Aerosol sampling for micro-spectroscopic single particle analysis and single particle soot
photometry (SP2) on board of the HALO aircraft during ACRIDICON-CHUVA
C. Pöhlker1, M. L. Krüger1, T. Klimach1, B. Nillius1, Y. Cheng1, D. Rose2, P. Artaxo3, M. O. Andreae1, U. Pöschl1
1
Max Planck Institute for Chemistry, 55020 Mainz, Germany.
Institute for Atmospheric and Environmental Sciences, Goethe-University Frankfurt am Main, 60438 Frankfurt am
Main, Germany.
3
Institute of Physics, University of São Paulo, São Paulo 05508-900, Brazil.
2
We propose to employ a newly designed automated impaction sampler and a single particle soot photometer
(SP2) on board of the research aircraft HALO during
ACRIDICON-CHUVA. The sampler and the SP2 will be
located in the ‘CCN-Rack’, which also hosts a cloud
condensation particle counter (CCNC). Both, the SP2
and the impaction sampler will be operated in a
switchable manner at two inlets: (i) The HALO aerosol
submicrometer inlet (HASI), which provides the total
aerosol population during non-cloud periods and the
fraction of particles which have not been activated as
CCN during cloud periods. (ii) The counterflow virtual
impactor (CVI) will provide residual particles after cloud
droplet evaporation and therefore probes the cloud-active
aerosol fraction during cloud periods.
The SP2 utilizes laser-induced incandescence to
measure black carbon (BC). Based on incandescence
emission and elastic light scattering information on BC
mass concentration, BC coating and mixing morphology,
vaporization temperature, and size of the particles can be
retrieved. The scientific objective of SP2 operation on
board of HALO is to estimate the BC fraction in cloudactive aerosols and to study BC abundance and properties depending on biomass burning influence.
The scientific objective of the impaction sampling is
to complement the online characterization of (cloudactive) aerosol particles (via CCNC and SP2) by offline
techniques. The sampling schedule of the impactor will
be synchronized with the operation modes of CCNC and
SP2 with special focus on sampling during cloud episodes. The collected aerosol particles will be analysed by
different modern micro-spectroscopic techniques on single particle basis, such as scanning transmission X-ray
microscopy with near-edge X-ray absorption fine structure analysis (STXM-NEXAFS) and scanning electron
microscopy with energy dispersive X-ray spectroscopy
(SEM-EDX). STXM-NEXAFS is a synchrotron-based
technique providing nanometer-scale spatial resolution
and high chemical sensitivity of a variety of elements
and certain carbon functional groups. It is particularly
powerful in characterizing the composition of carbonaceous aerosols. It further provides information about
particle morphology and mixing state. STXM-NEXAFS
analysis on samples from a ground-based CVI-inlet has
provided initial insights into the composition and microstructure of cloud-active particles (Fig. 1).
The proposed measurements on board of HALO will
be connected to ground-based measurements of a broad
set of instrumentation (including CCNC, SP2, and sampling) in the context of the GoAmazon2014 field campaign.
Fig. 1. Example of X-ray microscopy images of ice residual
particles on samples from ground-based CVI inlet. (A) Particle
morphology on sampling substrate. (B) Carbon elemental map
showing the distribution of carbonaceous material in the same
particles.
This work will be supported by the DFG projects SPP
1294 (HALO), the Max Planck Society (MPG), and the
Max Planck Graduate Center (MPGC).