Atmospheric Environment (v.43, #12)
Editorial board (i).
A comparison of North American and Asian exposure–response data for ozone effects on crop yields by L.D. Emberson; P. Büker; M.R. Ashmore; G. Mills; L.S. Jackson; M. Agrawal; M.D. Atikuzzaman; S. Cinderby; M. Engardt; C. Jamir; K. Kobayashi; N.T.K. Oanh; Q.F. Quadir; A. Wahid (1945-1953).
Modelling-based studies to assess the extent and magnitude of ozone (O3) risk to agriculture in Asia suggest that yield losses of 5–20% for important crops may be common in areas experiencing elevated O3 concentrations. These assessments have relied on European and North American dose–response relationships and hence assumed an equivalent Asian crop response to O3 for local cultivars, pollutant conditions and climate. To test this assumption we collated comparable dose–response data derived from fumigation, filtration and EDU experiments conducted in Asia on wheat, rice and leguminous crop species. These data are pooled and compared with equivalent North American dose–response relationships. The Asian data show that at ambient O3 concentrations found at the study sites (which vary between ∼35–75 ppb 4–8 h growing season mean), yield losses for wheat, rice and legumes range between 5–48, 3–47 and 10–65%, respectively. The results indicate that Asian grown wheat and rice cultivars are more sensitive to O3 than the North American dose–response relationships would suggest. For legumes the scatter in the data makes it difficult to reach any equivalent conclusion in relative sensitivities. As such, existing modelling-based risk assessments may have substantially underestimated the scale of the problem in Asia through use of North American derived dose–response relationships.
Keywords: Ozone; Crop yield; Asia; Rice; Wheat; Soybean; Food security;
Chemical and strontium isotope characterization of rainwater in Beijing, China by Zhifang Xu; Guilin Han (1954-1961).
Major ion concentrations and Sr isotope ratios (87Sr/86Sr) were measured in rainwater samples collected at an urban site in Beijing over a period of one year. The pH value and major ion concentrations of samples varied considerably, and about 50% of the rainwater studied here were acidic rain with pH values less than 5.0. Ca2+ and NH4 + were the dominant cations in rainwaters and their volume weighted mean (VWM) values were 608 μeq l−1 (14–1781 μeq l−1) and 186 μeq l−1 (48–672 μeq l−1), respectively. SO4 2− was the predominant anion with VWM value of 316 μeq l−1 (65–987 μeq l−1), next was NO3 − with VWM value of 109 μeq l−1 (30–382 μeq l−1).Using Na as an indicator of marine origin, and Al for the terrestrial inputs, the proportions of sea salt and terrestrial elements were estimated from elemental ratios. More than 99% of Ca2+ and 98% of SO4 2− in rainwater samples are non-sea-salt origin. The 87Sr/86Sr ratios were used to characterize the different sources based on the data sets of this study and those from literatures. Such sources include sea salts (87Sr/86Sr∼0.90917), soluble soil dust minerals originating from either local or the desert and loess areas (∼0.7111), and anthropogenic sources (fertilizers, coal combustion and automobile exhausts). The high concentrations of alkaline ions (mainly Ca2+) in Beijing atmosphere have played an important role to neutralize the acidity of rainwater. However, it is worth noting that there is a remarkable acidification trend of rainwater in Beijing recent years.
Keywords: Major ions; Rainwater; Strontium isotope; Beijing;
Exposure of PM2.5 and EC from diesel and gasoline vehicles in communities near the Ports of Los Angeles and Long Beach, California by Jun Wu; Douglas Houston; Fred Lurmann; Paul Ong; Arthur Winer (1962-1971).
The Ports of Los Angeles and Long Beach are the entry point for almost half of all cargo containers entering the United States. The use of diesel trucks to move Port-related goods has raised significant public health concerns associated with black carbon and other air pollutants. It is difficult to reliably estimate people's exposure to vehicle-related pollutants due to the narrow impact zone of traffic, usually within 200–300 m downwind of major roadways. Previous studies suffer from the lack of traffic count data on surface streets and the lack of neighborhood-level population data. We examined seasonal and annual average exposures of particulate matter less than 2.5 μm (PM2.5) and elemental carbon (EC) at a neighborhood scale for communities heavily impacted by diesel trucks near these ports. We assembled a traffic-activity database that distinguishes gasoline and diesel vehicles on both freeways and surface streets, by consolidating information from several sources, including our own field measurements. The CALINE4 model was used to estimate residential exposure of the study population to PM2.5 and EC. Parcel property data were used to allocate Census block group (BG) population to increase spatial resolution. The annual average PM2.5 and EC exposure due to local traffic was 3.8 and 0.4 μg m−3, respectively. On average, surface streets contributed a little more than freeways (55% vs. 45% for EC and 57% and 43% for PM2.5). Light-duty vehicles contributed significantly more than heavy-duty trucks for PM2.5 (61% vs. 39%), but slightly less than heavy-duty trucks for EC (49% vs. 51%). Community mean population exposure was similar using parcel, census block, and BG population data, but extreme values and standard deviations varied significantly at different spatial resolutions. The intake fraction for the study population was in the range of 1.0–2.2 × 10−5 by vehicle type, roadway type, and season.
Keywords: Particulate matter; Elemental carbon; Traffic; Intake fraction; Dispersion modeling;
Source identification of personal exposure to fine particulate matter using organic tracers by Gregory L. Brinkman; Jana B. Milford; James J. Schauer; Martin M. Shafer; Michael P. Hannigan (1972-1981).
Personal exposure to fine particulate matter (PM2.5) is due to both indoor and outdoor sources. Contributions of sources to personal exposure can be quite different from those observed at ambient sampling locations. The primary goal of this study was to investigate the effectiveness of using trace organic speciation data to help identify sources influencing PM2.5 exposure concentrations. Sixty-four 24-h PM2.5 samples were obtained on seven different subjects in and around Boulder, CO. The exposure samples were analyzed for PM2.5 mass, elemental and organic carbon, organic tracer compounds, water-soluble metals, ammonia, and nitrate. This study is the first to measure a broad distribution of organic tracer compounds in PM2.5 personal samples. PM2.5 mass exposure concentrations averaged 8.4 μg m−3. Organic carbon was the dominant constituent of the PM2.5 mass. Forty-four organic species and 19 water-soluble metals were quantifiable in more than half of the samples. Fifty-four organic species and 16 water-soluble metals had measurement signal-to-noise ratios larger than two after blank subtraction.The dataset was analyzed by Principal Component Analysis (PCA) to determine the factors that account for the greatest variance. Eight significant factors were identified; each factor was matched to its likely source based primarily on the marker species that loaded the factor. The results were consistent with the expectation that multiple marker species for the same source loaded the same factor. Meat cooking was an important source of variability. The factor that represents meat cooking was highly correlated with organic carbon concentrations (r = 0.84). The correlation between ambient PM2.5 and PM2.5 exposure was relatively weak (r = 0.15). Time participants spent performing various activities was generally not well correlated with PCA factor scores, likely because activity duration does not measure emissions intensity. The PCA results demonstrate that organic tracers can aid in identifying factors that influence personal exposures to PM2.5.
Keywords: Personal exposure; Fine particulate matter; Principal component analysis; Source apportionment; Organic tracers;
A Common Representative Intermediates (CRI) mechanism for VOC degradation. Part 3: Development of a secondary organic aerosol module by S.R. Utembe; L.A. Watson; D.E. Shallcross; M.E. Jenkin (1982-1990).
A Photochemical Trajectory Model (PTM), containing the Master Chemical Mechanism version 3.1 (MCM v3.1) coupled with an optimised representation of gas–aerosol absorptive partitioning of 365 oxygenated product species, has been used to simulate mass concentrations of secondary organic aerosol (SOA) for the conditions of the TORCH-2003 campaign in the south-east UK in late July and August 2003. A comprehensive reference dataset of 50 case study arrival events (and 4750 associated hourly air mass history events) has been compiled, which considers the base case conditions and scenarios in which emissions of anthropogenic pollution have been reduced by factors of up to 100. The relative contributions of SOA derived from anthropogenic and biogenic precursors are presented for the range of conditions, and the composition of these simulated components is discussed in terms of average molecular formulae, atomic ratios (H/C, O/C and N/C) and organic aerosol mass to organic carbon mass ratios (OM/OC), which are compared to reported measurements. The MCM v3.1 dataset has been used as a reference benchmark for development and optimisation of a reduced (14 species) SOA module for use with version 2 the Common Representative Intermediates mechanism (CRI v2), described in the first of two preceding companion papers [Jenkin, M.E., Watson, L.A., Utembe, S.R., Shallcross, D.E., 2008a. A Common Representative Intermediates (CRI) mechanism for VOC degradation. Part 1: gas phase mechanism development. Atmospheric Environment, 42, pp. 7185–7195. doi:10.1016/j.atmosenv.2008.07.028.]. The resultant version of the PTM containing CRI v2 and the reduced SOA module has been used to simulate the entire TORCH-2003 campaign at hourly resolution, and the contributions of SOA derived from anthropogenic and biogenic precursors are presented and discussed. The reduced SOA module is also shown to be compatible with the most reduced CRI variant (CRI v2-R5), described in the second of two preceding companion papers [Watson, L.A., Shallcross, D.E., Utembe, S.R., Jenkin, M.E., 2008. A Common Representative Intermediates (CRI) mechanism for VOC degradation. Part 2: gas phase mechanism reduction. Atmospheric Environment, 42, pp. 7196–7204. doi:10.1016/j.atmosenv.2008.07.034.], which is considered appropriate as a traceable reference mechanism in global simulations.
Keywords: Speciated VOC oxidation; Tropospheric chemistry; Degradation mechanisms; Mechanism reduction; SOA modelling; SOA composition;
Coastal and synoptic recirculation affecting air pollutants dispersion: A numerical study by Ilan Levy; Yizhak Mahrer; Uri Dayan (1991-1999).
This study examines the spatial distribution of potential recirculation over the East Mediterranean Sea, and the combined effect of synoptic and meso-scale recirculations on plume dispersion in the region. For this purpose, three case studies are performed by the RAMS–HYPACT modeling system, each for a different synoptic scale flow pattern. Both a quantitative measure of the recirculation potential at each grid cell and particle dispersion are calculated. Although the recirculation index is an Eulerian quantity for the wind field and plume dispersion is a manifestation of the Lagrangian behavior of the wind, good correlation is found between the two.Several locations are identified as having high recirculation potential, including southern Cyprus, the coasts of Israel and Lebanon, the eastern slopes of the Judean Mountains and the Haifa Bay in particular. In the latter location, high recirculation potential could be explained by strong interaction between the land–sea surfaces, curvature of the bay and proximity of the Carmel ridge. It is shown that the synoptic and meso-scale recirculations may, under certain conditions, act together and at the same time in determining particle distribution. Under weak synoptic scale flows, particles are recirculated over the entire East Mediterranean Sea basin, returning onshore after a period of 2–3 days to join freshly emitted particles. At the same time, near-shore land–sea breeze effects cause particles to recirculate on smaller time scales of less then one day, sometimes passing as much as three times over the same airshed. A single elevated emission source is shown to have the potential to impair air quality at a coastal strip as long as 100–200 km upon returning onshore.
Keywords: Coastal recirculation; Synoptic scale recirculation; Pollution dispersion; RAMS; Meso scale;
Modeling of temporal variations of vertical concentration profile of 7Be in the atmosphere by Jan Simon; Jana Meresova; Ivan Sykora; Miroslav Jeskovsky; Karol Holy (2000-2004).
Study of the vertical concentration profile and of the deposition of cosmogenic radionuclides provides information on the vertical transport in the stratosphere and troposphere and the processes of scavenging of aerosol particles by precipitation. Information on the distribution of atmospheric aerosols is important for the understanding of the physical processes relating to the studies in weather climate, air pollution, and aerosol physics. In this work the one-dimensional steady-state model of vertical concentration profile was established and the values of turbulent diffusion coefficient and scavenging coefficient determined by model using experimental data of the 7Be monthly average atmospheric activity concentrations and monthly deposition fluxes in Bratislava are presented. The temporal variations of the vertical distribution profiles of 7Be for each month are also calculated.
Keywords: Modeling; Vertical concentration profile; 7Be; Steady-state diffusion; Washout;
Online update of model state and parameters of a Monte Carlo atmospheric dispersion model by using ensemble Kalman filter by D.Q. Zheng; J.K.C. Leung; B.Y. Lee (2005-2011).
For an atmospheric dispersion model designed for the assessment of nuclear accident consequences, some uncertain model parameters, such as source term and weather conditions, may influence the reliability of model predictions. In this respect, good estimations of both model state and uncertain parameters are required. In this paper, an ensemble Kalman filter (EnKF) based method for simultaneous state and parameter estimation, using off-site radiation monitoring data, is presented. This method is based on a stochastic state space model, which resembles the parameter errors with stochastic quantities. Three imperfect parameters, including the source release rate, wind direction and turbulence intensity were perturbed simultaneously, and multiple parameter estimation were performed. Having been tested against both simulated and real radiation monitoring data, the method was found to be able to realistically reconstruct the real scene of dispersion, as well as the uncertain parameters. The estimated parameters given by EnKF nicely converge to the true values, and the method also tracks the temporal variation of those parameters.
Keywords: Atmospheric dispersion model; Ensemble Kalman Filter; Data assimilation; Parameter estimation;
Impact of mercury emissions from historic gold and silver mining: Global modeling by Sarah Strode; Lyatt Jaeglé; Noelle E. Selin (2012-2017).
We compare a global model of mercury to sediment core records to constrain mercury emissions from the 19th century North American gold and silver mining. We use information on gold and silver production, the ratio of mercury lost to precious metal produced, and the fraction of mercury lost to the atmosphere to calculate an a priory mining inventory for the 1870s, when the historical gold rush was at its highest. The resulting global mining emissions are 1630 Mg yr−1, consistent with previously published studies. Using this a priori estimate, we find that our 1880 simulation over-predicts the mercury deposition enhancements archived in lake sediment records. Reducing the mining emissions to 820 Mg yr−1 improves agreement with observations, and leads to a 30% enhancement in global deposition in 1880 compared to the pre-industrial period. For North America, where 83% of the mining emissions are located, deposition increases by 60%. While our lower emissions of atmospheric mercury leads to a smaller impact of the North American gold rush on global mercury deposition than previously estimated, it also implies that a larger fraction of the mercury used in extracting precious metals could have been directly lost to local soils and watersheds.
Keywords: Mercury; Mining; Gold rush; North America; Deposition; Sediment cores;
PM2.5 characterization for time series studies: Organic molecular marker speciation methods and observations from daily measurements in Denver by Steven J. Dutton; Daniel E. Williams; Jessica K. Garcia; Sverre Vedal; Michael P. Hannigan (2018-2030).
Particulate matter less than 2.5 microns in diameter (PM2.5) has been shown to have a wide range of adverse health effects and consequently is regulated in accordance with the US-EPA's National Ambient Air Quality Standards. PM2.5 originates from multiple primary sources and is also formed through secondary processes in the atmosphere. It is plausible that some sources form PM2.5 that is more toxic than PM2.5 from other sources. Identifying the responsible sources could provide insight into the biological mechanisms causing the observed health effects and provide a more efficient approach to regulation. This is the goal of the Denver Aerosol Sources and Health (DASH) study, a multi-year PM2.5 source apportionment and health study.The first step in apportioning the PM2.5 to different sources is to determine the chemical make-up of the PM2.5. This paper presents the methodology used during the DASH study for organic speciation of PM2.5. Specifically, methods are covered for solvent extraction of non-polar and semi-polar organic molecular markers using gas chromatography–mass spectrometry (GC–MS). Vast reductions in detection limits were obtained through the use of a programmable temperature vaporization (PTV) inlet along with other method improvements. Results are presented for the first 1.5 years of the DASH study revealing seasonal and source-related patterns in the molecular markers and their long-term correlation structure. Preliminary analysis suggests that point sources are not a significant contributor to the organic molecular markers measured at our receptor site. Several motor vehicle emission markers help identify a gasoline/diesel split in the ambient data. Findings show both similarities and differences when compared with other cities where similar measurements and assessments have been made.
Keywords: Particulate matter; PM2.5; Chemical speciation; Organic carbon; Molecular markers;
Nitrous oxide emissions from light duty vehicles by Lisa A. Graham; Sheri L. Belisle; Paul Rieger (2031-2044).
Nitrous oxide (N2O) emissions measurements were made on light duty gasoline and light duty diesel vehicles during chassis dynamometer testing conducted at the Environment Canada and California Air Resources Board vehicle emissions laboratories between 2001 and 2007. Per phase and composite FTP emission rates were measured. A subset of vehicles was also tested using other driving cycles to characterize emissions as a function of different driving conditions. Vehicles were both new (<6500 km) and in-use (6500–160,000 km) and were tested on low sulfur gasoline (<30 ppm) or low sulfur diesel (<300 ppm). Measurements from selected published studies were combined with these new measurements to give a test fleet of 467 vehicles meeting both US EPA and California criteria pollutant emissions standards between Tier 0 and Tier 2 Bin 3 or SULEV. Aggregate distance-based and fuel-based emission factors for N2O are reported for each emission standard and for each of the different test cycles. Results show that the distinction between light duty automobile and light duty truck is not significant for any of the emission standards represented by the test fleet and the distinction between new and aged catalyst is significant for vehicles meeting all emission standards but Tier 2. This is likely due to the relatively low mileage accumulated by the Tier 2 vehicles in this study as compared to the durability requirement of the standard. The FTP composite N2O emission factors for gasoline vehicles meeting emission standards more stringent than Tier 1 are substantially lower than those currently used by both Canada and the US for the 2005 inventories. N2O emission factors from test cycles other than the FTP illustrate the variability of emission factors as a function of driving conditions. N2O emission factors are shown to strongly correlate with NMHC/NMOG emission standards and less strongly with NO X and CO emission standards. A review of several published reports on the effect of gasoline sulfur content on N2O emissions suggests that additional research is needed to adequately quantify the increase in N2O emissions as a function of fuel sulfur.
Keywords: Nitrous oxide emissions; Light duty vehicles; Gasoline; Diesel;
A new approach for estimating emissions of organic solutes and organic solvents under wind speeds by Huan-Ping Chao (2045-2051).
A new approach is developed to predict the volatilization loss of the pure liquid and the volatilization rates of organic solutes with different Henry's law constants (H) under wind speed. The tested compounds include eight volatile organic compounds for pure liquid and the forty-one organic solutes with different H compounds are divided into three groups that span seven H orders. The wind speed is set from 0 to 6.0 ms−1. A characteristic parameter ε was established to estimate volatilization loss of pure organic compounds. The mass transfer coefficient (K OL) ratios of the organic solutes, under both wind speed and still conditions, are applied to describe the volatilization characteristics of the selected solutes. The curve profile for K OL ratios and ε values relative to the selected wind speed can be divided into two stages, the sharp-rise stage and the stable-linearity stage. The critical finding is the ε values for the different organic compounds under a specific wind speed approach a constant. The changes in the curve profile of the K OL ratios are similar to the ε values of the pure organic compounds. It is also found the relatively lower H compounds exhibit a sensitive wind effect on the K OL ratios. The K OL ratios of the relatively higher H compounds indicate a similar linear increase with the increasing wind speed in the two stages. Accordingly, concentrations of the organic compounds at the interface are thought to the primary factor. The obtained results could be a good reference to estimate volatilization loss of the organic solutes or the organic solvents under different wind speed conditions.
Keywords: Volatilization; Henry's law constant; Wind speed; Organic solute;
Behavior of benzene and 1,3-butadiene concentrations in the urban atmosphere of Tokyo, Japan by Wanna Laowagul; Kunio Yoshizumi (2052-2059).
Benzene and 1,3-butadiene concentration profiles in the urban ambient air were generated to investigate their levels at two specified sampling locations, roadside and residential, in Tokyo, Japan. Air monitoring data for benzene and 1,3-butadiene were obtained from the Air Quality Monitoring Information of the Tokyo Metropolitan Government. Air samples were continuously obtained and analyzed every hour for volatile organic compounds (VOCs) using an automated GC–MS system. The diurnal variations in benzene and 1,3-butadiene concentrations showed bi-modal patterns, which were considered to be related to the increasing and decreasing trends of vehicle emissions and vertical mixing depths in a day. The frequencies of occurrence of various benzene and 1,3-butadiene concentrations were examined. The results of each concentration showed log-normal forms with almost straight lines. The frequency distributions of both pollutants were confirmed to have a log-normal, rather than a simple normal, form. The relationship between benzene and 1,3-butadiene concentrations at both the roadside and residential site were examined. Separate observations of day and night trends revealed that photochemical decomposition showed a greater influence on the data in the residential site than that in the roadside site. These results were considered as direct evidences of photochemical decomposition of 1,3-butadiene in the atmosphere.
Keywords: Air toxics; Benzene; 1,3-Butadiene; Diurnal variation; Log-normal distribution; Photochemical decomposition;
Characterizing the spatiotemporal variability of PM2.5 in Cusco, Peru using kriging with external drift by John L. Pearce; Stephen L. Rathbun; Manuel Aguilar-Villalobos; Luke P. Naeher (2060-2069).
Advancing the understanding of spatiotemporal aspects of air pollution in the urban environment is an area where improved methods can be of great benefit to exposure assessment and policy support. This paper explores the potential of a technique known as kriging with external drift (KED) to provide high resolution maps of fine particulate matter for a downtown region of Cusco, Peru. There were three stages in this research. The first was to conduct a pilot level monitoring campaign to investigate ambient, regional, and street-level air pollutant concentrations for particulate matter (PM2.5, PM10) and carbon monoxide (CO) in the Province of Cusco. The second was to compile observations within a geographic information system (GIS) in order to characterize the proximal effect of the local transportation network, elevation, and land use classifications on PM2.5. Third, regression, ordinary kriging and kriging with external drift were used to model PM2.5 for three select time periods during a 24-h day. Statistical evaluations indicate kriging with external drift resulted in the strongest models explaining 64% of variability seen with morning particle concentrations, 25% for afternoon particles, and 53% in evening particles. These models capture spatial and temporal variability for air pollution in Cusco. These variations seem to be influenced, to varying degrees, by elevation, meteorological conditions, spatial location, and transportation characteristics. In conclusion, combining GIS, meteorological data and geostatistics proved to be a complementary suite of tools for incorporating spatiotemporal analysis into the air quality assessment.
Keywords: Air pollution; Exposure assessment; Geographic information systems (GIS); Kriging with external drift; Land use regression;
Characterisation of volatile organic compounds and polycyclic aromatic hydrocarbons in the ambient air of steelworks by Diane Ciaparra; Eric Aries; Marie-Jo Booth; David R. Anderson; Susana Marta Almeida; Stuart Harrad (2070-2079).
Investigations have been undertaken at two integrated steelworks in the UK to characterise airborne organic micro-pollutants and to assess the contribution of iron ore sintering and coke making operations on the air quality. Concentrations of volatile organic compounds (VOCs), namely benzene, toluene and p-xylene, were measured continuously within the boundary of a coking plant using for the first time differential optical absorption spectrometry (DOAS) between 2004 and 2006. Concentrations were obtained along two monitoring paths surrounding the coke plant and the average benzene concentration measured along both paths over the campaign was 28 μg m−3. Highest benzene concentrations were associated with winds downwind of the coke oven batteries. Concentrations of polycyclic aromatic hydrocarbons (PAHs) in ambient air were measured during 27 consecutive days in 2005 at three different locations on an integrated steelworks. PAH profiles were determined for each sampling point and compared to coke oven and sinter plant emission profiles showing an impact from the steelworks. The mean benzo [a] pyrene concentration determined in the immediate vicinity of the coke ovens downwind from the battery was 19 ng m−3, whereas for the two other sites average benzo [a] pyrene concentrations were much lower (around 1 ng m−3). Data were analysed using principal components analysis (PCA) and results showed that coke making and iron ore sintering were responsible for most of the variation in the PAH concentrations in the vicinity of the investigated plant.
Keywords: Steel industry; Benzo [a] pyrene; Benzene; Differential optical absorption spectroscopy; Coke ovens; Source apportionment;
Study on a new correlation between diffusion coefficient and temperature in porous building materials by Qinqin Deng; Xudong Yang; Jianshun Zhang (2080-2083).
The diffusion coefficient (D) and partition coefficient (K ma) are the two important parameters used to predict the volatile organic compound (VOC) emission or sorption characteristics in porous building materials. D and K ma may be strongly affected by temperature (T). In this study, we derived a new correlation between D and T based on the assumption that molecular diffusion is dominant, and evaluated this correlation using a series of existing experimental data. The modeling results using the new correlation agree well with the experimental data. The correlation would be useful for assessment of indoor air quality under different environmental (temperature) conditions.
Keywords: Diffusion coefficient; Temperature; Partition coefficient; Emission; Sorption;
A new look at atmospheric carbon dioxide by David J. Hofmann; James H. Butler; Pieter P. Tans (2084-2086).
Carbon dioxide is increasing in the atmosphere and is of considerable concern in global climate change because of its greenhouse gas warming potential. The rate of increase has accelerated since measurements began at Mauna Loa Observatory in 1958 where carbon dioxide increased from less than 1 part per million per year (ppm yr−1) prior to 1970 to more than 2 ppm yr−1 in recent years. Here we show that the anthropogenic component (atmospheric value reduced by the pre-industrial value of 280 ppm) of atmospheric carbon dioxide has been increasing exponentially with a doubling time of about 30 years since the beginning of the industrial revolution (∼1800). Even during the 1970s, when fossil fuel emissions dropped sharply in response to the “oil crisis” of 1973, the anthropogenic atmospheric carbon dioxide level continued increasing exponentially at Mauna Loa Observatory. Since the growth rate (time derivative) of an exponential has the same characteristic lifetime as the function itself, the carbon dioxide growth rate is also doubling at the same rate. This explains the observation that the linear growth rate of carbon dioxide has more than doubled in the past 40 years. The accelerating growth rate is simply the outcome of exponential growth in carbon dioxide with a nearly constant doubling time of about 30 years (about 2%/yr) and appears to have tracked human population since the pre-industrial era.
Keywords: Climate change; Carbon dioxide;
Emission of N2O on pulse–rice crop rotation in upland by T.S. Ramulu; S.K. Sahoo; R.K. Mohapatra; G. Roy Chaudhury; S.N. Das (2087-2090).
The Seasonally Integrated Flux (SIF) of N2O emission during pulse cultivation in Rabi season (Season-I: December to April) in rain-fed uplands of Orissa, was found to be 17.7 ± 0.07, 18.7 ± 0.16 and 43.3 ± 0.14 gha−1 for horse gram (HG), black gram (BG) and green gram (GG) respectively. During the subsequent Rabi season (Season-II), the SIF of N2O for BG and GG cultivated in the same fields were 20.9 ± 0.24 and 38.0 ± 0.42 gha−1 respectively. Similarly SIF values during rice cultivation with different cultivars have also been calculated to be in the range −20.05 ± 0.33 to 21.98 ± 0.29. Statistical analysis showed good correlation of N2O emission with climatic and soil parameters like temperature, nutrient N and organic matter in soil during pulse cultivation. Multivariate analysis was carried out to factorize the results obtained. Using student ‘t’ test, the N2O emission was observed to be similar for two consecutive Rabi seasons for pulses like BG and GG.
Keywords: GHG; SIF; Multivariate analysis; Student ‘t’ test;
New Directions: Results-oriented multi-pollutant air quality management by Jeffrey R. Brook; Kenneth L. Demerjian; George Hidy; Luisa T. Molina; William T. Pennell; Richard Scheffe (2091-2093).