9 research outputs found
Chemical mass balance of 300 degrees C non-volatile particles at the tropospheric research site Melpitz, Germany
In the fine-particle mode (aerodynamic diameter < 1 ÎŒm) non-volatile material has been associated with black carbon (BC) and low-volatile organics and, to a lesser extent, with sea salt and mineral dust. This work analyzes non-volatile particles at the tropospheric research station Melpitz (Germany), combining experimental methods such as a mobility particle-size spectrometer (3â800 nm), a thermodenuder operating at 300 °C, a multi-angle absorption photometer (MAAP), and an aerosol mass spectrometer (AMS). The data were collected during two atmospheric field experiments in MayâJune 2008 as well as FebruaryâMarch 2009. As a basic result, we detected average non-volatile particleâvolume fractions of 11 ± 3% (2008) and 17 ± 8% (2009). In both periods, BC was in close linear correlation with the non-volatile fraction, but not sufficient to quantitatively explain the non-volatile particle mass concentration. Based on the assumption that BC is not altered by the heating process, the non-volatile particle mass fraction could be explained by the sum of black carbon (47% in summer, 59% in winter) and a non-volatile organic contribution estimated as part of the low-volatility oxygenated organic aerosol (LV-OOA) (53% in summer, 41% in winter); the latter was identified from AMS data by factor analysis. Our results suggest that LV-OOA was more volatile in summer (MayâJune 2008) than in winter (FebruaryâMarch 2009) which was linked to a difference in oxidation levels (lower in summer). Although carbonaceous compounds dominated the sub-ÎŒm non-volatile particle mass fraction most of the time, a cross-sensitivity to partially volatile aerosol particles of maritime origin could be seen. These marine particles could be distinguished, however from the carbonaceous particles by a characteristic particle volumeâsize distribution. The paper discusses the uncertainty of the volatility measurements and outlines the possible merits of volatility analysis as part of continuous atmospheric aerosol measurements.ISSN:1680-7375ISSN:1680-736
Chemical mass balance of 300 °C non-volatile particles at the tropospheric research site Melpitz, Germany
In the fine-particle mode (aerodynamic diameter < 1 ÎŒm) non-volatile material has been associated with black carbon (BC) and
low-volatile organics and, to a lesser extent, with sea salt and mineral
dust. This work analyzes non-volatile particles at the tropospheric research
station Melpitz (Germany), combining experimental methods such as a mobility
particle-size spectrometer (3â800 nm), a thermodenuder operating at
300 °C, a multi-angle absorption photometer (MAAP), and an aerosol
mass spectrometer (AMS). The data were collected during two atmospheric
field experiments in MayâJune 2008 as well as FebruaryâMarch 2009. As a
basic result, we detected average non-volatile particleâvolume fractions of
11 ± 3% (2008) and 17 ± 8% (2009). In both periods, BC was
in close linear correlation with the non-volatile fraction, but not
sufficient to quantitatively explain the non-volatile particle mass
concentration. Based on the assumption that BC is not altered by the heating
process, the non-volatile particle mass fraction could be explained by the
sum of black carbon (47% in summer, 59% in winter) and a non-volatile
organic contribution estimated as part of the low-volatility
oxygenated organic aerosol (LV-OOA) (53% in summer, 41% in winter);
the latter was identified from AMS data by factor analysis. Our results
suggest that LV-OOA was more volatile in summer (MayâJune 2008) than in
winter (FebruaryâMarch 2009) which was linked to a difference in oxidation
levels (lower in summer). Although carbonaceous compounds dominated the
sub-ÎŒm non-volatile particle mass fraction most of the time, a
cross-sensitivity to partially volatile aerosol particles of maritime origin
could be seen. These marine particles could be distinguished, however from
the carbonaceous particles by a characteristic particle volumeâsize
distribution. The paper discusses the uncertainty of the volatility
measurements and outlines the possible merits of volatility analysis as part
of continuous atmospheric aerosol measurements
pH and salt effects on the aggregation behaviour of star polymer with G1 polyamidoamine core and terminal amphiphilic blocks
Impacts of meteorological uncertainties on the haze formation inBeijingâTianjinâHebei (BTH) during wintertime: a case study
Optimization of acidic extraction of astaxanthin from Phaffia rhodozyma *
Optimization of a process for extracting astaxanthin from Phaffia rhodozyma by acidic method was investigated, regarding several extraction factors such as acids, organic solvents, temperature and time. Fractional factorial design, central composite design and response surface methodology were used to derive a statistically optimal model, which corresponded to the following optimal condition: concentration of lactic acid at 5.55 mol/L, ratio of ethanol to yeast dry weight at 20.25 ml/g, temperature for cell-disruption at 30 °C, and extraction time for 3 min. Under this condition, astaxanthin and the total carotenoids could be extracted in amounts of 1294.7 Όg/g and 1516.0 Όg/g, respectively. This acidic method has advantages such as high extraction efficiency, low chemical toxicity and no special requirement of instruments. Therefore, it might be a more feasible and practical method for industrial practice
Atmospheric composition change: global and regional air quality
Air quality transcends all scales with in the atmosphere from the local to the global with handovers and feedbacks at each scale interaction. Air quality has manifold effects on health, ecosystems, heritage and climate. In this review the state of scientific understanding in relation to global and regional air quality is outlined. The review discusses air quality, in terms of emissions, processing and transport of trace gases and aerosols. New insights into the characterization of both natural and anthropogenic emissions are reviewed looking at both natural (e.g. dust and lightning) as well as plant emissions. Trends in anthropogenic emissions both by region and globally are discussed as well as biomass burning emissions. In terms of chemical processing the major air quality elements of ozone, non-methane hydrocarbons, nitrogen oxides and aerosols are covered. A number of topics are presented as a way of integrating the process view into the atmospheric context; these include the atmospheric oxidation efficiency, halogen and HOx chemistry, nighttime chemistry, tropical chemistry, heat waves, megacities, biomass burning and the regional hot spot of the Mediterranean. New findings with respect to the transport of pollutants across the scales are discussed, in particular the move to quantify the impact of long-range transport on regional air quality. Gaps and research questions that remain intractable are identified. The review concludes with a focus of research and policy questions for the coming decade. In particular, the policy challenges for concerted air quality and climate change policy (co-benefit) are discussed