Factors affecting polycyclic aromatic hydrocarbon biodegradation by Aspergillus flavus

This study investigated the ability of fungi isolated from highly contaminated soil to biodegrade polycyclic aromatic hydrocarbon (PAH) compounds, as well as the effect of several parameters on the biodegradation ability of these fungi. The isolated fungi were identified using ITS rDNA sequencing and tested using 2,6‐dichlorophinolendophenol to determine their preliminary ability to degrade crude oil. The top‐performing fungi, Aspergillus flavus and Aspergillus fumigatus, were selected to test their ability to biodegrade PAH compounds as single isolates. After 15 days of incubation, A. flavus degraded 82.7% of the total PAH compounds, with the complete degradation of six compounds, whereas A. fumigatus degraded 68.9% of the total PAHs, with four aromatic compounds completely degraded. We also tested whether different temperatures, pH, and nitrogen sources influenced the growth of A. flavus and the degradation rate. The degradation process was optimal at a temperature of 30°C, pH of 5.5, and with nitrogen in the form of yeast extract. Finally, the ability of the fungal candidate, A. flavus, to degrade PAH compounds under these optimum conditions was studied. The results showed that 95.87% of the total PAHs, including 11 aromatic compounds, were completely degraded after 15 days of incubation. This suggests that A. flavus is a potential microorganism for the degradation of PAH compounds in aqueous cultures.     

Sedimentary Record of Polycyclic Aromatic Hydrocarbons in the Gulf of Trieste (Northern Adriatic Sea)

To reconstruct a history of polycyclic aromatic hydrocarbon (PAH) pollution in the Gulf of Trieste, one of the largest urbanized areas in the Adriatic Sea, we analyzed three long sediment cores collected between 1996 and 1997. Concentrations of total PAHs, the sum of 16 PAH compounds and six of their methylated analogues, in all three cores show a decrease from 600–800 ng g⁻¹, at the surface, to levels below 250 ng g⁻¹ in deepest layers (down to 3 m). The same trend was shown with separate representative pyrogenic PAHs (pyrene, benzofluoranthene and phenanthrene). Using Hg as a recent geochronological tracer, we observe an increasing input of PAHs since the beginning of the 20th Century and, especially, after the Second World War coinciding with increasing industrialization and urbanization of the region. This correlation is supported by PAH ratios that are indication of combustion processes and represent a marker for anthropogenic inputs. No correlation exists between PAHs and black carbon within the core profiles, indicating two different fractions of the ‘black carbon continuum’.     

Effects of physicochemical factors on PAH degradation by Planomicrobium alkanoclasticum

Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants that are mutagenic, carcinogenic, and toxic to living organisms. Here, the ability and effectiveness of selected bacteria isolated from an oil‐contaminated area in biodegrading PAHs were evaluated, and the optimal conditions conducive to bacterial PAH biodegradation were determined. Of six bacterial isolates identified based on their 16S rRNA sequences, Planomicrobium alkanoclasticum could subsist on and consume nearly all hydrocarbons according to the 2,6‐dichlorophenolindophenol assay. The efficacy of this isolate at PAH biodegradation was then empirically confirmed. After 30 days of incubation, P. alkanoclasticum degraded 90.8% of the 16 PAH compounds analyzed and fully degraded eight of them. The optimum P. alkanoclasticum growth conditions were 35°C, pH 7.5, and NaNO₃ as the nitrogen source. Under these biostimulant conditions, P. alkanoclasticum degraded 91.4% of the total PAH concentration and completely decomposed seven PAHs after 15 days incubation. Hence, P. alkanoclasticum is an apt candidate for the biodegradation of PAHs and the bioremediation of sites contaminated by them.     

Sodium Persulfate Oxidation for the Remediation of Chlorinated Solvents (USEPA Superfund Innovative Technology Evaluation Program)

This study has been conducted at the University of Connecticut (UCONN) in connection with the USEPA Superfund Innovative Technology Evaluation (SITE) program to evaluate a chemical oxidation technology (sodium persulfate) developed at UCONN. A protocol to assess the efficacy of oxidation technologies has been used. This protocol, which consists of obtaining data from a treatability study, tested two in-situ chemical oxidation technologies that can be used on soil and groundwater at a site in Vernon, Connecticut. Based on the treatability report results and additional field data collected at the site, the design for the field implementation of the chemical oxidation remediation was completed. The results indicate that both sodium persulfate and potassium permanganate were able to effectively degrade the target VOCs (i.e., PCE, TCE and cis-DCE) in groundwater and soil-groundwater matrices. In the sodium persulfate tests (120 hrs), the extent of destruction of target VOCs was 74% for PCE, 86% for TCE and 84% for cis-DCE by Na₂S₂O₈ alone and 68% for PCE, 76% for TCE, and 69% for cis-DCE by Fe(II)-catalyzed Na₂S₂O₈. The results demonstrate the sodium persulfate's ability to degrade PCE, TCE and cis-DCE. It is expected that given sufficient dose and treatment time, a higher destruction rate of the dissolved phase contamination can be achieved. The data also indicates that the catalytic effect of the iron chelate on persulfate chemistry was much less pronounced in the soil-groundwater matrix. This indicates an interaction between the iron chelate solution and the soil, which may have resulted in a lower availability of the chelated iron for catalysis. The study showed that the remediation of the VOCs-contaminated soil and groundwater by in-situ chemical oxidation using sodium persulfate is feasible at the Roosevelt Mills site. As a result, the USEPA SITE program will evaluate this technology at this site.     

Sonophotocatalytic Degradation of Chitosan in the Presence of Fe(III)/H2O2 System

The degradation of chitosan by means of ultrasound irradiation and its combination with homogeneous photocatalysis (photo-Fenton) was investigated. Emphasis was given on the effect of additive on degradation rate constants. 24 kHz of ultrasound irradiation was provided by a sonicator, while an ultraviolet source of 16 W was used for UV irradiation. To increase the efficiency of degradation process, degradation system was combined with Fe(III) (2.5 × 10⁻⁴mol/L) and H₂O₂ (0.020–0.118 mol/L) in the presence of UV irradiation and the rate of degradation process change from 1.873 × 10⁻⁹−6.083 × 10⁻⁹ mol^1.7 L s⁻¹. Photo-Fenton process led to complete chitosan degradation in 60 min with the rate increasing with increasing catalyst loading. Sonophotocatalysis in the presence of Fe(III)/H₂O₂ was always faster than the respective individual processes. A synergistic effect between ultrasound and ultraviolet irradiation in the presence of Fenton reagent was calculated. The degraded chitosans were characterized by X-ray diffraction (XRD), gel permeation chromatography (GPC) and Fourier transform infrared (FT-IR) spectroscopy and average molecular weight of ultrasonicated chitosan was determined by measurements of intrinsic viscosity of samples. The results show that the total degree of deacetylation (DD) of chitosan change, partially after degradation and the decrease of molecular weight led to transformation of crystal structure. A negative order for the dependence of the reaction rate on total molar concentration of chitosan solution within the degradation process was suggested. Results of this study indicate that the presence of catalyst in the reaction medium can be utilized to reduce molecular weight of chitosan while maintaining the power of irradiated ultrasound and degree of deacetylation.     

In situ chemical oxidation of residual LNAPL and dissolved‐phase fuel hydrocarbons and chlorinated alkenes in groundwater using activated persulfate

A treatablity study (TS) was conducted to evaluate the efficacy of in situ chemical oxidation (ISCO) using activated persulfate, alone and in combination with air sparging (AS), for treating a source area contaminated with residual light nonaqueous‐phase liquid (LNAPL), dissolved‐phase fuel hydrocarbons (HCs), and dissolved‐phase chlorinated alkenes at Edwards Air Force Base (AFB), California. The TS was implemented in two phases. Phase I included injecting a solution of sodium persulfate and sodium hydroxide (NaOH) into groundwater via an existing well where residual LNAPL and dissolved‐phase contaminants were present. Because the results of Phase I indicated a limited distribution of the activated persulfate, Phase II was performed to assess whether AS could enhance the distribution of the sodium persulfate. Each phase was followed by groundwater monitoring and sampling at the injection well and at three monitoring wells, located 20 to 44 feet from the injection well. Results from Phases I and II of the TS indicated that (1) alkaline‐activated persulfate was effective in promoting the dissolution of LNAPL and the degradation of dissolved‐phase contaminants, but only at the injection well; (2) the addition of AS was effective in enhancing the radius of persulfate distribution from less than 20 feet to greater than 44 feet, and (3) persulfate alone (i.e., not in an activated state) was effective in reducing the concentrations of dissolved‐phase fuel HC and chlorinated alkenes. © 2009 Wiley Periodicals, Inc.     

Literature overview: Microbial metabolism of high molecular weight polycyclic aromatic hydrocarbons

High molecular weight polycyclic aromatic hydrocarbons (HMW PAHs) increase in hydrophobicity with increases in their molecular weight and ring angularity. Microbial strategies to deal with PAH hydrophobicity include biofilm formation, enzyme induction, and biosurfactants, the effect of which is variable on PAH metabolism depending on the surfactant type and concentration, substrate, and microbial strain(s). Aerobic HMW PAH metabolism proceeds via mineralization, partial degradation, and cometabolic transformations. Generally, bacteria and nonlignolytic fungi metabolize PAHs via initial PAH ring oxidation by dioxygenases to form cis‐dihydrodiols, which are transformed to catechol compounds by dehydrogenases and other mono‐ and dioxygenases to substituted catechol and noncatechol compounds, all ortho‐ or metacleaved and further oxidized to simpler compounds. However, lignolytic fungi form quinones and acids to CO₂. This review discusses the pathways for HMW PAH microbial metabolism. © 2008 Wiley Periodicals, Inc.     

Chemical Oxidation Performance in High Temperature,Saline Groundwater Impacted With Hydrocarbons

A series of laboratory microcosm experiments and a field pilot test were performed to evaluate the potential for in situ chemical oxidation (ISCO) of aromatic hydrocarbons and methyl tertiary butyl ether (MTBE), a common oxygenate additive in gasoline, in saline, high temperature (more than 30 °C) groundwater. Groundwater samples from a site in Saudi Arabia were amended in the laboratory portion of the study with the chemical oxidants, sodium persulfate (Na₂S₂O₈) and sodium percarbonate (Na₂(CO₃)₂), to evaluate the changes in select hydrocarbon and MTBE concentrations with time. Almost complete degradation of the aromatic hydrocarbons, naphthalene and trimethylbenzenes (TMBs), was found in the groundwater sample amended with persulfate, whereas the percarbonate‐amended sample showed little to no degradation of the target hydrocarbon compounds in the laboratory. Isotopic analyses of the persulfate‐amended samples suggested that C‐isotope fractionation for xylenes occurred after approximately 30 percent reduction in concentration with a decline of about 1 percent in the δ¹³C values of xylenes. Based on the laboratory results, pilot‐scale testing at the Saudi Arabian field site was carried out to evaluate the effectiveness of chemical oxidation using nonactivated persulfate on a high temperature, saline petroleum hydrocarbon plume. Approximately 1,750 kg of Na₂S₂O₈ was delivered to the subsurface using a series of injection wells over three injection events. Results obtained from the pilot test indicated that all the target compounds decreased with removal percentages varying between 86 percent for naphthalene and more than 99 percent for the MTBE and TMBs. The benzene, toluene, ethylbenzene, and xylene compounds decreased to 98 percent on average. Examination of the microbial population upgradient and downgradient of the ISCO reactive zone suggested that a bacteria population was present following the ISCO injections with sulfate‐reducing bacteria (SRB) being the dominant bacteria present. Measurements of inorganic parameters during injection and postinjection indicated that the pH of the groundwater remained neutral following injections, whereas the oxidation–reduction potential remained anaerobic throughout the injection zone with time. Nitrate concentrations decreased within the injection zone, suggesting that the nitrate may have been consumed by denitrification reactions, whereas sulfate concentrations increased as expected within the reactive zone, suggesting that the persulfate produced sulfate. Overall, the injection of the oxidant persulfate was shown to be an effective approach to treat dissolved aromatic and associated hydrocarbons within the groundwater. In addition, the generation of sulfate as a byproduct was an added benefit, as the sulfate could be utilized by SRBs present within the subsurface to further biodegrade any remaining hydrocarbons. ©2015 Wiley Periodicals, Inc.     

Toxicity and source assignment of polycyclic aromatic hydrocarbons in road dust from urban residential and industrial areas in a typical industrial city in Korea

This study analyzed the toxicity and sources of polycyclic aromatic hydrocarbons (PAHs) in road dust from six representative areas (three urban residential areas and three industrial areas) from a typical industrial city in Korea. The concentrations and the toxicity equivalent concentrations (TEQs) in road dust varied by area, depending on the type of traffic and industrial activities and the PAHs identified. High correlations between the total concentration and the TEQ of PAHs in road dust were found in road dust from both the urban and industrial areas. To identify the sources of PAHs, this study utilized a factor loading method in a principal component analysis, the ratio of PAHs from combustion sources to total PAHs (ΣCOMB to ΣPAH), and bivariate plots of phenanthrene/anthracene (PA/Ant) versus fluoranthene/pyrene (FL/Pyr), and ΣCOMB/ΣPAH versus FL/Pyr in road dust. The identified origin of the PAHs was fuel combustion, including gasoline, diesel, oil, and coal, used in urban and industrial areas.     

Polychloroprene Degradation by Photo-Fenton. Conductivity Measures as New Approach for Detecting/Evaluation of Degradation Products

In the present work the photo-degradation of polychloroprene (PCP) in toluene solution catalyzed by FeCl₃·6H₂O and polychromatic light was investigated based on FTIR and ¹³C NMR spectroscopies, on conductivity measurements and DSC technique. The band in the 1700–1790 cm⁻¹ range in the FTIR spectrum characterized the presence of carbonyl products due to the degradation of the PCP on the solution exposed to polychromatic light. The formation of carbonyl on degraded PCP was confirmed by the presence of signal on ¹³C NMR at δ 203.5. Products of PCP degradation, such as acid chlorides, generated in the toluene solution migrate to the aqueous phase (in contact with toluene phase) and the conductivity of aqueous phase increased as the time is elapsed. The area related to the PCP melting-peak on the DSC (film casted after the PCP-FeCl₃·6H₂O toluene solution has been exposed to polychromatic light) significantly decreased in comparison to that in the DSC of the raw PCP cast film.     

The in situ treatment of BTEX,MTBE, and TBA in saline groundwater

A pilot‐scale test was conducted in a saline aquifer to determine if a petroleum hydrocarbon (PHC) plume containing benzene (B), toluene (T), ethylbenzene (E), xylenes (X), methyl tert‐butyl ether (MTBE), and tert‐butyl alcohol (TBA) could be treated effectively using a sequential treatment approach that employed in situ chemical oxidation (ISCO) and enhanced bioremediation (EBR). Chemical oxidants, such as persulfate, have been shown to be effective in reducing dissolved concentrations of BTEX (B + T + E + X) and additives such as MTBE and TBA in a variety of geochemical environments including saline aquifers. However, the lifespan of the oxidants in saline environments tends to be short‐lived (i.e., hours to days) with their effectiveness being limited by poor delivery, inefficient consumption by nontargeted species, and back‐diffusion processes. Similarly, the addition of electron acceptors has also been shown to be effective at reducing BTEX and associated additives in saline groundwater through EBR, however EBR can be limited by various factors similar to ISCO. To minimize the limitations of both approaches, a pilot test was carried out in a saline unconfined PHC‐impacted aquifer to evaluate the performance of an engineered, combined remedy that employed both approaches in a sequence. The PHC plume had total BTEX, MTBE, and TBA concentrations of up to 4,584; 55,182; and 1,880 μg/L, respectively. The pilot test involved injecting 13,826 L of unactivated persulfate solution (19.4 weight percent (wt.%) sodium persulfate (Na₂S₂O₈) solution into a series of injection wells installed within the PHC plume. Parameters monitored over a 700‐day period included BTEX, MTBE, TBA, sulfate, and sulfate isotope concentrations in the groundwater, and carbon and hydrogen isotopes in benzene and MTBE in the groundwater. The pilot test data indicated that the BTEX, MTBE, and TBA within the PHC plume were treated over time by both chemical oxidation and sulfate reduction. The injection of the unactivated persulfate resulted in short‐term decreases in the concentrations of the BTEX compounds, MTBE, and TBA. The mean total BTEX concentration from the three monitoring wells within the pilot‐test area decreased by up to 91%, whereas MTBE and TBA mean concentrations decreased by up to 39 and 58%, respectively, over the first 50 days postinjection in which detectable concentrations of persulfate remained in groundwater. Concentrations of the BTEX compounds, MTBE, and TBA rebounded at the Day 61 marker, which corresponded to no persulfate being detected in the groundwater. Subsequent monitoring of the groundwater revealed that the concentrations of BTEX continued to decrease with time suggesting that EBR was occurring within the plume. Between Days 51 and 487, BTEX concentrations decreased an additional 84% from the concentration measured on Day 61. Mean concentrations of MTBE showed a reduction during the EBR phase of remediation of 33% while the TBA concentration appeared to decrease initially but then increased as the sulfate concentration decreased as a result of MTBE degradation. Isotope analyses of dissolved sulfate (³⁴S and ¹⁸O), and compound‐specific isotope analysis (CSIA) of benzene and MTBE (¹³C and ²H) supported the conclusions that ISCO and EBR processes were occurring at different stages and locations within the plume over time.     

Effect of Metal Oxide Catalysts on Degradation of Waste Polystyrene in Hydrogen at Elevated Temperature and Pressure in Benzene Solution

Degradation of waste polystyrene is carried out in presence of hydrogen using several metal oxide catalysts at elevated temperature and pressure for recycling. Benzene is used as a solvent for degradation. Initial hydrogen pressure in the autoclave is kept at 7.0 kg/cm² (g) and polystyrene degradation is carried out at 240 °C. After degradation, degraded polystyrene residue is separated and analyzed by Fourier transform infra red (FTIR) spectroscopy whereas filtrate is analyzed by gas chromatography (GC) for finding the degradation mechanism of polystyrene. Degradation rate is enhanced in presence of hydrogen and time dependent weight average molecular weight of degraded polystyrene is determined using viscosity method. Degradation rate constants for the different catalysts are calculated based on the proposed degradation mechanism. Alkali metal oxide catalyst shows higher reactivity towards polystyrene degradation as compare to the transition metal oxide catalyst i.e., degradation rate constant decreases with the increase in electro negativity of metal element of the catalyst. Though manganese (IV) oxide is a transition metal catalyst, but shows higher reactivity due to its reduction towards stable manganese (II) oxide under degradation environment. Finally, degradation rate constant of polystyrene is correlated with the catalyst activity i.e., electro negativity of metal element in the catalyst.     

Demonstrating Contaminant Degradation at an MGP Site With Metabolic Gas Flux and Radio Carbon Dating

Obtaining lines of evidence indicating that contamination in sediment environments is degrading and being transformed to less toxic forms is an important component of building support for a monitored natural recovery remedy for contaminated sediments. This project was a field demonstration of manufactured gas plant contaminant degradation in river sediments using metabolic gas flux and was performed in an urban area section of a river in northeastern Indiana. CO₂ sorbent traps were deployed to measure CO₂ flux from the river sediments. Sediment samples were collected and analyzed for polycyclic aromatic hydrocarbon (PAH) concentrations and for microbial community composition using molecular techniques. The results showed that the deployment was successful, measuring CO₂ flux at all sediment locations and demonstrating that microbial contaminant degrading activity was occurring in the sediments. Radio carbon dating showed a significant portion of the CO₂ being generated (approximately 19–27 percent) was the result of fossil fuel degradation. Molecular results showed that the microbial community consisted of phylotypes known to be associated with monocyclic aromatic and PAH degradation. ©2017 Wiley Periodicals, Inc.     

Arrested municipal solid waste incinerator fly ash as a source of polynuclear aromatic hydrocarbons (PAHs) to the environment

Arrested fly ash samples from most currently operating municipal solid waste (MSW) incinerators on the U.K. mainland have been analysed for polynuclear aromatic hydrocarbons (PAHs). The ashes have a mean ΣPAH content of about 227 μg kg⁻. This is generally lower than concentrations observed in U.K. surface soils. Benzo[ghi] perylene was the most abundant individual compound, and the most frequently detected. The ΣPAH content of ashes does not appear to be related to incinerator type, but rather it is likely that poor gas phase combustion favours higher PAH levels. The significance of PAHs in ash residues and their possible fate following disposal to landfill are discussed.     

Influence of Carbonyl Fe on Degradation of Epoxy in Ozone Environment

Carbonyl iron/epoxy coatings are widely used in military as a radar absorbing coating (RAC). The behaviors of RACs under working environments are very important, especially in the new environments such as ozone appeared with widening of the application fields. The effects of ozone degradation on pure epoxy cured with anhydride and the influence of carbonyl Fe on the degradation of epoxy are studied. The results indicate that if the peak at 1,510 cm⁻¹ was used as the inner standard, the intensity of absorption peaks at 1,738, 1,247 and 1,182 cm⁻¹ increases with exposure time for pure epoxy resin, while for the carbonyl iron/epoxy coatings, the three peaks changes insignificantly with the exposure time. The results indicates the oxidation process begins at the hydroxyl and methyl groups, and finally ozonide and carbonyl are formed on the surface for pure epoxy, and epoxy is eroded gradually in depth by ozone. Carbonyl iron could hinder the meeting of ozone with epoxy with dilution or hindrance effect and could protect epoxy resin from ozone and thus delay the deterioration of the coating performance.     

Characterisation of polycyclic aromatic hydrocarbons in flue gas and residues of a full scale fluidized bed combustor combusting non-hazardous industrial waste

This paper studies the fate of PAHs in full scale incinerators by analysing the concentration of the 16 EPA-PAHs in both the input waste and all the outputs of a full scale Fluidized Bed Combustor (FBC). Of the analysed waste inputs i.e. Waste Water Treatment (WWT) sludge, Refuse Derived Fuel (RDF) and Automotive Shredder Residue (ASR), RDF and ASR were the main PAH sources, with phenanthrene, fluoranthene and pyrene being the most important PAHs. In the flue gas sampled at the stack, naphthalene was the only predominant PAH, indicating that the PAHs in FBC’s combustion gas were newly formed and did not remain from the input waste. Of the other outputs, the boiler and fly ash contained no detectable levels of PAHs, whereas the flue gas cleaning residue contained only low concentrations of naphthalene, probably adsorbed from the flue gas. The PAH fingerprint of the bottom ash corresponded rather well to the PAH fingerprint of the RDF and ASR, indicating that the PAHs in this output, in contrast to the other outputs, were mainly remainders from the PAHs in the waste inputs. A PAH mass balance showed that the total PAH input/output ratio of the FBC ranged from about 100 to about 2600 depending on the waste input composition and the obtained combustion conditions. In all cases, the FBC was clearly a net PAH sink.     

Selective Lead(II) Adsorption and Flocculation Characteristics of the Grafted Sodium Alginate: A Comparative Study

Synthesis of sodium alginate-g-poly(acrylamide-co-N-methylacrylamide) [S-III], sodium alginate-g-poly(N-methylacrylamide-co-N,N-dimethylacrylamide) [S-II], sodium alginate-g-poly(acrylamide-co-N,N-dimethylacrylamide) [S-I]. Sodium alginate-g-poly(N,N-dimethylacrylamide) [SAG-g-PDMA] and sodium alginate-g-poly(acrylamide) [SAG-g-PAM] were prepared by solution polymerization technique using potassium peroxydisulfate as the initiator at 70?°C in water medium. The graft copolymers were characterized by FTIR and NMR (¹H and ¹³C) spectroscopy, SEM and XRD studies. All the five graft copolymers were used to remove Pb(II) ions from the aqueous solution and also in flocculation studies of kaolin clay (1.0 wt%), silica (1.0 wt%) and iron ore slime (0.25 wt%) suspensions. A comparative studies of all the five graft copolymers were also made in both the two cases. The Pb(II) ion removal capacity of all the graft copolymers follows the order S-III?>?SAG-g-PAM?>?S-II?>?SAG-g-PDMA?>?S-I. But the flocculation performance of the graft copolymers follows the order S-II?>?S-I?>?S-III?>?SAG-g-PDMA?>?SAG-g-PAM. S-III was also used for the competitive metal ion removal with Hg(II), Cd(II), Cu(II) and Zn(II). Pb(II) adsorption of S-III (the best Pb(II) ion adsorber) follows pseudo second order rate equation and Langmuir adsorption isotherm.     

Biodegradable Polymers from 5-Hydroxylevulinic Acid: 1. Synthesis and Characterization of Poly(5-hydroxylevulinic acid)

As an attempt to synthesize new biodegradable polymers from renewable cellulose resources, melt polycondensation of 5-hydroxylevulinic acid (5-HLA) was reported for the first time. The resulting product, poly(5-hydroxylevulinic acid) (PHLA), was synthesized and characterized with GPC, FTIR, ¹H NMR and DSC. The in vitro degradation behaviors in phosphate-buffered saline (PBS) and in deionized water (DW) were also examined. The molecular weight of PHLA is not high (several 1,000s), but it possesses unordinary high glass transition temperature (as high as 120 °C). This is very different from existing aliphatic polyesters that usually have T _gs lower than 60 °C. The high T _g is attributed to the formation of inter- and/or intramolecular hydrogen bonds due to a characteristic keto–enol tautomerism equilibrium in the polymer structure. PHLA readily degraded hydrolytically in aqueous media.     

Electrolytic oxidation studies of 2,2′-dichlorobiphenyl using ruthenium oxide electrodes, persulfate oxidizers, and UV irradiation

A three probe potentiostat was used to control the potential to a catalytic ruthenium oxide anode in oxidation studies of 2,2′-dichlorobiphenyl (2,2′). Voltages applied varied in one volt increments from 2.0 to 4.0 volts. Studies involved determination of the optimum voltage operating in conjunction with added sodium persulfate oxidizers (0.002 M and 0.018 M) and various exposure times (1 and 8 h) to ultra-violet (254.7 nm) provided by a General Electric BH-6 high pressure mercury arc lamp. The oxidation products of 2,2′ consisted of four compounds. The primary product was 2-chloro, 2′-hydroxyl biphenyl. Other products included: 2-acetoxy, 2′chlorobiphenyl (as previously observed by Laule et al, Journal of Electroanalytical Chemistry, 213: 329–332 (1986)), and dibenzofuran and 5,5′ dichlorodibenzofuran. All products were confirmed using a combination of GC and GC/MS. No reduction in 2,2′ concentration was observed in any of the control solutions in the absence of an applied voltage. Additionally, the presence of an oxidizer and UV irradiation aided the oxidation of 2,2′-dichlorobiphenyl. The oxidation percentage of the 2,2′ at 5 ppm was in the range of 70% under the optimum conditions of applied potential (3.0 volts), persulfate concentration (0.018 M), and UV exposure time (8 h). All reaction conditions and analysis procedures are described.     

In-Situ Phytoremediation of Pahs Contaminated Soils Following a Bioremediation Treatment

Phytoremediation of pollutants in soils is an emerging technology, using different soil-plant interaction properties. For organic pollutants, such as polycyclic aromatic hydrocarbons (PAHs), phytodegradation seems to be the most promising approach. It occurs mostly through an increase of the microbial activity in the plant rhizosphere, allowing the degradation of organic substances, a source of carbon for soil microbes. Despite a large amount of available data in the literature concerning laboratory and short term PAH phytodegradation experiments, no actual field application of such technique was previously carried out. In the present study, a soil from a former coking plant was used to evaluate the feasibility and the efficiency of PAH phytodegradation in the field during a three years trial and following a bioremediation treatment. Before the phytoremediation treatment, the soil was homogenized and split into six independent plots with no hydrological connections. On four of these plots, different types of common plant species were sowed: mixture of herbaceous species, short cut (P1), long cut (P2), ornamental plants (P3) and trees (P4). Natural vegetation was allowed to grow on the fifth plot (P5), and the last plot was weeded (P6). Each year, representative sampling of two soil horizons (0–50 and 50–100 cm) was carried out in each plot to characterize the evolution of PAHs concentration in soils and in soils solution obtained by lixiviation. Possible impact of the phytoremediation technique on ecosystems was evaluated using different eco- and genotoxicity tests both on the soil solid matrix and on the soil solution. For each soil horizon, comparable decrease of soil total PAHs concentrations were obtained for three plots, reaching a maximum value of 26% of the initial PAHs concentration. The decrease mostly concerned the 3 rings PAHs. The overall low decrease in PAHs content was linked to a drastic decrease in PAHs availability likely due to the bioremediation treatment. However, soil solutions concentration showed low values and no signficant toxicity was characterized. The mixture of the herbaceous species seemed to be the most promising plants to be used in such procedure.