Characterization of a new smog chamber for evaluating SAPRC gas-phase chemical mechanism

Suppression of anthropogenic secondary organic aerosol formation by isoprene

“…The time-dependent SOA mass concentrations and total particle number concentrations are shown in Fig. 1, which is divided into All experiments were carried out at ~35 °C, in dry conditions (RH < 10%) and in the absence of seed particles; the initial VOC concentrations were estimated from the injection amount following our previous protocol 54 ; the initial NO x concentrations were measured and comprised over 95% NO; AMS measurements were not available for ZJU095/098/178; the elemental ratios of H/C (hydrogen to carbon), O/C (oxygen to carbon) and OM/OC (organic matter to organic carbon) were calculated using the Improved-Ambient (I-A) method 59 ; all AMS-derived parameters including f 43 and f 44 (fraction of m/z = 43 or 44) were calculated using averaged data of 420−480 min.…”

“…The CAPS-ZJU (Complex Air Pollution Study-Zhejiang University) smog chamber is a 3 m 3 Teflon-FEP chamber housed in a well-controlled enclosure, with 60 controlled ultraviolet (UV) lamps providing the light source 53,54 . A total of 15 smog chamber experiments across a broad range of scenarios were performed to support the objectives of this study, with the initial concentrations of VOCs and NO x in each experiment given in Table 1.…”

“…Upon turning on the UV lights, the temperature inside the chamber increased from ~20 to ~35 °C within 2 h due to the heat released from the lights, and then stabilised at ~35 °C until the end of the experiment. All experiments had similar temperature profiles, which ensured that the experiments were comparable and repeatable 54 . The background air was supplied by a Zero Air generator (Aadco 737-15, USA).…”

“…After each experiment, the chamber was continually flushed with clean air for at least 12 h to ensure the particle number concentration below 10 cm −3 and the reactive gas concentration below 1 ppbv. More details of the chamber characterisation and experimental methods can be found in our recent publication 54 .…”

“…Then, the aerosol mass concentration was derived from the particle number size distribution. Size-dependent aerosol wall-loss correction was performed to account for the particles deposited onto the walls, following the method applied in our previous work 54 .…”