科研成果 by Year: 2013

Brominated flame retardants (BFRs) such as polybrominated diphenyl ethers (PBDEs) are important pollutants, yet few data on ambient BFRs levels have been available for North China, one of the most developed regions of the country. In this study, we investigated levels and spatial distributions of BFRs based on gridded field observations coupled with passive air sampling in the aforementioned region. A model incorporating both point and nonpoint sources was developed to simulate the spatial distribution and to achieve source apportionment. Although high concentration was observed at an electronic-waste (e-waste) recycling site, the median level of the sum of tri-, tetra-, hepta-, hexa-, and hepta-PBDEs (Sigma 10PBDEs) was 0.56 ng/sample, which was lower than those observed previously in mainland China. Source apportionment revealed that nonpoint emissions contributed nearly 78% of Sigma 10PBDEs observed in this study. In contrast, high levels of BDE-209 and DBDPE were observed, with median concentrations of 4.0 and 10.2 ng/sample, respectively. Point sources located in the region around Laizhou Bay, Shandong Province were the major sources, which contributed 31% of BDE-209 and 70% of DBDPE observed in this study, indicating that this manufacturing base was the most important source region for atmospheric deca-BFRs in North China. To our knowledge, this is the first study to report source apportionment of atmospheric BFRs based on gridded field observations.

Atmospheric aging appears to alter physical and chemical properties of mineral dust aerosol and thus its role as reactive surface in the troposphere. Yet, previous studies in the atmosphere have mainly focused on the pristine surfaces of mineral dust aerosol, and the reactivity of aged mineral dust toward atmospheric trace gases is poorly recognized. This work presents the first laboratory investigation of heterogeneous reactions of gaseous hydrogen peroxide (H2O2), an important atmospheric oxidant, on the surfaces of HNO3 and SO2-processed calcium carbonate particles as surrogates of atmospheric mineral dust aged by acidic trace gases. It is found that the processing of the calcium carbonate particles with HNO3 and SO2 has a strong impact on their reactivity toward H2O2. On HNO3-processed particles, the presence of nitrate acts to either decrease or increase H2O2 uptake, greatly depending on RH and surface coverage of nitrate. On SO2-processed particles, the presence of surface sulfite appears to enhance the intrinsic reactivity of the mineral particles due to its affinity for H2O2, and the uptake of H2O2 increases significantly relative to the pristine particles, in particular at high RH. The mechanisms for heterogeneous reactions of H2O2 with these processed particles are discussed, as well as their potential implications on tropospheric chemistry. The results of our study suggest that the reactivity of mineral dust aerosol toward H2O2 and maybe other trace gases is markedly dependent on the chemical composition and coverage of the coatings as well as ambient RH, and thus will vary considerably in different polluted air masses.

Volatile organic compounds (VOCs) are of central importance in the atmosphere because of their close relation to air quality and climate change. As a significant sink for VOCs, the fate of VOCs via heterogeneous reactions may explain the big gap between field and model studies. These reactions play as yet unclear but potentially crucial role in atmospheric processes. In order to better evaluate this reaction pathway, we present the first specific review for the progress of heterogeneous reaction studies on VOCs, including carbonyl compounds, organic acids, alcohols, and so on. Our review focuses on the processes for heterogeneous reactions of VOCs under varying experimental conditions, as well as their implications for trace gas and HOx budget, secondary organic aerosol (SOA) formation, physicochemical properties of aerosols, and human health. Finally, we propose the future direction for laboratory studies of heterogeneous chemistry of VOCs that should be carried out under more atmospherically relevant conditions, with a special emphasis on the effects of relative humidity and illumination, the multicomponent reaction systems, and reactivity of aged and authentic particles. In particular, more reliable uptake coefficients, based on the abundant elaborate laboratory studies, appropriate calibration, and logical choice criterion, are urgently required in atmospheric models.