Emissions of polycyclic aromatic hydrocarbons from fluidized and fixed bed incinerators disposing petrochemical industrial biological sludge.

This study investigated the emissions of polycyclic aromatic hydrocarbons (PAHs) from two fluidized bed incinerators (FLBI_A and FLBI_B) and one fixed bed incinerator (FIBI) disposing biological sludge generated from the petrochemical industries in Taiwan. The results of 21 individual PAHs (including low (LM-PAHs), middle (MM-PAHs) and high molecular weight PAHs (HM-PAHs)) were reported. The LM-PAHs mainly dominated the total-PAHs in the stack flue gases, whereas the LM- and HM-PAHs dominated the total-PAHs in the bottom fly, fly ash and WSB effluent. Due to high carcinogenic potencies (=total-BaP(eq) concentrations) in the bottom ash (195 ng g(-1)) and WSB effluent (20,600 ng L(-1)) of the FIBI, cautious should be taken in treating them to avoid second contamination. Lower combustion efficiency and elevated fuel/feedstock (F/W) ratio for the FIBI led to the highest total emission factor of total-PAHs (38,400 microg kg(-1)). Lower total-PAH removal efficiencies of wet scrubber (WSB) (0.837-5.89%), cyclone (0.109-0.255%) and electrostatic precipitator (ESP) (0.032%) than those reported elsewhere resulted in high fraction in PAH contributions from the stack flue gases. Lower total-PAH emission factor was found for FLBI_A (2380 microg kg(-1) biological sludge) with higher combustion efficiency compared to those for FLBI_B (11,500 microg kg(-1)) and FIBI (38,400 microg kg(-1) biological sludge), implying that combustion efficiency plays a vital role in PAH emissions.

Human dietary exposure to polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in Taiwan.

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) levels in a total of 25 food items in Taiwan were surveyed. It was observed that shellfish and saltwater fish possessed the highest PCDD/Fs levels, 9.82 and 3.60 pg WHO-TEQ/g, respectively, on the lipid basis. The dietary intakes of humans at the ages of 12-18, 19-64, and over 65 were determined. The estimated intake were between 21.8 pg (female teenagers) and 37.6 pg (male seniors) WHO-TEQ/day; the levels varied with the dietary habits. The PCDD/F intakes for all human groups are far below the tolerable limit of 70 pg WHO-TEQ/kg b.w./month. In addition, the daily PCDD/F intake levels for duck-farmers consuming average and large amounts of PCDD/F contaminated duck eggs were examined. The result shows that consuming more than one duck egg with level higher than 10 pg WHO-TEQ/g lipid of PCDD/Fs per day could lead to a PCDD/F intake level higher than the tolerable limit. However, for normal population, there is a little risk to ingest intolerable amount of PCDD/Fs because of consuming contaminated duck eggs.

Assessment of polychlorinated dibenzo-p-dioxins and dibenzofurans contribution from different media to surrounding duck farms.

Since the "Toxic Egg Event" broke out in central Taiwan, the possible sources of the high content of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in eggs have been a serious concern. In this study, the PCDD/F contents in different media (feed, soil and ambient air) were measured. Evaluation of the impact from electric arc furnace dust treatment plant (abbreviated as EAFDT plant), which is site-specific to the "Toxic Egg Event", on the duck total-PCDD/F daily intake was conducted by both Industrial Source Complex Short Term model (ISCST) and dry and wet deposition models. After different scenario simulations, the worst case was at farm A and at 200 g feed and 5 g soil for duck intake, and the highest PCDD/F contributions from the feed, original soil and stack flue gas were 44.92, 47.81, and 6.58%, respectively. Considering different uncertainty factors, such as the flow rate variation of stack flue gas and errors from modelling and measurement, the PCDD/F contribution fraction from the stack flue gas of EAFDT plant may increase up to twice as that for the worst case (6.58%) and become 13.2%, which was still much lower than that from the total contribution fraction (86.8%) of both feed and original soil. Fly ashes contained purposely in duck feed by the farmers was a potential major source for the duck daily intake. While the impact from EAFDT plant has been proven very minor, the PCDD/F content in the feed and soil, which was contaminated by illegal fly ash landfills, requires more attention.

Atmospheric dry deposition of polychlorinated dibenzo-p-dioxins and dibenzofurans in the vicinity of municipal solid waste incinerators.

This study focuses on the atmospheric dry deposition flux of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the vicinity of the two municipal solid waste incinerators (MSWIs) located in southern Taiwan. PCDD/Fs in ambient air were taken and analyzed for seventeen 2,3,7,8-substituted PCDD/Fs during November 2004 and July 2005. Results show that the mean concentrations of PCDD/Fs in the ambient air near MSWI-GS and MSWI-RW were 0.090 and 0.097pg I-TEQ/Nm(3), respectively. Dry deposition fluxes of total PCDD/Fs were 18.0 and 23.5pg I-TEQ/(m(2)d) in the ambient air near MSWI-GS and MSWI-RW, respectively, which were considerably higher than that measured in Guangzhou, China. Annual dry deposition fluxes of total PCDD/Fs in the ambient air near MSWI-GS and MSWI-RW were 189 and 217ng/(m(2)year), respectively, which were also much higher than dry deposition of total PCDD/Fs to the Atlantic Ocean. The results of the present study strongly suggest that exposure to PCDD/Fs in this area should be reduced. In addition, parametric sensitivity shows that dry deposition flux of PCDD/Fs is most sensitive to dry deposition velocity of the particle-phase, followed by air temperature and concentration of total suspended particulate but least sensitive to dry deposition velocity of the gas-phase.

Atmospheric deposition of polychlorinated dibenzo-p-dioxins and dibenzofurans on the soils in the vicinity of municipal solid waste incinerators.

This study focuses on the atmospheric deposition of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) on the soils in the vicinity of two municipal solid waste incinerators (MSWIs), which were located in the Gangshan (GS) and the Renwu (RW) Townships of southern Taiwan. PCDD/Fs in the soils were sampled simultaneously with those in the ambient air and analyzed for 17 2,3,7,8-substituted PCDD/Fs. The results show that the mean contents of PCDD/Fs in the soils near MSWI-GS and MSWI-RW were 2.65 and 1.20 ng I-TEQ/kg dry weight, respectively. Annual wet deposition fluxes of total PCDD/Fs were 119 and 113 ng/m(2)-year in the ambient air near MSWI-GS and MSWI-RW, respectively. The results obtained in this study are much higher than those estimated for the Atlantic Ocean, where the average wet deposition was only 45 ng/m(2)-year. The annual dry deposition fluxes accounted for 58.2 and 66.7%, respectively, indicating that dry deposition was more dominant than wet deposition in the atmospheric deposition processes. The congener profiles of 17 2,3,7,8-substituted PCDD/Fs showed that OCDD dominates in the soils. The contributions of OCDD in the soils near MSWI-GS and MSWI-RW were 73.4 and 67.1%, respectively, while they were only 41.4 and 31.2% in the atmospheric deposition, respectively. These results imply that OCDD is more persistent in the environment than other congeners. The results of the present study strongly suggest that exposure to PCDD/Fs in these areas should be reduced.

Significance of biomass open burning on the levels of polychlorinated dibenzo-p-dioxins and dibenzofurans in the ambient air.

In southern Taiwan, two areas (L- and Y-) with/without biomass open burning were selected to compare the PCDD/F concentrations and their congener profiles in the ambient air. The results of this study indicate that biomass (rice straw) open burning exhibited a significant impact on the PCDD/F concentration level in the ambient air. During the biomass burning season, the total PCDD/F I-TEQ concentrations in the ambient air of L- and Y-areas were approximately 4 and 17 times higher than those without biomass open burning, respectively. When 10% mass fraction of rice straw was burned, the contribution fraction of biomass burning on annual total PCDD/F I-TEQ emission was 3.28 and 8.11% for KC County and for Taiwan, respectively; however, when the calculation was on a weekly basis, the contribution fraction of biomass burning on weekly total PCDD/F I-TEQ emission was 30.6 and 53.4% for KC County and for Taiwan, respectively. The results of this study imply that during the week of biomass burning, it appears to be the most significant source of total I-TEQ PCDD emission. The results of this research can be applied to the study of other agricultural areas.

Characterization and inventory of PCDD/F emissions from coal-fired power plants and other sources in Taiwan.

The objectives of the present study were to quantify (1) the emission factors of a variety of dioxin emission sources; (2) the overall dioxin emission inventory in Taiwan as well as in a major metropolitan (KC area); and (3) the contribution of power plants to the overall PCDD/F emission. To achieve these goals, a total of 95 flue gas samples were collected and analyzed for 17 PCDD/Fs from 20 sources to develop emission factors. The emission factor of PCDD/Fs from coal-fired power plants (0.62 microgI-TEQton(-1)) obtained in this study is considerably higher than the values reported from different countries including UK, USA, and Spain by a factor of 2-265. It means that the air pollution control devices in certain power plants need to be more efficient. The emission data showed that there is a total annual release to air of 6.1 and 95gI-TEQ from major sources in the KC area and Taiwan, respectively. The dominant sources of PCDD/Fs in the KC area are the coal-fired power plants, secondary aluminum smelting, electric arc furnaces, and open burning of rice straw, which contributed for 56%, 17%, 13%, and 3.3% to the total, respectively. However, in Taiwan, the dominant sources of PCDD/Fs are the iron ore sintering, coal-fired power plants, electric arc furnaces, and open burning of rice straw, which contributed for 32%, 28%, 23%, and 8.1% to the total, respectively. The results of this study showed that coal-fired power plants are very significant sources of PCDD/Fs and also provide an important database to assist the decision makers for formulating policies to alleviate dioxin concerns.

Emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans from various industrial sources.

This study characterized the emissions of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) from the stack flue gases of 17 industrial sources, which were classified into 10 categories. The results show that the mean PCDD/PCDF concentration of secondary zinc smelter (Zn-S) and secondary copper smelter (Cu-S) is 2.44 ng international toxic equivalent (I-TEQ)/Nm3 (N represents normal conditions at 0 degrees C, 760 mmHg), which was found to be significantly greater than that of industrial waste incinerators (mean concentration = 0.15 ng I-TEQ/Nm3). These results imply that the controlling of secondary metallurgical melting processes is more important than industrial waste incineration for the reduction of PCDD/PCDF emissions. The mean emission factors of cement production, Zn-S and Cu-S, are 0.052, 1.99, and 1.73 microg I-TEQ/t product, respectively. For industrial waste incineration, the mean emission factors of waste rubber, waste liquor, waste sludge, industrial waste solid (IWI)-1, IWI-2, IWI-3, and IWI-4 are 0.752, 0.435, 0.760, 6.64, 1.67, 2.38, and 0.094 microg I-TEQ/t feed, respectively. Most of the PCDD/PCDF emission factors established in this study are less than those reported in previous studies, which could be because of the more stringent regulations for PCDD/PCDF emissions in recent years.