| Carbonyl compounds are a kind of volatile organic compounds, which have stronger chemical reaction activities. They are the important intermediates of photochemical oxidation. Their photochemical oxidations are the main source of hydroxyl free radical. They also affect the formation of ozone and peroxyacetyl nitrates (PANs) in troposphere. Carbonyl compounds also are the most common organic pollutants in the atmosphere. Some carbonyls are carcinogenic, such as formaldehyde, acetaldehyde, and acrolein. They have received more and more attention due to their potential adverse human health effects and their important roles in the atmospheric chemistry.A ternary-mobile phase program with acetonitrile (ACN), water and tetrahydrofuran was developed to simultaneously identify and quantify 22 carbonyl compounds species by high performance liquid chromatography-UV detection (HPLC-UV). The analytical method succeeded in separating acrolein from acetone. The same method was used to study the concentrations of carbonyl compounds in the atmosphere and plant samples.Carbonyl compounds concentrations were measured in five periods from January 2007 to October 2007 (covering winter, high-air-pollution days, spring, summer and autumn) based on collected samples from one sampling point in Shanghai. Formaldehyde, acetaldehyde and acetone were the most abundant carbonyls with their mean concentrations of 19.40±12.00, 15.92±12.07 and 11.86±7.04μg m-3 respectively, in the daytime for five sampling periods. Formaldehyde and acetaldehyde showed similar diurnal profiles with peak mixing ratios in the morning and early afternoon during the daytime. Their mean concentrations were highest in summer and lowest in winter. Acetone showed reversed seasonal variation. The important characteristics of carbonyl compounds in Shanghai were that the higher carbonyls levels were in nighttime than in daytime. The high molecular weight (HMW, C5-C10) carbonyls also showed obvious diurnal variations with higher concentrations in the daytime in summer and autumn, while they were all not detected in winter. Hexaldehyde and nonanaldehyde were the most abundant species of HWM. The carbonyls levels in high-air-pollution days were reported. More carbonyl species with higher concentrations were found in high-air-pollution days than in spring. These carbonyls were transported with other pollutants from north and northwest in March 27 to April 2, 2007 and then mixed with local sources. Based on studying the carbonyl levels in different districts of Shanghai city, the results showed that there were not big differences of carbonyl compounds levels between industrial district and business district. A conclusion could be drawn that the effects on ambient carbonyl compounds levels from different functional districts of cities is not very important.A new procedure combining derivatisation with ultrasonication was developed for the fast extraction of carbonyl compounds in plant leaves. Fresh leaves (<0.01 gram) were minced and ultrasonicated in acidic 2,4-dinitrophenylhydrazine (DNPH)- ACN solution for 30 min first and then holding 30 min to allow aldehydes and ketones in leaves to react completely with DNPH. The total extraction process was performed under room temperature and only took 60 min. The advantages of this method are very little sample preparation, requiring short treatment time and usual equipment. Four landscape plants, i.e. camphor tree (Cinnamomum camphora), sweet olive (Osmanthus fragrans), cedar (Cedrus deodara), and dawn redwood (Metasequoia glyptostroboides), were selected and extracted by this method. The common carbonyl species of the four trees were formaldehyde, acrolein and m/o-tolualdehyde. They all accounted for 67.26% in cedar, 50.84% in sweet olive, 45.83% in dawn redwood and 44.65% in camphor tree, respectively. Camphor tree had the highest leaf level of m/o-tolualdehdye with 14.98±3.41μg g-1(fresh leaf weight), which indicated that camphor tree may be considered to be a bioindicator of the level of tolualdehyde or xylene in the atmosphere.In carbonyl compounds emission inventories of four landscape plants, i.e. camphor tree, sweet olive, cedar, and lotus magnolia (Magnolia grandiflora), formaldehyde, acetaldehyde, acetone, 2-butanone, butyraldehyde, valeraldedyde and hexaldehyde were the common carbonyl species, but crotonaldehyde, m/o-tolualdehyde, 2, 5-dimethylbenzaldehyde and decylaldehyde were not found. Formaldehyde, acetaldehyde and acetone had higher emission rates than other carbonyls. They all altogether accounted for 54.58% in lotus magnolia, 58.63% in sweet olive, 74.56% in cedar, and 50.31% in camphor tree, respectively, in summer. The emissions of formaldehyde, acetaldehyde and acetone all showed obvious diurnal and seasonal variations, but the variations were influenced by plant species. The carbonyl species, diurnal and seasonal variations of carbonyls emission rates were all controlled by plant developmental stage.There are significant correlations between atmospheric carbonyl compounds concentrations and their emission rates from plant leaves, which indicated that carbonyls levels in the atmosphere have an impact on their emission rates from plant leaves to some degree, which also implied that the atmospheric carbonyls levels can influence on the bi-directional exchange of carbonyl compounds between the atmosphere and plant leaves. However, no correlations were found between leaf carbonyl levels and leaf emission rates with atmospheric carbonyl levels. |
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