Levels Of Non-methane Hydrocarbons Research Articles

Correlation between air temperature and surface ozone in their extreme ranges in the greater Tokyo region

High-level ozone (O3) events observed around major urban regions in the middle latitudes are correlated with high temperatures (T-O3 correlation). Therefore, the effects of global warming on the future O3 levels are a matter of concern. The T-O3 correlation is caused by various physicochemical and meteorological processes, the importance of which can differ by region. This statistical analysis focused on the correlation in the extremely high ranges, because the lower ranges would only act as noise in elucidating the conditions at which high temperatures and high levels of O3 occur. This methodology was applied to the greater Tokyo region after 2001, where severe O3 events frequently occurred when the sea breeze system developed in summer. To select sample days for the analysis, this study set up twofold filtering: (1) a large threshold for midday sunshine duration and (2) a typical variation pattern to roughly judge sea breeze days, mostly essential weather pattern for high-level O3 events in the region. The most notable result was a decrease in O3 corresponding to the reduction in non-methane hydrocarbons (NMHC) from Period I (2001–2007) to Period III (2017–2019). As the NMHC rank reduced, the linear regression line for the T-O3 correlation shifted downward, but its slope (ppb/°C) remained around 10, except that temporary spikes in O3 levels and temperatures occurred at moderate NMHC levels. From an urban meteorological perspective, the wind speed in the mature stage of the sea breeze is the major factor behind the T-O3 correlation.

Seasonal dependency of the atmospheric oxidizing capacity of the marine boundary layer of Bermuda

In this study, we investigate the atmospheric oxidation capacity in the marine boundary layer during two measurement campaigns in spring and summer 2019 at the Tudor Hill Marine Atmospheric Observatory, Bermuda. Measured species included non-methane hydrocarbons (NMHCs), HONO, HNO3, particulate matter, particulate nitrates, NO, NO2, O3, in addition to the meteorological parameters. Measured concentrations of all species were generally higher in spring than in summer. During the spring and summer, OH initiation sources made 61% and 42% of the total OH production rate (POH) during the daytime, respectively. The higher levels of NMHCs and OH production from ozone photolysis lead to a higher oxidation rate of NMHCs in the spring compared to summer. However, the low NO in the spring and summer leads to inefficient recycling of RO2 and HO2 to OH, with HO2 reaction with NO accounting for only 22% and 42% of POH during spring and summer. Sensitivity analysis suggests that OH reactivity in the MBL can be potentially enhanced by an oceanic source rather than a secondary oxidation product. Including halogen monoxides, BrO and IO were found to decrease HO2 by ∼14 and 18% during spring and summer, respectively, with marginal impact on OH due to the higher loss by aerosol uptake. The results demonstrate the complex multiphase HOx-Halogen chemistry and call for a more comprehensive multiphase investigation.

Characterizing methane and total non-methane hydrocarbon levels in Los Angeles communities with oil and gas facilities using air quality monitors.

Over the past decade, sensor networks have been proven valuable to assess air quality on highly localized scales. Here we leverage innovative sensors to characterize gaseous pollutants in a complex urban environment and evaluate differences in air quality in three different Los Angeles neighborhoods where oil and gas activity is present. We deployed monitors across urban neighborhoods in South Los Angles adjacent to oil and gas facilities with varying levels of production. Using low-cost sensors built in-house, we measured methane, total non-methane hydrocarbons (TNMHCs), carbon monoxide, and carbon dioxide during three deployment campaigns over four years. The multi-sensor linear regression calibration model developed to quantify methane and TNMHCs offers up to 16% improvement in coefficient of determination and up to a 22% reduction in root mean square error for the most recent dataset as compared to previous models. The deployment results demonstrate that airborne methane concentrations are higher within a 500 m radius of three urban oil and gas facilities, as well as near a natural gas distribution pipeline, likely a result of proximity to sources. While there are numerous additional sources of TNMHCs in complex urban environments, some sites appear to be larger emitters than others. Significant methane emissions were also measured at an idle site, suggesting that fugitive emissions may still occur even if production is ceased. Episodic spikes of both compounds suggested an association with oil and gas activities, demonstrating how sensor networks can be used to elucidate community-scale sources and differences in air quality moving forward.

Impact of COVID-19 lockdown on ambient levels and sources of volatile organic compounds (VOCs) in Nanjing, China

A lot of restrictive measures were implemented in China during January–February 2020 to control rapid spread of COVID-19. Many studies reported impact of COVID-19 lockdown on air quality, but little research focused on ambient volatile organic compounds (VOCs) till now, which play important roles in production of ozone and secondary organic aerosol. In this study, impact of COVID-19 lockdown on VOCs mixing ratios and sources were assessed based on online measurements of VOCs in Nanjing during December 20, 2019-Feburary 15, 2020 (P1-P2) and April 15–May 13, 2020 (P3). Average VOCs levels during COVID-19 lockdown period (P2) was 26.9 ppb, about half of value for pre-lockdown period (P1). Chemical composition of VOCs also showed significant changes. Aromatics contribution during decreased from 13% during P1 to 9% during P2, whereas alkanes contribution increased from 64% to 68%. Positive matrix factorization (PMF) was then applied for non-methane hydrocarbons (NMHCs) sources apportionment. Five sources were identified, including a source related to transport and background air masses, three sources related to petrochemical industry or chemical industry (petrochemical industry#1-propene/ethene, petrochemical industry#2-C7-C9 aromatics, and chemical industry-benzene), and a source attributed to gasoline evaporation and vehicular emission. During P2, NMHCs levels from petrochemical industry#2-C7-C9 aromatics showed the largest relative decline of 94%, followed by petrochemical industry#1-propene/ethene (67%), and gasoline evaporation and vehicular emission (67%). Furthermore, ratios of OH reactivity of NMHCs versus NO2 level (ROH,NMHCs/NO2) and total oxidant production rate (P (OX)) were calculated to assess potential influences of COVID-19 lockdown on O3 formation.

Ambient Non-Methane Hydrocarbons (NMHCs) Measurements in Baoding, China: Sources and Roles in Ozone Formation

Ambient non-methane hydrocarbons (NMHCs) are important precursors of ozone (O3) and secondary organic aerosol (SOA). Online and offline measurements of NMHCs were conducted during September 2015 in Baoding, Hebei province of China, in order to investigate their sources and roles in ozone formation. Average levels of total NMHCs online measured at the urban site were 44.5 ± 26.7 ppb. Aromatics was the largest contributor to NMHCs levels and OH reactivity, with fraction of 27.1% and 35.9%, respectively. Based on offline measurements at eight sites, we found that toluene, ethylbenzene, and m,p-xylene displayed the highest level at the site close to automobile manufacturing factories, followed by downwind receptor sites and other sites. Positive matrix factorization (PMF) model was then used to analyze NMHCs sources. Four factors were identified, including traffic-related emission, automobile manufacturing coating, biogenic emission, and NG/LPG usage and background. Average relative contribution of automobile manufacturing coating to NMHCs levels during the entire online measurement period was 33.4%, and this value increased to 42% during two O3 pollution days. Sensitivity of O3 formation to NMHCs and NOX during an O3 pollution episode were analyzed using a box model based on observations. Relative incremental reactivity (RIR) results suggested that O3 formation was in NOx-titration regime (i.e., highly NMHCs-limited regime). Further scenario analyses on relationship of O3 formation with reduction of NOx and anthropogenic NMHCs (AHC) indicated that AHC and NOx should be reduced by a ratio greater than two and three to achieve 5% and 10% O3 control objectives, respectively. The largest RIR value for anthropogenic NMHC species was from xylenes, which were also an important contributor to SOA formation and dominantly from sources related to automobile manufacturing coating and traffic emission. This means reducing NMHCs emission from automobile manufacturing coating and traffic emission should be given priority for synergetic control of O3 and PM2.5.

Evaluation of indoor and outdoor air quality in university academic buildings and associated health risk

ABSTRACT Air pollution is associated with several detrimental health conditions. This study assessed comfort parameters, priority air pollutants, hydrogen sulphide (H2S), non-methane hydrocarbons (NMHCs), and volatile organic compounds (VOCs) in natural science departments in a university to understand their role in air pollutant concentrations in university environments and associated health risks. Levels of air pollutants in the departments varied. High CO2 concentrations existed in all departments with highest levels of NMHC and VOC observed in the biochemistry, microbiology and biotechnology (BMBT) department. Highest Air quality index value of 111.3 was recorded for NO2 in the BMBT department. Health risk associated with exposure to these pollutants was highest for occupants in the physiology, followed by the biodiversity, and finally BMBT department. Natural science departments seem to contribute significant amounts of H2S, NO2, NMHCs and TVOCs in university campuses. Additional ventilation and frequent monitoring of air quality in these departments are recommended.

Mind the price gap: How optimal emission pricing relates to the EU CO2 reduction targets

From the transport economic literature, it is known that optimal pricing of (environmental) externalities improves the urban system. In contrast to theory-based optimal pricing strategies, real-world policy setting often follows so-called “backcasting” approaches where certain targets are set, and policy measures are implemented in order to reach those targets. An example for the latter approach is the EU goal to reduce global greenhouse gas emissions in the transport sector by 20% until 2020 with respect to 1990 levels. This article aims to (i) compare optimal pricing and backcasting approaches for a specific case study in a simulation environment by identifying the contribution of each approach in EU’s 2020 emission reduction target, and (ii) to determine the costs required to reach the desired targets. For this purpose, an optimal emission pricing strategy is applied to a real-world scenario of the Munich metropolitan area in Germany. The highly differentiated tolls relate to individual exhaust emissions, i.e. they are calculated using damage cost estimates from the literature and vary over time of day, with traffic situation, and with vehicle type. The results indicate that the desired reduction in CO2 emissions is not reached for optimal pricing approach, and that the initial damage costs estimates need to be multiplied by a factor of 5 in order to reach the target, yielding a price of 350 CO2. When aiming at a decrease of the overall emission costs by 20% (CO2 and local pollutants), the initial cost estimates need to be multiplied by a factor of 10. Furthermore, it is shown that the major contribution to the overall emission reduction stems from behavioral changes of commuters and reverse commuters rather than from urban travelers; under some circumstances, urban travelers even increase their CO2 emission levels. Hence, the study rises awareness that conflicting trends for different types of pollutants and different types of individuals are very likely: an increase in non-methane hydrocarbon levels for urban travelers and freight depicts that pricing emissions does not necessarily result in a reduction of all pollutants or of the emissions levels of all travelers. It is shown how agent-based simulations can be used to provide valuable insights and decision support in such possibly counter-intuitive situations.

Evaluation of the effectiveness of air pollution control measures in Hong Kong

From 2005 to 2013, volatile organic compounds (VOCs) and other trace gases were continuously measured at a suburban site in Hong Kong. The measurement data showed that the concentrations of most air pollutants decreased during these years. However, ozone (O3) and total non-methane hydrocarbon levels increased with the rate of 0.23 ± 0.03 and 0.34 ± 0.02 ppbv/year, respectively, pointing to the increasing severity of photochemical pollution in Hong Kong. The Hong Kong government has ongoing programs to improve air quality in Hong Kong, including a solvent program implemented during 2007–2011, and a diesel commercial vehicle (DCV) program since 2007. From before to after the solvent program, the sum of toluene, ethylbenzene and xylene isomers decreased continuously with an average rate of −99.1 ± 6.9 pptv/year, whereas the sum of ethene and propene increased by 48.2 ± 2.0 pptv/year from before to during the DCV program. Despite this, source apportionment results showed that VOCs emitted from diesel exhaust decreased at a rate of −304.5 ± 17.7 pptv/year, while solvent related VOCs decreased at a rate of −204.7 ± 39.7 pptv/year. The gasoline and liquefied petroleum gas vehicle emissions elevated by 1086 ± 34 pptv/year, and were responsible for the increases of ethene and propene. Overall, the simulated O3 rate of increase was lowered from 0.39 ± 0.03 to 0.16 ± 0.05 ppbv/year by the solvent and DCV programs, because O3 produced by solvent usage and diesel exhaust related VOCs decreased (p < 0.05) by 0.16 ± 0.01 and 0.05 ± 0.01 ppbv/year between 2005 and 2013, respectively. However, enhanced VOC emissions from gasoline and LPG vehicles accounted for most of the O3 increment (0.09 ± 0.01 out of 0.16 ± 0.05 ppbv/year) in these years. To maintain a zero O3 increment in 2020 relative to 2010, the lowest reduction ratio of VOCs/NOx was ∼1.5 under the NOx reduction of 20–30% which was based on the emission reduction plan for Pearl River Delta region in 2020.

Characterization of carbon monoxide, methane and nonmethane hydrocarbons in emerging cities of Saudi Arabia and Pakistan and in Singapore

We investigate the composition of 63 C2-C10 nonmethane hydrocarbons (NMHCs), methane (CH4) and carbon monoxide (CO), in Jeddah, Mecca, and Madina (Saudi Arabia), in Lahore, (Pakistan), and in Singapore. We established a database with which to compare and contrast NMHCs in regions where ambient levels and emissions are poorly characterized, but where conditions are favorable to the formation of tropospheric ozone, and where measurements are essential for improving emission inventories and modeling. This dataset will also serve as a base for further analysis of air pollution in Western Saudi Arabia including, but not limited to, the estimation of urban emissions and long range pollution transport from these regions. The measured species showed enhanced levels in all Saudi Arabian cities compared to the local background but were generally much lower than in Lahore. In Madina, vehicle exhaust was the dominant NMHC source, as indicated by enhanced levels of combustion products and by the good correlation between NMHCs and CO, while in Jeddah and Mecca a combination of sources needs to be considered. Very high NMHC levels were measured in Lahore, and elevated levels of CH4 in Lahore were attributed to natural gas. When we compared our results with 2010 emissions from the MACCity global inventory, we found discrepancies in the relative contribution of NMHCs between the measurements and the inventory. In all cities, alkenes (especially ethene and propene) dominated the hydroxyl radical (OH) reactivity (k OH) because of their great abundance and their relatively fast reaction rates with OH.

Non-methane hydrocarbons (NMHCs) and their contribution to ozone formation potential in a petrochemical industrialized city, Northwest China

Hourly air concentrations of fifty-three non-methane hydrocarbons (NMHCs) were measured at downtown and suburb of Lanzhou, a petrochemical industrialized city, Northwest China in 2013. The measured data were used to investigate the seasonal characteristics of NMHCs air pollution and their contributions to the ozone formation in Lanzhou. Annually averaged NMHCs concentration was 38.29 ppbv in downtown Lanzhou. Among 53 NMHCs, alkanes, alkenes, and aromatics accounted for 57%, 23% and 20% of the total NMHCs air concentration, respectively. The atmospheric levels of toluene and propane with mean values of 4.62 and 4.56 ppbv were higher than other NMHCs, respectively. The ambient levels of NMHCs in downtown Lanzhou were compared with measured NMHCs data collected at a suburban site of Lanzhou, located near a large-scale petrochemical industry. Results show that the levels of alkanes, alkenes, and aromatics in downtown Lanzhou were lower by factors of 3-11 than that in west suburb of the city. O3-isopleth plots show that ozone was formed in VOCs control area in downtown Lanzhou and NOx control area at the west suburban site during the summertime. Propylene-equivalent (Prop-Equiv) concentration and the maximum incremental reactivity (MIR) in downtown Lanzhou indicate that cis-2-butene, propylene, and m/p-xylene were the first three compounds contributing to ozone formation potentials whereas in the petrochemical industrialized west suburb, ethane, propene, and trans-2-Butene played more important role in the summertime ozone formation. Principal component analysis (PCA) and multiple linear regression (MLR) were further applied to identify the dominant emission sources and examine their fractions in total NMHCs. Results suggest that vehicle emission, solvent usage, and industrial activities were major sources of NMHCs in the city, accounting for 58.34%, 22.19%, and 19.47% of the total monitored NMHCs in downtown Lanzhou, respectively. In the west suburb of the city, however, vehicle emission was less important as compared with sources from petrochemical industries, as characterized by relatively higher ethane (C2H4)/ ethyne (acetylene) and propene (C3H6)/ethyne ratios which ruled out tailpipes emission as major contributors to the VOCs sources.

Exploring the seasonal NMHC distribution in an urban area of the Middle East during ECOCEM campaigns: very high loadings dominated by local emissions and dynamics

Environmental context Non-methane hydrocarbons play an important role in the formation of photochemical oxidants such as ozone. We investigate factors controlling the distribution of non-methane hydrocarbons in an urban area of the Middle East. The study highlights the importance of local emissions and atmospheric dynamics, and the limited effect of photochemistry at the measurement site. Abstract Measurements of over 70 C2-C16 non-methane hydrocarbons (NMHCs) were conducted in suburban Beirut (1.3 million inhabitants) in summer 2011 and winter 2012 during the Emission and Chemistry of Organic Carbon in the East Mediterranean (ECOCEM) field campaign. The levels of NMHCs observed exceeded by a factor of two in total volume the levels found in northern mid-latitude megacities (Paris and Los Angeles), especially for the unburned fossil fuel fraction. Regardless of the season, the major compounds, explaining 50% of the concentrations, were toluene, isopentane, butane, m,p-xylenes, propane and ethylene, emitted by mobile traffic and gasoline evaporation sources. Most NMHCs show a distinct seasonal cycle, with a summer maximum and a winter minimum, unlike seasonal cycles usually observed in the northern mid-latitude urban areas. We show that NMHC distribution is mainly driven by strong local emissions and local atmospheric dynamics, with no clear evidence of photochemical removal in summer or influence from long-range transport.

Assessment of carbon monoxide (CO) adjusted non-methane hydrocarbon (NMHC) emissions of a motor fleet – A long tunnel study

Speciated hydrocarbons (NMHCs) and CO were simultaneously measured by evenly distributed samples along the entire length (12.9 km) of the tunnel in different traffic conditions. Four passes (two round-trips) were made at four different fleet speeds (i.e., 45, 65, 75 and 85 km h−1). Individual NMHC and CO mixing ratios were observed to be sensitive to the fleet speed, which is compounded by driving conditions and traffic volumes. We propose using ratios of NMHCs to CO to cancel out the factor of traffic volumes to determine CO-normalized NMHC emissions, such that a less biased comparison can be made between different fleet speeds in this study and even between different studies. Moreover, to obtain robust CO-normalized NMHC emissions which are sufficiently representative of the fleet speeds, only samples collected deep inside the long-tunnels between 8 and 12 km were used.Of the 61 target NMHCs, isomers of butane, pentane, ethylene, acetylene and toluene were the most abundant species regardless of the driving conditions. We observed that different driving conditions not only affected the emission strengths but also altered the compositions of the NMHCs. To simplify the data analysis, the target NMHCs were classified into four chemical groups, i.e., alkanes, alkenes, aromatics and alkynes. For the slower and more congested driving condition (fleet speed = 45 km h−1), the CO-normalized NMHC emissions were the highest, with alkanes contributing to approximately 60% of the total NMHC levels, suggesting poorer fuel utilization at slower driving conditions. In terms of the CO-normalized ozone forming potentials (OFPs), the contribution of the alkanes diminished dramatically to approximately 9–22% despite their high weight percentage, whereas the contribution of the alkenes was enhanced significantly to 50–60% from their weight percent of only approximately 26%.Our total NMHC to CO ratios of 0.06–0.20 for the four fleet speeds generally fall within the range constrained by many other tunnel or chassis dynamometer studies; however, the sensitivity to the driving conditions and the robustness with the long-tunnel data are better demonstrated in this study.

Non–methane hydrocarbon emission profiles from printing and electronic industrial processes and its implications on the ambient atmosphere in the Pearl River Delta, South China

Thirty–seven non–methane hydrocarbons (NMHCs) were quantified for seven industrial work processes, covering the electronic industry and the printing industry, in the Pearl River Delta (PRD). NMHC source profiles (% by wt.) for the respective work processes and their associated industrial solvents were obtained. In order to examine the contribution of the individual work processes to the neighborhood atmospheres, ambient samples on the rooftop of the printing and electronic factories were collected. Total NMHC concentrations of 3 700±740 ppbv and 169±64 ppbv were detected, respectively. Air samples from roadside of a main roundabout, from rooftop of a residential building in the town center and from a background site were also collected to examine the impact of industrial and vehicular emissions on local NMHC levels. NMHC emissions from the printing factory were significantly higher than that from the electronic factory. The two work processes, plastic molding and soldering in the electronics factory, emitted mainly C3–C7 alkanes, while paint solvents used in the printing factory released C7–C8 aromatics. Toluene was the most abundant NMHCs measured for all work processes in the printing factory. It was due to the heavy usage of various solvent–based inks and paint solvents. In general, high toluene levels were found in the ambient and industrial–related atmosphere and this led to low benzene–to–toluene ratios (B/T, ppbv/ppbv) in this study. The B/T ratios for urban, suburban and roadside ambient atmospheres were smaller than 0.2. Much lower ratios (<0.04) were measured for industrial work processes associated with usage of ink and paint solvents. Our study suggests that toluene–rich emission from the printing industry contributes to the gradual increase in the atmospheric toluene background in the PRD.

Variations and sources of ambient formaldehyde for the 2008 Beijing Olympic games

As the host city of the 2008 Olympic games, Beijing implemented a series of air pollution control measures before and during the Olympic games. Ambient formaldehyde (HCHO) concentrations were measured using a fluorometric instrument based on a diffusion scrubber and the Hantzsch reaction; hydrocarbons were simultaneously measured using gas chromatography–mass spectrometry (GC–MS). Meteorological parameters, CO, O 3, and NO 2 concentrations were measured by standard commercial instrumentation. In four separate periods: (a) before the vehicle plate number control (3–19 July); (b) during the Olympic Games (8–24 August); (c) during the Paralympic Games (6–17 September) and (d) after the vehicle control was ceased (21–28 September), the average HCHO mixing ratios were 7.31 ± 2.67 ppbv, 5.54 ± 2.41 ppbv, 8.72 ± 2.48 ppbv, and 6.42 ± 2.79 ppbv, while the total non-methane hydrocarbons (NMHCs) measured were 30.41 ± 18.08 ppbv, 18.12 ± 9.38 ppbv, 30.50 ± 13.37 ppbv, and 33.33 ± 15.85 ppbv, respectively. Both HCHO and NMHC levels were the lowest during the Olympic games, and increased again during the Paralympic games even with the same vehicle control measures operative. Similar diurnal HCHO and O 3 patterns indicated that photo-oxidation of NMHCs may be the major source of HCHO. The diurnal profile of total NMHCs was very similar to that of NO 2 and CO: morning and evening peaks appeared in rush hours, indicating even after strict vehicle control, automobile emission may still be the dominant source of the HCHO precursors. The contributions of HCHO, alkanes, alkenes, and aromatics to OH loss rates were also calculated. HCHO contributed 22 ± 3% to the total VOCs and 24 ± 1% to the total OH loss rate. HCHO was not only important in term of abundance, but also important in chemical reactivity in the air.

The influence of sampling protocol on nonmethane hydrocarbon mixing ratios

The effect of sampling protocol on ambient air hydrocarbon mixing ratios was examined on eight sampling days in Los Angeles during 2007 and 2008. Four protocols, which were based on previously published multi-city urban hydrocarbon studies in the United States, were compared and differences were quantified. Whole air canister samples were collected and analyzed for nonmethane hydrocarbons (NMHCs). Differing sampling protocols resulted in large differences in mixing ratios, up to an order of magnitude, for certain NMHCs on the same sampling day. However, the magnitude of the variability between NMHC levels obtained by the four protocols was not consistent throughout the eight sampling days. It was found that sampling time, followed by sampling location, had the greatest influence on the magnitude of the mixing ratio. Ratios between hydrocarbons, often used in urban studies to gain information on emission sources, also varied depending on the protocol used. Comparison of absolute NMHC mixing ratios collected in urban environments using differing sampling protocols should be made with care.

C 2–C 8 NMHCs over the Eastern Mediterranean: Seasonal variation and impact on regional oxidation chemistry

More than 2500 measurements of C 2–C 8 non-methane hydrocarbons (NMHCs) have been conducted at Finokalia sampling station on the island of Crete over a thirty-month period (September 2003–February 2006), to investigate the factors controlling NMHC levels and estimate their role in the oxidizing capacity of the Eastern Mediterranean atmosphere. Atmospheric concentrations of NMHCs range from below the detection limit (5 pptv) to a few ppbv and present a hydroxyl radical (OH) driven seasonal pattern with lower values during summer. The diel variability was also influenced by the reaction of the NMHC with the OH radical, exhibiting a nighttime maximum and a midday or early afternoon minimum. Long-lived compounds demonstrate higher concentrations under the influence of the northern sector (European continent), indicating that besides chemistry, transport significantly contributes to NMHCs levels in the area. Based on the observed NMHCs diurnal cycles, mean OH radical levels of 3.5 × 10 6 molecules cm −3 have been derived for May–October period.

A multivariate prediction of spatial process with non-stationary covariance for Kuwait non-methane hydrocarbons levels

Predicting unmeasured realizations of multivariate spatial process responses is a fundamental problem in environmetrics. The study of levels of air pollutants is important for understanding and improving air quality in major urban areas. This research aims to handle the prediction in a Bayesian framework for non-methane hydrocarbons NMHC pollutant for the State of Kuwait where records of six monitor stations located in different sites are observed at successive time points. Our objective is to study the distribution level of NMHC with respect to time and metreological parameters and space and use this distribution to predict the concentration of NMHC in other sites of Kuwait using the minimum amount of data (reducing the cost). We will implement a hierarchical Bayesian approach assuming Gaussian random field technique that allows us to pool the data from different sites in predicting the exposure of the non-methane hydrocarbons in different regions of Kuwait.

Characteristics and sources of non‐methane hydrocarbons in background atmospheres of eastern, southwestern, and southern China

Non‐methane hydrocarbons (NMHCs) play very important roles in atmospheric chemistry, yet little is known about their abundance in the atmosphere of China, especially in the background atmospheres. Measurements of C2‐C10 NMHCs were concurrently carried out at two remote background sites and one rural background site in April and May 2004 in this study: Tengchong Mountain (TM) in Yunnan province on the border of southwestern China; Jianfeng Mountain (JM) on the southwest coast of Hainan Island, southern China; and Lin'an (LA) in Zhejiang province in eastern China. Additional samples were collected at an urban site, Tengyue Town (TT, about 10 km from TM), to obtain local urban NMHC profiles. NMHC levels in these background sites were compared with other rural and remote sites in Asia and other global background stations. In the urban site of TT, local biofuel combustion was the major contributor to the high levels of ethene, ethyne, and ethane. In LA, the major sources of NMHCs were the emissions from fossil fuel and biofuel combustion and from industrial solvent use. Compared with another study conducted in 2001, toluene levels had increased by 75% in 2004 in this study, whereas the levels of other anthropogenic hydrocarbons remained at the same levels. Local industrial emissions and transports from the Yangtze River Delta were the major sources of toluene, ethylbenzene, and xylenes in LA. While in TM, the major sources were regional biofuel combustions and biomass burning emissions from Southeast Asia. Long‐range transport of air masses from Southeast Asia was the major source of NMHCs in JM in spring. JM showed the lowest levels of most hydrocarbons among the three background sites. Several hydrocarbon molar ratios, such as benzene/toluene and ethane/propane, were used to characterize the signatures of air masses from different regions.

Nonmethane hydrocarbons at Pico Mountain, Azores: 1. Oxidation chemistry in the North Atlantic region

Measurements of nonmethane hydrocarbons (NMHC) at the Pico Mountain observatory at 2225 m asl on Pico Island, Azores, Portugal, from August 2004 to August 2005 (in part overlapping with the field campaign of the International Consortium on Atmospheric Research on Transport and Transformation study) were used to investigate NMHC sources and seasonal oxidation chemistry in the central North Atlantic region. Levels of anthropogenic NMHC were characteristic of the marine free troposphere. Their concentrations were low compared to continental sites at higher northern latitudes, but higher than data reported from a similarly located Pacific mountain site at Mauna Loa Observatory, Hawaii. These higher NMHC levels are indicative of a greater influence of the adjacent continents on air composition at Pico. Substantially enhanced NMHC concentrations during the summers of 2004 and 2005 were attributed to long‐range transport of biomass burning plumes originating from fires in northern Canada, Alaska, and Siberia. This finding exemplifies the continuing impact of biomass burning plumes on atmospheric composition and chemistry many days downwind of these emission sources. Seasonal cycles with lower NMHC concentrations and lower ratios of more reactive to less reactive NMHC during summer reflect the higher degree of photochemical processing occurring during transport. The NMHC concentrations indicate no significant role of chlorine atom oxidation on NMHC. Ozone above 35 ppbv was measured at Pico Mountain throughout all seasons. Enhanced ozone levels were observed in air that had relatively “fresh” photochemical signatures (e.g., ln [propane]/[ethane] &gt; −2.5). During spring‐summer air that was more processed (“older” air with ln [propane]/[ethane] &lt; −2.5) on average had lower ozone levels (down to &lt;20 ppbv). This relationship indicates that conditions in the lower free troposphere over the mid–North Atlantic during the spring and summer lead to net photochemical ozone destruction while air is photochemically aging during transport to Pico. This behavior contrasts to that in the mid–North Pacific where other recent studies have found that the photochemistry is more nearly ozone neutral.

Characteristic behavior of peroxyacetyl nitrate (PAN) in Seoul megacity, Korea

We measured the concentrations of peroxyacetyl nitrate (PAN) and other photochemically reactive species, including O 3, NO 2, and non-methane hydrocarbons (NMHCs), in the Seoul Metropolitan area (SMA) during May through June in 2004 and 2005. PAN was determined using a fast chromatograph with luminol-based chemiluminescence detection. Mixing ratios of PAN ranged from below the detection limit (0.1 ppbv) to 10.4 ppbv with an average of 0.8 ppbv. O 3 concentrations ranged from 0 to 141 ppbv. The average PAN/O 3 ratio of 0.07 was higher than that observed in cities of Europe and North America (0.02) where control strategies have been enforced to reduce hydrocarbon emissions through extensively reformulated gasoline programs. Strong positive correlations between daily PAN and O 3 maxima during the day demonstrate that similar photochemical factors controlled the production of these two chemicals. However, relationships between PAN and its precursors, NO 2 and NMHCs, suggest that PAN production was more sensitive to NO 2 than NMHCs levels whereas O 3 production was limited by the overall availability of NMHCs. It is likely that the compositions of NMHCs in SMA were favorable for PAN production because of the low fractions of oxygenated compounds in automobile fuels. PAN maxima were observed around noon, which was 2–3 h earlier than the much broader O 3 maxima that occurred in the midafternoon. After reaching the maximum, PAN concentrations rapidly dropped within a few hours, which could be largely due to thermal destruction and to limited production under the typically low NO 2 levels that occurred in the early afternoon. The heterogeneous destruction of particulate matter could be an additional sink for PAN in SMA.