John Johansson

Measurements of industrial emissions of alkenes in Texas using the solar occultation flux method

Solar occultation flux (SOF) measurements of alkenes have been conducted to identify and quantify the largest emission sources in the vicinity of Houston and in SE Texas during September 2006 as part of the TexAQS 2006 campaign. The measurements have been compared to emission inventories and have been conducted in parallel with airborne plume studies. The SOF measurements show that the hourly gas emissions from the large petrochemical and refining complexes in the Houston Ship Channel area and Mount Belvieu during September 2006 corresponded to 1250 +/- 180 kg/h of ethene and 2140 +/- 520 kg/h of propene, with an estimated uncertainty of about 35%. This can be compared to the 2006 emission inventory value for ethene and propene of 145 +/- 4 and 181 +/- 42 kg/h, respectively. On average, for all measurements during the campaign, the discrepancy factor is 10.2(+ 8,-5) for ethene and 11.7(+ 7,-4) for propene. The largest emission source was Mount Belvieu, NE of the Houston Ship Channel, with ethene and propene emissions corresponding to 440 +/- 130 kg/h and 490 +/- 190 kg/h, respectively. Large variability of propene was observed from several petrochemical industries, for which the largest reported emission sources are flares. The SOF alkene emissions agree within 50% with emissions derived from airborne measurements at three different sites. The airborne measurements also provide support to the SOF error budget.

Emission measurements of alkenes, alkanes, SO2, and NO2 from stationary sources in Southeast Texas over a 5 year period using SOF and mobile DOAS

A mobile platform for flux measurements of VOCs (alkanes and alkenes), SO2, and NO2 emissions using the Solar Occultation Flux (SOF) method and mobile differential optical absorption spectroscopy (DOAS) was used in four different studies to measure industrial emissions. The studies were carried out in several large conglomerates of oil refineries and petrochemical industries in Southeast and East Texas in 2006, 2009, 2011, and 2012. The measured alkane emissions from the Houston Ship Channel (HSC) have been fairly stable between 2006 and 2011, averaging about 11,500kg/h, while the alkene emissions have shown greater variations. The ethene and propene emissions measured from the HSC were 1511kg/h and 878kg/h, respectively, in 2006, while dropping to roughly 600kg/h for both species in 2009 and 2011. The results were compared to annual inventory emissions, showing that measured VOC emissions were typically 5-15 times higher, while for SO2 and NO2 the ratio was typically 0.5-2. AP-42 emission factors were used to estimate meteorological effects on alkane emissions from tanks, showing that these emissions may have been up to 35-45% higher during the studies than the annual average. A more focused study of alkene emissions from a petrochemical complex in Longview in 2012 identified two upset episodes, and the elevation of the total emissions during the measurement period due to the upsets was estimated to be approximately 20%. Both meteorological and upset effects were small compared to the factor of 5-15, suggesting that VOC emissions are systematically and substantially underestimated in current emission inventories.

Quantitative measurements and modeling of industrial formaldehyde emissions in the Greater Houston area during campaigns in 2009 and 2011

A sensitive Mobile differential optical absorption spectroscopy (DOAS) system with real-time evaluation capability and HCHO detection limit of 3 ppb over 100 m has been developed. The system was operated together with a Solar Occultation Flux system for large-scale vertical flux measurements of HCHO, NO2, SO2, and VOCs in the Houston-Galveston-Brazoria area during two studies, in 2009 (Study of Houston Atmospheric Radical Precursors campaign) and in 2011 (Air Quality Research Program study). Both in 2009 and 2011, HCHO plumes from five separate local sources in Texas City, Mont Belvieu, and Houston Ship Channel (HSC) were repeatedly detected using Mobile DOAS with emissions varying between 6 and 40 kg/h. In many cases significant alkene emissions were detected simultaneously with the HCHO plumes. Furthermore, in 2011 two additional sources were observed in Texas City and in HSC, with 10 kg/h and 31 kg/h HCHO, respectively. A plume chemistry model was applied to 13 cases to investigate whether the detected HCHO was emitted directly from the industries or was produced by photochemical degradation of VOCs. The model results showed that on average 90% of the detected HCHO was of primary origin and the photochemical production contributed more than 10% in only three cases. Based on the repeatability, it is likely that the most significant HCHO sources in the area are included in this study with an overall emission of 120 kg/h. On a regional scale, this emission is small compared to the secondary HCHO formed from oxidation of reactive VOCs emitted from the same industries, estimated to be an order of magnitude higher.