Formation of polychlorinated dibenzo-p-dioxins/dibenzofurans from residual carbon on municipal solid waste incinerator fly ash using Na37Cl

Na37Cl was used to study the role of chlorine in the formation of polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) from carbon. Adding Na37Cl to fly ash showed that this compound was a (relatively) poor chloride source; chlorine naturally present on the ash - which could include both chlorine in residual carbon and (metal) chlorides - was found to be ca. 17x more reactive. When both Na37Cl and CuCl2 were added to aqueous extracted fly ash, the percentage of 37Cl from Na37Cl included in PCDD/F increased, compared to the combination of Na37Cl/fly ash. When Na37Cl and CuCl2 were exchanged in water, followed by evaporation of the solvent, and mixed with aqueous extracted fly ash, the percentage of 37Cl included in PCDD/F was much higher. Apparently, direct transfer of 37Cl from CuCl2 to carbon and PCDD/F was much faster than transfer of 37Cl- from Na37Cl via a metal chloride (such as CuCl2) to carbon and PCDD/F. In addition to chlorine in PCDD/F originating from exchanged NaCl/CuCl2, chloride left on the fly ash after aqueous extraction and chlorine present in residual carbon could also have been incorporated in PCDD/F.     

Spatial patterns of organic chlorine and chloride in Swedish forest soil

The concentration of organic carbon, organic chlorine and chloride was determined in Swedish forest soil in the southern part of Sweden and the spatial distribution of the variables were studied. The concentration of organically bound chlorine was positively correlated to the organic carbon content, which is in line with previous studies. However, the spatial distribution patterns strongly indicate that some other variable adds structure to the spatial distribution of organic chlorine. The distribution patterns for chloride strongly resembled the distribution of organic chlorine. The spatial distribution of chloride in soil depends on the deposition pattern which in turn depends on prevailing wind-direction, amount of precipitation and the distance from the sea. This suggests that the occurrence of organic chlorine in soil is influenced by the deposition of chloride or some variable that co-varies with chloride. Two clearly confined strata were found in the area: the concentrations of organic chlorine and chloride in the western area were significantly higher than in the eastern area. No such difference among the two areas was seen regarding the carbon content.     

Effects of copper chloride on formation of polychlorinated dibenzofurans in model waste incineration in a laboratory-scale fluidized-bed reactor

Combustion experiments in a laboratory-scale fluidized-bed reactor have been performed to clarify the effects of copper chloride as a catalyst on polychlorinated dibenzofurans (PCDFs) formation in municipal waste incineration. We used model wastes with and without copper chloride (CuCl2 x 2H2O) as a catalyst, both of which contained polyvinyl chloride (PVC) as a chlorine source. Combustion temperature was set to 900 degrees C, and the amount of air supplied was twice as much as the theoretical amount. The experimental setup had been carefully planned to ensure avoidance of the influences of previous experiments. Results of these present experiments revealed that copper chloride in the waste increased the amount of PCDFs formed and made the homologue profile shifted towards the highly chlorinated species. Copper chloride contributes to PCDFs formation by promoting chlorination via catalytic reactions, whereby the reaction could be important in that organic matters are chlorinated directly by chlorinated compounds related to Deacon reaction such as copper chloride. It was elucidated that characteristic isomer distribution patterns appeared in case the waste contained copper chloride. It is probable in our experiment with copper chloride that PCDFs are mainly formed via catalytic reactions of copper compounds and carbon.     

Dechlorination pathways of ortho-substituted PCBs by UV irradiation in n-hexane and their correlation to the charge distribution on carbon atom

The photodegradations of 22 individual polychlorinated biphenyl (PCB) congeners (including 21 non-coplanar ortho substituted and one non-ortho substituted) by irradiation with ultraviolet lamp in n-hexane solution were studied. Photoproducts were identified by matching their retention times and mass spectra with those of authentic standards. PCB congener with less than two chlorides was photodegraded within half an hour, if more than three chlorine on ring, the photodechlorination time for PCB needs one and half hours or more, sometimes even longer than 15 h. The half-life of PCB degradation by photodechlorination was much shorter than that by anaerobic biological dechlorination. Charge distribution on carbon atom combined with the monitoring products of individual PCB congeners were used to deduce the photodegradation pathways. The higher the charge distribution for carbon to which chlorine is attached, the easier for photodechlorination to occur. A lot of chlorine atoms attached PCB, the dechlorination was found to occur prior to the carbon with higher charge distribution at the benzene ring with more chlorine atoms attached.     

Congener group patterns of chloroparaffins in marine sediments obtained by chloride attachment chemical ionization and electron capture negative ionization

Congener group patterns of technical short chain and medium chain chloroparaffins (SCCP and MCCP) were determined by electron capture negative ionization (ECNI) and chloride attachment chemical ionization (CACI) mass spectrometry (MS). In contrast to CACI-MS, congener patterns obtained by ECNI showed always a shift to the next higher chlorinated congener and carbon chain length group. Consequently, the calculated molecular masses and chlorine contents were higher for ECNI (factor 1.10+/-0.03 and 1.09+/-0.03, respectively). ECNI/CACI ratios in sediment samples from the North and Baltic Sea were also slightly higher. However, a more pronounced shift of the congener pattern for a given carbon chain length to congeners with 2-3 more chlorine atoms was observed. SCCP and MCCP concentrations obtained by ECNI-MS were in the range of 8-63ngg(-1) (North Sea) and 22-149ngg(-1) dry weight (Baltic Sea). MCCP levels were highest in all samples (MCCP/SCCP factor 1.1-3.2).     

Chemical degradation of 2,3,7,8-TCDD by means of polyethyleneglycols in the presence of weak bases and an oxidant

A chemical method for destroying the 2,3,7,8-TCDD is reported; it provides gradual and progressive substitution of the chlorine atoms by hydrogen atoms. The dehalogenation is promoted by a mixture made up of polyethyleneglycols (high molecular weight) of a weak base (K₂ CO₃) and of an inorganic peroxide (Na₂ O₂) which begins the radical process. The organic chlorine is transformed into inorganic chloride.The reaction mixture administered to male guinea-pigs did not lead to any direct or histological effect.     

Effects of copper chloride on formation of polychlorinated dibenzo-p-dioxins in model waste incineration

Combustion experiments in a laboratory-scale fluidized-bed reactor were conducted to elucidate the effects of copper chloride as a catalyst on polychlorinated dibenzo-p-dioxins (PCDDs) formation in municipal waste incineration. We used model wastes with and without copper chloride (CuCl₂ · 2H₂O), both of which contained polyvinyl chloride as a chlorine source. Combustion temperature was set to 900 °C, and the amount of air supplied was twice the stoichiometric ratio. The experimental setup was carefully planned to suppress the influences of experimental conditions except the waste composition. Results of these experiments showed that copper chloride in the waste increased the amount of PCDDs formed and made the homologue profile to shift towards the highly chlorinated species. Copper chloride contributes to the PCDDs formation by promoting chlorination, whereby the reaction is important in that organic matter is chlorinated directly by copper compounds. Copper chloride did not exert a great influence on the isomer distribution patterns of PCDDs, while there appeared a significant difference in the case of PCDFs. This points out the difference of the major formation mechanisms between PCDDs and PCDFs. PCDDs are less formed by the catalytic reactions from carbon/polycyclic aromatic hydrocarbons than PCDFs in our experimental conditions.     

Effects of copper chloride on formation of polychlorinated dibenzo-p-dioxins in model waste incineration

Combustion experiments in a laboratory-scale fluidized-bed reactor were conducted to elucidate the effects of copper chloride as a catalyst on polychlorinated dibenzo-p-dioxins (PCDDs) formation in municipal waste incineration. We used model wastes with and without copper chloride (CuCl₂ · 2H₂O), both of which contained polyvinyl chloride as a chlorine source. Combustion temperature was set to 900 °C, and the amount of air supplied was twice the stoichiometric ratio. The experimental setup was carefully planned to suppress the influences of experimental conditions except the waste composition. Results of these experiments showed that copper chloride in the waste increased the amount of PCDDs formed and made the homologue profile to shift towards the highly chlorinated species. Copper chloride contributes to the PCDDs formation by promoting chlorination, whereby the reaction is important in that organic matter is chlorinated directly by copper compounds. Copper chloride did not exert a great influence on the isomer distribution patterns of PCDDs, while there appeared a significant difference in the case of PCDFs. This points out the difference of the major formation mechanisms between PCDDs and PCDFs. PCDDs are less formed by the catalytic reactions from carbon/polycyclic aromatic hydrocarbons than PCDFs in our experimental conditions.     

Synthesis, isolation and purification of C10-C13 polychloro-n-alkanes for use as standards in environmental analysis

Short chain (C10-C13) polychloro-n-alkanes (sPCAs) mixtures were synthesized by refluxing pure n-alkane (> 99%) with sulfuryl chloride (SO2Cl2) in the presence of UV-light (550 W). The free radical initiated reactions produced analogs containing approximately 4-9 chlorine atoms on each carbon chain. Purification of reaction products was achieved by adsorption chromatography on Florisil. The products were characterized by high-resolution gas chromatography/mass spectrometry (HRGC/MS) operated in the electron capture negative ionization (ECNI) and in electron ionization (EI) modes. Individual standards can now be combined to create standards whose profiles resemble that of environmental samples. Quantification of a known amount of the newly synthesized sPCAs mixture, using an industrial formulation as an external standard, resulted in an overestimation (approximately 28%) in its true value.     

The formation and fate of chlorinated organic substances in temperate and boreal forest soils

Background, aim and scope  Chlorine is an abundant element, commonly occurring in nature either as chloride ions or as chlorinated organic compounds (OCls). Chlorinated organic substances were long considered purely anthropogenic products; however, they are, in addition, a commonly occurring and important part of natural ecosystems. Formation of OCls may affect the degradation of soil organic matter (SOM) and thus the carbon cycle with implications for the ability of forest soils to sequester carbon, whilst the occurrence of potentially toxic OCls in groundwater aquifers is of concern with regard to water quality. It is thus important to understand the biogeochemical cycle of chlorine, both inorganic and organic, to get information about the relevant processes in the forest ecosystem and the effects on these from human activities, including forestry practices. A survey is given of processes in the soil of temperate and boreal forests, predominantly in Europe, including the participation of chlorine, and gaps in knowledge and the need for further work are discussed. Results  Chlorine is present as chloride ion and/or OCls in all compartments of temperate and boreal forest ecosystems. It contributes to the degradation of SOM, thus also affecting carbon sequestration in the forest soil. The most important source of chloride to coastal forest ecosystems is sea salt deposition, and volcanoes and coal burning can also be important sources. Locally, de-icing salt can be an important chloride input near major roads. In addition, anthropogenic sources of OCls are manifold. However, results also indicate the formation of chlorinated organics by microorganisms as an important source, together with natural abiotic formation. In fact, the soil pool of OCls seems to be a result of the balance between chlorination and degradation processes. Ecologically, organochlorines may function as antibiotics, signal substances and energy equivalents, in descending order of significance. Forest management practices can affect the chlorine cycle, although little is at present known about how. Discussion  The present data on the apparently considerable size of the pool of OCls indicate its importance for the functioning of the forest soil system and its stability, but factors controlling their formation, degradation and transport are not clearly understood. It would be useful to estimate the significance and rates of key processes to be able to judge the importance of OCls in SOM and litter degradation. Effects of forest management processes affecting SOM and chloride deposition are likely to affect OCls as well. Further standardisation and harmonisation of sampling and analytical procedures is necessary. Conclusions and perspectives  More work is necessary in order to understand and, if necessary, develop strategies for mitigating the environmental impact of OCls in temperate and boreal forest soils. This includes both intensified research, especially to understand the key processes of formation and degradation of chlorinated compounds, and monitoring of the substances in question in forest ecosystems. It is also important to understand the effect of various forest management techniques on OCls, as management can be used to produce desired effects.     

UV-light induced mineralization of organic matter bound chlorine in Lake Bjän,Sweden--a laboratory study

Surface water and aqueous solutions of isolated organic matter from a humic rich lake in southern Sweden were exposed to artificial UV radiation to investigate the UV light induced influence on organic matter bound chlorine in natural systems. It was found that the photodegradation of organic matter bound chlorine was more pronounced than the photodegradation of organic carbon. After 120 h of irradiation of the isolated organic matter, only 35% of the initial organochlorine was still in the solution compared to about 70% of the dissolved organic carbon (DOC). A similar result was obtained for unfractionated surface water. Furthermore, our results indicate that the loss of organic chlorine was mainly due to a mineralization of organic chlorine into chloride ions. The total decrease of organic chlorine after 120 h was 32 microg Cl(org) l(-1), of which the major part disappeared in the initial irradiation phase. A similar increase was observed in the chloride concentration (34 microg Cl(-) l(-1)).     

Formation of dioxins (PCDDs/PCDFs) by dioxin-free fly ash as a catalyst and relation with several chlorine-sources

Simplified thermal formation experiments have been conducted using dioxin-free fly ash as a catalyst with many kinds of combustible samples such as newspaper, kerosene, paraffin, PE (polyethylene), PP (polypropylene) and PVC. Chlorine sources were PVC, NaCl and HCl. The combustion of samples containing chlorine in the absence of dioxin-free fly ash produced dioxins at a low level although HCl was present in the gas stream. On the other hand, the combustion of samples without chlorine with dioxin-free fly ash increased dioxins formation to a level around 10 times higher than that upon heating dioxin-free fly ash alone. This result is considered to be due to the presence of metal chloride in the fly ash and hydrocarbons in the gas stream. The combustion of samples containing either an organic or inorganic chlorine source or using a HCl stream with dioxin-free fly ash increased dioxin level dramatically.     

Chloride imbalances in soil lysimeters

The assumption that soil neither acts as a source or a sink of chloride is evaluated by incubating soil cores in lysimeters in a climate chamber under controlled conditions. Some of the lysimeters acted as a sink while others acted as a source of chloride. Considerable amounts of organic chlorine were lost by leaching. The loss by leaching of organic chlorine could only explain part of the discrepancy in the lysimeters where the soil acted as a sink and it could certainly not explain the cases where the soil acted as a source.The storage of organic chlorine was four times larger than the storage of chloride and comparably small changes in the organic chlorine storage will thus have a considerable influence on the chloride budget. However, the soil was too heterogeneous to determine whether a change in the storage had taken place or not. It is concluded that the observed chloride surplus and also, at least to some extent, the observed chloride deficit, most likely was caused by net-changes in the storage of organic chlorine in soil. An inverse correlation was found between the initial chloride content of the soil and the imbalance in the chloride budget.Dry deposition of chloride is generally assumed to equal the run-off minus the wet deposition. Extrapolation to the field situation suggests that the output of organic chlorine by soil leachate is at risk to cause an underestimation of the dry deposition by about 25%.     

Modeling heterogeneous ClNO2 formation,chloride availability,and chlorine cycling in Southeast Texas

Nitryl Chloride (ClNO₂) mixing ratios above 1 ppbv have been measured off the coast of Southeast Texas. ClNO₂ formation, the result of heterogeneous N₂O₅ uptake on chloride-containing aerosols, has a significant impact on oxidant formation for the Houston area. This work reports on the modeling of ClNO₂ formation and describes the sensitivity of ClNO₂ formation to key parameters. Model sensitivity analyses found that: (1) Chloride availability limits the formation of nitryl chloride at ground level but not aloft; (2) When excess particulate chloride was assumed to be present at ground level through sea salt, ClNO₂ concentrations increased in some locations by a factor of 13, as compared to cases where sea salt chloride was assumed to be limited; (3) Inland formation of ClNO₂ seems feasible based on chloride availability and could have a large impact on total ClNO₂ formed in the region; and (4) ClNO₂ formation is quite sensitive to the assumed yield of ClNO₂ from N₂O₅ uptake. These results demonstrate that there is a need for further field studies to better understand the geographic extent of ClNO₂ formation and the atmospheric conditions which control partitioning of chloride into the particle phase. In addition, this work examined the role of ClNO₂ in the cycling of chlorine between chloride and reactive chlorine radicals. The modeling indicated that the majority of reactive chlorine in Texas along the Gulf coast is cycled through ClNO₂, demonstrating the importance of including ClNO₂ into photochemical models for this region.     

Formation of cyanide ion or cyanogen chloride through the cleavage of aromatic rings by nitrous acid or chlorine. XI On the reaction of purine bases with hypochlorous acid in the presence of ammonium ion

Cyanogen chloride was formed by the reactions of purine bases(adenine and guanine) with hypochlorous acid in the presence of ammonium ion. The origin of the carbon and nitrogen atoms of cyanogen chloride formed from adenine was investigated by use of synthetic adenines variously labeled with the isotope of nitrogen(¹⁵N) or carbon(¹³C).     

Comparison of metastable atom bombardment and electron capture negative ionization for the analysis of polychloroalkanes

A new method for quantifying C10-C13 polychloroalkanes (PCAs or chloroparaffins, CPs) in environmental samples using metastable atom bombardment ionization (MAB) and high resolution mass spectrometry is presented. Contrary to electron capture negative ionization (ECNI), MAB can produce spectra for molecules having a low number of chlorine atoms. These molecules are present in commercial PCAs and are responsible for a large fraction of the total PCA concentration in water samples analysed. Using ECNI or MAB, no molecular ion can be seen in the spectra. ECNI spectra contain important peaks corresponding to [M-Cl]- and [M-HCl]-* while the base peak in MAB spectra is [M-Cl]+ with no [M-HCl]+* present. The mass range for C10-C13 CPs is very large and scanning the masses for all the compounds involved would lead to a loss of sensitivity. Two chromatographic analysis are thus performed using high resolution selective ion monitoring with only a limited number of masses recorded per run. To reduce analysis time, a short capillary column is used. Application of this method to the analysis of high-volumes water samples (dissolved and particulates portions separately) from the St. Lawrence river near Quebec City using MAB is presented. Contribution of molecules with a low chlorine content in the samples account for between 10% and 46% to the total concentration. Congeners distribution between the different fractions indicates that molecules with a low number of carbon atoms are preferentially retained on the particulates. Within a carbon number group, there is a slight tendency to accumulate molecules with a high number of chlorine atoms in the dissolved fraction.     

LP/LIF study of the formation and consumption of mercury (I) chloride: kinetics of mercury chlorination

The laser photolysis/laser induced fluorescence (LP/LIF) technique has been applied to studies of gas-phase mercury (Hg) chlorination. Mercury (I) chloride (HgCl) was been detected via LIF at 272 nm from reactions of elemental Hg with Cl atoms generated from the 193 nm photolysis of carbon tetrachloride. While the formation of HgCl was too fast to be observed on millisecond time scales, the kinetics of the consumption of HgCl have been determined at temperatures characteristic of post-combustion conditions. Rate coefficients and Arrhenius parameters for the reaction of HgCl with Cl2, HCl and Cl atoms were determined. The reaction of HgCl with Cl2 was the fastest reaction studied, while the reaction of HgCl with HCl was the only reaction to show any measurable temperature dependence. Estimates of the rate coefficient for the reaction Hg + Cl --> HgCl were determined using a modeling approach. Comparisons of these new measurements with model predictions are discussed.     

The effect of inorganic and organic chlorine on formation of highly chlorinated organic compounds during incineration: Laboratory pilot study

Aliphatic liquid as a basic fuel was incinerated in a laboratory scale pilot plant. Inorganic chlorine and organic chlorine mixed with basic fuel were used as additive chemicals. Sodium chloride (NaCl) and tetrachloroethylene (C₂Cl₄) were used as the sources of inorganic and organic chlorine. Combustion parameters were adjusted for optimum combustion and, consequently, the amount of particles in flue gases was low. The concentrations of chlorine in flue gases were high enough for possible formation reactions of organic chlorinated compounds in all of the chlorine input tests. An increase in chlorine input did not significantly increase the amounts of highly chlorinated organic compounds, like PCDD/Fs. The main result was that chlorophenol concentrations increased in parallel with organic chlorine input. Comparing organic chlorine to inorganic chlorine tests showed that more highly substituted PCDD/F congeners were formed when organic chlorine was the additive chlorine source. The formation of highly chlorinated organic compounds such as PCDD/Fs requires not only chlorine and aliphatic fuel to be formed, but some catalysts are also needed.     

Wastewater reuse: modeling chloroform formation

The chloroform is a substance that presents a significant risk to or via the aquatic environment. Thus, the emissions, discharges and losses of this substance need to be controlled during wastewater disinfection for reclamation and reuse purposes. Due to its carcinogenetic potential, multiple studies have been carried out on drinking and surface/natural waters but less consideration has been directed to the wastewater disinfection. The focus of this work studied the formation of chloroform during chlorination in prepared waters or artificial matrices that intended to simulate wastewaters stored in landscape ponds for green areas irrigation. The relation between reaction time, chlorine dose, and chloroform formation and the variation of the dissolved organic carbon (DOC) content during the reaction was assessed. A two-variant model was proposed to simulate breakpoint chlorination practices (when chlorine dose is equal or lower than chlorine demand) and super chlorination techniques (when chlorine dose tends to surpass chlorine demand). The model was validated by the application of actual data from working conditions of six wastewater treatment plants located in Algarve, Portugal, including other data obtained in previous research studies that were not used in the model development, and by comparing the predicted values with real measured ones.     

Analysis of polychlorinated naphthalenes in environmental samples

A method for the analysis of polychlorinated naphthalenes (PCN) has been developed. It is based on a simple clean-up procedure using activated carbon and a mass fragmentographic analysis using the negative ions formed during chemical ionization (NCI). Unlike the technical PCN products we have analyzed, a few isomerides containing four to six chlorine atoms dominate the PCN pattern in the environmental samples. The levels found in samples of biota from fresh water and marine environments in Sweden were between 3 and 62 ng PCN per gram lipid.