Juhani Tarhanen

Formation of PCDDs and PCDFs in municipal waste incineration and its inhibition mechanisms: A review

The reaction mechanisms by which polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) form in municipal solid waste (MSW) incineration are reviewed. Some of the possible reaction pathways are explored in detail: e.g. high-temperature pyrosynthesis, low-temperature de novo formation from macromolecular carbon and organic or inorganic chlorine present in the fly ash matrix, and formation from different organic precursors such as chlorophenols. Although all these mechanisms have been known for a number of years, few detailed reaction mechanisms can yet be offered for PCDD/F formation from macromolecular carbon or even structurally closely related precursors. The corresponding reactions are always only minor side-reactions with low yields. This is due in particular to the extreme complexity of the fly ash matrix, which effectively obscures the identity of the active catalytic sites and the overall processes. This work discusses the production of PCDD/Fs and the interactions between transition metals and aromatic precursors in relation to the amount of PCDD/F emitted in MSW incineration. It then goes on to discuss the correlation between transition metals and PCDD/F emissions in MSW incinerators. A literature survey and some thermodynamic considerations allow conclusions to be drawn on the relations between the loading of transition metals in flue gases and particles, PCDD/F concentrations, and operating temperature. Some possible inhibition mechanisms and their thermodynamics are also discussed briefly.

Polychlorinated phenols, guaiacols and catechols in environment

Abstract Emissions, bioaccumulation and possible food chain enrichment of polychlorinated phenols, guaiacols and catechols have been studied by analyses of water, snow, ash, benthic animal, fish and bird samples in Finland. Seventeen individual compounds were analyzed using authentic reference model compounds and internal standard by GC/ECD. Although the enrichment potential of the studied compounds appeared to be lower than that of the chlorinated hydrocarbons, they proved to be very general pollutants and some of them showed specific bioaccumulation to certain species and high persistency thus forming environmental hazards.

Toxic significance of planar aromatic compounds in Baltic ecosystem — New studies on extremely toxic coplanar PCBs

Abstract Baltic salmon and white-tailed eagle samples have been analyzed for organochlorine compounds including polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, polychlorinated naphtalenes and toxic coplanar PCBs. In salmon, PCB and DDT residue contents were 0.2-0.3 ug/g in fresh muscle. Chlordanes, toxaphene, hexachlorobenzene, α-hexachlorocyclohexane and γ-hexachlorcyclohexane were found at 1 – 10 ng/g levels. Significant dioxin type of toxins found were only 2,3,7,8-tetrachlorodibenzofuran (45–81 pg/g) and 3,3′,4,4′-tetrachlorobiphenyl (638–1120 pg/g). Polychloronaphtalene contents in all salmon and eagle samples were of the same order of magnitude ranging from 4 to 85 ng/g. The highest chlorohydrocarbon contents in eagle samples were for PCB 462 ug/g, sum of the DDT residues 42 ug/g, chlordanes 5.7 ug/g and HCB 1.6 ug/g. In contrary, toxaphene, α-hexachlorocyclohexane and γ-hexachlorocyclohexane were not detected in eagles. Levels of polychlorodibenzo-p-dioxins, polychlorodibenzofurans and coplanar PCBs were highest ever reported in wildlife in adult eagle samples, in liver of a juvenile eagle and in eagle egg from South Finland ranging from 1 to 13 ng/g for PCDD/Fs and from 18 to 229 ng/g for coplanar PCBs. Calculation of the TCDD-equivalents of the contents gave that dioxin toxicity load comes in great excess from the coplanar PCBs, especially from 3,3′,4,4′,5-pentachlorobiphenyl.

Formation of hydroxylated and dimeric intermediates during oxidation of chlorinated phenols in aqueous solution

The oxidation of selected chlorophenols (2-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol and pentachlorophenol) was studied in aqueous solutions using UV/H2O2 and O3 methods. The formation of oxidation intermediates was measured to elucidate their importance in the treatment of chlorophenols. Results indicated that chlorophenols can be treated efficiently by the methods studied, but the dechlorination of the compounds was insufficient. Analysis of intermediates in the acetylated extraction fractions showed that hydroxylation of chlorophenols and formation of dimeric products were involved in the oxidation of chlorophenols in both treatment processes. The majority of the intermediates detected were transient, and thus were not detectable after an extended treatment time. The presence of a complicated mixture of intermediates suggests the need for toxicity testing to confirm the detoxifying effect of the chemical oxidation of chlorophenols.

Occurence and fate of polychlorinated aromatic ethers (PCDE, PCA, PCV, PCPA and PCBA) in environment

Abstract Analyses of aromatic chloroethers in salmon (Salmo salar), white-tailed eagle (Hailaetus albicilla) and fish liver oil have been performed by improved clean up method which separates polychlorinated diphenyl ethers (PCDEs), anisoles and veratroles (PCAs and PCVs), phenoxy anisoles and biphenyl anisoles (PCPAs and PCBAs), dioxins and dibenzofurans (PCDDs and PCDFs) to different fractions, respectively. Compounds from all these substance groups were detected and many of them identified with authentic model compounds.

Polychlorinated dibenzo-P-dioxins and -furans (PCDDs and PCDFs) in municipal waste landfill fires

Abstract Polychlorinated dibenzo-p-dioxin and dibenzofuran samples were collected from two waste landfill fires. The first fire was ignited at the experimental field built on a municipal waste landfill, and another municipal waste landfill caught fire spontaneously during the landfill fire test. Air samples were collected five meters from the center of the fire, representing diluted smoke in the breathing zone. After these fires, burnt waste samples were collected in the vicinity of the fire centers. The PCDD/PCDF concentrations in the working air during the active fire were from 51 to 427 pg(TE)/m 3 . During the fires, the acceptable daily intake value of PCDD/Fs was exceeded at both sites. The toxic congener profiles were similar to those detected in municipal solid waste incinerators. The PCDD/PCDF concentrations in the burnt waste samples at the experimental site were surprisingly low, 4–87 pg(TE)/g, but at the site of the real landfill fire the concentrations were higher, 106–290 pg(TE)/g, which is due to the slightly different waste material and conditions during the fire.

Formation of polyaromatic hydrocarbons and polychlorinated organic compounds in municipal waste landfill fires

Abstract Polyaromatic hydrocarbon and polychlorinated biphenyl concentrations were determined in the working air at two municipal landfill fires. At the fast waste site the fire was ignited intentionally, and at the other site the waste material caught fire spontaneously. Burnt waste samples, collected during the fires were analyzed for polyaromatic hydrocarbons, polychlorinated biphenyls, chlorophenols and polychlorinated benzenes. PAH and PCB concentrations in the working air were below the threshold limit values at both sites, and PAH, PCB, CP and CBz concentrations in the burnt waste samples were low. The same PAH isomers (phenanthrene, fluoranthene and pyrene) were dominant both in the air and in the waste samples at both sites. The waste material evidently affects chlorocompound. emissions, as PCB concentrations in the air and in the burnt waste samples were several orders of magnitude higher at the site of the spontaneous fire than at the experimental site.

Formation of chloroaromatics at a metal reclamation plant and efficiency of stack filter in their removal from emission

Abstract Sampling and analyses of chloroaromatic compounds emitted from the metal reclamation plant of Kuusakoski Ltd in Heinola, South Finland, were continued in order to find out formation pathways and to follow the impact of process improvements done in 1991–1992. Especially, process gas cleaning by baghouse filter at aluminum smelter plant (ALS) and by scrubber at car schredding (CSH) were successful in emission control. At ALS, reductions of polychlorinated dioxins, furans, planar PCBs and dibenzothiophenes were better that 90, naphthalenes 78, other PCBs 73, chlorobenzenes 51 and chlorophenols 43 per cent. CSH scrubber gave similar results.

Effect of catalysts and chlorine source on the formation of organic chlorinated compounds

Abstract Two series of catalyzed incineration tests were performed in a 32 kW laboratory pilot plant to study the effect of metal catalysts on the formation of chlorobenzenes, chlorophenols and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). In the first series, iron(III), tin(II) and copper(II) chlorides were added to the flame as catalysts and the combustion parameters were adjusted for optimum am[ incomplete combustion. The aim was to study the distribution of organic chlorinated compounds between particles and the gas phase in the flue gases when the combustion parameters were varied. Concentrations of particle-bound PCDD/Fs were high in the incomplete combustion tests, and those in the gas phase were still high even in the optimum combustion tests. In the second test series, copper(II), iron(III) and manganese (II) nitrates were added to the flame. Sodium chloride, representing inorganic chlorine, and tetrachloroethylene representing organic chlorine, were used as chlorine sources in the basic fuel with the different catalysts. Metals and chlorine accounted for 0.5 weight-% of the total fuel flow. The basic fuel used in these investigations was an aliphatic liquid free of aromatic hydrocarbons. Organic chlorine with the catalyst promoted the formation of particle-bound PCDD/Fs, whereas inorganic chlorine was observed to promote the formation of PCDD/Fs more effectively in the gas phase than in the particle phase. Consequently, different mechanisms of formation may be involved in the gas phase and on particle surfaces.

Tetra- and pentachlorodibenzothiophenes are formed in waste combustion

Abstract Two different waste combustion samples have been analyzed for tetra- and pentachlorodibenzothiophenes. HRGC/HRMS with a resolution of 20 000 was used for identification. By resolution of 10 000 chlorinated dibenzo-p-dioxins and some unknown compounds gave GC/SIM peaks at the exact masses of the chlorinated dibenzothiophenes. These peaks were no more present by resolution 20 000. Several tetra- and pentachlorodibenzothiophenes were found in both samples. In the other one of the samples the concentrations were seemingly high although exact quantitative determination could not be done.