3 research outputs found
Experimental study on the influence of dimethylamine on the detection of gas phase sulfuric acid using chemical ionization mass spectrometry (CIMS)
Based on quantum chemistry calculations it has been suggested that the quantitative detection of gas phase sulfuric acid (H_2SO_4) by use of Chemical Ionization Mass Spectrometry (CIMS) could be biased in the presence of gas phase amines such as dimethylamine (DMA). An experiment was set up at the CLOUD aerosol chamber to test the quantitative detection of H_2SO_4 by CIMS by directly comparing the measured H_2SO_4 with and without DMA being present in the sample air. It was found that the H_2SO_4 cluster distribution changes but the CIMS detection efficiency is not strongly influenced
A double inversion: Size and time resolved growth rates for aerosol particles in the CERN CLOUD experiment
An integrated analysis of multiple instruments measuring concentrations of aerosol particles in the CLOUD (Cosmics Leaving OUtdoor Droplets) chamber at CERN obtains size and time dependent growth rates. A matrix inversion is performed twice: first to get size distributions from measured concentrations using instrument transfer functions; secondly to get growth rates from size distributions using the aerosol general dynamic equation (GDE)
Nitrate Radicals Suppress Biogenic New Particle Formation from Monoterpene Oxidation
Highly
oxygenated organic molecules (HOMs) are a major
source of
new particles that affect the Earth’s climate. HOM production
from the oxidation of volatile organic compounds (VOCs) occurs during
both the day and night and can lead to new particle formation (NPF).
However, NPF involving organic vapors has been reported much more
often during the daytime than during nighttime. Here, we show that
the nitrate radicals (NO3), which arise predominantly at
night, inhibit NPF during the oxidation of monoterpenes based on three
lines of observational evidence: NPF experiments in the CLOUD (Cosmics
Leaving OUtdoor Droplets) chamber at CERN (European Organization for
Nuclear Research), radical chemistry experiments using an oxidation
flow reactor, and field observations in a wetland that occasionally
exhibits nocturnal NPF. Nitrooxy-peroxy radicals formed from NO3 chemistry suppress the production of ultralow-volatility
organic compounds (ULVOCs) responsible for biogenic NPF, which are
covalently bound peroxy radical (RO2) dimer association
products. The ULVOC yield of α-pinene in the presence of NO3 is one-fifth of that resulting from ozone chemistry alone.
Even trace amounts of NO3 radicals, at sub-parts per trillion
level, suppress the NPF rate by a factor of 4. Ambient observations
further confirm that when NO3 chemistry is involved, monoterpene
NPF is completely turned off. Our results explain the frequent absence
of nocturnal biogenic NPF in monoterpene (α-pinene)-rich environments