Carbopack c

The CMIT/MIT aerosols were generated using a spray method with a mist generator (NB2N, Sibata, Soka, Saitama, Japan) (Table 1). The aerosols were collected on the glass fiber filter (HF00025C, HYUNDAI Micro, Seoul, Korea) and sorbent tube (packed with Carbopack C, Supelco, Bellefonte, PA, USA); the CMIT/MIT were analyzed using thermal desorber (TD, TD20, Shimadzu, Kyoto, Japan)-gas chromatography (GC, GC2010, Shimadzu, Japan)-mass spectrometry (MS, GCMS-QP2010 ultra, Shimadzu, Japan) (TD-GC-MS) system. The behavioral properties of the CMIT/MIT aerosols were assessed through two experimental stages (Exp stage 1 and Exp stage 2). In Exp stage 1, the filter breakthrough test was conducted for different mass concentrations and sampling volumes of the CMIT/MIT aerosols. The boundary between particulate and gaseous behavior of the CMIT/MIT aerosols was determined depending on the occurrence of filter breakthrough. In Exp stage 2, the relative proportions of MIT and CMIT in the aerosols were assessed with different aerosol mass concentrations (Figure 1 and Table 2).

All solvents, reagents, and chromatographic sorbents used were analytical grades or above and were of suitable purity for residual analysis. Dichloromethane, n-hexane, and toluene were purchased from Honeywell (Seelze, Germany). Methanol, acetone, acetonitrile, and anhydrous sodium sulfate (Na₂SO₄) were supplied by J.T. Baker (Deventer, the Netherlands). Potassium hydroxide (86%) was obtained from Fisher Chemicals (Pittsburgh, PA, USA). Silica gel (60 Å, 35–60 mesh) and Carbopack C (60/80 mesh) were purchased from Supelco (Bellefonte, PA, USA), sulfuric acid (96%) from Carlo Erba (Rodano, Milano, Italy) and BioBeads S-X3 (200–400 mesh) from Bio-rad (Munich, Germany). All chromatographic sorbents used (acidic silica, potassium silicate, silica and Na₂SO₄) were prepared as stated elsewhere [37 ].

The present study determined BTEX concentrations (benzene, toluene, ethylbenzene, and xylene) in different seasons—winter, spring, summer, and autumn—in the main crossroad from Arad City, from January to December 2016. Every month, there were four sampling times (every time, four samples were collected simultaneously—in total, 16 samples). Sampling was carried out at the height of 2 m above ground level by using air pumps (SKC 1003, SKC Inc., Houston, TX, USA), and stainless steel tubes (10.5 cm length, 4 mm inner diameter, Supelco, Bellefonte, PA, USA) filled with a mixture 2:1:1 w/w/w, Carbotrap C: Carbopack C: Carbotrap X adsorbents (Supelco, Bellefonte, PA, USA), with a flow rate of 200 mL min⁻¹ for 60 min. Before use, tubes were conditioned for 30 min at 350 °C in a pure He flow of 50 mL min⁻¹. Four samples were collected every time, and the tubes were analyzed on the same day as the sampling. The separation and detection of the compounds were performed by GC–MS (Shimadzu 2010 plus, GCMSTQ8040, Tokyo, Japan) coupled with a thermal desorption system (Shimadzu TD20, Kyoto, Japan) as described in Kannaste et al. [35 ].
To establish correlations between BTEX and the formation of tropospheric ozone in different seasons, the ozone concentration data were taken from open access data available at http://www.anpm.ro (accessed date: 17 June 2017).