Electrostatic sampler for semivolatile aerosols: chemical artifacts

Electrostatic precipitators (ESPs) show promise as an alternative sampling method for semivolatile aerosols because they are less susceptible to adsorptive and evaporative artifacts than filter based methods. However, the corona discharge may after the chemical composition of a sampled aerosol. Chemical artifacts associated with electrostatic precipitation of semivolatile aerosols were investigated in the laboratory. ESPs and filters sampled both particles and vapors of alkanes, polycyclic aromatic hydrocarbons, and alkenes across varying concentrations. Gravimetric measurements between the two sampling methods were well correlated. Ozone generated by the ESP corona was the primary cause of alkene reactions in the gas phase. Particles collected within the corona region were vulnerable to irradiation by corona ions overtime. Particles collected outside the corona region did not react. Vapors passing through the corona reacted to a lesser extent. Vapors captured after passing through the ESP reacted with ozone that was not removed by the vapor trap. Chemical speciation of highly reactive compounds (i.e., alkenes or other compounds with relatively short half-lives outdoors) is not appropriate with ESPs. Electrostatic precipitation of these compounds is appropriate, however, when total organic carbon is of interest as the ESP does not alter the amount of mass measured gravimetrically. ESPs can make accurate measurements of more persistent semivolatile compounds, such as alkanes and PAHs.     

毛纺用化学品毒性毒理数据库的建立

文章就我国毛纺行业用化学品现状进行了分析,对毛纺中常用化学品进行分类、归纳和总结,根据目前化学品毒性研究成果,提出毛纺工业用化学品毒性毒理数据库建立的基本思想,设计出了数据库的基本框架和查询方法.从化学品安全的角度提出毛纺用化学品的毒性分级建议及依据,指出了构效关系在高毒性化学品替代和数据库建设方面的重要作用.     

Passive monitoring method for 3-ethenylpyridine: a marker for environmental tobacco smoke

A new method was developed to assess environmental tobacco smoke in air. The method is based on passive sampling and subsequent measurement of the concentration of 3-ethenylpyridine, a vapor-phase compound specific to tobacco smoke. Air samples were collected using a 3M organic vapor monitor. Tests were carried out in a dynamic chamber to determine the sampling rate (25.7 cm3/min). 3-Ethenylpyridine was desorbed from the sampler with 1 mL of pyridine/toluene mixture. 3-Ethenylpyridine was quantified by gas chromatography/mass spectrometry. The limit of detection was 0.01 microgram/sample, corresponding to a concentration of 0.27 microgram/m3 air calculated for a sampling period of 24 h. Field measurements were carried out to test the performance of the method. Mean concentrations ranging from 1.3 to 5.3 micrograms/m3 were measured for 3-ethenylpyridine in smoking environments, but no 3-ethenylpyridine was detected in nonsmoking environments. Active sampling using charcoal tubes was used as a reference method in the chamber tests and field measurements. Individual exposures can be easily and accurately measured by means of the passive sampler. Because of simple sample treatment, the method is also well-suited for large-scale monitoring of environmental tobacco smoke.     

Passive sampling and analyses of common dissolved fixed gases in groundwater

An in situ passive sampling and gas chromatographic protocol was developed for analysis of the major and several minor fixed gases (He, Ne, H2, N2, O2, CO, CH4, CO2, and N2O) in groundwater. Using argon carrier gas, a HayeSep DB porous polymer phase, and sequential thermal conductivity and reductive gas detectors, the protocol achieved sufficient separation and sensitivity to measure the mixing ratio of all these gases in a single 0.5 mL gas sample collected in situ, stored, transported, and injected using a gastight syringe. Within 4 days of immersion in groundwater, the simple passive in situ sampler, whether initially filled with He or air, attained an equivalent and constant mixing ratio for five of the seven detected gases. The abundant mixing ratio of N2O, averaging 2.6%, indicated that significant denitrification is likely ongoing within groundwater contaminated with uranium, acidity, nitrate, and organic carbon from a group of four closed radioactive wastewater seepage ponds at the Oak Ridge Field Research Center. Over 1000 passive gas samples from 12 monitoring wells averaged 56% CO2, 32.4% N2, 2.6% O2, 2.6% N2O, 0.21% CH4, 0.093% H2, and 0.025% CO with an average recovery of 95 +/- 14% of the injected gas volume.     

Major issues regarding the efficiency of monitoring programs for nitrate contaminated groundwater

Major issues regarding the efficiency of moni toring programs for nitrate contaminated groundwater are analyzed in this paper: (i) representativeness of monitoring networks; (ii) correct interpretation of the monitoring data and resulting time series and trends; and (iii) differentiation among the different sources of nitrates in groundwater. Following an overview of the nitrate contamination problem and possible solutions, as well as some of the difficulties found, a relatively straightforward method for assessing monitoring network representativity is presented, namely interpolation standard error assessment. It is shown how nitrate-concentration time series resulting from periodic observations can be corrected with a conservative tracer, in order to avoid misinterpretation and confirm or correct apparent trends. Finally, coupled 1?N and 1?O isotope signatures of nitrate (NO??) in groundwater are used to differentiate among nitrogen (N) sources, to ensure correct targeting of restoration measures. The case study regards a Nitrate Vulnerable Zone in the south of Portugal, designated in compliance with the European Nitrates Directive, where coastal discharge of nutrient-rich groundwater threatens the good qualitative and ecological status of the Ria Formosa coastal lagoon. Results show that mineral fertilizer is the main source of N in groundwater, and that increases in N load can be masked by dilution phenomena.     

Application of toxicological risk assessment principles to the chemical constituents of cigarette smoke

Data sources: International Agency for Research on Cancer Monographs; California and US Environmental Protection Agency cancer potency factors (CPFs) and reference exposure levels; scientific journals and government reports from the USA, Canada, and New Zealand.

Study selection: This was an inclusive review of studies reporting yields of cigarette smoke constituents using standard ISO methods.

Data extraction: Where possible, the midpoint of reported ranges of yields was used.

Data synthesis: Data on 158 compounds in cigarette smoke were found. Of these, 45 were known or suspected human carcinogens. Cancer potency factors were available for 40 of these compounds and reference exposure levels (RELs) for non-cancer effects were found for 17. A cancer risk index (CRI) was calculated by multiplying yield levels with CPFs. A non-cancer risk index (NCRI) was calculated by dividing yield levels with RELs. Gas phase constituents dominate both CRI and NCRI for cigarette smoke. The contribution of 1,3-butadiene (BDE) to CRI was more than twice that of the next highest contributing carcinogen (acrylonitrile) using potencies from the State of California EPA. Using those potencies from the USEPA, BDE ranked third behind arsenic and acetaldehyde. A comparison of CRI estimates with estimates of smoking related cancer deaths in the USA showed that the CRI underestimates the observed cancer rates by about fivefold using ISO yields in the exposure estimate.

Conclusions: The application of toxicological risk assessment methods to cigarette smoke provides a plausible and objective framework for the prioritisation of carcinogens and other toxicant hazards in cigarette smoke. However, this framework does not enable the prediction of actual cancer risk for a number of reasons that are discussed. Further, the lack of toxicology data on cardiovascular end points for specific chemicals makes the use of this framework less useful for cardiovascular toxicity. The bases for these priorities need to be constantly re-evaluated as new toxicology information emerges.

     

Environmental monitoring of hydrocarbons: a chemical sensor perspective

Assessing the environmental impact of organic pollutants requires reliable analytical tools that can rapidly screen them with minimal sample handling. Chemical sensors are expected to play an increasing role in environmental monitoring, and recent technological advances are certain to facilitate the application of chemical sensing devices. The search for highly selective, sensitive, low cost, stable, and robust sensors for hydrocarbons is an area of interest that is reflected by many publications on this topic. This report surveys some of the work that has been undertaken using sensors to detect hydrocarbons in the gas and liquid phase. The analytical capabilities of various sensors are compared and discussed in terms of their selectivity, sensitivity, and detection limit. It was found that the sensitivity is highly dependent on the experimental conditions used in the preparation of the sensing surface. Many sensors display acceptable sensitivity under controlled laboratory conditions; however, very few are selective enough to distinguish among several hydrocarbons in complex mixtures. Selectivity is still a challenge that is hindering the widespread application of chemical sensors for environmental monitoring of hydrocarbons and a number of strategies have been proposed to help overcome some of these problems.     

Assessment of chemical mixtures and groundwater effects on Daphnia magna transcriptomics

Small organisms can be used as biomonitoring tools to assess chemicals in the environment. Chemical stressors are especially hard to assess and monitor when present as complex mixtures. Here, fifteen polymerase chain reaction assays targeting Daphnia magna genes were calibrated to responses elicited in D. magna exposed for 24 h to five different doses each of the munitions constituents 2,4,6-trinitrotoluene, 2,4-dinitrotoluene, 2,6-dinitrotoluene, trinitrobenzene, dinitrobenzene, or 1,3,5-trinitro-1,3,5-triazacyclohexane. A piecewise-linear model for log-fold expression changes in gene assays was used to predict response to munitions mixtures and contaminated groundwater under the assumption that chemical effects were additive. The correlations of model predictions with actual expression changes ranged from 0.12 to 0.78 with an average of 0.5. To better understand possible mixture effects, gene expression changes from all treatments were compared using high-density microarrays. Whereas mixtures and groundwater exposures had genes and gene functions in common with single chemical exposures, unique functions were also affected, which was consistent with the nonadditivity of chemical effects in these mixtures. These results suggest that, while gene behavior in response to chemical exposure can be partially predicted based on chemical exposure, estimation of the composition of mixtures from chemical responses is difficult without further understanding of gene behavior in mixtures. Future work will need to examine additive and nonadditive mixture effects using a much greater range of different chemical classes in order to clarify the behavior and predictability of complex mixtures.     

Automated sampler for the measurement of non-methane organic compounds

An automated sampler has been constructed for the unattended collection of whole-air samples in Summa passivated stainless steel canisters. The sampler consists of a Viton diaphragm pump; a differential-pressure flow controller; a 2-position, 3-port valve; a 10-port multiposition valve; and a digital valve sequence programmer that controls the sequence and timing of the electrically actuated valves. All connecting tubing was constructed from Silcosteel tubing. Two configurations of the automated sampler and a passive collection system were evaluated by comparing the combined sampling precisions of the three systems with the analytic precision, derived from replicate analyses of an ambient air sample. The analytic precision was generally < +/- 5%, with higher values observed for analytes with mixing ratios in the tens of pptv. However, analytic precision values for methanol and ethanol were poor, greater than +/- 20%. Values for sampling precision were greater by about a factor of 2 than the analytic precision. The poor results for the light oxygenated hydrocarbons could be caused by sorption of the analytes in the preconcentration and sampling systems and difficulties in peak integration.     

Environmental consequences of water pumped from greater New Orleans following Hurricane Katrina: chemical, toxicological, and infaunal analysis

The U.S. Army Engineer Research and Development Center Environmental Laboratory, Vicksburg, MS, conducted a study to determine the extent to which Hurricane Katrina floodwaters in the New Orleans, Louisiana area may have had impacts on wildlife habitat and other biological resources in surrounding areas. These studies were conducted as part of the Interagency Performance Evaluation Taskforce, an investigation of environmental impacts originating from the failure of the hurricane protection system during Hurricane Katrina. This paper presents data regarding the effects of pumped floodwaters on sediment chemistry, toxicity, and benthic invertebrate assemblages near pumping stations that discharged floodwaters into marshes near Chalmette and Violet, Louisiana. Chemical contamination of sediments was observed and varied among sample locations (e.g., outfall locations, wastewater treatment plant, canals, and wetlands); however, trends in the chemistry data were not always consistent with bioassay results. A comparison of the sediment chemistry data from this study with three other studies reporting concentrations of chemicals in sediments within the city of New Orleans suggested that sediments and associated contaminants present within the levees were not pumped into the marsh in appreciable quantities.     

Passive dosing of soil invertebrates with polycyclic aromatic hydrocarbons: limited chemical activity explains toxicity cutoff

The partitioning of organic soil pollutants into soil organisms is driven by their chemical activity, which normally does not exceed that of the pure pollutant. Passive dosing with the silicone poly(dimethylsiloxane) (PDMS) was used to initiate and maintain the maximum chemical activity of 10 polycyclic aromatic hydrocarbons (PAHs) in toxicity tests with the springtail Folsomia candida. The test animals could move freely on the PDMS saturated with PAHs, resulting in direct contact and exposure to saturated air. After 7 days, springtail lethality correlated neither with the octanol-water partition coefficients of the PAHs nor with their molecular size, but with their melting point All low-melting PAHs (T(M) < or = 110 degrees C) caused 100% lethality, whereas all high-melting PAHs (TM > or = 180 degrees C) caused no significant lethality. The lethality was successfully fitted to one chemical activity response curve for all PAHs tested, with effective chemical activity causing 50% lethality (Ea-50) of 0.058. It was also fitted to the PAH concentration in the PDMS, resulting in an EC(PDMS)-50 of 8.7 mM. Finally, the combined exposure to anthracene and pyrene was described by the sum of chemical activities causing lethality, in good agreement with the chemical activity-response curve obtained.     

热喷涂长效防腐——化工厂设备防腐的必然趋势

在20世纪30年代,英国某大桥由24个工人承担桥体的油漆涂刷工作,从桥的一端刷到另一端,历时3年。当涂刷完整座桥时发现,桥的始端又出现了锈蚀,不得不重新从头起刷漆。实际上,在几十年漫长的岁月中,整座大桥每天都有24个工人在刷油漆。 1961年,英国普利茅期Tamar公路大桥采用了热喷涂技术,将锌、铝等有色金属喷涂到钢铁表面,直到现在使用良好。这种采用复合防腐蚀的方法,叫做热喷涂长效防腐。     

Evaluation of the chemical residue monitoring in animal-derived products in Switzerland

This paper evaluates whether the Swiss monitoring programme for foreign substances in animal products fulfils basic epidemiological quality requirements, and identifies possible sources of bias in the selection of samples. The sampling was analysed over a 4-year period (2002-05). The sampling frame in 37 participating abattoirs covered 51% of all slaughtered pigs, 73% of calves, 68% of beef and 36% of cows. The analysis revealed that some sub-populations as defined by the region of origin were statistically over-represented while others were under-represented. The programme that is in accordance with European Union requirements contained some relevant bias. Patterns of under-sampled regions characterized by management type differences were identified. This could lead to an underestimate of the number of contaminated animals within the programme. Although the current sampling was stratified and partially risk-based, its efficiency could be improved by adopting a more targeted approach.     

Enhanced in situ bioremediation of BTEX-contaminated groundwater by combined injection of nitrate and sulfate

Enhancement of in situ anaerobic biodegradation of BTEX compounds was demonstrated at a petroleum-contaminated aquifer in Seal Beach, CA. Specifically, combined injection of nitrate and sulfate into the contaminated aquifer was used to accelerate BTEX removal as compared to remediation by natural attenuation. An array of multi-level sampling wells was used to monitor the evolution of the in situ spatial distributions of the electron acceptors and the BTEX compounds. Nitrate was utilized preferentially over sulfate and was completely consumed within a horizontal distance of 4-6 m from the injection well; sulfate reduction occurred in the region outside the denitrifying zone. By combining injection of both nitrate and sulfate, the total electron acceptor capacity was enhanced without violating practical considerations that limit the amount of nitrate or sulfate that can be added individually. Degradation of total xylene appears linked to sulfate utilization, indicating another advantage of combined injection versus injection of nitrate alone. Benzene degradation also appears to have been stimulated by the nitrate and sulfate injection close to the injection well but only toward the end of the 15-month demonstration. The results are consistent with the hypothesis that benzene can be biodegraded anaerobically after other preferentially degraded hydrocarbons have been removed.     

Mycotoxins and the pet food industry: toxicological evidence and risk assessment

Mycotoxin contamination in pet food poses a serious health threat to pets, causing an emotional and economical concern to the pet owners. Aflatoxins, ochratoxins, trichothecenes, zearalenone, fumonisins and fusaric acid have been found in the ingredients and final products of pet food, resulting in both acute toxicity and chronic health problems in pets. Toxicological interaction among mycotoxins as a natural mixture further complicates the issue. The concepts of "risk assessment", using hazard identification, dose-response assessment, no observable adverse effect level (NOAEL), and lowest observed adverse effect level (LOAEL), should be applied to assess the risk and safety of mycotoxins in pet food, thereby instilling public confidence in the pet food industry.     

大型粮仓深层粮食扦样器设计与使用

针对传统扦样设备的弊端,研发了一款可移动、便携式粮食扦样器,并在广东省储备粮管理总公司东莞直属库进行了应用试验.结果表明,通过使用该扦样器,实现了大型粮食库仓深层粮食扦样的机械自动化,有效降低了仓储作业人员劳动强度,提高了扦样效率,达到了粮食仓储环节高装粮深度粮食样品取得到,取得轻松,取得精准的目标,为粮食储存期间质量...     

Pyrite oxidation by hexavalent chromium: investigation of the chemical processes by monitoring of aqueous metal species

Pyrite, an iron sulfide, occurs in many soils and sediments, making it an important natural reductant of toxic metal pollutants. This study investigated the processes leading to aqueous Cr(VI) reduction by pyrite in a closed thermostated (25 +/- 0.1 degrees C) system and under an argon atmosphere. Synthetic pyrite suspensions were reacted with a range of Cr(VI) solutions from 0 to 7 x 10(-4) M and at pH 2-8. Metal species concentrations were continuously monitored during a period lasting approximately 20 h. Preliminary experiments carried out in acidic media without Cr(VI) have shown that some pyrite dissolution occurred. Then, metal species concentration changes with time during pyrite oxidation by Cr(VI) solutions exhibited two distinct trends depending on the complete or incomplete Cr(VI) removal. As long as chromate existed in solution, the Cr-(Ill) to Fe(lIl) ratio was found to be an effective parameter to investigate the pyrite reaction stoichiometry with Cr(VI). Experimental values close to 2 suggest that sulfur compounds with oxidation states between 0 and 2 should be formed during pyrite oxidation by Cr(VI). If Cr(VI) was completely reduced from solution, then the pyrite oxidation by Fe(lll) ions took place to generate ferrous ions.