[Forming potential of secondary organic aerosols and sources apportionment of VOCs in autumn of Shanghai, China].

A continuous measurement was conducted in urban area of Shanghai from 1stSeptember to 21st November, 2011. The mass concentration of PM2.5 and the mixing ratio of VOCs were obtained during the period. Four pollution episodes were observed: PD1 (20th-23th September), PD2 (5th-9th October), PD3 (13rd - 18th October), PD4 (10th - 14th November). The average mass concentrations of PM2.5 were (45+/-16), (76+/-46), (57+/-36) and (122+/-92) microg.m-3, respectively. The mixing ratio of VOCs were (30.87+/-30.77) x10(-9), (32.09+/-30.69) x10(-)9, (34.04+/-28.13) x10(-9) and (44.27+/-31.58) x10(-9). Alkane, alkene and aromatic hydrocarbons accounted for 53. 58% , 27. 89% , and 10. 96% of the total VOCs, respectively. The OH radical loss rate (LOH) and the ozone formation potential (OFP) were applied to assess the chemical reactivity of VOCs, the results showed that the alkenes and aromatics were the most important contributors to LOH and OFP in the atmosphere in the urban area of Shanghai, in autumn. Fractional aerosol coefficients (FAC) and the ratio of organic carbon to element carbon (OC/EC) were used to estimate the potential formation of secondary organic aerosols (SOA) in Shanghai, the SOA concentration values obtained by the two methods were 1.43 microg.m-3 and 4.54 microg.m-3, respectively. The value predicted by OC/EC was significantly higher, which was mainly due to the low amount of SOA precursors measured in this study. The aromatics were not only the most important contributors to OFP, but also important SOA precursors. By applying the positive matrix factorization (PMF) model, six major sources were extracted to identify the sources of VOCs in autumn in Shanghai, including vehicle exhaust (24.30%), incomplete combustion (17.39%), fuel evaporation (16.01%) , LPG/NG leakage (15.21%) , petrochemical industry (14.00% ), and paint/solvent usage (13.09%). Vehicle exhaust and paint/solvent usage contain abundant aromatics species which are the most important contributors to OFP and important SOA precursors. The above two sources contributed 37.39% of the total VOCs concentration. Hence, these sources should be listed as priority of air pollution control strategy for Shanghai in future.

[Source profile and chemical reactivity of volatile organic compounds from vehicle exhaust].

Light-duty gasoline taxis (LDGT) and passenger cars (LDGV), heavy-duty diesel buses (HDDB) and trucks (HDDT), gasoline motorcycles (MC) and LPG scooters (LPGS), were selected for tailpipe volatile organic compounds (VOCs) samplings by using transient dynamometer and on road test combined with SUMMA canisters technology. The samples were tested by GC-MS to analyze the concentration and species composition of VOCs. The results indicate that light-duty gasoline automobiles have higher fractions of aromatic hydrocarbons, which account for 43.38%-44.45% of the total VOCs, the main aromatic hydrocarbons are toluene and xylenes. Heavy-duty diesel vehicles have higher fractions of alkanes, which constitute 46.86%-48.57% of the total VOCs, the main alkanes are propane, n-dodecane and n-undecane. In addition, oxy-organics account for 13.28%-15.01% of the VOCs, the main oxy-organics is acetone. The major compound from MC and LPGS exhaust is acetylene, it accounts for 39.75% and 76.67% of the total VOCs, respectively. VOCs exhaust from gasoline motorcycles and light-duty gasoline automobiles has a significantly higher chemical reactivity than those from heavy-duty diesel vehicles, which contribute 55% and 44% to the atmospheric chemical reactivity in Shanghai. The gasoline motorcycles and light-duty gasoline automobiles are the key pollution sources affecting city and region ambient oxidation, and the key active species of toluene, xylenes, propylene, and styrene make the greatest contribution.

[The expression of TGF-beta1 and bFGF after LASEK and the effects of 20% ethanol exposure on corneal wound healing].

OBJECTIVE: To assess the effects of 20% ethanol used in LASEK on corneal wound healing. METHODS: Forty-eight eyes from 24 rabbits were deepithelialized by two techniques. The epithelium were detached with either 20% ethanol (applied for 30 seconds) or mechanical scraping, then ablated was performed. The number of superficial stromal keratocytes was counted and the morphologic changes were observed. Expression of TGF-beta1 and bFGF mRNAs was detected and analyzed by reverse transcription-polymerase chain reaction and immunocytochemical methods at 1, 7, 30 and 90 days after the surgery. RESULTS: One day after the surgery, the expression of TGF-beta1 and bFGF in the keratocytes in both treated groups was lower than that of the normal controls. Seven days after the surgery, the expression of TGF-beta1 and bFGF in both treated groups was greater than that of the normal controls (P < 0.01). The expression in the alcohol-treated group was greater than that of the surgical-treated group (P < 0.01). The expression of TGF-beta1 and bFGF reached the peak 30 days after the surgery, no significant difference was detected between the alcohol-treated and surgical-treated groups. There was no significant difference in expression level between the alcohol-treated and surgical-treated groups 3 months after the surgery; as well as between treated groups and normal group. The amount of TGF-beta1 and bFGF mRNA was positively correlated with the number of keratocytes. The correlation coefficient between TGF-beta1 and bFGF mRNA and the number of the keratocytes was 0.744 (P < 0.01) and 0.738 (P < 0.01) in the alcohol-treated group; and was 0.664 (P < 0.01) and 0.785 (P < 0.01) in the surgical-treated group, respectively. CONCLUSIONS: The expression of TGF-beta1 and bFGF mRNA undergo a dynamic process of "decrease-increase-normal". Although ethanol has a slight toxic effect on rabbit epithelial cells, but the effects do not persist over time, therefore, it is relatively safe to use the alcohol treatment in the LASEK.