Barbara Barletta

Mixing ratios of volatile organic compounds (VOCs) in the atmosphere of Karachi, Pakistan

Mixing ratios of carbon monoxide (CO), methane (CH4), non-methane hydrocarbons, halocarbons and alkyl nitrates (a total of 72 species) were determined for 78 whole air samples collected during the winter of 1998–1999 in Karachi, Pakistan. This is the first time that volatile organic compound (VOC) levels in Karachi have been extensively characterized. The overall air quality of the urban environment was determined using air samples collected at six locations throughout Karachi. Methane (6.3 ppmv) and ethane (93 ppbv) levels in Karachi were found to be much higher than in other cities that have been studied. The very high CH4 levels highlight the importance of natural gas leakage in Karachi. The leakage of liquefied petroleum gas contributes to elevated propane and butane levels in Karachi, although the propane and butane burdens were lower than in other cities (e.g., Mexico City, Santiago). High levels of benzene (0.3–19 ppbv) also appear to be of concern in the Karachi urban area. Vehicular emissions were characterized using air samples collected along the busiest thoroughfare of the city (M.A. Jinnah Road). Emissions from vehicular exhaust were found to be the main source of many of the hydrocarbons reported here. Significant levels of isoprene (1.2 ppbv) were detected at the roadside, and vehicular exhaust is estimated to account for about 20% of the isoprene observed in Karachi. 1,2-Dichloroethane, a lead scavenger added to leaded fuel, was also emitted by cars. The photochemical production of ozone (O3) was calculated for CO and the various VOCs using the Maximum Incremental Reactivity (MIR) scale. Based on the MIR scale, the leading contributors to O3 production in Karachi are ethene, CO, propene, m-xylene and toluene. r 2002 Elsevier Science Ltd. All rights reserved.

Source origins, modeled profiles, and apportionments of halogenated hydrocarbons in the greater Pearl River Delta region, southern China

[1] We analyze 16-month data of 13 major halocarbons measured at a southern China coastal site in the greater Pearl River Delta (PRD). A total of 188 canister air samples were collected from August 2001 to December 2002. Overall inspection indicated that CH2Cl2 ,C 2Cl4, and C2HCl3 had similar temporal variations while CFC-11, CFC-12, and CFC-113 showed the same emission patterns during the sampling period. Diurnal variations of halocarbons presented different patterns during ozone episode days, mainly related to emission strength, atmospheric dispersion, and photochemical lifetimes. For further statistics and source appointment, Lagrangian backward particle release simulations were conducted to help understand the potential source regions of all samples and classify them into different categories, including local Hong Kong, inner PRD, continental China, and marineairmasses.WiththeexceptionofHCFC-142b,themixingratiosofallhalocarbonsin marine air were significantly lower than those in urban and regional air (p < 0.01), whereas no significant difference was found between urban Hong Kong and inner PRD regional air, reflecting the dominant impact of the greater PRD regional air on the halocarbon levels. Thehalocarbonlevelsinthisregionweresignificantlyinfluencedbyanthropogenicsources, causing the halocarbon mixing ratios in South China Sea air to be higher than the corresponding background levels, as measured by global surface networks and by airborne missions such as Transport and Chemical Evolution Over the Pacific. Interspecies correlation analysis suggests that CHCl3 is mainly used as a solvent in Hong Kong but mostly as a feedstock for HCFC-22 in the inner PRD. Furthermore, CH3Cl is often used as a refrigerant and emitted from biomass/biofuel burning in the inner PRD. A positive matrix factorization receptor model was applied to the classified halocarbon samples in the greater PRD for source profiles and apportionments. Seven major sources were identified and quantified. Emissions from solvent use were the most significant source of halocarbons (71 ± 9%), while refrigeration was the second largest contributor (18 ± 2%). By further lookingatsamplesfromtheinnerPRDandfromurbanHongKongseparately,wefoundthat more solvent was used in the dry cleaning industry in Hong Kong, whereas the contribution of cleaning solvent in the electronic industry was higher in the inner PRD. Besides the two common sources of solvent use and refrigeration, the contributions of biomass/biofuel burning and feedstock in chemical manufacturing was remarkable in the inner PRD but negligible in Hong Kong. These findings are of help to effectively control and phase out the emissions of halocarbons in the greater PRD region of southern China.

Determination of toxic nitrophenols in the atmosphere by high-performance liquid chromatography

Abstract Seven HPLC columns were used for the optimization of the isocratic HPLC measurement of phenol, nitro- and dinitrophenols. A column constituted from 5 μm particles (100 A) of silica-based C 18 material was used for the analysis. Good separation of the analytes and their quantification in samples from the nitration of phenol in liquid and in gas phase in the laboratory was obtained. This approach allowed also to determine phenol in air samples.

Characteristics of nonmethane hydrocarbons (NMHCs) in industrial, industrial-urban, and industrial-suburban atmospheres of the Pearl River Delta (PRD) region of south China

Author(s): Chan, LY; Chu, KW; Zou, SC; Chan, CY; Wang, XM; Barletta, B; Blake, DR; Guo, H; Tsai, WY | Abstract: In a study conducted in late summer 2000, a wide range of volatile organic compounds (VOCs) were measured throughout five target cities in the Pearl River Delta (PRD) region of south China. Twenty-eight nonmethane hydrocarbons (NMHCs; 13 saturated, 9 unsaturated, and 6 aromatic) are discussed. The effect of rapid industrialization was studied for three categories of landuse in the PRD: Industrial, industrial-urban, and industrial-suburban. The highest VOC mixing ratios were observed in industrial areas. Despite its relatively short atmospheric lifetime (2-3 days), toluene, which is largely emitted from industrial solvent use and vehicular emissions, was the most abundant NMHC quantified. Ethane, ethene, ethyne, propane, n-butane, i-pentane, benzene, and m-xylene were the next most abundant VOCs. Direct emissions from industrial activities were found to greatly impact the air quality in nearby neighborhoods. These emissions lead to large concentration variations for many VOCs in the five PRD study cities. Good correlations between isoprene and several short-lived combustion products were found in industrial areas, suggesting that in addition to biogenic sources, anthropogenic emissions may contribute to urban isoprene levels. This study provides a snapshot of industrial, industrial-urban, and industrial-suburban NMHCs in the five most industrially developed cities of the PRD. Increased impact of industrial activities on PRD air quality due to the rapid spread of industry from urban to suburban and rural areas, and the decrease of farmland, is expected to continue until effective emission standards are implemented. Copyright 2006 by the American Geophysical Union.

Source attributions of hazardous aromatic hydrocarbons in urban, suburban and rural areas in the Pearl River Delta (PRD) region

Aromatic hydrocarbons (AHs) are both hazardous air pollutants and important precursors to ozone and secondary organic aerosols. Here we investigated 14 C6-C9 AHs at one urban, one suburban and two rural sites in the Pearl River Delta region during November-December 2009. The ratios of individual aromatics to acetylene were compared among these contrasting sites to indicate their difference in source contributions from solvent use and vehicle emissions. Ratios of toluene to benzene (T/B) in urban (1.8) and suburban (1.6) were near that of vehicle emissions. Higher T/B of 2.5 at the rural site downwind the industry zones reflected substantial contribution of solvent use while T/B of 0.8 at the upwind rural site reflected the impact of biomass burning. Source apportionment by positive matrix factorization (PMF) revealed that solvent use, vehicle exhaust and biomass burning altogether accounted for 89-94% of observed AHs. Vehicle exhaust was the major source for benzene with a share of 43-70% and biomass burning in particular contributed 30% to benzene in the upwind rural site; toluene, C8-aromatics and C9-aromatics, however, were mainly from solvent use, with contribution percentages of 47-59%, 52-59% and 41-64%, respectively.

Evidence of mixing between polluted convective outflow and stratospheric air in the upper troposphere during DC3

Aircraft measurements, including non-methane hydrocarbons (NMHCs), long-lived halocarbons, carbon monoxide (CO), and ozone (O3) collected on board the NASA DC-8 during the Deep Convection, Clouds, and Chemistry (DC3) field campaign (May – June 2012), were used to investigate interactions and mixing between stratospheric intrusions and polluted air masses. Stratospherically influenced air masses were detected using a suite of long-lived halocarbons, including chlorofluorocarbons (CFCs) and HCFCs, as a tracer for stratospheric air. A large number of stratospherically influenced samples were found to have reduced levels of O3 and elevated levels of CO (both relative to background stratospheric air), indicative of mixing with anthropogenically influenced air. Using n-butane and propane as further tracers of anthropogenically influenced air, we show that this type of mixing was present both at low altitudes and in the upper troposphere (UT). At low altitudes, this mixing resulted in O3 enhancements consistent with those reported at surface sites during deep stratospheric intrusions, while in the UT, two case studies were performed to identify the process by which this mixing occurs. In the first case study, stratospheric air was found to be mixed with aged outflow from a convective storm, while in the second case study, stratospheric air was found to have mixed with outflow from an active storm occurring in the vicinity of a stratospheric intrusion. From these analyses, we conclude that deep convective events may facilitate the mixing between stratospheric air and polluted boundary layer air in the UT. Throughout the entire DC3 study region, this mixing was found to be prevalent: 72% of all samples that involve stratosphere-troposphere mixing show influence of polluted air. Applying a simple chemical kinetics analysis to these data, we show that during DC3, the instantaneous production of hydroxyl radical (OH) in these mixed stratospheric-polluted air masses was 11 ± 8 times higher than that of stratospheric air, and 4.2 ± 1.8 times higher than that of background upper tropospheric air.

Air Quality in Mecca and Surrounding Holy Places in Saudi Arabia During Hajj: Initial Survey

The Arabian Peninsula experiences severe air pollution, the extent and sources of which are poorly documented. Each year in Saudi Arabia this situation is intensified during Hajj, the Holy Pilgrimage of Islam that draws millions of pilgrims to Mecca. An initial study of air quality in Mecca and surrounding holy sites during the 2012 Hajj (October 24-27) revealed strongly elevated levels of the combustion tracer carbon monoxide (CO, up to 57 ppmv) and volatile organic compounds (VOCs) along the pilgrimage route-especially in the tunnels of Mecca-that are a concern for human health. The most abundant VOC was the gasoline evaporation tracer i-pentane, which exceeded 1200 ppbv in the tunnels. Even though VOC concentrations were generally lower during a follow-up non-Hajj sampling period (April 2013), many were still comparable to other large cities suffering from poor air quality. Major VOC sources during the 2012 Hajj study included vehicular exhaust, gasoline evaporation, liquefied petroleum gas, and air conditioners. Of the measured compounds, reactive alkenes and CO showed the strongest potential to form ground-level ozone. Because the number of pilgrims is expected to increase in the future, we present emission reduction strategies to target both combustive and evaporative fossil fuel sources.

Ambient CFCs and HCFC‐22 observed concurrently at 84 sites in the Pearl River Delta region during the 2008–2009 grid studies

Air samples were collected concurrently at 05:00 A.M. and 10:00 A.M. local Beijing time (geomagnetic time + 8) at 84 sites during two grid-study campaigns on 29 September 2008 and 1 March 2009 in the Pearl River Delta region, in order to offer snapshots of ambient CFCs and hydrochlorofluorocarbons (HCFCs) in different seasons and to indicate the presence of local emission sources. Compared to the subtropical northern hemisphere background levels, mean mixing ratios of CFC-11, CFC-12, CFC-113, CFC-114, and HCFC-22 were enhanced by 7%–11%, 8%–11%, 5%–6%, 8%–9%, and 71%–135%, respectively. When data from this tudy were pooled together with previous observations in the region, ambient CFC-11, CFC-12, and CFC-113 unambiguously showed declines in mixing ratios, while HCFC-22 showed an increase. Spatial variations revealed potential emission hot spots in the region, and levels of CFCs and HCFC-22 were higher in September than in March due to many more refrigeration and air-conditioning activities during summer. Source apportioning by positive matrix factorization revealed that new input of CFCs and HCFC-22 into the ambient air was largely attributed to emission from air-conditioning and refrigerating activities instead of industry activities. Average emissions in the region estimated by the CO-tracer method were 0.8 ± 0.2, 1.4 ± 0.6, 0.2 ± 0.1, 0.1 ± 0.02, and 4.4 ± 1.0 Gg/yr for CFC-11, CFC-12, CFC-113, CFC-114, and HCFC-22, respectively, and they accounted for 5.5%–25.5% of the total estimated CFC and HCFC-22 emissions in China.

Stable isotope profiles reveal active production of VOCs from human-associated microbes.

Volatile organic compounds (VOCs) measured from exhaled breath have great promise for the diagnosis of bacterial infections. However, determining human or microbial origin of VOCs detected in breath remains a great challenge. For example, the microbial fermentation product 2,3-butanedione was recently found in the breath of Cystic Fibrosis (CF) patients; parallel culture-independent metagenomic sequencing of the same samples revealed that Streptococcus and Rothia spp. have the genetic capacity to produce 2,3-butanedione. To investigate whether the genetic capacity found in metagenomes translates to bacterial production of a VOC of interest such as 2,3-butanedione, we fed stable isotopes to three bacterial strains isolated from patients: two gram-positive bacteria, Rothia mucilaginosa and Streptococcus salivarius, and a dominant opportunistic gram-negative pathogen, Pseudomonas aeruginosa. Culture headspaces were collected and analyzed using a gas chromatographic system to quantify the abundance of VOCs of interest; mass spectroscopy was used to determine whether the stable isotope label had been incorporated. Our results show that R. mucilaginosa and S. salivarius consumed D-Glucose-13C6 to produce labeled 2,3-butanedione. R. mucilaginosa and S. salivarius also produced labeled acetaldehyde and ethanol when grown with 2H2O. Additionally, we find that P. aeruginosa growth and dimethyl sulfide production are increased when exposed to lactic acid in culture. These results highlight the importance VOCs produced by P. aeruginosa, R. mucilaginosa, and S. salivarius as nutrients and signals in microbial communities, and as potential biomarkers in a CF infection.

OH reactivity in urban and suburban regions in Seoul, South Korea – an East Asian megacity in a rapid transition

South Korea has recently achieved developed country status with the second largest megacity in the world, the Seoul Metropolitan Area (SMA). This study provides insights into future changes in air quality for rapidly emerging megacities in the East Asian region. We present total OH reactivity observations in the SMA conducted at an urban Seoul site (May-June, 2015) and a suburban forest site (Sep, 2015). The total OH reactivity in an urban site during the daytime was observed at similar levels (∼15 s(-1)) to those previously reported from other East Asian megacity studies. Trace gas observations indicate that OH reactivity is largely accounted for by NOX (∼50%) followed by volatile organic compounds (VOCs) (∼35%). Isoprene accounts for a substantial fraction of OH reactivity among the comprehensive VOC observational dataset (25-47%). In general, observed total OH reactivity can be accounted for by the observed trace gas dataset. However, observed total OH reactivity in the suburban forest area cannot be largely accounted for (∼70%) by the trace gas measurements. The importance of biogenic VOC (BVOCs) emissions and oxidations used to evaluate the impacts of East Asian megacity outflows for the regional air quality and climate contexts are highlighted in this study.