Atmospheric Bulk Deposition of PCDD/Fs in an Urban Area: Fluxes, Temporal Changes and Comparisons
Description
This study investigates the bulk deposition fluxes of PCDD/Fs in an urban area over four seasons. The samples were named bulk-dry and bulk-wet, respectively. Bulk-dry samples referred to no precipitation during the sampling period. The study employed a bulk deposition sampler (BDS), with bulk-dry deposition fluxes averaging 52.3 ± 23.7 pg/m²/day (4.29 ± 2.38 pg I-TEQ/m²-day). These results were higher than those of studies in the background regions due to increased pollution from anthropogenic activities. Additionally, the study estimated dry deposition velocities, with an average value of 0.25 ± 0.14 cm/s. This average value was smaller than the determined deposition velocities obtained from another sampler placed side-by-side. The difference mainly came from sampling duration and sampler characteristics. Moreover, bulk-wet deposition fluxes were evaluated separately, with particulate and dissolved phase deposition rates averaging 63.3 ± 16.8 pg/m²-day and 67.7 ± 9.7 pg/m²-day, respectively. Based on our search, the dissolved and particulate phases were evaluated separately in bulk samples for the first time. The collected rainwater samples were analyzed, and washout ratios were calculated. The results were different from the results obtained using a wet deposition sampler. In conclusion, the bulk results gave rough values rather than exact ones. However, BDSs have no energy necessity, are easy to use, and inexpensive. Seasonal variations in deposition fluxes were also observed, with higher fluxes recorded during colder months, attributed to increased emissions from incomplete combustion. The study also examined the compound profiles of PCDD/Fs, revealing that OCDD is the most prevalent congener in both bulk-dry and bulk-wet depositions.
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2. Materials and Methods 2.1. Sampling procedure This study was carried out in Bursa, a major metropolitan area with the fourth-highest population in Türkiye, home to a diverse range of industries such as paint, car, glass, cement, automotive, pharmaceuticals, food, and textile production. Ambient air and bulk deposition samplings were conducted from a 2.5 m high platform at a point located at 40°11′54.05″N-29°2′55.35″E in Bursa, where there is heavy traffic, commercial enterprises, and residential areas. Detailed information regarding the sampling site was in (Gülegen et al., 2024b, 2024a). As a sampler, we used a 60 cm diameter pot made of stainless steel with a 20 cm wide rim to prevent turbulence (Birgül and Tasdemir, 2012; Eker and Tasdemir, 2018), as presented in Fig. 1. The sampling collection period spanned from October 2022 to July 2023, and meteorological information was sourced from the Meteorology General Directorate (Table SM1). Bulk deposition sampling continued for eight months, during which the PCDD/Fs deposited on the stainless-steel pot were analyzed. Sample collection process: The accumulated dust on the sampling device was meticulously removed using a paper towel and submerged in sealed glass containers filled with an acetone/ n-hexane (ACE/HEX) solution when it was a dry sample. On the other hand, when rainwater was collected on the sampler, it underwent filtration using a Whatman-UK glass fiber filter. Subsequently, the filtered water was passed through a XAD-2 resin column. This process was completed rapidly, and the PCDD/F samples were split into dissolved and particulate states. These results were evaluated separately for particulate and dissolved phase deposition fluxes. This approach is utilized for bulk deposition for the first time because deposition samples have not been reported separately in dry (bulk without water) and wet (bulk with water) particles and dissolved phases. All details of the extraction and GC-HRMS analyses have been documented in our previous studies (Noori et al., 2024, 2025a).
Institutions
- Uludag Universitesi Muhendislik FakultesiBursa
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Funders
- Bursa Uludağ Üni̇versi̇tesi̇Bursa Province, TürkiyeGrant ID: (TUBITAK) (Project no: 121Y473) and Bursa Uludag University (BUU) (Project no: FGA-2022-1101)