Tetrachloroethylene Research Articles

Occupational exposure assessment to per and trichloroethylene in dry cleaning in Sfax city (Tunisia)

Abstract The use of chlorinated solvents in dry cleaning poses risks to human health. The current study is the first in Tunisia and Sfax city that aims to assess the occupational exposure and health risks of perchloroethylene (PCE) and trichloroethylene (TCE) in the dry cleaning industry. TCE was suspected to be used as it is not explicitly banned by law. We identified dry cleaning facilities by door-to-door canvassing within a 5 Km radius from the city center of Sfax. We found 47 facilities, but only 33 accepted to join our study. Then, we randomly selected 16 facilities where the exposure assessment to these solvents was conducted by indoor air measurements. The exposure levels were compared to occupational exposure limit values (OELV) and toxicological reference values. Then, cancer risks were evaluated. TCE was detected in all workplaces and their levels are close to the OELV (95% CI of the mean value [40.4-46 mg/m3]). The mean value of PCE concentrations is lower than the fifth of the OELV, but they are quite variable (95% CI of the mean value [5.1-43.4 mg/m3]). The overall results showed that inhalation exposure levels may induce many adverse effects that are probably threatening the occupationally exposed population and even the general one, because of the location of all facilities in residential settings. Among threshold effects, we noted high risks of neurological, renal, developmental and immune effects. As for carcinogenic effects, greatly high cancer risks were noticed if the lifetime exposure would have these average levels; 17 additional cases of kidney, hematologic or liver cancers are expected to occur in populations of 100. This study is significant for better understanding of the dry cleaning industrial sector in Tunisia and for the progress of future risk assessment studies. Indeed, it responded to many interrogations and suspicions about the qualitative and quantitative exposure conditions and thus the health status of dry cleaning workers in Sfax. Key messages Our study is the first health risk assessment study of the exposure to chlorinated solvents in dry cleaning in Sfax city. It revealed high levels of trichloroethylene that is a carcinogen to humans. The high exposure levels to per and tri-chloroethylene, in dry cleaning in Sfax city, may induce adverse health effects to workers and even the general population due to residential exposure.

Perchloroethylene (PCE) adsorption on coal macerals as derived from micro-FTIR spectroscopic analysis and mapping of the C=C bonds from PCE

ABSTRACT Organic liquids are used to prepare the density medium to produce clean coal composites for coal quality and coking test evaluations during the coal exploration stage. Perchloroethylene (PCE) is commonly used as a density medium for this procedure; however, it has been shown before that PCE affects Gieseler Fluidity and Ruhr Dilatation indices of coal, as well as the quality of the resulting coke. It was also found that PCE has a negative effect on the coking properties of coals with a high inertinite content. This paper investigates the adsorption of PCE on various coal maceral surfaces using micro-Fourier Transform Infrared Spectroscopy (micro-FTIR) analysis to observe the changes in the absorbance of the double carbon bond C = C (C = C absorbance peak is used as a marker to indicate the presence of PCE) before and after PCE was applied onto their surfaces. The micro-FTIR mapping of absorbance intensity of the C = C bond on coal macerals showed an increasing trend in the presence of these bonds on the surface of all macerals with the time after exposure to the PCE. The SEM- energy-dispersive X-ray spectroscopy was used to analyze the composition of minerals associated with fusinite and semifusinite, as they were filling the pores in these macerals.

Integrative isotopic and molecular approach for the diagnosis and implementation of an efficient in-situ enhanced biological reductive dechlorination of chlorinated ethenes

Based on the previously observed intrinsic bioremediation potential of a site originally contaminated with perchloroethene (PCE), field-derived lactate-amended microcosms were performed to test different lactate isomers and concentrations, and find clearer isotopic and molecular parameters proving the feasibility of an in-situ enhanced reductive dechlorination (ERD) from PCE-to-ethene (ETH). According to these laboratory results, which confirmed the presence of Dehalococcoides sp. and the vcrA gene, an in-situ ERD pilot test consisting of a single injection of lactate in a monitoring well was performed and monitored for 190 days. The parameters used to follow the performance of the ERD comprised the analysis of i) hydrochemistry, including redox potential (Eh), and the concentrations of redox sensitive species, chlorinated ethenes (CEs), lactate, and acetate; ii) stable isotope composition of carbon of CEs, and sulphur and oxygen of sulphate; and iii) 16S rRNA gene sequencing from groundwater samples. Thus, it was proved that the injection of lactate promoted sulphate-reducing conditions, with the subsequent decrease in Eh, which allowed for the full reductive dechlorination of PCE to ETH in the injection well. The biodegradation of CEs was also confirmed by the enrichment in 13C and carbon isotopic mass balances. The metagenomic results evidenced the shift in the composition of the microbial population towards the predominance of fermentative bacteria. Given the success of the in-situ pilot test, a full-scale ERD with lactate was then implemented at the site. After one year of treatment, PCE and trichloroethene were mostly depleted, whereas vinyl chloride (VC) and ETH were the predominant metabolites. Most importantly, the shift of the carbon isotopic mass balances towards more positive values confirmed the complete reductive dechlorination, including the VC-to-ETH reaction step. The combination of techniques used here provides complementary lines of evidence for the diagnosis of the intrinsic biodegradation potential of a polluted site, but also to monitor the progress, identify potential difficulties, and evaluate the success of ERD at the field scale.

Electrochemical Behavior of Lithium Chloride/Polymer Hybrid Layer Coated Lithium Powder Anode

Lithium metal anode is considered to be ultimate anode material because of its high theoretical specific capacity(3860mAh/g) and low redox potential(-3.04V vs H/H+). However, lithium metal suffers from dendrite growth and low coulombic efficiency. Lithium metal powder synthesized by droplet emulsion technique has 6 times higher surface area than lithium foil. So it can lower the effective current density thus prevent the dendrite growth. However, low coulombic efficiency still exists due to unstable Solid Electrolyte Interphase(SEI) layer. Here in, we propose a stable artificial protection layer to lithium powder anode by using perchloroethylene(PCE). PCE reacts with LiOH which is naturally passivated on lithium surface. Then, LiCl nanoparticle within the polymer matrix will form on the surface and act as a high lithium conducting, flexible artificial layer. The structure, morphology, and electrochemical properties will be investigated by the implementation of X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), and energy dispersive spectroscopy (EDS). The result was analyzed by electrochemical impedance spectroscopy (EIS).

Evaluation of Occupational Exposure to Perchlorethylene in a Group of Italian Dry Cleaners Using Noninvasive Exposure Indices.

Recent data suggest a general trend in decreased occupational exposure to perchlorethylene (PCE) in the dry-cleaning sector. The aims of this study were to confirm this trend to lower exposure levels in a group of Italian dry cleaners and to evaluate the current occupational PCE exposure in these works using noninvasive biological indices. Environmental exposure was assessed by personal sampling in 60 operators working in 21 dry cleaning shops in North Italy. PCE in the exhaled alveolar air (PCEalv), urinary concentration of PCE and of trichloroacetic acid (TCA) (PCEu and TCAu respectively), were measured as biological exposure indices. Median PCE environmental concentration in the whole sample was 10.6 mg/m3 (i.e., less than the 25% of the levels measured in the same area in a previous study). All values were less than 10% of the occupational limits. PCEu measured in samples collected at the end of the work shift resulted the biological markers having the strongest correlation with environmental PCE (r = 0.81). PCEalv also resulted in a high correlation (r = 0.66), while a lower correlation was found for TCAu measured at the end shift (r = 0.32). According to our results, PCEu can be proposed as a valid, noninvasive, and easily reliable exposure index to evaluate PCE exposure at the low levels currently observed in dry cleaners, therefore representing a promising alternative to invasive blood sample collections needed to determine PCE blood concentration.

Effect of Residual NAPLs on the Transport of Bisphenol A and Bisphenol S in Saturated Porous Media

Endocrine disrupter, like bisphenol A (BPA) and bisphenol S (BPS), is frequently detected in the subsurface environment, imposing threats to the groundwater quality and public health. However, current understanding of environmental fate and transport of BPA/BPS is still not clear, especially with respect to those in the subsurface media with trapped non-aqueous phase liquids (NAPLs). In this study, the effect of residual NAPLs on the retention and transport of BPA/BPS in the saturated sand and soil media was investigated using column experiments. The results showed that residual NAPLs (i.e., xylene and perchloroethylene (PCE)) inhibited the transport of BPA in the sand columns, and the inhibit effect of xylene was greater than that of PCE. While the presence of NAPLs showed little influence on the transport of BPS in the sand columns, in soil A (sandy soil), the residual NAPLs had similar effect on the retention and transport of BPA and BPS. Both BPA and BPS showed higher retention in the soil B columns than in the sand and soil A columns due to soil B’s higher organic matter contents, which can strongly sorb BPA/BPS. The presence of residual NAPLs reduced the retention of BPA/BPS in the soil B columns because the NAPLs blocked the sorption sites of the soil organic matter for BPA/BPS. This study demonstrates the importance of residual NAPLs, types of media, properties of contaminants, and their interactions to the fate and transport of BPA/BPS in saturated porous media.

The Effect of Perchloroethylene (PCE) Exposure Toward Frequency of Micronucleus Formation in Buccal Mucosal Ephitelia of Dry Cleaning Employees

Background: Perchloroethylene is one of the main ingredients used in the dry cleaning industry. Continuous inhalation of Perchloroethylene particles can cause genetic damage that can be marked by the appearance of micronucleus. Micronucleus formation of excessive buccal mucosal is one of the early signs of malignancy in the oral cavity.
 Objective: To determine the effect of Perchloroethylene exposure toward frequency of micronucleus formation in buccal mucosal epithelial of dry cleaning employees in Banyumas Regency.
 Materials & methods: This study uses cross-sectional design with primary data that is the preparation of buccal mucosal smear from 22 dry cleaning employees as exposed group and 22 subjects are not exposed to Perchloroethylene as control group. The buccal epithelial cells are collected using a spatula and then smeared on an object glass and colored using Giemsa. Micronuclear frequencies are calculated per 1000 cells using a light microscope.
 Results: The difference of micronucleus frequency between two groups (p = 0.000) is obtained. The duration of work has correlation with medium correlation strength to the forming frequency of micronucleus formation, whereas age has strong correlation to the forming frequency of micronucleus formation. The correlation between age and work duration with the forming frequency of micronucleus formation is significant (p = 0.000 and p = 0.07)
 Conclusions: There is influence of Perchloroethylene exposure toward frequency of micronucleus formation. The duration of work and age are significantly correlated with the forming frequency of micronucleus formation.
 J MEDICINE JUL 2019; 20 (2) : 59-62

The influences of ionic strength and permeability on DNAPLs representative elementary volume in porous media

Dense nonaqueous phase liquids (DNAPLs) have led to widely distributed groundwater contamination due to their widespread applications and accidental spills. To investigate influences of two factor-ionic strength and permeability on the representative elementary volume (REV) of DNAPL, four experiments are conducted in two-dimensional (2D) porous media to investigate perchloroethylene (PCE) migration and associated REVs. The permeability and ionic strength of four experiments are set as different schemes. PCE migration and REVs are estimated by moment analysis and the criteria of the relative gradient error (εgi). Results suggest that the permeability and ionic strength are of significant effects on REVs of PCE. Higher permeability of porous media can promote the vertical infiltrate rate of PCE in aquifer. Simultaneously, higher ionic strength can lower the second moments of PCE plume and increase the GTP of PCE mass. More importantly, higher permeability has increased the REV of PCE saturation (So) with absolute errors of 1.35 mm and 2.71 mm under conditions of low and high ionic strength. Besides, higher permeability has decreased the REV of PCE-water interfacial area (AOW) with absolute errors of 2.76 mm and 1.09 mm under conditions of low and high ionic strength. What’s more, ionic strength has no apparent effects on So-REV sizes when permeability is high (absolute error equals to 0.16 mm between low and high ionic strength). However, high ionic strength can decrease the minimum REV sizes of So when permeability is low (absolute error is 1.52 mm). Moreover, high ionic strength can increase minimum REV sizes of AOW with absolute errors of 1.49 mm and 1.01 mm under conditions of high and low permeability. These findings can improve the understanding of DNAPLs behaviors in subsurface environment under complex condition.

Hydroxyl radical and non-hydroxyl radical pathways for trichloroethylene and perchloroethylene degradation in catalyzed H2O2 propagation systems

Catalyzed H2O2 propagations (CHP) is characterized by the most robust reactivity of any of the in situ chemical oxidation (ISCO) technologies because it generates the strong oxidant hydroxyl radical along with nucleophiles + reductants, such as superoxide radical. The most common groundwater contaminants, trichloroethylene (TCE) and perchloroethylene (PCE), were used as model contaminants in evaluating the effect of hydrogen peroxide (H2O2) dosage on contaminant destruction kinetics. Both TCE and PCE degradation rates increased with H2O2 dosages up to 0.1 M, and then decreased with higher H2O2 dosages. Parallel reactions conducted with the addition of the hydroxyl radical scavenger 2-propanol and the hydroxyl radical-specific probe nitrobenzene confirmed that hydroxyl radical is primarily responsible for TCE and PCE degradation; however, 5–20% of their degradation was attributed to a non-hydroxyl radical mechanism. Reactions conducted with the superoxide probe tetranitromethane showed that superoxide generation rates increased with increasing H2O2 doses. These results were confirmed by electron spin resonance spectroscopy. Therefore, the non-hydroxyl radical pathway for TCE and PCE degradation at H2O2 ≥0.5 M was likely via nucleophilic attack by superoxide. The results of this research demonstrate that contaminants present in the aqueous phase that are reactive with hydroxyl radical require only low doses of H2O2 (≤0.1 M), but subsurface systems contaminated with species not reactive with hydroxyl radical (e.g., carbon tetrachloride) require H2O2 concentrations ≥0.5 M.

In-situ reductive degradation of chlorinated DNAPLs in contaminated groundwater using polyethyleneimine-modified zero-valent iron nanoparticles

Zero-valent iron nanoparticles (ZVIN) have found applications in many strategies for on-site soil and groundwater decontamination. A number of studies have reported the prospective utilization of ZVIN in the reduction of chlorinated organic compounds such as dense non-aqueous phase liquids (DNAPLs) in groundwater. Due to their bioaccumulation and carcinogenesis, DNAPLs in groundwater are a human health hazard and pose environmental risks. Therefore, decontamination of these contaminants is necessary. This study presents the in-situ remediation of trichloroethylene (TCE), perchloroethene (PCE), and 1,2-dichloroethene (1,2–DCE) DNAPLs through the direct injection of polyethylenimine (PEI)-coated ZVIN (PEI–ZVIN composite materials) to facilitate the reduction of contaminants in low-permeability media. A field test was conducted at the premises of a petrochemical company, situated in the Miaoli County of Northern Taiwan that discharged significant amounts of DNAPLs. After in-situ injection and one-day of reaction with groundwater contaminants, ZVIN was further characterized to examine its efficacy in the reduction of pollutants. After the direct injection of PEI–ZVIN, a notable reduction in the concentration of DNAPLs was recorded with conversion from toxic to non-toxic substances. Use of resistivity image profiling (RIP) technique suggested similar conductivity data for the PEI-coated ZVIN suspension and groundwater samples. X-ray absorption near edge structure (XANES) and X-ray absorption fine structure (EXAFS) studies depicted that the oxidation of ZVIN and PEI–ZVIN was occurring after the reductive reaction with contaminated groundwater. The reacted samples had bond distance values of 1.98, 2.00, 1.96, and 1.94 Å. Combining floating surface-coated ZVIN and RIP technique seems promising and environmentally attractive.

Numerical modelling of the impact of surfactant partitioning on surfactant-enhanced aquifer remediation

The partitioning of surfactants into non-aqueous phase liquids (NAPLs) during Surfactant-Enhanced Aquifer Remediation (SEAR) is potentially an important and non-negligible phenomenon that can strongly impact remediation efficiency. This paper numerically investigates the impact of surfactant partitioning on the enhanced NAPL dissolution and mobilization mechanisms and the overall NAPL removal from the subsurface. For demonstration, a multiphase model is used to simulate a hypothetical SEAR consisting of Triton X100 surfactant solution for the removal of perchloroethylene (PCE) entrapped in contaminated porous medium at the core/column scale. The simulations are conducted for two-dimensional homogenous and three-dimensional heterogeneous systems. By simultaneously incorporating spatial heterogeneity of porous media, injection rate, and endpoint mobility ratio into the model, we delineate the interplay of surfactant partitioning with flow and transport dynamics. Our results show that surfactant partitioning from the aqueous phase across the interface to the NAPL phase can undermine both efficiency of the enhanced dissolution and mobilization of NAPL species. This undermining is more pronounced for when aqueous phase mobility is less than the mobility of the NAPL phase. For such conditions interfacial tension between the two phases is reduced less for partitioning than non-partitioning cases (due to loss of surfactant into NAPL phase) and a secondary water front is formed due to partitioning that makes aqueous phase breaks through earlier.

Reductive dechlorination of perchloroethene (PCE) and bacterial community changes in a continuous-flow, two-stage anaerobic column

This study is aimed at investigating the performance of the continuous-flow, two-stage anaerobic column for the reductive dechlorination of perchloroethene (PCE) in a trichloroethene (TCE)-contaminated aquifer without bioaugmentation. Results indicated that complete dechlorination of PCE to cis-dichloroethene (DCE) was observed within the first 12 days after the addition of lactate and PCE (620:1 mg mg−1 mass ratio). The PCE conversion to ethene was initially observed in the 2nd column after 70 days (during phase II) upon the increase of lactate to PCE mass ratio to 5000:1 (mg mg−1). However, the degradation of PCE to ethene occurred in the 1st column after 30 days operation of phase IV (217–310 d) under the high PCE feed conditions (33.65 ± 2.86 μM). 16S rDNA clone library sequence analysis confirmed that Dehalobacter sp., Desulfuromonas sp., Desulfovibrio sp. Geobacter sp., Methanosaeta sp., Methanobacterium paludism, and M. spelaei were the dominant species in the original aquifer, and their relative abundance were further changed following lactate addition. Dehalococcoides mccartyi sequences were retrieved after lactate stimulation. Overall, the continuous-flow, two-stage anaerobic column process exhibited the maximum dechlorination (6.23 μmol L−1 hr−1) of PCE without bioaugmentation, indicating its potential up-scaling application in PCE dechlorination.

Removal of non-aqueous phase liquids (NAPLs) from TPH-saturated sandy aquifer sediments using in situ air sparging combined with soil vapor extraction

Contamination in coastal aquifer plains is of great concern in many countries given that non-aqueous phase liquids (NAPLs) have polluted numerous sites through accidental oil spills or improper disposal. We have developed a method to remove pollutants such as NAPLs from sandy sediment samples collected from the Mandol area of Gomso Bay in western South Korea. The sediments were collected from around the diffuser in a two-dimensional (2D) acrylic reaction apparatus, and these contained a total petroleum hydrocarbon (TPH) concentration of 89.3 ppm (mg/kg media). The maximum perchloroethylene (PCE) concentration was 398.51 ppm in the unsaturated zone and 0.77 ppm in the saturated zone. Volatile organic compounds (VOCs) were detected between 20 and 44 hour. However, non-volatile contaminants remained in the sediments after treatment. In situ air sparging (IAS) combined with soil vapor extraction (SVE), transformation from sorbed and nonaqueous phases to the vapor phase, is incomplete when treatment is performed using a pervasive air flow for sediments such as the sand of Mandol. During air transformation, the groundwater flow conditions increased the rate of contaminant removal. Although pilot-scale testing in the field site was fluctuated due to the heterogeneous of sediments condition, this 2D study found that the proposed method can alter the measurable geophysical properties of NAPLs. These findings demonstrate that IAS combined with SVE in the saturated zone is an effective technology for aquifer remediation high applicability of sandy coastal sediments contaminated by NAPLs.

Distributional analysis for understanding geochemical processes affecting ground and surficial waters in different geological conditions

The aim of this contribution is to investigate whether the study of frequency distribution, representing chemical reactions or geochemical processes, is able to provide useful information on the dynamics affecting ground and surficial waters. To reach this goal we started to explore the behaviour of the main solutes and common contaminants, by means of distributional analysis. In fact, the shape of the frequency distribution in geochemical variables reveals important information about the governing dynamics of the system that gave birth to the distribution. Moreover, the distribution shape, when plurimodality is pointed out, can be used to approximate the shape of different basins of attraction of the concentration valuesand this allows us to make helpful observations about the resilience of the system taken into account. Two application examples are presented, the first one for Perchloroethylene (PCE) concentration in groundwater of Firenze-Prato-Pistoia (Tuscany Region) alluvial plain and the second one for the chemistry of the surficial waters of the Alpine region.

Comparative investigation of argon and argon/oxygen plasma performance for Perchloroethylene (PCE) removal from aqueous solution: optimization and kinetic study.

PurposeThe aim of this study is evaluation of the perchloroethylene degradation from aqueous solutions by non-thermal plasma produced in dielectric barrier discharge reactor in two different scenarios: first plasma generated with 225 cc/min mixture of oxygen and argon flow (12% gas ratio of O2/Ar), and in the second scenario plasma generated with 225 cc/min of pure argon gas.MethodsDesign studies were performed using response surface methodology and central composite design. All experiments with the selected levels of independent parameters including the initial concentration of perchloroethylene (5–100 mg/L), voltage (20–5 kv) and contact time (15–180 s) was implemented, and 29 tests were proposed by using response surface methodology and central composite design was performed in two experimental scenarios.ResultsResults showed that the Pseudo first-order kinetics coefficient of perchloroethylene degradation in the mixture of oxygen and argon and pure argon scenario under the optimum conditions were 0.024 and 0.016 S−1 respectively. Results conveyed that in order to achieve the highest removal efficiency (100%), the values of contact time, perchloroethylene concentration and voltage variables were predicted 169.55 s, 74.3 mg/l, 18.86 kv respectively in mixture of oxygen and argon scenario and also were predicted 203 s, 85.22 mg/l, 20.39 kv respectively in pure argon scenario.ConclusionsIn the recent study dielectric barrier discharge was an efficient method for perchloroethylene removal with both oxygen an argon mixture and pure argon as input gas. Both input voltage and reaction time has positive effect on perchloroethylene removal; but initial perchloroethylene concentration has negative effect on perchloroethylene removal. Comparison of two plasma scenarios with different input gas shown that plasma generated by mixture of oxygen and argon gas was more powerful and had higher removal efficiency and degradation kinetics than the plasma generated by pure argon gas.

Seasonal Variations in Odorous Compounds Emission from A Municipal Solid Waste Disposal Plant

Waste treatment plants are among the major sources of odor nuisances and health risk to workers and nearby residents. In this work, we present an assessment of the seasonal variations in volatile compounds emission and the odor nuisance effects from a waste treatment plant. Air samples were seasonally collected in four different processing units in the plant, and analyzed by both instrumental and sensory methods. Results showed that a total of 17, 27, 23 and 14 volatile compounds were detected in the air samples collected in the four seasons, with average total chemical concentration of 1515.4, 5364.7, 3282.5 and 1067.6 µg m-3. On the other hand, the non-carcinogenic risk of H2S (1.7 and 1.3 in summer and autumn) and dichloromethane (1.7 in summer) exceeded the acceptable risk levels (HI = 1). Carcinogenic risk of ethylbenzene ranged from 2.1E-05 to 4.2E-05 in spring, autumn and winter, exceeding the acceptable carcinogenic risk level (1.0E-06). Moreover, the carcinogenic risk of tetrachloroethylene and ethylbenzene was larger than 1.0E-04 and reached the level of “definite risks” in summer.

Survival, metabolic rates and locomotory activities of a groundwater-obligate copepod species under long-term exposures to tetrachloroethylene

Volatile organic compounds (VOCs) are known to potentially cause a severe change in the respiratory metabolism of freshwater species, however the effect of these contaminants on groundwater-obligate species has not been investigated to date. Tetrachloroethylene (TCE) is a VOC frequently found in the groundwater bodies of industrialized areas, even years after a contamination event because TCE degradation takes several decades to occur. Contamination from TCE is considered persistent and difficult to remediate. Its high density favors a gravity-driven vertical infiltration into groundwater bodies. The TCE threshold value is 1.1 μg/L in groundwater bodies of Italy. TCE concentration in many Italian groundwater bodies is widely over this legal limit. In this study, we investigated the effect of 1.1 μg/L TCE on the survival, oxygen consumption, and locomotory activities of a groundwater-obligate copepod species. The specimens required for the trials were collected in the Antro del Corchia Cave (Tuscany). We measured the individual-based oxygen consumption of this species as a proxy of possible metabolic reactions to long-term (5 days) exposures to TCE at 8.0°C that is the mean annual temperature of groundwater flowing in the cave. To this end, we used a sealed glass microplate equipped with 24-planar oxygen sensor spots with optical isolation glued onto the bottom of 80-μL wells (Loligo Systems, Denmark) integrated with a 24-channel fluorescence-based respirometry system (SDR Sensor Dish Reader, PreSens, Germany). The system allows simultaneous measurement of 20 replicates and 4 controls. Survival and locomotory activity assessments were performed by counting the number of alive individuals and measuring the number of moving animals in 5 mL glass vials each containing 20 individuals. Preliminary results showed a decreasing in oxygen consumption of the organisms exposed to 1.1 μg/L TCE for 5 days at 8°C respect to the control. However, neither survival nor locomotory activities appeared to have been affected by exposure to TCE. See Suppl. material 1.

Anodic oxidation for the remediation of soils polluted with perchloroethylene

AbstractBACKGROUNDThis work focuses on the removal of perchloroethylene (PCE) from soils spiked with this hazardous chlorinated hydrocarbon and oil by a combination of two technologies: soil washing and anodic oxidation with diamond electrodes. The first attains the transfer of the pollutant from the soil to a soil washing fluid (SWF), from which the organics are then efficiently removed.RESULTSResults show that high concentrations of sodium dodecyl sulphate (SDS) are required in the SWF for an efficient extraction of the chlorinated hydrocarbon and electrolysis has to be applied not only to the clarified liquid, but also to the interphase. The surfactant used interacts strongly with soil not only during the washing, but also during the electrolysis step. This interaction seems to play a protective role against the oxidation of SDS. The initial phase of the electrolysis is rather complex and there are several processes which modify the results importantly.CONCLUSIONSRemoval of PCE by electrolysis from soil is less efficient than its removal from synthetic solutions of this chlorinated pollutant. There are two first‐order kinetic zones, which indicate an important competition for the oxidation of the different organics contained in the SWF during the electrolysis. © 2018 Society of Chemical Industry

Combined use of ISCR and biostimulation techniques in incomplete processes of reductive dehalogenation of chlorinated solvents

Pools of chloroethenes are more recalcitrant in the transition zone between aquifers and basal aquitards than those elsewhere in the aquifer. Although biodegradation of chloroethenes occur in this zone, it is a slow process and a remediation strategy is needed. The aim of this study was to demonstrate that combined strategy of biostimulation and in situ chemical reduction (ISCR) is more efficient than the two separated strategies. Four different microcosm experiments with sediment and groundwater of a selected field site where an aged perchloroethene (PCE)-pool exists at the bottom of a transition zone, were designed under i) natural conditions, ii) biostimulation with lactic acid, iii) in situ chemical reduction (ISCR) with zero valent iron (ZVI) and under iv) a combined strategy with lactic acid and ZVI. Biotic and abiotic dehalogenation, terminal electron acceptor processes and evolution of microbial communities were investigated for each experiment. The main results where: i) limited reductive dehalogenation of PCE occurs under sulfate-reducing conditions; ii) biostimulation with lactic acid promotes a more pronounced reductive dehalogenation of PCE in comparison under natural conditions, but resulted in an accumulation of cis-dichloroethene (cDCE); iii) ISCR with zero-valent iron (ZVI) facilitates a sustained dehalogenation of PCE and its metabolites to non-halogenated products, however, the iv) combined strategy results in the fastest and sustained dehalogenation of PCE to non-halogenated products in comparison of all four set-ups. These findings suggest that biostimulation and ISCR with ZVI are the most suitable strategy for a complete reductive dehalogenation of PCE-pools in the transition zone.

Preliminary Study: Environmental Assessment of Perchloroethylene in Dry-Cleaning Facilities in the UAE.

Background Perchloroethylene (PERC) is a widely spread cleaning solvent, used in nearly all dry-cleaning facilities. It has been declared as “probable human carcinogen” by the International Agency for Research on Cancer (IARC) due to its hazardous and toxic effects on human health. The study aimed at assessing the exposure of PERC among dry-cleaning workers at four different dry-cleaning facilities in the UAE. Methods The four dry-cleaning facilities, using PERC in one of the cities of the UAE, were selected. Draeger perchloroethylene 10/b detector tubes along with a Draeger accuro pump were used to estimate the levels of PERC exposure in three main selected positions in each of the facilities. Results The results showed that the second selected position had the highest amounts of PERC exposure above the international and local standards in 3 out of 4 selected facilities. The workers at position 2, who were not using any of the provided personal protective equipment, were at the highest risk of developing PERC-related health problems. Conclusion It is important to install local exhaust ventilation systems and monitoring devices of PERC concentrations in these facilities, along with raising the awareness of workers about the health effects of PERC and the importance of using personal protective equipment (PPE) while performing their job.