科研成果

The fine particles serving as cloud condensation nuclei in pristine Amazonian rainforest air consist mostly of secondary organic aerosol. Their origin is enigmatic, however, because new particle formation in the atmosphere is not observed. Here, we show that the growth of organic aerosol particles can be initiated by potassium-salt-rich particles emitted by biota in the rainforest. These particles act as seeds for the condensation of low- or semi-volatile organic compounds from the atmospheric gas phase or multiphase oxidation of isoprene and terpenes. Our findings suggest that the primary emission of biogenic salt particles directly influences the number concentration of cloud condensation nuclei and affects the microphysics of cloud formation and precipitation over the rainforest.

A novel biodegradable polymer composed of PHBV and PLA was prepared for advanced wastewater treatment. It could serve as both biofilm carrier and carbon source for denitrification. Results of batch test showed the average denitrification rate was 0.07 mg NO3-N/(g h). The kinetic study demonstrated that when nitrate concentration was above 10.00 mg/L, DOC could not be detected in the effluent. In continuous packed-bed reactor, the average nitrogen removal efficiency was 94.11%. Nitrite concentration throughout the experiment was below 0.15 mg/L. The formation of NH4-N was observed, though small. DOC released in the effluent did not exceed 16.00 mg/L in the whole process, and it finally dropped below 1.20 mg/L. (C) 2012 Elsevier Ltd. All rights reserved.

For sustainable geologic CO2 sequestration (GCS), it is important to understand the effects of temperature and CO2 pressure on mica’s dissolution and surface morphological changes under saline hydrothermal conditions. Batch experiments were conducted with biotite (Fe-end member mica) under conditions relevant to GCS sites (35–95 °C and 75–120 atm CO2), and 1 M NaCl solution was used to mimic the brine. With increasing temperature, a transition from incongruent to congruent dissolution of biotite was observed. The dissolution activation energy based on Si release was calculated to be 52 ± 5 kJ mol–1. By comparison with N2 experiments, we showed that CO2 injection greatly enhanced biotite’s dissolution and its surface morphology evolutions, such as crack formation and detachment of newly formed fibrous illite. For biotite’s dissolution and morphological evolutions, the pH effects of CO2 were differentiated from the effects of bicarbonate complexation and CO2 intercalation. Bicarbonate complexation effects on ion release from biotite were found to be minor under our experimental conditions. On the other hand, the CO2 molecules in brine could get into the biotite interlayer and cause enhanced swelling of the biotite interlayer and hence the observed promotion of biotite surface cracking. The cracking created more reactive surface area in contact with brine and thus enhanced the later ion release from biotite. These results provide new information for understanding CO2–brine–mica interactions in saline aquifers with varied temperatures and CO2 pressures, which can be useful for GCS site selection and operations.

Radiocarbon (C-14) has become a powerful tracer in source apportionments of atmospheric carbonaceous particles. Fine particles (PM2.5) were collected at a rural site of Beijing in the summer and winter of 2007. The fractions of contemporary carbon (f(C)) in total carbon (TC) and elemental carbon (EC) are presented using C-14 measurements. This value directly represents the contemporary biogenic contribution, since recently living biomass and biogenic organic compound emissions have f(C) = 1, whereas anthropogenic emissions from fossil carbon have f(C) = 0 because the C-14 in the latter has completely decayed. The measured f(C) (TC) values range from 0.30 to 0.38 (n = 12) in winter and 0.31 to 0.44 (n = 12) in summer, respectively. The levels of f(C) values are lower than those from other rural sites in the world, indicating that the Yufa site was heavily influenced by anthropogenic emissions. The high TC concentrations in winter with the lower average f(C) (TC) suggest that coal burning for residential heating was significant contributors to the TC concentrations. The sources of contemporary carbon are primary emissions due to biomass burning, and biogenic secondary organic aerosol. Biomass burning was a dominant contributor in the winter. Fossil fuels represented 80-87% of EC in both seasons. (C) 2012 Elsevier Ltd. All rights reserved.

Radiocarbon (C-14) has become a powerful tracer in source apportionments of atmospheric carbonaceous particles. Fine particles (PM2.5) were collected at a rural site of Beijing in the summer and winter of 2007. The fractions of contemporary carbon (f(C)) in total carbon (TC) and elemental carbon (EC) are presented using C-14 measurements. This value directly represents the contemporary biogenic contribution, since recently living biomass and biogenic organic compound emissions have f(C) = 1, whereas anthropogenic emissions from fossil carbon have f(C) = 0 because the C-14 in the latter has completely decayed. The measured f(C) (TC) values range from 0.30 to 0.38 (n = 12) in winter and 0.31 to 0.44 (n = 12) in summer, respectively. The levels of f(C) values are lower than those from other rural sites in the world, indicating that the Yufa site was heavily influenced by anthropogenic emissions. The high TC concentrations in winter with the lower average f(C) (TC) suggest that coal burning for residential heating was significant contributors to the TC concentrations. The sources of contemporary carbon are primary emissions due to biomass burning, and biogenic secondary organic aerosol. Biomass burning was a dominant contributor in the winter. Fossil fuels represented 80-87% of EC in both seasons. (C) 2012 Elsevier Ltd. All rights reserved.

Radiocarbon (C-14) has become a powerful tracer in source apportionments of atmospheric carbonaceous particles. Fine particles (PM2.5) were collected at a rural site of Beijing in the summer and winter of 2007. The fractions of contemporary carbon (f(C)) in total carbon (TC) and elemental carbon (EC) are presented using C-14 measurements. This value directly represents the contemporary biogenic contribution, since recently living biomass and biogenic organic compound emissions have f(C) = 1, whereas anthropogenic emissions from fossil carbon have f(C) = 0 because the C-14 in the latter has completely decayed. The measured f(C) (TC) values range from 0.30 to 0.38 (n = 12) in winter and 0.31 to 0.44 (n = 12) in summer, respectively. The levels of f(C) values are lower than those from other rural sites in the world, indicating that the Yufa site was heavily influenced by anthropogenic emissions. The high TC concentrations in winter with the lower average f(C) (TC) suggest that coal burning for residential heating was significant contributors to the TC concentrations. The sources of contemporary carbon are primary emissions due to biomass burning, and biogenic secondary organic aerosol. Biomass burning was a dominant contributor in the winter. Fossil fuels represented 80-87% of EC in both seasons. (C) 2012 Elsevier Ltd. All rights reserved.

Polycyclic aromatic hydrocarbons (PAHs) associated with inhalable particles are harmful to human health, especially to people in urban indoor environments. To evaluate human respiratory exposure to indoor PAHs properly, respiratory deposition fluxes of size-fractioned PAHs were estimated based on size-segregated distribution of PAHs in indoor air of an urban community of Guangzhou, China. The concentrations of Sigma(16)PAH (sum of the 16 priority PAHs designated by the United States Environmental Protection Agency) were 28.9 +/- 10.0 ng/m(3), with the mean benzo(a)pyrene equivalent (BaPE) concentration at 4.1 +/- 1.6 ng/m(3). Particle size distributions of both Sigma(16)PAH and BaPE concentrations peaked in the 1.0-1.8 mu m fraction. The mean respiratory deposition flux of Sigma(16)PAH was 5.9 ng/h, and accumulation mode particles contributed 20.5-83.8% of the respiratory deposition fluxes for individual PAHs. In addition, 8.6-10.2% of inhaled Sigma(16)PAH were calculated to be deposited in the alveoli region, with accumulation particles as the largest contributor. In particular, ultrafine particles contributed 0.4-21.7% of individual PAHs deposited in the alveoli region, more than twice the fraction of the PAHs in the ultrafine particles (0.2-8.5%). Finally, lifetime cancer risk via inhalation of indoor particulate PAHs may be greater than the cancer risk guideline value (10(-6)). depending on specific assumptions used in this risk assessment. (C) 2012 Elsevier B.V. All rights reserved.