PAH compounds

Understanding particulate emissions, their formation and control, is another key issue in meeting the new particulate emission Hmits set by the new EURO emission standards. The particulate emissions formed in diesel engines have a mass median diameter of 0.05-1.0 gm. Particle consists of carbon with various HCs adsorbed on it including polyaromatic hydrocarbon (PAH) as well as nitro-PAH compounds. 

RO can recover metals, antifreeze, paint, dyes, and oils in the retentate while generating cleaned up wastewater permeate for disposal. RO is also used to reduce the volume of waste liquids (e.g., spent sulfite liquor in paper manufacturing). Wastewater treatment application removals of 95 percent TOC, > 90 percent COD, > 98 percent PAH compounds, and pesticides > 99 percent have been seen [Wilhams et al., chap. 24 in Membrane Handbook, Sirkar and Ho (eds.), Van Nostrand, 1992]. 

The separation efficiency of 25,000/m (plate height 40 pm) was reported for neutral PAH compounds like fluorene. 

The most refractory compounds in the resids may be the PAHs. Those present in residues consists of fused rings of more than six cycles, with molecular weight above 600. Some of the complex larger PAHs isolated and identified are collected in Table 10. These examples probably correspond to the smallest PAH compounds in a resid cut, but worth to set the lowest limit to the level of complexity, from where the reacting mixture starts. 

Park, K.S., Sims, R.C., Dupont, R.R., Doucette, W.J., Matthews, J.E. (1990) Fate of PAH compounds in two soil types Influence of volatilization, abiotic loss and biological activity. Environ. Toxicol. Chem. 9, 187-195. 

Sims, R.C.C. (1990) Fate of PAH compounds in soil loss mechanisms. Environ. Toxicol. Chem. 9, 187-. 

PAH Compound, Organism, and Other Variables Concentration in Medium (g/L) Effecta Reference11... 

PAH Compound, Whole Organism, and Other Variables Exposure Period8 BCF Reference ... 

Time to depurate or biotransform 50% of accumulated PAHs (Tb 1/2) varied widely. Tb 1/2 values for Daphnia pulex and all PAH compounds studied ranged between 0.4 and 0.5 h (Southworth et al. 1978). In rainbow trout given an intraarterial injection of 10 mg/kg BW of 2-methylnaphtha-lene, fluorene, or pyrene, the Tb 1/2 values ranged between 9.6 and 12.8 h when route of exposure was intragastric and doses were 50 mg/kg BW, there was negligible uptake (Kennedy and Law 1990). For marine copepods and naphthalene, a Tb 1/2 of about 36 h was recorded (Neff 1982a). 

Effect (units), Organism, PAH Compound Concentration Reference9... 

That many, but not all, four-, five-, and six-ring PAH compounds are carcinogenic... 

Fig. 5a-c. A typical distribution of polycyclic aromatic hydrocarbons in a atmospheric fallout sample, Alexandria City - Egypt b bottom incineration ash leachate of municipal solid waste - USA c hydrothermal petroleum, Escanaba Trough, NE Pacific Ocean. PAH Compound identifications N = naphthalene, MN = methylnaphthalene, DMN = dimethylnaphthalenes, P = phenanthrene, MP = methylphenanthrene, Fl = fluoranthene, Py = pyrene, BaAN = benzol anthracene, DH-Py = dihydropyrene, 2,3-BF = 2,3-benzofluorene, BFL = benzo[fc,/c]fluoranthene, BeP = benzo[e]pyrene, BaP = benzo[a]pyrene, Per = perylene, Cx-228 = methyl-228 series, Indeno = indeno[ l,2,3-c,d]pyrene, DBAN = dibenz[a,/z]anthracene, BPer = benzo[g,/z,z] perylene, AAN = anthanthrene, DBTH = dibenzothiophene, Cor = coronene, DBP = dibenzo [a,e]pyrene, DBPer = dibenzo [g,h,i] perylene... 

Table 8. Toxicity values (EC50) and molecular connectivity indices for various PAH compounds...

A QSAR (see Sect. 2.2) is a mathematical model between a property (activity) of a certain compound, in this case the chronic toxicity value of a certain PAH compound, and the descriptors of that PAH. The descriptors are chemical or physical characteristics obtained experimentally or from the structure of the compound itself. In order to develop the MOLCONN-QSAR model, Aboul-Kassim [1] ... 

Used a QSAR modeling technique to predict the chronic toxicity of untested PAH compounds for which the descriptors are known. 

Valence indices, (denoted with a v superscript) which encode sigma, pi, and lone electrons and thus include more information about the specific elements included in the PAH compound. 

PAH mixture ID PAH compounds in mixtures Experimental values MOLCONN-QSAR predicted values ... 

The experimental results and the procedure used in determining the TU of the eighth PAH compound (i.e., TU8) that would induce 50% growth inhibition for the fresh water alga Selenastrum capricornutum are detailed in Fig. 12 for only a single test on the eighth component PAH mixture (i.e., 8-C1, see Table 9 for the mixture composition). 

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