Mesopelagic microbial community dynamics in response to increasing oil and Corexit 9500 concentrations.

Marine microbial communities play an important role in biodegradation of subsurface plumes of oil that form after oil is accidentally released from a seafloor wellhead. The response of these mesopelagic microbial communities to the application of chemical dispersants following oil spills remains a debated topic. While there is evidence that contrasting results in some previous work may be due to differences in dosage between studies, the impacts of these differences on mesopelagic microbial community composition remains unconstrained. To answer this open question, we exposed a mesopelagic microbial community from the Gulf of Mexico to oil alone, three concentrations of oil dispersed with Corexit 9500, and three concentrations of Corexit 9500 alone over long periods of time. We analyzed changes in hydrocarbon chemistry, cell abundance, and microbial community composition at zero, three and six weeks. The lowest concentration of dispersed oil yielded hydrocarbon concentrations lower than oil alone and microbial community composition more similar to control seawater than any other treatments with oil or dispersant. Higher concentrations of dispersed oil resulted in higher concentrations of microbe-oil microaggregates and similar microbial composition to the oil alone treatment. The genus Colwellia was more abundant when exposed to multiple concentrations of dispersed oil, but not when exposed to dispersant alone. Conversely, the most abundant Marinobacter amplicon sequence variant (ASV) was not influenced by dispersant when oil was present and showed an inverse relationship to the summed abundance of Alcanivorax ASVs. As a whole, the data presented here show that the concentration of oil strongly impacts microbial community response, more so than the presence of dispersant, confirming the importance of the concentrations of both oil and dispersant in considering the design and interpretation of results for oil spill simulation experiments.

The potential of medicinal plant extracts in improving the phytoremediation capacity of Solanum nigrum L. for heavy metal contaminated soil.

This study focused on the effects of eight medicinal plant extracts on Solanum nigrum L. potential to accumulate Cd and Pb from soil. These medicinal plants were common and relatively cheap. The eight 10% water extracts were made from the peel of Citrus reticulata Blanco (PCR), fruit of Phyllanthus emblica L. (FPE), root of Pueraria Lobata (Willd.) Ohwi (RPL), rhizome of Polygonatum sibiricum Red (RPS), root of Astragalus propinquus Schischkin (RAP), bud of Hemerocallis citrina Baroni (BHC), seed of Nelumbo nucifera Gaertn (SNN) and fruit of Prunus mume (Sieb.) Sieb.etZuce (FPM). The results showed that among all exposures, the treatment with FPE resulted in the significant increase (p < 0.05) of Cd and Pb concentration in shoots and roots of S. nigrum by 32.5% and 65.2% for Cd, and 38.7% and 39.6% for Pb. The biomasses of S. nigrum in all plant extract treatments were not significantly changed (p < 0.05) compared to the control (CK). The Cd and Pb extraction rates of S. nigrum in FPE treatment were increased respectively by 60.5% and 40.5% compared to CK. Though the treatment with EDTA significantly improved (p < 0.05) the concentration of Cd and Pb of S. nigrum, the Cd and Pb masses (ug plant-1) of S. nigrum did not show any significant difference compared to the CK due to the significant decrease in the shoot (20.4%) and root (22.0%) biomasses. The chelative role of FPE might be relation with its higher polyphenolic compounds. However, not sure if the contents of polyphenolic compounds was the only differences between FPE and other additives. Thus, some unknown organic matters might also play active role. This study provided valuable information on improving the phytoremediation potential of hyperaccumulator.

Human and Aquatic Toxicity Potential of Petroleum Biodegradation Metabolite Mixtures in Groundwater from Fuel Release Sites.

The potential toxicity to human and aquatic receptors of petroleum fuel biodegradation metabolites (oxygen-containing organic compounds [OCOCs]) in groundwater has been investigated as part of a multi-year research program. Whole mixtures collected from locations upgradient and downgradient of multiple fuel release sites were tested using: 1) in vitro screening assays for human genotoxicity (the gamma-H2AX assay) and estrogenic effects (estrogen receptor transcriptional activation assay), and 2) chronic aquatic toxicity tests in 3 species (Ceriodaphnia dubia, Raphidocelis subcapitata, and Pimephales promelas). In vitro screening assay results demonstrated that the mixtures did not cause genotoxic or estrogenic effects. No OCOC-related aquatic toxicity was observed and when aquatic toxicity did occur, upgradient samples typically had the same response as samples downgradient of the release, indicating that background water quality was impacting the results. This information provides additional support for previous work that focused on the individual compounds and, taken together, indicates that OCOCs from petroleum degradation at fuel release sites are unlikely to cause toxicity to human or freshwater receptors at the concentrations present. Environ Toxicol Chem 2020;39:1634-1645. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Effect of Citric Acid on Growth, Ecophysiology, Chloroplast Ultrastructure, and Phytoremediation Potential of Jute (Corchorus capsularis L.) Seedlings Exposed to Copper Stress.

Soil and water contamination from heavy metals and metalloids is one of the most discussed and caused adverse effects on food safety and marketability, crop growth due to phytotoxicity, and environmental health of soil organisms. A hydroponic investigation was executed to evaluate the influence of citric acid (CA) on copper (Cu) phytoextraction potential of jute (Corchorus capsularis L.). Three-weeks-old seedlings of C. capsularis were exposed to different Cu concentrations (0, 50, and 100 µM) with or without the application of CA (2 mM) in a nutrient growth medium. The results revealed that exposure of various levels of Cu by 50 and 100 µM significantly (p < 0.05) reduced plant growth, biomass, chlorophyll contents, gaseous exchange attributes, and damaged ultra-structure of chloroplast in C. capsularis seedlings. Furthermore, Cu toxicity also enhanced the production of malondialdehyde (MDA) which indicated the Cu-induced oxidative damage in the leaves of C. capsularis seedlings. Increasing the level of Cu in the nutrient solution significantly increased Cu uptake by the roots and shoots of C. capsularis seedlings. The application of CA into the nutrient medium significantly alleviated Cu phytotoxicity effects on C. capsularis seedlings as seen by plant growth and biomass, chlorophyll contents, gaseous exchange attributes, and ultra-structure of chloroplast. Moreover, CA supplementation also alleviated Cu-induced oxidative stress by reducing the contents of MDA. In addition, application of CA is helpful in increasing phytoremediation potential of the plant by increasing Cu concentration in the roots and shoots of the plants which is manifested by increasing the values of bioaccumulation (BAF) and translocation factors (TF) also. These observations depicted that application of CA could be a useful approach to assist Cu phytoextraction and stress tolerance against Cu in C. capsularis seedlings grown in Cu contaminated sites.

Cadmium influences the litter decomposition of Solidago canadensis L. and soil N-fixing bacterial communities.

It is important to illuminate the effects of litter decomposition of invasive alien species on soil N-fixing bacterial communities (SoNiBa), especially under heavy metal pollution to better outline the mechanisms for invasion success of invasive alien species. This study attempts to identify the effects of litter decomposition of Solidago canadensis L. on SoNiBa under cadmium (Cd) pollution with different concentrations (i.e., low concentration, 7.5 mg/kg soil; high concentration, 15 mg/kg soil) via a polyethylene litterbags-experiment. Electrical conductivity and total N of soil were the most important environmental factors for determining the variations of SoNiBa composition. S. canadensis did not significantly affect the alpha diversity of SoNiBa but significantly affect the beta diversity of SoNiBa and SoNiBa composition. Thus, SoNiBa composition, rather than alpha diversity of SoNiBa, was the most important determinant of the invasion success of S. canadensis. Cd with 15 mg/kg soil did not address distinct effects on alpha diversity of SoNiBa, but Cd with 7.5 mg/kg soil noticeably raised the number of species and species richness of SoNiBa mainly due to the hormonal effects. The combined S. canadensis and Cd with 15 mg/kg soil obviously decreased cumulative mass losses and the rate of litter decomposition (k) of S. canadensis, but the combined S. canadensis and Cd with 7.5 mg/kg soil evidently accelerated cumulative mass losses and k of S. canadensis. Thus, Cd with 7.5 mg/kg soil can accelerate litter decomposition of S. canadensis, but Cd with 15 mg/kg soil can decline litter decomposition of S. canadensis.

Long-term effects of silver nanoparticles on performance of phosphorus removal in a laboratory-scale vertical flow constructed wetland.

Silver nanoparticles (AgNPs) have been widely used in many fields, which raised concerns about potential threats to biological sewage treatment systems. In this study, the phosphorus removal performance, enzymatic activity and microbial population dynamics in constructed wetlands (CWs) were evaluated under a long-term exposure to AgNPs (0, 50, and 200 µg/L) for 450 days. Results have shown that AgNPs inhibited the phosphorus removal efficiency in a short-term exposure, whereas caused no obviously negative effects from a long-term perspective. Moreover, in the coexisting CW system of AgNPs and phosphorus, competition exhibited in the initial exposure phase, however, cooperation between them was observed in later phase. Enzymatic activity of acid-phosphatase at the moderate temperature (10-20°C) was visibly higher than that at the high temperature (20-30°C) and CWs with AgNPs addition had no appreciable differences compared with the control. High-throughput sequencing results indicated that the microbial richness, diversity and composition of CWs were distinctly affected with the extension of exposure time at different AgNPs levels. However, the phosphorus removal performance of CWs did not decline with the decrease of polyphosphate accumulating organisms (PAOs), which also confirmed that adsorption precipitation was the main way of phosphorus removal in CWs. The study suggested that AgNPs and phosphorus could be removed synergistically in the coexistence system. This work has some reference for evaluating the influences of AgNPs on the phosphorus removal and the interrelation between them in CWs.

Beyond N and P: The impact of Ni on crude oil biodegradation.

N and P are the key limiting nutrients considered most important for the stimulation of crude oil degradation but other trace nutrients may also be important. Experimental soil microcosms were setup to investigate crude oil degradation in the context of Ni amendments. Amended Nickel as NiO, NiCl2, or, a porphyrin complex either inhibited, had no effect, or, enhanced aerobic hydrocarbon degradation in an oil-contaminated soil. Biodegradation was significantly (95% confidence) enhanced (70%) with low levels of Ni-Porph (12 mg/kg) relative to an oil-only control; whereas, NiO (200 and 350 mg/kg) significantly inhibited (36 and 87%) biodegradation consistent with oxide particle induced reactive oxygen stress. Microbial community compositions were also significantly affected by Ni. In 16S rRNA sequence libraries, the enriched hydrocarbon degrading genus, Rhodococcus, was partially replaced by a Nocardia sp. in the presence of low levels of NiO (12 and 50 mg/kg). In contrast, the highest relative and absolute Rhodococcus abundances were coincident with the maximal rates of oil degradation observed in the Ni-Porph-amended soils. Growth dependent constitutive requirements for Ni-dependent urease or perhaps Ni-dependent superoxide dismutase enzymes (found in Rhodococcus genomes) provided a mechanistic explanation for stimulation. These results suggest biostimulation technologies, in addition to N and P, should also consider trace nutrients such as Ni tacitly considered adequately supplied and available in a typical soil.

Effects of macro metals on alkaline phosphatase activity under conditions of sulfide accumulation.

Alkaline phosphatase (AP) is commonly found in aquatic ecosystems as an extracellular enzyme closely related to the biogeochemical cycling of phosphorus. Although the AP activity (APA) is conventionally thought to be a main response to PO43- starvation, significant effects of macro metal elements (Al, Fe, and Ca) and S on the APA were found in this study. The APA was reduced by Al primarily through the adsorption of the enzyme onto AlOOH colloids. Fe2+ inhibited the APA via a mechanism involving free radical oxidation. The main mechanism by which Ca2+ inhibited the APA was by competing with Mg2+ and Zn2+ for the active sites of the enzyme. Excessive S2- could reduce the APA by removing Zn2+ from the active sites of the enzyme. The inhibition of APA could be reversed if some metal ions (e.g., Fe2+) were precipitated by S2- under reducing conditions. Therefore, in anaerobic ecosystems, the effects of macro metals on APA under conditions of sulfide accumulation may have innovative implications for phosphorus management.

Growth stage and molybdenum treatment affect cadmium accumulation, antioxidant defence and chlorophyll contents in Cannabis sativa plant.

Cadmium (Cd) uptake and accumulation in plant tissues is affected by physiological stage of a plant and presence of mineral nutrients in soil. We investigate the effect of micronutrient Mo (0.5, 1.0 and 2.0 ppm) on biomass, Cd accumulation, photosynthetic pigments and endogenous phenolics and soluble proline in Cannabis sativa plant grown in 25 and 50 ppm Cd polluted soil. Molybdenum was applied as seed soaking and soil addition treatments. The plants were harvested in two stages i.e. vegetative (6 weeks) and reproductive stages (12 weeks). It was found that seed soaking treatment of 1.0 ppm Mo most significantly increased biomass, Cd accumulation (1.76 ±â€¯0.19 mg Cd/DBM) and phenolics (104.5 ±â€¯4.46 ppm) concentration in the plant tissues. Molybdenum treatments highly increased Cd bio-concentration at reproductive stage as compared to vegetative stage in plants grown in 50 ppm Cd polluted soil. Translocation of Cd from roots into leaves was significantly increased by Mo treatments at reproductive stage as compared to vegetative stage. Strong inter-correlations existed between total phenolics, Cd accumulation, dry biomass and chlorophyll contents of the plant.

The impact of lead co-contamination on ecotoxicity and the bacterial community during the bioremediation of total petroleum hydrocarbon-contaminated soils.

The continued increase in the global demand for oil, which reached 4,488 Mtoe in 2018, leads to large quantities of petroleum products entering the environment posing serious risks to natural ecosystems if left untreated. In this study, we evaluated the impact of co-contamination with lead on the efficacy of two bioremediation processes, natural attenuation and biostimulation of Total Petroleum Hydrocarbons (TPH) as well as the associated toxicity and the changes in the microbial community in contaminated soils. The biostimulated treatment resulted in 96% and 84% reduction in TPH concentration in a single and a co-contamination scenario, respectively, over 28 weeks of a mesocosm study. This reduction was significantly more in comparison to natural attenuation in a single and a co-contamination scenario, which was 56% and 59% respectively. In contrast, a significantly greater reduction in the associated toxicity of in soils undergoing natural attenuation was evident compared with soils undergoing biostimulation despite the lower TPH degradation when bioassays were applied. The earthworm toxicity test showed a decrease of 72% in the naturally attenuated toxicity versus only 62% in the biostimulated treatment of a single contamination scenario. In a co-contamination scenario, toxicity decreased only 30% and 8% after natural attenuation and biostimulation treatments, respectively. 16s rDNA sequence analysis was used to assess the impact of both the co-contamination and the bioremediation treatment. NGS data revealed major bacterial domination by Nocardioides spp., which reached 40% in week 20 of the natural attenuation treatment. In the biostimulated soil samples, more than 50% of the bacterial community was dominated by Alcanivorax spp. in week 12. The presence of Pb in the natural attenuation treatment resulted in an increased abundance of a few Pb-resistant genera such as Sphingopyxis spp. and Thermomonas spp in addition to Nocardioides spp. In contrast, Pb co-contamination completely shifted the bacterial pattern in the stimulated treatment with Pseudomonas spp. comprising approximately 45% of the bacterial profile in week 12. This study confirms the effectiveness of biostimulation over natural attenuation in remediating TPH and TPH-Pb contaminated soils. In addition, the presence of co-contaminants (e.g. Pb) results in serious impacts on the efficacy of bioremediation of TPH in contaminated soils, which must be considered prior to designing any bioremediation strategy.

Reduction of hexavalent chromium (VI) by indigenous alkaliphilic and halotolerant Microbacterium sp. M5: comparative studies under growth and nongrowth conditions.

AIMS: To evaluate hexavalent chromium (Cr (VI)) reduction potential of indigenous isolate M5, under growing and nongrowing conditions. METHODS AND RESULTS: Microbacterium sp. M5 was isolated from soil samples collected from a common effluent treatment plant, after enrichment of indigenous microbial diversity in the presence of 200 mg l-1 of Cr (VI). The isolate achieved complete reduction of 400 mg l-1 Cr (VI) supplement to Luria Bertani medium having initial pH of 9·0 after 48 h incubation. Furthermore, the reduction potential of resting and surfactant treated cell membrane compromised cells of M5 was evaluated. The control and biosurfactant treated cells achieved 22·71 ± 0·5% and 40·56 ± 0·5% reduction of 50 mg l-1 Cr (VI) in Tris-HCl buffer, under resting cells conditions. To the best of our knowledge, this is the first report where cells with compromised cell membrane obtained after exposure to biosurfactant have been evaluated for Cr (VI) reduction. CONCLUSION: The Cr (VI) reduction potential of Microbacterium sp. M5 could be effectively exploited for treatment of chromium-rich effluents, under nongrowing conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: The isolate M5 could be a potential inoculum for effluent treatment plants as it is able to support Cr (VI) reduction under wide range of pH, salinity and in the presence of different metal ions.

Microbial induced carbonate precipitation for immobilizing Pb contaminants: Toxic effects on bacterial activity and immobilization efficiency.

Microbial induced carbonate precipitation (MICP) is a natural bio-mediated process, which has been explored for soil stabilization and heavy metals immobilization in soil and groundwater. Previous studies have shown that MICP is capable of immobilizing various heavy metals including lead (Pb). However, most studies focus merely on the immobilization of heavy metals with relatively low concentration. This study: (1) presents results of an investigation into the toxic effects of Pb on bacterial activity and immobilization efficiency within a wide range of Pb concentrations; and (2) identifies controlling biotic and abiotic factors of Pb immobilization by MICP. In the first series of tests, bacterial strains (Sporosarcina pasteurii) are inoculated into nutrient solutions containing 0-50 mM Pb(NO3)2 and incubated at 30 °C. Biochemical parameters are measured over time, which include pH, electrical conductivity, urease activity, and viable cell number. In the second series of tests, grown bacterial strains are mixed with urea, calcium salts and Pb(NO3)2 in solution. Viable cell number, produced ammonium concentration, aqueous Pb concentration of the mixed solution, and total precipitation mass are measured. The results show that the presence of Pb has marginal effect on bacterial growth and associated urease activity at Pb concentration < 30 mM. The calcium source and initial bacteria concentration are found to remarkably influence Pb immobilization efficiency in terms of Pb removal percentage. Supplementary geochemical simulation results indicate that the Pb immobilization mechanisms includes abiotic precipitation, biotic precipitation and bio-sorption.

Influence of graphene oxide and biochar on anaerobic degradation of petroleum hydrocarbons.

The anaerobic degradation of petroleum is an important process in natural environments. So far, few studies have considered the response of the microbial community to nanomaterials during this process. This study explored the potential effects of graphene oxide and biochar on the anaerobic degradation of petroleum hydrocarbons in long-term experiments. Cyclic voltammetry and electrochemical impedance spectroscopy indicated that the addition of carbon-based materials promoted the electrochemical activity of anaerobic cultures that degrade petroleum hydrocarbons. The maximum degradation rates for benzene, toluene, ethylbenzene, and xylene (BTEXs) in the cultures incubated for 10 weeks with graphene oxide (0.02 mg/L) and biochar (20 mg/L) were 76.5% and 77.6%, respectively. The maximum degradation rates of n-alkanes in the cultures incubated for 10 weeks with graphene oxide (2 mg/L) and biochar (100 mg/L) were 70.0% and 77.8%, respectively. The 16S rDNA copy numbers in the treatments with 0.02 mg/L graphene oxide and 20 mg/L biochar were significantly higher than others during the process (P < 0.05). In the 2nd week, the maximum copy numbers of the masD and bamA genes in the treatments with biochar were 349 copies/mL (20 mg/L) and 422 copies/mL (20 mg/L), respectively, and in the treatments with graphene oxide were 289 copies/mL (0 mg/L) and 366 copies/mL (0.02 mg/L). The contents of carbon-based materials had slight effects on the microbial community structure, whereas the culture time had obvious effects. Paracoccus denitrificans, Pseudomonas aeruginosa, and Hydrogenophaga caeni were the dominant microorganisms in the culture systems under all treatments.

Enhancement the Cellulase Activity Induced by Endophytic Bacteria Using Calcium Nanoparticles.

The huge applications of cellulosic and lignocellulosic materials in the various fields of life lead to accumulation of its wastes that became one of the major sources of environmental pollution. In this study, a Gram-positive cellulose-decomposing endophytic bacterium (Chi-04) was isolated from medicinal plant Chiliadenus montanus which inhabitant Saint Catherine (Sinai) region in Egypt. The bacterial strain was identified based on the sequence analysis of 16S rRNA genes as Lysinibacillus xylanilyticus. This isolate was capable of degrading 58% of cellulosic filter paper (100 g/l) within 15 days of incubation. The soluble and reduced sugars were spectrophotometrically determined as cellulose decomposition metabolites. The bacterial isolate exhibited an obvious activity toward cellulase enzyme production. The maximum cellulase activity (0.18 U/min) was detected after 12 days of incubation while the maximum release of soluble sugars (11.85 mg/ml) was detected after 15 days of incubation. CaCl2 nanoparticles (100 nm) were chemically prepared to enhance the activity of the enzyme. The optimum concentration of CaCl2 nanoparticles that showed the highest activity of cellulase (0.3 mg/ml reduced sugar) was 0.6%. The bacterial isolates showed potential convert of cellulose into reducing sugars which could be used in several applications.

Effects of soil amendments on the growth response and phytoextraction capability of a willow variety (S. viminalis × S. schwerinii × S. dasyclados) grown in contaminated soils.

This study was conducted to evaluate the effects of lime and bisphosphonates (BPs) such as N10O chelate amendment on the growth, physiological and biochemical parameters, and phytoextraction potential of the willow variety Klara (Salix viminalis × S. schwerinii × S. dasyclados) grown in soils heavily contaminated with copper (Cu), nickel (Ni) and zinc (Zn). The plants were irrigated with tap or processed water (mine wastewater). The results suggest that the combined effects of the contaminated soil and processed water inhibited growth parameters, gas exchange parameters and chlorophyll fluorescence (Fv/Fm) values. In contrast, malondialdehyde (MDA) content, organic acids, total phenolic and total flavonoid contents, and the accumulation of metals/metalloids in the plant tissues were increased compared to the control. When the soil was supplemented with lime and N10O; growth, physiological, biochemical parameters, and resistance capacity were significantly higher compared to unamended soil treatments, especially in the contaminated soil treatments. The combined lime‒ and N10O‒amended soil treatment produced higher growth rates, resistance capacity, photosynthesis rates and phytoextraction efficiency levels relative to either the lime‒amended or the N10O‒amended soil treatments. This study provides practical evidence of the efficient chelate‒assisted phytoextraction capability of Klara and highlights its potential as a viable and inexpensive novel approach for in situ remediation of Cu‒, Ni‒ and Zn‒contaminated soils and mine wastewaters.

Effects of nano-sized MnO2 on methanogenic propionate and butyrate degradation in anaerobic digestion.

The responses of methanogenic propionate and butyrate degradation to nano-sized MnO2 exposure were explored. The results showed that supplementation with 50 mg/g volatile suspended solids (VSS) of nano-sized MnO2 significantly enhanced the production rate of CH4 in propionate and butyrate degradation by 25.6% and 21.7%, respectively. The stimulatory effects most likely resulted from enhancements in the microbial metabolic activity based on the observed increases in the extracellular polymeric substance (EPS) secretion and activity of the electron transport system. In contrast, the CH4 yields obtained were irreversibly inhibited by the presence of 400 mg/g VSS of nano-sized MnO2, in which just 62.8% and 6.5%, respectively, of the yield obtained from the control. Further investigations indicated that supplementation by nano-sized MnO2 could cause oxidative stress in microbial cells, resulting in the release of reactive oxygen species (ROS). Compared with that of the control, the amount of intracellular ROS generated in the systems increased by 28.3% (fed with propionate) and 42.5% (fed with butyrate), corresponding to approximately 43.9% and 64.8% losses in cell viability, respectively; thus, ROS generation was suggested to be the main factor responsible for the inhibitory effects of nano-sized MnO2 on methanogenic propionate and butyrate degradation.

An efficient and environmental-friendly dispersant based on the synergy of amphiphilic surfactants for oil spill remediation.

Eliminating the adverse environmental impact of chemical dispersants for oil spill has been a significant challenge since decades ago. Here, we prepared an effective and environmentally-friend dispersant with stable emulsifying capacity by the soybean lecithin and Tween 80. The mean droplet diameters of emulsions prepared by decane decreased from 11.3 to 4.1 µm, the emulsification index of emulsion climbed from 0 to 22.0% by 0.5 wt% dispersant. This dispersant exhibits favorable emulsifying capacity when the temperature ranges from 10 to 40 °C, pH within 5-7, and the concentration of inorganic cation is 30000 mg/L. Fluorescence microscopy analysis, FTIR, and the interfacial tension meter were employed to investigate the interaction between the soybean lecithin and Tween 80, a clear redshift of the hydroxyl group on the lecithin/Tween 80 dispersant and the detected surfactants over the oil-water interface confirm that there exists a synergy between the lecithin and Tween 80 due to the electrostatic attractions, which tremendously contribute to the reduction in the interfacial tension between water and oil. To further understand the influence of the dispersant on the oil hydrocarbon concentration in the water column, visualization simulation with the varying depths were performed. The results showed that the oil hydrocarbon concentration in the water column bottom was proportional to the addition of the dispersant, which facilitates spilled oil dispersing into smaller droplets, accelerates the biodegradation process. Hence, the lecithin/Tween 80 dispersant can be perceived as a promising alternative for oil spill remediation.

Multi-method assessment of the intrinsic biodegradation potential of an aquifer contaminated with chlorinated ethenes at an industrial area in Barcelona (Spain).

The bioremediation potential of an aquifer contaminated with tetrachloroethene (PCE) was assessed by combining hydrogeochemical data of the site, microcosm studies, metabolites concentrations, compound specific-stable carbon isotope analysis and the identification of selected reductive dechlorination biomarker genes. The characterization of the site through 10 monitoring wells evidenced that leaked PCE was transformed to TCE and cis-DCE via hydrogenolysis. Carbon isotopic mass balance of chlorinated ethenes pointed to two distinct sources of contamination and discarded relevant alternate degradation pathways in the aquifer. Application of specific-genus primers targeting Dehalococcoides mccartyi species and the vinyl chloride-to-ethene reductive dehalogenase vcrA indicated the presence of autochthonous bacteria capable of the complete dechlorination of PCE. The observed cis-DCE stall was consistent with the aquifer geochemistry (positive redox potentials; presence of dissolved oxygen, nitrate, and sulphate; absence of ferrous iron), which was thermodynamically favourable to dechlorinate highly chlorinated ethenes but required lower redox potentials to evolve beyond cis-DCE to the innocuous end product ethene. Accordingly, the addition of lactate or a mixture of ethanol plus methanol as electron donor sources in parallel field-derived anoxic microcosms accelerated dechlorination of PCE and passed cis-DCE up to ethene, unlike the controls (without amendments, representative of field natural attenuation). Lactate fermentation produced acetate at near-stoichiometric amounts. The array of techniques used in this study provided complementary lines of evidence to suggest that enhanced anaerobic bioremediation using lactate as electron donor source is a feasible strategy to successfully decontaminate this site.

Effects of gibberellic acid on Tifton 85 bermudagrass (Cynodon spp.) in constructed wetland systems.

This study aimed to evaluate 1) the influence of gibberellic acid (GA3) in the development of Tifton 85 bermudagrass grown in constructed wetland systems (CWs) and 2) the plant's capacity to remove nutrients and sodium from synthetic municipal wastewater (SMW). The experiment was carried out in Viçosa, Minas Gerais, Brazil, and consisted of foliar applications of GA3 set in randomized blocks design, with four replicates and 6 treatments as following: NC (control with plants); 0 µM GA3; N1: 5 µM GA3; N2: 25 µM GA3; N3: 50 and N4: 100 µM GA3 per CWs, NC* (control with no plants): 0 µM GA3. The study was conducted over two crop cycles in the spring 2016. The parameters used to evaluate the performance of the Tifton 85 bermudagrass were its plant height, productivity, chlorophyll measurement, number of internodes, nutrients and Na removals. Chemical analyses of the effluents were conducted. In response to the application of GA3, the increase in height of Tifton 85 bermudagrass in the first crop cycle was higher than the increase in height in the second crop cycle. The decrease in plant growth in response to GA3 in the second crop cycle may be linked to the age of the plant tissue and climatic conditions. The greater growth of the plants cultivated in the CWs allows a more efficient removal of pollutants, using simple management and low cost. The results suggest that applying 50 µM of GA3 to the development of Tifton 85 bermudagrass provides higher dry matter yield and removal of nitrogen, phosphorus, and sodium for the first crop cycle in CWs. However, in the second crop cycle, the application of GA3 had no effect on dry matter production and nutrient removal by Tifton 85 bermudagrass in CWs.

Guar gum blended alginate/agarose hydrogel as a promising support for the entrapment of peroxidase: Stability and reusability studies for the treatment of textile effluent.

Ginger peroxidase (GP) was entrapped into the hydrogels of guar gum (GG)-alginate/agarose and these immobilized GP preparations were employed for the treatment of textile effluent. GG is a natural hydrophilic polysaccharide, the average size of which increases in its hydrated form that helps in retaining the enzyme inside the entrapping support. Therefore, the activity retention by alginate-guar gum (ANGG) and agarose-guar gum (AGG) was higher than that of alginate and agarose alone. ANGG-GP and AGG-GP were highly stable against various physical and chemical denaturants during the decolorization of textile effluent. As compared to free GP, both the immobilized preparations were more efficient in the decolorization of textile effluent in batch processes. After 10th repeated use in batch processes, ANGG-GP and AGG-GP was quite effective in removing up to 68% and 55% of the color from textile effluent, respectively. Continuous packed bed reactors containing ANGG-GP and AGG-GP were able to decolorize around 80% and 69% of the effluent color, respectively, even after 30 days of their continuous operation at room temperature (30 °C). Genotoxicity of textile effluent was significantly reduced after GP mediated decolorization.