Emissions Of Carbonyl Compounds Research Articles

Carbonyl Compounds and Toxicity Assessments of Emissions from a Diesel Engine Running on Biodiesels

This study elucidates the effect of biodiesel on the emission of carbonyl compounds generated from a diesel engine (generator), and the related biotoxicity characteristics. The Microtox test and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay were conducted to evaluate the acute toxicity and cytotoxicity, respectively, of gaseous extracts from diesel engine exhaust. The engine was tested using diesel fuel and biodiesel blends (10, 30, 50, 75, and 100% of biodiesel by volume). The operating conditions of the diesel engine were set as idling, 10, 33, and 55% loads. The regulated emissions of carbon monoxide (CO), nitrogen oxides (NOx), and carbon dioxide (CO2) were monitored. The carbonyl compounds in the exhaust were collected in 2,4-dinitrophenylhydrazine (2,4-DNPH) solution in an impinger and converted to corresponding hydrazone derivatives, which were then analyzed using high performance liquid chromatography (HPLC) with an ultraviolet (UV) detector. Analysis results indicate that the carbonyl compound emissions increased when the engine was run on biodiesels at all of the loadings; however, the total concentration of emitted carbonyls did not increase with the biodiesel content. The dominant carbonyls (formalde-hyde, acetaldehyde, acrolein, and acetone) accounted for 70 to 90% of all carbonyl emissions in the engine exhaust. The concentrations of CO2 and NOx from B10 were quite similar to those from diesel. Finally, in the toxicity assessments, B10 had a higher acute toxicity and cytotoxicity than diesel, indicating that blending with biodiesel may have adverse health effects because of toxic gas emissions. At various engine loads, higher toxicities were associated with greater carbonyl emissions in diesel exhaust, but not in B10, indicating that the carbonyls may not be the major pollutants that induce the toxicity of emissions from biodiesel.

Carbonyl Emissions during Food Decay from Kimchi, Fish, and Salted Fish

In this study, the emissions of carbonyl compounds as offensive odorants were measured using three food types (Kimchi, fresh fish, and salted fish) as a function of time. Odor samples for each food type, collected at 0, 1, 3, 7, and 14 days, were analyzed by high performance liquid chromatography (HPLC). Only three kinds of carbonyl compounds were quantified above their respective detection limits: formaldehyde, acetaldehyde, and acetone. The emission patterns of these compounds were distinguishable from each other. Formaldehyde tends to peak at the beginning and decrease through time with unique patterns. Conversely, acetaldehyde and acetone seem to increase gradually through time. The results showed that relative patterns of carbonyl emissions were more distinguishable by compound type rather than food type.

Carbonyl compounds emitted by a diesel engine fuelled with diesel and biodiesel–diesel blends: Sampling optimization and emissions profile

Biodiesel is emerging as a renewable fuel, hence becoming a promising alternative to fossil fuels. Biodiesel can form blends with diesel in any ratio, and thus could replace partially, or even totally, diesel fuel in diesel engines what would bring a number of environmental, economical and social advantages. Although a number of studies are available on regulated substances, there is a gap of studies on unregulated substances, such as carbonyl compounds, emitted during the combustion of biodiesel, biodiesel–diesel and/or ethanol–biodiesel–diesel blends. CC is a class of hazardous pollutants known to be participating in photochemical smog formation. In this work a comparison was carried out between the two most widely used CC collection methods: C18 cartridges coated with an acid solution of 2,4-dinitrophenylhydrazine (2,4-DNPH) and impinger bottles filled in 2,4-DNPH solution. Sampling optimization was performed using a 2 2 factorial design tool. Samples were collected from the exhaust emissions of a diesel engine with biodiesel and operated by a steady-state dynamometer. In the central body of factorial design, the average of the sum of CC concentrations collected using impingers was 33.2 ppmV but it was only 6.5 ppmV for C18 cartridges. In addition, the relative standard deviation (RSD) was 4% for impingers and 37% for C18 cartridges. Clearly, the impinger system is able to collect CC more efficiently, with lower error than the C18 cartridge system. Furthermore, propionaldehyde was nearly not sampled by C18 system at all. For these reasons, the impinger system was chosen in our study. The optimized sampling conditions applied throughout this study were: two serially connected impingers each containing 10 mL of 2,4-DNPH solution at a flow rate of 0.2 L min −1 during 5 min. A profile study of the C1–C4 vapor-phase carbonyl compound emissions was obtained from exhaust of pure diesel (B0), pure biodiesel (B100) and biodiesel–diesel mixtures (B2, B5, B10, B20, B50, B75). The ΣCC of the emission concentrations were 20.5 ppmV for B0 and 15.7 ppmV for B100. When considering fuel blends, the measured ΣCC were 21.4 ppmV, 22.5 ppmV, 20.4 ppmV, 14.2 ppmV, 11.4 ppmV and 14.7 ppmV, respectively, for B2, B5, B10, B20, B50 and B75. Among the target CC, both formaldehyde and acetaldehyde were the major contributors to the observed total CC levels. Except for acrolein and formaldehyde, all CC showed a clear trend of reduction in the emissions from B2 to B100 (40% reduction, on average). Both individual and total CC emission factors (pg g −1 of fuel burnt) were calculated for all tested biodiesel–diesel blends. The lowest total CC emission factor (2271 pg g −1) was found when B50 was used; the individual emission factors determined (pg g −1) were: 539.7 (formaldehyde), 1411 (acetaldehyde), 30.83 (acrolein), and 310.7 (propionaldehyde).

Real-world emissions of carbonyl compounds from in-use heavy-duty diesel trucks and diesel Back-Up Generators (BUGs)

Emissions of carbonyl compounds such as formaldehyde, acetaldehyde, and acrolein are of interest to the scientific and regulatory communities due to their suspected or likely impacts on human health. The present work investigates emissions of carbonyl compounds from nine Class 8 heavy-duty diesel (HDD) tractors and also from nine diesel-powered backup generators (BUGs); the former were chosen because of their ubiquity as an emission source, and the latter because of their proximity to centers of human activity. The HDD tractors were operated on the ARB 4-Mode heavy heavy-duty diesel truck (HHDDT) driving cycle, while the BUGs were operated on the ISO 8178 Type D2 5-mode steady-state cycle and sampled using a mobile emissions laboratory (UCR MEL) equipped with a full-scale dilution tunnel. Samples were analyzed using the SAE930142 (Auto/Oil) method for 11 aldehydes, from formaldehyde to hexanaldehyde, and 2 ketones (acetone and methyl ethyl ketone). Although absolute carbonyl emissions varied widely by BUG, the relative contributions of the different carbonyls were similar (e.g., median: 56% for formaldehyde). A slight increasing trend with engine load was observed for relative formaldehyde contribution, but not for acetaldehyde contribution, for the BUGs. On-road per-mile carbonyl emission factors were a strong function of operating mode of the ARB HHDDT cycle, and found to decrease in the order Creep>Transient>Cruise. This order is qualitatively similar to emission factors for PAHs and n-alkanes determined for the same set of Class 8 diesel tractors in an earlier work. In general, relative carbonyl contributions for the HDD tractors were similar to those for BUGs (e.g., median: 54% for formaldehyde). These results indicate that while engine operating mode and application appear to exert a strong influence on the total absolute mass emission rate of the carbonyls measured, they do not appear to exert as strong an influence on the relative mass emission rates of individual carbonyls.

Characteristics of carbonyl compounds emission from a diesel-engine using biodiesel–ethanol–diesel as fuel

Characteristics of carbonyl compounds (carbonyls) emissions from biodiesel–ethanol–diesel (BE–diesel) were investigated in a Commins-4B diesel engine and compared with those from fossil diesel. Acetaldehyde was the most abundant carbonyls in the exhaust, followed by formaldehyde, acetone, propionaldehyde and benzaldehyde. Apliphatic carbonyls emitted from BE–diesel were higher than those from diesel fuel, while formaldehyde and aromatic carbonyls were less than those from diesel fuel. Total carbonyls emissions from BE–diesel were 1–12% higher than those from diesel fuel depending on engine operating conditions. The effects of engine speed and load level were also investigated carefully. It was found that total carbonyls emission was in positive correlation with the engine speed. During the constant speed/varying load tests, minimum total carbonyls emission was found at 50% load. Compared with fossil diesel, the BE-diesel was observed to significantly reduce PM emission and increase slightly NO x emission.

Emission of non-methane volatile organic compounds (VOCs) from boreal peatland microcosms—effects of ozone exposure

Abstract Non-methane volatile organic compounds (VOCs) emitted from boreal peatland microcosms were semiquantitatively determined using gas chromatography–mass spectrometry techniques in a growth chamber experiment. Furthermore, effects of vegetation composition and different ozone concentrations on these emissions were estimated by multivariate data analyses. The study concentrated on the less-studied VOCs, and isoprene was not analyzed. The analyses suggest that a sedge Eriophorum vaginatum is associated with emissions of the four most-emitted VOC groups (cyclic, aromatic, carbonyl and aliphatic hydrocarbon compounds) and also with VOCs emitted in smaller amounts (terpenoids and N-containing compounds). A woody dwarf shrub Andromeda polifolia was strongly associated with emissions of aromatic, carbonyl and terpenoid compounds. Results suggest that exposure to an ozone concentration of 150 ppb leads to an increased emission of most VOC groups. Emission of aromatic compounds seems to increase linearly with increasing ozone concentration. These observations indicate that peatlands may be a source of a vast range of volatile compounds to the atmosphere. For more accurate assessment of the impact of elevated tropospheric ozone on the terpenoid and non-terpenoid VOC emissions from peatlands, well-replicated open-air ozone-exposure experiments should be conducted.

Characteristics of emissions of air pollutants from burning of incense in a large environmental chamber

The objective of this study was to characterize the emissions of air pollutants from incense burning in a large environmental test chamber. Air pollutants emitted from ten types of commonly used incense manufactured in different regions were compared. The target pollutants included particulate matters (PM10, PM2.5), volatile organic compounds (VOCs), carbonyls, carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides (NOx), methane (CH4) and non-methane hydrocarbon (NMHC). The particulate matters emitted from all the incense significantly exceeded the Recommended Indoor Air Quality Objectives for Office Buildings and Public Places in Hong Kong (HKIAQO). The CO peak levels of seven incense types greatly exceeded the HKIAQO standard. The formaldehyde concentrations of six types of incense were higher than the HKIAQO. The highest formaldehyde level exceeded the standard by 2 times. The results indicated that the concentrations of benzene, toluene, methyl chloride and methylene chloride significantly increased with the burning of all incense tested. In addition, the benzene concentrations of all tested incense were significantly higher than the HKIAQO standard. Although Incense 2 and 6 were claimed to be environmental friendly, the quantity of the pollutants emitted was not observed to be lower than the others. It was observed that when comparing the gas pollutant emission factors between two major incense categories (i.e. traditional and aromatic), the traditional incense (i.e. Incense 1−6) had relatively higher values than aromatic incense (i.e. Incense 7−9). Generally, it was found that the VOCs emitted sequence was aromatic incense>tradition incense>church incense (i.e. Incense 10). However, the carbonyl compounds emission sequence was traditional incense>aromatic incense>church incense. The results show that incense burning is one of the important indoor air pollution sources for PM, CO and VOCs.

Artifact evidence in carbonyl compound sampling using the enclosure technique with cuvette system.

Biogenic hydrocarbon emission rates from individual plant species have been estimated experimentally placing small plants or branches in enclosures and measuring the emission rates of the compounds. All-Teflon chambers (cuvettes) where air samples are drawn through tubes packed with adsorbents, have been commonly used for plant enclosure. Sampling of carbonyl compounds emitted from plants has been done using 2,4-dinitrophenylhydrazine coated particles and the derivative carbonyl compounds have been analyzed by HPLC-UV. In this work, the enclosure technique using a cuvette for measurements of carbonyl compound emissions from plants was evaluated. Blank measurements in an empty cuvette have revealed quite different results for experiments performed under laboratory and field conditions. Rigorous univariate statistical analysis of the data obtained indicate that the analytical procedure to determine carbonyl compounds at trace levels in emission samples using the cuvette may lead to positive artifacts during field sampling. This analysis applied to laboratory measurements showed no difference in the results for the cuvette and external lines. Multivariate statistical calculations point out that solar light intensity accounts for the high carbonyl compound levels, especially for acetaldehyde, in the empty cuvette.

Emission of alcohols and carbonyl compounds from a spark ignition engine. Influence of fuel and air/fuel equivalence ratio.

A spark ignition engine was used to study the impact of fuel composition and of the air/fuel equivalence (lambda) ratio on exhaust emissions of alcohols and aldehydes/ketones. Fuel blends contained eight hydrocarbons (n-hexane, 1-hexene, cyclohexane, n-octane, isooctane, toluene, o-xylene, and ethylbenzene (ETB)) and four oxygenated compounds (methanol, ethanol, 2-propanol, and methyl tert butyl ether (MTBE)). Exhaust methanol is principally produced from fuel methanol and MTBE but also from ethanol, 2-propanol, isooctane, and hexane. Exhaust ethanol and 2-propanol are produced only from the respective fuel compounds. Exhaust formaldehyde is mainly produced from fuel methanol, acetaldehyde from fuel ethanol, and propionaldehyde from straight-chain hydrocarbons. Exhaust acroleine comes from fuel 1-hexene, acetone from 2-propanol, n-hexane, n-octane, isooctane, and MTBE. Exhaust crotonaldehyde comes from fuel 1-hexene, cyclohexane, n-hexane, and n-octane, methacroleine from fuel isooctane, and benzaldehyde from fuel aromatics. Light pollutants (C1-C2) are most likely formed from intermediate species which are quite independent of the fuel composition. An increase in A increases the exhaust concentration of acroleine, crotonaldehyde, methacroleine, and decreases these of the three alcohols for the alcohol-blended fuels. The concentration of methanol, formaldehyde, propionaldehyde, and benzaldehyde is a maximum atstoichiometry. The exhaust concentration of acetaldehyde and acetone presents a complex behavior: it increases in some cases, decreases in others, or presents a maximum at stoichiometry. The concentration of four aldehydes (formaldehyde, acetaldehyde, propionaldehyde, and benzaldehyde) is also linked with the exhaust temperature and fuel H/C ratio.

00/02491 Emissions of carbonyl compounds from various cookstoves in China

00/02491 Emissions of carbonyl compounds from various cookstoves in China

Effect of methanol-containing additive on the emission of carbonyl compounds from a heavy-duty diesel engine

This study was aimed at determining the effect of methanol-containing additive (MCA) on the emission of carbonyl compounds (CBCs) generated from the diesel engine. For this experiment, a heavy-duty diesel engine was connected with a full flow critical flow ventri (CFV) type dilution tunnel, a Schenck GS-350 DC dynamometer, and a DC-IV control system in series. The operating conditions of the heavy-duty diesel engine for both cold-start and hot-start Transient Cycle tests and for both low-load and high-load steady-state tests were ascertained. The exhaust of CBCs collected from a 2,4-dinitrophenylhydrazine (2,4-DNPH)-coated cartridge were first converted to corresponding hydrazone derivatives, which were then solvent-eluted and analyzed by a High Performance Liquid Chromatograph (HPLC) with an ultraviolet–visible (UV) detector. When either 10% or 15% MCA was used, the emission factors of the CBCs acrolein and isovaleraldehyde increased by at least 91%. Accordingly, future studies must be done to cut down the emission of CBCs when MCA and methanol alternative fuels are used.

Emission of isoprene and carbonyl compounds from a boreal forest and wetland in Sweden

Emission measurements of light hydrocarbons, light carbonyl compounds, and monoterpenes have been made with canister, DNPH, and Tenax samples, respectively, on Norway spruce (Picea abies), Scots pine (Pinus sylvestris), the floor of a mixed pine and spruce forest, and a Sphagnum fen at the NOPEX site (Northern hemisphere climate Processes and land-surface Experiment) in the southern boreal zone of Sweden, in 1995. The branch and ground measurements were made with the flow-through enclosure technique and static chamber technique, respectively. Norway spruce was found to emit significant amounts of isoprene, the normalised emission rate (30°C, 1000μmolm−2s−1) averaging 24±18nmolgdw−1h−1 (1.4μgCgdw−1h−1), and of carbonyls with normalised rates ranging from 10 to 150nmolgdw−1h−1 (0.3–4.6μgCgdw−1h−1). Acetone/acrolein and acetaldehyde dominated the carbonyl flux with 61 and 27%, respectively. The normalised monoterpene emission rate (30°C) varied from 17 to 60nmolgdw−1h−1 (2–7μgCgdw−1h−1), with α-pinene accounting for 34% of the flux. The emission from Scots pine included only traces of isoprene, while the emission rate of acetone/acrolein was comparable to that of the monoterpenes. The BVOC flux from the forest floor made up only a few percent of the total forest flux and included ethene and propane at several tens of nmolm−2h−1, and the monoterpenes at rates reaching 380nmolm−2h−1 (50μgCm−2h−1), dominated by α-pinene. A Sphagnum fen emitted isoprene at rates fully comparable to the areal flux of isoprene from the boreal spruce forest. Highest emission rates were observed from the low and wet micro-sites, as compared to the higher and drier hummocks. The average flux in June was 912±750nmolm−2h−1 (55±45μgCm−2h−1) and in August 6800±4000nmolm−2h−1 (408±240μgCm−2h−1). Monoterpene fluxes were 160±80nmolm−2h−1 (19±9μgCm−2h−1) in June and 760±480nmolm−2h−1 (90±60μgCm−2h−1) in August. Isoprene from Norway spruce and Sphagnum wetlands, as well as acetone/acrolein from Norway spruce and Scots pine, are shown here to be important components of the boreal emission of BVOC. More diurnal and seasonal data is needed to correctly evaluate the seasonal flux.

Emissions of Carbonyl Compounds from Various Cookstoves in China

This paper presents a new database of carbonyl emission factors for commonly used cookstoves in China. The emission factors, reported both on a fuel-mass basis (mg/kg) and on a defined cooking-task basis (mg/task), were determined using a carbon balance approach for 22 types of fuel/stove combinations. These include various stoves (e.g., traditional, improved, brick, and metal, with and without flue) using different species of crop residues and wood, kerosene, and several types of coals and gases. The results show that all the tested cookstoves produced formaldehyde and acetaldehyde and that the vast majority of the biomass stoves produced additional carbonyl compounds such as acetone, acrolein, propionaldehyde, crotonaldehyde, 2-butanone, isobutyraldehyde, butyraldehyde, isovaleraldehyde, valeraldehyde, hexaldehyde, benzaldehyde, o-tolualdehyde, m,p-tolualdehyde, and 2,4-dimethylbenzaldehyde. Carbonyls other than formaldehyde and acetaldehyde, however, were rarely generated by burning coal, coal gas, and...

Nonmethane Hydrocarbon, Monocarboxylic Acid, and Low Molecular Weight Aldehyde and Ketone Emissions from Vegetation in Central New Mexico

Direct emissions of nonmethane hydrocarbons, monocarboxylic acids, and low molecular weight carbonyl compounds were measured from vegetation typical to central New Mexico. These species included quaking aspen, cottonwood, Gambel oak, Douglas fir, Engelmann spruce, Rocky Mountain juniper, pinyon pine, and ponderosa pine. The hydrocarbon emissions from most of the coniferous trees were dominated by α-pinene. In general, α-pinene emissions were 100-10 000 ng g -1 h -1 and displayed the expected temperature dependence. Other identified hydrocarbons included isoprene, camphene, β-pinene, myrcene, Δ 3 -carene, and d-limonene. The deciduous trees as well as the spruce and fir trees showed isoprene emission rates of 100-100 000 ng g -1 h -1 . Formaldehyde and acetaldehyde were the most common low molecular weight carbonyl compounds measured. The carbonyl emissions averaged 50-1660 ng g -1 h -1 , depending on the compound and the trees species. Unlike the hydrocarbons, the carbonyl emissions displayed little correlation with enclosure temperature. Formic acid emissions averaged 15-920 ng g -1 h -1 , and acetic acid emissions averaged 50-1300 ng g -1 h -1 . As with the carbonyls, poor correlation was found between the acid emissions and the enclosure temperature. The deciduous trees were found to have average (mass-based) emissions of 98% hydrocarbons, 1% carbonyls, and 1% organic acids. The coniferous trees averaged 80%, 8%, and 12%, respectively.

Monitoring of low density lipoprotein oxidation by low-level chemiluminescence

A method for monitoring low-density lipoprotein (LDL) oxidation by low-level chemiluminescence (LL-CL) is described in this study. The kinetic indices obtained with this procedure, in particular lag-time and K value (related to prooxidant activity of Cu2+ bound to LDL) are compared with those of the established UV-absorbing conjugated diene assay. The correlation of lag-time values obtained by LL-CL and conjugated diene assay was very high both in the case of Cu2+- and peroxyl-radical-mediated oxidation (r = 0.99). By using the transient free radical scavenging activity of butylated hydroxytoluene, a calibration of LL-CL for lipid peroxyl radical and termination rate was obtained. The spectral analysis of LL-CL from oxidizing LDL shows a maximum peak between 420 and 500 nm, corresponding to the emission of triplet carbonyl compounds. LL-CL allows continuous and direct monitoring of LDL oxidation as extraction and derivatization of lipid peroxidation products are not required. Moreover, some limitations of UV spectroscopy such as by absorbing compounds need not be considered. Therefore, the present procedure represents a simple and convenient tool for continuous monitoring of LDL oxidation which may be applied to mechanistic and clinical studies.

Emissions of Carbonyl Compounds from Vehicles Fuelled with Different Gasolines

Carbonyl compounds (formaldehyde, acetaldehyde, acrolein, benzaldehyde and acetone) were sampled using Sep-Pak DNPH-Silica cartridges placed inside the exhaust pipes of several cars using various f...

Emissions of Carbonyl Compounds from Vehicles Fuelled with Different Gasolines

Emissions of Carbonyl Compounds from Vehicles Fuelled with Different Gasolines

The Emission of Carbonyl Compounds during Thermal Processing of an Acrylic Polymer

Optimal conditions of heating for an acrylic varnish have been determined by a study with a Setaram apparatus (simultaneous TG-DTA). While the dry var nish underwent thermal decomposition, the carbonyl compounds emitted were adsorbed on silica cartridges and separated by high-performance liquid chromatography. The thermal decomposition up to 650 ° C and up to 350 ° C showed that formaldehyde and acetaldehyde were the predominant toxic car bonyl compounds. Acrolein was found only when the varnish was heated up to 650°C; it was not emitted when heating was limited to 350°C. These experi mental results are compared with analyses performed in the industrial sector.

Carbonyl Compounds and PAH Emissions From CNG Heavy-Duty Engine

Previous works carried out in Istituto Motori laboratories have shown that natural gas is a suitable fuel for general means of transportation. This is because of its favorable effects on engine performance and pollutant emissions. The natural gas fueled engine provided the same performance as the diesel engine, met R49 emission standards, and showed very low smoke levels. On the other hand, it is well known that internal combustion engines emit some components that are harmful for human health, such as carbonyl compounds and polycyclic aromatic hydrocarbons (PAH). This paper shows the results of carbonyl compounds and PAH emissions analysis for a heavy-duty Otto cycle engine fueled with natural gas. The engine was tested using the R49 cycle that is used to measure the regulated emissions. The test analysis has been compared with an analysis of a diesel engine, tested under the same conditions. Total PAH emissions from the CNG engine were about three orders of magnitude lower than from the diesel engine. Formaldehyde emission from the CNG engine was about ten times as much as from the diesel engine, while emissions of other carbonyl compounds were comparable.

The Effect of Precipitation on Radial Increment in Norway Spruce (Picea abies Karst.) and on the Dynamics of a Lepidopteran Pest Insect

This paper reviewed the researches on the carbonyl compounds emission and uptake by plants, and discussed the compensation point of the bidirectional exchange of carbonyl compounds between plants and atmosphere. The uptake by leaf stomata and stratum corneum is the principal way for the purification of air aldehydes by plants. After entering into plant leaves, most parts of carbonyl compounds can be metabolized into organic acid, glucide, amino acid, and carbon dioxide, etc. , by the endoenzymes in leaves. The exchange direction of the carbonyl compounds between plants and atmosphere can be preliminarily predicted by the compensation point and the concentrations of ambient carbonyl compounds. This paper summarized the analytical methods such as DNPH/HPLC/UV and PFPH/GC/MS used for the determination of carbonyl compounds emitted from plants or in plant leaves. The main research interests in the future were pointed out, e. g. , to improve and optimize the analytical methods for the determination of carbonyl compounds emitted from plants and the researches on systems (e. g. , plant-soil system), to enlarge the detection species of carbonyl compounds emitted from plants, to screen the plant species which can effectively metabolize the pollutants, and to popularize the phytoremediation techniques for atmospheric