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PubMed2006

Sorption and degradation of imidacloprid in soil and water.

Imidacloprid, the major component of many widely used insecticide formulations, is highly persistent in soils. In this study, the sorption of imidacloprid by six soils as well as its photodegradation and hydrolysis in water were studied. The soils differed significantly in organic matter content and other physical and chemical properties. Sorption increased with increasing soil organic matter content but was not significantly correlated with other soil properties. Removal of organic matter via H2O2 oxidation decreased the sorption. By normalizing the Freundlich coefficients (Kf) to organic matter contents, the variability in obtained sorption coefficient (Kom) was substantially reduced. These results indicate that soil organic matter was the primary sorptive medium for imidacloprid. The low heat of sorption calculated from Kom suggests that partition into soil organic matter was most likely the mechanism. The photodegradation and hydrolysis of imidacloprid in water followed pseudo-first-order kinetics; however, the latter process needed a six-time-higher activation energy. While both processes produced the same main intermediate, they occurred via different pathways. The hydrolysis of imidacloprid was not catalyzed by the high interlayer pH in the presence of metal-saturated clays, which appeared to result from the lack of the pesticide adsorption in the interlayers of clays.

Adsorption↗
PubMed2002

Visualization and measurement of multiphase flow in porous media using light transmission and synchrotron x-rays.

Non-aqueous phase liquids enter the vadose zone as a result of spills or leaking underground storage facilities, thus contaminating groundwater resources. Measuring the contaminant concentrations is important in assessing the risk to human health and the environment and to develop effective remediation. This research presents the development and application of the light transmission method (LTM) for three-phase flow systems, aimed at investigating unstable fingered flow in a soil-air-oil-water system. The LTM uses the hue and intensity of light transmitted through a slab chamber to measure fluid content, since total liquid content is a function of both hue and light intensity. Evaluation of the LTM is obtained by comparing experiments with LTM and synchrotron X-rays. The LTM captures the spatial resolution of the fluid contents and can provide new insights into rapidly changing, two-phase and three-phase flow systems. Application of the LTM as a visualization technique for environmental and physical phenomena is noted. Visualization by LTM of groundwater remediation by surfactants as well as visualization of model cluster growth and fractal dimensions was also explored.

Calibration↗
PubMed2005

The impacts of cyanobacteria on pulp-and-paper wastewater toxicity and biodegradation of wastewater contaminants.

This study investigated the effects of cyanobacteria from pulp-and-paper waste-treatment systems on biological toxicity removal and biodegradation of certain wastewater contaminants. In field and batch studies, using the Microtox assay, cyanobacterial biomass and final wastewater toxicity were significantly correlated. In softwood-based wastewater, a decrease in toxicity was negatively correlated with cyanobacterial biomass, but the correlation was positive in hardwood-based wastewater. In the softwood-based wastewater, toxicity remained higher in the light than it was in the dark, whereas in hardwood-based wastewater, toxicity was lower in the light than it was in the dark. All of these results were light-dependent, suggesting that the photosynthetic growth of cyanobacteria is required to induce significant effects. When grown in mixed cultures with bacterial degraders, cyanobacteria from pulp-and-paper waste-treatment systems generally impeded the biodegradation of the wastewater contaminants phenol and dichloroacetate (DCA). However, there was one case where the cyanobacterium Phormidium insigne improved the bacterial degradation of DCA. Doubling inorganic nutrient concentrations did not improve phenol or DCA biodegradation in the majority of cases, indicating that nutrient competition is not a major factor. These data suggest that cyanobacteria play an important role during the biological treatment of contaminants, and, hence, toxicity removal in pulp-and-paper waste-treatment systems.

Biodegradation, Environmental↗
PubMed2004

[Study on on-board measurements and modeling of vehicular emissions].

It's a basic work to study the characteristics of vehicular emissions and give emission factors for development of vehicular emission inventory and decision-making of the control strategies. On-board emission measurements of on-road vehicles are regarded as important complementary to emission laboratory dynamometer tests. On-board exhaust emission measurements were conducted on seven samples of gasoline cars in a typical road in Macao, using AVL DiGas 4000 light five-gas analyzer. It was found that there was an obvious reduction of gaseous pollutant emissions from cars equipped with electronic fuel injection and three-way catalytic converter system (referred to as EFI cars in the following), compared to old carburetor cars. The average volume concentrations of CO, HC and NO of carburetor cars were 227 x 10(-6), 1.57% and 1477 x 10(-6), respectively, while those of EFI cars were 33 x 10(-6), 0.21% and 131 x 10(-6), which were about 1/11 through 1/7 of the former. However, there were high emissions during the cold start of EFI cars. The arithmetical mean concentrations of CO and NO emissions of EFI cars were calculated and their absolute values were predominantly contributed by high concentrations with low frequency. Furthermore, the emission factors of gasoline cars were estimated by test data, and at the same time, MOBILES model was used to calculate average emission factors of gasoline cars in Macao in 2000. The ratios between the results calculated by model and estimated by experiment data were in the range of 59%-139%, which would narrow into 68%-132% if only annual average emission factors were compared. The results suggest that EFI + TWC systems equipped in vehicles have good effect on the emission reduction, but catalytic converters are not activated during the cold start. Technical improvement of EFI cars, which could reduce the occurrence of high emissions with low frequency during the operation, would decrease their average level on exhaust emissions a lot. Furthermore, it's reliable that the emission factors of gasoline cars in Macao calculated by modified MOBILES model.

Air Pollutants↗
PubMed2005

Benzene: a secondary pollutant formed in the three-way catalyst.

Benzene emissions from a relevant proportion of today's gasoline-driven passenger cars and light-duty vehicles can increase by up to 2 orders of magnitude when driving at high engine load (e.g., on highways). Under such conditions, post-catalyst benzene levels exceeded those found pre-catalyst. As a consequence, formation of benzene in the catalyst was postulated. To further reduce ambient air concentrations of benzene,these critical operating conditions must be carefully avoided. Here, we report in detail to what extent and at what operating conditions catalyst-induced benzene and toluene formation can occur. For that purpose, a EURO-1 passenger car (1.8 L, model year 1995)fulfilling the valid regulations, equipped with a new, two-layered, Pd-CeO2-Al2O3/Rh-ZrO2-Al2O3 three-way catalyst was operated at steady state on a chassis dynamometer at 100, 125, and 150 km/h at variable air to fuel ratios. Pre- and post-catalyst exhaust gas concentrations of benzene, toluene, C2-, and C3-benzenes were monitored at a time resolution of 0.5 Hz by means of chemical ionization mass spectrometry. A net benzene formation window, ranging from pre-catalyst exhaust gas temperatures of 600-730 degrees C and lambda-values of 0.83-0.95, with a pronounced minimum at 0.87, was observed. Dealkylation reactions of aromatic hydrocarbons are assumed to be the major pathway leading to benzene.

Air Pollutants↗
PubMed1978

Bioaccumulation and detection of trace levels of cadmium in aquatic systems by Eichhornia crassipes.

The water hyacinth (Eichhornia crassipes) may be used as a sensitive biological indicator for continuously monitoring trace quantities of toxic heavy metals in aquatic systems. A river water system polluted with cadmium was simulated while other factors of temperature, day-night cycle, water quality, and light intensity remained constant. When the water hyacinth is maintained in river water containing 0.001 mg/l. of cadmium chloride, the plant's root system will concentrate this element at an average rate of 0.9, 1.4, and 3.0 mug Cd/g root dry weight after 24, 48, and 72 hr exposure periods, respectively. At a higher cadmium concentration of 0.01 mg/l., cadmium was concentrated in the roots much faster to levels of 6.8, 13.6, and 39.1 mug/g root after 4, 8, and 24 hr exposure periods, respectively. At initial concentrations of 0.05 mg/l. cadmium, the roots contained 29.5, 48.8, and 156 mug/g root following 4, 8, and 24 hr exposure periods, respectively. During these same time intervals, the water hyacinth sorbed 56.7, 153, and 281 mug/g root when the initial cadmium concentration was increased to 0.10 mg/l. The water hyacinth tops can also assist in the monitoring process when cadmium contamination levels are 0.10 mg/l. and greater. At this initial cadmium concentration, cadmium is translocated into the tops. After 8 hr, the tops averaged 1.1 mug/g top. After 24 hr, this concentration was increased to 6.1 mug/g top.

Cadmium↗
PubMed1994

Removal of pesticides from wastewater at golf courses using plants (removal by mung beans; Phaseolus radiatus L).

Many studies have been done on the removal of pollutants from wastewater using aquatic plants. Water hyacinth has been the most widely-used plant, and systems using water hyacinth are well-established. These systems, however, have a few problems in their practical use. In a previous paper, we proposed a new system that could be used as a substitute for a conventional system or, as a secondary system to assist the conventional one. Mung beans will be used to remove pollutants in this system. In the previous experiment, the removal characteristics of nutrient salts such as NO2-, NO3-, NH4+ and phosphorus salts from wastewater in residential areas were examined. Mung beans exhibited good characteristics for removing these nutrient salts. At present, pesticides used at golf courses have become a severe environmental problem polluting water supplies. The purpose of this study was, therefore, to verify whether our new system using mung beans was also effective in removing pesticides from wastewater at golf courses. An experiment was conducted on seven different pesticides. They were three insecticides; Diazinon, Fenitrothion and Chlorpyrifos, three fungicides; Captan, Isoprothiolane and Chlorothalonil, and a herbicide; Simazine. The experimental results showed that, under experimental conditions, the pesticides were rapidly removed and that they exhibited no harmful effects on the growth of the mung beans. Mung beans may be used, therefore, to remove pesticides from wastewater at golf courses although further research is needed.

Fabaceae↗
PubMed2003

Indoor environment quality in dental clinics: potential concerns from particulate matter.

PURPOSE: To provide a comprehensive assessment of the indoor environment of a representative dental office. METHODS: Health and comfort parameters, including carbon dioxide (CO2), respirable particulate matter (PM2.5), volatile organic compounds (VOCs), temperature, relative humidity, light and sound level, were measured at three sites over a 1-week period. Both real-time and integrated sampling methods were used, and clinic activities were recorded. Measurements were compared to guidelines and standards, and interactions between pollutant levels, emissions, and clinic activities were investigated using correlations, trend analyses, and a ventilation assessment. RESULTS: Comfort parameters were found to be within recommended values, with the exception of relative humidity, which was low but not unusual for the winter season investigated. Ventilation rates were within accepted guidelines. Integrated sampling showed that concentrations of VOCs were well below guidelines. However, PM2.5 levels exceeded ambient standards (by a factor of 2 to 6) throughout the building. Continuous trending allowed identification of peak levels, but correlations of clinic activities with measured concentrations were inconclusive. The results suggested that levels of air contaminants in dental clinics (with the exception of PM) are within guideline levels. With the recirculating ventilation systems found in most clinics and offices, particulate contaminants may rapidly disperse throughout a building. Improved capture, exhaust and filtration would decrease indoor PM concentrations. If contaminants are pathologic, the ramifications for practitioners may be considerable, and some specialists may be particularly at risk.

Acrylates↗
PubMed2003

Volatile metabolites of higher plant crops as a photosynthesizing life support system component under temperature stress at different light intensities.

The effect of elevated temperatures of 35 and 45 degrees C (at the intensities of photosynthetically active radiation 322, 690 and 1104 micromoles m-2 s-1) on the photosynthesis, respiration, and qualitative and quantitative composition of the volatiles emitted by wheat (Triticum aestuvi L., cultivar 232) crops was investigated in growth chambers. Identification and quantification of more than 20 volatile compounds (terpenoids--alpha-pinene, delta 3 carene, limonene, benzene, alpha- and trans-caryophyllene, alpha- and gamma-terpinene, their derivatives, aromatic hydrocarbons, etc.) were conducted by gas chromatograph/mass spectrometry. Under light intensity of 1104 micromoles m-2 s-1 heat resistance of photosynthesis and respiration increased at 35 degrees C and decreased at 45 degrees C. The action of elevated temperatures brought about variations in the rate and direction of the synthesis of volatile metabolites. The emission of volatile compounds was the greatest under a reduced irradiation of 322 micromoles m-2 s-1 and the smallest under 1104 micromoles m-2 s-1 at 35 degrees C. During the repair period, the contents and proportions of volatile compounds were different from their initial values, too. The degree of disruption and the following recovery of the functional state depended on the light intensity during the exposure to elevated temperatures. The investigation of the atmosphere of the growth chamber without plants has revealed the substances that were definitely technogenic in origin: tetramethylurea, dimethylsulfide, dibutylsulfide, dibutylphthalate, and a number of components of furan and silane nature.

Air Pollution, Indoor↗
PubMed1992

A basic study on removal of nutrient salts in wastewater using plants (removal by mung beans; Phaseolus radiatus L).

Many studies have reported on the removal of pollutants from wastewater using aquatic plants. The water hyacinth has been the most widely used and its system is the most well established. This system however, has a few problems in practical use. The purpose of this study is to obtain basic information on a new system that can substitute for a conventional system or be used as a secondary system to assist the conventional one. We first envisioned a model of this new system and then conducted a preliminary experiment using a small experimental unit to simulate the new system. The experiment showed that mung beans were a suitable plant for our study. Their removal rate of pollutants was the highest before they developed leaves and started photosynthesis. We found that nutrients were expelled outside the plant root when nutrient concentration inside the plant tissue became too high.

Absorption↗
PubMed2000

Particle mass emission rates from current-technology, light-duty gasoline vehicles.

Now that the U.S. Environmental Protection Agency has promulgated new National Ambient Air Quality Standards for PM2.5, work will begin on generating the data required to determine the sources of ambient PM2.5 and the magnitude of their contributions to air pollution. This paper summarizes the results of an Environmental Research Consortium program, carried out under the auspices of the U.S. Council for Automotive Research. The program focused on particulate matter (PM) emissions from representative, current-technology, light-duty gasoline vehicles produced by DaimlerChrysler Corp., Ford Motor Co., and General Motors Corp. The vehicles, for the most part taken from the manufacturer's certification and durability fleets, were dynamometer-tested using the three-phase Federal Test Procedure in the companies' laboratories. The test fleet was made up of a mixture of both low-mileage (2K-35K miles) and high-mileage (60K-150K miles) cars, vans, sport utility vehicles, and light trucks. For each vehicle tested, PM emissions were accumulated over 4 cold-start tests, which were run on successive days. PM emission rates from the entire fleet (22 vehicles total) averaged less than 2 mg/mile. All 18 vehicles tested using California Phase 2 reformulated gasoline had PM emission rates less than 2 mg/mile at both low and high mileages.

Air Pollution↗