[Effects of temporal and spatial variation of canopy structures and light conditions on population characteristics of Fargesia decurvata.] / å† å±‚ç»“æž„å’Œå ‰çŽ¯å¢ƒçš„æ—¶ç©ºå˜åŒ–å¯¹ç´«è€³ç®­ç«¹ç§ç¾¤ç‰¹å¾çš„å½±å“.

The canopy structures and light conditions and the population characteristics of Fargesia decurvata, a dominant understory species, were investigated in three typical communities, i.e., deciduous broad-leaved forest, evergreen and deciduous broad-leaved mixed forest, evergreen broad-leaved forest. The results showed that with the succession from deciduous broad-leaved forest to evergreen and deciduous broad-leaved mixed forest and to evergreen broad-leaved forest, the Shannon index, Simpson index and Pielou index were increased, suggesting that the development of communities in Jinfo Mountains tended to be stable. Moreover, canopy structures were significantly changed, in that the canopy openness and mean leaf angle decreased, leaf area index increased, and canopy extinction ability enhanced, resulting in the decrease of light intensity under the canopy. The upper canopy was the main contributor for canopy closure, with the crown depth and crown area of canopy being the two main influencing factors. Moreover, canopy structures were significantly correlated with light conditions in the forest, with the greatest influence on the diffuse solar radiation. With the growth season coming, canopy openness and understory light conditions were decreased, while leaf area index increased, and their maximum values appeared in June or July in the three forest types. The maximum and minimum value of mean leaf angle appeared in spring and summer, respectively. Clonal growth of F. decurvata was closely related to canopy structures and light conditions. In evergreen and deciduous broad-leaved mixed forest with moderate light, F. decurvata grew best, with high and thick ramets, high ramet density (29.69±1.68 ind·m-2) and high ability to expand rhizomes. In deciduous broad-leaved forest, the strong light condition caused the reduction of soil water might have effects on the growth of F. decurvata. However, in the evergreen broad-leaved forest with low light condition, ramets of F. decurvata tended to be short and thin, with low ramet density (5.80±1.16 ind·m-2) and the clonal expansion ability. Those results suggested that forest succession would change canopy structures and understory light conditions. Low understory light conditions prohibited the regeneration and development of F. decurvata population.

[Characteristics of Polycyclic Aromatic Hydrocarbons Emitted from Typical Industrial Biomass Boilers].

This research selected 13 types of industrial biomass boilers and used GC-MS technology to investigate the characteristics of 15 polycyclic aromatic hydrocarbons (PAHs) emitted from the boils. The results show that the total emissions of the 15 PAHs was 0.02-27.8 g ·h-1, and the concentration was 0.77-3173 µg ·m-3. There was a large different in the Σ15 PAHs concentration and emissions for each boiler. The maximum concentration appeared in the No.13 boiler sample, and the maximum emissions appeared in the No.4 boiler sample; these have relatively high concentrations of PAHs and large stack gas velocities. PAHs were found to be dominant in the gas phase, with a proportion of 45.9%~100%. Acenaphthylene, phenanthrene, fluoranthene, and pyrene were the main PAHs. The spectral distribution profiles of the 15 PAHs were similar, and the general concentrations were C3,4 rings > C5,6 rings. Diagnostic ratios the fluoranthene to fluoranthene plus pyrene (Flu/(Flu+Pyr)) from biomass combustion were greater than 0.5, except for the No.4 sample, which was 0.4. There were obvious positive interrelationships between O2 and acenaphthylene, acenaphthene, phenanthrene, and anthracene. In addition, there were obvious interrelationships between CO and indeno[1,2,3-cd]pyrene, benzo (g,h,i) perylene, and acenaphthene.

[Monitoring of polychlorinated biphenyls in the atmosphere of the Pearl River Delta using PUF-passive air sampler].

The article research concentration and distribution of atmospheric polychlorinated biphenyls from the Pearl River Delta (PRD) using PUF passive sampling technique. Sampling was conducted at the same time at twenty-one passive sampling sites for consecutive 56 day from August 2005 to October 2005. The results showed middle contaminated levels of PCBs were found in PRD in comparison with other places in the world. Higher contaminated site located FoShan (2 000 pg x m(-3)) in PRD. Concentration range of PCBs are 260 - 2 000 pg x m(-3) and average valuable 670 pg x m(-3) in PRD, 170 - 470 pg x m(-3) and 300 pg x m(-3) in HK. It is obvious that distribution of PCBs in PRD is higher and lower in HK. The results demonstrated that PUF-PAS technique can be used in the monitoring of PAHs in the atmosphere at a regional or global scale.