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At least 289 records · Page 16Linked to original sources
PubMed2006

Continuous flow configuration for total hydrocarbons index determination in soils by evaporative light scattering detection.

A continuous flow configuration is proposed for the estimation of the hydrocarbon index in soils using for the first time evaporative light scattering detection (ELSD). The method is based on a membrane-enrichment of the hydrocarbons of interest (C10-C40), which are previously extracted from the soil matrix with a water:hexane mixture using a household microwave oven. The organic supernatant is cleaned-up through silica, evaporated and redissolved in a sodium dodecyl sulphate aqueous solution which is introduced in the loop of an injection valve. The sample, carried by an aqueous stream, passes through a continuous filtration unit fitted with a 1 microm pore size PTFE membrane, where the hydrocarbons are retained while the potential coextracted compounds are wasted. Quantitative elution of the C10-C40 fraction is accomplished by passing an acetone stream through the filter which drives the analytes to the ELSD system for analytical measurement. The detection limit was 1.8 microg ml(-1), the linear range 5-25 microg ml(-1) and the precision 4.3%. The recoveries were between 93 and 97%. The proposed method was also evaluated by attenuated total reflexion-Fourier transform (ATR-FT-IR) analysis of the extracts.

Calibration↗
PubMed2004

Variability of catechin and 4-hydroxyacetophenone distribution in Norway spruce needles in relation to their position, age, and growing conditions.

The amount of catechin and 4-hydroxyacetophenone in the methanolic extract of the Norway spruce needles at the locality Bílý Kríz (Moravian-Silesian Beskydy Mts.) was found in the range 2.8-12.1 mg g(-1) (dry weight) and 0.2-17.7 mg g(-1) (dry weight), respectively. Total amount of catechin (sum of the last three needle year-classes) is statistically higher (p<0.01) in the sparse areas compared to the dense ones and similar trends were recorded for catechin content in current and one-year-old needles. These results may support an idea about primary control of phenolic production by the incident solar radiation, which depends on the social position of the tree and canopy closure degree.

Acetophenones↗
PubMed2005

Effects of oxygen on the release and distribution of phosphorus in the sediments under the light condition.

Effects of oxygen on the release and distribution of phosphorus (P) in the sediments in the presence of light were investigated, using sediment cores and overlying water from Lake Taihu, in China. The results show that P can be released from sediments to the overlying water in both anoxic and aerobic conditions. But more P was released in the anoxic condition. The transformation of P between various fractions in the sediments was observed during the release experiments. Concentrations of Ca-bound P and organic P in the sediments decreased in both conditions, but Fe/Al-bound P increased in the aerobic condition. The decrease of total P and P fractions in the sediments is consistent with the accumulative increase in quantity (AIQ) of total P (TP) in the overlying water, but is contrary with the AIQ of dissolved inorganic P. This is due to the uptake of algae by the dissolved inorganic P. Total nitrogen in the sediments in the anoxic condition was lower than that in the aerobic condition, and pH in the overlying water increased in the anoxic condition.

Aluminum↗
PubMed2000

High levels of melatonin in the seeds of edible plants: possible function in germ tissue protection.

The seeds of plants represent the anlage of the next generation and are vital to their existence. Melatonin has been identified in the leaves and flowers of plants but not in seeds. In this study, we examined the seeds of 15 edible plants for the presence of melatonin which was extracted using cold ethanol. Melatonin was initially identified by radioimmunoassay and subsequently quantified and confirmed using high performance liquid chromatography. The physiological concentrations of melatonin in the 15 seeds studied ranged from 2 to 200 ng/g dry weight. The highest concentrations of melatonin were observed in white and black mustard seeds. This level of melatonin is much higher than the known physiological concentrations in the blood of many vertebrates. Since the seed, particularly its germ tissue, is highly vulnerable to oxidative stress and damage, we surmise that melatonin, a free radical scavenger, might be present as an important component of its antioxidant defense system. Thus, melatonin in seeds may be essential in protecting germ and reproductive tissues of plants from oxidative damage due to ultraviolet light, drought, extremes in temperature, and environmental chemical pollutants.

Chromatography, High Pressure Liquid↗
PubMed2002

Study of chlorothalonil photodegradation in natural waters and in the presence of humic substances.

Photodegradation of chlorothalonil was studied in different natural waters (sea, river and lake) as well as in distilled water under natural and simulated solar irradiation. The effect of dissolved organic matter (DOM) such as humic and fulvic substances on the photodegradation rate of chlorothalonil was also studied in simulated sunlight. The presence of DOM enhanced the photodegradation of chlorothalonil with the exception of seawater. The kinetics were determined through gas chromatography electron capture detection (GC/ECD) and the photodegradation proceeds via pseudo-first-order reaction in all cases. Half-life ranged from 1 to 48 h. In natural and humic water chlorothalonil photodegradation gave rise to two different intermediates compared to distilled water demonstrating that the transformation of chlorothalonil depend on the constitution of the irradiated media and especially from DOM. The byproducts identified by GC/MS techniques were: chloro-1,3-dicyanobenzene, dichloro-1,3-dicyanobenzene, trichloro-1,3-dicyanobenzene and benzamide.

Fungicides, Industrial↗
PubMed2003

On-road measurement of automotive particle emissions by ultraviolet lidar and transmissometer: instrument.

A novel vehicle emissions remote sensing system (VERSS) for the on-road measurement of fuel-based particulate matter (PM) emission factors is described. This system utilizes two complementary PM channels using an ultraviolet Lidar and transmissometer for the measurement of PM mass column content behind a passing vehicle. Ratioing the PM mass column content with the carbon mass column content, simultaneously measured with infrared absorption, yields the fuel-based PM mass emission factor. The transmissometer directly yields PM extinction coefficients without calibration, while the Lidar measurement of PM backscatter coefficients is calibrated through laboratory measurements of gases with well-known backscatter coefficients. The PM mass column content is calculated from these extinction and backscatter coefficients with the help of mass backscatter and extinction efficiencies obtained from theoretical calculations. This novel VERSS has been used extensively in a major air quality study, and example data are presented.

Air Pollutants↗
PubMed2005

Joint sealants: an overlooked diffuse source of polychlorinated biphenyls in buildings.

In October 2000, joint sealants containing polychlorinated biphenyls (PCB) were discovered in various public buildings in Switzerland. Triggered by this event, a nationwide comprehensive study was initiated by the Swiss Agency for the Environment, Forests, and Landscape, and 1348 samples of joint sealants as well as 160 indoor air samples from concrete buildings erected between 1950 and 1980 were analyzed. Out of 1348 samples, 646 (48%) contained PCB. In 279 (21%) samples, PCB concentrations of 10 g/kg and more were detected, and concentrations of 100 g/kg of PCB or more were found in 129 (9.6%) samples. These data indicate that PCB were widely used as plasticizers in joint sealants in Switzerland. In buildings constructed between 1966 and 1971, one-third of all joint sealants investigated contained more than 10 g/kg of PCB. PCB concentrations exceeding the limit of 0.050 g/kg above which material is required to be treated as PCB bulk product waste were reached by 568 samples (42%). PCB with a chlorine content between 45 and 55%, corresponding to mixtures such as Clophen A50, Aroclor 1248, and Aroclor 1254, were encountered in 316 samples (70%). In 42 cases (26%) where joint sealants containing PCB were present, clearly elevated PCB indoor air concentrations above 1 microg/m3 were encountered. In eight cases (5%), levels were higher than 3 microg/m3. The Swiss tentative guideline value of 6 microg/m3 (based on a daily exposure of 8 h) for PCB in indoor air was exceeded in one case (0.6%). On the basis of this work, representing the first large-scale nationwide analysis of the issue of PCB-contaminated joint sealants, we estimate that there are still 50-150 t of PCB present in these materials, acting as diffuse sources. They are distributed over many hundreds of buildings all over the country and represent a significant but frequently overlooked inventory of PCB. In light of the Stockholm Convention on persistent organic pollutants that entered into force last year, reduction of the release of PCB from these widely used materials is an important issue to be addressed.

Air Pollutants, Occupational↗
PubMedDate not supplied

Photochemical formation of singlet molecular oxygen in illuminated aqueous solutions of several commercially available sunscreen active ingredients.

Evidence is presented for the photochemical formation of singlet molecular oxygen (1O2) in air-saturated aqueous solutions of several sunscreen active ingredients using sunlight-range illumination. This is of significance because (1) 1O2 is known to be cytotoxic, and (2) there have been several reports of toxic effects associated with the use of some sunscreens; most notably, with p-aminobenzoic acid (PABA). Illuminated aqueous solutions of PABA, 2-ethylhexyl p-(dimethylamino)benzate (ODPABA), 2-hydroxy-4-methoxybenzophenone (BZ3), 2,2'-dihydroxy-4-methoxybenzophenone (BZ8), 2-ethylhexyl 2-cyano-3,3-diphenylacrylate (OCR), 2-ethylhexyl p-methoxycinnamate (OMC), and 2-ethylhexyl salicylate (OCS) were evaluated individually for 1O2 formation. Furfuryl alcohol (FFA), a well-known chemical trap for 1O2, was added to each of the aqueous sunscreen solutions. The FFA was consumed when solutions of PABA, ODPABA, OMC, and OCR were illuminated, but no loss of FFA other than by direct photolysis occurred in solutions of BZ3, BZ8, or OCS. There was also no significant loss of FFA in any of these solutions kept in the dark. Further evidence for the formation of 1O2 in illuminated aqueous sunscreen solutions is provided by the results of experiments in which individual solutions containing sunscreen active ingredients and FFA that were diluted with D2O exhibited an increased rate of FFA consumption while the addition of azide ion (N3-) reduced the rate of FFA consumption. Continuous sunlight-range illumination of aqueous PABA solutions produced significantly higher steady-state concentrations of 1O2 than in solutions containing any of the other sunscreen active ingredients evaluated. The substituted benzophenone compounds (BZ3 and BZ8) and the salicylate-based compound (OCS) not only appear to produce no 1O2, but they also appear to produce no other reactive oxidant species that are capable of consuming FFA. This indicates that BZ3, BZ8, and OCS may be peferable, from the standpoint of toxic oxidant formation, for use as sunscreen active ingredients when compared to the other compounds evaluated in this study.

4-Aminobenzoic Acid↗
PubMed2002

The ecological condition of south Florida estuaries.

An assessment of the ecological condition of south Florida estuaries based on regional probabilistic monitoring was conducted during the summer of 1995. Samples and data were collected on water and sediment quality, benthos, and fish tissue contaminants. Elevated concentrations of metals and pesticides were measured in both sediments and fish tissue with some exceedances of guidance values. Bottom dissolved oxygen levels over 23-37% of the area were below state criteria. Eighty-eight percent of surface waters had greater than 10% penetration of ambient light to a depth of 1.0 m. Nine percent of the area studied in South Florida exhibited degraded biology and impaired use based on a calculated index of ecological condition. Using the probability-based monitoring design, useful information of this type can be provided to resource managers regarding estuarine condition on a regional scale.

Animals↗
PubMed1999

Light regime, riboflavin, and pH effects on 2,4-D photodegradation in water.

A laboratory study was conducted to determine the effects of light regime, riboflavin, and pH on photodegradation of 2,4-D in aqueous solution. In controlled-environment chamber experiments, riboflavin sensitized 2,4-D photolysis in a concentration-dependent manner under both attenuated UV (-UV) and enhanced UV (+UV) light regimes. The photolysis half-life of 2,4-D in solutions containing 10 mg L-1 riboflavin was 9.7 and 12.5 h when exposed to +UV and -UV, respectively, compared to no photolysis in the absence of riboflavin. In contrast, the extrapolated half-life of 2,4-D in solutions containing 2.5 mg L-1 riboflavin was 46 h under +UV and 72 h under -UV. The rate of 2,4-D photolysis in the presence of riboflavin increased under both light regimes as initial pH of the solution was decreased from 7.5 to 4.5. The half-life of 2,4-D in the presence of 10 mg L-1 riboflavin at pH 4.5 and exposed to +UV was 1.6 h. Lumichrome, a principal photoproduct of riboflavin, did not photosensitize 2,4-D. Concentrations of 2,4-dichlorophenol formed as a result of riboflavin-sensitized 2,4-D photolysis were higher under the -UV than the +UV regime. These results indicate that riboflavin concentration, solution pH, and light regime are interacting factors that may be manipulated to enhance rates of aqueous 2,4-D photolysis.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1995

The sensitive individual and the indoor environment: case study.

This case study describes an indoor environment investigation initiated in response to numerous health and comfort complaints suspected of being associated with a two-story office building. Conventional indoor environment investigation techniques were applied in an attempt to identify one or several contributing factors, such as inadequate outdoor air ventilation and the presence of a respiratory irritant. The air quality satisfaction percentage in the building was well above 80%; however, at least one individual was experiencing a fairly severe reaction only upon entering the subject building. Evaluating the building indoor conditions as acceptable without attempting to address all possible building-related causes and communicating findings to interested occupants would likely have resulted in more occupant complaints and increased the potential for hysteria conditions. This investigation necessarily addressed a sensitive individual and involved an occupational physician as a constructive participant in the investigation.

Air Pollutants↗