Background

In the atmosphere, volatile organic compounds (VOCs) and aerosols are species still of great importance for a wide range of geophysical and environmental problems varying from local issues to global scale. VOCs are key ingredients in the formation of ozone (O3) and secondary organic aerosols in polluted air, and play a significant role in determining regional air quality. Moreover, some of the VOCs emitted in the atmosphere are toxic and can have harmful effects on human health and the environment. Particulate matter (PM) mainly identified as coarse (PM10) and fine (PM2.5) modes still merit special attention. The levels of these thin aerosol particles have been under scrutiny during the past decade mainly because of their effect on health, climate and the environment in general. Aerosols in ambient air emerge from a variety of anthropogenic (transport, industrial activities, vegetation burning, etc.) and natural (volcanic eruptions, sea salt, soil dust suspension, natural forest fires, etc.) sources, which results in direct emission of PM (primary PM) and gaseous aerosols precursors (mainly SO2; NOx (NO + NO2); NH3; anthropogenic and biogenic VOCs, all producing secondary PM).

It has also been suggested that PM, and especially its fine fraction (PM2.5), leads to a wide range of acute and chronic health problems in many European Union (EU) countries. An increase of 10 μg m-3 in PM10 concentrations, as compared with its limit value set by the EU directive (20 μg m-3 annual mean), is expected to result in an increase of premature deaths by 1% up to 5% for short- and long-term exposure, respectively. This issue is particularly relevant in Romania, since this recommended value for PM2.5 is regularly exceeded in some regions. Consistently, large financial gains of the order of tens of millions Euros could also be expected in terms of health and related costs. Overall, the impact of aerosols on health may vary according to their physical (size, shape) and chemical (composition) characteristics.

There are essentially two families of precursors of secondary organic aerosols in the atmosphere: the first concerns Biogenic Volatile Organic Compounds (BVOCs) and includes the monoterpenes and the sesquiterpenes; the second consists of anthropogenic (mainly aromatic) compounds. On a global scale, BVOC emissions dominate over the anthropogenic sources, while on a regional scale, the anthropogenic emissions, which are in large part caused by the use of fossil fuels, are usually more important. The oxidation of terpenes and aromatic compounds by atmospheric oxidants leads to semi- and low-volatile products which may undergo gas/particle partitioning and form SOA. Our present scientific knowledge about SOA formation and evolution in the atmosphere clearly requires large research efforts to make progresses in the management and improvement of the air quality in urbanized countries.

OLFA-ROA project has been proposed to provide a better description of the chemical mechanisms of terpene and catechols ozonolysis from the initial steps in the gaseous phase to the formation of secondary organic aerosols in the course of the oxidation processes by using ESC-Q-UAIC chamber facilities.

The indoor ESC-Q-UAIC chamber is a closed cylindrical vessel of internal dimensions of 0.48 m diameter and 4.2 m length. The reactor volume is of 760 L and the ratio of interior surface to volume is about 8.8 m-1. This rigid reactor is made of three quartz tubes connected by flanges and is vacuum compatible. It can be operated over a range of pressure from 10-3 to 1200 mbar. The chamber body is mounted on a steel framework with help of six adjustable anti-vibrating stands in order to limit the vibration effects coming from the ground level and the pumping system. The chamber is connected to the ground to prevent any electrical charge build-up. It is closed at both ends by stainless steel flanges with appropriate insertions for reactants and bath gases inlet systems, pressure and temperature measurement units. Sampling lines made either of PTFE or stainless steel are appropriately disposed for on-line/off-line measurements of various chemical parameters (gaseous or aerosol phase products). A schematic view of the existing ESC-Q-UAIC facility chamber is presented in Figure 1.

A technical description (vacuum system, homogeneous mixing, black-light lamps and actinic lamps for irradiation, pressure, temperature and relative humidity measuring systems, FT-IR spectrometer interfaced with a multiple White path cell giving a total optical path length of (492 ± 0.2) m of the chamber can be found at the http://erris.gov.ro/cernesim.uaic.ro.

The ESC-Q-UAIC chamber is equipped with a large panel of analytical instruments dedicated to gas and particulate measurements as well as instruments for monitoring the physical parameters of the chamber (see Figure 1). However, a number of available ports provide space for the connection of other instruments which can be temporarily required to address specific scientific issues. Off and on line analyses can be achieved by using the wide range of conventional analytical equipments (http://erris.gov.ro/cernesim.uaic.ro).

Figure 1. Schematic view of the existing ESC-Q-UAIC facility.