[Determination of six halogenated solvent residues in olive oil by headspace gas chromatography]

The residual amount of halogenated solvents in olive oil is an important indicator of its quality. The National Olive Oil Quality Standard GB/T 23347-2021 states that the residual amount of individual halogenated solvents in olive oil should be ≤0.1 mg/kg and that the total residual amount of halogenated solvents should be ≤0.2 mg/kg. COI/T.20/Doc. No. 8-1990, which was published by the International Olive Council, describes the standard method used for the determination of halogenated solvents in olive oil. Unfortunately, this method is cumbersome, has poor repeatability and low automation, and is unsuitable for the detection and analysis of residual halogenated solvents in large quantities of olive oil. At present, no national standard method for determining residual halogenated solvents in olive oil is available in China. Thus, developing simple, efficient, accurate, and stable methods for the determination of residual halogenated solvents in olive oil is imperative. In this paper, a method based on automatic headspace gas chromatography was established for the determination of residual halogenated solvents, namely, chloroform, carbon tetrachloride, 1,1,1-trichloroethane, dibromochloromethane, tetrachloroethylene, and bromoform, in olive oil. The samples were processed as follows. After mixing, 2.00 g (accurate to 0.01 g) of the olive oil sample was added into a 20 mL headspace injection bottle and immediately sealed for headspace gas chromatography analysis. Blank virgin olive oil was used to prepare a standard working solution and the external standard method for quantification. The solvents used in the preparation of halogenated solvent standard intermediates were investigated and methanol was selected as a replacement for N,N-dimethylacetamide to prepare a halogenated solvent standard intermediate owing to its safety. The effects of different injection times (1, 2, 3, 4, 5, 6 s), equilibration temperatures (60, 70, 80, 90, 100, 110, 120 ℃), and equilibration times (4, 5, 8, 10, 20, 30, 40 min) of the headspace sampler on the detection of the residual amounts of the six halogenated solvents were investigated. The optimal injection time and equilibration temperature were 3 s and 90 ℃, respectively. The method demonstrated good analytical performance for the six halogenated solvents when the equilibration time was 30 min. A methodological study was conducted on the optimized method, and the results showed that the six halogenated solvents exhibited good linear relationships in the range of 0.002-0.200 mg/kg, with correlation coefficients of ≥0.9991. The limits of detection (LODs) and quantification (LOQs) of 1,1,1-trichloroethane and bromoform were 0.0006 and 0.002 mg/kg, respectively. The LODs and LOQs of chloroform, carbon tetrachloride, dibromochloromethane, and tetrachloroethylene were 0.0003 and 0.001 mg/kg, respectively. The average recoveries under different spiked levels were 85.53%-115.93%, and the relative standard deviations (n=6) were 1.11%-8.48%. The established method was used to analyze 13 olive oil samples available in the market. Although no halogenated solvents were detected in these samples, a limited number of samples does not represent all olive oils. Hence, monitoring residual halogenated solvents in olive oil remains necessary for its safe consumption. The LOQs of the method for the six halogenated solvents were significantly lower than that of the COI/T.20/Doc. No. 8-1990 standard method (0.02 mg/kg). In addition, the developed method can be conducted under short operation times with high precision and degree of automation as well as good accuracy. Thus, the proposed method is suitable for the determination and analysis of the residues of the six halogenated solvents in large batches of olive oil samples.

[Transformation mechanism of carbon tetrachloride and the associated micro-ecology in landfill cover, a typical functional layer zone]

Landfill is one of the important sources of carbon tetrachloride (CT) pollution, and it is important to understand the degradation mechanism of CT in landfill cover for better control. In this study, a simulated landfill cover system was set up, and the biotransformation mechanism of CT and the associated micro-ecology were investigated. The results showed that three stable functional zones along the depth, i.e., aerobic zone (0-15 cm), anoxic zone (15-45 cm) and anaerobic zone (> 45 cm), were generated because of long-term biological oxidation in landfill cover. There were significant differences in redox condition and microbial community structure in each zone, which provided microbial resources and favorable conditions for CT degradation. The results of biodegradation indicated that dechlorination of CT produced chloroform (CF), dichloromethane (DCM) and Cl^- in anaerobic and anoxic zones. The highest concentration of dechlorination products occurred at 30 cm, which were degraded rapidly in aerobic zone. In addition, CT degradation rate was 13.2-103.6 μg/(m²·d), which decreased with the increase of landfill gas flux. The analysis of diversity sequencing revealed that Mesorhizobium, Thiobacillus and Intrasporangium were potential CT-degraders in aerobic, anaerobic and anoxic zone, respectively. Moreover, six species of dechlorination bacteria and eighteen species of methanotrophs were also responsible for anaerobic transformation of CT and aerobic degradation of CF and DCM, respectively. Interestingly, anaerobic dechlorination and aerobic transformation occurred simultaneously in the anoxic zone in landfill cover. Furthermore, analysis of degradation mechanism suggested that generation of stable anaerobic-anoxic-aerobic zone by regulation was very important for the harmless removal of full halogenated hydrocarbon in vadose zone, and the increase of anoxic zone scale enhanced their removal. These results provide theoretical guidance for the removal of chlorinated pollutants in landfills.

Emissions estimates of carbon tetrachloride for 1992-2014 in China

Discrepancies in emission estimates of carbon tetrachloride (CCl₄, CTC), between bottom-up and top-down methods, have been shown since the 1990s at both the global and regional scale. This study estimates the emissions of China from 1992 to 2014 based on emission functions and aggregated activity information given reasonable uncertainties. The results show that emissions increase from 7.3 Gg/yr (5.6-9.1 Gg/yr at 95% confidential interval) to 14.0 (9.1-19.5) Gg/yr with a growth rate of 6.7 (1.9-11.4) %/yr during 1992-2002 and then decrease to a minimum of 4.3 (1.9-8.0) Gg/yr in 2011. More than 54% of the emissions during 1992-2009 are from the process agents sector. The estimates are comparable with those of other studies and those in this study based on observations during 2011-2014 using the interspecies correlation method. China's contribution to global emissions increases from 7.5% to 19.5% during 1992-2009, but the contribution is reduced to 9.9% and 8.0% in 2010 and 2011, respectively, indicating the effectiveness of compliance with the Montreal Protocol and its subsequent Amendments and Adjustments, whereby CTC emissions are phased-out. The results of this study are beneficial for narrowing the gap between bottom-up estimates and top-down emission calculations of CTC in China.

Fabrication of bimetallic Ag/Fe immobilized on modified biochar for removal of carbon tetrachloride

As an effective conventional absorbent, biochar exhibited limited adsorption ability toward small hydrophobic molecules. To enhance the adsorption capacity, a novel adsorbent was prepared by immobilizing nanoscale zero-valent iron onto modified biochar (MB) and then the elemental silver was attached to the surface of iron (Ag/Fe/MB). It's noted that spherical Ag/Fe nanoparticles with diameter of 51nm were highly dispersed on the surface of MB. As the typical hydrophobic contaminant, carbon tetrachloride was selected for examining the removal efficiency of the adsorbent. The removal efficiencies of carbon tetrachloride by original biochar (OB), Ag/Fe, Ag/Fe/OB and Ag/Fe/MB were fully investigated. It's found that Ag/Fe/MB showed higher carbon tetrachloride removal efficiency, which is about 5.5 times higher than that of the OB sample due to utilizing the merits of high adsorption and reduction. Thermodynamic parameters revealed that the removal of carbon tetrachloride by Ag/Fe/MB was a spontaneous and exothermic process, which was affected by solution pH, initial carbon tetrachloride concentration and temperature. The novel Ag/Fe/MB composites provided a promising material for carbon tetrachloride removal from effluent.

Atmospheric carbon tetrachloride in rural background and industry surrounded urban areas in Northern Iberian Peninsula: Mixing ratios, trends, and potential sources

Latest investigations on atmospheric carbon tetrachloride (CTC) are focused on its ozone depleting potential, adverse effects on the human health, and radiative efficiency and Global Warming Potential as a greenhouse gas. CTC mixing ratios have been thoroughly studied since its restriction under the Montreal Protocol, mostly in remote areas with the aim of reporting long-term trends after its banning. The observed decrease of the CTC background mixing ratio, however, was not as strong as expected. In order to explain this behavior CTC lifetime should be adjusted by estimating the relative significance of its sinks and by identifying ongoing potential sources. Looking for possible sources, CTC was measured with high-time resolution in two sites in Northern Spain, using auto-GC systems and specifically developed acquisition and processing methodologies. The first site, Bilbao, is an urban area influenced by the surrounding industry, where measurements were performed with GC-MSD for a one-year period (2007-2008). The second site, at Valderejo Natural Park (VNP), is a rural background area where measurements were carried out with GC-FID and covering CTC data a nonsuccessive five-year period (2003-2005, 2010-2011, and 2014-2015years). Median yearly CTC mixing ratios were slightly higher in the urban area (120pptv) than in VNP (80-100pptv). CTC was reported to be well mixed in the atmosphere and no sources were noticed to impact the rural site. The observed long-term trend in VNP was in agreement with the estimated global CTC emissions. In the urban site, apart from industrial and commercial CTC sources, chlorine-bleach products used as cleaning agents were reported as promotors of indoor sources.

[Evaluation on the capability of testing carbon tetrachloride, benzene, methylbenzene, dimethylbenzene, p' p-DDT of the provincial centers for disease control and prevention]

OBJECTIVE

To evaluate the Centers of Disease Control and Prevention's (CDC) provincial divisions' capabilities of detectingconcentrations of organic parameters such as carbon tetrachloride, benzene, methylbenzene, dimethylbenzene and pesticide parameter of p’ p-DDT in drinking water, by adopting a quality control assessment methodology of interlaboratory comparison.

METHODS

All laboratories had been divided into 2 groups, each of which contained aboutl6 laboratories. Organic concentrations and pesticide concentrations were assigned to 2 sample groups. Testing capabilities of the laboratories were evaluated through the use of robust statistical methods.

RESULTS

Thirty CDC provincial divisions, including municipalities under the central government and in autonomous regions, participated in this interlaboratory comparison. Twenty laboratories obtained positive results in all parameters, accounting for 66.7%. Eight laboratories' results were suspicious, accounting for 26.7%. Finally, 2 laboratories produced outliers, accounting for 6.7%.

CONCLUSIONS

The majority of provincial CDC participants in this interlaboratory comparison are capable of testing the concentrations of organic parameterssuch as carbon tetrachloride, benzene, and methylbenzene, dimethyl benzene, and pesticide concentrations of p' p-DDT in drinking water.

Enhanced dechlorination of carbon tetrachloride by Geobacter sulfurreducens in the presence of naturally occurring quinones and ferrihydrite

The effect of naturally occurring quinones including lawsone (LQ), ubiquinone (UQ), juglone (JQ), and 1,4-naphthoquinone (NQ) on the biotransformation of carbon tetrachloride (CT) in the presence of Geobacter sulfurreducens and ferrihydrite was investigated. AQDS was used as the model compound for comparison. The reductive dissolution of ferrihydrite by G. sulfurreducens was enhanced by AQDS, NQ, and LQ. However, addition of UQ and JQ had little enhancement effect on Fe(II) production. The bioreduction efficiency and rate of ferrihydrite was highly dependent on the natural property and concentration of quinone compounds and the addition of low concentrations of LQ and NQ significantly accelerated the biotransformation rate of CT. The pseudo-first-order rate constants for CT dechlorination (kobsCT) in AQDS-, LQ- and NQ-amended batches were 5.4-5.8, 4.6-7.4 and 2.4-5.8 times, respectively, higher than those in the absence of quinone. A good relationship between kobsCT for CT dechlorination and bioreduction ratio of ferrihydrite was observed, indicating the important role of biogenic Fe(II) in dechlorination of CT under iron-reducing conditions. Spectroscopic analysis showed that AQDS and NQ could be reduced to semiquinones and hydroquinones, while only hydroquinones were generated in LQ-amended batches.

Seasonal and diurnal variations of atmospheric peroxyacetyl nitrate, peroxypropionyl nitrate, and carbon tetrachloride in Beijing

Atmospheric peroxyacetyl nitrate (PAN), peroxypropionyl nitrate (PPN), and carbon tetrachloride (CCl4) were measured from September 2010 to August 2011 in Beijing. PAN exhibited low values from mid-autumn to early spring (October to March) with monthly average concentrations ranging from 0.28 to 0.73 ppbV, and increased from early spring to summer (March to August), ranging from 1.37-3.79 ppbV. The monthly variation of PPN was similar to PAN, with low values (below detection limit to 0.18 ppbV) from mid-autumn to early spring, and a monthly maximum in September (1.14 ppbV). The monthly variation of CCl4 was tightly related to the variation of temperature, exhibiting a minimum in winter (69.3 pptV) and a maximum of 180.6 pptV in summer. Due to weak solar intensity and short duration, PAN and O3 showed no distinct diurnal patterns from morning to night during winter, whereas for other seasons, they both exhibited maximal values in the late afternoon (ca. 15:00 to 16:00 local time) and minimal values during early morning and midnight. Good linear correlations between PAN and PPN were found in autumn (R = 0.91), spring (R = 0.94), and summer (R = 0.81), with slopes of 0.130, 0.222, and 0.133, respectively, suggesting that anthropogenic hydrocarbons dominated the photochemical formation of PANs in Beijing. Positive correlation between PAN and O3 in summer with the low slopes (deltaO3/deltaPAN) ranging from 9.92 to 18.0 indicated serious air pollution in Beijing, and strong negative correlation in winter reflected strong O3 consumption by NO titration and less thermal decompositin of PAN.

Chip-scale Mid-Infrared chemical sensors using air-clad pedestal silicon waveguides

Towards a future lab-on-a-chip spectrometer, we demonstrate a compact chip-scale air-clad silicon pedestal waveguide as a Mid-Infrared (Mid-IR) sensor capable of in situ monitoring of organic solvents. The sensor is a planar crystalline silicon waveguide, which is highly transparent, between λ = 1.3 and 6.5 μm, so that its operational spectral range covers most characteristic chemical absorption bands due to bonds such as C-H, N-H, O-H, C-C, N-O, C=O, and C≡N, as opposed to conventional UV, Vis, Near-IR sensors, which use weaker overtones of these fundamental bands. To extend light transmission beyond λ = 3.7 μm, a spectral region where a typical silicon dioxide under-clad is absorbing, we fabricate a unique air-clad silicon pedestal waveguide. The sensing mechanism of our Mid-IR waveguide sensor is based on evanescent wave absorption by functional groups of the surrounding chemical molecules, which selectively absorb specific wavelengths in the mid-IR, depending on the nature of their chemical bonds. From a measurement of the waveguide mode intensities, we demonstrate in situ identification of chemical compositions and concentrations of organic solvents. For instance, we show that when testing at λ = 3.55 μm, the Mid-IR sensor can distinguish hexane from the rest of the tested analytes (methanol, toluene, carbon tetrachloride, ethanol and acetone), since hexane has a strong absorption from the aliphatic C-H stretch at λ = 3.55 μm. Analogously, applying the same technique at λ = 3.3 μm, the Mid-IR sensor is able to determine the concentration of toluene dissolved in carbon tetrachloride, because toluene has a strong absorption at λ = 3.3 μm from the aromatic C-H stretch. With our demonstration of an air-clad silicon pedestal waveguide sensor, we move closer towards the ultimate goal of an ultra-compact portable spectrometer-on-a-chip.

Subsoil heterogeneities controlling porewater contaminant mass and microbial diversity at a site with a complex pollution history

This study seeks to improve our understanding of the conceptual model of pollutant transport and fate in cases of DNAPL contamination at sites with a complex contamination history. The study was carried out in an unconfined aquifer of alluvial fans in the Tarragona Petrochemical Complex (Spain). Two boreholes were drilled and continuous cores were recovered in order to carry out a detailed core description at centimeter scale and a comprehensive sampling of borehole cores. The biogeochemical heterogeneity at these sites is controlled by the conjunction of lithological, hydrochemical and microbiological heterogeneities. Biodegradation processes of contaminant compounds take place not only at the level of the dissolved fraction in the aquifer but also at the level of the fraction retained in the fine, less conductive materials as shown by the biodegradation haloes of parent and metabolite compounds. Sampling the low-conductivity levels also allowed us to identify compounds, e.g. BTEX, that are the remaining traces of the passage of old contaminant plumes whose sources no longer exist. This enabled us to describe past biogeochemical processes and to partially account for the processes occurring today. Transition zones, characterized by numerous textural changes, constitute ecotones whose biostimulation could be effective in promoting the acceleration of the remediation of the multiple pollution at these sites.

[Implementation of an electronic nose for rapid detection of volatile chloralkane and chloroalkene]

An electronic nose, core detector of which was composed of three metal-doped SnO2 gas sensors and a photo ionization detector (PID) as a sensor array, was developed for rapid detection of volatile chloralkane and chloroalkene. A gas recognition model was developed based on test and analysis with nine of pure gas and five of mixtures, and then the electronic nose was applied to several water samples and the validity was evaluated with a gas chromatography. The results revealed that the sensor array responded differently between the chloralkane and chloroalkene. PID was less sensitive to chloralkane, while linearly responded to chloroalkene (R2 > 0.997). Sensor TGS2602 performed sensitive to carbon tetrachloride (CT), trichloromethane (TCM) and 1,2-dichloroethane (1,2-DCA), with a linear response to the former two but a poor linear response to 1,2-DCA. Sensors TGS2600 and TGS2620 were by far more sensitive and linearly (R2 > 0.995) responded to dichloromethane (DCM) and 1,2-DCA. Therefore in the final gas recognition model, PID was used to determine the concentration of chloroalkene, sensor TGS2602 was used to determine CT and TCM, sensor TGS2600 or TGS2620 was used to determine DCM and 1,2-DCA. When applied to gas mixtures, sensor TGS2602 responded less sensitive than the sum of the response to each single component, while other sensors responded equally. The electronic nose showed a determined result linearly correlated to GC (R2 > 0.96) as applied to samples with a mixture of DCM and perchloroethylene.

Ligand-assisted degradation of carbon tetrachloride by microscale zero-valent iron

Degradation of carbon tetrachloride (CT) by microscale zero-valent iron (ZVI) was investigated in batch systems with or without organic ligands (ethylenediaminetetraacetic acid (EDTA), citric acid, tartaric acid, malic acid and oxalic acid) at pHs from 3.5 to 7.5. The results demonstrated that at 25°C, the dechlorination of CT by microscale ZVI is slow in the absence of organic ligands, with a pseudo-first-order rate constant of 0.0217 h(-1) at pH 3.5 and being further dropped to 0.0052 h(-1) at pH 7.5. However, addition of organic ligands significantly enhanced the rates and the extents of CT removal, as indicated by the rate constant increases of 39, 31, 32, 28 and 18 times in the presence of EDTA, citric acid, tartaric acid, malic acid and oxalic acid, respectively, at pH 3.5 and 25°C. The effect of EDTA was most significant; the dechlorination of CT at an initial concentration of 20 mg l(-1) increased from 16.3% (no ligands) to 89.1% (with EDTA) at the end of 8h reaction. The enhanced CT degradation in the presence of organic ligands was primarily attributed to the elimination of a surface passivation layer of Fe(III) (hydr)oxides on the microscale ZVI through chelating of organic ligands with Fe(III), which maintained the exposure of active sites on ZVI surface to CT.

[Determination of chloroform and carbon tetrachloride in residential air by capillary gas chromatography]

OBJECTIVE

To establish solvent desorption capillary gas chromatography method for determination of chloroform and carbon tetrachloride in residential air.

METHODS

The sample was absorbed by active carbon glass tube, then desorbed by Acetone and determined by Capillary Gas Chromatography.

RESULTS

Linear range of this method: 5.0 x 10(-4)-1.0 x 10(-1) mg/m3 for chloroform, 1.9 x 10(-4)-1.0 x 10(-2) mg/m3 for carbon tetrachloride. The sample could be stored in the active carbon glass tube for 7 days. The re-occurrence rate of this method is good. RSD is: 0.41%-1.54% for chloroform, 0.31%-1.03% for carbon tetrachloride. Detection limit of this method: 1.5 x 10(-3) ng for chloroform, and 5.8 x 10(-4) ng for carbon tetrachloride. Recovery rate for different concentrations: 88.5%-98.6% For chloroform, and 91.0%-99.0% for carbon tetrachloride. Sampling efficiency: 93.7%-99.2% for chloroform, and 90.6%-99.2% for carbon tetrachloride. Other Volatile halogenated hydrocarbons with similar structures and similar nature in the residential air do not interfere the measurement.

CONCLUSION

The method was easy and quick, with high sensibility. It was applicable to monitor the chloroform and carbon tetrachloride in residential air.

Sonochemical degradation of perchloroethylene: the influence of ultrasonic variables, and the identification of products

Sonochemistry is a technique that offers promise for pollutant degradation, but earlier studies on various chlorinated substrates do not give a definitive view of the effectiveness of this methodology. We now report a thorough study of ultrasonic operational variables upon perchloroethylene (PCE) degradation in water (variables include ultrasonic frequency, power and system geometry as well as substrate concentration) and we attempt to close the mass balance where feasible. We obtained fractional conversions of >97% showing very effective loss of pollutant starting material, and give mechanistic proposals for the reaction pathway based on cavitational phenomena inducing pyrolytic and free radical processes. We note major products of Cl(-) and CO(2)/CO, and also trichloroethylene (TCE) and dichloroethylene (DCE) at ppm concentrations as reported earlier. The formation at very low (ppb) concentration of small halocompounds (CHCl(3), CCl(4)) and also of higher-mass species, such as pentachloropropene, hexachloroethane, is noteworthy. But of particular importance in our work is the discovery of significant quantities of chloroacetate derivatives at ppm concentrations. Although these compounds have been described as by-products with other techniques such as radiolysis or photochemistry, this is the first time that these products have been identified in the sonochemical treatment of PCE; this allows a much more effective account of the mass balance and may explain earlier inconsistencies. This reaction system is now better identified, but a corollary is that, because these haloacetates are themselves species of some toxicity, the use of ultrasound here may not sufficiently diminish wastewater toxicity.

Desorption behavior of carbon tetrachloride and chloroform in contaminated low organic carbon aquifer sediments

Slow release behavior of carbon tetrachloride (CCl(4)) and chloroform (CHCl(3)) in low organic carbon (<0.1%) deep aquifer sediments was quantified by 1-D column desorption studies with intact cores. The compounds had been in contact with the sediments for 30years. Comparison of the CCl(4) distribution coefficient (K(d)) from this study with those from short contact time experiments suggested that CCl(4)K(d)'s calculated from site contaminated sediments of long contact time are likely a factor of 10 or more higher than those calculated from short contact-time lab experiments. A significant portion of the CHCl(3) mass (55% to more than 90%) was resistant to aqueous desorption in sediments with clay contents ranging from 2.0% to 36.7% and organic carbon content ranging from 0.017% to 0.088%. In contrast, CCl(4) showed greatest mass retention (31% or more) only in the highest clay and organic carbon content sediment. Relatively easy solvent extraction of the residual masses of CCl(4) and CHCl(3) from the sediments indicated the compounds were not permanently sequestered. Tracer breakthrough in columns was well behaved, indicating interparticle diffusion was not causing the slow release behavior. Diffusion out of intraparticle pores is suggested to be the main process governing the observed behavior although, diffusion out of natural organic matter cannot be ruled out as a potential contributing factor. The half-life for release of the slow fraction of CHCl(3) mass from sediments was estimated to be in the range of weeks (100h) to months (1100h). Neither CCl(4) or CHCl(3) were detected at measurable levels in the column effluent of one of the sediments even though a significant mass fraction of CHCl(3) was found present on the sediment following desorption suggesting that our estimate of hundreds to thousands of hours for complete release of CHCl(3) masses from such sediment is conservative.

[Health risk analysis of VOC/SVOC contaminated soil in an abandoned chemical plant]

Environmental health risk of contaminated soil in a typical abandoned industry was analyzed based on the full field investigation according to the site assessment procedure of American Society for Testing and Material (ASTM). Parameters were modified with the combination of Chinese crowd character and site specifics. Results indicated that the site was mainly contaminated with volatile and semi-volatile organic compounds in soil profiles. And the contents of carbon tetrachloride, tetrachloroethylene, pentachloroethane, hexachlorobutadiene, hexachloroethane and hexachlorobenzene in soil samples were exceeded the national environmental standard. These contaminants ranked the carcinogenic risks and hazard quotients more than 10(-2) and 1 in some locations with the exposure by oral ingestion, dermal contact and inhalation. Contaminants in this site had resulted in the high health risks to the residents and surrounding communities. The risk should be reduced to the health acceptable level by the treatment and remediation before further development for residential and commercial utilization.

Comparison of atmosphere/aquatic environment concentration ratio of volatile chlorinated hydrocarbons between temperate regions and Antarctica

For the purpose of understanding the transport and deposition mechanisms and the air-water distribution of some volatile chlorinated hydrocarbons (VCHCs), their atmosphere/aquatic environment concentration ratio was evaluated. In addition, for the purpose of differentiating VCHC behaviour in a temperate climate from its behaviour in a polar climate, the atmosphere/aquatic environment concentration ratio evaluated in matrices from temperate zones was compared with the concentration ratio evaluated in Antarctic matrices. In order to perform air samplings also at rigid Antarctic temperatures, the sampling apparatus, consisting of a diaphragm pump and canisters, was suitably modified. Chloroform, 1,1,1-trichloroethane, tetrachloromethane, 1,1,2-trichloroethylene and tetrachloroethylene were measured in air, water and snow using specific techniques composed of a purpose-made cryofocusing-trap-injector (for air samples) and a modified purge-and-trap injector (for aqueous samples) coupled to a gas chromatograph with mass spectrometric detection operating in selected ion monitoring mode. The VCHCs were retrieved in all the investigated matrices, both Italian and Antarctic, with concentrations varying from tens to thousands of ng m(-3) in air and from digits to hundreds of ng kg(-1) in water and snow. The atmosphere/aquatic environment concentration ratios were always found to be lower than 1. In particular, the Italian air/water concentration ratios were smaller than the Antarctic ones, by reason of the higher atmospheric photochemical activity in temperate zones. On the other hand, the Antarctic air/snow concentration ratios proved to be largely in favour of snow with respect to the Italian ratios, thus corroborating the hypothesis of a more efficient VCHC deposition mechanism and accumulation on Antarctic snow.

Characterization of the chronic risk and hazard of hazardous air pollutants in the United States using ambient monitoring data

BACKGROUND

Ambient measurements of hazardous air pollutants (air toxics) have been used to validate model-predicted concentrations of air toxics but have not been used to perform risk screening at the national level.

OBJECTIVES

We used ambient concentrations of routinely measured air toxics to determine the relative importance of individual air toxics for chronic cancer and noncancer exposures.

METHODS

We compiled 3-year averages for ambient measurement of air toxics collected at monitoring locations in the United States from 2003 through 2005. We then used national distributions of risk-weighted concentrations to identify the air toxics of most concern.

RESULTS

Concentrations of benzene, carbon tetrachloride, arsenic, 1,3-butadiene, and acetaldehyde were above the 10(-6) cancer risk level at most sites nationally with a high degree of confidence. Concentrations of tetrachloroethylene, ethylene oxide, acrylonitrile, and 1,4-dichlorobenzene were also often greater than the 10(-6) cancer risk level, but we have less confidence in the estimated risk associated with these pollutants. Formaldehyde and chromium VI concentrations were either above or below the 10(-6) cancer risk level, depending on the choice of agency-recommended 10(-6) level. The method detection limits of eight additional pollutants were too high to rule out that concentrations were above the 10(-6) cancer risk level. Concentrations of 52 compounds compared with chronic noncancer benchmarks indicated that only acrolein concentrations were greater than the noncancer reference concentration at most monitoring sites.

CONCLUSIONS

Most pollutants with national site-level averages greater than health benchmarks were also pollutants of concern identified in modeled national-scale risk assessments. Current monitoring networks need more sensitive ambient measurement techniques to better characterize the air toxics problem in the United States.

[Carcinogenic hazard of chloroform and other drinking water chlorination by-products]

The paper presents the results of studying the carcinogenic effect of chloroform and its combination with carbon tetrachloride, 1,2-dichloroethane, trichloroethylene during chronic oral administration to F1(CBAxC57Bl6) mice. There is a relationship between the manifestation of carcinogenesis to the dose of chloroform and a combination of chemicals, as well as its enhancement upon exposure to the combination as compared with acute administration of chloroform. Exposure to a combination of substances at the level of their maximum permissible concentrations does not affect carcinogenesis. The possible mechanisms of the specific features of carcinogenesis in this experiment are discussed.

Physical control on CCl4 and CHCl3 desorption from artificially contaminated and aged sediments with supercritical carbon dioxide

The long-term interactions of carbon tetrachloride (CCl(4)) and chloroform (CHCl(3)) with sediments that are low in organic matter (OM) are not well studied. In this study, CCl(4) and CHCl(3) were mixed with supercritical carbon dioxide (CO(2)) and loaded onto columns packed with two sediments with low OM and different textures, to establish contamination and achieve expedited artificial aging. The columns were subsequently leached with a simulated groundwater under hydraulically saturated conditions. Scanning electron microscopy was used to inspect the morphology of sediment single particles, determine the degree of particle association in aggregates and qualitatively estimate porosity and the possible diffusional pathways that might affect the overall contaminant desorption rates. Results demonstrated that most of contaminant inventories were rapidly released in the first pore volume of effluent, although a small portion of contaminants' total mass exhibited time-dependent desorption. The calculated K(d) values of CCl(4) or CHCl(3) partition were negligibly small. Both contaminants had similar transport behavior which was simulated well with a distributed (multiple)-rate (DR) statistical model. The model accounted for the apparent contaminant mass transfer through diffusional pathways of different lengths, towards the advective pores. The distribution of contaminant mass between equilibrium and kinetic fractions, the distribution of the individual rate constants, and the average rate constants calculated with the parameters of the gamma-distribution function (beta and eta) of the DR model, were sediment (texture) dependent. This indicated that contaminant desorption during the late stage of leaching was driven by concentration gradients (i.e., diffusion) within sediment matrix porosity.

Using artificial burrows to evaluate inhalation risks to burrowing mammals

Since the onset of plutonium production at the U.S. Department of Energy's Hanford Site, several hundred cubic meters of carbon tetrachloride (CCl4) has been discharged to the soil column, resulting in a dispersed CCI4 vapor plume in the subsurface. Inhalation of volatile organic chemicals could be an important exposure pathway for burrowing animals there. Historical levels of CCl4 in soil pore gas exceeded the inhalation ecological screening level for CCl4. Thus, the inhalation exposure pathway was evaluated with the use of artificial burrows deployed at locations that had elevated levels of CCl4 in soil gas. Artificial burrows were designed on the basis of information available for Hanford Site fossorial wildlife. After installation, the artificial burrow atmosphere was sampled and analyzed for CCl4 and its degradation products: chloroform, methylene chloride, and chloromethane. Sampling was repeated on 3 occasions to capture varying atmospheric conditions affecting exposure concentrations. CCl4 was detected in the artificial burrows, and maximum exposures were observed during relatively low barometric conditions. The highest CCl4 detections were still well below the inhalation-based ecological screening level and CCl4 degradation products were never detected. This study shows that artificial burrows are an efficient method for obtaining relevant exposure data and illustrates the utility of directly measuring the medium for exposure under ecologically realistic conditions.

Photocatalytic decomposition of CCl4 on Zr-MCM-41

Photocatalytic decomposition of CCl4 (80 mg L(-1) in H2O) effected by Zr-MCM-41 (Zr incorporated in the amorphous wall of MCM-41) has been studied in the present work. Experimentally, photocatalytic decomposition of CCl4 on Zr-MCM-41 was enhanced by about 1.96 times over that on ZrO2. Photocatalytic decomposition of CCl4 may proceed via a two-electron transfer process that yields mainly CHCl3, Cl- and H2. Since little C2Cl2, C2Cl6 or CH2Cl2 was found, it is unlikely that CHCl3 involved in the secondary photocatalytic degradation process. In addition, photocatalytic splitting of H2O on Zr-MCM-41 was also enhanced. The yield of H2 was 6.5 mmol(gZrO2)(-1). About 68% of this hydrogen (6.5 mmol(gZrO2)(-1)) was consumed in the photocatalytic decomposition of CCl4.

The flux of chloroform and tetrachloromethane along an elevational gradient of a coastal salt marsh, East China

The fluxes of trichloromethane (CHCl(3), CM) and tetrachloromethane (CCl(4), TCM) were seasonally measured using static flux chambers over an annual cycle in a coastal salt marsh, East China. The salt marsh presented as a large sink for both the compounds in the growing season (from April to October), but it was a minor source for the gas species in the non-growing season. Generally, the cordgrass marsh acted as a sink of CM and TCM. The net consumption of CM and TCM observed in the study marsh may result from the high ambient atmospheric concentrations and enriched soil organic matter that result in anoxic sediments. Higher plants were suggested to be an important sink for CM and TCM in the growing season, but a net source in the non-growing season. However, the mechanism responsible for the plant removal process is not clear.

A sensitive spectrophotometric method for determination of carbon tetrachloride with the aid of ultrasonic decolorization of methyl orange

A sensitive method for carbon tetrachloride (CCl(4)) determination has been developed with the aid of ultrasonic oxidation decolorization of methyl orange (MO). It is found that the ultrasonic oxidation decolorization rate of MO can be significantly promoted by adding a little amount of CCl(4). The increased ultrasonic decolorization rate of MO is strongly dependent on the concentration of CCl(4) added, and a linear correlation is observed between the amount of CCl(4) and the decolorization rate of MO in the ultrasonic oxidation process. Thus, the CCl(4) determination is transformed to a simple and direct determination of the decoloration extent of MO solution at a given concentration. As an indirect spectrophotometric determination of CCl(4), the new method is sensitive and easy of operation with a maximum wavelength of 508 nm, molar absorptivity of 3.83 x 10(4) L mol(-1) cm(-1), and a Sandell sensitivity of 7.96 x 10(-3) microg cm(-2). Under optimized conditions, Beer's law is obeyed in the range of 0.4-20 mg L(-1) of CCl(4) (DL=0.19 mg L(-1), r=0.9996). The concentrations of CCl(4) in several practical samples have been determined satisfactorily by using this method.

Effect of soil moisture dynamics on dense nonaqueous phase liquid (DNAPL) spill zone architecture in heterogeneous porous media

The amount, location, and form of NAPL in contaminated vadose zones are controlled by the spatial distribution of water saturation and soil permeability, the NAPL spill scenario, water infiltration events, and vapor transport. To evaluate the effects of these processes, we used the three-phase flow simulator STOMP, which includes a new permeability-liquid saturation-capillary pressure (k-S-P) constitutive model. This new constitutive model considers three NAPL forms: free, residual, and trapped. A 2-D vertical cross-section with five stratigraphic layers was assumed, and simulations were performed for seven cases. The conceptual model of the soil heterogeneity was based upon the stratigraphy at the Hanford carbon tetrachloride (CT) spill site. Some cases considered co-disposal of NAPL with large volumes of wastewater, as also occurred at the Hanford CT site. In these cases, the form and location of NAPL were most strongly influenced by high water discharge rates and NAPL evaporation to the atmosphere. In order to investigate the impact of heterogeneity, the hydraulic conductivity within the lower permeability layer was modeled as a realization of a random field having three different classes. For six extreme cases of 100 realizations, the CT mass that reached the water table varied by a factor of two, and was primarily controlled by the degree of lateral connectivity of the low conductivity class within the lowest permeability layer. The grid size at the top boundary had a dramatic impact on NAPL diffusive flux just after the spill event when the NAPL was present near the ground surface. NAPL evaporation with a fine grid spacing at the top boundary decreased CT mass that reached the water table by 74%, compared to the case with a coarse grid spacing, while barometric pumping had a marginal effect for the case of a continuous NAPL spill scenario considered in this work. For low water infiltration rate scenarios, the distribution of water content prior to a NAPL spill event decreased CT mass that reached the water table by 98% and had a significant impact on the formation of trapped NAPL. For all cases simulated, use of the new constitutive model that allows the formation of residual NAPL increased the amount of NAPL retained in the vadose zone. Density-driven advective gas flow from the ground surface controlled vapor migration in strongly anisotropic layers, causing NAPL mass flux to the lower layer to be reduced. These simulations indicate that consideration of the formation of residual and trapped NAPLs and dynamic boundary conditions (e.g., areas, rates, and periods of different NAPL and water discharge and fluctuations of atmospheric pressure) in the context of full three-phase flow are needed, especially for NAPL spill events at the ground surface. In addition, NAPL evaporation, density-driven gas advection, and NAPL vertical movement enhanced by water flow must be considered in order to predict NAPL distribution and migration in the vadose zone.

Expression of heat shock protein and hemoglobin genes in Chironomus tentans (Diptera, chironomidae) larvae exposed to various environmental pollutants: a potential biomarker of freshwater monitoring

To identify a sensitive biomarker of freshwater monitoring, we evaluated pollutant-induced expression of heat shock proteins (HSPs) and hemoglobins (Hbs) genes in the larvae of the aquatic midge Chironomus tentans (Diptera, Chironomidae). As pollutants, we examined nonylphenol, bisphenol-A, 17alpha-ethynyl estradiol, bis(2-ethylhexyl) phthalate, endosulfan, paraquat dichloride, chloropyriphos, fenitrothion, cadmium chloride, lead nitrate, potassium dichromate, benzo[a]pyrene and carbon tetrachloride. We also investigated larval growth as a physiological descriptor by measuring changes in the body fresh weight and dry weight after chemical exposure. The response of the HSPs gene expression by chemical exposure was rapid and sensitive to low chemical concentrations but it was not stressor specific. Interestingly, an increase in the expression of HSPs genes was observed not only in a stress inducible form (HSP70), but also in a constitutively (HSC70) expressed form. The expression of Hb genes showed chemical-specific responses: that is, alkyl phenolic compounds increased the expression of hemoglobin genes, whereas pesticides decreased the expression. As expected, molecular-level markers were more sensitive than physiological endpoints, suggesting that gene expression could be developed as an early warning biomarker in this animal. The overall results suggest that the expression of HSP and Hb genes in Chironomus could give useful information for diagnosing general health conditions in fresh water ecosystem. The expression of Hb genes, in particular, seems to be a promising biomarker, especially in view of the potential of Chironomus larvae as a biomonitoring species and of the physiological particularities of their respiratory pigments.

Comparative study of infrared and Raman spectra of CCl4 in vapour and condensed phases: effect of LO-TO splitting resulting from hetero-isotopic TD-TD interactions

Salient features of an in-depth comparative study of infrared and Raman spectra of CCl(4) in vapour, liquid and condensed phases are presented. Wavenumbers of nu(4), nu(1)+nu(4), nu(3) and 2 nu(3) modes of CCl(4) vapour in infrared and Raman spectra are found to be in good agreement. Analysis of the vibrational spectra of liquid CCl(4) together with the spectroscopic observations on solid CCl(4) at low temperatures reveal TD-TD interaction amongst various CCl(4) isotopes in condensed states. The concept of LO-TO splitting of dipole active nu(3) and nu(1)+nu(4) Fermi doublet have been invoked to explain several features of the vibrational spectra of liquid CCl(4). There is significant strengthening of Fermi resonance interaction between nu(3) and nu(1)+nu(4) modes of CCl(4) in condensed phases relative to that in vapour phase. The Fermi resonance interaction parameter W has been found to be independent of molecular environment.

Synergic quenching effects of water and carbon tetrachloride in liquid scintillation gel samples

Although both water and carbon tetrachloride induce chemical quenching when incorporated to Insta Gel, the quenching power of carbon tetrachloride is nearly two orders of magnitude greater than that of water. This huge difference shows how different the chemical quenching mechanisms among quenchers can be. One remarkable fact of all pure beta-ray nuclides is that calibration curves do not depend on the water to scintillator volume ratio or on the nature of the quencher. The fact is clearly surprising, because two tritium samples of different water to scintillator and quencher to scintillator volume ratios may have identical counting efficiencies. As we shall prove, this fact is only possible when the external quench parameter of both samples is the same. We study the synergies in quenching generated when carbon tetrachloride is added to a sample in gel phase.

[Contamination by disinfection byproducts (DPBs) and microbiological quality of dialysis water: a study in an Italian hospital dialysis service]

Maintaining a high standard of quality of dialysis fluid has been shown to be difficult. For this reason, an evaluation of the microbiological quality (total bacterial count at 22 degrees C and 37 degrees C, pyrogenic Pseudomonas, Staphylococcus, Acinetobacter and Enterobacteriaceae) and contamination by disinfection byproducts, of dialysis fluids was carried out in a hospital dialysis service in Arezzo (Italy). The analysis was carried out in different points of the water treatment system used for the preparation of dialysis fluids. Results show diffuse microbiological contamination especially at the point of entry of the dialyzer monitor; Staphylococcus and Pseudomonas were found to be the most frequent contaminants due to the presence of biofilms in the water system, while pyrogenic bacteria were found to be within regulatory limits. Trichloroethane and trichloroethylene were absent but traces of carbon tetrachloride, percloroethylene and bromoform were found; these were outnumbered by trialomethanes (chloroform at point of entry decalcifier: mean 90.14 microg/L). Contamination by trialomethanes decreased at the end of the distribution system (mean chloroform 8.55 microg/L). The yearly level of exposure of a dialysis patient to low molecular weight volatile halogenated organics (VHOs) that are able to pass the dialyser membrane, was therefore estimated to be approximately 100 mg.

Carbon isotope fractionation in the reductive dehalogenation of carbon tetrachloride at iron (hydr)oxide and iron sulfide minerals

Compound-specific isotope analysis (CSIA) is used increasingly in contaminant hydrology in the attempt to assess the nature as well as the extent of in situ transformation reactions. Potentially, variations of stable isotope ratios along a contaminant plume may be used to quantify in situ degradation. In the present study, the abiotic dehalogenation of CCl4 by Fe(II) present at the surface of different iron minerals has been characterized in terms of the reaction rates and carbon isotopic fractionation (delta13C) of carbon tetrachloride (CCl4) as well as the yields and isotopic signatures of chloroform (CHCl3), one of the main transformation products. The abiotic reductive dehalogenation of CCl4 was associated with substantial carbon isotopic enrichment effects. The observed enrichment factors, e, correlated neither with the surface-normalized reaction rate constants nor with the type of products formed but fell into two distinctly different ranges for the two principal groups of minerals studied. With iron (hydr)oxide minerals (goethite, hematite, lepidocrocite, and magnetite) and with siderite, the e-values for CCl4 dehalogenation were remarkably similar (-29 +/- 3 per thousand). Because this value matches well with the theoretical estimates for the cleavage of an aliphatic C-Cl bond, we suggest that dissociative electron transfer to CCl4 controls the reaction rates for this group of iron minerals. Conversely, CCl4 transformation by different preparations of the iron sulfide mackinawite was accompanied by a significantly lower carbon istotopic fractionation (e = -15.9 +/- 0.3 per thousand), possibly due to the presence of nonfractionating rate-determining steps or a significantly different transition state structure of the reaction. Isotopically sensitive branching of the reaction pathways (i.e., the effect of different product distributions on isotope fractionation of CCl4) did not play a significant role in our systems. The extensive data set presented in this study opens new perspectives toward an improved understanding of the factors that determine reaction mechanisms and isotopic fractionation of dehalogenation reactions by Fe(II) at iron containing minerals.

[Halogenated volatile organic compounds in bottled mineral water and soft drinks]

74 mineral natural water samples and 56 samples of different commercial drinks have been analysed by head-space chromatography in order to evidence the presence of volatile halogenated organic compounds (VHO). Trihalomethanes (THM) as drinking water chlorination by-products and trichloroethane, carbon tetrachloride, trichloroethylene and tetrachloroethylene as ubiquitarious substances have been investigated. The presence of VHO has been evidenced in 20,3% of mineral natural water samples and in the 58,9% of the commercial soft drinks: this latest group has usually shown higher levels of the investigated compounds. The results of the present study has been compared with a similar study performed in 1991 in the same area: the VHO values observed in the present study appear to be lower than those obtained in the previous study.

pH dependence of carbon tetrachloride reductive dechlorination by magnetite

Magnetite is precipitated by dissimilatory iron-reducing bacteria or forms through corrosion of zero-valent iron (ZVI) in permeable reactive barriers. Reduction of carbon tetrachloride (CCl4) by synthetic magnetite was examined in batch reactors to evaluate the pH dependence of the reaction rates and product distributions. This work presents the first data where magnetite promotes CCl4 dechlorination independent of added sorbed Fe(II) or coexisting minerals that maintained Fe2+ above the magnetite solubility limit. In this system, reaction rate constants increase with increasing pH values between 6 and 10. The pH dependence is explained by acid-base equilibrium between two surface sites, where the more deprotonated exhibits greater dechlorination reactivity. The distribution of reaction products was also found to depend on pH. The primary reaction product is carbon monoxide (CO) followed by chloroform (CHCl3). CHCl3 production is at a minimum at pH 6 but increases through pH 10. Formation rate constants for both products increase with increasing pH, but the values for CHCl3 increase at a much faster rate. A hypothesis is proposed that relates the CHCl3 rate enhancement to the reduced capacity of deprotonated surface sites to stabilize the trichlorocarbanion transition-state complex. These data form a basis to assess the natural attenuation capacity of magnetite formed under iron reducing conditions. Application of this information to permeable barrier technology suggests that, in the long term, oxidation of ZVI to magnetite may be accompanied by a shift toward more benign reaction products as well as a 2 order of magnitude decrease in reaction rate constants.

[Preparation of a novel activated carbon coating fiber for solid phase micro-extraction and its application for halocarbon compound analysis in water]

A novel activated carbon coating fiber used for solid phase micro-extraction (SPME) was prepared using activated carbon powder and silica resin adhesive. The extraction properties of the novel activated carbon coating fiber were investigated. The results indicate that this coating fiber has high concentration ability, with enrichment factors for chloroform, carbon tetrachloride, trichloroethylene and tetrachloroethylene in the range of 13.8 to 18.7. The fiber is stable at temperature as high as 290 degrees C and it can be used for over 140 times at 250 degrees C. The activated carbon coating fiber was then applied to the analysis of the four halocarbon compounds mentioned above. A linear correlation with correlation coefficients between 0.995 2 and 0.999 4 and the detection limits between 0.008 and 0.05 microg/L were observed. The method was also applied to a real water sample analysis and the recoveries of these halocarbon compounds were from 95.5% to 104.6%.

Synergistic effect of copper ion on the reductive dechlorination of carbon tetrachloride by surface-bound Fe(II) associated with goethite

The dechlorination of carbon tetrachloride (CT) by Fe(II) associated with goethite in the presence of transition metal ions was investigated. X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (XRPD) were used to characterize the chemical states and crystal phases of transition metals on solid phases, respectively. CT was dechlorinated to chloroform (CF) by 3 mM Fe(II) in 10 mM goethite (25.6 m2 L(-1)) suspensions. The dechlorination followed pseudo-first-order kinetics, and a rate constant (k(obs)) of 0.036 h(-1) was observed. Transition metal ions have different effects on CT dechlorination. The addition of Ni(II), Co(II), and Zn(II) lowered the k(obs) for CT dechlorination, whereas the amendment of 0.5 mM Cu(II) into the Fe(II)-Fe(III) system significantly enhanced the efficiency and the rate of CT dechlorination. The k(obs) for CT dechlorination with 0.5 mM Cu(II) was 1.175 h(-1), which was 33 times greater than that without Cu(II). Also, the dechlorination of CT by surface-bound iron species is pH-dependent, and the rate constants increased from 0.008 h(-1) at pH 4.0 to 1.175 h(-1) at pH 7.0. When the solution contained Cu(II) and Fe(II) without goethite, a reddish-yellow precipitate was formed, and the concentration of Fe(ll) decreased with the increase in Cu(II) concentration. XPS and XRPD analyses suggested the possible presence of Cu2O and ferrihydrite in the precipitate. Small amounts of aqueous Cu(I) were also detected, reflecting the fact that Cu(II) was reduced to Cu(I) by Fe(II). A linear relationship between k(obs) for CT dechlorination and the concentration of Cu(II) was observed when the amended Cu(II) concentration was lower than 0.5 mM. Moreover, the k(obs) for CT dechlorination was dependent on the Fe(II) concentration in the 0.5 mM Cu(II)-amended goethite system and followed a Langmuir-Hinshelwood relationship. These results clearly indicate that Fe(II) serves as the bulk reductant to reduce both CT and Cu(II). The resulting Cull) can further act as a catalyst to enhance the dechlorination rate of chlorinated hydrocarbons in iron-reducing environments.

Soluble asialoglycoprotein receptors reflect the apoptosis of hepatocytes

Cell death is thought to take place through at least two distinct processes: apoptosis and necrosis. There is increasing evidence that dysregulation of the apoptotic program is involved in liver diseases. However, there is no method to simply evaluate apoptosis in the liver tissue at present. It has been reported that the expression of asialoglycoprotein receptors (AGPRs) increases with apoptosis, but there is no report until now that investigates the influence of soluble AGPRs on apoptosis of hepatocytes. Soluble AGPRs have been reported to be present in human serum under physiological conditions. In the present study, in order to investigate the correlation between apoptosis of hepatocytes and soluble AGPR, mouse soluble AGPRs were detected using SDS-PAGE and Western blot analysis was conducted using anti-extracellular mouse hepatic lectin-1 (Ex-MHL-1) antiserum (polyclonal rabbit serum). The mouse soluble AGPRs were present in culture medium and mouse serum when hepatocytes were damaged. The soluble AGPRs increased proportionately, as the number of dead hepatocytes increased. In addition, soluble AGPRs existed more when apoptotic cell death was observed in in vitro and in vivo than when necrotic cell death was observed. The extracellular moiety of MHL-1 exists in the culture medium and mouse serum as a soluble AGPR, but the detailed mechanism of releasing soluble AGPR from hepatocytes has not been revealed yet. We described the first evidence for the relation between quantity of soluble AGPRs with two kinds of cell death: necrosis and apoptosis. Based on the results of our study, soluble AGPRs might become a new marker of apoptosis in the liver tissue and be useful for clinical diagnosis and treatment for liver diseases.

Highly enhanced photoreductive degradation of perchlorinated compounds on dye-sensitized metal/TiO2 under visible light

This study reports an example of visible-light photocatalyst based on TiO2 modified by ruthenium-complex sensitizers and noble metal deposits. The photodegradation of trichloroacetate (TCA) and carbon tetrachloride was used as a probe reaction for evaluating the visible light activity of the photocatalyst under the illumination of lambda > 420 nm. Photodeposition of platinum nanoparticles on dye-sensitized TiO2 (Pt/TiO2/Ru(II)L3) drastically enhanced the degradation rate of TCA and CCl4. The visible light reactivity of Pt/TiO2/Ru(II)L3 was optimal with [Ru(II)L3] = 10 microM, [TiO2] = 0.5 g/L, and Pt loading of about 0.2 wt %. Although no electron donors to regenerate the oxidized Ru-sensitizers were added in the aqueous suspension, the photoreductive dechlorination of perchlorinated compounds proceeded far beyond the stoichiometric limit of the initial sensitizer concentration. Water acted as an electron donor to regenerate the sensitizer with a concurrent production of dioxygen. On the other hand, Pt/TiO2/Ru(II)L3 was completely inactive in the presence of dissolved oxygen and the in-situ generated dioxygen gradually decelerated the dechlorination rate. Conduction band electrons transferred to O2 in preference to CCl4 and TCA on Pt deposits. Other noble metals (Ag, Au, and Pd) deposited on TiO2 showed a better oxygen-tolerance but less visible-light reactivity than PtTiO2/Ru(II)L3. Effects of metal loading on the visible light activity and its implications for the efficientvisible-light photocatalyst development are discussed.

Direct quantification of human serum albumin in human blood serum without separation of gamma-globulin by the total internal reflected resonance light scattering of thorium-sodium dodecylbenzene sulfonate at water/tetrachloromethane interface

A direct quantification of human serum albumin (HSA) in blood serum samples without separation is proposed based on the measurements of total internal reflected resonance light scattering (TIR-RLS) at water/tetrachloromethane (H(2)O/CCl(4)) interfaces. In the pH range of 6.37-6.59, the coadsorption of the binary complex of HSA-Th(IV) with sodium dodecylbenzene sulfonate occurs at the H(2)O/CCl(4) interface, forming an amphiphilic layer and displaying greatly enhanced TIR-RLS signals with the maximum peak located at 340-370 nm. The enhanced TIR-RLS intensity is in proportion to the HSA concentration in the range 0.15-1.0 micro gml(-1). The limit of detection is 14.4 ngml(-1). The contents of HSA in blood serum samples were determined with the recovery of 97.1-102.3% and RSD of 0.6-2.9%, which are identical to those obtained according to the spectrofluorimetric method using chrome azurol S.

Risks to the public from historical releases of radionuclides and chemicals at the Rocky Flats Environmental Technology Site

This paper summarizes the methods and results of estimating risks of cancer incidence resulting from plutonium, carbon tetrachloride, and beryllium releases from operations at the Rocky Flats Environmental Technology Site, near Denver, Colorado, from 1953 through 1989. The key findings show that people who lived near the facility were exposed to plutonium mainly through inhalation during routine operations, from a major fire in 1957, and from plutonium resuspended from contaminated soil from an outdoor drum storage area, called the 903 Area. Results were presented for five exposure scenarios that were location-independent. Individuals described by the laborer scenario received the highest risk of all scenarios considered. Upper bound (95th percentile) incremental lifetime cancer incidence risks for the laborer scenario were in about the 10(-4) range (1 chance in 10,000) for developing cancer from Rocky Flats plutonium releases during a lifetime. At the 5th percentile level, the maximum cancer risk was about 10(-7) (1 chance in 10 million) for developing cancer during a lifetime. Estimated cancer risks at the 95th percentile level are within the range of for acceptable risks established by the US Environmental Protection Agency of 10(-6) to 10(-4). Carbon tetrachloride was found to be the chemical that presented the highest risk to the public. The 5th and 95th percentile risk values for exposure to carbon tetrachloride were 9.2x10(-7) and 2.5x10(-5), respectively.

Development, operation, and long-term performance of a full-scale biocurtain utilizing bioaugmentation

A full-scale field evaluation of bioaugmentation was conducted in a carbon tetrachloride (CT)- and nitrate-impacted aquifer at Schoolcraft, MI. The added organism was Pseudomonas stutzeri KC (strain KC), a denitrifying bacterium that cometabolically degrades CT without producing chloroform (CF). To introduce and maintain strain KC in the aquifer, a row of closely spaced (1-m) injection/extraction wells were installed normal to the direction of groundwater flow near the leading edge of the CT plume. The resulting system of wells was used to establish and maintain a "biocurtain" for CT degradation through the intermittent addition of base to create favorable pH conditions; inoculation; and weekly addition of acetate (electron donor), alkali, and phosphorus. Although half of the test zone was inoculated twice, the long-term performance of both sections was indistinguishable: both had high CT removal efficiencies (median of 98-99.9%) and similar levels of strain KC colonization (>10(5) strain KC/g). Sustained and efficient (98%) removal of CT has now been observed over 4 yr. Transient low levels of CF (<20 ppb) and H2S (<2 ppm) were observed, but both disappeared when the concentration of acetate in the weekly feed was reduced. Nitrate removal efficiencies ranged from 60% at low acetate concentrations to nearly 100% at high acetate concentrations. We conclude that closely spaced wells and intermittent substrate addition are effective means of delivering organisms and substrates to subsurface environments. At the Schoolcraft site, we achieved uniform removal efficiencies over a significant vertical depth (15 m), despite significant variability in hydraulic conductivity. This was accomplished by pumping 65% (v/v) of the natural gradient flow passing through the biocurtain during a given week in a single 6-h pumping event. Approximately 18,600 m3 of contaminated groundwater was treated during the project.

First measurements of carbon tetrachloride and tetrachloroethene in the atmosphere of Athens, Greece

Levels of carbon tetrachloride and tetrachloroethene were determined for the first time in Athens in the summer of 2000. The mean CCl4 and C2Cl4 concentrations were 0.060 and 0.18 ppb, respectively. CCl4 did not exhibit significant variation throughout the measurement period or with wind direction. C2Cl4 under strong eastern winds had less than half the concentrations observed during other meteorological conditions. No diurnal variation was observed for either compound.

[Determination of chloroform and tetrachloro-methane in water with capillary column-microECD]

The method of determination of chloroform and tetrachloro-methane in water with capillary column-microECD had better and wider linear range and lower detection limit. At the range of 0-10 micrograms/L chloroform and 0-1 microgram/L tetrachloro-methane, the regression equation were calculated as Y = 1.959X + 4.816 (r = 0.9910) and Y = 3.947X + 42.58 (r = 0.9970). The lowest detection limit were 0.1032 microgram/L chloroform and 0.01219 microgram/L tetrachloro-methane. This method not only simplified the operating processes, but also increase the sensitivity, and reavled better precision and accuracy.

Total internal reflected resonance light scattering determination of chlortetracycline in body fluid with the complex cation of chlortetracycline-europium-trioctyl phosphine oxide at the water/tetrachloromethane interface

A highly selective method of chlortetracycline (CTC) is proposed on the basis of the measurements of total internal reflected resonance light scattering (TMR-RLS) at water/tetrachloromethane (H20/CCl4) interfaces. In the pH range of 7.54-8.14, the interaction of the binary complex of Eu(III)/CTC in the presence of trioctyl phosphine oxide (TOPO) occurs at the H20/CCl4 interface, resulting in greatly enhanced TIR-RLS signals with the maximum peak located at 340 nm. The enhanced TIR-RLS intensity is in proportion to the CTC concentration in the range 0.98 to approximately 20.0 x 10(-7) mol/L. The limit of detection is 9.8 x 10(-9) mol/L. Synthetic samples and body fluid samples including human urine, human serum, and fresh milk were determined with the recovery of 95.4-106.4% and RSD of 2.9-3.9%.

Noninvasive determination of the location and distribution of DNAPL using advanced seismic reflection techniques

Recent advances in seismic reflection amplitude analysis (e.g., amplitude versus offset-AVO, bright spot mapping) technology to directly detect the presence of subsurface DNAPL (e.g., CCl4) were applied to 216-Z-9 crib, 200 West Area, DOE Hanford Site, Washington. Modeling to determine what type of anomaly might be present was performed. Model results were incorporated in the interpretation of the seismic data to determine the location of any seismic amplitude anomalies associated with the presence of high concentrations of CCl4. Seismic reflection profiles were collected and analyzed for the presence of DNAPL. Structure contour maps of the contact between the Hanford fine unit and the Plio/Pleistocene unit and between the Plio/Pleistocene unit and the caliche layer were interpreted to determine potential DNAPL flow direction. Models indicate that the contact between the Plio/Pleistocene unit and the caliche should have a positive reflection coefficient. When high concentrations of CCl4 are present, the reflection coefficient of this interface displays a noticeable positive increase in the seismic amplitude (i.e., bright spot). Amplitude data contoured on the Plio/Pleistocene-caliche boundary display high values indicating the presence of DNAPL to the north and east of the crib area. The seismic data agree well with the well control in areas of high concentrations of CCl4.

Cyclohexane as an alternative vapor of carbon tetrachloride for the assessment of gas removing capacities of gas masks

An alternative vapor was explored to replace carbon tetrachloride (CCl4) for testing breakthrough times of cartridges and canisters of gas masks in the National Approval Test of Respirators. Cyclohexane was single out as a candidate for the alternative vapor out of six vapors: trichloroethylene, n-pentane, n-hexane, n-heptane, toluene and cyclohexane from the viewpoints of similarity of vapor pressure and water-solubility to CCl4, lower toxicity than CCl4, and technical feasibility in generating an airflow of 30 L/min containing the vapor ranging from 300 to 5000 ppm. Breakthrough times of cartridges and canisters were examined by generating cyclohexane vapor in a test airflow of 30 L/min in comparison with CCl4 vapor under various test conditions with different vapor concentrations and relative humidities (RH). As the results, the breakthrough times of the cartridges and canisters for cyclohexane were found to almost coincide with those for CCl4 under all examined range of concentrations and RH. By an increase of humidity from 50% RH to 80% RH, the cartridges showed significant shortening of breakthrough times for both of CCl4 and cyclohexane, but the susceptibility of the breakthrough time of cyclohexane to humidity was also similar to that of CCl4. It was, therefore, concluded that cyclohexane can be recommended as the alternative vapor of CCl4 for testing the breakthrough times of gas mask cartridges and canisters in the National Approval Test.

ATR-FTIR sensor development for continuous on-line monitoring of chlorinated aliphatic hydrocarbons in a fixed-bed bioreactor

This article describes the continuous on-line monitoring of a dechlorination process by a novel attenuated total reflection-Fourier transform infrared (ATR-FTIR) sensor. This optical sensor was developed to measure noninvasively part-per-million (ppm) concentrations of trichloroethylene (TCE), tetrachloroethylene (PCE), and carbon tetrachloride (CT) in the aqueous effluent of a fixed-bed dechlorinating bioreactor, without any prior sample preparation. The sensor was based on an ATR internal reflection element (IRE) coated with an extracting hydrophobic polymer, which prevented water molecules from interacting with the infrared (IR) radiation. The selective diffusion of chlorinated compound molecules from aqueous solution into the polymer made possible their detection by the IR beam. With the exclusion of water the detection limits were lowered, and measurements in the low ppm level became possible. The best extracting polymer was polyisobutylene (PIB) in the form of a 5.8-microm thick film, which afforded a detection limit of 2, 3, and 2. 5 mg/L (ppm) for TCE, PCE, and CT, respectively. Values of the enrichment factors between the polymer coating and the water matrix of these chloro-organics were determined experimentally and were compared individually with predictions obtained from the slopes of absorbance/concentration curves for the three analytes. Before coupling the ATR-FTIR sensor to the dechlorinating bioreactor, preliminary spectra of the chlorinated compounds were acquired on a laboratory scale configuration in stop-flow and flow-through closed-loop modes. In this way, it was possible to study the behavior and direct response of the optical sensor to any arbitrary concentration change of the analytes. Subsequently, the bioreactor was monitored with the infrared sensor coupled permanently to it. The sensor tracked the progression of the analytes' spectra over time without perturbing the dechlorinating process. To calibrate the ATR-FTIR sensor, a total of 13 standard mixtures of TCE, PCE and CT at concentrations ranging from 0 to 60 ppm were selected according to a closed symmetrical experimental design derived from a 3(2) full-factorial design. The above range of concentrations chosen for calibration reflected typical values during normal bioreactor operation. Several partial least squares (PLS) calibration models were generated to resolve overlapping absorption bands. The standard error of prediction (SEP) ranged between 0.6 and 1 ppm, with a relative standard error of prediction (RSEP) between 3 and 6% for the three analytes. The accuracy of this ATR-FTIR sensor was checked against gas chromatography (GC) measurements of the chlorocompounds in the bioreactor effluents. The results demonstrate the efficiency of this new sensor for routine continuous on-line monitoring of the dechlorinating bioreactor. This strategy is promising for bioprocess control and optimization.

[Determination of volatile halohydrocarbons in drinking water by gas chromatography with direct aqueous injection]

The volatile CHCl3, CCl4, CHBrCl2, CHBr2Cl, CHBr3 in drinking water have been determined by wide bore capillary gas chromatography/electron capture detector(GC/ECD) with direct aqueous injection method. The method is simple, fast and highly sensitive. It has better accuracy and precision. When the average mass concentration of five halohydrocarbons ranged from 9.03 to 20.19 micrograms/L, the relative deviations ranged from 5.7% to 9.1%, RSD ranged from 2.9% to 7.5%. The standard deviations ranged from 0.3 to 0.9. Correlation coefficients were 0.998 and 0.999. The detection limits ranged from 0.1 to 0.7 microgram/L and were lower than those in other work when the temperature of ECD was 350 degrees C.

Volatile organic compounds in the surface waters of northern Greece

An investigation into the occurrence of volatile organic compounds (VOCs) was conducted for a period of two years in the surface waters of Northern Greece. Samples from four rivers and five lakes were taken seasonally and analyzed for VOCs. The analysis has been performed by purge-and-trap (PAT) gas chromatographic-mass spectrometric (GC-MS) technique. The most commonly encountered VOCs in surface waters were chloroform, carbon tetrachloride, trichloroethylene, dichlorobromomethane, tetrachloroethylene, and chlorodibromomethane.