Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Light Pollution”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11Linked to original sources
PubMed1980

Practical application of magnetic alignment of mineral fibres for hazard evaluation.

Techniques and instrumentation have been developed employing the magnetic alignment of fibrous dust collected on membrane filters coupled with light-scatter measurement for the accurate and reproducible assessment of airborne fibre hazard. This equipment, specifically designed to measure asbestos hazard, is built into a standard microscope, which also incorporates a facility for manual fibre counting and for bulk sample identification. With this new technique, up to 100 samples per day can be analysed automatically, compared with some 10-15 samples per day by manual counting. Collected fibres are assessed from areas of membrane filters some 30 times greater than those with manual methods; consequently, a more representative result ensues. These techniques lend themselves to considerable and varied application and involve relatively inexpensive instrumentation.

Air Pollutants, Occupational↗
PubMedDate not supplied

[Isolation of hydrocarbon-oxidizing psychrophilic bacteria from oil-polluted soils].

Microorganisms growing on a mineral medium with crude oil and its light fractions as only carbon and energy sources have been isolated from samples of oil-polluted soils collected in the Usa District (Komi Republic, Russia). For the first time, hydrocarbon-oxidizing psychrophilic bacteria of the genus Cytophaga have been found that are clearly capable of consuming crude oil hydrocarbons. A method for cultivating microorganisms on porous plastic is proposed. The data from the literature on the response of soil microbiota to oil pollution indicate that the pollution can activate or suppress the growth of various physiological groups of microorganisms [1]. Different soil and climatic conditions and pollution levels can give rise to different microbial cenoses, which include different associations and predominant microbial species.

Biodegradation, Environmental↗
PubMed2005

Trends in speciated fine particulate matter and visibility across monitoring networks in the Southeastern United States.

Trends in fine particulate matter <2.5 microm in diameter (PM2.5) and visibility in the Southeastern United States were evaluated for sites in the Interagency Monitoring of Protected Visual Environments, Speciated Trends Network, and Southeastern Aerosol Research and Characterization Study networks. These analyses are part of the technical assessment by Visibility Improvement-State and Tribal Association of the Southeast (VISTAS), the regional planning organization for the southeastern states, in support of State Implementation Plans for the regional haze rule. At all of the VISTAS IMPROVE sites, ammonium sulfate and organic carbon (OC) are the largest and second largest contributors, respectively, to light extinction on both the 20% haziest and 20% clearest days. Ammonium nitrate, elemental carbon (EC), soils, and coarse particles make comparatively small contributions to PM2.5 mass and light extinction on most days at the Class I areas. At Southern Appalachian sites, the 20% haziest days occur primarily in the late spring to fall, whereas at coastal sites, the 20% haziest days can occur through out the year. Levels of ammonium sulfate in Class I areas are similar to those in nearby urban areas and are generally higher at the interior sites than the coastal sites. Concentrations of OC, ammonium nitrate, and, sometimes, EC, tend to be higher in the urban areas than in nearby Class I areas, although differences in measurement methods complicate comparisons between networks. Results support regional controls of sulfur dioxide for both regional haze and PM2.5 implementation and suggest that controls of local sources of OC, EC, or nitrogen oxides might also be considered for urban areas that are not attaining the annual National Ambient Air Quality Standard for PM2.5.

Air Pollution↗
PubMed2003

Remote monitoring of air pollutant emissions from point sources by a mobile lidar/sodar system.

This paper describes remote monitoring of air pollutant emissions by a mobile lidar (light detection and ranging)/ sodar (sound detection and ranging) system. First, measurements are carried out in the flue gas plume of a public power plant. The investigations focus mainly on quantifying SO2 emissions, but the uncertainties of such measurements are also emphasized. Furthermore, an example providing valuable data sets for the development and validation of plume dispersion models is outlined with measurements of the dilution of SO2 along the plume axis. Series of repeated determinations of SO2 emissions show a large variation in the obtained flux values, with moderate margins of error. Incomplete recording of the plume within the individual lidar scans, induced by strong looping movements of the flue gas plume, predominantly causes the variations of flux values. Therefore, the highest flux values determined are considered to be the most exact. This is verified by a comparison of measured fluxes with in situ measurements made by the plant operators. The results further indicate that lidar measurements illustrate the location and dimension of aerosol plumes better than the location and dimension of the plumes of gaseous compounds. The wind direction affecting the plume at any moment can be determined faster by lidar than by sodar because the latter requires much longer time intervals of signal averaging. Measurements show higher concentrations of SO2 compared with results from a Gaussian plume model for periods of less than 5 min after dispersion. The findings emphasize the suitability of remote sensing for detecting emissions and for investigating the propagation and dilution of air pollutant plumes.

Air Pollutants, Occupational↗
PubMed1995

Flow cytometric assay of lung macrophage uptake of environmental particulates.

We sought to establish a quantitative method using flow cytometry to study uptake of environmental particulates by alveolar macrophages (AMs). We used right angle light scatter (RAS) to measure uptake of titanium dioxide, quartz, and diesel particulates. After incubation with TiO2 in vitro, AMs showed dose-dependent increases in both cell-associated particles visualized by microscopy and RAS measured by flow cytometry (e.g., fold increase RAS at 4, 8, 16, 32, and 80 micrograms/ml, respectively, = 2 +/- 0.1, 4.0 +/- 0.5, 5.5 +/- 0.5, 9.1 +/- 2.5, 14.3 +/- 0.9; mean +/- SEM). Similar results were obtained with quartz and diesel particles. A strong correlation was observed between particle load per cell and AM RAS after uptake of fluorescent latex beads or fluorescent TiO2 (coated with BODIPY-BSA) (R2 = 0.984, 0.997, respectively). Using this technique, we found AM uptake of environmental particulates to be substantially greater than that of a panel of myelomonocytic and epithelial cell lines, consistent with their physiologic role in pulmonary defenses. RAS measurements have also identified both calcium-dependent and calcium-independent components in AM interactions with inert particles. Although this technique does not allow precise quantitation of particle number or mass per cell, flow cytometric analysis of relative increases in RAS is a useful tool to study AM interactions with a variety of environmental particulates.

Animals↗
PubMed1998

Microbial photodegradation of aminoarenes. Metabolism of 2-amino-4-nitrophenol by Rhodobacter capsulatus.

The phototrophic bacterium Rhodobacter capsulatus photoreduces 2,4-dinitrophenol to 2-amino-4-nitrophenol, which is further metabolized by an aerobic pathway that is also light-dependent. The catabolism of 2-amino-4-nitrophenol requires O2 and the presence of alternative carbon (C) and nitrogen (N) sources, preferably acetate and ammonium. Rhodobacter capsulatus B10, a bacterium unable to assimilate nitrate, releases negligible amounts of nitrite when growing with 2-amino-4-nitrophenol, thus suggesting that an oxygenase, nitrite-producing activity is not involved in the metabolization of the compound. The diazotrophic growth of R. capsulatus increases in the presence of 2-amino-4-nitrophenol, but growth with ammonium is clearly inhibited by the compound. Mutant strains of R. capsulatus B10, which are affected in nifHDK, nifR1, or nifR4 genes, unable to fix dinitrogen, do not grow with 2-amino-4-nitrophenol as the sole N source. This indicates that the compound cannot be used as a N source. The nif mutants degrade 2-amino-4-nitrophenol to the same extent as the wild-type in the presence of ammonium. The compound is not used as a C source by the bacterium, either. Aromatic stable intermediates, such as 2,4-diaminophenol or 4-nitrocatechol, are not detectable in microaerobic cultures of R. capsulatus growing with 2,4-dinitrophenol or 2-amino-4-nitrophenol.

Aerobiosis↗
PubMed2005

Reconciliation and interpretation of the Big Bend National Park light extinction source apportionment: results from the Big Bend Regional Aerosol and Visibility Observational Study--part II.

The recently completed Big Bend Regional Aerosol and Visibility Observational (BRAVO) Study focused on particulate sulfate source attribution for a 4-month period from July through October 1999. A companion paper in this issue by Schichtel et al. describes the methods evaluation and results reconciliation of the BRAVO Study sulfate attribution approaches. This paper summarizes the BRAVO Study extinction budget assessment and interprets the attribution results in the context of annual and multiyear causes of haze by drawing on long-term aerosol monitoring data and regional transport climatology, as well as results from other investigations. Particulate sulfates, organic carbon, and coarse mass are responsible for most of the haze at Big Bend National Park, whereas fine particles composed of light-absorbing carbon, fine soils, and nitrates are relatively minor contributors. Spring and late summer through fall are the two periods of high-haze levels at Big Bend. Particulate sulfate and carbonaceous compounds contribute in a similar magnitude to the spring haze period, whereas sulfates are the primary cause of haze during the late summer and fall period. Atmospheric transport patterns to Big Bend vary throughout the year, resulting in a seasonal cycle of different upwind source regions contributing to its haze levels. Important sources and source regions for haze at Big Bend include biomass smoke from Mexico and Central America in the spring and African dust during the summer. Sources of sulfur dioxide (SO2) emissions in Mexico, Texas, and in the Eastern United States all contribute to Big Bend haze in varying amounts over different times of the year, with a higher contribution from Mexican sources in the spring and early summer, and a higher contribution from U.S. sources during late summer and fall. Some multiple-day haze episodes result from the influence of several source regions, whereas others are primarily because of emissions from a single source region.

Air↗
PubMed2003

Emission spectroscopy for coal-fired cyclone furnace diagnostics.

Using a spectrograph and charge-coupled device (CCD) camera, ultraviolet and visible light emission spectra were obtained from a coal-burning electric utility's cyclone furnaces operating at either fuel-rich or fuel-lean conditions. The aim of this effort is to identify light emission signals that can be related to a cyclone furnace's operating condition in order to adjust its air/fuel ratio to minimize pollutant production. Emission spectra at the burner and outlet ends of cyclone furnaces were obtained. Spectra from all cyclone burners show emission lines for the trace elements Li, Na, K, and Rb, as well as the molecular species OH and CaOH. The Ca emission line is detected at the burner end of both the fuel-rich and fuel-lean cyclone furnaces but is not detected at the outlet ends of either furnace type. Along with the disappearance of Ca is a concomitant increase in the CaOH signal at the outlet end of both types of furnaces. The OH signal strength is in general stronger when viewing at the burner end rather than the exhaust end of both the fuel-rich and fuel-lean cyclone furnaces, probably due to high, non-equilibrium amounts of OH present inside the furnace. Only one molecular species was detected that could be used as a measure of air/fuel ratio: MgOH. It was detected at the burner end of fuel-rich cyclone furnaces but not detected in fuel-lean cyclone furnaces. More direct markers of air/fuel ratio, such as CO and O2 emission, were not detected, probably due to the generally weak nature of molecular emission relative to ambient blackbody emission present in the cyclone furnaces, even at ultraviolet wavelengths.

Air Pollution↗
PubMed2000

Dual action of the active oxygen species during plant stress responses.

Adaptation to environmental changes is crucial for plant growth and survival. However, the molecular and biochemical mechanisms of adaptation are still poorly understood and the signaling pathways involved remain elusive. Active oxygen species (AOS) have been proposed as a central component of plant adaptation to both biotic and abiotic stresses. Under such conditions, AOS may play two very different roles: exacerbating damage or signaling the activation of defense responses. Such a dual function was first described in pathogenesis but has also recently been demonstrated during several abiotic stress responses. To allow for these different roles, cellular levels of AOS must be tightly controlled. The numerous AOS sources and a complex system of oxidant scavengers provide the flexibility necessary for these functions. This review discusses the dual action of AOS during plant stress responses.

Air Pollutants↗
PubMed2004

Mechanochemical removal of organo-chlorinated compounds by inorganic components of soil.

The purpose of this work is to evaluate the catalytic efficiency of two metal oxides, ferrihydrite and birnessite and of a ferruginous smectite, towards organic molecules such as 4-chloroaniline (4-CA), pentachlorophenol (PCP), and five polychlorinated biphenyls (PCBs) characterised by different number and position of chlorine atoms. Mechanochemical dry contacts with light grinding between catalytic surfaces and pollutants have been carried out. The efficiency of the mechanochemical removal was compared with batch experiments for the soluble compounds (PCP and 4-CA). The removal of 4-CA and PCP by the mechanochemical procedure resulted more effective than by batch contact in the presence of birnessite and ferrihydrite, particularly at higher pH (100% removal of 4-CA by birnessite in 30 min at pH 8.6 after the mechanochemical contact compared to 20% removal using the batch interaction at the same pH). The mechanochemical contact of PCBs and birnessite produced a removal of pollutant that was a function of the number of chlorine atoms (complete removal of 2,2'-dichlorobiphenyl in 10 days and a removal of 30% and 20% of 2',3,4-trichlorobiphenyl and 3,3',4,4'-tetrachlorobiphenyl, respectively in 90 days) and of the position of chlorine atoms about the biphenyl rings (100% of 2,2'-dichlorobiphenyl in 10 days, 84% of 3,3'-dichlorobiphenyl in 15 days and 40% of 4,4'-dichlorobiphenyl in 27 days).

Aniline Compounds↗
PubMed2001

Degradation of 2,4-dichlorophenol by immobilized iron catalysts.

The degradation of 2,4-Dichlorophenol (from now on 2,4-DCP) has been carried out on Nafion-Fe (1.78%) in the presence of H2O2 under visible light irradiation. A solution containing 2,4-DCP (TOC 72 mg C/L)) is seen to be mineralized in approximately 1 h in the presence of H2O2 (10 mM) under solar simulated visible light (80 mW cm-2) at pH values between 2.8 and 11. Homogeneous photo-assisted Fenton reactions were capable of mediating 2,4-DCP degradation only up to pH 5.4. The degradation kinetics of 2,4-DCP on Nafion-Fe membranes was more favorable than the one observed during Fenton photo-assisted processes at pH 2.8. The degradation of 2,4-DCP was investigated as a function of the substrate, oxidant concentration and applied light intensity. The Nafion-Fe was seen to be effective over many cycles during the photo-catalytic degradation of 2,4-DCP showing an efficient and stable performance during 2,4-DCP degradation without leaching out Fe(3+)-ions into the solution. Evidence is presented that the degradation at the surface of the Nafion-Fe membrane seems to be controlled by mass transfer and not by chemical reaction of the species in solution. The approach used to degrade 2,4-DCP is shown to be valid for other chloro-carbons like 4-chlorophenol, 2,3-chlorophenol and 2,4,5-trichlorophenol.

Catalysis↗
PubMed2003

Photodegradation of 17alpha-ethynylestradiol in aqueous solution exposed to a high-pressure mercury lamp (250 W).

The photodegradation of 17alpha-ethynylestradiol (EE(2)) induced by high-pressure mercury lamp (lambda> or =313, 250 W) in aqueous solution of EE(2) was investigated initially. The affecting factors on the photodegradation were studied and described in details, such as EE(2) initial concentration, Fe(3+), algae, exposure time, and so on. The concentration of EE(2) in distilled water was mainly determined using fluorescence spectrophotometer. The photodegradation of EE(2) in aqueous solution exposed to high-pressure mercury lamp was evident and could be accelerated by Fe(3+) or algae (e.g. Anabaena cylindrica) in general. With the algae concentration increasing, photodegradation rate increased. In this paper, the mechanism of photocatalytic degradation of EE(2) by Fe(3+) or algae is discussed primarily.

Anabaena↗
PubMed2006

Photolysis behavior of herbicide propisochlor in water media and preliminary analysis of photoproducts under different light sources.

Photolysis behavior of a new herbicide propisochlor in water media as well as the effects of light sources, initial concentration of propisochlor, pH value, dissolved oxygen (DO) level, and salinity on the photolysis process was investigated. It was found that the relationship between initial concentration of propisochlor and its photodegradation rate was negatively correlated. The changes in acidity and alkalinity of the reaction medium influenced the photoreaction rate evidently. In the alkaline solution the degradation was accelerated. In the reaction media with different pH values, the photolysis followed the first-order kinetics. The presence of dissolved oxygen may promote the photolysis and there existed an optimum of dissolved oxygen concentrations. Increasing the DO level can weaken the promotion and even have an adverse effect. It was demonstrated that with dissolved oxygen the photodegradation of propisochlor followed the first-order kinetics equation. The addition of salt ions Ca2+ and Mg2+ changed the ionic strength and solvent polarity, resulting in the effect on propisochlor photolysis. The photoproducts were detected by both HPLC and GC-MS methods. It was found that photolysis products varied under different light sources. Conclusions may be reached that in the photodegradation of propisochlor, the benzene ring remained intact under irradiation of both solar light and high-pressure mercury lamp, and the amido link was relatively stable, while dechlorination was liable to take place; moreover, alpha-hydrogen at the substituent of benzene ring was active.

Acetamides↗
PubMed1992

Photoactivation of 2-nitrofluorene in vitro and in the rat in vivo. UVA-induced formation of reactive intermediates that bind covalently to RNA and protein.

2-Nitrofluorene (2-NF), an environmental pollutant, can be activated by UV light to reactive intermediates that bind covalently to RNA and protein in vitro: high levels of covalent binding were obtained. This covalent binding was not dependent on the presence of oxygen in the solution and could be decreased by glutathione. Hydrolysis of the in vitro modified RNA and subsequent analysis of the liberated bases by HPLC revealed that approximately 15% of the covalent binding of 2-NF to RNA could be attributed to the formation of a guanosine adduct of nitroreduced 2-NF, N-(deoxyguanosin-8-yl)-2-aminofluorene. Many other adducts are formed of which the structure and mechanism of formation are as yet unknown. The possibility of photoactivation of 2-NF in the rat in vivo was also investigated. Photoactivation increased covalent binding of 2-NF in the skin but not in other organs. The mechanism of the photoactivation of 2-NF is discussed.

Animals↗