Fossil Fuel Fires: A Forgotten Factor of Air Quality

1. Introduction – fossil fuel fires

Spontaneous fires of fossil fuels – mainly coals but also bituminous shales and oil shales – are known worldwide. They both concern natural environments and their anthropogenic analogues – burning mining waste heaps (BCWH). The CWHs are, more or less, permanent elements of the environment of coal basins. Although sometimes under reclamation, their recultivation procedures may also negatively influence the surroundings. The phenomena taking place in the BCWH are described, e.g., in Nasdala & Pekov [1], Cebulak et al. [2], Sokol et al., [3], Stracher [4], and papers of Ł.K. The later largely characterize complex products of gaseous emissions related to both coal and barren rock – mutually known as mining waste – burning. This chapter characterizes the composition of these emissions, by juxtaposing published concentrations and their related mean values with new data obtained for new BCWH-type object. As such, the chapter extends knowledge about the geochemical charge of the BCWH gaseous emissions and, as such, their potential atmospheric input.

2. Environmental gas emission measurement methods

Numerous methods of gas analysis in the environment exist. One of the most simple one, based on colorimetric chemical reactions, uses indicatory tubes (IT). This method is based on colorimetric interaction of measured gaseous species with a chemical filler. In particular, Dräger tubes allow to detect and measure amounts of gases like O₂, CO₂, CO, NO₂, SO₂, NH₃, PH₃ (phosphine), acetic acid, acetone, propane, benzene, toluene, styrene, o-xylene, butadiene, total mercaptans (thiols), methanol, i-propanol, trichloroethene (TCE), vinyl chloride, methyl tert-butyl eter (MTBE), and others. However, the IT method brings large errors due to cross-sensitivity and numerous coincident reactions of the emanation-contained gaseous species, and humidity. Positive determinations for the BCWHs gases were thus single, and the following substances were observed (with semi-quantitative due to the above factors): H₂S (up to 1140 ppm), HCN (single determination (s.d.), 16 ppm), acetaldehyde (possibly up to 1150 ppm), diethyl ether (up to 1100 ppm), trimethylamine (and/or other amines; ca. 57 ppm), ethyl formate (s.d., <23 ppm), and I₂ (s.d., 1.7 ppm). Gas Chromatography (GC) is a method of choice for the analysis of environmental organics. A sample is put into specialized columns, where retention time of a particular molecule, related to its mass and charge (m/z parameter), is measured. However, it is relatively rarely used for gas analysis due to a need of a more sophisticated sample loader. This is overcame by a method of Colman et al. [5], where a sample sucked into a steel can and sent to laboratory (here: overseas) is reheated (to the temperature measured in situ), divided into aliquots with various pre-treatments including (1) passing heated aliquots over a glass for low-volatile compounds exerting and (2) water-immersion-driven revolatization, and (3) chromatographic separation. Analyses of such portioned sample using 3 detection methods: Mass Spectrometry (MS), Flame Ionization (FI), and Electron Capture (EC), both shown in Kruszewski et al. [6] and this chapter, proven to be problematic, as explained below.

The GC method is, however, useful in the environmental gas analyses if coupled with tools like Nitrogen-Phosphorus-Detector and cryo-focusing. A good example is a work of Wickenheiser et al. [7], who analyzed gases emitted from Italian wetland bogs. The compounds included PH₃, ethane, ethene, and NO_x. GC coupled with Inductively Coupled Plasma – Mass Spectroscopy (ICP-MS) allowed them to address heavy organo(semi/non)metallic gases like trimethylarsine (TMA), (CH₃)₃As, and trimethylstibine (TMS), (CH₃)₃Sb, and also metallic Hg, emitted from algal mats. The same method allowed to Feldmann et al. to detect (via cryo-trapping) trimethylbismuthine, (CH₃)₃Bi, as a common gas in municipal solid waste and sewage gas. Traces of tetramethyltin and TMS were also detected this way (vide [8]). Another method mentioned by the latter author is hydride generation. The use of tedlar bags, a gas trapping solution (with HNO₃ and H₂O₂), charcoal sorbent tubes, preconcentrators, and analysis with GC–MS and GC-PID (GC with photoionization detection) is also widely exploited, e.g., to measure TMA and propanethiol [9]. A method to be exploited by the author (Ł.K.) is a GC in conjunction with Atomic Emission Spectroscopy (AES). This two-step method involved very-low-detection-limit analysis, both qualitative and quantitative, of mainly (semi)metals in a gas sample, followed by analysis of their immediate surroundings for proposing types of organic and inorganic (semi)metal forms (R. Stasiuk, pers. comm.).

3. Mining waste heaps and products of their fires

A large number of coal mining waste heaps bear numerous spontaneous fire foci. In these burning coal-mining waste heaps (BCWHs), the fire incidents are due to criss-crossing influence of coal petrography (i.e., maceral composition), sulfide mineral content (especially pyrite), coal rank, and microbial activity. The fires induce three types of mineral-forming phenomena: a high-temperature solid–solid and gas–solid transformation of the waste, known as pyrometamorphism (up to ∼1200°C in the coal case; [3]); medium-temperature exhalative processes; and low-temperature supergene weathering processes ([6, 10, 11, 12], and references therein). Of the Air Quality interest is, of course, the second group of processes, involving both gas emission and gas-waste interface reactions. The latter include direct gas desublimation (condensation) and pneumatolysis-like gaseous extraction of various waste-contained metals followed by hydrothermal mineralization. The first process mainly produces minerals like native sulfur (S₈), salammoniac (NH₄Cl), and a number of less frequent species like kremersite, (NH₄,K)₂[FeCl₅(H₂O)] and other chlorides. The second one is responsible for vast, thick sulfate crusts mainly comprising godovikovite-sabieite solid solution, (NH₄)(Al,Fe)(SO₄)₂, millosevichite-mikasaite solid solution, (Al,Fe)₂(SO₄)₃, steklite, KAl(SO₄)₂, tschermigite, (NH₄)Al(SO₄)₂·12H₂O (natural ammonium aluminum alum), alunite-supergroup minerals, and many others. Pyrometamorphic processes and their product in Polish BCWH – within both the Upper and Lower Silesian Coal Basins (USCB and LSCB, respectively) was extensively studied, e.g., by Kruszewski [13, 14] and Kruszewski et al. [15, 16], with process imitation experiments described, e.g. by Kruszewski [10]. Mineralogy of the exhalative processes and gas phase composition of the local fumaroles was largely addressed by Kruszewski [6, 12, 17, 18, 19]. Fabiańska et al. [20] and Lewińska-Preis et al. [21] addressed some environmental aspects of the gas emissions in question. Supergene mineralogy was described in Kruszewski [11]. Presentation of the BCWH as models of various natural environments, including extraterrestrial ones, was shown by Kruszewski et al. [22, 23]. Biological aspects of the BCWH environment were brought up by Kruszewski & Matlakowska [24].

The fumaroles bear numerous minerals rich in trace and toxic elements, like zinc, copper, nickel, arsenic, thallium, lead, bismuth, selenium, bromine, iodine, indium, silver, and others. The mineral segregations are, obviously, related to the gas phase composition. Analyzing the latter was somewhat pioneering, as we could not find any literature sources showing the use of a portable FTIR (Fourier-Transformed InfraRed) spectroscopy for in situ analyzing of gaseous emissions, at least in the BCWH or the coal-fire environment in general. The IR method is a type of spectroscopy where vibrations of chemical bonds in molecules are being addressed, and depicted by their interaction with IR laser (a similar method is Raman spectroscopy). Various types of vibrations (i.e., stretching, bending, rocking, and other types) are responsible for various peaks in the spectra observed. Most compounds show response to the IR light (i.e., IR laser), by a pattern more or less characteristic for the particular molecule. Some exceptions include H₂S (hydrogen sulfide), which – in the variation of the IR method described here – gives only weak signals, thus making the aforementioned IT method somewhat more useful. The main components were shown (in [6]) to be H₂O and CO₂, with minor but variable add of CH₄ and CO. However, the composition was shown to be much more complex. The portable FTIR GASMET DX-4000 (OMC ENVAG) system was thoroughly characterized in Kruszewski et al. [6, 12]. It system a tool of choice for analysis of complex, hot, chemically aggressive and char- and ash-rich emanations, including combustion/exhaust gases. It comprises a probe with stainless-steel tip, connected with special wires with gas conditioning system (with a pressure control, pump, and system of 2 μm filters for catching any solid and liquid contaminants) and then the FTIR spectrometer. The interferometer has a ZnSe beam splitter; the sample cell has its path length of 5.0 m, volume is 0.4 L; Viton gaskets, MgF₂ protective coating, and BaF₂ window are present, too. The whole sampling system is internally coated by protective layers of rhodium and, gold and nickel.

FTIR results obtained for total 52 fumaroles in four BCWHs located in Pszów, Rybnik-Rymer, Radlin, and Rydułtowy (USCB), respectively, showed up to [in ppm, unless noticed; whole-range maximums underlined]: H₂O57.5, 19.3, 12.5, 36.2 vol.%; CO₂67.2, 7.63, 6.82, 30.6 vol.%; CO2690, 694, 21, 347; NO434, 38, 123, 151; N₂O not observed (n.o.), 0.42, 1.2,8.7; NO₂16430, 116, 24, 191; NH₃1715, 646, 14, 98; SO₂582, 74, 64, 226; HCl58, 23, 2.4, 8.9; CCl₄22, 1.5, 6.0, 14; HF 4.0, 2.2, n.o.,5.1; SiF₄ 1890, 228, 504,1980; AsH₃8.2, 0.49, 0.18, 0.64; CH₄82970, 1050, 838, 888; ethane511, 306, 42, 316; propane1446, 100, 16, 284; hexane921, 123, n.o., 262; ethene92, 28, 21, 21; dichloromethane (DCM)5472, 1730, 241, 1980; 1,1-dichloroethane (1,1-DCE)2110, 580, 175, and 742; 1,2-DCE573, 28, 7.4, n.o.; 1,1,1-trichloroethane (1,1,1-TCE) 7.7, n.o.,40, 23; 1,2-dichloropropane (1,2-DCP)4900, 12, n.o., 44; 1,1-dichloroethene (1,1-DCEe) 51, 3.3, 34,140; vinyl chloride 1700, 809, n.o.,1980; chlorobenzene416, 71, 92, 100; cumene (i-propylbenzene)194, 84, 35, 75; phenol 43,348, 37, and 103; o-cresol (2-methylphenol)1620, 99, n.o., 99; furan 27, 29,130, 12; tetrahydrofuran (THF) 598, 372, n.o.,2830; thiophene781, 578, 773, 550; acetic acid7000, 12, 12, 650; dimethyl sulfide (DMS) 6650, 2230, n.o.,6780; dimethyl disulfide (DMDS)518, 36, n.o., 97; formaldehyde5.7, n.o., n.o., and 3.1. Pyridine was observed only in Radlin, in very constant amounts, 10–11 ppm. Although certified (as in the case of other compounds in the calibration library), the maximum contents of germanium tetrachloride, GeCl₄, i.e., 3130, 209, 333, and 2098 should be treated with care due to possible coincidence as yet unresolvable by the Calcmet software. Geometric means of the concentration values (Pszów, Rybnik-Rymer, Radlin, Rydułtowy, whole series) are: H₂O 31, 12, 3.0, 21, and 19 (n _total = 46); CO₂ 31, 4.0, 0.22, 11, and 7.0 (n _total = 50) [vol.%]; CO 84, 186, 9.6, 81, and 81 (n _total = 41); NO 87, 15, 14, 66, and 42 (n _total = 24); NO₂ 334, 38, 14, 42, and 41 (n _total = 26); N₂O -, 0.10, 0.66, 4.3, and 0.83 (n _total = 17); NH₃ 287, 22, 3.4, 59, and 88 (n _total = 18); SO₂ 110, 18, 17, 48, and 56 (n _total = 31); HCl 7.4, 4.2, 0.56, 3.0, and 3.8 (n _total = 46); CCl₄ 3.2, 0.18, 0.91, 2.5, and 1.6 (n _total = 51); HF 4.0, 2.2, −, 3.3, and 3.4 (n _total = 9); SiF₄ 16, 114, 94, 182, and 65 (n _total = 29); AsH₃ 1.1, 0.19, 0.17, 1.0, and 0.58 (n _total = 26); CH₄ 1945, 500, 23, 537, and 457 (n _total = 47); ethane 46, 114, 15, 75, and 59 (n _total = 37); propane 148, 70, 16, 27, and 46 (n _total = 27); hexane 160, 25, −, 15, and 38 (n _total = 26); ethene 7.9, 7.3, 11, 8.3, and 8.2 (n _total = 28); DCM 230, 119, 160, 295, and 214 (n _total = 45); 1,1-DCE 235, 190, 98, 99, and 139 (n _total = 32); 1,2-DCE 153, 28, 7.4, −, and 91 (n _total = 9); 1,1,1-TCE 5.4, −, 40, 9.5, and 7.7 (n _total = 19); 1,2-DCP 1038, 5.7, −, 20, and 166 (n _total = 9); 1,1-DCEe 19, 2.6, 31, 25, and 20 (n _total = 35); vinyl chloride 329, 38, −, 394, and 289 (n _total = 32); chlorobenzene 24, 36, 92, 32, and 32 (n _total = 12); cumene 28, 30, 35, 15, and 22 (n _total = 38); phenol 14, 36, 3.8, 32, and 19 (n _total = 32); o-cresol 115, 21, −, 99, and 73 (n _total = 15); furan 11, 9.8, 72, 12, and 31 (n _total = 18); THF 126, 372, −, 643, and 195 (n _total = 10); thiophene 251, 200, 90, 156, and 186 (n _total = 40); formaldehyde 3.5, −, −, 0.54, and 0.82 (n _total = 8); acetic acid 189, 6.6, 8.1, 83, and 54 (n _total = 22); DMS 517, 433, −, 921, and 533 (n _total = 16); DMDS 68, 11, −, 31, and 41 (n _total = 35); and pyridine -, −, 11, −, and 11 (total 8 records).

GC results were also published in the paper, with confirmed occurrence of carbonyl sulfide, COS, carbon disulfide, CS₂, freons (CCl₃F, CCl₂F₂, CHClF₂), i-butane, n-butane, i-pentane, n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, propene, 1-butene, i-butene, trans- and cis-2-butene, trans- and cis-2-pentene, ethyne, 1,3-butadiene, isoprene (2-methyl-1,3,-butadiene), 2,3-dimethylbutane; 2- and 3-methylpentanes; benzene, toluene, m/p- and o-xylenes, styrene, ethylbenzene, n- and i-propylbenzene; 2-, 3,- and 4- (or m-, p- and o-)ethyltoluene; 1,2,3-, 1,2,4-, and 1,3,5-trimethylbenzenes; and α- and β-pinene. As shown in the paper, the GC results may be quite unreliable due to their non-in situ character and possible intra-gas and gas-steel interactions, and are thus not resumed here. In turn, we have later used a second and third mode of the FTIR spectra reading. The first one is an external library search, where the spectra are read and calculated using libraries containing other compound sets, thus reporting semi-quantitative results with fit factor (r², in %), as described in Kruszewski et al. [12]. Any misfits are due to recording the standards in different conditions than in the DX-4000 calibration library case. Applying this method allowed to detect additional compounds for the previously listed 4 BCWH sites [in ppm, with results for fit ≥90%, 75–90%, 50–75%, and < 50%, and whole-data maximums underlined]: acetylene, C₂H₂ (up to 0.81; up to 27; up to 38; up to288), n-butane (−; −;7.1; 1.5), i-butane (−; −;9.7; 0.25), propene (−; −; up to101; up to 30), n-pentane (−; −;4.0; 1.9), i-pentane (−; −;11; 0.91), heptane (−; −; up to2.1; −), octane (−; −; up to2.3; −), nonane (−; −; up to2.1; −), decane (−; −; up to2.0; −), undecane (−; −; up to2.0; −), 1,3-butadiene (3.2; −; up to 144; up to169), cyclohexane (−; −; up to2.7; −), α-pinene (−; −; up to4.0; up to 1.1), limonene (C₁₀H₁₆; −; −; up to4.9; 2.7), 3-carene (C₁₀H₁₆;512; up to 2.2), benzene (8.8; up to 5.1; up to 52; up to5700), toluene (−; −; up to74; up to 18), styrene (−; 88; 0.76; up to154), m-xylene (−; −; 19; up to51), p-xylene (−; −; 16; up to23), ethylbenzene (−; −; −; up to8.4), 1,3,5-TMB (−; −; up to729; up to 32), 1,2,4-TMB (−; −; up to1610; up to 27), 1,2,3-TMB (−; −; up to1360; up to 23), tetrachloroethene (−; up to 4.3; up to28; up to 27), methanol (11; 5.4; up to 18; up to75), ethanol (16; 5.4; up to 38; up to126), i-propanol (isopropanol; −; −; −; up to16), i-butanol (isobutanol; −; −; −;5.4), n-propanol (−; −;982; −), methanethiol (methylmercaptan), CH₃SH (−; −; −; up to55), ethanethiol (ethylmercaptan), C₂H₅SH (−; −;2500; up to 14), HCN (up to 8.4; up to 16; up to88; up to 65), acrylonitrile (prop-2-enenitrile, CH₂ = CHCN; −; 6.0; up to 63; up to82), isocyanic acid (−; −; −; up to717), formic acid, HCOOH (3.0; 8.7; up to 29; up to48), trimethylamine, (C₂H₅)₃N (−; −; −; up to1.5), acetaldehyde (up to 45; up to 97; up to 1810; up to6270), propionaldehyde (propanal), (C₂H₅)CHO (−; −; −; up to24), 2-ethylhexylaldehyde (C₄H₉CH(C₂H₅)CHO; −; −; up to342; −), acrolein (propenal, CH₂ = CHCHO; −; 1.6; up to57; up to 25), acetone (propan-2-one) (−; −; −; up to98), methyl ethyl ketone (MEK, or butan-2-one), CH₃C(O)C₂H₅ (−; −; −; up to28), methyl isobutyl ketone (MIBK, or 4-methylpentan-2-on), (CH₃)₂C₂H₃C(O)CH₃ (−; −; −; up to2.6), diethylether (ethoxyethane, (C₂H₅)₂O; −; −; 1.7; up to24), MTBE (−; −; −; up to9.4), 2-ethoxyethanol, (C₂H₅)O(CH₂)O(C₂H₅) (−; −; up to47; up to 32), 2-ethoxyethyl acetate (−; −; −; up to19), butyl acetate (−; −; −; up to15), 2-(2-butoxyethoxy)ethyl acetate (−; −; −; up to13), methyl metacrylate (methyl 2-methylprop-2-enoate; −; −; −; up to10), PH₃ (phosphine; −; up to 43; up to 144; up to152), COS (up to 0.88; up to6.1; up to 0.40; −), and last but not least SF₆ (−; −; up to1.6; up to 1.5). The last compound is environmentally very important, as it is said – by the Intergovernmental Panel on Climate Change – to be the most potent greenhouse gas [25]. The measured BCWH emanation concentrations are also much higher (over 170000 times) than the highest ones measured at Mauna Loa fumaroles [26]. Calculated geometric means (whole series; with values for fit ≥50% in the parentheses): 13 (2.3) for acetylene (n = 14 (31)), 25 (51) for propene (n = 9 (3)), 17 (29) for 1,3-butadiene (n = 15 (5)), 0.76 for α-pinene (n = 6), 3.5 for limonene (n = 3), 6.2 for 3-carene (n = 4), 55 (9.7) for benzene (n = 34 (14)), 7.4 (21) for toluene (n = 11 (3)), 9.6 for styrene (n = 9), 9.9 (10) for m-xylene (n = 11 (8)), 13 for p-xylene (n = 7), 13 (13) for 1,3,5-TMB (n = 11 (8)), 11 for 1,2,4-TMB (n = 10), 4.5 for 1,2,3-TMB (n = 6), 15 (5.5) for methanol (n = 24 (4)), 32 (8.6) for ethanol (n = 26 (7)), 6.9 for i-propanol (n = 7), 23 for ethanethiol (n = 4), 4.2 (1.4) for tetrachloroethene (n = 31 (9)), 7.2 (5.9) for HCN (n = 47 (33)), 293 for isocyanic acid (n = 18), 1.2 for trimethylamine (n = 3), 47 (47) for acrylonitrile (n = 12 (9)), 15 (12) for formic acid (n = 35 (7)), 62 (28) for acetaldehyde (n = 50 (45)), 9.4 for propionaldehyde (n = 4), 37 for 2-ethylhexylaldehyde (n = 3), 23 (28) for acrolein (n = 13 (9)), 21 for acetone (n = 22), 5.2 for diethylether (n = 10), 6.8 for 2-ethoxyethanol (n = 10), 7.7 for 2-ethoxyethyl acetate (n = 20), 4.8 for butyl acetate (n = 8), 5.1 for methyl metacrylate (n = 9), 12 for MEK (n = 8), 2.0 for MIBK (n = 5), 2.7 for MTBE (n = 4), 0.37 (0.41) for COS (n = 16 (13)), 72 (40) for PH₃ (n = 28 (10)), and 1.1 for SF₆ (n = 10). As such, acetaldehyde, HCN, PH₃, tetrachloroethene, ethanol, benzene, COS, methanol, acetylene, and 1,3-butadiene, isocyanic acid, acrolein, and likely acetone and 2-ethoxyethyl acetate seem to be the most frequent admixing gases in the BCWH exhausts studied.

The third operation mode is qualitative analysis of residual spectra, as thoroughly described in both my previous papers. This method allowed to list proposals of additional, very interesting, admixing gases, many of which were likely first documented in the nature. They include neutral hydroxides of Ca, Mg, Al, Fe(II), Fe(III), Zn, Cu; nitrosyls and carbonyls of Ti, V, Mn, Fe, Ag, Mo, Fe, Cu; hydrides of Al, Cu, Zn, Ge, Mo, Sb, and Hg; nitriles, azo and related compounds (azacyclopropenylidene, dicyanoacetylene, cyanogen isocyanate, cyanogen N-oxide, diazomethyl radical, hydrogen isocyanide, isocyanic acid, m-hydroxybenzonitrile, phenylnitrene radical; 2,4,6-trinitrene-1,3,5-triazine); amines (methyl(nitrosomethyl)amine); hypobromous and hydroiodic acids; hydrocarbons and halocarbons (cyclohexene, dibenz[a,h]anthracene, difluorovinylidene, hexachlorobenzene, hexachloroethane, 5-methyl-1,3-didehydrobenzene, pentacene, phenanthrene, triphenylene); nitrosyl chloride and iodide, phosgene; organoboron compounds (fluoroisocyanatoborane) and compounds like CBrO and B₂O₂; organosulfurs (thiirene, thioacetaldehyde, thioxoethenylidyne radical), organophosphorus compounds (methylphosphine), and organosilicons (difluorosilane, disinale, silanenitrile, tribromosilane), organoiodine compounds (iodosomethane – an I³⁺-bearing compounds; iodocyanoacetylene), HAlCl₂, ClO₂ ^*, and dimeric NO, to mention some. Due to multiple coincidence possible these results should, however, be treated with care.

4. New in situ FTIR gas analysis results of the USCB heaps

Results presentation within this chapter has its main goal in enlarging the span of the knowledge on the concentration range of various (major and minor) components of the BCWH combustion gases, both by pFTIR and GC methods. Table 1 shows data from Czerwionka-Leszczyny (18, that is, 10 vents / vent zones from zone CLD and 8 from the CL one). Table 2 juxtaposes data for 10 additional, differently mineralized vents from the Radlin heap (RD), with that from a BCWH in Bytom (BTM, 7 vents / vent zones). Table 3, in turn, juxtaposed data for vents in a BCWH in Świętochłowice (SWC, 11 vents / vent zones), “Starzykowiec” heap in the Chwałowice part of Rybnik (RCH, 1 vent, surface and deep part), and “Ruda” heap in Zabrze-Biskupice (ZBB, 5 vents / vent zones). In total, data for additional 53 vents is reported. As in the case of the data presented in Kruszewski et al. [6, 12], gases were probed at the surface and from deeper parts of the vents, whenever possible. Temperatures were measured using an IR pyrometer.

Following are values describing maximum and geometric-mean concentrations of gaseous species as detected within fumarolic vents of the CLD, CL, RD, BTM, SWC, and ZBB sites (whole-series-maximums are underlined): H₂O, 18.12, 14.74; 7.30, 2.83;27.14, 23.04; 11.15, 9.83; 6.42, 4.68; 25.63, 23.19; CO₂, 2.85, 2.29; 27.00, 0.20; 29.89, 20.85; 8.12, 6.05;38.41, 33.89 [vol.%]; CO, 135, 110; 163, 9.4; 2430, 1002; 3590, 2675; 1090, 303;26700, 3257; NO,112, 96; 10, 6.4; 7.3, 7.3; −, −; 19, 15; −, −; NO₂, 44, 22; 368, 155; 2.0, 2.0;1430,1430; −, −; 66, 45; N₂O, 3.5, 2.3; 0.06, 0.02;4.4,4.4; 2.8, 2.8; 1.3, 1.3; −, −; NH₃, 21, 7.7; 30, 2.5; 19, 7.1;65, 55; 4.1, 2.4; 8.3, 8.3; SO₂, 120, 31;671, 25; 388, 160; 532, 202; 79, 40; 123, 123; HCl, 11, 2.4; 6.5, 0.58; 6.2, 3.6;19, 6.1; 8.4, 3.0; 5.9, 3.8; CCl₄, −, −; 6.6, 6.6;11, 6.5, 1.1, 1.1; 0.57, 0.15; 8.5, 6.8; HF, 0.62, 0.62; 0.03, 0.03; 0.12, 0.12;1.1, 0.36;1.1, 0.46; −, −; SiF₄, 6.3, 1.3; 31, 3.5; 21, 16; 3.2, 1.7;48, 4.6; 28, 19; AsH₃, 0.17, 0.09; 1.7, 0.38; 1.7, 0.75;3.4, 1.7; 0.40, 0.20; 2.9, 1.1; CH₄, 262, 107; 2950, 16;3470, 1238; 819, 491; −, −; 1130, 984; ethane, −, −; 30, 30; 142, 142;281,281; −, −; −, −; propane, 42, 15;729, 15; 601, 275; 694, 410; 215, 77; 277, 255; hexane, 11, 1.8; 152, 51; 139, 73;608, 225; −, −; 69, 48; ethene, 6.6, 3.2; 79, 6.9; 12, 6.0;84, 27; 26, 13; 23, 20; DCM, 141, 36;368, 69; 126, 47; 84, 46; 191, 51; 142, 82; 1,1-DCE, 7.2, 7.2; 17, 8.9; −, −; 16, 16;104, 67; −, −; 1,2-DCE, −, −;77,77; 39, 39; 38, 38; −, −; 60, 59; 1,1,1-TCE, 99, 46; 417, 26; 36, 25; 59, 11;492, 150; 65, 34; 1,2-DCP, 31, 31; 56, 56; 384, 159;568, 226; −, −; 214, 114; 1,1-DCEe, 77, 21;347, 67; 195, 123; 28, 17; 287, 66; 191, 132; vinyl chloride, −, −; −, −;416, 235; chlorobenzene, 39, 24; 186, 15; 77, 44;206, 81; 51, 18; 73, 70; cumene, 34, 16;399, 5.7; 126, 97; 264, 81; 66, 81; 153, 60; 153, 76; phenol, 29, 10; 7, 4.2; 51, 16;67, 41; 9.7, 2.8; 36, 23; o-cresol, 46, 5.8; 66, 3.6; 65, 36;81, 54; 13, 5.3; 63, 30; furan, 0.14, 0.14 (no records for other sites); THF, 1.3, 0.41; 177, 177; 96, 12;293, 261; −, −; 36, 29; thiophene, 192, 146; 173, 38; 556, 332;689, 241; 260, 143; 496, 397; formaldehyde, 12, 3.7; 13, 1.2; 5.5, 2.0;17, 2.3; 9.4, 3.0; 2.8, 1.9; acetic acid, −, −; −, −; 9.1, 9.1;50, 14; −, −; −, −; DMS, 62, 21; 893, 28; 401, 69;1540, 534; −, −; 153, 101; DMDS, 104, 28; 37, 21; −, −; −, −;380, 194; −, −; ad pyridine, 7.1, 7.1; 86, 7.3; −, −; −, −;232, 144; −, − [ppm]. As compared to these vents, the one at the RCH site. The geometric mean concentrations for the whole range are: H₂O 9.5, CO₂ 3.83 [vol.%], CO 350, NO 20, NO₂ 54, N₂O 0.51, NH₃ 7.5, SO₂ 72, HCl 2.5, CCl₄ 2.3, HF 0.26, SiF₄ 4.5, AsH₃ 0.53, methane 201, ethane 106, propane 58, hexane 29, ethene 11, DCM 54, 1,1-DCE 17, 1,2-DCE 53, 1,1,1-TCE 37, 1,2-DCP 127, 1,1-DCEe 60, vinyl chloride 165, chlorobenzene 30, cumene 36, phenol and o-cresol and THF 13, furan 0.14, thiophene 200, formaldehyde 2.2, acetic acid 13, DMS 65, DMDS 39, and pyridine 29.

5. Discussion

In general, the data provided for additional vents from additional BCWH probed allows to enlarge the span of the maximum observed values of only some compounds. They include (with excess in parentheses) CO (10x), SO₂, 1,1,1-TCE (12x), 1,1-DCEe (2.5x), cumene (2x), formaldehyde (3x), and pyridine (21x). Higher than previously observed geometric mean values are also observed for NO₂, CCl₄, ethane (2x), propane, ethene, and thiophene. This is clearly seen in the case of the latter two compounds, with more frequent positive determinations than within the previous studies. Similar levels of geometric means are found for HCl, AsH₃, chlorobenzene, phenol, and DMDS. As formerly observed, concentration ranges are usually extremely variable. Cumene is a good example of a compound with very high maximum but very low geometric mean. So is true, though less clearly, for, e.g., o-cresol. Some compounds often show large contents but single records. For many BCWHs there are large discrepancies between the geometric mean values and maximums, while for less number of the objects studied the amounts emitted are at very steady level. Some constituents, like vinyl chloride and even methane, may show very high concentrations (>100 ppm) but may be “absent” (below detection limits) at other BCWHs or vents. As explained in the former papers, this results from very high dynamics of the local combustion processes. The ex situ GC values obtained are, again, usually much lower than those observed by in situ FTIR, thus confirming their uncertain and, possibly, semi-quantitative value. On the other hand, two compounds not observed within the previous GC data are now determined: CH₃Cl (chloromethane or methyl chloride) and cyclopentane.

At the time of the BCWH gas analyses the author could not find paper showing the usage of FTIR for environmental studies. Stockwell et al. [27] used this method to measure H₂O, CO_x, NO_x, HCl, SO₂, NH₃, methane, acetylene, ethene, propane, formaldehyde, formic acid, methanol, acetic acid, HCN, furan, glycolaldehyde, and HONO (the latter also initially reported in [6]) in biomass emissions, though in a Fire Lab at Missoula Experiment. A more in situ type of work, engaging airborne FTIR, is by Yokelson et al. [28] who measured African savanna fires, with 14 compounds analyzed.

It is noteworthy that numerous organic and organo(semi)metallic compounds (or similar ones) detected in the BCWHs exhausts are also detected in volcanic fumaroles (mainly via GC, or modeled, as summarized by Wahrenberger [29]) or algal emissions (by GC–MS; [30]). Examples of interesting species include CO₂, COS, CS₂, S₂, S₈, SO₂, AsH₃, HCl, HF, HBr, CHCl₃, NO₂, propanal, methanol, acetaldehyde, 1,1,2-trichlorotrifluoroethane, hexafluoropropene, tetrachloroethene, vinyl chloride, i-butene, hexane, octane, octane, butadiene, benzene, toluene, α-pinene, i- and n-propanol, methylacrolein, MEK, acetone, 1,4-dioxane, dimethyldifluorosilane, thioformaldehyde, ethylthiophene, trimethylborane, methylphosphine, and uncertain [N-(phenyl-2-pyridinylmethylene)benzeneamine-N,N′]-irontricarbonyl and silver benzoate; geosmin, cyclopentane, cyclohexane, acetic acid, acetamide, glucopyranose, dibutyl phthalate, cholest-5-en-22-one, benzaldehyde, hydrazine, 8-amino-2-naphthalenol, ethanethioimide, thiourea, 1,3-oxathian-2-one, tetrahydro-2,5-dimethylthiophene, 6-methylbenzo[b]thiophene, 3,3,5,5,-tetramethyl-1,2,4-trithiolane, thiirane, C₂H₇O₂B borane, trimethylsilane, butytrimethylsilane, or undecanoic acid 11-chloro- and 11-fluorotrimethylsilyl esters.

Acknowledgments

This work was financed by the NCN (Narodowe Centrum Nauki, or National Science Centre) grant no. 2013/11/B/ST10/04960.