Phytoremediation using Rizophora mangle L. in mangrove sediments contaminated by persistent total petroleum hydrocarbons (TPH's)

Regulating the biodegradation of petroleum hydrocarbons with different carbon chain structures by composting systems

Composting can decrease petroleum hydrocarbons in petroleum contaminated soils, however the microbial degradation mechanisms and regulating method for biodegradation of petroleum hydrocarbons with different carbon chain structures in the composting system have not yet been investigated. This study analyzed variations of total petroleum hydrocarbon concentrations with C ≤ 16 and C > 16, Random Forest model was applied to identify the key microorganisms for degrading the petroleum hydrocarbon components with specific structure in biomass-amended composting. Regulating method for biodegradation of petroleum hydrocarbons with different carbon chain structures was proposed by constructing the influence paths of "environmental factors-key microorganisms- total petroleum hydrocarbons". The results showed that composting improved the degradation rate of C ≤ 16 fraction and C > 16 fraction of petroleum hydrocarbons by 67.88 % and 61.87 %, respectively. Analysis of the microbial results showed that the degrading bacteria of the C ≤ 16 fraction had degradation advantages in the heating phase of the compost, while the C > 16 fraction degraded better in the cooling phase. Moreover, microorganisms that specifically degraded C > 16 fractions were significantly associated with total nitrogen and nitrate nitrogen. The biodegradation of C ≤ 16 fraction was regulated by organic matter, moisture content, and temperature. The composting system modified by biogas slurry was effective in removing of petroleum hydrocarbons with different carbon chain structures in soil by regulating the metabolic potential of the 46 key microorganisms. This study given their expected importance to achieve the purpose of treating waste with waste and contributing to soil utilization as well as pollution remediation.

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

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

Exploring the bioremediation capability of petroleum-contaminated soils for enhanced environmental sustainability and minimization of ecotoxicological concerns

The bioremediation of soils contaminated with petroleum hydrocarbons (PHCs) has emerged as a promising approach, with its effectiveness contingent upon various types of PHCs, i.e., crude oil, diesel, gasoline, and other petroleum products. Strategies like genetically modified microorganisms, nanotechnology, and bioaugmentation hold potential for enhancing remediation of polycyclic aromatic hydrocarbon (PAH) contamination. The effectiveness of bioremediation relies on factors such as metabolite toxicity, microbial competition, and environmental conditions. Aerobic degradation involves enzymatic oxidative reactions, while bacterial anaerobic degradation employs reductive reactions with alternative electron acceptors. Algae employ monooxygenase and dioxygenase enzymes, breaking down PAHs through biodegradation and bioaccumulation, yielding hydroxylated and dihydroxylated intermediates. Fungi contribute via mycoremediation, using co-metabolism and monooxygenase enzymes to produce CO2 and oxidized products. Ligninolytic fungi transform PAHs into water-soluble compounds, while non-ligninolytic fungi oxidize PAHs into arene oxides and phenols. Certain fungi produce biosurfactants enhancing degradation of less soluble, high molecular-weight PAHs. Successful bioremediation offers sustainable solutions to mitigate petroleum spills and environmental impacts. Monitoring and assessing strategy effectiveness are vital for optimizing biodegradation in petroleum-contaminated soils. This review presents insights and challenges in bioremediation, focusing on arable land safety and ecotoxicological concerns.

Phytoremediation of crude oil-contaminated sediment using Suaeda heteroptera enhanced by Nereis succinea and oil-degrading bacteria

A 150-day experiment was performed to investigate the stimulatory effect of a promising phytoremediation strategy consisting of Suaeda heteroptera (S. heteroptera), Nereis succinea (N. succinea), and oil-degrading bacteria for cleaning up total petroleum hydrocarbons (TPHs) in spiked sediment. Inoculation with oil-degrading bacteria and/or N. succinea increased plant yield and TPH accumulation in S. heteroptera plants. The highest TPH dissipation (40.5%) was obtained in the combination treatment, i.e., S. heteroptera + oil-degrading bacteria + N. succinea, in which the sediment TPH concentration decreased from an initial value of 3955 to 2355 mg/kg in 150 days. BAF, BCF, and TF confirmed the role of N. succinea and oil-degrading bacteria in the amelioration and translocation of TPHs. In addition, TPH toxicity of S. heteroptera was alleviated by N. succinea and oil-degrading bacteria addition through the reduction of oxidative stress. Therefore, S. heteroptera could be used for cleaning up oil-contaminated sediment, particularly in the presence of oil-degrading bacteria + N. succinea. Field studies on oil-degrading bacteria + N. succinea may provide new insights on the rehabilitation and restoration of sediments contaminated by TPHs.

Development of Rhizophora mangle (Rhizophoraceae) and Avicennia schaueriana (Avicenniaceae) in the presence of a hydrocarbon-degrading bacterial consortium and marine diesel oil

The development of Rhizophora mangle and Avicennia schaueriana seedlings impacted by marine diesel oil (MDO) was evaluated in the presence or absence of a hydrocarbon-degrading bacterial consortium (HBC). The bioassays were conducted in a greenhouse during 6 months and consisted of three different treatments (control, MDO only and MDO + HBC). The bacterial consortium was mainly composed of Bacillus spp. (73%), but Rhizobium spp., Pseudomonas spp., Ochrobactrum spp., and Brevundimonas spp. were also present. After 6 months, A. schaueriana seedlings showed higher mortality compared to those of R. mangle; R. mangle exhibited 68% (control), 44% (MDO alone) and 50% (MDO + HBC) seedlings survivorship compared to 42% (control), 0% (MDO alone) and 4% (MDO + HBC) for A. schaueriana. This variability may be due to differences in species physiology. Stem growth, diameter and number of leaves remained constant during the 6 months of the experiment with marine diesel oil and hydrocarbon-degrading bacterial consortium (MDO + BBC). For both mangrove species, bacterial enzymatic activity in the sediments was sufficient to maintain cell counts of 10⁷ cells cm^-3 in the rhizospheric soil and possibly synthetize the extracellular polymeric substances (EPS) that may emulsify and solubilize oil products.

Assessment of role of rhizosphere process in bioaccumulation of heavy metals in fine nutritive roots of riparian mangrove species in river Hooghly: Implications to global anthropogenic environmental changes

Biota of coastal estuarine habitats of tropics and subtropics are extremely vulnerable. In the study, we have investigated the role of rhizosphere process in bio-accumulation of heavy metals in fine nutritive roots of riparian mangroves at eleven sampling locations of river Hooghly. The rhizospheric sediment of river Hooghly was accumulating HMs due to the presence of organic content and anthropogenic inputs. The mean EF (2.03-8.3), Igeo (-2.27-0.71), and CF (0.62-2.53) values signifies the enrichment of HMs in sediment fine fraction (<62.5 μm) whereas, the mean PLI (0.83 to 1.18) indicates gradual environmental degradation of river Hooghly. Low BCF observed in the river Hooghly might be due to barrier to hypodermal structures and/or any prevailing mechanism of saturation of HMs. However, BCF > 1 for Al, Cu, Cr, Mn, and Zn, signifies the phyto-remediation potential of riparian mangroves to mitigate amplified global anthropogenic environmental changes.

Understanding potentially toxic metal (PTM) induced biotic response in two riparian mangrove species Sonneratia caseolaris and Avicennia officinalis along river Hooghly, India: Implications for sustainable sediment quality management

Elevated human-induced activities have prompted significant uncontrolled release of potentially toxic metals (PTM) to the undisturbed ecosystem throughout the globe. Riparian mangrove vegetations act as a natural purifier of wastewaters and assist in maintaining a healthy ecosystem. We have investigated the elevated PTM-induced stress and biotic response of two riparian mangrove species e.g. Sonneratia caseolaris and Avicennia officinalis by river Hooghly. The increased PTM concentrations were observed throughout the river bank; with the maximum pollution load at Chemaguri (S9). Except Co, Cr and Pb, higher enrichment factor (1.97-8.89) and contamination factor (0.64-2.88) values were observed for Cd, Cu, Fe, Zn. Mn, and Ni. Geo-accumulation index (-2.2 - 0.92) values indicates natural geogenic accumulation of Cu in the riparian mangrove sediment. Thus, sediment quality indices suggest except Cu, enrichment of all studied PTMs was sourced from anthropogenic activities. The sediment of the region when compared with consensus-based sediment quality guidelines shows considerable ecotoxicological risks and threat towards human health considering Ni accumulation. The highest potential ecological risk index value was observed in Chemaguri (S9). The biotic response of riparian mangroves was characterized by reduced photosyhthetic pigments (Chlorophyll a and Chlorophyll b) and increased activity of antioxidative stress enzymes (POD, CAT and SOD). Significant statistical relationship between antioxidative enzyme activity, photosynthetic pigments and bioaccumulated PTMs reflects active functioning of detoxification mechanism in the riparian mangrove species.

Response and capability of Scirpus mucronatus (L.) in phytotreating petrol-contaminated soil

The greenhouse phytotoxicity experiment was conducted to analyse and assess the capability of Scirpus mucronatus (L.) in tolerating and removing petrol in contaminated soil. This research was conducted for 72 days by using 5, 10 and 30 g/kg petrol as soil contaminants. Results showed that the system planted with S. mucronatus (L.) had high potential to treat the 10 g/kg petrol-contaminated soil and had an average Total Petroleum Hydrocarbon (TPH) removal of 82.1%. At 5 and 30 g/kg petrol, the planted system removed 74.9% and 75.8% TPH, respectively. The petrol (10 g/kg) affected the plant growth positively, which was indicated by the increase in dry and wet weights throughout the research period. The removal of the TPH in the system was performed because of the interaction of plants and rhizobacteria. SEM showed that a high concentration of petrol (30 g/kg) affected the plant tissue negatively, as indicated by the altered structures of the root and stem cells. EDX results also confirmed that petrol was absorbed by the plant, as shown by the increased carbon content in the plant's root and stem after the treatment.

Remediation of petrol hydrocarbon-contaminated marine sediments by thermal desorption

In this study, a hydrocarbon-contaminated marine sediment was treated applying ex-situ thermal desorption (ESTD) at bench-scale. Temperatures up to 280 °C and heating times (t) in the 5-30 min range were investigated. Results revealed that temperatures in the range 200-280 °C led to Total Petrol Hydrocarbon (TPH)-removal efficiency (RE) from 75 to 85% (t = 10 min). The maximum RE of 89% was obtained at 200 °C for 30 min. However, a shorter remediation time of 5 min (or lower temperatures of 160 and 180 °C with longer times) is needed to reach the TPH standard limit. Data also demonstrated the selectivity of the treatment in TPH fraction removal. The modelling of the TPH removal kinetics and desorption isotherm jointly with activation energy calculation (>30 kJ mol^-1) indicated that ESTD process is quite unfavorable for marine sediments. This is due to the fact that ESTD is regulated by chemisorption processes and occurred in two distinct TPH removal phases: evaporation and boiling vaporization. This depends on the strong affinity of the TPH with the fine sediment particles, as well as on the high initial water, salinity, organic matter and sulfides content. However, the comparison between alternative processes has shown that ESTD is the most feasible treatment process for TPH-contaminated marine sediment remediation. Obtained results also add relevant information that can be used as a basis for future scaling-up investigations of ESTD for hydrocarbon-contaminated marine sediments.

Human health risks from fish consumption following a catastrophic gas oil spill in the Chiquito River, Veracruz, Mexico

An industrial accident resulted in a gas oil spill of 11,808 barrels in the upper part of the Coatzacoalcos River watershed. After river shore cleanup, concentrations of total petroleum hydrocarbons (TPH) and polycyclic aromatic hydrocarbons (PAH) in muscle (+ skin) were determined in captured fish to evaluate human health risk due to fish consumption post-spill in the most affected communities. Data on fish consumption, body weight, and diet factor were collected by questionnaires and field observations. Using standard formulas for carcinogenic and non-carcinogenic substances, site-specific remediation levels were calculated in fish, comparing them to the real levels observed. Likewise, the levels of PAHs in fish captured pre- and post-spill were compared to determine their origin (pyrolytic vs. petrogenic). The TPH concentrations were between 119,000 and 523,000 ng/g (dry weight) and no significant difference (P > 0.05) was found pre- vs. post-spill. The concentration of total PAHs varied between 2494.83 and 35,412.23 ng/g (dry weight), with the concentrations of naphthalene (520.9 ng/g) and phenanthrene (7532.7 ng/g) being much higher than in control samples, and being from the gas oil spill (petrogenic origin). The site-specific remediation levels calculated for TPH and PAH were much higher than the maximum levels actually detected. No human health risks were found from hydrocarbons from the spill, at least after cleanup efforts and natural attenuation (six months).

Phytoremediation of polycyclic aromatic hydrocarbons (PAHs) in mangrove sediments using Rhizophora mangle

A phytoremediation experiment was carried out in mesocosms to investigate the performance of Rhizophora mangle in the remediation of polycyclic aromatic hydrocarbons (PAHs) in mangrove sediment contaminated with crude oil. The water pH of the experiments (phytoremediation and natural attenuation) ranged from 4.9 to 8.4 at 0 and 90 days, respectively. The oxy-reduction potential (Eh) ranged from oxidising (108.0 mV, time 0) to reducing (approximately -110.0 mV, time 90) environments. Dissolved oxygen (DO) ranged from 5.7 mg L^-1 (time 0) to 4.5 mg L^-1 and 3.6 mg L^-1 (time 90) in phytoremediation and natural attenuation, respectively. The sediments had silty texture and an average concentration of 5% organic matter (OM). Phytoremediation (60.76%) showed better efficiency in the remediation of the 16 PAHs compared to natural attenuation (49.57%). Principal component analyses showed a correlation between the concentrations of PAHs with pH, Eh, OM and DO in both experiments.

Biogas slurry as an activator for the remediation of petroleum contaminated soils through composting mediated by humic acid

Soil pollution caused by petroleum hydrocarbons is a widespread environmental problem. Composting is one of the cost-effective solutions for petroleum hydrocarbons removal but limited by low efficiency of bioremediation, leading to high phytotoxicity. Given that biogas slurry as nutrients can alter the microbial activity, the aim of this study was to investigate the role of biogas slurry on the remediation of petroleum contaminated soils in composting. Herein, we added biogas slurry into the composting of hydrocarbon contaminated soil to investigate its effect on the biodegradation of petroleum hydrocarbons, humic acid (HA) transformation and the safety of product. The results showed that biogas slurry addition improved the degradation of organic matter and total petroleum hydrocarbons (TPH) (especially C > 16), but also increased 18.0% of germination index and the humification degree of HA. The estrone from biogas slurry was removed during composting and did not affect the phytotoxicity level of compost. Redundancy analysis and structural equation modeling indicated that TPH degradation was significantly related to the humification of HA components and total nitrogen from biogas slurry, which contributed to composting safety. Therefore, biogas slurry could be a possible activator for the remediation of petroleum contaminated soils through composting mediated by HA transformation, which is beneficial to obtain the composts with a lower phytotoxicity and higher maturity for soil application.

Assessing and Modelling the Efficacy of Lemna paucicostata for the Phytoremediation of Petroleum Hydrocarbons in Crude Oil-Contaminated Wetlands

The potentials of the invasive duckweed species, Lemna paucicostata to remove pollutants from aquatic environment was tested in a constructed wetlands as an ecological based system for the phytoremediation of petroleum hydrocarbons in crude oil-contaminated waters within 120 days. Total petroleum hydrocarbons in wetlands and tissues of duckweed were analyzed using gas chromatography with flame ionization detector following established methods while the experimental data were subjected to the first-order kinetic rate model to understand the remediation rate of duckweed in wetlands. L. paucicostata effected a significant (F = 253.405, P < 0.05) removal of hydrocarbons from wetlands reaching 97.91% after 120 days. Assessment on the transport and fate of hydrocarbons in duckweed indicated that L. paucicostata bioaccumulated less than 1% and significantly biodegraded 97.74% of hydrocarbons in wetlands at the end of the study. The experimental data reasonably fitted (r2 = 0.938) into the first-order kinetic rate model. From the result of the study, it is reasonable to infer that L. paucicostata is an effective aquatic macrophyte for the removal of petroleum hydrocarbons in moderately polluted waters.

Rhizosphere assisted biodegradation of benzo(a)pyrene by cadmium resistant plant-probiotic Serratia marcescens S2I7, and its genomic traits

Melia azedarach-rhizosphere mediated degradation of benzo(a)pyrene (BaP), in the presence of cadmium (Cd) was studied, using efficient rhizobacterial isolate. Serratia marcescens S2I7, isolated from the petroleum-contaminated site, was able to tolerate up to 3.25 mM Cd. In the presence of Cd, the isolate S2I7 exhibited an increase in the activity of stress-responsive enzyme, glutathione-S-transferase. Gas Chromatography-Mass spectroscopy analysis revealed up to 59% in -vitro degradation of BaP after 21 days, while in the presence of Cd, the degradation was decreased by 14%. The bacterial isolate showed excellent plant growth-promoting attributes and could enhance the growth of host plant in Cd contaminated soil. The 52,41,555 bp genome of isolate S. marcescens S2I7 was sequenced, assembled and annotated into 4694 genes. Among these, 89 genes were identified for the metabolism of aromatic compounds and 172 genes for metal resistance, including the efflux pump system. A 2 MB segment of the genome was identified to contain operons for protocatechuate degradation, catechol degradation, benzoate degradation, and an IclR type regulatory protein pcaR, reported to be involved in the regulation of protocatechuate degradation. A pot trial was performed to validate the ability of S2I7 for rhizodegradation of BaP when applied through Melia azedarach rhizosphere. The rhizodegradation of BaP was significantly higher when augmented with S2I7 (85%) than degradation in bulk soil (68%), but decreased in the presence of Cd (71%).

Phragmites australis in combination with hydrocarbons degrading bacteria is a suitable option for remediation of diesel-contaminated water in floating wetlands

The presence of diesel in the water could reduce the growth of plant and thus phytoremediation efficacy. The toxicity of diesel to plant is commonly explained; because of hydrocarbons in diesel accumulate in various parts of plants, where they disrupt the plant cell especially, the epidemis, leaves, stem and roots of the plant. This study investigated the effect of bacterial augmentation in floating treatment wetlands (FTWs) on remediation of diesel oil contaminated water. A helophytic plant, Phragmites australis (P. australis), was vegetated on a floating mat to establish FTWs for the remediation of diesel (1%, w/v) contaminated water. The FTWs was inoculated with three bacterial strains (Acinetobacter sp. BRRH61, Bacillus megaterium RGR14 and Acinetobacter iwoffii AKR1), possessing hydrocarbon degradation and plant growth-enhancing capabilities. It was observed that the FTWs efficiently removed hydrocarbons from water, and bacterial inoculation further enhanced its hydrocarbons degradation efficacy. Diesel contaminated water samples collected after fifteen days of time interval for three months and were analyzed for pollution parameters. The maximum reduction in hydrocarbons (95.8%), chemical oxygen demand (98.6%), biochemical oxygen demand (97.7%), total organic carbon (95.2%), phenol (98.9%) and toxicity was examined when both plant and bacteria were employed in combination. Likewise, an increase in plant growth was seen in the presence of bacteria. The inoculated bacteria showed persistence in the water, root and shoot of P. australis. The study concluded that the augmentation of hydrocarbons degrading bacteria in FTWs is a better option for treatment of diesel polluted water.

Rhamnolipid production using Shewanella seohaensis BS18 and evaluation of its efficiency along with phytoremediation and bioaugmentation for bioremediation of hydrocarbon contaminated soils

This study reports the combined use of a rhamnolipid type biosurfactant (BS) along with phytoremediation and bioaugmentation (BA) for bioremediation of hydrocarbon-contaminated soils. Bacterial isolates obtained from hydrocarbon contaminated soil were screened for rhamnolipid production and isolate BS18, identified as Shewanella seohaensis, was selected for bioremediation experiments. Growth of BS18 in mineral salt medium (MSM) with diesel oil as the carbon source showed a maximum biomass of 8.2 g L^-1, rhamnolipid production of 2.2 mg g^-1 cell dry weight, surface tension reduction of 28.6 mN/m and emulsification potential (EI₂₄%) of 65.6. Characterization of rhamnolipid based on Fourier transmittance infrared (FTIR) analysis confirmed the presence of OH, CH₂/CH₃, C=O, and COO stretching vibrations, respectively, which are distinctive features of rhamnolipid type BSs. In bioremediation experiments, the lowest hydrocarbon concentration of 2.1 mg g^-1 of soil for non-sterilized soil and 4.3 mg g^-1 of soil for sterilized soil was recorded in the combined application of rhamnolipid, phytoremediation, and BA. This treatment also yielded the highest hydrocarbon degrading bacterial population (6.4 Log Cfu g^-1 of soil), highest plant biomass (8.3 g dry weight plant^-1), and the highest hydrocarbon uptake (512.3 mg Kg^-1 of plant).

Enhanced rhizoremediation of crude oil-contaminated mangrove swamp soil using two wetland plants (Phragmites australis and Eichhornia crassipes)

Comparative studies of enhanced rhizoremediation with biostimulation and bioaugmentation techniques in remediation of oil-contaminated mangrove environment were investigated. Contaminated soils at 7190 mg/kg of oil were subjected to the following treatments: soil (S), soil + oil (SO), soil + oil + fertilizer (NPK) (SOF), soil + oil + fertilizer + microorganisms (SOFM), soil + oil + fertilizer + microorganisms + solarization (SOFMS) (triplicates): two sets planted with P. australis, E. crassipes, and one unplanted. These were studied comparatively for 120 days for culturable (aerobic, mesophilic) heterotrophic and hydrocarbon-utilizing microbial populations, and soil residual TPH. Results showed culturable heterotrophic and hydrocarbon-utilizing microbial populations and TPH loss in planted soils were consistently higher than those in unplanted receiving corresponding treatments (P ˂ 0.05). There were 44.4, 71.8, 74.7, and 67.5, and 50.5, 71.8, 82.3, and 71.8% reduction in residual TPH in soil planted with P. australis and E. crassipes respectively for treatments PSO, PSOF, PSOFM, and PSOFMS as against 20.0, 62.6, 67.5, and 67.5% losses in SO, SOF, SOFM, and SOFMS. Treatments PSOFM and SFOM recorded the highest TPH loss with daily residual TPH loss in the order as follows: E. crassipes (49.20 mg/kg/day) ˃ P. australis (44.64 mg/kg/day) ˃ unplanted soil (40.32 mg/kg/day). Enhanced rhizoremediation was more effective than biostimulation and bioaugmentation techniques.

Potential application of oil-suspended particulate matter aggregates (OSA) on the remediation of reflective beaches impacted by petroleum: a mesocosm simulation

This paper presents the oil-suspended particulate matter aggregate (OSA) resulted from the interaction of droplets of dispersed oil in a water column and particulate matter. This structure reduces the adhesion of oil on solid surfaces, promotes dispersion, and may accelerate degradation processes. The effects of the addition of fine sediments (clay + silt) on the formation of OSA, their impact on the dispersion and degradation of the oil, and their potential use in recovering reflective sandy beaches were evaluated in a mesoscale simulation model. Two simulations were performed (21 days), in the absence and presence of fine sediments, with four units in each simulation using oil from the Recôncavo Basin. The results showed that the use of fine sediment increased the dispersion of the oil in the water column up to four times in relation to the sandy sediment. There was no evidence of the transport of hydrocarbons in bottom sediments associated with fine sediments that would have accelerated the dispersion and degradation rates of the oil. Most of the OSA that formed in this process remained in the water column, where the degradation processes were more effective. Over the 21 days of simulation, we observed a 40 % reduction on average of the levels of saturated hydrocarbons staining the surface oil.

Biodegradation of polycyclic aromatic hydrocarbons (PAHs) in a diesel oil-contaminated mangrove by plant growth-promoting rhizobacteria

In this study, Rhizophora mangle L. mangrove plants and plant growth-promoting bacteria were evaluated for their ability to degrade polycyclic aromatic hydrocarbons in diesel oil-contaminated sediment. The diesel-contaminated soil was sown with plant growth-promoting bacteria in the R. mangle L. rhizosphere and monitored for 120 days in a greenhouse. The plant growth-promoting bacteria Pseudomonas aeruginosa and Bacillus sp. were analyzed for their ability to degrade eight priority polycyclic aromatic hydrocarbons, achieving a removal rate for naphthalene (80%), acenaphthene (> 60%), anthracene (> 50%), benzo(a)anthracene (> 60%), benzo(a)pyrene (> 50%) and dibenzo(a,h)anthracene (> 90%) in the treatments with and without plants. R. mangle L. demonstrated a removal rate above 50% for acenaphthene and fluoranthene. The bacterial strains promoted the development of the plant propagule in 55% of sediment contaminated with diesel. Scanning electron microscopy revealed the formation of biofilms by the strains in the roots of the plants in contact with the diesel. Thus, the interaction between Rhizophora mangle L. and the bacterial strains (Bacillus sp. and P. aeruginosa) demonstrated the potential of the strains to degrade diesel and bioremediate mangroves impacted by diesel oil.

Biosurfactant-assisted phytoremediation of multi-contaminated industrial soil using sunflower (Helianthus annuus L.)

This study evaluated the use of commercial rhamnolipid biosurfactant supplementation in the phytoremediation of a soil via sunflower (Helianthus annuus L.) cultivation. The soil, obtained from an industrial area, was co-contaminated with heavy metals and petroleum hydrocarbons. The remediation tests were monitored for 90 days. The best results for removal of contaminants were obtained from the tests in which the sunflower plants were cultivated in soil with 4 mg kg^-1 of the rhamnolipid. Under these conditions, reductions of 58% and 48% were obtained in the total petroleum hydrocarbon (TPH) and polycyclic aromatic hydrocarbon (PAH) concentrations, respectively; reductions in the concentrations of the following metals were also achieved: Ni (41%), Cr (30%), Pb (29%), and Zn (20%). The PCR-DGGE analysis of soil samples collected before and after the treatments verified that the plant cultivation and biosurfactants supplementation had little effect on the structure of the dominant bacterial community in the soil. The results indicated that sunflower cultivation with the addition of a biosurfactant is a viable and efficient technology to treat soils co-contaminated with heavy metals and petroleum hydrocarbons.

Rhizospheric microorganisms as a solution for the recovery of soils contaminated by petroleum: A review

Petroleum is currently the world's main energy source, and its demand is expected to increase in coming years. Its intense exploitation can lead to an increase in the number of environmental accidents, such as spills and leaks, and an increase in the generation of environmental liabilities resulting from refining. Due to its hydrophobic characteristics and slow process of biodegradation, petroleum can remain in the environment for a long time and its toxicity can cause a negative impact on both terrestrial and aquatic ecosystems, with the main negative effects related to its carcinogenic potential for both animals and humans. The objective of the present review is to discuss environmental contamination by oil, conventional treatment techniques and bioremediation an alternative tool for recovery petroleum-contaminated soils, focusing on the rhizodegradation process, plant growth-promoting rhizobacteria (PGPR), a phytoremediation strategy in which the microorganisms that colonize the roots of phytoremediatior plants are responsible for the biodegradation of petroleum. These microorganisms can be selected and tested individually or in the form of consortia to evaluate their potential for oil degradation, or even to measure the use of biosurfactants produced by them to constitute tools for the development of environmental recovery strategies and biotechnological application.

Leucanthemum vulgare lam. crude oil phytoremediation

Sites with crude oil pollution have been successfully treated using phytoremediation, but expanding the range of plants that can be used and understanding how exposure impacts the plants are two areas of study that are important to continue. Leucanthemum vulgare has been shown to grow well under a variety of stressful conditions. To examine L. vulgare's ability to both survive crude oil exposure and to reduce crude oil concentrations in soil, plants were placed in soil containing 0, 2.5, 5, 7.5, or 10% w/w crude oil. Total petroleum hydrocarbons (TPH) concentration, peroxidase and catalase activity, proline and phenol content in roots and leaves were determined at the start of planting and every 2 months for 6 months. L. vulgare roots were successfully colonized with mycorrhizae under all conditions. Results showed positive correlation between antioxidant compound concentration and crude oil contamination. Also, a significant reduction occurred in TPH content of soil over time in planted pots as compared to controls. The lowest TPH content was recorded after 6 months under all treatments. Results showed L. vulgare could survive crude oil exposure and enhance reducing of crude oil from soil.

Potential of the green alga Chlorella vulgaris for biodegradation of crude oil hydrocarbons

Oil production and/or transportation can cause severe environmental pollution and disrupt the populations of living organisms. In the present study, biodegradation of petroleum hydrocarbons is investigated using Chlorella vulgaris as a green algal species. The microalga was treated by 10 and 20g/l crude oil/water concentrations at two experimental durations (7 and 14days). Based on the results obtained, C. vulgaris owned not only considerable resistance against the pollutants but also high ability in remediation of crude oil hydrocarbons (~94% of the light and ~88% of heavy compounds in 14days). Intriguingly, dry weight of C. vulgaris increased by the rising crude oil concentration indicating the positive effect of crude oil on the growth of the algal species. This biodegradation process is remarkably a continuous progression over a period of time.

Are pioneer mangroves more vulnerable to oil pollution than later successional species?

Propagules of Avicennia marina, Bruguiera gymnorrhiza and Rhizophora mucronata were cultivated in rhizotrons (root observation chambers) and subjected to sediment oiling treatments for 409days to determine the effects of oil on root growth. Oiling reduced root length, specific root length, relative root growth rate and root diameter, while specific root volume increased. Oiling reduced root length by 96% in A. marina, 99% in B. gymnorrhiza and 80% in R. mucronata, while specific root volume increased by 34%, 29% and 23% respectively. Relative root growth rate decreased in the oiled treatments by 84%, 80% and 73% respectively. Avicennia exhibits typical root traits of a pioneer species compared to slower-growing later successional species like B. gymnorrhiza and R. mucronata. These traits of A. marina not only allow more rapid establishment of seedlings, but also expose a larger root surface area and therefore greater susceptibility to oil contamination than the other species.

Phytoremediation of contaminated soils containing gasoline using Ludwigia octovalvis (Jacq.) in greenhouse pots

Greenhouse experiments were carried out to determine the phytotoxic effects on the plant Ludwigia octovalvis in order to assess its applicability for phytoremediation gasoline-contaminated soils. Using plants to degrade hydrocarbons is a challenging task. In this study, different spiked concentrations of hydrocarbons in soil (1, 2, and 3 g/kg) were tested. The results showed that the mean efficiency of total petroleum hydrocarbon (TPH) removal over a 72-day culture period was rather high. The maximum removal of 79.8 % occurred for the 2 g/kg concentration, while the removal rate by the corresponding unplanted controls was only (48.6 %). The impact of gasoline on plants included visual symptoms of stress, yellowing, growth reduction, and perturbations in the developmental parameters. The dry weight and wet weight of the plant slightly increased upon exposure to gasoline until day 42. Scanning electron microscopy (SEM) indicated change to the root and stem structure in plant tissue due to the direct attachment with gasoline contaminated compared to the control sample. The population of living microorganisms in the contaminated soil was found to be able to adapt to different gasoline concentrations. The results showed that L. octovalvis and rhizobacteria in gasoline-contaminated soil have the potential to degrade organic pollutants.

Spatial distribution and concentration assessment of total petroleum hydrocarbons in the intertidal zone surface sediment of Todos os Santos Bay, Brazil

The primary objective of this study was to investigate the concentrations and spatial distribution of the total petroleum hydrocarbons (TPHs) in the intertidal zone surface sediment of Todos os Santos Bay, Brazil, to assess the distribution and degree of contamination by TPHs, measure the level of TPH degradation in the surface sediment, and identify the organic matter sources. The surface sediment used in this study was collected in 50 stations, and TPHs, isoprenoid alkanes (pristane and phytane), and unresolved complex mixture (UCM) were analyzed by gas chromatography with a flame ionization detector. The total concentrations ranged from 0.22 to 40,101 μg g(-1) dry weight and showed a strong correlation with the total organic carbon (TOC) content. The highest TPH concentrations were observed in samples from the mangrove sediments of a river located near a petroleum refinery. Compared with other studies in the world, the TPH concentrations in the intertidal surface sediment of Todos os Santos Bay were below average in certain stations and above average in others. An analysis of the magnitude of UCM (0.11 to 17,323 μg g(-1) dry weight) and the ratios nC17/Pr and nC18/Ph suggest that an advanced state of oil weathering, which indicates previous contamination. The molar C/N ratios varied between 5 and 43, which indicate organic matter with a mixed origin comprising marine and continental contributions.

Bioresources for control of environmental pollution

Environmental pollution is one of the biggest threats to human beings. For practical reasons it is not possible to stop most of the activities responsible for environmental pollution; rather we need to eliminate the pollutants. In addition to other existing means, biological processes can be utilized to get rid of toxic pollutants. Degradation, removal, or deactivation of pollutants by biological means is known as bioremediation. Nature itself has several weapons to deal with natural wastage and some of them are equally active for eliminating nonnatural pollutants. Several plants, microorganisms, and some lower eukaryotes utilize environmental pollutants as nutrients and some of them are very efficient for decontaminating specific types of pollutants. If exploited properly, these natural resources have enough potential to deal with most elements of environmental pollution. In addition, several artificial microbial consortia and genetically modified organisms with high bioremediation potential were developed by application of advanced scientific tools. On the other hand, natural equilibria of ecosystems are being affected by human intervention. Rapid population growth, urbanization, and industrialization are destroying ecological balances and the natural remediation ability of the Earth is being compromised. Several potential bioremediation tools are also being destroyed by biodiversity destruction of unexplored ecosystems. Pollution management by bioremediation is highly dependent on abundance, exploration, and exploitation of bioresources, and biodiversity is the key to success. Better pollution management needs the combined actions of biodiversity conservation, systematic exploration of natural resources, and their exploitation with sophisticated modern technologies.

A phytotoxicity test of bulrush (Scirpus grossus) grown with diesel contamination in a free-flow reed bed system

In this study, bulrush (Scirpus grossus) was subjected to a 72 day phytotoxicity test to assess its ability to phytoremediate diesel contamination in simulated wastewater at different concentrations (0, 8700, 17,400 and 26,100mg/L). Diesel degradation by S. grossus was measured in terms of total petroleum hydrocarbon (TPH-D). The TPH-D concentration in the synthetic wastewater was determined with the liquid-liquid extraction method and gas chromatography. S. grossus was found to reduce TPH-D by 70.0 and 80.2% for concentrations of 8700 mg/L and 17,400mg/L, respectively. At a diesel concentration of 26,100mg/L, S. grossus died after 14 days. Additionally, the biomass of S. grossus plants was found to increase throughout the phytotoxicity test, confirming the ability of the plant to survive in water contaminated with diesel at rates of less than 17,400mg/L.