[Effect of elevated atmospheric CO2 concentration and temperature on volatile halogenated organic compound content in soils of Schima superba and Cunninghamia lanceolata seedlings.] / 大气CO2浓度和温度升高对木荷和杉木幼苗土壤卤代烃含量的影响.

Global changes caused by the increases of atmospheric CO2 concentration and temperature have important effects on soil biogeochemical processes. The synthesis and release of volatile halogenated organic compounds (VOXs) is an important pathway for soil to participate in the global material cycle and energy flow. In this study, Schima superba and Cunninghamia lanceolata seedlings in the southern subtropics were selected as the research objects. Four treatments, including control (CK), elevated CO2 concentration (EC), elevated temperature (ET) and elevated both factors (EC+ET) were set up. The effects of EC and ET on soil VOXs formation were studied by an open-top chamber system coupled with a purging and trapping gas chromatography/mass spectrometry. The results showed that VOXs content in the soil of S. superba seedlings was 0.065-0.252 ng·g-1, which was higher than that of C. lanceolata (0.038-0.136 ng·g-1). At the EC, ET and EC+ET treatments, VOXs contents were reduced in soils of both species. The effect of ET was the most significant, with the decrease rates of 74.2% and 72.1% in both soils, respectively. The change of VOXs content with increasing temperature mainly attributed to the changes of soil moisture and nitrogen content. The content of VOXs in the soils of S. superba seedlings decreased more than that of C. lanceolata under different treatments. In CK, EC, ET and EC+ET treatment, bromodichloromethane (BDCM) (27.5%, 36.7%, 32.9%, 32.6%) and tetrachloromethane (TCM) (9.0%, 16.8%, 22.7%, 15.8%) were the main VOXs in the soil of S. superba seedlings, respectively, while BDCM and dibromomethane (DBM) were the main VOXs in the soil of C. lanceolata seedlings. BDCM accounted for 31.9%, 38.2%, 40.9% and 37.2% of the VOXs content in each treatment, and DBM accounted for 17.9%, 16.5%, 19.2% and 16.0% of the VOXs content, respectively. Simulating elevated atmospheric CO2 concentration and temperature was conducive to more comprehensive reflection of the ecological effect of global climate change, and it could provide data support for improving the VOCs flux model.

[Characteristics of PAHs in the atmosphere in winter and summer in the urban and suburban of Fuzhou].

Air samples from four sampling sites in urban and suburban in Fuzhou were collected by Hi-vol air samplers in winter and summer in 2010, and concentrations of PAHs were analyzed by GC-MSD. The total (particle and gas phase) PAHs concentrations in ambient air were in the range of 115.45-187.76 ng x m(-3) in winter and 45.55-59.20 ng x m(-3) in summer. PAHs in the gas phase were significantly higher than those in the particle phase, and PAHs in winter were higher than those in summer. No significantly difference was found between urban and suburban, with little higher PAHs in urban in winter and lower PAHs in summer. The ratios of PAHs in the gas phase to particle phase in summer were significantly higher than those in winter. The 2-4 rings PAHs were the dominant components in the gas phase while PAHs in the particle phase were dominated by 4-6 rings. The 3 rings PAHs were the dominant components in the gas phase in winter while 3 and 4 rings in summer. No significantly seasonal trends of PAHs components were found in the particle phase. The toxic equivalence factor (TEF) assessment showed that the pollution of PAHs in Fuzhou city was at a low level. Source analysis indicated that PAHs mainly came from combustion and diesel fuel was the predominant fuel in Fuzhou.