Highly efficient screening and optimal combination of functional isolates for bioremediation of hydrocarbon-polluted soil

The key to enhancing the efficacy of bioremediation of hydrocarbon-contaminated soil is the precise and highly efficient screening of functional isolates. Low screening effectiveness, narrow screening range and an unstable structure of the constructed microflora during bioremediation are the shortcomings of the traditional shaking culture (TSC) method. To improve the secondary screening of isolates and microflora implemented for alkane degradation, this work evaluated the characterization relationship between bacterial function and enzyme activity and devised an enzyme activity assay (EAA) method. The results indicated a substantial positive correlation (r = 0.97) between 24 candidate isolates and their whole enzymes, proving that whole enzyme activity properly reflects the metabolic functions of microorganisms. The functional analysis of the isolates demonstrated that the EAA method in conjunction with microbial abundance and metabolite determination could broaden the screening range of functional isolates, including aliphatic acid-metabolizing isolates (isolates H4 and H7) and aliphatic acid-sensitive isolates (isolate H2) with n-hexadecane degradation ability. The EAA method also guided the construction of functional microflora and optimized the mode of application using combinations of alkane-degrading bacteria and aliphatic acid-degrading bacteria successively (e.g., F1+H7+H7). The combinations maintained a high abundance of functional isolates and stable α diversity and community composition throughout the experiment, which contributed to more advanced alkane degradation and mineralization ability (p < 0.01). Assuming a workload of 100 tests, the screening efficiency of the EAA method is more than 16 times that of the TSC method, and the greater the quantity of isolates, the higher the screening efficiency, enabling high-throughput screening. In conclusion, the EAA method has a broad-spectrum, accurate and highly efficient screening ability for functional isolates and microflora, which can provide intensive technical support for the development of bioremediation materials and the application of bioremediation technology.

Investigating the succession process of native desert plants over hydrocarbon-contaminated soils using remote sensing techniques

Hydrocarbon-contaminated soils are considered as one of the major environmental issues that harm human well-being, particularly in arid regions of the world. Phytoremediation is a possible mitigation measure for this issue and has been suggested as it is cost-effective compared with other remediation technologies for soil clean-up, such as soil thermal treatment and soil washing. However, there are still gaps in the literature regarding the behavior of annual and perennial desert plants and their ability to survive in hydrocarbon-contaminated soils in arid ecosystems. Therefore, this study aims to develop an integrated approach using remote sensing techniques to understand the behavior of annual and perennial desert plants over different types of oil-contaminated soils (oil tarcrete, wet-oil lake, bare soil, and vegetation cover) in the Kuwait Desert and to explore the impact of climate and physical soil properties on the regrowth of native desert plants. The Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), and ferrous iron (Fe2+) index (FI) were used to determine the changes in oil contamination and vegetation cover from 1992 to 2002, and 2013-2020. Subsequently, statistical tests were performed to determine the influence of climatic and soil physical characteristics on changes in hydrocarbon contamination and desert plant behavior. The results showed that hydrocarbon contamination was high at the study sites in the first six years (1992-1997) after contamination, and then decreased in the following years. However, vegetation cover was low in the first six years but significantly increased after 1998, reaching >65%. It was also found that annual plants had the highest distribution rate compared to perennial plants, which mainly depended on the soil type. We concluded that certain annual and perennial plants could successfully grow over tarcrete-contaminated sites, making these sites more suitable for the restoration of native desert plants than hydrocarbon-contaminated sites. We also observed that the succession process of vegetation growth over hydrocarbon-contaminated soils could be associated with vegetation growth on a clean sediment layer covering the oil layer. Additionally, we observed that the remobilization of aeolian sediment over many contaminated sites in Kuwait resulted in the accumulation of organic matter, plant seeds, and dust particles that create layers of nutrient-rich soil for the initial growth of plants.

Total petroleum hydrocarbons and influencing factors in co-composting of rural sewage sludge and organic solid wastes

Co-composting is an efficient strategy for collaborative disposal of multiple organic wastes in rural areas. In this study, we explored the co-composting of rural sewage sludge and other organic solid wastes (corn stalks and kitchen waste), with a focus on the variation of total petroleum hydrocarbons (TPH) during this process. 12% corn-derived biochar was applied in the composting (BC), with no additives applied as the control treatment (CK). The TPH contents of piles after composting ranged from 0.70 to 0.74 mg/g, with overall removal efficiencies of 35.6% and 61.1% for CK and BC, respectively. The results indicate that the addition of 12% biochar increased the rate of TPH degradation and accelerated the degradation process. 16s rDNA high-throughput sequencing was applied to investigate the biodiversity and bacterial community succession during the composting process. Diverse bacterial communities with TPH degradation functions were observed in the composting process, including Acinetobacter, Flavobacterium, Paenibacillus, Pseudomonas, and Bacillus spp. These functional bacteria synergistically degraded TPH, with cooperative behavior dominating during composting. Biochar amendment enhanced the microbial activity and effectively promoted the biodegradation of TPH. The physicochemical properties of the compost piles, including environmental factors (pH and temperature), nutrients (nitrogen, phosphorus, potassium), and humic substances produced in composting (humic acids and fulvic acids), directly and indirectly affected the variation in TPH contents. In conclusion, this work illustrates the variation in TPH content and associated influencing factors during co-composting of rural organic solid wastes, providing valuable guidance toward the further optimization of rural organic waste management.

Consistency of Cuticular Hydrocarbon Mixtures of Five Reticulitermes (Blattodea: Rhinotermitidae) Taxa From Northern California: Similarity Among Colonies and Seasonal Variation

Cuticular hydrocarbon (CHC) mixtures from workers of five distinct CHC phenotypes of Reticulitermes Holmgren 1913 from two locations in northern California were examined from monthly collections taken over a 3-yr period. The objectives of this study were (1) to identify and quantify variations of the CHCs of multiple colonies of each of these phenotypes (= species or subspecies) to demonstrate consistency, (2) to assess the potential of CHC mixtures to separate or identify colonies within each phenotype, and (3) to detect any temporal changes in each of the hydrocarbons in the CHC mixtures. Nonmetric multidimensional scaling of all CHC mixtures of all samples collected at both locations separated the samples into five clearly visible, different groups of CHC phenotypes (taxa or species) of Reticulitermes. The degree of variability of the CHC mixtures among colonies of each phenotype was such that nonmetric multidimensional scaling did not separate or identify colonies. Strong seasonal fluctuations were evident in some of the CHCs of all five phenotypes and were significantly consistent with a sine curve. Maximum proportions of seasonal CHCs within a phenotype occurred in all seasons of the year but occurred mostly in the winter and summer. In general, the CHCs displaying maximum values in the winter were short-chained (C23-C27) methyl-branched alkanes, whereas the CHCs displaying maximum values in the summer were long-chained (C35-C43) methyl-branched alkanes, which likely influences water retention. These consistent chemical fingerprints are probably responsible for inter-phenotype recognition patterns and are thus useful for chemical taxonomy.

Insight on efficiently oriented oxidation of petroleum hydrocarbons by redistribution of oxidant through inactivation of soil organic matter coupled with passivation of manganese minerals

While extensive works focused on the enhancement of the activity of heterogeneous Fenton catalysts, little was paid attention to the inhibition of soil organic matter (SOM) and Mn minerals in soil remediation. Here, the oxidation of petroleum hydrocarbons in soils (S1: 4.28 % SOM, S2: 6.04 % SOM, S3: 10.33 % SOM) with inactivated SOM and passivated Mn oxides regulating by calcium superphosphate (Ca(H₂PO₄)₂) was carried out. Oily sludge pyrolysis residue was used as precursors to prepare an oleophilic iron-supported solid catalyst (Fe-N @ PR). For regulated systems, under the optimal conditions of 1.8 mmol/g H₂O₂ and 0.05 g/g Fe-N @ PR, 72 ∼ 91 % of total petroleum hydrocarbons (TPHs: 15,616.58 mg/kg) were oxidized, which was 38 ∼ 45 % higher than that of control systems. The mechanism of efficient oxidation was proposed that the passivated Mn minerals stabilized H₂O₂ redistributing more H₂O₂ to sustainably produce •OH, and the inactivated SOM improved the relative reactivity of •OH to TPHs. Additionally, the passivation of Mn oxides was mainly related to the binding of H₂PO₄^-, and the inactivation of SOM was realized by Ca²⁺ combing with -OH and C-O-C to form stable complexes. This study brought us a new perspective on soil remediation through passivating Mn minerals and inactivating SOM.

Development of a porous layer-by-layer microsphere with branched aliphatic hydrocarbon porogens

Porous polymer microspheres are employed in biotherapeutics, tissue engineering, and regenerative medicine. Porosity dictates cargo carriage and release that are aligned with the polymer physicochemical properties. These include material tuning, biodegradation, and cargo encapsulation. How uniformity of pore size affects therapeutic delivery remains an area of active investigation. Herein, we characterize six branched aliphatic hydrocarbon-based porogen(s) produced to create pores in single and multilayered microspheres. The porogens are composed of biocompatible polycaprolactone, poly(lactic-co-glycolic acid), and polylactic acid polymers within porous multilayered microspheres. These serve as controlled effective drug and vaccine delivery platforms.

Hydrocarbons removal and microbial community succession in petroleum-contaminated soil under hydrogen peroxide treatment

Chemical oxidation as a pretreatment step coupled with bioremediation for petroleum-contaminated soil may pose serious impacts on indigenous microorganisms and the available nutrients. Petroleum-contaminated soil were treated by hydrogen peroxide (H₂O₂) at initial concentrations of 105 mM (HH), 21 mM (HL), and 105 mM in three equal amounts (HT) without adding any external catalyst. The contents of total petroleum hydrocarbons (TPH) and dissolved nutrients (total organic compounds, nitrogen, and phosphate), and the indigenous bacteria community succession (analyzed by high-throughput sequencing of 16S rDNA) were investigated over 50 days. Compared to the control treatment without H₂O₂ addition, H₂O₂ treatments for the petroleum-contaminated soil significantly promoted the TPH removal especially in the first 4 days and impacted the contents of dissolved nutrients. Both of chemical oxidation and nutrients contributed to microbial community structure changes in alpha diversity. Although the soil microbial community structure had undergone significant changes after different chemical oxidation pretreatments, Firmicutes, Proteobacteria, Gemmatimonadetes, and Actinobacteria were the main bacterial phyla. Compared with adding H₂O₂ at one time, H₂O₂ added in stepwise was beneficial to indigenous bacterial diversity recovery and TPH removal. H₂O₂ oxidation treatments showed a great influence on the microbial community structures in the start-up stage, while recovery time rather than the oxidation treatments presented greater effects on the composition of the microbial community structure with the incubation time extended. Therefore, adding H₂O₂ as pretreatment for petroleum-contaminated soil showed little effect on the structure of soil indigenous microbial community from a long-term scale, and was conducive to the continuous removal of TPH by indigenous microorganisms.

Batch-mode stimulation of hydrocarbons biodegradation in freshwater sediments from historically contaminated Alūksne lake

Historical contamination of freshwater lakes with hydrocarbons (HC) due to anthropogenic activities represents a serious problem worldwide. This study was focused on hydrocarbons-contaminated sediments sampled in Lake Alūksne of glacial origin in Northeast Latvia. The batch experiments were aimed at evaluating the effect of bio-stimulation and bioaugmentation on the biodegradation of hydrocarbons in lake sediments (LS), as well as changes in microbial community structure and metabolic activity. The sediments were sampled from two points of the lake, 4-5 m and 8 m depth, respectively. These samples slightly differed by colour, count of diatoms, microbial respiration intensity and colour intensity of 2,6- dichlorophenolindophenol. Nevertheless, the trend in biodegradation activity was similar for both LS samples. The concentration of HC in LS during the 32-day incubation decreased in average from 465 mg/kg to 165 mg/kg and 117.5 mg/kg in the LS amended with nutrients and nutrients+microbial community, respectively. Different treatment types of LS resulted in differences in microbial respiration and HC-degrading activity. The Shotgun sequencing has revealed the main phyla present in the intact LS being Proteobacteria (48.8%), Actinobacteria (24.4%), Firmicutes (10.4%) and Bacteroidetes (5.0%). Incubation of LS for 32 days resulted in increasing abundance of Proteobacteria from 48.8% in the raw LS to 58-62%, mainly due to the increase of Betaproteobacteria. The functional annotation of gene families revealed that the most abundant gene families were associated with ATP binding, metal ion, magnesium ion, sulfur cluster, zinc ion binding, DNA binding and other essential components for cell functioning. The Shannon biodiversity index of culturable microorganisms in EcoPlates™ ranged from 2.28 to 2.85. The data obtained in this study indicated that the suggested approach is a potent remediation technology for further ex situ scaling up.

A review of the occurrence, distribution, and impact of bitumen seeps on soil and groundwater in parts of southwestern Nigeria

The impact of bitumen components on soil and groundwater resources is of environmental importance. Contaminants' influx into the environment from bitumen components through anthropogenic activities such as exploration, mining, transportation, and usage of bitumen in all its forms have been reported globally. However, gaps exist in the geogenic occurrence of bitumen in the shallow subsurface such as in southwest Nigeria, contaminating the soil and groundwater resources. This review presents in situ bitumen seeps as a source of geogenic soil and groundwater contaminants in southwestern Nigeria. We conducted a systematic review of literatures based on defined selection criteria. We derived information on the state of knowledge about bitumen seep occurrences and distribution in southwestern Nigeria. Also, the processes that exacerbate bitumen contaminants' influx into soil and groundwater were enunciated. At the same time, case examples highlighted areas for possible in situ bitumen contamination studies in Nigeria. The results of this review showed that a multidisciplinary approach has been employed to assess and monitor the contaminants resulting from the various activities involving the exploitation and application of bitumen in Nigeria. These studies emphasize bitumen contaminants as emanating from anthropogenic sources. The results also suggested that bitumen studies have been mainly exploratory to improve the understanding of the economic potential of the hydrocarbon reserve. Also, recent advances in bitumen contaminants studies accounted for the heterogeneous nature of the bitumen. This allows for the optimized categorization of the mechanism and processes undergone by the different bitumen components when released as environmental contaminants. However, a knowledge gap exists in characterizing and understanding the effects of in situ bitumen seeps as a geogenic source of soil and groundwater contamination. This review identifies the possibility of geogenic soil and groundwater contamination by in situ bitumen seeps in the coastal plain sand of the Dahomey basin in southwestern Nigeria. The impact of the bitumen contaminants on the environment was discussed, while methods for accessing the occurrence and distribution of the bitumen contaminants were highlighted.

Genomics for the characterization of the mechanisms of microbial strains in degrading petroleum pollutants

Four petroleum-tolerant bacteria, namely, Pseudomonas hibiscicola, Enterobacter hormaechei, Rhizobium pusense and Pseudomonas japonica were isolated. These strains showed excellent performance in the remediation of petroleum contamination with degradation percentages of 26.13%, 26.47%, 32.27%, and 18.74% for petroleum hydrocarbons, 29.63%, 70.11%, 88.38%, and 67.03% for n-docosane, and 61.00%, 96.36%, 98.00%, and 67.01% for fluorene. Accordingly, the strain of Rhizobium pusense was used to further study its underlying degradation mechanism. N-docosane could be metabolised through the pathway of subterminal oxidation by Rhizobium pusense, while the main pathway for fluorene metabolism is the meta-cleavage. R. pusense contains 10 genes that are involved in the synthetic of biosurfactants and 71 genes that are involved in the metabolism of petroleum hydrocarbons and organic pollutants, such as hydrocarbons, toluene, xylene, ethylbenzene and naphthalene. This study was the first to determine that concerning the metabolism ability and metabolic genes of R. pusense for petroleum pollutant degradation, which is important for understanding the bioremediation mechanism of petroleum pollution.

Using radish (Raphanus lativus L.) germination to establish a benchmark dose for the toxicity of ozonated-petroleum byproducts in soil

The concentration-response relationship between the germination outcome of radish (Raphanus lativus L.) and ozonated petroleum residuals was determined experimentally. The outcomes were used to produce an ecological risk assessment model to predict the extra risk of adverse outcomes based on the concentration of ozonated residuals. A test soil with low organic matter (0.5% w/w) was mixed with raw crude oil, artificially weathered, and treated at three doses of ozone (O₃) gas (5 g, 10 g, and 40 g O₃ per 600 g of soil). Total petroleum hydrocarbons (TPH) and produced dissolved organic carbon (DOC) were measured. TREATMENT categories (control, petroleum, petroleum + 5 g O₃, petroleum + 10 g O₃, and petroleum + 40 g O₃) were then used to create a dilution series using different proportions of the test soil and a commercially available potting mix (∼75% w/w organic matter) to evaluate the effects of background organic matter (b-ORGANIC) in conjunction with TPH and DOC. Multivariable logistic regression was performed on the adverse germination outcome as a function of TPH, DOC, TREATMENT, and b-ORGANIC. The parameters controlling germination were the continuous variable DOC and the categorical variables TREATMENT and b-ORGANIC. Radish germination was strongly harmed by DOC from ozonation, but DOC's ecotoxicity decreased with increasing O₃ dose and the presence of b-ORGANIC beyond 10% (w/w). We used the germination outcome of radish to produce a logistic regression model that computes margins of DOC (± std. error) that create 10%, 25%, and 50% extra risk of adverse germination effects.

Evaluation of the effective factors of unloading and loading goods in ports and the impact on the environment using the MCDM method

Today, the impact of transportation on sustainable development is undeniable. Maritime transport, as one of the important pillars of this industry and due to its advantages such as low cost and large volume of freight, plays a key role in the development of foreign trade. This study uses TOPSIS and DEMATLE methods to evaluate the factors affecting the unloading and loading of goods on the port's environment. The results of TOPSIS method on the main criteria showed that the atmospheric factors' criterion had the highest weight and the port criterion (includes activities that occur in the port) had the lowest weight. In the sub-criteria section, the suitable visibility of the crane operator had the highest rank and the sub-criterion of storage capacity and its (storage) area obtained the lowest rank. Also, the results of DEMATEL method on the cause-and-effect relationship of sub-criteria of unloading and loading of goods showed that coastal transport equipment, unloading and loading equipment, and safety required for unloading goods are influenced higher than other sub-criteria and also the impact of safety required for unloading goods, proper visibility of the crane operator, and the ability of unloading equipment is greater than other sub-criteria. The results of cause-and-effect relationship for sub-criteria of the port environment showed that the impact of sewage, sanitary effluents from the port and ships, and hazardous waste is higher than other sub-criteria and also the impact of petroleum hydrocarbons, sediments, and toxic substances is higher than other sub-criteria.

The Challenges of Characterizing the Zooplankton Community Response Following Simulated Spills of Diluted Bitumen into Boreal Lake Limnocorrals

We attempted to characterize zooplankton community response following spills of the unconventional crude oil, diluted bitumen (dilbit), into 10-m diameter, ~ 100 m³, ~ 1.5-m deep boreal lake limnocorrals, including two controls and seven dilbit treatments ranging from 1.5 to 180 L (1:100,000 to 1:1,000 v/v, dilbit:water). Community composition and abundances were monitored weekly to bi-weekly over three months. Total zooplankton biomass and abundance seemingly collapsed in all limnocorrals, regardless of treatment, though some rotifer species persisted. As a result, it was not possible to determine the impacts of dilbit. We theorize several potential non-oil-related reasons for the sudden community collapse - including elevated zinc levels, fish grazing pressures, and sampling biases - and provide guidance for future work using in-lake enclosures.

Synergistic citric acid-surfactant catalyzed hydrothermal liquefaction of pomelo peel for production of hydrocarbon-rich bio-oil

Citric acid showed good performance of hydrothermal liquefaction (HTL) of biomass waste via promoting the depolymerization of macromolecules. The synergistic effects of citric acid-surfactants/solid catalysts in the low-temperature (200 °C) catalytic hydrothermal liquefaction of pomelo peel (PP) were studied for the first time. It turned out that citric acid-surfactants promoted the conversion of pomelo peel to bio-oil with a higher yield (26.10-67.72 wt%), higher heating value (17.79-24.77 MJ/kg) and energy yield (33.53-114.11 %), while citric acid-solid catalysts were more conducive to the formation of gas and other products. FT-IR and GC-MS analysis testified that citric acid-surfactants increased the selectivity of hydrocarbons from 49.99 % to 74.19 %. Additionally, the chemical functional groups of bio-oil were characterized by ¹H NMR and ¹³C NMR, indicating that the highest aliphatic content of bio-oils was 89.67 %. Moreover, citric acid-surfactant more environmentally friendly for low temperature liquefaction of biomass.

Diesel removal and recovery from heavily diesel-contaminated soil based on three-liquid-phase equilibria of diesel + 2-butyloxyethanol + water

Diesel contamination poses a serious threat to ecosystem and human health. This study proposes a novel method for simultaneous diesel removal and recovery from heavily diesel-contaminated soil by washing based on three-liquid-phase equilibria of diesel+2-butoxyethanol+water. This work covers both theoretical-cum-experimental explorations. For this brand-new ternary three-liquid-phase system (TPS), Ternary-Gibbs and Fish-Shaped phase diagrams were constructed through the phase behavior investigation to provide theoretical support for diesel removal/recovery. As the experiment demonstrated, the removal efficiency was up to 87.5 % for the contaminated soil with diesel content of 226,723 mg/kg, and the recovery rate reached 73.8 %. In addition, the TPS could also be used continuously during the washing process while avoiding solution purification, and the detached diesel would automatically float into the top phase without complicated separation. The mechanism of diesel removal was determined as the surface "stripping" effect based on ultralow interfacial tension, and the enhanced process involved "stripping+dissolution". The treated soil contained almost negligible organic solvent residue and was therefore appropriate for plant cultivation. The recovered diesel exhibited less variation from commercial diesel in composition and properties, possessing a higher potential for reuse. Moreover, this study also provided key insights into the residual mechanisms of recalcitrant hydrocarbons in the soil.

Geographical Variation of Cuticular Hydrocarbon Profiles of Adult Flies and Empty Puparia Amongst Three Populations of Calliphora vicina (Diptera: Calliphoridae)

Blowflies (Diptera: Calliphoridae) are of great importance in forensic entomology and in determining the minimum post-mortem interval, as they may be the first group of insects to colonize decomposing remains. Reliable species identification is an essential prerequisite. Classically, morphological characters or DNA sequences are used for this purpose. However, depending on the species and the condition of the specimen, this can be difficult, e.g., in the case of empty fly puparia. Recent studies have shown that cuticular hydrocarbon (CHC) profiles are species-specific in necrophagous taxa and represent another promising tool for identification. However, the population-specific variability of these substances as a function of e.g., local climatic parameters has not yet been sufficiently investigated. The aim of this study was to determine the geographical variation of CHC profiles of the blowfly Calliphora vicina (Robineau-Desvoidy, 1830) depending on different countries of origin. Flies were reared in the United Kingdom, Germany, and Turkey in common garden experiments under ambient conditions. CHC profiles of the resulting adult flies and their empty puparia were analyzed using gas chromatography-mass spectrometry. Data were visualized by principal component analysis and clustered by population. The populations of the United Kingdom and Germany, both having similar climates and being geographically close to each other, showed greater similarities in CHC profiles. However, the CHC profile of the Turkish population, whose climate is significantly different from the other two populations, was very different. Our study confirms the high potential of CHC analysis in forensic entomology but highlights the need to investigate geographical variability in chemical profiles.

Treatment of a synthetic decanted oily seawater in a pilot-scale hollow fiber membrane filtration process: Experimental investigation

This study investigates the performance of a pilot-scale submerged hollow fiber (HF) ultrafiltration (UF) polytetrafluoroethylene (PTFE) membrane filtration system for the treatment of two different types of oily seawater (i.e., seawater contaminated with light and heavy crude oil). The effects of membrane flux and aeration flow rate on membrane performance and the removal efficiency of different fractions of hydrocarbon, including polycyclic aromatic hydrocarbons (PAHs) were examined. The results for both heavy and light crude oil contaminated wastewater reveal that total petroleum hydrocarbon (TPH) removal efficiency of more than 91% was achieved. This research paper determined the optimal operational parameters for an HF membrane filtration system to obtain a good TPH removal efficiency. This system can easily be upscaled and placed on a barge to treat oily wastewater generated from marine oil spills, which can significantly improve the oil spill response capacity.

Soil washing of total petroleum and polycyclic aromatic hydrocarbons from crude oil-contaminated ultisol using aqueous extracts of waterleaf

Ultisols are acidic soils found in humid climates and are known for poor fertility. Crude oil impacted ultisols, therefore, require special treatment measures to account for nutrient loss during treatment. In this paper, we report the utilization of a food waste, aqueous extracts of waterleaf (Talinum triangulare), as a plant-derived surfactant to wash simulated crude oil-contaminated soils. The soils before and after washing were monitored for microbial loads, nutrient parameters, physicochemical characteristics, total petroleum hydrocarbons (TPHs) and polycyclic aromatic hydrocarbons (PAHs). Although higher amounts of PAHs (up to 100%) were removed compared to TPHs (up to 95.7%), the results revealed that the efficiency of the waterleaf extracts was comparable to that of a commercial surfactant sodium dodecyl sulphate. However, soils washed with the waterleaf extracts retained some significant amounts of nutrients and favourable pH moderation. In both surfactants, soil microbial loads reduced significantly. Overall, the aqueous waterleaf extracts showed potential as ecofriendly surfactants and nutrients retainer during soil washing of contaminated ultisols.

The effect of biodiesel production method on its combustion behavior in an agricultural tractor engine

In this study, biodiesel fuel was produced from waste cooking oil (WCO) using a heterogeneous catalyst under microwave (MB) and conventional (CB) heating, and fueled in an agricultural tractor engine to evaluate the engine performance as well as emissions. The biodiesels presented different fatty acid methyl ester (FAME) profiles where MB had lower unsaturated FAME chains. Beyond the transesterification reaction time, the energy consumed for MB biodiesel production diminished by around eight times compared to that required for CB production. The engine results confirmed the positive influence of blending net diesel fuel with biodiesel for enhancing the engine performance and reducing the emissions. More than 20% increment in the engine power and torque was detected at all engine loads (the engine speed was adjusted at 1500 rpm). The hydrocarbon (HC), carbon monoxide (CO), and smoke opacity (SO) indicated significant reductions compared to when net diesel fuel was used. According to statistical analysis, CB25 and MB25 fuels presented a suitable combination as fuel where MB25 provided better engine performance, lower HC and SO emissions, with CO emissions reaching the minimum amount by CB fuels.

Petroleum refinery effluent contribution to chemical mixture toxic pressure in the environment

Petroleum refinery effluents (PRE) are wastewaters from industries associated with oil refining. Within Europe, PREs are regulated through local discharge permits and receive substantial treatment before emission. After treatment, PREs can still contain low levels of various pollutants potentially toxic to organisms. Earlier work, including whole-effluent toxicity assessments, has shown that the toxicity of permitted PREs is often limited. However, the extent to which PREs contribute to chemical pollution already present in the receiving environment is unknown. Therefore, our study aimed to assess the contribution of PREs to mixture toxic pressure in the environment, using the multi-substance potentially affected fraction of species (msPAF) as an indicator. Based on measured chemical concentrations, compiled species sensitivity distributions (SSD) and a mechanistic solubility model, msPAF levels were estimated for undiluted effluents at discharge points and diluted effluents downstream in receiving waters. Median msPAF-chronic and msPAF-acute levels of PREs at discharge points were 74% (P50) and 40% (P95), respectively. The calculated msPAF levels were reduced substantially to <5% downstream for most effluents (82%), indicating low to negligible toxicity of PREs in receiving environments beyond the initial mixing zone. Regardless of differences in endpoints and locations, hydrocarbons (mainly total petroleum hydrocarbons) and inorganics (mainly ammonia) explained at least 85% of the mixture toxic pressure. The msPAF levels of PREs were on average 2.5-4.5 orders of magnitude lower than msPAF levels derived from background pollution levels, suggesting that PREs were minor contributors to the toxic pressure in the environment. This study presents a generic methodology for quantifying the potential toxic pressure of PREs in the environment, identifying hotspots where more effective wastewater treatment could be needed. We explicitly discuss the uncertainties for further refinement and development of the method.

Increased barium levels in recent marine sediments from the Norwegian and Barents Seas suggest impact of hydrocarbon drilling and production

Barium (Ba) in recent marine sediments can originate from natural and anthropogenic sources including discharges from the oil and gas industry. In this study, we use data from the Norwegian and Barents Seas to assess whether Ba in recent marine sediments has increased due to these discharges. To account for Ba in detrital material, we normalise all samples with respect to aluminosilicate by calculating an enrichment factor. We use statistical modelling to control for parameters related to sedimentation. We present results that suggest increased Ba levels in recent sediments that coincide with the timing of hydrocarbon drilling and production. This is supported by geographical differences on a large scale that relate to proximity to hydrocarbon drilling and production. Among 243 sampling stations, we identify 73 locations exhibiting enrichment of Ba in the upper 6 of sediment. At these locations, Ba is 1.55 to 3.55 times higher than the levels that can be expected from the shale average when Ba in detrital matter is accounted for. Excess Ba is reported in sediment surface samples in areas important to fisheries like the Lofoten area and the western Barents Sea.

Modeling demonstrates minimal ecological risks of cuttings discharges associated to oil and gas drilling with deep water wells

To assess the impacts of drill cutting discharges in the Gulf of Mexico, a particle dispersion modeling study was conducted on hypothetical drilling scenarios. The goal was to assess cumulative seabed deposition, and potential hydrocarbon loading from non-aqueous drilling fluids (NADF). Cuttings drilled with NADF showed to have minimal impact on local fauna at the deep-water well simulated. A hypothetical drill site was modeled under 3 different seasonally representative met-ocean conditions. The site is located approximately 260 km from the coast in water roughly 3500 meters (m) deep. Cumulative deposition was assessed for all materials released, whereas hydrocarbon loading was assessed based on the potential for NADF fluids to be retained on cuttings. Smothering effects on the benthic community are not anticipated. Hydrocarbon deposition was also very limited, ≤165 ppm of TPH. Overall, the cuttings drilled with NADF are predicted to have minimal impact on local fauna.

Exploring the effect on the environment of encapsulated micro- and nano-plastics into asphalt mastics for road pavement

A new environmental problem is represented by the huge transformation of plastic waste released into the environment into small fragments, the so called micro- and nano-plastics, due to atmospheric phenomena. The smaller the size of the plastic fragments, the more their spreading into environmental compartments. The aim of this study is to test encapsulation into asphalt mastics of waste plastic material (WPM) as sustainable strategy to obtain road flexible pavements and to evaluate the potential release in water of micro and nano plastics. A new mastic mixing method was developed to blend the WPM with the bitumen contained into a bitumen emulsion (BE60/40) by adopting low mixing temperatures. Three different WPM contents, equal to 5, 10 and 20% by the weight of the bitumen contained in the BE60/40, were adopted to produce the mastics; the mastics' rheological properties, obtained by frequency sweep and multiple stress creep and recovery tests, were compared to those of a traditional asphalt mastic containing limestone filler. The aging of asphalt mastics was analyzed by soaking them in water and gradually lowering and raising temperature between -10 and 60 °C at predefined intervals. The addition of WPM improved greatly the asphalt mastic performance; in particular, for a WPM content of 10%, the rheological response in terms of stiffness remained unchanged after the mastic underwent thermal excursions in water. Encapsulation of micro and nano plastics into mastics reduced of more than 99% their potential water release.

Tracing the impact and recovery trajectory of oil spill affected tropical rocky intertidal macrobenthic communities using the BOPA index

A yearlong study was conducted to assess the impact of an oil spill on macrobenthos of rocky intertidal zone of Uran, India and its recovery processes, by comparing impacted site with a reference. Immediate acute effects observed were elevated sediment hydrocarbons, absence of macroalgae and amphipods, mass mortality of macrofauna and dominance of the opportunistic nereid, Namalycastis senegalensis. As the hydrocarbons reduced at the impacted site by ~50 % within three months, gradual re-appearance of macroalgae and re-colonization of amphipods (51.4 %) and sensitive polychaetes (7 %) indicated that the recovery was well underway. The amphipod, Allomelita pellucida proved to be a potential indicator of oil contamination. BOPA correlated with sediment hydrocarbons and performed effectively as the extant macrobenthic communities had sufficient representation of Polychaeta and Amphipoda. Notwithstanding the distinct initial impacts of the oil spill, comparable macrobenthic assemblages comprised of sensitive species at both sites after a year confirmed complete recovery.

Relation of blood lead levels and lead in gasoline: an updated systematic review

BACKGROUND

Millions of tons of lead were added to gasoline worldwide beginning in 1922, and leaded gasoline has been a major source of population lead exposure. In 1960s, lead began to be removed from automotive gasoline. Removal was completed in 2021.

OBJECTIVES

To determine whether removal of lead from automotive gasoline is associated with declines in population mean blood lead levels (BPb).

METHODS

We examined published studies that reported population blood leaded levels for two or more years, and we calculated average concentrations of lead in gasoline corresponding to the years and locations of the blood lead level measurements.

RESULTS

Removal of lead from gasoline is associated with declines in BPb in all countries examined. In some countries, BPb continues to fall after lead has been eliminated from gasoline. Following elimination of lead from gasoline, BPb less than 1 μg/dL have been observed in several European and North American countries, and BPb less than 3 μg/dL have been documented in several studies from South America.

DISCUSSION

There remain many countries for which no multi-year studies of populations BPb have been identified, including all of Central America, high population countries including Pakistan and Indonesia, and major lead producers including Australia and Russia.

CONCLUSION

Removal of lead from gasoline has been a public health success. Elimination of lead from gasoline has enabled many countries to achieve population mean BPb levels of 1 μg/dL or lower. These actions have saved lives, increased children's intelligence and created great economic benefit in countries worldwide.

Catalytic pyrolysis of high-density polyethylene over nickel-waste chicken eggshell/HZSM-5

The main objective of the current work is to investigate the effect of nickel-waste chicken eggshell modified Hydrogen exchanged Zeolite Socony Mobil-5 (Ni-WCE/HZSM-5) on pyrolysis of high-density polyethylene (HDPE). Ni-WCE/HZSM-5 was synthesized via the impregnation incipient wetness (IWI) method with Ni and WCE mass loading of 4 and 12 wt% respectively. HZSM-5, CaO, WCE, WCE/HZSM-5, and Ni/HZSM-5 were prepared for comparison purposes with Ni-WCE/HZSM-5. All the synthesized catalysts were characterized for phase analysis, metal loading, surface morphology, and textural properties. The impregnation of nickel and WCE had significantly affected the original framework of HZSM-5, where the crystallinity percentage and average crystal size of HZSM-5 dropped to 44.97% and increased to 47.90 nm respectively. The surface morphology of HZSM-5 has drastically changed from a cubic-like shape into a spider web-like surface after the impregnation of WCE. The BET surface area of HZSM-5 has been lowered due to the impregnation of nickel and WCE, but the total pore volume has increased greatly from 0.2291 cm³/g to 0.2621 cm³/g. The catalyst performance was investigated in the pyrolysis of HDPE via a fixed bed reactor and the pyrolysis oil was further analysed to evaluate the distribution of C₆ to C₉> hydrocarbons. Among the tested catalytic samples, the highest pyrolysis oil yield was achieved by WCE (80%) followed by CaO (78%), WCE/HZSM-5 (63%), HZSM-5 (61%), Ni/HZSM-5 (44%) and Ni-WCE/HZSM-5 (50%). For hydrocarbon distribution in pyrolysis oil, the Ni/HZSM-5 produced the highest of total C₆ and C₇ hydrocarbons at 12% and 27% respectively followed by WCE/HZSM-5 (4% and 20%), non-catalytic (5% and 13%), Ni-WCE/HZSM-5 (0% and 15%), WCE (0% and 10%), HZSM-5 (0% and 6%) and CaO (0% and 0%).

Comparative toxicological assessment of three soils polluted with different levels of hydrocarbons and heavy metals using in vitro and in vivo approaches

The biological effects induced by the pollutants present in soils, together with the chemical and physical characterizations, are good indicators to provide a general overview of their quality. However, the existence of studies where the toxicity associated to soils contaminated with mixtures of pollutants applying both in vitro and in vivo models are scarce. In this work, three soils (namely, Soil 001, Soil 002 and Soil 013) polluted with different concentrations of hydrocarbons and heavy metals were evaluated using different organisms representative of human (HepG2 human cell line) and environmental exposure (the yeast Saccharomyces cerevisiae, the Gram-negative bacterium Pseudomonas putida and, for the in vivo evaluation, the annelid Enchytraeus crypticus). In vitro assays showed that the soluble fraction of the Soil 001, which presented the highest levels of heavy metals, represented a great impact in the viability of the HepG2 cells and S. cerevisiae, while organic extracts from Soils 002 and 013 caused a slight decrease in the viability of HepG2 cells. In addition, in vivo experiments showed that Soils 001 and 013 affected the survival and the reproduction of E. crypticus. Altogether, these results provide a general overview of the potential hazards associated to three specific contaminated sites in a variety of organisms, showing how different concentrations of similar pollutants affect them, and highlights the relevance of testing both organic and soluble extracts when in vitro safety assays of soils are performed.

Fast Pyrolysis of Cellulose and the Effect of a Catalyst on Product Distribution

Fast pyrolysis of microcrystalline cellulose (MC) was carried out by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The effects of temperature, time, and a catalyst on the distribution of the pyrolysis products were analyzed. The reaction temperature and time can significantly affect the types and yields of compounds produced by cellulose pyrolysis. A pyrolysis temperature of 500-600 °C and pyrolysis time of 20 s optimized the yield of volatile liquid in the pyrolysis products of cellulose. In all catalytic experiments, the relative contents of alcohols (1.97%), acids (2.32%), and esters (4.52%) were highest when K₂SO₄ was used as a catalyst. HZSM-5 promoted the production of carbohydrates (92.35%) and hydrocarbons (2.20%), while it inhibited the production of aldehydes (0.30%) and ketones (1.80%). MCM-41 had an obvious catalytic effect on cellulose, increasing the contents of aldehydes (41.58%), ketones (24.51%), phenols (1.82%), furans (8.90%), and N-compounds (12.40%) and decreasing those of carbohydrates (5.38%) and alcohols (0%).

Clogging and Unclogging of Hydrocarbon-Contaminated Nanochannels

The recent advantages of the fabrication of artificial nanochannels enabled new research on the molecular transport, permeance, and selectivity of various gases and molecules. However, the physisorption/chemisorption of the unwanted molecules (usually hydrocarbons) inside nanochannels results in the alteration of the functionality of the nanochannels. We investigated contamination due to hydrocarbon molecules, nanochannels made of graphene, hexagonal boron nitride, BC₂N, and molybdenum disulfide using molecular dynamics simulations. We found that for a certain size of nanochannel (i.e., h = 0.7 nm), as a result of the anomalous hydrophilic nature of nanochannels made of graphene, the hydrocarbons are fully adsorbed in the nanochannel, giving rise to full uptake. An increasing temperature plays an important role in unclogging, while pressure does not have a significant role. The results of our pioneering work contribute to a better understanding and highlight the important factors in alleviating the contamination and unclogging of nanochannels, which are in good agreement with the results of recent experiments.

Highly Efficient Treatment of Oily Sludge by a Novel High-Speed Stirring Method at Room Temperature

Oily sludge is one of the main hazardous wastes which seriously endangers the ecological environment and human health. In this paper, in order to effectively treat oily sludge, a novel high-speed stirring (HSS) method was proposed to clean oily sludge, and the main parameters affecting the residual oil rate of oily sludge were studied experimentally. Firstly, the cleaning time and stirring speed were optimized in the one-stage HSS cleaning, and then the optimal cleaning time of two-stage HSS cleaning was determined by the response surface method. The results suggested that the oil can be efficiently separated by high-speed stirring at room temperature, and that the two-stage cleaning with a circular-hole outlet (Rotor-C) followed by a vertical hole-outlet (Rotor-V) presented the best effect. The optimal stirring speed was 6000 r/min, and the optimal cleaning times of the two-stage cleaning were 7 min and 8 min, respectively. After cleaning, the residual oil rate of the treated oily sludge was 1.65%, and the removal rate of the petroleum hydrocarbons was 84.3%.

An updated comprehensive IVOC emission inventory for mobile sources in China

Intermediate volatility organic compounds (IVOCs) from mobile sources contribute significantly to secondary organic aerosol (SOA) formation. However, the assessments of IVOC emissions remain considerably uncertain due to the lack of localized measured data and detailed emission source classifications. This study established a comprehensive database of IVOC emission factors (EFs) for mobile sources based on the diversified measured EFs and correlations with hydrocarbons. The provincial-level IVOC emission inventories over China were further established by integrating activity data of various mobile sources. The national mobile source IVOC emissions were 507.5 Gg in 2017. The IVOC emissions of on-road and non-road mobile sources were roughly the same. Trucks and non-road construction machineries were the major contributors to IVOC emissions, accounting for >66 % of the total. The IVOC emission characteristics and spatial distributions from various mobile sources varied significantly with different types and usages. The IVOC emission inventories with detailed classifications can be used to evaluate emission control policies for mobile sources. Incorporating localized measured data would be beneficial for a better understanding for the atmospheric impacts of mobile source IVOC emissions.

Analysis of sleep in individual Drosophila melanogaster reveals a self-regulatory role for cuticular hydrocarbons pheromones

It is well established that pheromones are used by insects to transmit information between individuals. However, research has revealed that individual insects can be both the sender and the receiver of some pheromonal signals. It is therefore interesting to consider whether the pheromonal state of an individual insect can exert an effect on itself. In this study, we monitored the sleep activity of single flies exhibiting a mutation that leads to pheromonal deficiency and found that cuticular hydrocarbons (CHs) exerted self-regulatory effects on the amount of sleep experienced by these flies. To identify the physiological significance of this mechanism, we compared the amounts of sleep in individual young flies and individual old flies (flies are known to sleep less as they get older) and compared this data with young and old flies exhibiting mutations that lead to CH reception defects. The differences in the amount of sleep experienced by young and old mutant flies were significantly lower than those of the control flies. Our data show that hydrocarbon signals produced by the cuticle in Drosophila can be self-perceived and regulate the amount of sleep acquired in a maturation-dependent manner.

Bioremediation of hydrocarbon contaminated soil using local organic materials and earthworms

Bioremediation technologies have demonstrated significant success on biological quality recovery of hydrocarbon contaminated soils, employing techniques among which composting and vermiremediation stand out. The aim of this study was to evaluate the efficiency of these processes to remediate diesel-contaminated soil, employing local organic materials and earthworms. During the initial composting stage (75 days), the substrate was made up using contaminated soil, lombricompost, rice hulls and wheat stubbles (60:20:15:5% w/w). Diesel concentration in the contaminated substrate was about 5 g kg^-1, equivalent to a Total Petroleum Hidrocarbons (TPH) experimental concentration of 3425 ± 50 mg kg^-1. During the later vermiremediation stage (60 days), the earthworm species Eisenia fetida and Amynthas morrisi were evaluated for their hydrocarbon degradation capacity. Physicochemical and biological assays were measured at different times of each stage and ecotoxicity assays were performed at the end of the experiments. TPH concentration reduced 10.91% after composting and from 45.2 to 60.81% in the different treatments after vermiremediation. Compared with TPH degradation in the treatment without earthworms (16.05%), results indicate that earthworms, along with indigenous microorganisms, accelerate the remediation process. Vermiremediation treatments did not present phytotoxicity and reflected high substrate maturity values (>80% Germination Index) although toxic effects were observed due to E. fetida and A morrisi exposure to diesel. Vermiremediation was an efficient technology for the recovery of substrate biological quality after diesel contamination in a short period. The addition of organic materials and suitable food sources aided earthworm subsistence, promoted the decontamination process and improved the substrate quality for future productive applications.

Diclidophora merlangi (Kuhn, 1829) Krøyer, 1838 (Monogenea: Diclidophoridae) as an indicator of hydrocarbon pollution in the North Sea

This study presents the results of analyses of data on infections of 2646 whiting Merlangius merlangus with the monogenean Diclidophora merlangi. All fish were caught in the North Sea and off the north coast of Scotland in 1990, 1993 and 1995. The aims were to analyse these data in relation to the locations of whiting sampling stations and oil installations active at that time, and to evaluate the results in terms of D. merlangi as an indicator of hydrocarbon pollution. Mean abundance of D. merlangi increased significantly with increasing proximity to the nearest oil field, with an accelerated rate of increase within approximately 2 km of the oil field. Age of oil field and whiting length showed no significant effect on parasite abundance, but there was a small difference between years. The results support those of previous studies in demonstrating the value of monogeneans as indicators of hydrocarbon pollution.

Effective bioremediation of soil from the Burgan oil field (Kuwait) using compost: A comprehensive hydrocarbon and DNA fingerprinting study

An innovative combination of metagenomic profiling of microbial communities and GC-MS & Pyrolysis-GC-MS fingerprinting methods were used to assess the biodegradation of contaminated soil from the Burgan oil field in Kuwait. The soil was treated with (sludge) compost in microcosms to evaluate the feasibility of this material for bioremediation purposes. The most favourable trial showed a > 80% decrease in TPH, thereby indicating strong potential for full-scale application using a cost-effective technology and thus in line with the principles of the circular economy. The microbial study showed that compost addition enhanced the organic matter and nutrient content of the soil. However, the microorganisms in the compost did not seem to play a relevant role in bioremediation, meaning that compost amendments serve as a biostimulation rather than a bioaugmentation approach. The chemical study of the distinct oil fractions revealed rapidly biodegraded compounds (alkanes, alkyl-aromatics, etc.) and others that were much more refractory (hopanes, benzohopanes, etc.). Of note, although heavy fractions are usually considered recalcitrant to biodegradation, we observed incipient degradation of the asphaltene fraction by means of double-shot thermodesorption and pyrolysis. Finally, chemical fingerprinting also revealed that the treated soil contained some of the compounds found in the compost, such as coprostanol, cholesterol, and plant sterols. This observation would support the use of these compounds as proxies to monitor the effects of compost and to adjust dosages in real-scale bioremediation treatments.

Correlation of soil microbiome with crude oil contamination drives detection of hydrocarbon degrading genes which are independent to quantity and type of contaminants

The impacts of crude oil contamination on soil microbial populations were explored in seven different polluted areas near oil and gas drilling sites and refineries of Assam, India. Using high-throughput sequencing techniques, the functional genes and metabolic pathways involved in the bioconversion of crude oil contaminants by the indigenous microbial community were explored. Total petroleum hydrocarbon (TPH) concentrations in soil samples ranged from 1109.47 to 75,725.33 mg/kg, while total polyaromatic hydrocarbon (PAH) concentrations ranged from 0.780 to 560.05 mg/kg. Pyrene, benzo[a]anthracene, naphthalene, phenanthrene, and anthracene had greater quantities than the maximum permitted limits, suggesting a greater ecological risk, in comparison to other polyaromatic hydrocarbons. According to the metagenomic data analysis, the bacterial phyla Proteobacteria, Actinobacteria, Acidobacteria, and Bacteroides were the most prevalent among all polluted areas. The most prominent hydrocarbon degraders in the contaminated sites included Burkholderia, Mycobacterium, Polaromonas, and Pseudomonas. However, the kinds of pollutants and their concentrations did not correlate with the abundances of respective degrading genes for all polluted locations, as some of the sites with little to low PAH contamination had significant abundances of corresponding functional genes for degradation. Thus, the findings of this study imply that the microbiome of hydrocarbon-contaminated areas, which are biologically involved in the degradation process, has various genes, operons and catabolic pathways that are independent of the presence of a specific kind of contaminant.

Simulation on oily contamination removal by ozone using molecular dynamics

Ozone (O₃) is characteristic of high oxidative activity. It displays a high potential value in sterilization and decontamination. Although O₃ has been widely investigated for its efficiency and environmentally friendly effectiveness, the fundamental issue regarding the complicated microscopic interaction mechanism between O₃ and contaminant molecules remains largely unaddressed. We addressed this knowledge gap through molecular dynamics (MD) simulation at the molecular scale. Results indicated that five representative hydrocarbon molecules (n-hexadecane, phytane, terpane, naphthalin and acenaphthylene) on a rough silica (SiO₂) surface were almost removed after about 300 ps simulation. And the aromatic molecules were easier to be removed than aliphatic ones. The hydroxyl oxidation reaction was demonstrated as a predominant mechanism. As the large dose of O₃ was supplied by atmospheric air dielectric barrier discharge (DBD) plasma, this work provided an important theoretical reference for better using plasma technology for oily contaminant removal.

Elevated CO2 and biochar differentially affect plant C:N:P stoichiometry and soil microbiota in the rhizosphere of white lupin (Lupinus albus L.)

Biochar application is a potent climate change mitigation strategy in agroecosystems. However, little is known about the interactive effects of elevated CO₂ (eCO₂) and biochar on plant nutrient uptake and soil microbial processes. A pot experiment was conducted to investigate the effects of eCO₂ and biochar addition on plant C:N:P stoichiometry and rhizobacterial community for better management of nutrient balance and use efficiency in a future climate scenario. White lupin (Lupinus albus L.) was grown for 30 days in topsoil and subsoil with or without 2% corn-stubble biochar under ambient CO₂ (aCO₂: 390 ppm) or eCO₂ (550 ppm). Elevated CO₂ increased, but biochar decreased, plant biomass and shoot N and P uptake, with no interactions in either soil layer. Elevated CO₂ decreased shoot N concentration by 16% and biochar decreased shoot P concentration by 11%. As a result, eCO₂ increased shoot C:N ratio by 20% and decreased the N:P ratio by 11%. Biochar decreased shoot C:N ratio by 8% in the subsoil under eCO₂. However, biochar increased shoot C:P ratio by an average of 13% and N:P ratio by 23% in the subsoil. Moreover, plants grown in the subsoil showed lower shoot N (35%) and P (70%) uptake compared to the topsoil. The results indicate that N and P are the more limiting factors that regulate plant growth under eCO₂ and biochar application, respectively. Elevated CO₂ and biochar oppositely affected dominant rhizobacterial community composition, with the eCO₂ effect being greater. The microbiota in the subsoil held a greater diversity of contrasting species than the topsoil, which were associated with nutrient cycling, hydrocarbon degradation and plant productivity. These results enrich our understanding of potential soil nutrient cycling and plant nutrient balance in future agroecosystems.

Comparing simulated shallow subsurface spills of diluted bitumen and conventional crude oil

Increased oil production in Canada has resulted in proposals to extend or develop new oil pipelines. Many of these proposals have been met by concerns from the public over potential environmental impacts related to construction and the potential for oil spills to negatively affect groundwater quality. Crude oil sourced from the Alberta oil sands represents a significant proportion of this increase in production. This crude oil is produced as bitumen, which is subsequently diluted with light hydrocarbons to lower viscosity to allow for pipeline transport producing diluted bitumen. In this study, we pumped water through tanks filled with sand to simulate groundwater flow. Tanks were injected with either conventional crude or diluted bitumen to simulate a crude oil spill from a pipeline rupture occurring below the water table representing a pipeline river crossing scenario. Water samples were collected from the downstream end of the tanks throughout the experiment period (∼two months). Compared to water quality guidelines, effluent waters from both conventional crude and diluted bitumen tanks contained elevated concentrations of dissolved organic compounds, particularly benzene, ethylbenzene, toluene and xylenes (BTEX). The effluent from each tank had similar concentrations of benzene, whereas discharge water from conventional crude tanks contained higher concentrations of ethylbenzene, toluene and xylenes. In both tanks, and as expected, the BTEX concentrations appeared to be proportional to those determined in their injected crude oils. The measured dissolved concentrations of benzene, ethylbenzene and toluene are lower than predicted which is attributed largely due to dilution along the flow path. In addition to organic constituents, effluent sampled from the diluted bitumen tank contained some metals (Co, Cr, Fe and V) which measured constituents of the oil.

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.

The co-application of biochar with bioremediation for the removal of petroleum hydrocarbons from contaminated soil

Soil pollution from petroleum hydrocarbon is a global environmental problem that could contribute to the non-actualisation of the United Nations Sustainable Development Goals. Several techniques have been used to remediate petroleum hydrocarbon-contaminated soils; however, there are technical and economical limitations to existing methods. As such, the development of new approaches and the improvement of existing techniques are imperative. Biochar, a low-cost carbonaceous product of the thermal decomposition of waste biomass has gained relevance in soil remediation. Biochar has been applied to remediate hydrocarbon-contaminated soils, with positive and negative results reported. Consequently, attempts have been made to improve the performance of biochar in the hydrocarbon-based remediation process through the co-application of biochar with other bioremediation techniques as well as modifying biochar properties before use. Despite the progress made in this domain, there is a lack of a detailed single review consolidating the critical findings, new developments, and challenges in biochar-based remediation of petroleum hydrocarbon-contaminated soil. This review assessed the potential of biochar co-application with other well-known bioremediation techniques such as bioaugmentation, phytoremediation, and biostimulation. Additionally, the benefits of modification in enhancing biochar suitability for bioremediation were examined. It was concluded that biochar co-application generally resulted in higher hydrocarbon removal than sole biochar treatment, with up to a 4-fold higher removal observed in some cases. However, most of the biochar co-applied treatments did not result in hydrocarbon removal that was greater than the additive effects of individual treatment. Overall, compared to their complementary treatments, biochar co-application with bioaugmentation was more beneficial in hydrocarbon removal than biochar co-application with either phytoremediation or biostimulation. Future studies should integrate the ecotoxicological and cost implications of biochar co-application for a viable remediation process. Lastly, improving the synergistic interactions of co-treatment on hydrocarbon removal is critical to capturing the full potential of biochar-based remediation.

Conversion of acetone and mixed ketones to hydrocarbons using HZSM-5 catalyst in the carboxylate platform

In this study, two different feeds were treated to produce hydrocarbons: (1) reagent-grade acetone, and (2) mixed ketones obtained from lignocellulosic biomass via the carboxylate platform. Acetone and mixed ketones underwent catalytic self-condensation over HZSM-5. For acetone, HZSM-5(80) was used, and the experiments were conducted in two sets: (1) vary temperature (305-415°C) at P = 101 kPa (abs) and weight hourly space velocity (WHSV) = 1.3 h-1; (2) vary WHSV (1.3-7.9 h-1) at T = 350 and 415°C, and P = 101 kPa (abs). For acetone over HZSM-5(280), the experiments were conducted in two sets: (1) vary WHSV (1.3-6.5 h-1) at T = 415°C, and P = 101 kPa (abs); and (2) vary WHSV (1.3-11.8 h-1) at P = 790 kPa (abs) and T = 415°C. For mixed ketones, HZSM-5(280) was used at WHSV = 1.9 h-1, T = 430-590°C, and P = 101 kPa (abs). For acetone at higher temperatures, the conversion was 100% and the liquid products were aromatics centered on C8. At low temperatures, conversion was less and the carbon liquid distribution was centered on C9 (mainly mesitylene). For mixed ketones, catalyst deactivation was higher causing product concentrations to change over time, and the highest conversion reached was 40%.

The acute toxicity of bitumen-influenced groundwaters from the oil sands region to aquatic organisms

The extraction of surface mined bitumen from oil sands deposits in northern Alberta, Canada produces large quantities of liquid tailings waste, termed oil sands process-affected water (OSPW), which are stored in large tailings ponds. OSPW-derived chemicals from several tailings ponds migrating past containment structures and through groundwater systems pose a concern for surface water contamination. The present study investigated the toxicity of groundwater from near-field sites adjacent to a tailings pond with OPSW influence and far-field sites with only natural oil sands bitumen influence. The acute toxicity of unfractionated groundwater and isolated organic fractions was assessed using a suite of aquatic organisms (Pimephales promelas, Oryzias latipes, Daphnia magna, Hyalella azteca, Lampsilis spp., Ceriodaphnia dubia, Hexagenia spp., and Vibrio fischeri). Assessment of unfractionated groundwater demonstrated toxicity towards all invertebrates in at least one far-field sample, with both near-field and far-field samples with bitumen influence toxic towards P. promelas, while no toxicity was observed for O. latipes. When assessing the unfractionated groundwater and isolated organic fractions from near-field and far-field groundwater sites, P. promelas and H. azteca were the most sensitive to organic components, while D. magna and L. cardium were most sensitive to the inorganic components. Groundwater containing appreciable amounts of dissolved organics exhibited similar toxicities to sensitive species regardless of an OSPW or natural bitumen source. The lack of a clear distinction in relative acute toxicities between near-field and far-field samples indicates that the water-soluble chemicals associated with bitumen are acutely toxic to several aquatic organisms. This result, combined with the similarities in chemical profiles between bitumen-influenced groundwater originating from OSPW and/or natural sources, suggests that the industrial bitumen extraction processes corresponding to the tailings pond in this study are not contributing unique toxic substances to groundwater, relative to natural bitumen compounds present in groundwater flow systems.

Bio-grafted silica to make an asphalt road a sink for reactive environmental pollutants

Asphalt-surfaced areas such as roads have been reported as major non-combustion sources of reactive organic compounds in urban areas. Emission of latter compounds from asphalt is exacerbated due to exposure to sunlight and high temperature, contributing to negative human and environmental health outcomes. Furthermore, loss of asphalt components over time is linked to bitumen's aging that reduces service life of roads. Here, we introduce a designed bio-grafted-silica nano-filler derived from wood pellet as a sink for latter volatile compounds in an asphalt mixture. Molecular modeling calculations showed the remarkable adsorptive activity of the bio-grafted silica for trapping select asphalt volatiles, especially for the sulfur-containing aromatics and the oxygen-containing aromatics. Laboratory experiment revealed that the bitumen modified with bio-grafted silica exhibited up to 23% lower signs of aging. Thermogravimetric analysis proved that the modified bitumen exhibited a 16% reduction in mass loss compared to neat bitumen. Dynamic vapor sorption analysis also showed bio-grafted silica adsorbed higher amounts of a candidate volatile than pristine silica. The study outcomes highlights the advantages of a bio-derived modifier in asphalt to address concerns associated with the loss of hazardous compounds.

Exposure of construction workers to hazardous emissions in highway rehabilitation projects measured with low-cost sensors

Construction workers on highway rehabilitation projects can be exposed to a combination of traffic- and construction-related emissions. To assess the personal exposure a worker experiences, a portable battery-operated Air Quality Device (AQD) was utilised to measure emissions during normal construction operations of a major road rehabilitation project. Emissions measured were nitrogen dioxide (NO₂), Total Volatile Organic Compounds (TVOCs) and Particulate Matter (PM₁₀, PM_2.5, and PM₁). The objective of the paper is to document the hazardous emissions that construction workers may be exposed to and allow for a basis of informed decision making to mitigate the risks of a road construction project. Most critically, this article is designed to raise awareness of the potential impact to a worker's wellbeing as well as highlight the need for further research. Through statistical analysis, asphalt paving was identified as the most hazardous activity in terms of exposure relative to other activities. This activity was further assessed using discrete-time Markov chain Monte Carlo simulations with results indicating a high probability that workers may be exposed to greater hazardous emission concentrations than measured. Limiting the distance to the source of emissions, large-scale use of warm-mix asphalt and reducing the idling times of construction vehicles were identified as practical mitigation measures to reduce exposure and aid in achieving zero-harm objectives. Finally, it is found that males are more susceptible to long-term implications of hazardous emission inhalation and should be more aware if the scenarios they might work in expose them to this.

Microwave-induced steam distillation (MISD) remediation in petroleum hydrocarbon-contaminated sites: From process improvement to pilot application

The process improvement, a pilot remediation test and the decontamination mechanism of microwave-induced steam distillation (MISD) for petroleum hydrocarbons (PHs) removal were conducted. Processes of multistage steam distillation and carbon reinforcement were compared to determine the best remediation process. Pilot project was then carried out to explore the applicability of MISD in site-scale remediation. The remediation efficiency, procedures and influencing factors of site-scale MISD project were studied by monitoring variations of soil moisture, temperature and PHs concentrations. Furthermore, the decontamination mechanisms of PHs were clarified based on kinetic analysis. The results showed that the multistage steam distillation could improve 10%∼15% remediation efficiency, and the carbon reinforcement could shorten remediation duration of each steam distillation stage by 50%. Pilot MISD project adopted multistage steam distillation process and went through four (initial, rapid heating-up, gentle heating-up and quasi-equilibrium) remediation stages (overall temperature ≤100 °C). The final PHs removal rate was about 60%, which would get better with greater proportion of low boiling points components and stronger vapor extraction. Kinetic studies showed that PHs was removed by steam stripping and limited by intraparticle diffusion in the "steam distillation zone", while local high temperature (＞100 °C) greatly improved PHs volatilization and provided activation energy for PHs desorbed and degraded in the "selective heating zone".

Ozone pollution in the plate and logistics capital of China: Insight into the formation, source apportionment, and regional transport

As the logistics and plate capital of China, the sources and regional transport of O₃ in Linyi are different from those in other cities because of the significant differences in industrial structure and geographical location. Twenty-five ozone pollution episodes (OPEs, 52 days) were identified in 2021, with a daily maximum 8-h moving average O₃ concentration (O_3-MDA8) of 184.5 ± 22.5 μg/m³. Oxygenated volatile organic compounds (OVOCs) and aromatics were the dominant contributors to ozone formation potential (OFP), with contributions of approximately 23.5-52.7% and 20.0-40.8%, respectively, followed by alkenes, alkanes, and alkynes. Formaldehyde, an OVOC with high concentrations emitted from the plate industry and vehicles, contributed the most to OFP (22.7 ± 5.5%), although formaldehyde concentrations only accounted for 9.4 ± 2.7% of the total non-methane hydrocarbon (NMHC) concentrations. The source apportionment results indicated that the plate industry was the dominant O₃ contributor (27.0%), followed by other sources (21.6%), vehicle-related sources (18.0%), solvent use (16.9%), liquefied petroleum gas (LPG)/natural gas (NG) (8.8%), and combustion sources (7.7%). Therefore, there is an urgent need to control the plating industry in Linyi to mitigate O₃ pollution. The backward trajectory, potential source contribution function (PSCF), and concentration weighted trajectory (CWT) models were used to identify the air mass pathways and potential source areas of air pollutants during the OPEs. O₃ pollution was predominantly affected by air masses that originated from eastern and local regions, while trajectories from the south contained the highest O₃ concentrations (207.0 μg/m³). The potential source area was from east and south Linyi during the OPEs. Therefore, it is critical to implement regional joint prevention and control measures to lower O₃ concentrations.

Coupling of metataxonomics and culturing improves bacterial diversity characterization and identifies a novel Rhizorhapis sp. with metal resistance potential in a multi-contaminated waste sediment

Long-term contaminated environments have been recognized as potential hotspots for bacterial discovery in taxonomic and functional terms for bioremediation purposes. Here, bacterial diversity in waste sediment collected from a former industrial dumpsite and contaminated with petroleum hydrocarbon and heavy metals was investigated through the parallel application of culture-independent (16S rRNA gene amplicon sequencing) and -dependent (plate culturing followed by colony picking and identification of isolates by 16S rRNA gene Sanger sequencing) approaches. The bacterial diversities retrieved by both approaches greatly differed. Bacteroidetes and Proteobacteria were dominant in the culture-independent community, while Firmicutes and Actinobacteria were the main culturable groups. Only 2.7% of OTUs (operational taxonomic units) in the culture-independent dataset were cultured. Most of the culturable OTUs were absent or in very low abundances in the culture-independent dataset, revealing that culturing is a useful tool to study the rare bacterial biosphere. One culturable OTUs (comprising only the isolate SPR117) was identified as a potential new species in the genus Rhizorhapis (class Alphaproteobacteria) and was selected for further characterization. Phytopathogenicity tests showed that Rhizorhapis sp. strain SPR117 (ATCC TSD-228) is not pathogenic to lettuce, despite the only described species in this genus, Rhizorhapis suberifaciens, is causal agent of the lettuce corky root disease. The genome of the strain SPR117 was sequenced, assembled in 256 contigs, with a length of 4,419,522 bp and a GC content of 59.9%, and its further annotation revealed the presence of genes related to the resistance to arsenic, copper, iron, and mercury, among other metals. Therefore, the coupling of metataxonomics and culturing is a useful tool to obtain not only an improved description of bacterial communities in contaminated environments, but also to isolate microorganisms with bioremediation potential.

A Comparative Review of Hot and Warm Mix Asphalt Technologies from Environmental and Economic Perspectives: Towards a Sustainable Asphalt Pavement

The environmental concerns of global warming and energy consumption are among the most severe issues and challenges facing human beings worldwide. Due to the relatively higher predicted temperatures (150-180 °C), the latest research on pavement energy consumption and carbon dioxide (CO₂) emission assessment mentioned contributing to higher environmental burdens such as air pollution and global warming. However, warm-mix asphalt (WMA) was introduced by pavement researchers and the road construction industry instead of hot-mix asphalt (HMA) to reduce these environmental problems. This study aims to provide a comparative overview of WMA and HMA from environmental and economic perspectives in order to highlight the challenges, motivations, and research gaps in using WMA technology compared to HMA. It was discovered that the lower production temperature of WMA could significantly reduce the emissions of gases and fumes and thus reduce global warming. The lower production temperature also provides a healthy work environment and reduces exposure to fumes. Replacing HMA with WMA can reduce production costs because of the 20-75% lower energy consumption in WMA production. It was also released that the reduction in energy consumption is dependent on the fuel type, energy source, material heat capacity, moisture content, and production temperature. Other benefits of using WMA are enhanced asphalt mixture workability and compaction because the additives in WMA reduce asphalt binder viscosity. It also allows for the incorporation of more waste materials, such as reclaimed asphalt pavement (RAP). However, future studies are recommended on the possibility of using renewable, environmentally friendly, and cost-effective materials such as biomaterials as an alternative to conventional WMA-additives for more sustainable and green asphalt pavements.

Functional characterization of the ABC transporters and transposable elements of an uncultured Paracoccus sp. recovered from a hydrocarbon-polluted soil metagenome

Environmental microorganisms usually exhibit a high level of genomic plasticity and metabolic versatility that allow them to be well-adapted to diverse environmental challenges. This study used shotgun metagenomics to decipher the functional and metabolic attributes of an uncultured Paracoccus recovered from a polluted soil metagenome and determine whether the detected attributes are influenced by the nature of the polluted soil. Functional and metabolic attributes of the uncultured Paracoccus were elucidated via functional annotation of the open reading frames (ORFs) of its contig. Functional tools deployed for the analysis include KEGG, KEGG KofamKOALA, Clusters of Orthologous Groups of proteins (COG), Comprehensive Antibiotic Resistance Database (CARD), and the Antibiotic Resistance Gene-ANNOTation (ARG-ANNOT V6) for antibiotic resistance genes, TnCentral for transposable element, Transporter Classification Database (TCDB) for transporter genes, and FunRich for gene enrichment analysis. Analyses revealed the preponderance of ABC transporter genes responsible for the transport of oligosaccharides (malK, msmX, msmK, lacK, smoK, aglK, togA, thuK, treV, msiK), monosaccharides (glcV, malK, rbsC, rbsA, araG, ytfR, mglA), amino acids (thiQ, ynjD, thiZ, glnQ, gluA, gltL, peb1C, artP, aotP, bgtA, artQ, artR), and several others. Also detected are transporter genes for inorganic/organic nutrients like phosphate/phosphonate, nitrate/nitrite/cyanate, sulfate/sulfonate, bicarbonate, and heavy metals such as nickel/cobalt, molybdate/tungstate, and iron, among others. Antibiotic resistance genes that mediate efflux, inactivation, and target protection were detected, while transposable elements carrying resistance phenotypes for antibiotics and heavy metals were also annotated. The findings from this study have established the resilience, adaptability, and survivability of the uncultured Paracoccus in the hydrocarbon-polluted soil.