Ambient Contamination Research Articles

Proving Whether or Not Contamination is Caused by Oil and Gas Operations

Oil and gas development is becoming increasingly controversial in the U.S., in part because of uncertainty about the causes of groundwater contamination in active gas fields. Debates about whether contamination is caused specifically by hydraulic fracturing and whether gas wells should be regulated under the Safe Drinking Water Act rage, but without the relatively rare smoking gun, the question whether oil and gas development has caused contamination evades both scientific and legal determinations. The inability to determine causation is a problem that fuels public distrust of government and industry and deserves a serious effort to solve.In 2010, 2,682 wells were drilled in Pennsylvania, about 500 more than in Colorado’s Garfield County. Home to the Piceance Basin, Garfield County’s natural gas boom commenced in about 2004. That year, the Colorado Oil and Gas Conservation Commission (COGCC) permitted 796 wells in Garfield County -- a number that climbed steadily to 2,888 by 2008, the peak year to date. Whereas oil and gas development was previously concentrated offshore and in more confined parts of the Gulf Coast and Rocky Mountains, it is now occurring in more heavily populated areas such as Pennsylvania. Although the industry sparked controversy in its traditional territory, the volume of the public opposition has increased as development has invaded more populous regions and much of this controversy is fueled by concerns about water quality.During a 2009 public hearing on the New York Department of Environmental Conservation’s Supplemental Generic Environmental Impact Statement on oil and gas development, protesters in New York City held anti-development signs, interrupted official presentations and were escorted out of the venue. The New York legislature imposed a moratorium in November 2010 in order to allow the Department of Environmental Conservation to better study modern oil and gas development techniques, and federal legislators from New York, Pennsylvania and Colorado have called for federal regulation of the hydraulic fracturing (fracking) process under the auspices of the Safe Drinking Water Act (SDWA). Some of the reasons that oil and gas development is so controversial are that it is an industrial activity that is allowed under common law to encroach upon residential areas where it causes nuisance noise, odor and pollution. But it is also implicated in instances of ambient groundwater contamination that have not been fully resolved. This lack of resolution serves as a rallying cry for anti-development groups, and results partly from failures to adequately address issues of causation and proof. Public pressure, in turn, has spawned legislative proposals such as the so-called FRAC Act.

Electronic structure of indium tin oxide/nanocrystalline TiO2 interfaces as used in dye-sensitized solar cell devices

Dye-sensitized solar cells are typically prepared under ambient conditions and contamination is inevitably introduced during the fabrication process. Hence, the electronic structure and charge injection properties of the indium tin oxide (ITO)/nanocrystalline titanium dioxide (TiO2) interface was studied by photoemission spectroscopy (PES) in the presence of environmental contaminants. The interface was formed by in situ multi-step electrospray thin film deposition of TiO2 nanoparticles onto ITO substrates cleaned prior in solvent under ambient conditions. In between deposition steps, the samples were characterized with PES yielding the band line-up at the ITO/TiO2 interface. In addition, the band line-up before and after annealing of the TiO2 layer was determined. The results of these measurements have in common that there are only small charge injection barriers between the valence bands of the oxides (∼0–0.2 eV), but more significant barriers for electron injection from TiO2 to ITO (∼0.3–0.5 eV), which has the potential to affect the performance of solar cell device structures. Another focus of the experiments was to investigate whether an earlier reported work function lowering measurement artifact occurring during ultraviolet photoemission spectroscopy (UPS) measurements on environmentally contaminated metal oxide surfaces would affect the characterization of ITO/TiO2 interfaces. For this purpose additional band line-up measurements using low intensity x-ray photoemission spectroscopy (LIXPS) were performed. LIXPS has been demonstrated to not cause the artifact, i.e., can be used to detect its occurrence. The results of these experiments show that the UV-induced work function reduction is not observed on the annealed interface, but that at contaminated interfaces care must be taken during data evaluation to take the artifact into account.

Experimental results of UV laser cleaning on a silver Carlino coin

Silver artefacts and particularly ancient silver artefacts present the serious problem of turning black due to ambient contamination. The black colour is the consequence of a layer forming on the surface made of acanthite and jalpaite; both compounds are sulphur composts. Recently, a UV laser cleaning technique has demonstrated to be very promising in the processing of cultural artefacts. To operate on artefacts without contaminating the bulk, we first determined the laser fluence threshold of the bulk; second, we controlled the surface compounds, and finally we operated the laser irradiation. In this work, we utilised certified silver and silver/copper samples in order to perform preliminary studies. The threshold fluences we found were 780 and 510 mJ/cm2 for the pure Ag and for the Ag/Cu alloy, respectively. The jalpaite concentration on the Ag/Cu sample increased after a laser dose of 25 J/cm2, whereas for a higher laser dose its value lowered, pointing out that complex processes take part during the laser application. We successfully applied the technique on a Carlino coin made of silver coined in 1689 under King Carlo II. The analyses were performed by two different techniques that are able to find the percentage of elements and the chemical compounds: the energy dispersive X-ray fluorescence and the X-ray diffractometer spectrometer. We found that the sulphur concentration decreased upon the increase of the laser dose. Operating on the coin up to a dose of 280 J/cm2, the sulphur concentration deceased by up to 20%, while the coin looks clearer just after 50 J/cm2.

Hydrogel-Encapsulated Soil: A Tool to Measure Contaminant Attenuation In Situ

Hydrogel encapsulation presents a novel and powerful general method to observe many water-solid contaminant interactions in situ for a variety of aqueous media including groundwater, with a variety of nondestructive analytical methods, and with a variety of solids including contaminated soil. After intervals of groundwater immersion, polyacrylamide hydrogel-encapsulated solid specimens were retrieved, assayed nondestructively for uranium and other elements using X-ray fluorescence spectroscopy, and replaced in groundwater for continued reaction. Desorption dynamics of uranium from contaminated soils and other solids, when moved to uncontaminated groundwater, were fit to a general two-component kinetic retention model with slow-release and fast-release fractions for the total uranium. In a group of Oak Ridge soils with varying ambient uranium contamination (169-1360 mg/kg), the uranium fraction retained under long-term in situ kinetic behavior was strongly correlated (r(2) = 0.89) with residual uranium after laboratory sequential extraction of water-soluble and cation-exchangeable fractions of the soils. To illustrate how potential remedial techniques can be compared to natural attenuation, thermal stabilization of one soil increased the size of its long-term in situ retained fraction from 50% to 88% of the total uranium and increased the half-life of that long-term retained fraction from 990 to 40000 days.

The Increase of the Jet Size of an Atmospheric-Pressure Plasma Jet by Ambient Air Control

We present an approach to increase the area for surface treatment using a nitrogen atmospheric-pressure plasma jet sustained by a pulsed dc power source. This plasma is used for glass surface treatment to quantify the efficiency of the treatment by examination of the water contact angle before and after the treatment. The proposed approach utilizes a glass tube to shield the jet downstream from the ambient air contamination. With this approach, the visible jet length and width increase significantly. The effective area for surface treatment using this jet increases by more than a factor of two.

Practical considerations for validity of constant temperature anemometer flow measurements in industrial applications

The constant temperature anemometer (CTA) is used for measurement of flow characteristics in turbulent flow regions. Factors such as ambient conditions and contamination of the CTA sensor strongly affect the working of CTA, and its nonlinear calibration curve to a lesser extent. In order to minimize the consequences of these factors, the CTA must be recalibrated from time to time. For research applications, the recalibration can be done prior to each measurement. However, frequent recalibration is time consuming and expensive, and may be impractical in medical and industrial applications. In this paper, the use of CTA as flowmeter has been considered in the latter applications. To keep the need for elaborate recalibration of the CTA used as flowmeter to minimum, practical guidelines for ascertaining the validity of flow measurements have been presented. Application of correction factors for improvement of measurement accuracy has been discussed. Effect of change in the CTA voltage offset on the measurements has been considered. Results show that although correction factors can be used to improve the accuracy of measurements by the CTA used as flowmeter, in some cases, application of a correction factor alone cannot improve measurements, and thus recalibration of the CTA becomes necessary. Also, the use of correction factor alone does not allow for extension of measurements by the CTA used as flowmeter beyond its calibration range.

Recoverable electroluminescence from a contaminated organic/organic interface in an organic light-emitting diode

An organic/organic interface, like an electrode/organic interface in an organic light-emitting diode (OLED), can be severely affected by ambient contamination. However, we surprisingly found that the contaminated surface or interface can be “cured” by depositing a thin interfacial layer containing a strong reducing agent onto the contaminated surface before finishing the fabrication of the device. For example, in comparison with a regular OLED, an OLED having a 5-min ambient exposure to the light-emitting layer/electron-transporting layer interface drops its initial electroluminescence (EL) intensity by 50%. The decreased EL intensity due to the 5-min ambient exposure can be fully recovered and the improved operational stability can be realized after curing the contaminated interface using a thin Li interfacial layer. The experimental results provide a useful method to cope with the interfacial contamination in OLEDs during a manufacturing process. In addition, our results support the failure mechanism of an Alq-based OLED suggested by [Papadimitrakopoulos et al., Chem. Mater. 8, 1363 (1996)].

A Study on PVD Co Pre-clean Chamber RF Reflect Power Improvement

For 0.18um and 0.13 um technology, Co/TiN deposition process is widely used to form CoSix to provide the needed lower contact resistance of the polysilicon gate. CoSix formation is sensitive to pre-existing wafer surface native oxides and ambient contamination. Pre-clean process before Co film deposition is required to remove residues before Co/TiN deposition. The corresponding chamber RF reflected power too high issue during this pre-clean has significant impact on the etch rate and particle performance. In this paper, three approaches to reduce Co pre-clean chamber RF reflect power are presented.

Electronic structure of the indium tin oxide/nanocrystalline anatase (TiO2)/ruthenium-dye interfaces in dye-sensitized solar cells

The electronic structure of two interfaces commonly found in dye-sensitized photovoltaic cells based on nanocrystalline anatase TiO2 (“Grätzel cells”) was investigated using photoemission spectroscopy (PES). X-ray photoemission spectroscopy (XPS) and ultraviolet photoemission spectroscopy (UPS) measurements were carried out on the indium tin oxide (ITO)/TiO2 and the TiO2/cis-bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato)-ruthenium(II)bis-tetrabutylammonium dye (“N719” or “Ruthenium 535-bisTBA”) interfaces. Both contacts were investigated using a multistep deposition procedure where the entire structure was prepared in vacuum using electrospray deposition. In between deposition steps the surface was characterized with XPS and UPS resulting in a series of spectra, allowing the determination of the orbital and band lineup at the interfaces. The results of these efforts confirm previous PES measurements on TiO2/dye contacts prepared under ambient conditions, suggesting that ambient contamination might not have significant influence on the electronic structure at the dye/TiO2 interface. The results also demonstrate that there may be a significant barrier for electron injection at the sputtered ITO/TiO2 interface and that this interface should be viewed as a semiconductor heterojunction rather than as metal-semiconductor (Schottky) contact.

Identifying the source of a strong fullerene envelope arising from laser desorption mass spectrometric analysis of meteoritic insoluble organic matter

Insoluble organic matter (IOM) has been obtained from two carbonaceous chondrite meteorites and subjected to analysis by laser desorption mass spectrometry (LDMS) using standard operating conditions that were optimized for fullerene detection (3–6 μJ pulses at 337 nm focused to a spot size of approximately 100 μm in diameter). The preparation process yields no free C 60 in the IOM, and other experiments suggest that this material does not contain appreciable amounts of fullerenes. Nevertheless, a pronounced high-mass envelope is observed in LDMS, extending from 720 amu to about 4000 amu, with peaks spaced apart every 24 amu (corresponding to the gain or loss of C 2 units). We attribute this high-mass envelope to the existence of various fullerene molecules. The present work demonstrates that these fullerene molecules are created by the laser desorption laser ionization process under typical laser conditions used for studying free fullerenes in organic solvent extracts of natural samples (toluene and 1,2,4-trichlorobenzene). The implications of this false positive detection of fullerene molecules on the reports of fullerenes in other meteoritic samples have been investigated by introducing IOM into typical fullerene extraction procedures and examining the LDMS results. We found that IOM is capable of producing false positive signals in these experiments. The effect of ambient laboratory contamination producing fullerene signals is also described. It is found that extensive centrifugation of the meteoritic extracts is able to reduce the observed fullerene envelope, which points to an association of this envelope with IOM particulates that have passed through the filtering steps. We suggest the exercise of extreme caution in interpreting fullerene data from LDMS experiments.

The tropical brown alga Lobophora variegata as a bioindicator of mining contamination in the New Caledonia lagoon: A field transplantation study

Previous field and laboratory studies have identified the alga Lobophora variegata as a good candidate for biomonitoring metal contamination in the New Caledonia lagoon which is subjected to intensive and extensive metal inputs from land-based mining activities. The aim of this work was to further assess the bioindicative potential of this species by investigating, in the field, its bioaccumulation capacity for local key contaminants, i.e. Ag, As, Cd, Co, Cr, Cu, Mn, Ni and Zn. Algae from clean and contaminated sites were cross-transplanted for a period of three months in order to determine the in situ uptake and depuration kinetics of the nine elements. Results indicate that algae transplanted to the contaminated site displayed a significant linear increase in concentration with time for Ag, As, Cd, Co, Cr, Cu, Mn and Ni. In contrast, algae transplanted to the clean site did not show major depuration of these elements, except for Co. Overall, L. variegata showed a rapid temporal response in metal uptake, especially for the elements intensively released into the coastal environment of New Caledonia (viz., Co, Cr, Mn and Ni). This species appears therefore as an excellent bioindicator species of metal contamination in this area. Our results also provide background information necessary for using L. variegata under in situ experimental conditions so as to provide better quantitative information on ambient metal contamination levels. The wide distribution of L. variegata in tropical areas further enhances its potential as a bioindicator species of metal contamination in other tropical coastal environments.

Asymmetric Chiral Growth of Micron-SizeNaClO3Crystals in Water Aerosols

We describe an aerosol-liquid cycle that launches the autocatalytic amplification of any initial imbalance of the order of 10(-7)% (1 ppb) up to total chiral purity in a single step process. Crystal nucleation of NaClO3 is initiated at the aerosol air-water interface where, due to the accumulation of ambient chiral impurities or added hydrophobic chiral aminoacids in tiny concentrations (ppb), the initial levorotatory (l) and dextrorotatory (d) excess will not be produced with equal probability. The enantiomeric yield is then enhanced up to homochirality by recycling the crystallites through a liquid phase. In the absence of added catalysts this process leads to preferential (d) homochiral crystallizations in a ratio of 4:1 which is due to ambient contamination. By adding only 2 ppb of (L) or (D) Phe, we induce a final preferential homochiral crystallization of (d) or (l) handedness, respectively, in a ratio of 2:1.

Ambient contamination of poly-crystalline diamond surfaces studied by high-resolution electron energy loss spectroscopy and X-ray photoelectron spectroscopy

In this work we provide direct evidence of hydrogen, carbon and oxygen contamination of poly-crystalline diamond surfaces from ambient conditions and their thermal stability upon vacuum annealing. Deuterated diamond films were exposed to ambient conditions for ~ 3 months and then studied by high-resolution electron energy loss spectroscopy and X-ray photoelectron spectroscopy. Hydrocarbon contaminations posses at least two different binding states which desorb upon annealing to ~ 300 °C and ~ 600 °C. Oxygen contaminations gradually desorb upon annealing to 700–800 °C. It is shown that thermal desorption of contaminations creates sp 2 carbon atoms on the diamond film surface.

인천지역 일부 학교의 실내 및 대기 중 포름알데히드 농도 평가

This study evaluated formaldehyde concentration in classrooms and on roofs at 4 elementary schools, 3 middle schools and 3 high schools in Incheon City. These schools were chosen based on their surrounding environments that included industrial site, landfill, railway, 8-lane road and harbor. Indoor concentration ranged between 4.65 and <TEX>$56.25{\mu}g/m^3$</TEX>, while that of outdoor concentration was <TEX>$1.23{\sim}10.22{\mu}g/m^3$</TEX>, both of which were below <TEX>$100{\mu}g/m^3$</TEX>, a formaldehyde criterion stipulated by the School Health Act. Indoor concentration was higher than outdoor concentration by <TEX>$1.4{\sim}5.9$</TEX> times, and there was a positive correlation between indoor and outdoor formaldehyde concentrations (R=0.49). As for indoor concentration, multi-use practice rooms had an average 2.8 times higher than that of usual classrooms with a statistically significant difference (p<0.01). Indoor formaldehyde concentration had a positive correlation with the construction year (R=0.55). The school close to the industrial complex had the highest ambient formaldehyde concentration, followed by the one near a landfill. The formaldehyde concentration in school in the vicinity of the industrial complex was twice or more than that of the school located other site. In conclusion, this study suggests that it is crucial to consider surrounding environments in selecting school sites, as it can influence ambient air contamination, as well as using construction material that emit less formaldehyde, in order to protect the health of students, teachers and school staff.

Towards a Nano-Scale Electrochemical and Spectroscopic Characterization of Organic Layers on Oxide Surfaces

The presented works prepares the ground for galvanic deposition of metallic overlayers on metal oxide surfaces functionalized by phosphonic acid monolayers. In view of this goal, it is necessary to control the most important factors of the electrodeposition process (e.g. flatness and uniformity of distribution). Because of these requirements, in this work, we study the morphology and the interaction between PO(OH)2-functionalities and an oxide surface. The analysis is carried out using complementary surface analysis techniques, like Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS). We have succeeded in creating a blank surface with a RMS roughness of less than 1 nm and a hydroxyl fraction of 17%. The organic deposition was followed in time and it was observed that Volmer Weber multilayer growth was present. Also the influence of carbon contamination was characterized and a methodology is presented to correct the experimental data for this ambient contamination.

The effect of ambient contamination on PEMFC performance

The effect of environmental contamination (NO x , SO 2) on the performance of proton exchange membrane fuel cells (PEMFC) was studied. The performance of PEMFCs was tested for 100 h with different cathode reactants. According to the Ambient Air Quality Standard of PRC, three kinds of cathode gases were applied to operate the fuel cells, which were 1 ppm NO 2/air, 1 ppm SO 2/air and a mixture of contaminant gases. The gas mixture contained 0.8 ppm NO 2, 0.2 ppm NO and 1 ppm SO 2. Finally, the poisoning behavior and the mechanisms were analyzed by constant-current discharging and cycle voltammetry (CV). During the 100 h test, the potentials of the fuel cell degraded by 65%, 77% and 90% with 1 ppm SO 2/air, a gas mixture and 1 ppm NO 2/air, respectively.

A comparison of two techniques for studying sediment desorption kinetics of hydrophobic pollutants

A comparison of two techniques (gaseous purge and vial desorption) for studying the kinetics of desorption of hydrophobic pollutants from natural sediments was conducted using identical, pre-equilibrated pollutant-sediment suspensions. Desorption profiles for the two techniques [for Lindane, Aldrin, 2,2′-dichlorobiphenyl (2,2′-DCB), 4,4′-dichlorobiphenyl (4,4′-DCB), and 2,2′,6,6′-tetrachlorobiphenyl (TCB)] were then compared, based on the distribution of pollutant mass between the labile (fast) and non-labile (slow) desorption phases and the release rate constants for each phase of release. The vial desorption technique shows many practical advantages over the gaseous purge technique, including its more realistic mixing conditions, the use of an independent sample for each data point (as opposed to a calculation of a cumulative mass purged at each time point), the fact that the vials constitute a closed system and are therefore less subject to ambient contamination, and the relatively low demands of time and money for the vial technique. No consistent trends in labile rate constants or in pollutant distribution between the labile and non-labile phase were observed between the two techniques. A comparison of kinetic parameters shows much faster non-labile rate constants for the gaseous purge technique, attributed to the violent, continuous agitation employed, which likely disrupted sediment aggregates and oxidized the natural organic matter associated with the sediment. Non-labile rate constants have implications for the long-term fate of compounds adsorbed to repetitively disturbed sediments. This study suggests that the traditionally less popular vial desorption technique may yield more realistic non-labile desorption rate constants.

Postsilicon Oxide Etch Cleaning Process Using Integrated Ashing and an HF Vapor Process

A totally integrated dry cleaning process after silicon oxide etching in fluorocarbon gases was proposed and demonstrated on blanket silicon oxide film and patterned wafers. Silicon oxide etching was performed using an inductively coupled plasma etcher using 100% gas. In situ oxygen plasma and HF vapor were used for cleaning fluorocarbon polymeric contamination formed during oxide etching. This process sequence was performed in a vacuum cluster system in our laboratory. With the apparatus, we have the ability to transfer samples between processing chambers and perform surface analysis at a base pressure in the range. In this manner, we can mimic a clustered process, avoid ambient contamination, and obtain an accurate picture of the evolution of the wafer surface throughout the process sequence. We support our cleaning results with quasi-in situ angle-resolved X-ray photoelectron spectroscopy. It was demonstrated that planar surfaces after silicon oxide etching could be cleaned, leaving less than one monolayer of oxygen, fluorine, and carbon on the surface. The proposed cleaning process was also successful in removing contamination from both sidewalls and trench bottom in line- and space-patterned samples. The measured contact resistance values after the cleaning process were close to the theoretical minimum.

Industrial vacuum leak detection with intelligent gas leak detectors: Not just a mass spectrometer

In recent years, the requirements for reliability and lifetime of industrial components have increased significantly. This is due both to customer requirements and the Total Quality philosophy that has been much more widely introduced. This development has had an impact especially on industrial leak detection, since this is one of the non-destructive testing techniques that has been at a rather low level both regarding the involved technologies and the training of personnel. Modern leak detectors that use test gases, especially helium, for testing components and systems have addressed these needs. In a most important first step, as early as 20 years ago, helium leak detectors did away with liquid nitrogen traps by introducing counter flow technology. This, together with the replacement of manual valves by electromagnetic ones controlled by a microprocessor, enabled operation by relatively unskilled persons in industrial processes. In the years that followed, efforts concentrated on lowering the detection limit and the helium signal response time of the new method. The introduction of dry pumping systems (required by the semiconductor industry) was an additional challenge to be mastered parallel to those efforts. With the latest instruments, and this is the major concern of this article, operation under industrial conditions was optimized, now also focusing on background signal handling, which is mandatory for a quick pump-down of large vessels (up to 100 liters of volume) and unambiguous detection of leaks under contamination conditions. Reaching the leak rate range below 1 × 10-9mbarl/s within a few minutes when pumping a 100 liter vessel is one of the specifications to be achieved. Several 1000?ppm of ambient helium background or contamination of elastomer gaskets may not produce long waiting times with no value added. It is not surprising that alongside new pumping technologies software is an increasingly important part of modern leak detectors. There are ways of dealing with signal instabilities to increase the detection limit for leak rates, it is possible to reduce the effect of water vapor desorption on the pump-down time for large volume vessels without LN2, there are more and more sophisticated ways of “ZERO” functions and non-linearity compensations for high total pressure operation. These developments are explained and demonstrated with some examples of modern leak detectors recently introduced into the market.

Observation of Field‐Effect Transistor Behavior at Self‐Organized Interfaces

Ultrathin, conformal semiconductor– dielectric bilayers can be fabricated in one step by self-organization (see Figure), without exposing the critical interface to ambient contamination. Low-voltage polymer field-effect transistors using a fluorene–triarylamine copolymer as the p-channel semiconductor and 40–60 nm thick crosslinked bisbenzocyclobutene derivative as the gate dielectric are shown to be robust and reproducible.