Anthropogenic Polycyclic Aromatic

Anthropogenic Polycyclic Aromatic witness Apportionment of Anthropogenic Polycyclic Aromatic Hydrocarbons (PAHs) by Molecular and Isotopic CharacterizationA dissertation submitted as part of the beseechments for the Degree of Master of ScienceAbstractPolycyclic aromatic hydrocarbons (PAHs) are important, ubiquitous environmental pollutants known for their carcinogenic and mutagenic properties. They are mercantile establishmentd into the atmosphere, shite (which bears ab protrude 90% of the environmental PAH burden in the UK) and water by natural and anthropogenic processes. Today, anthropogenic combustion of fogey fuel is, by far, the approximately important seminal fluid of PAH input into the environment.The importance of PAHs as environmental pollutants with a numerousness of sources has resulted in considerable interest in source apportionment techniques. This line of business therefore investigated the PAH profiles in road dust samples around a last temperature carboniza tion plant (Barnsley, South Yorkshire) and used the combination of molecular(a) methods and hitman chromatography-isotope symmetry mass spectrometry (d13C GC-IRMS) to identify their origin.Quantification of the sixteen U.S EPA priority PAHs extracted from the dust samples ranged from 2.65 to 90.82g/g. The PAH profiles were dominated by phenanthrene for 2-3 ring PAHs and by fluoranthene, pyrene, chrysene and benzo(b+k)flouranthene for PAHs with ring size 4. The fluoranthene to pyrene (Fl/(FL+P)) )) concentration ratio ranged from 0.51 to 0.55, eon the indenol(1,2,3-cd)pyrene to benzo(ghi)perylene (IcdP/(IcdP+ BghiPer)) ratio ranged from 0.37 to 0.55 suggesting partings from diesel combustion, most likely from heavy duty trucks.The ability of compound-specific stable isotope measurement, using d13C GC-IRMS, to source apportion environmental PAHs where authoritative input from char is expected has been demonstrated. The PAH d13C isotope ratio values ranged from -25.5 to -29.7%o. Overall, the d13C isotope ratio, in conjunction with PAH molecular distribution/ratio, strongly suggest that PAHs in the study area claim inputs from both high temperature ember carbonisation and transport fuels (mainly diesel combustion).Chapter One1.0 IntroductionIndustrialization, centered on energy use, has been the driving force for many of the greatest advances in the twentieth century and is central to our way of life in the modern world today. Energy improvements and the discovery of fogy fuel (coal and petroleum) seduce hastened industrialization and break by means ofs in areas such as travel, communication, agriculture and healthcare, in many parts of the world.Despite these achievements, industrialization has brought along with it global problems of environmental pollution and challenges. These include exploitation of natural resources, petroleum spillages, global warming due to rising releases of carbon dioxide and other green house gases, disposal of wastes (industr ial and domestic) and inorganic and organic emissions which ultimately affect air, water and trim quality. The release of organics/organic effluents such as polycyclic aromatic hydrocarbons (PAHs), mainly from the use of fossil fuels into the environment watch particularly gained attention in recent time due to their toxicity and persistence.1.1 Polycyclic Aromatic Hydrocarbons (PAHs)Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants that are of great public concern due to their toxicity, carcinogenicity and/or mutagenicity (Fabbri et al., 2003 Sharma et al., 2007). They are continuously introduced into the environment by both natural processes, such as volcanic eruptions and forest fires and anthropogenic sources which include various industrial processes such as deoxycytidine monophosphate production in the iron and steel industry, catalytic cracking in the petroleum industry, coal gasification, heating and government agency generation, open bur ning of vegetation and intrinsic combustion engines used for various means of transportation (Suess, 1976 Morasch et al., 2007). Immense PAHs contaminations of the environment typically originate from anthropogenic sources.A natural balance existing amidst the production and natural degradation of PAH historically kept the background concentration of PAH in the environment minor and fixed (Smith and Harrison, 1996). The ever-increasing industrial development and use of fossil fuels in many parts of the world released PAHs into the environment resulting in their universal occurrence in air, water, soil and sediments. This increase in the production rate of anthropogenic PAHs has disrupted the natural balance of PAHs in the environment, while their rate of decomposition remains more or less constant (Suess, 1976 Fetzer, 1988).PAHs are found in great abundance in fossil fuel materials such as shale oil, coal liquids, petroleum, asphalt and many other hydrocarbon based materials (Fet zer, 1988). Incomplete combustion of these fossil fuel materials produces fly ash, chimney soot and engine-derived air particulates which have higher levels of PAHs than the original materials (Chadwick et al., 1987 Fetzer, 1988).Generally, PAHs give rise to evidential impact to the areas close to the nearest storey sources (Ohkuchi et al., 1999). There are very high concentrations of atmospheric PAH in the urban environment which is accounted for by the various industrial processes earlier identify, increasing vehicular job and the scarce dispersion of the atmospheric pollutants. These PAHs are emitted to the atmosphere either in the gaseous build or on very small particles, 70-90% of which are in the respirable range (et al., 1987). The risk associated with the human exposure to atmospheric PAH is therefore highest in the cities because of these factors and the density of population (Sharma et al., 2007).In view of the carcinogenic potential of many PAH compounds, their contri bution to the mutagenic activity of ambient aerosols and range of sources of emission, their concentration in the environment is considered alarming and efforts should be made to reduce or even eliminate them wherever possible. To achieve this, a better understanding of their fate and associative transformation pathways in the environment is necessary and this has resulted in considerable interest in PAHs source apportionment.1.2 Source ApportionmentMost organic pollutants can be released into the environment from various sources. Hydrocarbon pollutants are particularly widespread in the environment due to the multiplicity of their sources such as synthesis by living organisms (biogenic origin), degradation of organic matter (diagenic origin), incomplete combustion of organic matter and natural and anthropogenic fossil fuel combustibles (petrogenic origin) (Mazeas et al., 2002).Due to the multiplicity of the sources of organic pollutants, source apportionment techniques are invalua ble in the determination of the contributions of various pollution sources of a pollutant in the environment. Source apportionment generally refers to the quantitative assignment of a combination of distinct sources of a particular group of compounds put into a system (OMalley et al., 1994). Differences in emission profile, among emission sources, have been sufficiently used to develop fingerprints that can be identified and quantified at a particular site (Dallarosa et al., 2005).As mentioned earlier, most of the environmental PAHs have anthropogenic origins. Contributions from coal combustion and use of petroleum in internal combustion engines for transportation have increased over the years and have generated a lot of concern. It is therefore important to be able to distinguish different sources that contribute to PAH pollution of a particular environment using steady-going source apportionment techniques.This project work is therefore aimed at contributing to the know directge of reliable, unambiguous novel PAH source apportionment techniques by(i) Identifying and quantifying contemporary PAHs fluxes in the environment around a coking works using molecular methods(ii) Demonstrating the ability of compound specific stable isotope measurement to source apportion environmental PAHs where significant input from coal is expectedChapter Two2.0 Literature Review2.1 General overview of the properties of PAHsPolycyclic aromatic hydrocarbon (PAH) compounds are a class of complex organic chemicals made up of carbon and hydrogen with a fused ring structure containing at least 2 benzene rings (Ravindra et al., 2008). They may also contain additive fused rings that are not six-sided (Figure 1).Pyrosynthesis and pyrolysis are two main mechanisms that can explain the formation of PAH from saturated hydrocarbons under oxygen-deficient conditions. Low molecular tip hydrocarbons like ethane form PAHs by pyrosynthesis (Figure 2). At a temperature greater than 5000C, carbon -hydrogen and carbon-carbon bond are broken to form free radicals which combine to form acetylene. alkyne condenses further to form aromatic ring structures which are resistant to degradation (Figure 2). The ease with which hydrocarbons may form PAH structure varies in the order aromatics cycloolefins olefins Paraffins (Ravindra et al., 2008). The higher molecular weight alkanes in fuel form PAH by pyrolysis the cracking of organic compounds.The discovery of the fluorescence of a number of known carcinogenic tars and mineral oils in 1930 led to the investigation of the carcinogenic properties of PAHs. This spanned from the discovery that benz(a)anthracene and other compounds in its group possessed a similar fluorescence (Chadwick et al., 1987). Initial investigation for PAH carcinogenicity using dibenz(a,h)anthracene later resulted in the closing off of a federal agencyful carcinogenic substance from coal tar benzo(a)pyrene (Chadwick et al., 1987).Since the discovery of benzo(a) pyrene, various works have been done to identify other carcinogenic PAHs. sixteen (16) parental PAHs have been designated by the US environmental protection agency (US EPA) as priority pollutants and most of the studies have focused on these (Figure 1 and get across 1). Seven (7) of these (Table 2) have been identified by the International Agency for Research on Cancer (IARC) as animal carcinogens and have been studied by the EPA as potential human carcinogens (EPA report, 1998). PAH can undergo metabolic transformation into mutagenic, carcinogenic and teratogenic agents in aquatic and terrestrial organisms. These metabolites, such as dihydrodiol epoxides, bind to, and disrupt, deoxyribonucleic acid and RNA, which is the basis for tumor formation (Wild and Jones, 1995).Although PAHs are renowned for their carcinogenic and mutagenic properties, not all of them are environmentally or biologically significant. Studies have been carried out on monitoring the levels of some of the impo rtant PAH in various parts of the world and the results of a number of these are summarized in Table 2. The carcinogenicity and/or mutagenicity of PAH, which require metabolic conversion and activation, is structurally dependent while certain isomers can be very active, other similar ones are not (Fetzer, 1988). An example, as shown by Fetzer (1988), is found in the five PAHs with molecular weight of 288 and containing 4 rings. Chrysene, benzaanthracene and benzocphenanthrene are mutagenic but the remaining two, napthacene and triphenylene are not. As molecular weight increases, the carcinogenic level of PAHs also increases and acute toxicity decreases (Ravindra et al., 2008).The p electron fused benzene rings in PAHs account for most of their physical properties and chemical perceptual constancy (Lee et al., 1981). The 2-ring and 3-ring PAHs compounds, which are more mercurial and water soluble, but less lipophilic than their higher molecular weight relatives, generally exist pr imarily in the gas phase in the atmosphere and will tend to be deposited to the surfaces via dry gaseous and/or wet deposition (Ravindra et al., 2008). On the other hand, the less volatile 5-6 ring PAHs tend to be deposited on surfaces bound to particles in wet and dry deposition while compounds of intermediate vapor pressure will have a temperature-dependent gas/particle partitioning of PAHs leading to both wet and dry deposition in gaseous and particle-bound form (Mannino and Orecchio, 2008).PAHs have a angle of inclination to sorb on hydrophobic surfaces and this tendency increases with the number of aromatic rings (Morasch et al., 2007). Thus, PAHs are primarily found/present in the environment in soils and sediments, kind of than water and air. Their high hydrophobic tendency and high lipophilic properties make them easily bio-accumulated to such an extent that can threaten the safety of food fetter for both man and animals (Sun et al., 2003).CompoundsChemical formulaMolecul ar weightMeltingpoint, oCBoilingpoint,oCParticle/gas phase distributionNapthaleneC10H8128.1980.5218AcenaphthyleneC12H8152.21 flub phaseAcenaphtheneC12H10154.2196.2279Gas phaseFluoreneC13H10166.22116 -117295Gas phasePhenanthreneC14H10178.24100 101340Particle phaseAnthraceneC14H10178.24216.5 217.2339.9Particle phaseFluorantheneC16H10202.26110.6 111.0393Particle phasePyreneC16H10202.66152.2 152.9360Particle phaseBenz(a)anthracene*C18H12228.30159.5 160.5435Particle phaseChrysene*C18H12228.30250 254448Particle phaseBenzo(b)fluoranthene*C20H12252.32Particle phaseBenzo(K)fluoranthene*C20H12252.32215.5 216Particle phaseBenzo(a)pyrene*C20H12252.32176.5 -177.5311Particle phaseIndeno(1,2,3-cd)pyrene*C20H12276.34Particle phaseDibenz(a,h)anthracene*C22H14278.34205Particle phaseBenzo(ghi)peryleneC20H12276.34273Particle phase*PAHs identified animal carcinogens and as potential human carcinogensTable 1 Physical properties of 16 priority PAHs on US EPA listing (Adapted from EPA REPORT, 1998, Ravindra et al., 2008)S/N check PAHsMean (ngm-3)Cities1 15 PAHs56Columbia (USA)2 15 PAHs412Austria3B (a) P4.99-9.56aDelhi4 12 PAHs93Denver (USA)5 8 PAHs150-1800aDelhi6 15 PAHs166London7 15 PAHs59Cardiff8 11 PAHs90-195 (I)a, 20-70 (R)aAhmedabad9 12 PAHs22.9-190.96aKolkata10 12 PAHs20-95a, 125-190aMumbai, Nagpur11 13 PAHs90.37 57.04Coimbatore12 11 PAHs310 (60-910)aMexico city13 15 PAHs8.94-62.5aCamo Grande city14 16 PAHs13-1865aChicagoI= industrial site, R = residential site, a RangeTable 2 A summary of mean concentrations (ng/m3) of total PAHs in various cities of the world (Sharma et al., 2007)2.2 Anthropogenic sources of PAHSThe high concentration of PAHs in the environment, as shown in Table 2, suggests the extent of anthropogenic contribution (Sharma et al., 2007). It is, however, difficult to estimate the amount of anthropogenic PAHS on the yearly input of the various sources on a global basis.An approximate quantification has been made, based on the yearly consumption of fossil fuel, that while the global annual release of PAHs to the atmosphere is of an order of 105 tonnes, including 103 tonnes of benzo(a)pyrene the annual input of crude and processed oil containing 1-3% PAHs to the oceans of the world is 1.1106 tonnes (Ivwurie, 2004).The main anthropogenic sources of carcinogenic PAHs are emissions from fossil fuel combustion in industrial and power plants, automobile emissions, biomass burning, agricultural burning and natural gas utilization. Fossil fuel utilization is the major cause of anthropogenic PAH occurrence in the environment. Hence, emphasis is fit(p) on these sources below.2.2.1 PAHs from Coal Combustion and Conversion ProcessesCoal, an organic rock formed from the accumulation and burial of partially decomposed vegetation in previous geologic ages through a series of physical, biological and biochemical changes is a major fossil fuel for heating and power generation. The predominant organic components in coal have resulted from the format ion and condensation of polynuclear carboxylic and heterocyclic ring compounds containing carbon, hydrogen, oxygen, nitrogen and sulphur (United Nations, 1973).Due to its chemical composition (heterogeneous macro-molecular matrix, including hydrocarbons and hetero-atomic moieties) various coal conversion and utilizations are significant contributors of PAHs to the environment.Coal combustion emissions47 PAH compounds resulting from coal combustion residing in fly ash, grate ash or the stack emissions were identified in the work of scrap and Ford (1980, cited in Chadwick et al., 1987). However, these PAH emissions are a function of the efficiency of the coal combustion plant. On the whole, large, efficient coal-burning, electricity-generating plants, with high combustion temperatures, emit relatively low total amounts of PAH and contribute very little to PAH emissions when operated properly (Chadwick et al., 1987).PAH emission factors for coal-fired plants were put at 32ugkg-1 and 4 1ugkg-1 coal by Ramdahl et al. (1983) and Masclet et al. (1987) respectively. 70% of the total PAH emission flux from power plants is made up of 3-4 ring PAHs and their alkylated counterparts (Wild and Jones, 1995). 5-6 ring PAHs and their heteroatom-containing derivatives are emitted from coke ovens during coal carbonisation (Kirton et al., 1991)Coal carbonization emissionsCoal carbonization, the pyrolytic decomposition of coal in the absence of oxygen, can be classified according to the temperature to which the coal is heated, as shown in Table 3. This process yields char or coke, tar and oven or coal gas as the major products.Coke is by far the most important product in terms of yield and revenue. However, leakages from coke ovens are sources of release of high levels of PAHs and other organics to the environment. Emissions from coke ovens range from volatile monoaromatics (alkyl benzenes) to 5-6 ring PAHs together with their substituted heteroatom derivatives such as O-PAHs, NPA Hs and S-PAHs (Lao et al., 1975 Kirton et al., 1991). Anderson et al. (1983) determine