil is phytoremediation. Particularly in the tropics, where resources can be scarce and the climate is favorable for plant development. Finding plant species that will work well with this technology was the aim of this investigation. The ability of a cereal (Pennisetum glaucum) and a legume (Vigna unguiculata) to remediate soil contaminated with 1%, 2%, 3%, 4%, and 5% (W/V) of spent engine oil was evaluated. After 150 days of incubation, the Total Petroleum Hydrocarbon (TPH) loss in greenhouse studies was calculated. The total petroleum hydrocarbon content of soil that was vegetated with P. glaucum and V. unguiculata was substantially lower than that of non-vegetated soil. Furthermore, a positive association was discovered between the initial TPH and the total petroleum hydrocarbon loss caused by planting P. glaucum. It was also discovered that P. glaucum outperformed V. unguiculata in remediation capacity. These findings suggest that P. glaucum be investigated further, which might lead to a better understanding of how to apply phytoremediation to soils contaminated with spent-engine oil.

Biotesting for adsorptive bioremediation of oil-contaminated podzolic soil in Western Siberia

The majority of Russia’s oil and gas-producing regions are situated in the northern part of Western Siberia, where sandy podzolic soils are prevalent. Due to the low buffering capacity of these soils and the severe Arctic climate, the conventional method of bioremediation for removing oil contamination is not effective. This study, for the first time, explores the potential of adsorptive bioremediation for purifying oil-polluted gley-podzolic soil. This approach involves introducing natural sorbents of various classes before soil treatment through bioremediation. The optimal conditions for soil treatment can be determined using the express phytotests based on white clover ( Trifolium repens ) seed germination. The results indicate that under the best conditions, which involve adding 2 % mixed sorbent based on granulated activated carbon (GAC) and diatomite (4:1) or Spilsorb, it is possible to minimize soil phytotoxicity after 2-3 warm seasons and reduce the content of total petroleum hydrocarbons to the permissible residual oil content (≤5 g/kg) established in the territory of the Khanty-Mansiysk Autonomous Okrug for recultivated agricultural soils. Moreover, other sorbents, such as peat, GAC, vermiculite, zeolite, and diatomite, can be used to reduce phytotoxicity to <33 %, allowing for additional soil decontamination through phytoremediation.

Migration of total petroleum hydrocarbon and heavy metal contaminants in the soil-groundwater interface of a petrochemical site using machine learning: impacts of convection and diffusion.

Convection and diffusion are key pathways for the migration of total petroleum hydrocarbons (TPH) and heavy metals (HMs) from soil to groundwater. However, the extent of their influence on pollutant migration, as well as the nonlinear relationships between these processes and pollutants, remains unclear. This study investigates the spatial distribution of TPH and HMs at a petrochemical site with complex hydrogeological conditions in southwestern China. In addition, machine learning (ML) was used to assess the effects of convection and diffusion on pollutant migration at the soil-groundwater interface. The analysis identifies and reveals TPH, Co, and Ni as the primary pollutants, with soil concentrations reaching 47.427, 7.024, and 4.766 times their respective screening values. Among various ML models, Random Forest (RF) was identified as the most effective, based on R 2, and RMSE performance metrics. The RF model demonstrates that the concentrations of TPH and As are closely related to soil depth. Furthermore, importance indices calculated by RF indicate that the significance of convection and diffusion varies across different soil-groundwater systems. Specifically, at the soil-perched water interface, convection plays a more significant role than diffusion in influencing the migration of TPH and As. However, at the soil-pore water interface, diffusion more significantly influences the migration of all pollutants compared to convection. Additionally, a threshold or saturation effect was observed for the impact of the convection factor on pollutant concentrations in groundwater. These findings highlight the distinct roles of convection and diffusion across various water interfaces, providing new insights into the mechanisms governing contaminant migration and fate.

Assessment of Physicochemical Quality, Heavy Metals, and Total Petroleum Hydrocarbon Concentration in Surface Water from Communities of the Jones Creek Oil Field, Niger Delta Nigeria

Assessment of Physicochemical Quality, Heavy Metals, and Total Petroleum Hydrocarbon Concentration in Surface Water from Communities of the Jones Creek Oil Field, Niger Delta Nigeria

Potential effects of soil petroleum contamination on decomposition of Artemisia annua plant litter.

The accumulation of petroleum contaminants in phytoremediating plants can significantly impact the decomposition of their litter. However, the mechanisms underlying these effects and the potential influence of the contaminant concentration remain unclear. In this study, litter from Artemisia annua plants grown in soil with varying concentrations of petroleum (0, 15, 30, and 45 g kg-1) was collected. The litter samples were then inoculated with soil microorganisms and subjected to an indoor simulation of decomposition under controlled temperature and humidity conditions. Changes in the chemical properties, activities of decomposition-related enzymes in the litter, and decomposition rates were measured. Additionally, structural equation modeling was employed to analyze the mechanism through which soil petroleum contamination affects litter decomposition. The findings revealed several key points: (1) increasing soil petroleum contamination tended to reduce the concentration of carbon and nitrogen in litter while increasing those of lignin and total petroleum hydrocarbons (TPH). (2) Soil petroleum contamination tended to increase the activities of both total lignocellulases and total nutrient cycling-related enzymes in litter. (3) Soil petroleum contamination might indirectly inhibit the activity of lignocellulases by increasing the concentration of lignin and TPH in litter. However, it might also directly accelerate the activity of these enzymes, resulting in contradictory effects on litter decomposition. (4) Finally, A. annua litter produced in soil contaminated with 15 and 30 g kg-1 of petroleum exhibited significantly lower decomposition rates than that from uncontaminated soil.

Bioavailability enhancement of petroleum-contaminated soil by electrokinetic remediation

The Electro kinetic Remediation Technology (EKR) is recognized as the most potential remediation technology for soils with low permeability, like clay soil characteristics. Electrokinetic treatment could increase the bioavailability of contaminants in bioremediation petroleum-contaminated soil. The study, “Bioavailability enhancement of petroleum contaminated soil by electrokinetic remediation,” is experimental research in a laboratory to improve the bioavailability of petroleum hydrocarbons on clay during bioremediation with initial treatment using electrokinetic remediation techniques, finding optimum electrokinetic operating conditions of remediations, and analyzing the mechanism of remediation process in contaminated soil. Bioavailability enhancement was studied for 35 days. Polluted soil was treated with an electrokinetic box test (17cm×12cm×10cm), and DC power was used for 48 hours. Total Petroleum Hydrocarbon (TPH) concentration was determined by gravimetric methods. The results showed that the characteristics of the soil samples were dominated by 49.31% clay. The initial concentration of TPH in polluted soil is 3.7%. The electrokinetic applications during 48 hours and followed by bioremediation for 35 days those processes removed TPH up to 80.74 % (from 33780.66 mg HC (kg dry w)-1 to 6506.155176 mg HC (kg dry w)-1. There is an increase in bioavailability indicated by the rise in bacterial populations and an increase in biodegradation after electrokinetic remediation. With this approach, bioavailability has been increased by 70.18%. Bio-electrokinetic remediation is the recommended method for polluted clay soils with low bioavailability.

Soil residue ecotoxicology from biosurfactant extraction for oily soil decontamination process

Solvent extraction as part of oily soil decontamination process has been including rhamnolipid biosurfactant to be part for seeking its possibility for further implementation. Result of some researchers reported prospect of its implementation due to removal efficiency. This study reported post treatment process assessment to soil residue that remained after the completion of decontamination process. Soil toxicity examined involving Total Petroleum Hydrocarbon (TPH) concentration, Hydrocarbon Structure by using Gas Chromatography-Flame-Ionization Detection (GC-FID), Hydrocarbon bond identification by using Fourier Transform Infra-Red Spectroscopy (FTIR), Toxicity Characteristics Leaching Procedure (TCLP) analysis, Metal and Oxide Metal Content of the residual soil. Germination Index as biological indicator also involved as part of the study to give early indication of impact on residual treated soil. Germination index selected mung bean (Phaseolus radiatus) as object of study. Result showed that at residual soil TPH content could be reduced until 0.78%, there are simplification of hydrocarbon structure after treatment process included weakened of hydrocarbon bonding and concentration observed by FTIR. TCLP result showed residual soil was benign to the environment and Germination Index indicated improvement of mung beans germination after decontamination process.

Minimizing the total petroleum hydrocarbon contaminants in biochar derived from agricultural byproducts

The use of agricultural byproducts as feedstocks for the synthesis of biochar might result in the release of total petroleum hydrocarbons (TPHs) because of the presence of various plastic residues, such as plastic film mulch, gloves, and poles. TPH has been considered a critical health concern for humans worldwide. The aim of the present study was to evaluate the effect of different pyrolysis temperatures and durations on reducing the TPH concentration while synthesizing biochar using agricultural byproducts as feedstock materials. Agricultural byproducts, comprising sawdust and plastic films, were pyrolyzed as feedstocks at temperatures of 400, 500, 600, and 700 °C for durations of 0.5, 1, 2 and 3 h, respectively. Pyrolyzing the feedstock at 500 °C for 1 h and at 600 °C for 0.5 h significantly reduced the TPH concentration in the biochar by 98 and 91 %, respectively, compared to that at 400 °C for 0.5 h. The highest biochar yield was obtained at the lowest pyrolysis temperature (400 °C) and the shortest pyrolysis duration (0.5 h), with a subsequent steady decrease as the temperature and duration increased. These findings underscore the importance of understanding pyrolysis conditions for producing low-cost but high-quality biochar with reduced TPH contaminants and increased biochar yield. This research offers valuable insights for developing sustainable strategies for minimizing the health risks of TPH and utilizing biochar for environmental benefits.

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%.

Microbial functional heterogeneity induced in a petroleum-polluted soil profile

Microbial taxonomic diversity declines with increasing stress caused by petroleum pollution. However, few studies have tested whether functional diversities vary similarly to taxonomic diversity along the stress gradient. Here, we investigated soil microbial communities in a petrochemically polluted site in China. Total petroleum hydrocarbon (TPH) concentrations were higher in the middle (2–3 m) and deep soil layer (3–5 m) than in the surface soil layer (0–2 m). Accordingly, microbial taxonomic α-diversity was decreased by 44% (p < 0.001) in the middle and deep soil layers, compared to the surface soil layer. In contrast, functional α-diversity decreased by 3% (p < 0.001), showing a much better buffering capacity to environmental stress. Differences in microbial taxonomic and functional β-diversities were enlarged in the middle and deep soil layers, extending the Anna Karenina Principle (AKP) that a community adapts to stressful environments in its own way. Consistent with the stress gradient hypothesis, we revealed a higher degree of network connectivity among microbial species and genes in the middle and deep soil layers compared to the surface soil layer. Together, we demonstrate that microbial functionality is more tolerant to stress than taxonomy, both of which were amenable to AKP and the stress gradient hypothesis.

Evaluation of the Effectiveness of Bioaugmentation-Assisted Phytoremediation of Soils Contaminated with Petroleum Hydrocarbons Using Echinacea purpurea

Phytoremediation supported by bioaugmentation is a promising method considered for cleaning up areas polluted with petroleum hydrocarbons. In this study, phytoremediation was carried out using Echinacea purpurea as a phytoremediant on two types of soil: Soil DW—aged soil taken from an excavation pit, Soil OS—soil taken from an oil spill area. The tests for each soil were carried out in six test systems (non-inoculation, inoculation with the B1 microbial consortium, inoculation with the B2 microbial consortium, inoculation with the B1 microbial consortium with the addition of γ-PGA (γ-poly glutamic acid), inoculation with the B2 microbial consortium with the addition of γ-PGA and inoculation with the γ-PGA solution) for 6 months. The effectiveness of the remediation treatments used was assessed based on chromatographic analyses of soil and plant material (roots, shoots) and toxicological analyses using four types of toxicological tests (PhytotoxkitTM (MicroBioTests Inc., Gent, Belgium), OstracodtoxkitTM (MicroBioTests Inc., Gent, Belgium), Microtox® Solid Phase Test (Modern Water Inc., New Castle, DE, USA), MARA (NCIMB Ltd., Aberdeen, UK)). The research conducted showed that the most effective method of bioremediation of soils contaminated with petroleum hydrocarbons was phytoremediation supported by bioaugmentation with the microbial consortium B2 with γ-PGA, which allowed for reducing the concentration of total petroleum hydrocarbons (TPHs) and polycyclic aromatic hydrocarbons (PAHs) in the tested soils by 53.98% and 49.54% (Soil DW-5) and 60.47% and 37.55% (Soil OS-5), respectively. In turn, the lowest bioremediation efficiency was recorded in non-inoculated systems, for which the concentration of TPHs and PAHs at the end of the study decreased by 18.40% and 16.14% (Soil DW-1) and 21.87% and 18.20% (Soil OS-1), respectively. The results of toxicological analyses confirmed the relationship between the concentration of TPHs and PAHs in the soil and its toxicity level.

Spatiotemporal distribution and potential risks of metals and total petroleum hydrocarbons (TPHs) in seawater from the Zhifu Bay and its surrounding areas, Yellow Sea, China (2015–2019)

To investigate the concentrations, spatiotemporal distribution, correlation with environmental factors, and potential risks of four metals (Hg, Cu, Pb, and Cd) and total petroleum hydrocarbons (TPHs) in seawater from the Zhifu Bay and its surrounding areas, surface seawater samples were collected from 10 stations in spring, summer, and autumn of 2015–2019. Compared with values from other regions, the average concentrations of metals and TPHs were in the low and medium levels, respectively. Concentrations of all the study pollutants decreased in the offshore direction, suggesting that most of these pollutants are from land and nearshore sources. Annual variation patterns indicated decreasing trends of Cu and TPHs, and due to the seasonal differences in river discharges, rainfalls, and human activities, wet seasons (summer and/or autumn) exhibited higher concentrations of Hg, Cu, and TPHs than dry season (spring). The potential ecological risk of Cu and carcinogenic health risk of Cd suggest that the discharge of metals from the sea should be more strictly controlled.

Quantitative Assessment of Organic Mass Fluxes and Natural Attenuation Processes in a Petroleum-Contaminated Subsurface Environment

We perceived a trend in the study and practice of petroleum-contaminate sites. Monitored natural attenuation (MNA) can reduce the contaminant concentrations in the soil and groundwater, and it is a method that can remediate the petroleum-contaminated site effectively. MNA is becoming a research focus. This study evaluated MNA using a series of lab-based bench-scale experiments and a large amount of monitoring data from field samplings. Based on the in-site total petroleum hydrocarbon (TPH) results, we used statistical methods, the Mann-Kendall test, and mass fluxes in order to evaluate the MNA of petroleum-contaminated sites in groundwater. The results showed that the TPH concentrations were decreasing, and the plume became smaller. The attenuation rate was from 0.00876 mg/d to 0.10095 mg/d; remediating the petroleum contamination site would cost 1.3 years to 10.6 years. The plume reached a quasi-steady state, and mass flux declined. The most essential process of MNA was biodegradation, and the second was sorption. During the monitoring period, 393 g of TPH was attenuated, including 355 g of TPH gradated by microbes. Biodegradation upstream of the plume was more serious. Iron(Ⅲ) and manganese were the main electron acceptors utilized by microbes during the monitored period. MNA was in progress, and it can be an effective method to remediate the petroleum-contaminated site. Lab-based bench-scale experiments were performed with much monitoring data from the field samplings in order to understand the fate and transport mechanism of the petroleum contamination from the land surface to shallow groundwater according to site conditions.