PAHs in road dust of Nanjing Chemical Industry Park, China: chemical composition, sources, and risk assessment.

The objectives of the present study were to research the chemical composition of PAHs in PM2.5 of road dust, explore potential sources of PAHs, and assess their carcinogenic risk. Fifty-six road dust samples were collected on the arterial and sub-arterial roads at Nanjing Chemical Industry Park during the sampling periods of autumn and winter. A resuspension system in the laboratory was used to simulate the naturally suspended road dust in the environment and collect PM2.5. Ace was not detected, but other PAHs were found. The pollution level of PAHs was 43.66 ± 15.79 mg kg-1; and 4-ring PAHs, which accounted for 35.14% of PAHs, were the main pollutants. The contents of BeP and BghiP were the highest, accounting for 12.23% and 12.06% of PAHs, respectively. The PAHs concentrations were found to be higher in winter due to the physicochemical characteristics of PAHs and the meteorological conditions. The sequence of PAHs concentrations was: sub-arterial road in winter > arterial road in winter > arterial road in autumn > sub-arterial road in autumn. Traffic emission and industrial sources led to higher PAHs concentrations on the arterial roads in autumn. Meteorological conditions and road characteristics, such as vehicular speed, frequency of road dust sweeping, and road width, led to higher PAHs concentrations on the sub-arterial roads in winter. Principal component analysis (PCA) and the ratios of Ant/(Ant + Phe), Flu/(Flu + Pyr), InP/(InP + BP), and BaA/(BaA + Chr) were used to distinguish the PAHs sources, which indicated fossil fuel combustion, traffic emissions, and petroleum exhaust as the main PAHs sources. The application of the ILCR model for PAHs in road dust showed a higher carcinogenic risk for children and adults (6.01 × 10-5 and 5.80 × 10-5, respectively) on the sub-arterial roads in winter, indicating a high potential carcinogenic risk at the Chemical Industrial Park.

[Molecular and Carbon Isotopic Compositions of n-Alkanoic Acids in Smoke from Maize Straw Combustion].

Four cultivars of maize straw were burned under flaming and smoldering conditions. Smoke samples were colleted and analyzed by GC/MS and GC/C/IRMS to determine molecular and stable carbon isotopic compositions of n-alkanoic acids in them. The results showed that n-alkanoic acids in flaming smoke were composed of C7 to C34, with a mean total content of 13895.0 mg·kg-1. The average ratio values of the content for homologues with lower carbon number (≤C16) to that for ones with higher carbon number (>C16) (L/H), C18/C16, C24/C16, C24/C18, and C24/(C22+C26) (CAR) were 1.1, 0.33, 0.17, 0.50, and 1.2, respectively. Moreover, the acids exhibited a bimodal profile with peaks at C16 and C24, respectively. They had evident even to odd carbon number predominance (mean CPI: 4.5). In smoldering smoke the acids were consisted of C6 to C34, with an average total content of 50183.7 mg·kg-1. The mean ratios of L/H, C18/C16, C24/C16, C24/C18, and CAR were 1.3, 0.33, 0.20, 0.60, and 1.6, respectively. In addition, the homologues had the same distribution pattern as in flaming smoke and even to odd carbon number predominance (mean CPI=6.1). The mean carbon isotopic ratio (δ13 C) values for individual n-alkanoic acids (C14 to C26) in flaming smoke ranged from -21.0‰ to -24.8‰, the overall average of which was -23.5‰. The difference between mean δ13 C values of n-fatty acids in flaming smoke and the straw (Δ13 C) was -0.7‰. In smoldering smoke, the mean δ13 C values for the compounds varied from -21.8‰ to -25.4‰, with an overall average of -23.3‰. The Δ13 C value was up to -0.5‰. The molecular and carbon isotopic compositions of n-alkanoic acids in smoke were significantly different from those in straw matter. L/H, C24/C16, C24/C18, CAR, and δ13 C might be useful proxies to discriminate the organic pollutants in atmospheric aerosols derived from maize straw combustion.

[Chemical Composition of Alkanes and Organic Acids in Vehicle Exhaust].

The soot of 11 diesel buses and 20 gasoline cars was sampled by direct sampling, and the main organic compounds of the samples were separated and qualitatively analyzed by GC-MS. The results showed that the mass fraction of n-alkanes was 1.31-149.08 µg·g-1 and 15.35-556.03 µg·g-1. The main carbon number of n-alkanes in diesel buses and gasoline cars soot was 20 and 29, respectively, and gasoline cars generated more long chain alkanes with high boiling point. The total mass fraction of pristane and phytane in diesel buses was 15.24 µg·g-1 and 21.79 µg·g-1, respectively, while the two values in gasoline cars were 2.31 µg·g-1 and 2.69 µg·g-1, respectively. The ratios of pristane and phytane were 0.6994 and 0.8587, and the ratios of phytane and octadecane were 0.3565 and 0.7472. The changes of the relative mass of fatty acids were relatively large, the change ranges in buses and cars were 0.01-40.87 µg·g-1 and 3.8-113.7 µg·g-1, respectively, and the organic acid with the highest content in the buses was 3- hydroxybutyric acid.The maximal ratio of hexadecanoic acid and butanedioic acid (C3/C4) was 5.93. The most abundant n-alkanes in gasoline cars soot was C16, and the mass fraction of aromatic acids was 5.05-31.70 µg·g-1 and 0.1-228.38 µg·g-1, respectively.

[Chemical Composition of Water-soluble Ions in Smoke Emitted from Tree Branch Combustion].

Water-soluble ions in particulate matter (PM) from tree branch combustion were determined. The results showed that the average content of total water-soluble ions in flaming PM from dry branches was (28.88±17.54) g·kg-1. The major components included Cl-, SO42-, and K+, the mean emission factors (EFs) of which were in the range of 101.0 to 118.2 mg·kg-1. In addition, the mean content of the total ions in smoldering PM was (6.38±2.79) g·kg-1. The main constituents contained Na+, SO42-, K+, and Cl-, the mean EFs of which varied from 101.1 to 245.7 mg·kg-1. The average content of the total ions in flaming PM from green branches was (22.13±13.52) g·kg-1. Their major components were SO42-, Cl-, and K+, with mean EFs ranging from 136.4 to 197.6 mg·kg-1. Furthermore, the mean content of all ions in smoldering PM derived from green branches was (15.71±19.09) g·kg-1. Cl-, SO42-, and Na+ were the main components, with mean EFs varying from 298.6 to 869.1 mg·kg-1. Significant correlations were found between the contents of Cl- and K+ in PM from dry and (or) green branches burned under each condition. Similar relation also existed between EFs of Cl- from the dry branches burned in smoldering condition and the moisture in them. The EFs of Cl-, K+, and Mg2+ were positively correlated with moisture while the green branches were burned in flaming condition. The EFs of Cl-, Na+, NH4+, and Mg2+ were significantly positively correlated with moisture as well when the fuels were combusted in smoldering condition. Combustion conditions, tree types, and moisture in wood fuels all had impacts on the chemical compositions and EFs of water-soluble ions in PM from tree branches. This may have significance in estimating the quantity of the pollutants from forest fires.

[Organic Carbon and Elemental Carbon in Forest Biomass Burning Smoke].

Ten kinds of trees were selected for preparing dry and wet stick samples. Concentrations of organic carbon (OC), elemental carbon (EC) in particular matter produced by sticks samples in the flaming and smoldering were analyzed through the Thermal Optical Carbon Analyzer (Model 2001A). The results showed that mean values of OC (EF(OC)), EC (EF(EC)), PM (EF(PM)) emission factors were 6.8, 2.1, 16.5 g x kg(-1) in the dry stick flaming smoke, 57.5, 11.1, 130.9 g x kg(-1) in the dry stick smoldering smoke, 13.6, 3.3, 30.5 g x kg(-1) in the wet stick flaming smoke, 57.6, 9.6, 125.6 g x kg(-1) in the wet stick smoldering smoke. Compared to the flaming condition, EF(OC), EF(EC), EF(PM), were much higher in the smoldering condition. In the flaming condition, EF(OC), EF(EC), EF(PM) had positive correlations with the moisture content. The mean values of OC/PM, EC/PM, TC/PM (TC = OC + EC) were 45%, 10%, 55%, and the mass fractions of OC was much higher in smoldering condition than those in flaming condition, but the mass fractions of EC was lower in the smoldering condition. Compared to dry sticks, the smoke of wet sticks combustion had higher mass fractions of OC and lower mass fractions of EC. The mean value of OC/EC was 3.3 (2.5-5.2) in the dry stick flaming smoke, and was 5.2 (4.3-6.3) in the dry stick smoldering smoke, in the wet stick flaming smoke was 4.1 (3.1-5.3), and was 6.2 (4.2-8.4) in the wet stick smoldering smoke. Compared to the flaming condition, the mean value of OC/EC was higher in the smoldering condition, and the mean value of OC/EC was much higher in high moisture content stick combustion smoke. The correlation coefficient between OC and EC was 0.985 in dry stick combustions, and was 0.915 in wet stick combustions. So, based on the flaming and smoldering condition, the correlation between OC and EC was significant in different moisture contents of sticks.

[Emission of Particulate Matter, Organic and Elemental Carbon from Burning of Fallen Leaves].

The two kinds of burning conditions, i. e., flaming and smoldering, were selected to investigate the particulate matter (PM), organic carbon (OC), and elemental carbon ( EC) from burning of ten kinds of fallen leaves. In the experiment, the emission smoke was sampled from the fallen leaves burning, in which the OC and EC loadings were measured by the Thermal Optical Carbon Analyzer. The results showed that the emission factors of PM, OC, and EC were 7.9-31.9, 0.9-9.7, and 3.6-13.9 g x kg(-1), with the average values of 19.7, 5.2, and 6.8 g x kg(-1), respectively, under the flaming condition. The emission factors of PM, OC, and EC were 61.3-128.9, 31.7-60.4, and 1.9-6.0 g x kg(-1), with the average values of 91.0, 43.0, and 4.0 g x kg(-1), respectively, under the smoldering condition. The OC/EC ratio ranged from 0.21 to 1.82 and from 8.16 to 16.84 under the flaming and smoldering condition, respectively. The OC/PM and EC/PM ratios ranged from 0.11 to 0.41 and from 0.18 to 0.56, respectively under the flaming condition. The OC/PM and EC/PM ratios, however, ranged from 0.43 to 0.53 and from 0.03 to 0.06, respectively, under the smoldering condition. The OC emission factor was well correlated with the PM emission factor in the two burning conditions. Those results indicated that rather different emission factors occurred in all kind of components in different burning emission. In addition, the OC emission factor was higher under the smoldering condition than that under the flaming condition. However, the EC emission factor was higher under flaming condition, compared with that under smoldering condition. Analysis of the PM, OC, and EC emission factor and their ratios was beneficial for building the emission list from the biomass burning and the sources apportionment.

[Organic and element carbon in foliar smoke].

A home-made combustion and sampling apparatus was used to burn green leaves under flaming and smoldering conditions and to collect the smoke generated. The smoke was measured with Organic/Elemental Carbon (OC/EC) Analyzer using IMPROVE thermal-optical reflectance (TOR) method, to investigate the mass fractions and the distribution of OC, EC and eight carbon fractions in foliar smoke. The results showed that in smoldering condition, the mean OC, EC mass fractions of ten foliar smokes were 48.9% and 4.5%, respectively. The mean mass fraction of char-EC (EC1 - POC) was 4.4%. The average emission factors (EF) of particulate matters, OC and EC in smoldering foliar smoke were 102.4 g x kg(-1), 50.0 g x kg(-1) and 4.7 g x kg(-1), respectively. The mean ratios of OC/EC, OC1/OC2 and char-EC/soot-EC (EC1 - POC/EC2 + EC3) in this condition were 11.5, 1.9 and 48.1, respectively. For the foliar smoke emitted in flaming condition, the mean mass fractions of OC, EC and char-EC were 44.9%, 10.9% and 10.7%, respectively. The average EF of PM, OC and EC in flaming smoke were 59.2 g x kg(-1), 26.6 g x kg(-1) and 6.0 g x kg(-1). And the three ratios mentioned above in this condition were 4.8, 1.1 and 133.0, respectively. In conclusion, foliar smoke had higher OC1 mass fractions and OC1/OC2 values in smoldering condition. While flaming foliar smoke had higher char-EC mass fractions and char-EC/soot-EC values. The compositions of OC, EC in foliar smoke varied between different tree species and different combustion conditions. The composition was also obviously different from those of other biomass smoke.

[Composition of organic carbon/elemental carbon and water-soluble ions in rice straw burning].

Six types of rice straw were selected in China in this paper, the homemade biomass combustion devices were used to simulate the outdoor burning. The concentrations of organic carbon (OC), elemental carbon (C) and water-soluble ions in particular matter produced by the flaming and smoldering were analyzed using Thermal Optical Carbon Analyzer (Model 2001A) and Ion Chromatography(ISC 2000/ISC 3000). The results showed that the mean value of OC (EFoc) and EC (EFEC) emission factors were (6.37 +/- 1.86) g x kg(-1) and (1.07 +/- 0.30) g x kg(-1) under the flaming conditions, respectively, while under the smoldering conditions the two mean values were (37.63 +/- 6.26) g x kg(-1) and (4.98 x 1.42) g x kg(-1). PM, OC and EC emitted from the same kind of rice straw had similar change trends. The average values of OC/EC under flaming and smoldering were 5.96 and 7.80, and the value of OC/PM was almost unchanged along with the combustion state. Nevertheless, the values of EC/PM under flaming and smoldering were 0.06-0.08 and 0.08-0.11, respectively. The trend of combustion state could be determined using the ratio of EC/PM and the RZ of emitted OC and EC through those two types of combustion reached 0. 97, which was significantly correlated at the 0. 01 level. Among the anions, Cl- showed the highest concentration, the results indicated that the average value of of Cl- emission factor was (0.246 +/- 0.150) g x kg(-1) under flaming, while it was (0.301 +/- 0.274) g x kg(-1) under smoldering. However, A big difference between flaming and smoldering was found in the average value of K+ emission factor, where (0.118 +/- 0.051) g x kg(-1) of the former was significantly higher than the latter (0.053 +/- 0.031) g x kg(-1). When it came to Na, the result of smoldering was significantly higher than that of flaming. The correlation between water-soluble ions in flaming was more significant than smoldering. Rice straw burning could be distinguished from fossil fuels and some other biomass burning by the OC/EC ratio, and it could also be distinguished from sort of trees burning by the ratio of K+ /Na+, Cl-/Na+ in water-soluble ions.

[Isotope compositions of elemental carbon in the smoke and ash from crop straw combustion].

Six genotypes of straws for rice, maize and wheat, respectively, were combusted under flaming and smoldering conditions, and the isotope compositions for elemental carbon ( EC) in the straw smoke and ash were investigated with an isotopic mass spectrometer. The results showed that the mean delta 13C values for EC in the flaming and smoldering smoke of rice straw were - 28. 3 per thousand and - 28.7 per thousand, with depletions of 2.7 per thousand and 3. 0 per thousand relative to that of total carbon (TC) in the straw, respectively. The mean delta 13C values for EC in the flaming and smoldering smoke of wheat straw were -28.5 per thousand and - 28. 0 per thousand, with a depletion of 0. 1 per thousand and enrichment of 0. 4 per thousand comparing to TC in the straw, respectively. The average values in two types of maize straw smoke were -17.2 per thousand and - 13. 6 per thousand,with a depletion of 3.4 per thousand and an enrichment of 0. 2 per thousand relative to TC in the straw, respectively. The mean delta 13C ratios for EC in the flaming and smoldering ash of rice straw were -27. 5 per thousand and -27. 3 per thousand, with depletions of 1.8 per thousand and 1. 6 per thousand comparing with TC in the straw, respectively. In the flaming and smoldering ash of wheat straw, the mean ratios were -27.4 per thousand and -26.0 per thousand, with enrichments of 0. 9 per thousand and 2. 4 per thousand relative to TC in the straw, respectively. In the two types of ash for maize straw, the average delta13 C values for EC were - 15. 0 per thousand and - 14. 8 per thousand,which were 1. 2 per thousand and 1.0 per thousand lighter than those of the straw TC. In general, evident isotope fractionations occur between EC in both smoke and ash and TC in the corresponding straws, especially for rice and maize straws. The isotopic ratios may be useful in identifying and estimating the contribution of EC from straw combustion to ambient aerosol.

[Chemical compositions of n-alkanols in smoke from rice and maize straw combustion].

Six genotypes of rice straw and four genotypes of maize straw were burned under different conditions, and the smoke was collected and n-alkanol in it was measured by GC-MS. Results showed that, in the smoke from rice straw flaming combustion, n-alkanol was composed of individual compounds from C14 to C34, and total contents(sigma) changed in the range of 1 604.4 to 13 889.7 mg x kg(-1). The ratio values of amount for n-alkanol with lower carbon number to that for one with higher carbon number (L/H) were in the range of 0.02 to 0.09. The values for C24/C30, C32/C30, C30/sigma, CPI, and ACL varied from 3.3% to 19.6%, 8.4% to 19.9%, 53.9% to 72.6%, 8.7 to 21.5, and 29.0 to 30.1, respectively. The abundance distribution for the compounds was bimodal with the maximal and the second peaks at C30 and C24, respectively. In smoldering smoke of rice straw, individual n-alkanol from C14 to C34 were also analyzed, with sigma values varying in the range of 1 688.7 to 5 168.2 mg x kg(-1). The ratios for L/H, C24/C30, C32/ C30, and C30/sigma ranged from 0.08 to 0.14, 31.0% to 70.5%, 6.9% to 17.6%, 39.5% to 57.8%, respectively. In addition, the CPI and ACL values varied from 10.7 to 17. 5, and 27.2 to 28.5, respectively. Moreover, the distribution pattern was similar to that in flaming smoke. In flaming smoke of maize straw, n-alkanol from C12 to C34 were identified, with sigma values being in the range of 852.3 to 2 667.9 mg x kg(-1). The values for L/H, C24/C28, C32/C28, C28/sigma, CPI, and ACL varied from 0.2 to 1.0, 104.3% to 293.3%, 42.2% to 61.4%, 7.3% to 16.5%, 5.6 to 9.7, and 23.1 to 26.9, respectively. Besides, the abundance distribution pattern was mainly bimodal with a maximal peak at C30, C24 or C22. In the smoldering smoke for maize straw, the same individual n-alkanols were found, and the sigma values changed from 1493.0 to 8386.9 mg x kg(-1). The values for L/H, C24/C28, C32/C28, C28/sigma, CPI and ACL were in the range of 0.2 to 0.3, 53.6% to 217.6%, 21.7% to 75.9%, 8.8% to 27.3%, 4.2 to 6.5, and 26.3 to 27.2, respectively. Furthermore, the distribution pattern was bimodal as well with the highest peak mainly at C30 and the second one at C24. In brief, obvious discrimination exists among chemical compositions of n-alkanol in the straw and smoke. C24/C30, C32/C30, and C30/sigma are useful proxies in distinguishing between n-alkanol in airborne aerosol deriving from rice straw and one released in rice straw combustion process. L/H, C24/C28, C32/C28, and C28/sigma may have a potential in discriminating the compounds from maize straw and its burning. L/H is possibly used to makea distinction between the organic compounds from rice and maize straws, and/or from combustion of the straws.

[Chemical compositions of n-alkanoic acids in wheat straw and its smoke].

Wheat straws of six genotypes were burned under different conditions, and n-alkanoic acids in the straw and its smoke were measured by GC/MS. The results showed that the carbon number of the fatty acids in all the smoke ranged from C8 to C32. In the flaming smoke, the total amounts of the compounds varied from 1,509.3 to 10,543.7 mg x kg(- ), with a mean value of 5,871.2 mg x kg(-1). And the content ratio values of n-alkanoic acids with low carbon number (C8 to C16) to those with high carbon number (C17 to C32) (L/H) were between 0.8 and 5.3, with an average of 2.8. In addition, the mean values for C14/C16, C28/C16 and C30/C16 were 16.5%,14.1% and 11.4%, respectively. The distribution of the compounds in the smoke was bimodal with the peak carbon number of C16 followed by C28 or C30, and it showed an even carbon number preference. The mean values of carbon preference index (CPI) and average carbon chain length (ACL) were 19.8 and 18.2, respectively. In the smoldering smoke,the total amounts of the fatty acids were in the range of 5,799.3 to 37,244 mg x kg(-1), and the mean was 15,838.6 mg x kg(-1). Moreover, the L/H ratios varied from 1.2 to 5.6, with a mean value of 4.2. The average ratio values for C14/C16, C28/C16 and C30/C16 were 12.7% , 10.1% and 6.0%, respectively. The content distribution pattern of the compounds was similar to that in the flaming smoke, and the mean values of CPI and ACL were 24.7 and 17.7, respectively. In general, n-alkanoic acids in both wheat straw and its two types of smoke had similar distribution modes, both with even carbon number preference, but there was prominent distinction among the chemical compositions of the compounds in the straw and the smokes. This is maybe useful in identifying the organic matter from wheat straw or its smoke in the atmospheric aerosol.

[Chemical composition of n-alkanes in wheat straw and smoke].

Straw of six wheat species was burned under flaming and smoldering conditions. Chemical compositions of n-alkanes in the straw and its smoke were measured with GC/MS. The results showed, the main compounds in all samples were C16 to C33, and the total amounts of n-alkanes in the straw were between 19.6 and 62.3 mg x kg(-1), with a mean value of 36.0 mg x kg(-1). Moreover, the ratios of the contents of n-alkanes with low carbon number (< C23) to the total n-alkanes varied from 1.4% to 31.6%. The C27/C29 values in straws ranged from 20.2% to 47.4% with an average of 33.7%, and the C31/C29 values ranged from 22.9% to 48.1% with a mean value of 32.7%. In the flaming smoke, the total contents were 764.2 to 5 304.1 mg x kg(-1), with a mean value of 2 854.2 mg x kg(-1). And the contribution of the compounds with low carbon number to the total contents was 2.0% to 19.4%, the mean of which was 7.1%. Furthermore, the C27/C29 ratios changed from 10.0% to 31.6% with an average of 20.2%, and the C31/C29 values ranged from 47.1% to 98.9% with a mean of 71.2%. In the smoldering smoke, the total contents were in the range of 5 126 to 15 898 mg x kg(-1), and the mean value was 9 220.8 mg kg(-1). The ratios of the content of n-alkanes with low carbon number to the total n-alkanes varied from 1.9% to 13.0%, and the average value was 5.5%. In addition, the C27/C29 values ranged from 8.6% to 23.0% with a mean of 13.8%, and C31/C29 ratios varied from 42.5% to 90.2% with an average of 62.2%. In both the straw and the smoke, n-alkanes showed unimodal distribution with a peak at C29. The compounds with high carbon number (> C21) in all samples had evident odd to even carbon number predominance. The carbon predominance index (CPI) for the straw ranged from 4.0 to 33.6 with a mean value of 19. 2, and the corresponding average carbon chain length (ACL) varied from 25.2 to 29.0 with a mean of 28.0. The CPI for flaming smoke was between 4.4 and 27.1 with a mean value of 12.4, and the corresponding ACL varied from 27.6 to 29.4 with an average value of 28.8. The CPI values for smoldering smoke ranged from 5.5 to 29.6 with a mean of 18.0, and the ACL was from 28.0 to 29.5 with an average value of 28.9. In short, there were visible differentiations among the chemical compositions of n-alkanes in wheat straw and its smoke, which are helpful for identifying the organic contaminants in ambient aerosol from wheat straw burning.

[Carbon isotopic compositions of n-alkanes and n-alkanoic acids in the smoke from combustion of rice straw].

In order to investigate the carbon isotopic fractionation in n-alkanes and n-alkanoic acids in smoke from rice straw combustion, six types of rice straw were burned in laboratory under flaming and smoldering conditions, and the compound specific isotopic compositions for the two classes of biomarkers in the smoke were determined. The results showed that the delta13C values of individual n-alkanes and n-alkanoic acids released from flaming burns of all the rice species ranged from -28.6 per thousand to -38.8 per thousand and from -29.6 per thousand to -41.9per thousand, respectively, and that the mean delta13C values for the two compound classes in the flaming smoke for the six types of rice straw were in the range of -32.6 per thousand to -36. 4per thousand and -34.0 per thousand to -36.2 per thousand, respectively. Moreover, the n-alkanes in the smoke from the most straws were more depleted in 13C in general than the identical substances with equal carbon number in corresponding unburned biomass. The magnitude of the isotopic discrimination (delta) was up to 4.1per thousand. Conversely, the n-alkanoic acids in the smoke tended to be more enriched in 13C than the corresponding biomarkers in the unburned straw for all of the species, and the delta was up to 6.3 per thousand. The delta13C values of the individual n-alkanes and n-alkanoic acids in the smoke from smoldering burns of the six species varied between -31.7 per thousand and -39.0 per thousand and between -31.3 per thousand and -38.8 per thousand, respectively. The average values for the two compound classes in the smoke for a species were in the range of -35.1 per thousand to -36.4 per thousand and -34.4 per thousand to -35.6 per thousand, respectively. The compound specific delta13C values of the n-alkanes in the smoke for most species were smaller than those of the same substances in the corresponding rice straw, and the greatest delta was 6.1 per thousand. However, the delta13C values of n-alkanoic acids in the smoke were greater than those in the rice straw, and the delta was up to 8.4 per thousand. The n-alkanes from the smoldering burn were more depleted in 13C than those from the flaming burn of the identical rice species, whereas the n-alkanoic acids (> or = C19) more enriched in 13C. These results suggest that there is significant difference in the carbon isotopic composition of individual n-alkanes or n-alkanoic acids in the smoke derived from rice straw combustion and the unburned biomass, and that converse carbon isotopic fractionation occurs in the two compound classes in the smoke relative to those in the rice straw.

[Distribution characteristics and sources identification of PAHs in ancient paddy soil].

Soil samples of current paddy soils, ancient paddy soil/ancient dry land soil, and bottom soils were collected from two sites in Chuodunshan Site of Majiabang Culture (about 6,000a). 15 polycyclic aromatic hydrocarbons (PAHs) were analyzed with HPLC, and their possible sources were identified. The sum of 15 PAHs was 202.9microg x kg(-1) and 207.7microg x kg(-1) in the surface soils from Site A and Site B respectively, which were mainly deposited from atmosphere. In ancient paddy soil from Site A, the total PAHs concentration sharply decreased to 56.0microg x kg(-1), but was still higher than those in ancient dry land soil and bottom soils with the sum of 32.0 approximately 36.9microg x kg(-1). In ancient paddy soil, the concentrations of 2-ring and 3-ring PAHs took a larger portion of 63 percents to the total PAHs, and naphthalene and phenanthrene were the most abundant compounds, while PAHs of more than 4 rings took a small part. The ratios of phenanthrene anthracene and benzo(a) anthracene chrysene and 13C-NMR spectrum of soil organic matter showed that PAHs in ancient paddy soil mainly originated from rice straw burning, biogenesis under reducing conditions may be another source.

Sorption of pyrene on two paddy soils and their particle-size fractions.

In the present study, the sorption of pyrene on two kinds of bulk paddy soils, Gleyic Stagnic Anthrosols, and Ferric accumulic Stagnic Anthrosols as well as their particle-size fractions was investigated. The sorption isotherms fitted well with Freundlich equation. For both soils, the clay fraction( < 2 microm) and coarse sand fraction(2000-250 microm) had higher sorption capacity than fine sand fraction(250-20 microm) and silt fraction(20-2 microm). The log Koc values obtained of each soil and its particle-size fractions were similar, proving that SOM content was a key factor affecting pyrene sorption. The Kd values showed a significant correlation with contents of dithionite-extractable Fe in both paddy soils and a good relationship with CEC in Gleyic Stagnic Anthrosols, indicating possible effects of surface properties of particle-size fractions on the sorption of pyrene.

[Aging of spiked pyrene in two paddy soils and their particle-size fractions after soil incubation and changes in extractability and bio-availability to earthworm].

Effect of aging on bioavailability and extractability of persistent organic pollutants has recently been paid much attention in environmental studies. This study deals with aging of spiked pyrene, a four-ring polycyclic hydrocarbon, in two paddy soils and their particle-size fractions under laboratory incubation and change in its extractability and bioavailability. The bioavailability of aged pyrene was tested by an assay of exposure to earthworms (Eisenia foetida). The extractability of spiked pyrene was decreased by 15% to 23%, and the bioavailability to earthworm was decreased by 37% to 67% after incubation for 90 d compared to under no incubation. Meanwhile, there was no significant difference in the pyrene extractability between incubation with different size fractions of a single soil. Soil incubation resulted in lower extractability and, thus, lower environmental risk of the organic pollutants after incorporation in paddy soils and their aggregates. The different size fractions of paddy soils may exert different bioavailability when exposure to soil fauna. Thus, content and chemical extractability may not be appropriate index for assessing the potential environmental risk and bioavailability to soil fauna for persistent organic pollutants in paddy soils.