Aerosol particle chemical characteristics measured from aircraft in the lower troposphere during ACE-2

Abstract

During the Aerosol Characterization Experiment (ACE‐2), filter samples were collected aboard the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Pelican aircraft near Tenerife in June and July of 1997. The flights included constant altitude measurements in the boundary layer as well as profiles up to 3800 m providing detailed chemical information about the composition of the aerosol distribution in the lower troposphere. Three cases with different air mass origins—clean marine air, anthropogenically‐influenced air from the European continent, and dust‐laden air from the Sahara—were identified. The samples were analyzed by ion chromatography (IC) for ionic species, by combined thermal and optical analysis (TOA) for organic carbon, and by total reflection X‐ray fluorescence (TXRF) for elemental composition. Particle composition and size distributions for the range of air masses encountered illustrate links in the chemical and microphysical characteristics of aerosol from different sources. Clean marine air masses were characterized by low particle number and mass concentrations with no detectable metals, while anthropogenically‐influenced and dust‐laden air had high number, mass, and trace metal concentrations. Anthropogenic sources were characterized by high concentrations of submicron particles and some Fe and Cu, whereas dust particle loadings included a significant mass of micron‐sized particles and significant loadings of Fe, in addition to small amounts of Mn, Cu, and Ni. These results showed similar tracers for air mass origin as those found in other measurements of oceanic and continental air masses. Aerosol optical properties were estimated with a simplified model of the aerosol based on the measured compositions. The real and imaginary refractive indices and single scattering albedos differed significantly among the three types of aerosol measured, with clean marine aerosol properties showing the least absorption and dust‐containing aerosols showing the most. There were only small differences in optical properties for the two different cases of clean marine aerosol, but some significant differences between the two dust cases. Since measurement uncertainties affect these calculations, we studied the type of mixing and the fraction of absorbing species and found the calculation was sensitive to these variations only for the dust‐containing aerosol case, probably due to the small amount of water present. While the optical properties varied little with composition for clean marine and anthropogenically‐influenced cases, they showed a strong dependence on variations in particle composition and mixing state for the dust‐containing cases.

European pollution outbreaks during ACE 2: Microphysical particle properties and single‐scattering albedo inferred from multiwavelength lidar observations

“…As a consequence an enhanced share of crustal material, which possesses a rather large real part of the complex refractive index [Ishida and Price, 1996], may have been transported into the pollution plume. It is worth noting that a significant increase of the real part for dust particles compared to the one from a mixture of marine and aged-pollution particles was also found during aircraft-based observations performed in the framework of ACE 2 in the Canary Islands [Schmeling et al, 2000].…”

“…Measurements were made below 1000-m height. Wavelength-dependent complex refractive indices were calculated on the basis of chemical analysis of particles collected on board and of complex refractive indices of the identified components found in literature [Schmeling et al, 2000].…”

“…[46] The real part of the complex refractive index in the study by Schmeling et al [2000] turned out to be a little less than 1.4 for the visible wavelength range. As pointed out in section 2 the inversion provides a mean wavelength-independent value.…”

Organic Compound in Airborne Particles and their Genottoxic Effects in Mexico City

“…Knowledge of these compounds implies a better understanding of aerosol organics in atmospheric processing (Pang et al, 2006). Bulk aerosol characteristics have been measured using infrared spectroscopy, nuclear magnetic resonance, ion chromatography and aerosol mass spectrometry (Allan et al, 2003;Schmeling et al, 2000;Suzuki et al, 2001). In real-time particle mass spectrometric analysis, techniques have been developed for atmospheric measurements (Canagaratna et al, 2007).…”

Saharan dust over a central European EARLINET‐AERONET site: Combined observations with Raman lidar and Sun photometer

“…Although in situ observations at the surface give a detailed and long-term monitoring of chemical and physical characteristics these observations are not very representative of the particle conditions in the free troposphere. In situ observations with aircraft can only provide short-term monitoring during field campaigns [e.g., Ö ström and Noone, 2000; Schmeling et al, 2000;Haywood et al, 2001]. The well-known particle losses caused by the instrument inlets, in particular with respect to large mineral dust particles, may cause severe biases of derived optical properties of particles.…”