MARGA – Monitor for AeRosols and Gases in ambient Air Continuous Measurements of Aerosols and Gases 02 Ambient air quality – critical for our health and the environment For several decades, the emission of aerosols and their The chemical composition and size distributions of aeroprecursor gases has continuously increased due to growsols are highly variable and dependent on different facing populations, industrialisation and human activities. It tors such as the location, time, meteorological condihas been known for some time that elevated concentrations, contribution of specific sources and altitude. Long tions of certain species in atmospheric aerosols have a term studies of the variation in concentration and comnegative effect on human mortality/morbidity rates. In position of key components help in the understanding of addition to human health concerns, aerosols also affect the dynamics of air pollution and lead to ways of improvatmospheric processes, having an impact on air quality, ing air quality to the benefit of our health and the envivisibility, cloud formation and rainfall. Aerosols can influronment. ence the climate directly by absorbing and scattering light, thus changing the Earth’s reflectivity or they can affect the climate indirectly via cloud formation and chang ing the property of clouds. Ambient air monitoring with MARGA quantifying aerosols and gases simultaneously When considering the effects of aerosols on health and MARGA (Monitor for AeRosols and Gases in ambient 03 the environment, it is necessary to understand how they Air) has been developed by Metrohm Applikon in coopeare formed and how their concentration and composiration with the Energy Research Centre of the Netherlands. tion vary with diurnal and seasonal cycles. Continuous The instrument offers a new approach in which gases measurements of aerosols and their precursor gases are and aerosols sampled from the same air mass are separequired with sufficient time resolution so that the varirated from each other by selectively dissolving them in ous processes can be elucidated. water. The resulting solutions are then analysed using ion chromatography with conductivity detection. Separating the two fractions from each other, allows the detection of important precursor gases and ionic species found in the aerosols. Gases HCl, HNO , HNO , SO , NH 3 2 2 3 Aerosols Cl–, NO –, SO 2–, NH +, Na+, K+, Ca2+, Mg2+ 3 4 4 Top shelf: Sample Box – separates and collects soluble gases and aerosols in solution. Eluents for chromatographs. Middle shelf: Syringe pumps for collecting sample solutions, Metrohm ion chromatographs for anion and cation analysis and human interface. Bottom shelf: UPS, additional liquid reservoirs and air flow control box (FCB). MARGA – the concept 04 Air to be analysed enters into the Sample Box via an ap ­ The liquid samples from the WRD and SJAC are continupropriate inlet, typically with a cut­off of PM or PM ously collected during one hour by syringe pumps. After 10 2.5 (particle sizes less than 10 μm or 2.5 μm). The airflow is degassing and mixing with an internal standard (lithium maintained at a constant 1 m3/h by a mass flow conbromide), the samples are analysed by two ion chromatrolled air pump. In the Sample Box water­soluble gases tographs for determination of anions and cations, resare quantitatively absorbed in a dilute (10 mg/L) solution pec tively. of hydrogen peroxide by using a wet rotating denuder (WRD). Aerosols pass through the WRD and are subse­ The bottom shelf accommodates various liquid containquently collected in a steam­jet aerosol collector (SJAC). ers, an uninterruptable power supply and flow control box. The entire instrument is controlled by a single software that runs on an integrated industrial PC. Key Features • Simultaneous measurements of gases and aerosols • High temporal resolution – results every hour from same air mass • High sensitivity for key parameters • Unattended online operation • Single software controls instrument and processes data • Continuous calibration with internal standard • All results validated by automated checks • Results flagged with user­readable comments • Detailed system diagnostics always available • Results and all operation details recorded in easily accessible form • Remote control and access of results possible • Automated restart in case of temporary line power failure 05 Schematic diagram of air and liquid flow in the MARGA MARGA is available with one or two Sample Boxes, the latter offering the possibility to distinguish between different size particulate matter in the same air mass (comparing PM and PM 2.5 10 for example) or to make gradient studies at the same location with inlets of variable heights. Gas and aerosol sampling from the same air mass 06 MARGA determines anions and cations in an aerosol and a gas sample taken from the same air mass every hour. Wet Rotating Denuder (WRD) Steam-Jet Aerosol Collector (SJAC) The WRD consists of two concentric glass tubes, forming After the WRD, the ambient air, stripped of its gaseous an annulus constantly fed with dilute H O solution. water soluble components, enters the SJAC. Here super­ 2 2 These tubes rotate at 30 revolutions per min, forming a saturated steam is introduced causing the aerosols to continuous liquid film on the inside of the outer cylinder grow into larger, heavier droplets due to the process of and the outside of the inner cylinder. Ambient air is deliquescence. Further on the air passes through a glass drawn in and, due to high diffusion coefficients, close to spiral tube, which acts as an impactor, breaking up the 100% of acid gases and ammonia are stripped from the particles by inertial separation. The resulting solution of air mass. The resulting solution of gases is continuously dissolved ionic aerosol species collects at the bottom of sampled by the Detector Box. Due to the design creating the SJAC which is then continuously sampled by the laminar flow and also the velocity of the air within the Detector Box. annulus, aerosols and particulates pass through to the SJAC. Gases dissolve in liquid film because of high diffusion rates. Steam generator Absorbance solution Air from denuder Supersaturated steam To air pump Aerosols pass through the WRD. Liquid level sensor Additional absorbance Working principle of WRD and SJAC Sample to syringe solution. Automated analysis 24/7 07 Detector Box The Detector Box is fitted with two sets of alternating At the heart of the Detector Box are two Metrohm ion syringe pumps. Every hour, one pair of syringe pumps chromatographs, fitted with conductivity detectors. The collect 25 mL of absorbance liquid each from the WRD samples in the filled sample loops are injected into cation (the gas sample) and the SJAC (the aerosol sample). Each and anion IC columns supported in a column oven. The syringe then contains a sample of gases and aerosols addition of internal standard to the WRD and SJAC samaveraged over the one hour period. At the same time ples makes anion and cation IC data validation possible. 2.5 mL of LiBr internal standard is drawn in, ready to be It also allows for the retention times to be kept stable mixed with the samples before they are injected into the over long periods by comparing the relative retention ion chromatographs. At the end of the hour the direction times of Br– and SO 2– and adjusting the column tem4 of the syringe pumps is reversed and the samples are perature appropriately. The timing of the analytical cycle passed to the sample loops of the ion chromatographs is tightly controlled so that the anions and cations from after first being degassed and mixed with the internal both the aerosol and gas sample can be analysed within standard. Meanwhile the second set of syringe pumps each hour or in the case of the two Sample Box version, are being filled with the next hour’s sample. two gas and aerosol samples within each hour. A precon centration column can be added before the ion chromatographs in case lower detection limits are re quired. Cation and anion chromatographs, with column oven and Syringe block for collecting gas and aerosol samples. conductivity detectors. Software for full control and visibility The MARGA software automatically opens when the 08 toggled with the operations details screen shown below. instrument is switched on. The software allows for full The operations details screen allows for a complete overcon trol of the system from the industrial PC that acts as view of the instrument operation at a single glance. The the human interface. The result graph screen shows up graphs can be zoomed for easy examination of de tails. to one month’s results for gases or aerosols and can be Result panel Raw data panel The results panel provides an overview of the measured The raw data panel provides an overview of all the gases, aerosols and internal standards. im portant raw data parameters. Air and liquid concentrations panel Anion and cation chromatogram panel This panel displays up to the last 4 weeks of air and The anion and cation panel displays the anion and liquid concentrations. For each analysis a new line is cation ion chromatograms. These can either be shown crea ted in the table. Coloured flags indicate the validity live or the user can page through previous results. Re of each result. ten tion times of integrated peaks are also displayed. The taskbar at the bottom of the screen allows the ac ­ Data can be conveniently exported in .xml format, as cess to all the different functions, parameters and conwell as status flags and log entries. trols, while at the very bottom information is displayed on the current status of the instrument. Monitoring trends in aerosols and gases over time Once data on gas and aerosol concentrations are export­ Coupled with backward trajectories of wind direction 09 ed from MARGA then these data can be examined and valuable deductions can be made as to the possible graphed to determine trends, both seasonal and diurnal. sources of high pollution events. Changes over time in the concentration of some gases in the ambient air in Schiedam (Netherlands), April 2012, determined by MARGA Changes over time in the ionic aerosol constituents in the ambient air in Schiedam (Netherlands), April 2012, determined by MARGA 10 MARGA installation at Auchencorth Moss, Scotland, NERC Centre for Ecology and Hydrology. All rights reserved. Ian Leith. 2011. Watch a video of a MARGA system operated by the Institute of Tropical and Marine Meteorology in Guangzhou, China: http://metrohm.com/com/Company/testimonials/index.html?q=9 MARGA of the German Federal Environment Agency (UBA) operating at research site Melpitz, of the MARGA installations run by USEPA at MARGA installed in the laboratory of Leibniz­Institute for Tropospheric Research (TROPOS) the USDA’s Beltsville agricultural research site the National Institute of Environmental Research, Seoul Typical detection limits with MARGA Specifications 11 Component Detection Limit Detection Limit Dimensions (rack included) fixed loop Preconc. Width 120 cm (µg/m3) (µg/m3) Height 180 cm Gas Depth 60 cm Weight 200 kg HCl 0.01 0.001 HNO3 0.05 0.005 Environmental conditions HNO2 0.02 0.002 Shelter temperature range 25 ± 5 °C SO2 0.03 0.003 Ambient temperature range ­30 to 45 °C NH3 0.05 0.005 Shelter humidity < 60% Aerosol Ambient humidity 0–100% Altitude Up to 2’000 m Cl– 0.01 0.001 NO – 3 0.05 0.005 Mains connection via UPS SO42– 0.04 0.004 Required voltage 115–120 V/220–230 V NH4+ 0.05 0.005 Required frequency 50/60 Hz Na + 0.05 0.005 Power consumption 700 VA K + 0.09 0.009 Dimensions and power requirements given are for the MARGA 1S. Mg 2+ 0.06 0.006 Ca 2+ 0.09 0.009 Detection limits determined on an active MARGA system in Schiedam (Netherlands) ETV Verification The U.S. EPA Environmental Technology Verification Pro gram (ETV) provides objective, third­party data to the environmental marketplace about the performance of new environmental technologies. MARGA installed in the laboratory of the National Institute of Environmental Research, Seoul The MARGA instrument from Metrohm Applikon has been verified by this program. The full report can be found at www.epa.gov/etv or at www.metrohm-applikon.com/marga.html www.epa.gov/etv Disclaimer: The EPA Environmental Technology Verification Program (ETV) Name and/or Logo does not imply approval or certification of this product, nor does it make any explicit or implied warrantees or guarantees as to product performance. Information on the performance characteristics of Metrohm Applikon ADI 2080 MARGA can be found at www.epa.gov/etv, or call Metrohm Applikon at +31 10 29 83 555 to obtain a copy of the ETV verification report. www.metrohm-applikon.com Herisau ­9100 CH G, A ohm Metr by Switzerland in printed , SWA ­06 modifications Ecknauer+Schoch to by Subject Layout 8.000.5092EN – 2013