Perchloroethylene Concentrations Research Articles

Groundwater Plume Characteristics at Small Chlorinated-Solvent Release Sites in California

There is a need to study the spatiotemporal distribution of chlorinated solvent releases in groundwater to understand the risk/threat they pose to human health, water quality, and the environment, which then can be used to prioritize clean-up and evaluate regulatory closure with appropriate risk management controls. This paper provides a statistical analysis of spatiotemporal distribution of perchloroethylene (PCE) (and its degradation products including trichloroethene [TCE]) from eighty-three cases across California for which data were available onthe State Water Resources Control Board’s GeoTracker database and the Department of Toxic Substance Control Board’s Envirostor database. These cases consisted of seventy-one dry cleaning sites and twelve other similar small solvent release sites. Statistical analyses of available groundwater data were performed to estimate: maximum concentrations at the source area, groundwater plume length, plume stability; and correlations between plume length, concentrations, and plume age. At 90% of the sites, the PCE and TCE plume lengths were less than 1,569 feet (478 meters) and 1,782 feet (543 meters), respectively. The average plume lengths for PCE and TCE were 670 feet (204 meters) and 701 feet (213 meters), respectively. At 90% of the sites that have reached stable conditions, PCE and TCE concentrations at the source areas were less than 2,670 and 660 micrograms per liter (µg/L) respectively. This study for the first time provides key characteristics of small chlorinated-solvent plume behaviors in California that can be used to prioritize management of small chlorinated-solvent release sites and to develop strategies towards achieving closure at these sites.

Remediation of perchloroethylene contaminated groundwater using Fe0/ZnS embedded in a highly porous polymer: Experimental results on pilot-scale photoreactor and kinetic modeling analysis for industrial scale-up

Perchloroethylene (PCE) is a pollutant toxic to aquatic life and suspected of being a human carcinogen. It is also recalcitrant to degradation. Therefore remediation of PCE-contaminated groundwater is currently still a challenging task. In this work, the efficiency of a UV-assisted oxidation process exploiting a photocatalyst composed of zero-valent iron supported on commercial zinc sulfide (Fe/ZnS) and incorporated in a highly porous polymer, is investigated. The experimental studies were carried out, for about six months, on a pilot-scale photoreactor operating in continuous mode at the Solofra (Campania, Italy) wastewater plant, to evaluate the effectiveness and stability of the photocatalytic system. The results show that it is possible to reach a PCE degradation in natural groundwater in the range of 85–95%%. Furthermore, a kinetic model is developed and compared with collected experimental data. The mathematical model well describes the experimental data of the photocatalytic system operating both in batch and continuous mode and therefore it can be potentially used for further scale-up of photocatalytic systems devoted to PCE degradation, allowing to estimate the catalyst weight required for total PCE removal as a function of the liquid flow rate to be treated and inlet PCE concentration.

The importance of proper pH adjustment and control to achieve complete in situ enhanced reductive dechlorination.

In situ bioremediation of chlorinated compounds such as perchloroethylene (PCE) and trichloroethylene (TCE) through enhanced reductive dechlorination (ERD) requires appropriate growth conditions for organohalide-respiring bacteria (OHRB). One of the most important factors controlling OHRB metabolism is groundwater pH. Dehalococcoides spp. (DHC) growth may be inhibited when pH is lower than 6.0, which can lead to the accumulation of toxic daughter compounds including cis-dichloroethylene (cDCE) and vinyl chloride (VC). Aquifer pH may decline as HCl is released during reductive dechlorination and from substrate fermentation to fatty acids and carbonic acid. In this article, we demonstrate that using proper pH adjustment and control in situ is an appropriate strategy to achieve complete ERD (i.e., complete conversion of PCE and TCE to nontoxic ethylene) in remediation sites with inherently low pH values and/or low buffering capacity. To analyze the effectiveness of this approach, field monitoring results are presented for a challenging site containing high concentrations of PCE and TCE (>10 000 µg/L and >1000 µg/L, respectively) and low aquifer pH (~4.9). Addition of a bioaugmentation culture, emulsified vegetable oil (EVO), and a colloidal buffer (CoBupHTM ) to increase pH, stimulated rapid conversion of PCE and TCE to cDCE and VC. However, further conversion of cDCE and VC was very limited. To stimulate complete conversion to ethylene, additional CoBupHTM and nutrients were injected, resulting in a rapid increase in metabolic rates, and maintained the aquifer pH at ~6.5 for more than five years, thus demonstrating that complete ERD can be achieved in sites with similar characteristics. Proper pH adjustment and control is needed to limit the accumulation of toxic intermediates, maintaining in situ bioremediation as an efficient, affordable, and environmentally friendly option to treat chlorinated compounds. Integr Environ Assess Manag 2023;19:943-948. © 2022 SETAC.

Degradation of High-Concentration of Perchloroethylene from Aqueous Solution Using Electro-Fenton Process

Introduction: Perchloroethylene (PCE) is one of the most well-known chlorinated organic compounds recently detected in aqueous environments. The presence of PCE in aquatic ecosystems has caused many health problems and environmental challenges. Therefore, its removal and treatment from aqueous environments are essential.
 Materials and Methods: The electro-Fenton (EF) process was carried out in a cylindrical reactor containing 250 mL contaminated water with PCE. The effects of parameters, including solution pH (3-12), current density (2-10 mA cm-2), H2O2 concentration (20-70 µL H2O2 per 250 mL sample.), PCE concentration (5-50 mg L-1), and electrolysis time (1-15 min) on PCE degradation were investigated. The kinetics and radical’s scavenger of the EF process were examined to detect the exact mechanism of PCE degradation.
 Results: The degradation of the PCE of 98.1% was obtained in the optimum condition, including solution pH of 5, the current density of 8 mA cm-2, H2O2 concentration of 50 µL per 250 mL sample, PCE concentration of 15 mg L-1, and electrolysis time of 10 min. The kinetics studies of the EF process indicated that the obtained results were in satisfactory agreement with the first-order model (R2 = 0.9858, Kapp = 0.2822). Also, the addition of ethanol and tertiary butanol caused an inhibiting effect.
 Conclusion: The EF process was effectively applied to degrade PCE from polluted water as an efficient technique. The obtained results indicated that the generation of •OH throughout the EF process was the key mechanism that controlled the EF process.

The perchloroethylene-induced toxicity in dry cleaning workers lymphocytes through induction of oxidative stress.

Evaluation of the compounds and metabolites, and studying their side effects in the workplace is essential. This study was designed to evaluate the exposure of dry cleaning workers to perchloroethylene (PEC), and its liver and kidney damage, and oxidative stress in B-lymphocytes isolated from the workers. Blood samples were evaluated for liver (alanine transaminase [ALT] and aspartate transaminase [AST]) and kidney (BUN and creatinine) markers. For measurement of PEC, exhaled, personal, and ambient air samples were collected and analyzed gas chromatography (GC-FID) through the NIOSH 1003 and 3704 methods. Also, the parameters of oxidative stress including the level of reactive oxygen species (ROS), glutathione (GSH), oxidized glutathione (GSSG), and lipid peroxidation (LPO) in B-lymphocytes were evaluated. The results showed that the levels of liver enzymes ALT and AST in dry cleaning workers are higher than in the control group. The personal exposure levels and exhaled air concentration of PEC in dry cleaning workers were above the recommended national occupational exposure limits (OELs) and the biological exposure index (BEI). The levels of ROS, LPO, and GSSG in B-lymphocytes from the dry cleaning workers are higher than the control group, and the levels of GSH in dry cleaning workers are lower. The results suggested that exposure of dry cleaning workers to PEC could be associated with liver damage and oxidative damage in B-lymphocytes.

Combined method of 3H/3He apparent age and on-site helium analysis to identify groundwater flow processes and transport of perchloroethylene (PCE) in an urban area

Urban groundwater management requires a thorough and robust scientific understanding of flow and transport processes. 3H/3He apparent ages have been shown to efficiently help provide important groundwater-related information. However, this type of analysis is expensive as well as labor- and time-intensive, and hence limits the number of potential sampling locations.To overcome this limitation, we established an inter-relationship between 3H/3He apparent groundwater ages and 4He concentrations analyzed in the field with a newly developed portable gas equilibrium membrane inlet mass spectrometer (GE-MIMS) system, and demonstrated that the results of the simpler GE-MIMS system are an accurate and reliable alternative to sophisticated laboratory based analyses. The combined use of 3H/3He lab-based ages and predicted ages from the 3H/3He–4He age relationship opens new opportunities for site characterization, and reveals insights into the conceptual understanding of groundwater systems.For our study site, we combined groundwater ages with hydrochemical data, water isotopes (18O and 2H), and perchloroethylene (PCE) concentrations (1) to identify spatial inter-aquifer mixing between artificially infiltrated groundwater and water originating from regional flow paths and (2) to explain the spatial differences in PCE contamination within the observed groundwater system. Overall, low PCE concentrations and young ages occur when the fraction of artificially infiltrated water is high. The results obtained from the age distribution analysis are strongly supported by the information gained from the isotopic and hydrochemical data. Moreover, for some wells, fault-induced aquifer connectivity is identified as a preferential flow path for the transport of older groundwater, leading to elevated PCE concentrations.

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.

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.

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.

Nonalcoholic Fatty Liver Disease Is a Susceptibility Factor for Perchloroethylene-Induced Liver Effects in Mice.

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent pathological liver condition in developed countries. NAFLD results in severe alterations in liver function, including xenobiotic metabolism. Perchloroethylene (PERC) is a ubiquitous environmental pollutant, a known hepatotoxicant in rodents, and a probable human carcinogen. It is known that PERC disposition and metabolism are affected by NAFLD in mice; here, we examined how NAFLD changes PERC-associated liver effects. Male C57Bl6/J mice were fed a low-fat diet (LFD), high-fat diet (HFD), or methionine/folate/choline-deficient diet (MCD) to model a healthy liver, or mild and severe forms of NAFLD, respectively. After 8 weeks on diets, mice were orally administered PERC (300 mg/kg/day) or vehicle (5% aqueous Alkamuls-EL620) for 5 days. PERC-induced liver effects were exacerbated in both NAFLD groups. PERC exposure was associated with up-regulation of genes involved in xenobiotic, lipid, and glutathione metabolism, and down-regulation of the complement and coagulation cascades, regardless of the diet. Interestingly, HFD-fed mice, not MCD-fed mice, were generally more sensitive to PERC-induced liver effects. This was indicated by histopathology and transcriptional responses, where induction of genes associated with cell cycle and inflammation were prominent. Liver effects positively correlated with diet-specific differences in liver concentrations of PERC. We conclude that NAFLD alters the toxicodynamics of PERC and that NAFLD is a susceptibility factor that should be considered in future risk management decisions for PERC and other chlorinated solvents.

Nonalcoholic Fatty Liver Disease Is a Susceptibility Factor for Perchloroethylene-Induced Liver Effects in Mice.

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent pathological liver condition in developed countries. NAFLD results in severe alterations in liver function, including xenobiotic metabolism. Perchloroethylene (PERC) is a ubiquitous environmental pollutant, a known hepatotoxicant in rodents, and a probable human carcinogen. It is known that PERC disposition and metabolism are affected by NAFLD in mice; here, we examined how NAFLD changes PERC-associated liver effects. Male C57Bl6/J mice were fed a low-fat diet (LFD), high-fat diet (HFD), or methionine/folate/choline-deficient diet (MCD) to model a healthy liver, or mild and severe forms of NAFLD, respectively. After 8 weeks on diets, mice were orally administered PERC (300 mg/kg/day) or vehicle (5% aqueous Alkamuls-EL620) for 5days. PERC-induced liver effects were exacerbated in both NAFLD groups. PERC exposure was associated with up-regulation of genes involved in xenobiotic, lipid, and glutathione metabolism, and down-regulation of the complement and coagulation cascades, regardless of the diet. Interestingly, HFD-fed mice, not MCD-fed mice, were generally more sensitive to PERC-induced liver effects. This was indicated by histopathology and transcriptional responses, where induction of genes associated with cell cycle and inflammation were prominent. Liver effects positively correlated with diet-specific differences in liver concentrations of PERC. We conclude that NAFLD alters the toxicodynamics of PERC and that NAFLD is a susceptibility factor that should be considered in future risk management decisions for PERC and other chlorinated solvents.

Effect of Coupling Zero-Valent Iron Side Filters on the Performance of Bioreactors Fed with a High Concentration of Perchloroethylene

AbstractThe objectives of this work were first to evaluate the effect of coupling a zero-valent side filter to anaerobic fluidized bed bioreactors (HFBB) versus bioreactors without the zero-valent filter, also called methanogenic fluidized bed bioreactors (MFBB); and second to study the diversity of the microbial community in both types of bioreactors. At the end of operation (in the last 75 d), the HFBB reached a 95% removal of the incoming tetrachloroethylene, whereas the MFBBs without filter achieved a removal of 88%. Genera such as Dehalobacter spp., Desulfurospirillum spp., Desulfitobacterium spp., and Dehalococcoides spp., and Methanosarcina were found at the end of the treatment. Coupling zero-valent filters to bioreactors (HFBB) fed with high tetrachloroethylene concentration improved reactor performance [high tetrachloroethylene removal and reduction of concentrations of vinyl chloride (VC) and dichlorethylene (DCE)]. This performance was consistent with significant higher concentrations of dehal...

캠프 캐럴 인근 주민의 혈중 및 요중 휘발성 유기화합물 평가

Objectives: Exposure to volatile organic compounds such as trichloroethylene(TCE) and perchloroethylene(PCE), along with Agent Orange, that were issued around Camp Carroll US Army Base situated in Waegwan, Chilgok-gun, Gyeongsangbuk-do Province, Korea. The main objective of this study was to assess the exposure to TCE and PCE of residents of the area surrounding Camp Carroll. Methods: The TCE, PCE and trichloroethanol(TCEOH) concentrations in blood and trichlroroacetic acid(TCA) and TCEOH concentrations in urine were measured and analyzed in a total of 1,033 residents around Camp Carroll. TCA and TCEOH are metabolites of TCE and PCE, respectively. The information on demographic characteristics and exposure variables in relation to underground water were obtained through a questionnaire completed by the subjects. Results: TCE, PCE and TCEOH concentrations were not detected in blood. Detection rates of TCA and TECOH concentrations in urine were 98.5% and 36.6%, respectively. Creatinine-corrected average TCA and TCEOH concentrations were 12.23±23.81 μg/g and 0.66±4.31 μg/g, respectively. A significant difference was not shown between the drinking group and no drinking group for underground water, which was assumed as a potential route of exposure to TCE and PCE through the consumption of ground water. However, females drinking ground water showed a significantly higher mean level of TCA in urine than did males. There was no significant difference according to drinking ground water as a potential source of exposure to TCE and PCE in residents around Camp Carroll. Conclusions: Considering the statistical analysis of factors affecting exposure to TCE and PCE in ground water along with previous reports, TCA in urine as exposure to TCE and PCE might not be appropriate because it is found in chlorinated drinking water. Therefore, TCA concentration in urine may be the result of drinking of chlorinated water.

Occurrence of perchloroethylene in surface water and fish in a river ecosystem affected by groundwater contamination.

Long-term monitoring of the content of perchloroethylene (PCE) in a river ecosystem affected by groundwater contamination was performed at a site in the Czech Republic. The quality of surface water was monitored quarterly between 1994 and 2013, and fish were collected from the affected ecosystem to analyse the content of PCE in their tissue in 1998, 2011 and 2012. Concentrations of PCE (9-140 μg/kg) in the tissue of fish collected from the contaminated part of the river were elevated compared to the part of the river unaffected by the contamination (ND to 5 μg/kg PCE). The quality of surface water has improved as a result of groundwater remediation during the evaluated period. Before the remedial action, PCE concentrations ranged from 30 to 95 μg/L (1994-1997). Following commencement of remedial activities in September 1997, a decrease in the content of PCE in the surface water to 7.3 μg/L (1998) and further to 1 μg/L (2011) and 1.1 μg/L (2012) led to a progressive decrease in the average concentration of PCE in the fish muscle tissue from 79 μg/kg (1998) to 24 (2011) and 30 μg/kg (2012), respectively. It was determined that the bioconcentration of PCE does not have a linear dependence because the decrease in contamination in the fish muscle tissue is not directly proportional to the decrease in contamination in the river water. The observed average bioconcentration factors were 24 and 28 for the lower concentrations of PCE and 11 for the higher concentrations of PCE in the river. In terms of age, length and weight of the collected fish, weight had the greatest significance for bioconcentration, followed by the length, with age being evaluated as a less significant factor.

Single-walled carbon nanotube/silica composite as a novel coating for solid-phase microextraction fiber based on sol-gel technology

Single-walled carbon nanotubes (SWCNTs)/silica composite coating for solid phase microextraction synthesized by sol-gel technology was developed for air sampling and determination of perchloroethylene, benzotrichloride, chloromethyl methyl ether and trichloroethylene. Application of this method was investigated under different laboratory conditions. Predetermined concentrations of each analyte were prepared in a homemade standard chamber and the influence of temperature, humidity, extraction time, storage time, desorption temperature and desorption time was investigated. Under optimal conditions, the use of SWCNTs/silica composite fiber showed high sensitivity and fast sampling of halogenated volatile organic compounds from air. For linearity test, the regression correlation coefficient was more than 98% for analytes of interest and linear dynamic range for the proposed fiber and the applied gas chromatography-flame ionization detector (GC-FID) technique was from 1 to 100 ng/mL Method detection limits ranged from 0.11 to 0.2 ng/mL and method quantification limits were between 0.34 and 0.7 ng/mL. SWCNTs/silica composite fiber was highly reproducible; relative standard deviations were between 5.6 and 11.7%. The developed method was applied to determine perchloroethylene concentration of real air samples of a dry cleaning shop and the results compared with the data obtained with commercially available carboxen/polydimethylsiloxane (CAR/PDMS).

Photocatalytic oxidation of gaseous perchloroethylene over TiO 2 based paint

Abstract Perchloroethylene (PCE) is a volatile chlorinated compound persistently present in indoor air of several industrial closed facilities. Due to its environmental and human health impact, efforts have been directed in the last decades toward the degradation of this kind of air pollutants. The photocatalytic oxidation (PCO) of PCE was studied in an annular photoreactor equipped with a compound parabolic collector (CPC) and employing two different configurations of a monolithic structure of cellulose acetate coated with an active TiO 2 -based paint (9 wt.% of TiO 2 PC500) under solar radiation. The influence of the experimental conditions, namely feed flow rate ( Q feed ), initial concentration ( C PCE,feed ), relative humidity (RH) in the system, absence of oxygen and incident irradiance on the PCE conversion was evaluated. Under the best experimental conditions ( C PCE,feed = 1100 ppm, Q feed = 75 cm 3 min −1 , RH = 40% and I = 38.4 W UV m −2 in the presence of oxygen) 60% of the initial PCE concentration was converted. The results showed that depending on the configuration of the structure, photocatalytic degradation of PCE can be enhanced by approximately 58%. Results obtained at low RH suggest that Cl radical chain propagation reactions may be included in the PCO mechanism of PCE. Also, in the absence of oxygen the photoreaction can still take place.

Degradation of perchloroethylene by ferrate(VI)

The degradation characteristics of perchloroethylene by ferrate(VI) oxidation have been studied. The degradation efficiency of perchloroethylene in aqueous solution was investigated at various values of ferrate(VI) dosage, pH, initial concentration of perchloroethylene and aqueous solution temperature. GC-ECD has been used to analyze the changes of perchloroethylene concentration. The optimum conditions of perchloroethylene degradation were obtained at pH 7.0 and 25˚C of aqueous solution temperature. Also, the experimental results showed that perchloroethylene removal efficiency increased with the decrease of initial concentration of perchloroethylene. Lastly intermediate products were identified by GC-MS techniques. Trichloroethylene and chloroform were identified as reaction intermediates.

Adsorption performance and mechanism of perchloroethylene on a novel nano composite β-FeOOH-AC

Akaganeite-activated carbon (β-FeOOH-AC) nano composite was prepared firstly and characterized. β-FeOOH-AC was used in the removing perchloroethylene (PCE) from water. The adsorption performance and mechanism of PCE from water by β-FeOOH-AC is investigated through batch experiments including kinetics, thermodynamics and isothermal adsorption models. The results show that the PCE removal achieves 97.83% when the initial PCE concentration is 100 mg/L and sorbent dosage is 8 g/L at temperature 298 K. The kinetic data prove a closer fit to the pseudo-second order model. The isotherm data can be fit with Langmuir and Freundlich isothermal adsorption models. Additionally, the thermodynamic analysis indicates PCE adsorption on β-FeOOH-AC is a spontaneous, endothermic, single and multi-layer combined physical adsorption process, and β-FeOOH-AC has a strong PCE adsorption affinity. The excellent adsorption performance and low cost of the β-FeOOH-AC can be considered as one of the effective options to remove PCE from contaminated water.

Nanoscale zero-valent iron flakes for groundwater treatment

Even today the remediation of organic contaminant source zones poses significant technical and economic challenges. Nanoscale zero-valent iron (NZVI) injections have proved to be a promising approach especially for source zone treatment. We present the development and the characterization of a new kind of NZVI with several advantages on the basis of laboratory experiments, model simulations and a field test. The developed NZVI particles are manufactured by milling, consist of 85 % Fe(0) and exhibit a flake-like shape with a thickness of <100 nm. The mass normalized perchloroethylene (PCE) dechlorination rate constant was 4.1 × 10−3 L/g h compared to 4.0 × 10−4 L/g h for a commercially available reference product. A transport distance of at least 190 cm in quartz sand with a grain size of 0.2–0.8 mm and Fe(0) concentrations between 6 and 160 g/kg (sand) were achieved without significant indications of clogging. The particles showed only a low acute toxicity and had no longterm inhibitory effects on dechlorinating microorganisms. During a field test 280 kg of the iron flakes was injected to a depth of 10–12 m into quaternary sand layers with hydraulic conductivities ranging between 10−4 and 10−5 m/s. Fe(0) concentrations of 1 g/kg (sand) or more [up to 100 g/kg (sand)] were achieved in 80 % of the targeted area. The iron flakes have so far remained reactive for more than 1 year and caused a PCE concentration decrease from 20.000–30.000 to 100–200 µg/L. Integration of particle transport processes into the OpenGeoSys model code proved suitable for site-specific 3D prediction and optimization of iron flake injections.

Biomonitoring Study of Dry Cleaning Workers Using Cytogenetic Tests and the Comet Assay

Perchloroethylene (PCE) is the main solvent used in the dry cleaning industry worldwide. The aim of the present work was to evaluate the genotoxic potential of occupational exposure to PCE in dry cleaning workers. The study was carried out in 59 volunteers (30 workers, 29 controls). The genotoxic effect was evaluated by analyzing chromosome aberrations (CAs), and micronuclei (MN) and DNA damage (assessed by the comet assay) in peripheral blood lymphocytes. Environmental monitoring of exposure was carried out on personal breathing zone air samples collected during two consecutive working days by measuring the concentration of PCE air levels. The mean PCE concentration in workplace air of dry cleaning workers was 31.40 mg/m3. There were no significant differences in CA frequency between dry cleaning workers and the controls, but analysis showed a significant association of CA frequency with employment duration and frequency of exposure to PCE. The MN frequency and DNA damage detected by alkaline comet assay were significantly increased in dry cleaning workers compared to the controls. The results suggest that (a) chronic occupational exposure to dry cleaning solvents below permissible occupational exposure limit of 70 mg/m3 (i.e., ∼10.3 ppm) may lead to an increased risk of genetic damage among dry cleaning workers, and (b) CA, MN tests, and comet assay are useful to monitor populations exposed to low doses of PCE.