Prediction of vapor pressures, boiling points and enthalpies of fusion for twenty-nine halogenated dibenzo-p-dioxins and fifty-five dibenzofurans by a vapor pressure correlation method

The characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and the variation of the gas-particle partitioning of PCDD/Fs near two municipal solid waste incinerators (MSWIs) located in southern Taiwan were investigated. In order to better understand the mechanism of dry deposition, the atmospheric dry deposition flux and velocity of PCDD/Fs were calculated. It was found that the mean atmospheric PCDD/F concentrations (0.0386-0.106 pg I-TEQ/Nm 3 ) were comparable to those detected in the vicinity of MSWIs in Taiwan, but significantly lower than those in a highly industrialized urban area (0.15 pg I-TEQ/Nm 3 ) located in southern Taiwan. The relatively higher atmospheric PCDD/F concentrations was found in winter than in summer, probably because of several loss process including photolysis, chemical reactivity, wet and dry deposition, and scavenging by vegetation. The calculated total dry deposition flux of PCDD/Fs ranged from 0.0274-0.718 ng I-TEQ/m 2 -month, and the atmospheric deposition flux in winter tended to be higher than those in summer. The results also indicated that dry deposition velocities of atmospheric particles for each month ranged from 0.52-0.91 cm/s (mean = 0.63 cm/s) and 0.48-0.73 cm/s (mean = 0.55 cm/s) in sites A and B, respectively, which were similar to that for the ambient air near two MSWIs in Taiwan, but slightly higher than those in urban area of Korea. In addition, the dry deposition of PCDD/Fs was mainly contributed by particle-phase at both sampling areas during the estimated period. The above results demonstrated that the dominant mechanism of dry deposition was particle phase deposition.

Section: Gas-particle Partitioning Of Pcdd/fssupporting

confidence: 82%

Characterization of Atmospheric Dry Deposition of Polychlorinated Dibenzo-p-dioxins/Dibenzofuran in a Rural Area of Taiwan

Huang

Chen

Lai

et al. 2011

“…According to the results of contribution fraction of particle phase, the PCDD/F and PCB congeners with higher chlorine numbers occupied a higher particle fraction. Compare the particulate fraction of PCDDs and PCDFs, PCDD homologues is apt to attaching to particles than the equivalent PCDFs, which might owing to the vapor pressure of PCDFs are slightly less than PCDDs (Rordorf, 1989). Comparable results can also be found in previous studies (Lohmann and Jones, 1998;Chao et al, 2004;Lin et al, 2010a).…”

Section: Gas-particle Partitioningsupporting

confidence: 76%

Atmospheric Deposition Modeling of Polychlorinated Dibenzo-p-dioxins, Dibenzofurans and Polychlorinated Biphenyls in the Ambient Air of Southern Taiwan. Part I. Dry Depositions

Tseng

Hsieh

et al. 2014

Atmospheric deposition, including dry and wet deposition, is a primary pathway for the transfer of POPs to terrestrial and aquatic ecosystems. In this study (that is, the part I.), the characteristics of PCDD/Fs and PCBs in the ambient air of Tainan City were simulated by the PM 10 versus PCDD/Fs concentration regression analysis, gas-particle partition modeling, and the simulation of dry deposition. Dry deposition fluxes are obtained from the combination of the PCDD/F and PCB concentrations, meteorological information, dry deposition velocities, and scavenging ratios. The dry deposition fluxes of PCDD/F-TEQ 2005 increase with decreasing temperature, while increase with a higher degree of chlorine numbers on PCDD/F homologues. In this study (that is, the part I.), the average PCDD/F dry deposition fluxes in spring, summer, fall and winter were 69.3, 28.2, 129 and 246 pg WHO-TEQ/m 2 -month during 2012, respectively. As for 2013, the average PCDD/F dry deposition fluxes in spring, summer, fall and winter were 67.0, 29.8, 102 and 377 pg WHO-TEQ/m 2 -month, respectively. The average PCB dry deposition fluxes in spring, summer, fall and winter were 2.16, 1.99, 5.70 and 11.9 pg WHO-TEQ/m 2 -month during 2012, respectively. As for 2013, the average PCB dry deposition fluxes in spring, summer, fall and winter were 2.11, 1.27, 4.49 and 8.88 pg WHO-TEQ/m 2 -month, respectively. The minimum simulated value occurred in summer, while the maximum dry deposition fluxes, which were about 4-5 times higher than the minimum values, occurred in winter. The lower values observed in summer may be caused by the atmospheric diffusion of SVOCs and high rainfall intensity.

“…It was found that the measured and simulated particulate fractions of PCDD/Fs increased as the number of chlorinated substitutes increased; the higher chlorinated congeners (particularly HCDD/F and OCDD/F) were predominant in the particle phase (Tables 4 and 5). The total PCDD was found predominantly associated with particles at all sites of both measured and simulated results, probably due to lower vapor pressures for the PCDDs (Rordorf, 1989). Additionally, the total PCDD/Fs bound to particles increased slightly with decreasing temperature, the highest level was observed in fall (average of 60.2-72.5%), while the lowest one in spring for all sites (average of 42.8-58.6%).…”

Section: Gas-particle Partitioning Of Pcdd/fs and Pcbsmentioning

confidence: 76%

Atmospheric Dry Deposition of Polychlorinated Dibenzo-p-Dioxins/Dibenzofurans (PCDD/Fs) and Polychlorinated Biphenyls (PCBs) in Southern Taiwan

Lin

et al. 2012

Dry deposition is one of the major routes by which air pollutants enter the ecosystem, and thus this study investigated the dry deposition characteristics of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) and biphenyls (PCBs) in the ambient air of industrial, urban, and rural areas in southern Taiwan from November 2010 to May 2011. Average dry deposition fluxes of total PCDD/Fs and PCBs in the ambient air of four sites were 157-544 pg/m 2 -day (8.30-27.5 pg I-TEQ/m 2 -day) and 289-1010 pg/m 2 -day (0.540-1.94 pg WHO-TEQ/m 2 -day), respectively. The results showed that particle phase depositions dominated the dry deposition processes for the removal of PCDD/Fs and PCBs from the atmosphere, and the atmospheric deposition flux in the cold season tended to be higher than that during the warm season. The dry deposition velocity of individual PCDD/Fs (0.031-0.546 cm/s) increased as the number of chlorinated substitutes increased, which were similar to those measured or predicted in other Asian countries. Similar patterns of dry deposition velocities were observed for individual PCBs (0.069-3.38 cm/s), due to the fact that low chlorinated PCBs are predominant in gas phase and have lower deposition velocities.