CU-Boulder Center for Atmospheric Chemistry Research Environmental Chamber Facility
Last updated: 9-Jan-2016 (v4) - Contact: email@example.com
Published at: http://tinyurl.com/chamber-cu
1. Twin Environmental Chambers.
- Two separate temperature control enclosures, each housing a ~20 m3 Teflon FEP bag
- Surrounded by blacklights and visible wide-spectrum fluorescent lights on four walls (jNO2 = 0.01 s-1).
- A Teflon-coated fan can be used to rapidly mix reactants.
- The bag is flushed and filled with purified air (total hydrocarbons <5 ppbv and ~0.1% RH) from a pure air system (AADCO), with a maximum flow rate of 500 lpm
- Reactions are conducted at ambient pressure (~820 mbar) and controllable temperature (4-40 oC, higher temperatures can be reached with less precise control).
- RH can be adjusted between less than 0.5% (<100 ppm H2O) and ~85% by passing the supply air over a heated humidifier.
- Ozone concentrations >100 ppm are generated with a BMT 802N ozone generator.
- Chamber state and select chemical data (e.g., T, RH, P, UV/Vis irradiation, gas analyzers) are automatically recorded and controlled via a programable centralized data collection/control system using the MICAS-X platform in Labview (http://www.originalcode.com/MICASX.html; http://www.originalcode.com/MICAS-X_Customer_Experience.html).
2. Basic Measurements
- NO & NOx: 42i-TL NO-NO2-NOx Thermo Environmental Instruments
- O3: 49i Thermo Environmental Instruments
- CO, CO2, CH4, and H2O by Picarro G2401
- SO2: 43i Thermo Environmental Instruments
- H2O: LI-COR LI-840A H2O/CO2 monitor, and
- Temperature and RH: Vaisala probes (HM110, HMP60).
- Particle size distributions: TSI 3936L Scanning Mobility Particle Sizer (SMPS). Aerosol number, surface area, volume, and mass (using measured or estimated particle density) concentrations can be calculated from these measurements.
- Total Particle Concentrations (>3nm): TSI 3776 Ultrafine Condensation Particle Counter (UCPC)
- Total HC/CH4 (55i) analyzer (Thermo)
- Thermo multi-gas calibrator (146i)
- Ocean Optics spectrometer (USB4000)
- Vis (Extech, 407026)
- UV (Sper Scientific, 850009) light meters
3. Basic Experimental Procedures
- Inorganic Seed Particles. Depending on seed particle requirements (miscible with organics, non-reactive, acidic), seed particles can be ammonium sulfate or other inorganic salts, generated with an atomizer + dryer set up.
- Organic Seed Particles. Organic seeds can be dioctyl sebacate (DOS), oleic acid, or polyethylene glycol (PEG). These organic species have low volatility and facilitate condensation and so reduce loss of gases to the walls (Matsunaga and Ziemann, 2010) and they can be monitored in real-time by particle mass spectrometry to quantify SOA loss to the walls. These particles will be generated using an evaporation-condensation apparatus in which the liquid is evaporated from a hot glass bulb into a N2 stream and flushed into the chamber where particles form by homogeneous nucleation. The size distribution is narrow with peak diameter ~0.2 µm.
- OH• radicals can be generated in the presence of NOx by photolysis of methyl nitrite/NO mixtures (Atkinson et al., 1981). NO suppresses the formation of O3 and NO3 radicals. OH radicals can be generated in the absence of NOx by photolysis of H2O2 (Kroll et al., 2006), or alternatively by reacting 2-methyl-2-butene (2M2B) with O3 (Atkinson et al., 2008), which forms OH radicals with a yield ~1 (Atkinson, 1997). Methanol, which reacts with OH radicals to form HO2• with unity yield (Seinfeld and Pandis, 1998) can also be added to the reaction system to increase the HO2•/RO2• ratio.
- Most organic compounds to be used and H2O2 are liquid or solid at 25oC and can be added to the chamber by evaporating and flushing measured amounts from a glass bulb (heated if necessary) using N2. Glass bulbs containing known amounts of gaseous methyl nitrite (CH3ONO), NO, and O3 can be prepared on a glass vacuum rack with amounts determined from the pressure, temperature, and bulb volume, and flushed into the chamber using N2. Methyl nitrite is synthesized (Taylor et al., 1980) and stored in a lecture bottle, whereas NO can be obtained from a commercially available gas cylinder and O3 from an ozone generator (Ozone Engineering LG-7 or Osti 802N). Alkenes, cycloalkenes, alkanes, aromatics, terpenes, and isoprene precursors are commercially available in high purity, and for a wide selection of carbon numbers (about C8–C17) and isomers. Key products that are not available commercially can be synthesized as the Ziemann lab has often done in the past.
- Protocol and Conditions. In a typical experiment the chamber will be filled with clean air at the desired RH and then seed particles, VOC, and oxidant precursor(s) will be added. Initial concentrations will be about 10–100 µg m-3 seed particles and VOC, and either methyl nitrite/NO, H2O2, or O3. The blacklights will then be turned on to initiate OH radical formation by photolysis, or 2M2B will be added in the presence of O3 to initiate OH radical formation for low NOx alkane or aromatics reactions. SOA usually forms within a few minutes. The extent of reaction will be determined by precursor concentrations and blacklight exposure. Average OH radical concentrations will be about 2 × 106–2 × 107 cm−3 over a few hours, sufficient to form about 1–3 generations of reaction products. Gas and particle chemical composition and particle size distributions will be analyzed using real-time and offline methods.
Source Room. A state-of-art “source room” (Fig. 9) is adjacent to one chamber where biomass can be combusted with most of the smoke vented through a large ceiling-mounted fume hood and a small flow rapidly drawn via a Dekati Diluter through a port and into the chamber enclosure and reaction bag (or alternatively a large duct).
CU Environmental Chamber Facility Infrastructure: The facility occupies 8500 sq.ft. of laboratory, office and storage space on the CU main campus. In addition to the 4 environmental chambers and source room (described above) and supporting instrumentation for online and offline gas and particle analysis (described below), the CU Environmental Chamber Facility is fully equipped with a comprehensive infrastructure to support large-scale collaborative campaigns including: a dedicated cylinder room, 6 fume hoods for sample preparation (one with a vacuum rack for gas injection preparation), 6 vented chemical storage cabinets, several stationary and 3 mobile lab benches, an overhead network of cable trays for tubing/cables, 50 house vacuum ports, 50 UHP N2 ports, 50 compressed air / pure air ports, 50 exhaust ports, 70 x 120V/20A/60Hz circuits, and 6 x 208V/20-30A/60Hz circuits. The gases, exhaust, and vacuum ports are distributed throughout the laboratory mostly overhead in groups every ~2 m. 25 of the 120V circuits and 4 of the 208V circuits are distributed by a busbar with 6 m cable drops for re-configurable distribution. Each of the temperature-controlled rooms surrounding the large chambers have 4 plates (one on each side) equipped with 8-10 feedthroughs (0.64-2.54 cm) to run sampling/injection lines between the lab and Teflon bag. An additional port for each large chamber is located on the ceiling, allowing sampling by instruments in the laboratory on the 4th floor above (via ~7 cm diameter bore hole). The two smaller chambers have ~10 sampling and injection ports (0.64-0.95 cm diameter) each on two sides directly fixed to the Teflon bag. The larger chambers can accommodate 1-2 AMS-sized instruments (or several small instruments; 3 x 120V/20A circuits) inside the temperature-controlled enclosure although personnel access may be limited during some experiments. The outsides of the large chambers are outfitted with unistrut for attaching gas cylinders, sampling lines, and cables. For the large chambers, a central control and data-logging system (programmed in Labview) controls/logs the UV/visible lights, enclosure temperature control, pure air and humidity-control system, ozone generator and ancillary gas analyzers. While the layouts are designed to allow sampling by multiple instruments from the same chamber at one time, total surrounding floor space, power, access and distance from sampling ports, and amount of sampling air drawn from the reaction chamber can impose practical limits, depending on the type of experiment and instrumentation; thus, careful planning is required for large-scale / multi-instrument campaigns.
Physical Layout of the Chamber Lab
Chamber 2 (“White Chamber” - West, “1W”):
1W- South 1W- West
1W- North 1W- East
Chamber 1 (“Brown Chamber” - East, “2B”):
2B- West 2B- North
2B - East 2B - additional east port in source room
Synchronized Overhead Drops throughout lab (~30 each on 3rd floor?):
UHP Liquid N2 (30 psi), Compressed or Purified Air (90/30psi), Vacuum (~80-260mb), Exhaust
Overhead busbar with 20-foot drops (20A/120V, 4 plugs, GFI-protected)
# of total 20A circuits in entire lab?
Between Chamber - Control center/Gas Analyzers
(conduit to greenhouse also shown below)
Cylinder/Liquid Nitrogen Room:
2 Fume hoods across from chambers (1dedicated to gas injection rack):
Guest Work Stations (5 on 3rd floor, 4 on 4th floor):
(Add pics of other ones + better one of this one)
Conference Rooms (Projectors and white boards):
Large conference room Small conference room
Small conference room
Additional things to add: