Measured Hydrocarbon Concentrations Research Articles

Spatio-temporal variation of the microbial community of the coast of Lebanon in response to petroleum hydrocarbon pollution

In this study, the coast of Lebanon was analyzed for the dynamic changes in sediment microbial communities in response to a major petroleum oil spill and tar contamination that occurred in the summer of 2021. Spatio-temporal variations in the microbial structure along the shores of Lebanon were assessed in comparison to baseline microbial structure determined in 2017. Microbial community structure and diversity were determined using Illumina MiSeq technology and DADA2 pipeline. The results show a significant diversity of microbial populations along the Lebanese shore, and a significant change in the sediment microbial structure within four years. Namely, Woeseia, Blastopirellula, and Muriicola were identified in sediment samples collected in year 2017, while a higher microbial diversity was observed in 2021 with Woeseia, Halogranum, Bacillus, and Vibrio prevailing in beach sediments. In addition, the results demonstrate a significant correlation between certain hydrocarbon degraders, such as Marinobacter and Vibrio, and measured hydrocarbon concentrations.

Weathering of Oil in a Surficial Aquifer

The composition of crude oil in a surficial aquifer was determined in two locations at the Bemidji, MN, spill site. The abundances of 71 individual hydrocarbons varied within 16 locations sampled. Little depletion of these hydrocarbons (relative to the pipeline oil) occurred in the first 10 years after the spill, whereas losses of 25% to 85% of the total measured hydrocarbons occurred after 30 years. The C6-30 n-alkanes, toluene, and o-xylene were the most depleted hydrocarbons. Some hydrocarbons, such as the n-C10-24 cyclohexanes, tri- and tetra- methylbenzenes, acyclic isoprenoids, and naphthalenes were the least depleted. Benzene was detected at every sampling location 30 years after the spill. Degradation of the oil led to increases in the percent organic carbon and in the δ 13 C of the oil. Another method of determining hydrocarbon loss was by normalizing the total measured hydrocarbon concentrations to that of the most conservative analytes. This method indicated that the total measured hydrocarbons were depleted by 47% to 77% and loss of the oil mass over 30 years was 18% to 31%. Differences in hydrocarbon depletion were related to the depth of the oil in the aquifer, local topography, amount of recharge reaching the oil, availability of electron acceptors, and the presence of less permeable soils above the oil. The results from this study indicate that once crude oil has been in the subsurface for a number of years there is no longer a "starting oil concentration" that can be used to understand processes that affect its fate and the transport of hydrocarbons in groundwater.

Multimedia fate of petroleum hydrocarbons in the soil: Oil matrix of constructed biopiles

A dynamic multimedia fugacity model was used to evaluate the partitioning and fate of petroleum hydrocarbon fractions and aromatic indicator compounds within the soil: oil matrix of three biopiles. Each biopile was characterised by four compartments: air, water, soil solids and non-aqueous phase liquid (NAPL). Equilibrium partitioning in biopile A and B suggested that most fractions resided in the NAPL, with the exception of the aromatic fraction with an equivalent carbon number from 5 to 7 (EC 5−7). In Biopile C, which had the highest soil organic carbon content (13%), the soil solids were the most important compartment for both light aliphatic fractions (EC 5−6 and EC 6−8) and aromatic fractions, excluding the EC 16−21 and EC 21−35. Our starting hypothesis was that hydrocarbons do not degrade within the NAPL. This was supported by the agreement between predicted and measured hydrocarbon concentrations in Biopile B when the degradation rate constant in NAPL was set to zero. In all scenarios, biodegradation in soil was predicted as the dominant removal process for all fractions, except for the aliphatic EC 5−6 which was predominantly lost via volatilization. The absence of an explicit NAPL phase in the model yielded a similar prediction of total petroleum hydrocarbon (TPH) behaviour; however the predicted concentrations in the air and water phases were significantly increased with consequent changes in potential mobility. Further comparisons between predictions and measured data, particularly concentrations in the soil mobile phases, are required to ascertain the true value of including an explicit NAPL in models of this kind.

Airborne NMHC measurements under various pollution conditions

Traffic is one of the main emission sources of non-methane hydrocarbons (NMHC), which play a key role in the formation of ozone. Over the last years, airborne measurements of non-methane hydrocarbons have been performed with an on-line gas chromatograph over large cities such as Vienna and Milano, the polluted Lombardy region and moderately polluted regions such as the Swiss Plateau and alpine areas. This set of data has been analysed with respect to pollution level, composition, reactivity and contribution of emission sources in the different areas. The measured hydrocarbon concentrations coincide with the emission strengths given by the emission inventories of the respective regions. The alpine Mesolcina valley south of the Alps is strongly influenced by advected air polluted with hydrocarbons. The relative concentration of individual species to the sum of the measured hydrocarbons is similar in all regions, but show a few peculiarities specific to some regions.

Measurements of cycle resolved air-fuel ratio near the spark plug in a spark ignition engine

Mixture preparation is a key contributor to both the combustion and emissions of the automotive gasoline engine. The air-fuel ratio near the spark plug may have an effect on combustion characteristics, especially at low load, since it is related to flame development. Therefore, measurements of the cycle-resolved equivalence ratio near the spark plug are particularly important for a better understanding of their contribution to combustion and emissions. This paper describes how the in-cylinder equivalence ratio was determined from the measured hydrocarbon concentrations near the spark plug using a fast response flame ionization detector (FRFID). The procedures established were then applied to a limited range of engine operating conditions, and the cycle-resolved equivalence ratio near the spark plug was determined from the measured hydrocarbon concentration. The results showed that with premixed propane fuel the cyclic variation in equivalence ratio near the spark plug was quite small and corresponded to the overall equivalence ratio from the universal exhaust gas oxygen (UEGO) sensor signal. However, with gasoline fuel the equivalence ratio near the spark plug varied by up to 10 per cent and did not coincide with the UEGO sensor signal on a cyclic basis. The variation in equivalence ratio near the spark plug affected the heat release rate, which in turn affected the indicated mean effective pressure (i.m.e.p.). The equivalence ratio excursions and its effects during acceleration and deceleration are strongly related to the exhaust emissions, fuel economy and so on. With this in mind, the quantitative measurement method using the measured hydrocarbon concentrations was studied for detailed analysis during transient conditions. It was also observed that cyclic variation in the equivalence ratio near the spark plug might be one cause of cycle-by-cycle variation.

Estimation of Hydrocarbon Oxidation by Measuring He Concentrations in an SI Engine Exhaust Port

In order to investigate the exhaust structure and secondary oxidation of unburned hydrocarbon (HC) in the exhaust port, concentrations of individual HC species were measured in exhaust process, the degree of oxidation were obtained. Using a solenoid-driven fast sampling system on single-cylinder research engine fueled with 94% propane, the profiles of unburned hydrocarbons (HCs) and non-fuel HCs with a propane fueled engine were obtained from several locations in the exhaust port during the exhaust process. The sampled gases were analyzed using a gas chromatography of HC species with 4 or lesser carbon atoms. The change of total HC concentration and HC fractions of major components through the exhaust port were discussed. The results showed that non-uniform distribution of HC concentration existed around the exhaust valve and changed with time, and that the exhaust gas exhibited nearly uniform concentration profile at port exit, which was due to mixing and oxidation. Also it could be known that bulk gas with relatively high HC concentration came out through the bottom of the exhaust valve. To estimate the mass-based degree of HC oxidation in the exhaust port from measured HC concentrations, a 3-zone diagnostic cycle simulation and plug flow modeling were used. The degree of oxidation ranged between 26 % and 36 % corresponding to the engine operation conditions

Benzene exposures caused by traffic in Munich public transportation systems between 1993 and 1997

Volatile aromatics (benzene, toluene, xylenes, the BTX-aromatics) were measured between 1993 and 1997 in buses and trams in Munich center and along main roads during regular rides. The sampling time was between 07.00 and 00.00 h. A total of 631 probes were sampled and centrally analyzed. In the mean of 5 years we found 15.0 μg benzene/m 3, 50% above the limit of the 23. BImSchV and 107.5 μg BTX aromates/m 3 along the strongly traffic loaded main streets. Splitting up these mean emissions into single years we observed a trend toward a decline of mean immission of all volatile aromatics (benzene from 23.8 μg/m 3 to 7.4 μg/m 3) and the sum of BTX aromatics (from 147.5 μg/m 3 to 59.4 μg/m 3). The measured hydrocarbon concentrations in Munich center were consistent with the long range theoretical calculations concerning the decrease of traffic-caused benzene immissions in cities. If the current trends continue, we can expect benzene concentrations to be below 5 μg/m 3 by the year 2001 and below 2.5 μg/m 3 by the year 2008. At these levels, the carcinogenic risk from benzene is probably less significant than the risks to public health from other car exhaust components.

Measurement of hydrocarbon fuel concentration by means of infrared absorption technique with 3.39 ?m HeNe laser

The infrared absorption technique with a 3.39 μm HeNe laser is useful for measuring hydrocarbon concentrations. First, molar absorption coefficients of propane or methane for the 3.39 μm wavelength were investigated in the temperature range of 285–420 K and in the pressure range of 100–800 kPa. It was found that the molar absorption coefficient, ϵ, is independent of temperature, and that pressure has little effect on ϵ in propane, but a strong effect in methane. Second, by applying this technique to a spark ignition engine, the fuel concentration in the vicinity of a spark plug and the hydrocarbon concentration in the exhaust pipe were measured under the c conditions of no residual gas and homogeneous mixture. For the lean mixture, although cycle-to-cycle fluctuation of the fuel concentration was very small, the fluctuation of pressure in the cylinder was large.

In-Cylinder Measurements of Wall Layer Hydrocarbons in a Spark Ignited Engine

Abstract The hydrocarbon emissions process for the conventional, spark ignited, IC engine has been studied experimentally using a rapid acting gas sampling valve mounted in the combustion chamber wall. The sampling valve was electrohydraulically actuated. Design of the valve specifically allowed sampling in the vicinity of the wall quench layer with minimum leakage and crevice contributions to the measured hydrocarbon concentrations. Experimental results presented give substantial evidence that hydrocarbons remaining in a wall quench layer are not a major source of exhaust hydrocarbon emissions. Measurements of species concentrations as a function of time in the cycle and sample flow rate indicate that after flame arrival and quenching at the cold walls, hydrocarbons in the quench layer are rapidly and extensively oxidized within 2 msec. By use of an analytical model for the gas flow profile into the sampling valve, conservative upper limit calculations have been made of the quench layer contribution to t...

Inputs and fates of petroleum hydrocarbons in a subtropical marine estuary

Inputs and fates of petroleum from a higly urbanized area to a subtropical marine estuary were investigated by measuring hydrocarbon concentrations in municipal wastewater treatment plants, urban stormwater drains, sediments, and benthic organisms in and around Tampa Bay, FL. The concentrations of petroleum hydrocarbons discharged from secondary and tertiary treatment plants in this area were lower than concentrations previously reported for other treatment plants in temperate regions. Samples collected from urban storm drains under base flow conditions were also low. The generally low levels of petroleum hydrocarbons in the sediments and organisms throughout Tampa Bay suggest that the bay is relatively pristine with respect to petroleum hydrocarbon contamination. Since it is unlikely that the anthropogenic input of hydrocarbons to this estuary is significantly lower than in other urbanized areas, we suggest that elevated annual temperatures in this subtropical system result in increased metabolic rates of microorganisms and more rapid degradation or metabolism of the petroleum hydrocarbons.