Transient interaction effects of temperature and light intensity on isoprene and monoterpene emissions from Schima superba and Phoebe bournei.

Biogenic volatile organic compound (BVOC) (such as isoprene (ISO) and monoterpenes (MTs)) emissions from plants play a great role in the atmospheric chemistry. Now frequency of dramatic changes of weather such as transient temperature changing increases, most current studies focus on the effects of simulating climate change (long-term) on BVOC emissions. While studies of transient effects on that are less reported. This study aimed to identify the ISO and MT emissions and the related physiological processes in the short-term scale at different temperature (T) and light intensity (PAR), in seeding stage of Schima superba and Phoebe bournei belonging to typical subtropical tree species. The results showed that the ISO and MT emissions were significantly affected by T and PAR, either independently or interactively. With the increase of T and PAR, the ISO and MT emissions increased, with the maximum rates of ISO and MTs of 39.39 and 1042.35 pmol m-2 s-1 for S. superba under 40 °C × 500 µmol m-2 s-1 condition, while the maximum rates reached 18.73 and 6737.41 pmol m-2 s-1 at 30 °C × 1500 µmol m-2 s-1 for P. bournei. The increase of ISO and MT emissions with T and PAR increasing that was related to the promotion of Pn and gs in plants. Regarding MT components, the proportion of α-pinene decreased with T and PAR increasing, with the lowest ratios of 4.91 % and 21.16 % for S. superba and P. bournei under 40 °C × 1500 µmol m-2 s-1 condition. However, the proportion of ß-pinene significantly increased, with the highest ratios of 67.42 % and 57.93 % for S. superba and P. bournei under 30 °C × 1500 µmol m-2 s-1 condition, which is attributed to differences in light tolerance between the two plants. Our study provides basis for evaluating the transient changes of environmental factors on BVOC emissions and optimizing regional BVOC emission models.

[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.

Biogenic volatile organic compound emissions from Pinus massoniana and Schima superba seedlings: Their responses to foliar and soil application of nitrogen.

Increasing nitrogen (N) deposition is one of the main drivers of global change, while the emission of biogenic volatile organic compounds (BVOCs) from plant in response to elevated N deposition is poorly understood, especially with respect to the response to foliar application of N. In this study, BVOC emissions from two tree species (Pinus massoniana Lamb. and Schima superba Gardn. et Champ.) were determined by dynamic chamber coupled with a proton transfer reaction-time of flight-mass spectrometer. Two N application methods, namely soil application of N (SAN) and foliar application of N (FAN), and three N levels (5.6, 15.6 and 20.6 g N m-2 yr-1) were employed by applying NH4NO3 every week for 1.5 years. The results showed that: (1) oxygenated volatile organic compounds (OVOCs, mainly acetaldehyde, methyl alcohol, ethenone and acetone) and non-methane hydrocarbons (NMHCs, mainly monoterpenes, propyne, 1,3-butadiene and propylene) were the dominant BVOCs for all the treatments, accounting for 32.40-65.72% and 19.21-47.39% of total 100 determined BVOC compounds, respectively; (2) for S. superba seedlings, both SAN and FAN treatments significantly decreased total BVOC emissions (11.83% to 66.23%). However, total BVOCs from P. massoniana significantly increased with N addition for SAN treatment, while no difference were found in the FAN treatment; (3) BVOC emission rates for FAN treatment were significantly lower than those for SAN treatment, indicating that previous studies which simulated N deposition by adding N directly to soil might have imprecisely estimated their effects on plant BVOC emissions. Considering the inconsistent responses of BVOC emissions to different N application methods for different plant species, close attention should be paid on the effects of N deposition or even global change on plant BVOC emissions in the future.

[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.