Soil resource availability is much more important than soil resource heterogeneity in determining the species diversity and abundance of karst plant communities.

Resource availability and heterogeneity are recognized as two essential environmental aspects to determine species diversity and community abundance. However, how soil resource availability and heterogeneity determine species diversity and community abundance in highly heterogeneous and most fragile karst landscapes is largely unknown. We examined the effects of soil resource availability and heterogeneity on plant community composition and quantified their relative contribution by variation partitioning. Then, a structural equation model (SEM) was used to further disentangle the multiple direct and indirect effects of soil resource availability on plant community composition. Species diversity was significantly influenced by the soil resource availability in shrubland and woodland but not by the heterogeneity in woodland. Abundance was significantly affected by both soil resource availability and heterogeneity, whereas variation partitioning results showed that soil resource availability explained the majority of the variance in abundance, and the contribution of soil resource heterogeneity was marginal. These results indicated that soil resource availability plays a more important role in determining karst plant community composition than soil resource heterogeneity. Our SEMs further found that the multiple direct and indirect processes of soil resource availability in determining karst species diversity and abundance were different in different vegetation types. Soil resource availability and heterogeneity both played a certain role in determining karst plant community composition, while the importance of soil resource availability far exceeded soil resource heterogeneity. We propose that steering community restoration and reconstruction should be highly dependent on soil resource availability, and multiple direct and indirect pathways of soil resource availability for structuring karst plant communities need to be taken into account.

[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.

Passive air sampling of DDT, chlordane and HCB in the Pearl River Delta, South China: implications to regional sources.

The Pearl River Delta (PRD) is one of the largest fast-developing economic zones in China. Hong Kong and the mainland part of the PRD differed in socio-economic development history and chemical management policies. Polyurethane foam (PUF)-passive air sampling (PAS) was deployed at 21 regional air quality monitoring stations across the PRD in summer and winter, respectively. Dichloro-diphenyl-trichloroethane (DDT), chlordane and hexachlorobenzene (HCB) were analyzed with GC-MS. High total DDT (240-3700 pg m(-3)) and chlordane (100-2600 pg m(-3)) concentrations were observed. Concentrations of DDTs and chlordane were higher in summer than winter; HCB vice versa. Spatially, the mainland part of the PRD generally displayed higher DDT concentrations than Hong Kong. Antifouling paint for fishing ships in coastal China was suggested to be an important current DDT source in the coast. The reason is unknown for the very low trans-/cis-chlordane (TC/CC) ratios (0.27) found in the mainland in winter. HCB concentrations were relatively uniform across the PRD, and long range transport of HCB from inland/North China to the PRD in winter was suggested.