Hexachlorobutadiene (HCBD), a by-product in the synthesis of perchloroethylene and trichloroethylene and a prominent environmental pollutant, is one of the most nephrotoxic chlorinated-hydrocarbons in rodents. Its organ-specific toxicity is based on a bioactivation mechanism that includes hepatic conjugation with glutathione to produce (penta-chloro, butadienyl)-glutathione (PCBG) and finally to (pentachloro butadienyl)-cysteine (PCBC), translocation and subsequent enzymatic degradation to toxic metabolites by the enzyme C-S-lyase/GTK/KAT. In this study we attempted to determine whether HCBD is a site-specific neurotoxin in the young rat. In this research, 28-day old male Wistar albino (W/A) rats were used. Groups of rats received daily doses of HCBD 25mg /kg, ip (low dose), for 2, 3, 4 and 7 days and 100mg/kgbody weight, ip (high dose), for one and two days. Control group received corn oil, 1ml /kg, ip. Animals were killed, the brain removed, halved, one half fixed in formalin and embedded in paraffin for histopathology and the other half was frozen in dried-ice isopantane for enzyme assay. Sections of 5 µm were prepared and stained with hematoxylin and eosin. Light microscopic examination showed an extensive damage in the choroids plexus of lateral and third ventricles in HCBD treated rats, especially in 1-day HCBD (100mg/kg) treated group, compare with control and other groups. In groups treated with low dose of HCBD there is a minor haemorrhage in lateral ventricles with pyknotic and mitotic figures in coroidal cells. Glutamine transaminase K (GTK) specific activity in high dose treated groups was lower than control group. In low dose treated groups GTK specific activity showed higher, but not significantly, than that of control group. In high dose treated groups the activity of GTK was lower than control. Data have shown that HCBD is a neurotoxin and choroid plexus in the lateral and third ventricles is the most sensitive organ that is affected.        

Background and Objective: “Perchloroethylene” is a solvent widely used in dry cleaning industry. Various effects on liver, kidney, nervous and cardiovascular systems have been attributed to exposure to this solvent. In this study we assessed some of the neuropsychological effects of chronic exposure to perchloroethylene on exposed dry cleaning workers.Materials and Methods: 40 exposed and 40 non exposed workers were compared in this historical cohort study. The researchers collected the data using a questionnaire and a check list. Frequency of selected neuropsychological effects were evaluated and compared in each group by means of statistical software. Results: After adjustment for age and educational status, the frequency of depression in exposed group and non-exposed group was calculated to be %42/5 and %22/5 respectively (P=0/056). Frequency of memory loss was higher in exposed group (%27/5) compared to non-exposed group (%17/5) (P>0.05) and the frequency of repetitive checking was surprisingly higher in non-exposed group and this difference was statistically significant (P<0/05).Conclusion: The observed difference in .frequency of depression in exposed and non exposed workers in our study was consistent with findings of previous studies. We were not able to demonstrate any statistically significant relation between perchloroethylene exposure and other neuropsychological effects. Our findings of repetitive checking was unexpectedly in contrast to the findings of previous studies.

Background: Perchloroethylene (PCE) is a chlorinated aliphatic hydrocarbon which has been widely used in some industries. Industrial wastewaters polluted with PCE must be treated because of its possible carcinogenic effects. Since an Anaerobic Migrating Blanket Reactor (AMBR) has never been used in PCE biodegradation, this study aimed to determine its ability to biodegrade PCE with higher concentrations than those previously studied.Methods: A laboratory scale AMBR, with a total volume of 10 liters and four compartments for biodegradation of PCE in synthetic substrate, was used. The reactor was seeded with anaerobic digested sewage sludge. Then, the performance of the reactor was evaluated during 4 phases through which PCE loading rate increased from 3.75 to 75 mg/L.d. Hydraulic retention time (HRT) was fixed at 32 hours.Findings: Optimum 98% COD removal efficiency through organic loading of COD was obtained as 3.1g/L.d. Optimum 99.8% PCE removal efficiency was observed at a loading rate equal to 37.5 mg/L.d.Average COD and PCE removal efficiency for the whole active period of the reactor were 91.4 and 99.5%, respectively.Conclusion: According to our results, a full-scale AMBR can be used as a simple, efficient, and reliable method for treatment of PCE in real polluted industrial wastewater.

Background and objective: Perchloroethylene is a chlorinated hydrocarbon used as a solvent in many industries and services activities such as dry cleaning and auto industry as degreasing. We carried out a bioassay using Daphnia Magna in order to determine the ecological effects of wastewater treatment through applying advanced oxidation processes (ultrasonic, ultraviolet irradiation and hydrogen peroxide processes) for removal of perchloroethylene.Materials and Methods: Due to the sensitivity of Daphnia and reports indicating this species is the most sensitive aquatic invertebrate to a variety of organic compounds, toxicity of perchloroethylene and its intermediate degradation products during applying different processes was tested using Daphnia. Lethal concentration (LC50) and toxic units (TU) were determined. In to determine toxicity of perchloroethylene, its stock solution was prepared at a concentration of 100 mg/L. Then, nine samples each containing 0 (control), 5, 10, 20, 30, 40, 50, 75, and 100% by volume of the primary stock solution were prepared. To determine the toxicity of the intermediate products of perchloroethylene by ultrasonic, photolysis, photolysis with hydrogen peroxide and photosonic processes, an initial concentration of perchloroethylene for each reactor (100 mg/L) was taken. All experiments were carried out at the Laboratory of Microbiology, Faculty of Health, Tehran University of Medical Sciences, Iran.Results: It was found that the 24 h LC50 for perchloroethylene on Daphnia Magna was 35.51 mg /L. The 48 h, 72 h and 96 h LC50 of perchloroethylene were 28.058, 21.033, and 19.27 mg/L respectively. Toxicity of perchloroethylene was decreased after oxidation processes.Conclusion: The toxicity after hybrid processes was lower than the single processes. The toxicity reduction was the same during all time period. Hence, the hypothesis of reducing toxicity of the intermediate products of perchloroethylene degradation after the abovementioned processes is acceptable. It is noteworthy that although there are different intermediate compounds in the effluent of various chemical oxidation processes,, but they are less toxic compared with the original perchloroethylene; this may be due to the partially concentration of intermediate products that will decrease toxicity.

Electrokinetic (EK) technology is advanced methods for the degradation and ex- traction of heavy metals and organic contaminants from saturated and unsaturated soil and groundwater. In this method, with the application of an electric field, pol- lutants will be migrated towards anode or cathode by electrolysis, electro-osmosis, electromigration, and electrophoresis. In this study, the behavior of perchloroethy- lene contaminated soils in an electrokinetic (EK) system enhanced by Triton X-100 on laboratory scale for 10 days was investigated. Electrical current and cumulative electro-osmosis and pH in anode and cathode reservoirs were measured every 24 hours during the run and perchloroethylene content was measured at the end of the experiments. According to the results, perchloroethylene is not influenced by electro-osmosis and ion migration due to low solubility, non-polar, and high ad- sorption to soil. However, by using the TX-100’ in EK process, pollutant removal efficiency is significantly increased and perchloroethylene content of the soil is decreased by 51 %.

Background and objectives: Perchloroethylene (PCE) is categorized as contaminant of concern because of its adverse health effects and persistence in drinking water resources. Permeable reactive barrier with zero valent iron (ZVI-PRB) is a passive zone in which chlorinated ethenes are degraded in situ through the chemical reduction mechanism. The objective of the present investigation was optimization and modelling of ZVI-PRB technology for the elimination of PCE from the aqueous environment using response surface methodology.Materials and methods: In order to simulate ZVI-PRB, a column filled with silica sand and ZVI was used. effects of three variables including pH, column height or barrier thickness and flow on reductive de chlorination efficiency were assessed. Design of experiment, modelling, and data analysis were carried out using response surface method.Results: The de chlorination efficiency was about 93% under optimum conditions (pH=5, 26 cm column height and 2 mL/min flow rate). The ascending trend of pH along the column revealed that the reductive condition was dominant within the column. The R2 value of 0.98 also indicated good fitness of the experimental results and model predictions.Conclusion: Based on the results, ZVI-PRB technology has high efficiency in de chlorination of PCE. Likewise, regarding to no need of energy consumption, abundance of iron, no production of harmful by-products and cost-effectiveness, ZVI-PRB is propounded as a stable, green, and environmental friendly technology in groundwater remediation.

Quantitative description of soil hydraulic properties is crucial for preventing organic contamination entering into the soil and groundwater. In order to assess the hydraulic behaviour of Perchloroethylene as a toxic chlorinated contaminant in soil, the retention curves for Perchloroethylene and water were determined. The Saturated hydraulic conductivity of both fluids examined was determined by the constant head method. The Perchloroethylene and water hydraulic conductivities obtained were 492.84 and 450.27 cm day-1, respectively. The porous medium retention parameters were obtained based on the van Genuchten, Brooks-Corey and Kosugi retention models. Further, the unsaturated hydraulic conductivity for both fluids was obtained based on the Mualem- Brooks- Corey, Mualem-van Genuchten and Mualem- Kosugi models. The accuracy performance of the models was assessed using some statistics including ME, RMSE, EF, CD and CRM. Results indicated that the van Genuchten model provided better estimations than other models when the fluid studied was Perchloroethylene. The results further indicated that the magnitudes of the pore-size distribution parameters and the bubbling pressure parameters are reduced more in a water-air system compared to a Perchloroethylene-air system. This can be attributed to the high viscosity of water and its considerable resistance against flow. This implies that more suction is needed to drain water out from a porous medium than Perchloroethylene. Consequently, a porous medium provides less retention for Perchloroethylene at a given quantity of fluid than water. Owing to lower Perchloroethylene viscosity, the saturated and unsaturated porous medium hydraulic conductivity of Perchloroethylene was greater than that of water. Since Perchloroethylene has lower retention and larger hydraulic conductivity than water, its infiltration into a porous medium would lead to its faster movement towards groundwater.

Background and aims: Needle trap micro-sampler, with all advantages of microextraction techniques such as solid phase microextraction, owing to the ease of use and becoming a powerful method for air pollution monitoring. In this study, the performance of needle trap micro-sampler device with silica composite of carbon nanotubes, prepared using sol-gel technique, was investigated for health monitoring of perchloroethylene in air.Methods: After preparation of proposed sorbent, 1.5 cm length of a 21-gauge needle (10 cm length and 0.52 mm I.D.) packed and the experimental parameters adjusted and the performance of micro-extraction sampler assessed in the sampling, storage and desorption stages for micro-sampling and determination of perchloroethylene. Finally the sampler was used for air monitoring of perchloroethylene in the dry cleaning and compared with NIOSH relevant method.Results: The results demonstrated that breakthrough volumes were more than 1300 and 1100 ml for needle trap packed with CNTs/silica composite and CAR/PDMS, respectively. Increasing the sampling temperature and relative humidity reduced the sampling efficiency and the needle trap devices with both sorbents showed less than 4% for analyte losses after seven days. In the field sampling, needle trap with nano-structured sorbent showed better response comparing to the NIOSH 1003 method.Conclusion: Needle trap device packed with silica composite of carbon nanotubes showed good performance for sampling of perchloroethylene in air and recommended for health monitoring of occupational and environmental pollutant.

Background and Objectives: The retention and hydraulic conductivity are important characteristics of porous media in relation to imposed contaminants. Retention curve and hydraulic conductivity are dependent on soil and fluid characteristics. When entering groundwater, Chlorinated contaminants cause contamination due to the type of compounds. Thus preventing these materials to enter soil and water is crucial to avoid any contamination. In order to investigate the hydraulic behavior of Trichloroethylene in soil, the retention of Trichloroethylene and water were determined. Determining the saturated hydraulic conductivity and estimating the unsaturated hydraulic conductivity by Mualem-van Genuchten, Mualem-Brooks-Corey and Mualem-Kosugimodels in the two-phase NAPL-air systems were other objectives of this study. Materials and Methods: In this study, the hydraulic behavior of both Trichloroethylene fluid and water were examined. In order to draw the water and Trichloroethylene retention curves in silty loam soil texture, the hanging water column method was used. The constant head method was employed to determine the saturated hydraulic conductivity. The soil retention parameters for Trichloroethylene and water were obtained based on van Genuchten, Brooks-Corey and Kosugi retention models, using the RETC program. The unsaturated hydraulic conductivity, for both fluids as a function of Matric potential was obtained based on Mualem-Brooks-Corey, Mualem-van Genuchten and Mualem-Kosugi models. The performances of these models were assessed by some statistics including ME, RMSE, EF, CD and CRM. Results: The obtained results indicated that in a certain amount of liquid phase, Trichloroethylene has lower retention and larger hydraulic conductivity compared to water in soil. According to lower surface tension and viscosity of Trichloroethylene compared to water, the saturated hydraulic conductivity of Trichloroethylene and water were 136. 75 and 94. 50 cm/day, respectively. For water, the van Genuchten retention model demonstrated highest EF (0. 93) and lowest RMSE (0. 018) values compared to Trichloroethylene fluid. The other two models were also provided better efficiency for water than Trichloroethylene. In case of Trichloroethylene, the van Genuchten and Brooks-Corey models showed highest efficiency. Generally, the accuracy of all three models for Trichloroethylene was less than water. Conclusions: The validation results of hydraulic models shows that the van Genuchtenmodel provides better prediction for retention in soil compared to Kosugi and Brooks-Corey models in the two-phase air-water and air-Trichloroethylene systems. Finally, due to the higher hydraulic conductivity and less maintenance of Trichlorothene fluid than water, if entering the soil, it will move faster towards groundwater and, if introduced into the aquifer, will cause contamination and change in water quality.