No description available.

No description available.

Durant els últims anys l'oposició de la població cap a certes activitats industrials ha augmentat considerablement, a causa de que cada dia existeix una major consciència de la població dels impactes produïts per les emissions de contaminants sobre la salut. Entre les activitats que han portat un important rebuig per la societat trobem la incineració de residus sòlids urbans, degut principalment a les seves emissions de policlorodibenzo-p-dioxines (PCDDs) i policlorodibenzofurans (PCDFs), així com de metalls pesants.L'elevada toxicitat d'aquests compostos és la que ens va portar a proposar com a objectiu del present estudi: el desenvolupament d'un model d'avaluació del risc de les emissions de dioxines i furans (per als 17 congèneres tòxics) i metalls pesants d'una planta incineradora de residus sòlids urbans.Per tal de poder assolir aquest objectiu el present estudi ha estat dividit en tres parts: 1) el desenvolupament d'un model multi-compartamental, 2) l'avaluació de l'impacte medi ambiental de les emissions de dioxines i furans i de metalls pesants a les rodalies de la planta incineradora de residus urbans de Montcada i Reixac, mitjançant una monitorització de l'àrea d'estudi, i 3) l'anàlisi de risc degut a les emissions de la planta i als nivells ambientals a l'àrea.Desenvolupament d'un model multi-compartamentalPer tal d'assolir l'objectiu de la primera part, el primer que s'ha portat a terme ha estat un estudi de la dispersió dels contaminants des de la seva sortida per xemeneia per als 17 congèneres tòxics de PCDD/Fs i per a metalls pesants. El següent pas ha estat el desenvolupament d'un model multimedia simple (aire - sòl - vegetació), que descriu el transport i transformacions de PCDD/Fs i metalls pesants als diferents medis. En el model sòl-aire s'han considerat 4 vies d'exposició dels contaminants: deposició particulada seca i humida, deposició de gasos i exposició via arrels, a més a més de les pèrdues per lixiviació, degradació, arrossegament per aigües superficials, volatilització i erosió. Per al model aire-vegetals s'han considerat les mateixes vies d'exposició. D'aquesta manera s'han determinat els nivells de contaminants en sòl i vegetació deguts a les emissions de la planta. Durant el desenvolupament d'aquest model s'ha buscat l'equilibri entre un model el qual pugui predir amb una exactitud raonable la bioacumulació de compostos químics en sòls i plantes, i un model que no requereixi una extensiva caracterització i un gran número de dades físico-químiques.Monitorització de l'àreaLa segona part de l'estudi ha estat l'avaluació de l'impacte ambiental de les emissions de dioxines i furans i de metalls pesants a les rodalies de la planta incineradora de residus urbans de Montcada i Reixac. Per tal de poder assolir aquest objectiu, s'ha portat a terme la monitorització de l'àrea d'estudi, on s'han determinat els nivells de dioxines, furans i metalls pesants en 24 mostres de sòls i vegetació durant tres anys consecutius (1996, 1997, 1998). D'aquesta manera s'ha realitzat una avaluació espacial i temporal dels nivells de contaminants. Per altra banda, al 1999 la planta d'incineració de Montcada i Reixac va portar a terme unes millores medi ambientals en la seva instal·lació. D'aquesta manera les emissions de dioxines i furans i metalls pesants entre d'altres es van veure reduïdes considerablement. Per aquesta raó, al 2000 es va a tornar a portar a terme una altra monitorització de les emissions de la planta, per tal de determinar de quina manera la disminució en les emissions afectaria els nivells medi ambientals. Anàlisi de riscFinalment, s'ha quantificat el risc per la població degut a les emissions de PCDD/Fs i metalls pesants. El risc avalua la probabilitat de que un efecte advers sobre la salut pugui ocorre després de l'exposició a una dosi determinada d'una substància definida. L'avaluació del risc realitzada ha estat la deguda a l'exposició a contaminants com a combinació de les cinc vies següents: inhalació de partícules, inhalació d'aire, ingesta de sòls i vegetals conreats a l'àrea d'estudi, i absorció dèrmica. Els individus d'una població poden ser descrits per un número de diferents escenaris d'exposició, ja que poden ocorre diferents nivells de risc dins d'una població. Així, per tal d'avaluar la variabilitat i la incertesa del risc s'ha portat a terme una anàlisi de Monte Carlo.

ABSTRACT Key words: PCDD/FS , aromatic precursor compounds , transition metal catalysts , chlorine donor , surface of fly ash particles In the last 20 years , increasing concern has focused on the environmental chemicals that mimic hormone functions , some of them toxic , which producing cancer , suppression of the immune system , and death from undefined causes . These chemicals are not made intentionally , but are formed as contaminants in combustion sources , including PCDD/FS of dioxin-like compounds that emitted from municipal solid waste incinerators (MWSI) and hazardous waste incinerators (HWI) . This study investigated the role that fly-ash plays in the formation of PCDD/FS using a commercial scale fluidized bed waste incinerators (FBWI) , which rated capacity at 3750000 kcal/hr (LHV) . In this design , a lay of sand is placed on the bottom of the combustion chamber. During combustion, the hot gases are channeled through the sand and crushed solid waste at relatively high velocity . This generated about eight times more mass of fly-ash will be produced from combustion zone than the others, and also makes much greater of PCDD/FS through the air pollutants control devices(APCD) to emission stack . The general reaction in this formation pathway is an interaction between an aromatic precursor compound and chlorine promoted by a transition metal catalyst on a reactive fly-ash surface. Since these reactions involve heterogenous chemistry , the rate of emissions is less depended on reactant concentration than conditions that promote formation such as temperature , retention time , transition metal catalysts (e , g,. Cu , Fe , Pb , Zn , Sn) and availability on catalytic surfaces of fly ash particle . These forming conditions will be proceeding a series of well study and experiment on fly-ashes from 4 zones (F1 , F2 ,F3 , F4) of FBWI . PCDD/FS synthesis from combustion of FBWI can potentially be explained by three principal mechanisms that results can be divided into several major parts as follows¡G 1. The fly-ash from zone F3 generated about 47 times more mass of PCDD/FS than zone F1 . 2. The F3 fly-ash proved to be the most active catalytic (Cu , Zn) medium , despite similarities with respect to specific surface area and average pore diameters . In addition , there are up to 75.9 percent by weight of Zn and 97.6 percent of Cu has been found in F3 of overall ashes. 3. In both fly- ash and transition metal catalysts in formation mechanisms are the dominant controlling factor for rates of PCDD/FS.

No description available.

Thesis (Ph.D. (Zoology))--North-West University, Potchefstroom Campus, 2008.

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 (0.0348-0.106 pg I-TEQ/Nm3) were comparable to those detected in the vicinity of MSWIs in Taiwan, but significantly lower than those in a highly industrialized urban area (0.150 pg I-TEQ/Nm3) located in southern Taiwan. The relatively higher atmospheric PCDD/F concentrations was found in winter than in summer. The calculated total dry deposition flux of PCDD/Fs ranged from 0.0274-0.718 ng I-TEQ/m2-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. The annual variations of wet deposition of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in atmosphere were also measured at two sites (A and B). Results showed that particle scavenging dominates in the wet deposition processes for the removal of PCDD/Fs from the atmosphere, the highest value was observed at the highest chlorinated congener. The ambient temperature and the amount of precipitation played an important role in the variation of PCDD/F deposition fluxes. It was found that temperature was inversely associated with the existence of particulate PCDD/Fs, indicating PCDD/Fs are scavenged most efficiently in cold weather. PCDD/F wet deposition fluxes in rainy seasons (from June to August) were significantly higher than those in dry seasons (from December to February), revealing a positive relationship between wet deposition flux and monthly rainfall. Additionally, the annual total (dry + wet) deposition fluxes of PCDD/Fs were 149 ng/m2-year (5.02 ng I-TEQ/m2-year) and 177 ng/m2-year (5.11 ng I-TEQ/m2-year) for sites A and B, respectively, revealing that dry deposition was more dominant than the wet deposition for the atmospheric deposition of PCDD/Fs. Since atmospheric deposition is believed to be the main transfer pathway of PCDD/Fs into food chains, its impact on human exposure to PCDD/Fs is of great importance.

This work investigated the characteristics of polychlorinated dibenzo-p-dioxins anddibenzofurans (PCDD/F) in stack-flue gases from six stationary emission sources in five types ofincinerators: industrial waste incinerator (IWI), small-scale municipal solid waste incinerator(MSWI), medical waste incinerator (MWI), cement kilns (CK), and crematories (CR). These characteristics were further investigated using factor analysis and cluster analysis. Experimental results reveal that PCDDs dominate MSWI and CR, and PCDFs dominate IWIa, IWIb, CK and MWIs. The factor analysis results showed that CR and MSWI have similar fingerprints, as do IWIb and MWI3. The cluster analysis showed that if a vertical line is cut at a rescaled distance of four, then the PCDD/F congener profiles fall into four groups. The indicators of PCDD/Fs are OCDD, 1,2,3,4,6,7,8-HpCDF, 2,3,4,7,8-PeCDF, and 1,2,3,4,6,7,8-HpCDD. The emission factors of PCDD/Fs herein were from 0.0433

This study determined the polychlorinated dibenzo-p-dioxins/ dibenzo- furans (PCDD/Fs) and 22 metals contents in ash in the super heater (SH), economizer (EC), semi-dryer absorber (SDA), fabric filter (FF), fly ash pit (FAP) and bottom residue (BR) in a municipal solid waste incinerator (KTMSWI). Experimental results showed that average PCDD/FS contents in ash samples from the SH, EC, SDA, FF, FAP and BR were 0.102, 0.788, 0.210, 1.95, 2.04 and 0.0218 ng I-TEQ /g, respectively. PCDD/Fs content was very low in the SH and BR due to high temperatures (around 461¢XC in the SH and 914¢XC in combustion chamber). Conversely, total PCDD/Fs content was significantly high in ash samples from the EC (around 340¢XC), mainly because the temperature is within the favorable range of 250-400¢XC for PCDD/FS formation due to de nova reformation mechanisms. Although the SDA operated at 245¢XC, the PCDD/FS content decreased very significantly, mainly because the temperature was relatively low and because calcium carbonate was introduced into flue gases to dechlorinate and dilute chlorine-containing species. PCDD/Fs were captured by the active carbon in the FF. Furthermore, the duration that fly ash remained in the FF was longer than that for other incinerator units, and thus causing an increasing trend of PCDD/Fs level downstream (except the SDA). Total PCDD/Fs emission factors (£gg /ton-waste; £gg I-TEQ /ton-waste) in ash samples from different units were: SH (42.3; 0.846), EC (326; 6.12 ), SDA (58.1; 1.10), FF (1540; 61.3), FAP (2950; 107) and BR (537; 4.31). Most PCDD/Fs in ash were contributed by the FF (about 56%), and the generation of PCDD/Fs in ash was significant (about 35%) during the transfer process from different units to the FAP. A strong and positive correlation in a logarithmic form existed between PCDD/Fs and chlorine (Cl-) contents in ash. The results showed that principal metals in the incinerator ash were Al, Fe, Zn, Ba, Pb and Cu. On average, these six metals accounted for 96.6%, 96.8%, 97.0%, 94.2% and 96.7% of the total metals in SH, EC, SDA, FF and BR ash, respectively. The emission factors of individual metals from different units were obtained. Volatile metals, such as Cd, Sn, Sb, Hg and Pb, were mostly in fly ash, while lithophilic metals, such as Al, Fe, Ti, V, Cu, Mn, Fe, Co, Ni, Cu, Sr, Mo, Ag, Ba and Cr+6 were mainly in bottom ash. Distribution ratios for total metals in SH, EC, SDA, FF and BR ash were 4.87%, 4.26%, 2.89%, 8.17% and 79.81%, respectively. That is, about 20.2% of total metals were in fly ash and most metals (about 79.8%) were in bottom ash. The Pb content in EC ash and Hg content in FF ash were between alarm contents and maximum legal limits, while Cd and Pb contents in FF ash exceeded the maximum legal limits. The existing transportation system for transferring fly ash from different units to a fly ash pit should be modified for recycling the valuable metals. Ash with less than the alarm content for metals content, such as ash from the SH, SDA and BR, can be reused. Ash with metals exceeding the alarm contents, such as ash from the EC and FF, should be collected and transferred to a different fly ash pit for further treatment, such as metal recycling.

Persistent organic pollutants (POPs) are a threat to the environment and human health because they are ubiquitous, resistant to degradation, can bio-accumulate in organisms and bio-magnify in food chains. They have a detrimental effect on the reproductive, nervous and immunity systems of vertebrates. An international treaty, the Stockholm Convention on POPs, came into force in 2004 and aims to limit and eventually prohibit any use and unintentional production of POPs. South Africa ratified the Convention in 2002. Those compounds currently listed by the Stockholm Convention as POPs include chlorinated pesticides such as dichlorodiphenyltrichlorethane (DDT), chlordane and dieldrin, and industry-related compounds such as polychlorinated biphenyls (PCBs) and hexachlorobenzene. Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are also regarded as POPs but - together with some PCBs - they are the unintentional result of anthropogenic activity. This study focussed on the PCDDs, PCDFs and dioxin-like PCBs in the aquatic environment of South Africa particularly because the water resources in this country are under pressure. Despite the fact that South Africa has the sources of these compounds, little is known about the levels of these three groups of compounds. The concentration of twelve dioxin-like PCBs, seven PCDDs and ten PCDFs were determined for 22 sites selected on the grounds of their proximity to possible pollution sources. Analytical determinations included gas chromatography/mass spectrometry and a cell-based bio-assay, the H4IIE-/17C reporter gene assay. Possible sources of the observed pollution were inferred using the following statistical investigative methods: principal component and hierarchical cluster analysis. Seven of the sites had levels higher than the threshold effect concentration of Canada's sediment quality guidelines of 0.85 ngTEQ kg'1 (Toxic Equivalency Quotient). The other sites had lower levels. The highest concentration, 17.8 ng TEQ kg"1, was measured at a site in the southern Gauteng Province. Most of the PCDD/F pollution seemed to have come from combustion sources related to human activity, rather than industrial combustion. Most of the dioxin-like PCB pollution seemed to have been from commercial PCB preparations. Future research would require better characterisation of the sources in order to reduce the formation of these compounds, but also to better understand the exposure and risk scenarios, if humans are to be in close contact with these sources. / Thesis (Ph.D. (Zoology))--North-West University, Potchefstroom Campus, 2008.