Observation of volatile and semi-volatile carbonyls in an Algerian urban environment using dinitrophenylhydrazine/silica-HPLC and pentafluorophenylhydrazine/silica-GC-MS

Lower carbonyls and n-alkanals from C5 to C10 were measured from late autumn 2000 to summer 2001 in two urban areas in the Algerian territory: Algiers and Ouargla. They were collected on silica cartridges coated with dinitrophenylhydrazine (DNPH) and pentafluorophenylhydrazine (PFPH), which were analysed by HPLC-UV and high-resolution GC-MS. respectively. The two methods were used in parallel samplings in a suburban Algiers site and provided consistent results for semi-volatile congeners, as differences in the concentration data did not exceed 21% on average for individual carbonyl levels ranging from 0.0 to 0.5-2.6 microg m(-3). Concentrations of formaldehyde up to 27 and 5 microg m(-3) were monitored during 10 h samplings in the daytime in Algiers and Ouargla, respectively; acetaldehyde reached values of 13 and 5 microg m(-3), whilst acetone was the most abundant ketone with peak levels of 14 and 4 microg m(-3), respectively. High night-time levels of lower carbonyls were also measured at both locations. Among the semi-volatile alkanals, the highest levels were observed in suburban Algiers for hexanal and nonanal (2.2 microg m(-3)) and in downtown Algiers for valeraldehyde (2.6 microg m(-3)), whilst in Ouargla only hexanal and nonanal levels within the C5-C10 fraction exceeded 1 microg m(-3). Moreover, benzaldehyde concentrations as high as 5 microg m(-3) were measured in the centre of Algiers. Algiers data are comparable with those found in photochemically polluted urban areas of Europe and the USA. Strong correlations between formaldehyde and acetaldehyde and between formaldehyde and benzaldehyde were observed; by contrast, acetone did not show any correlation with the lower aldehydes, suggesting the existence of carbonyl sources other than vehicular traffic. Diurnal variations of almost all carbonyls suggested that motor vehicles were the most important source in the winter, whereas photochemical production appeared to predominate during the summer.     

Mixing ratios of carbonyls and BTEX in ambient air of Kolkata, India and their associated health risk

Mixing ratios of 15 carbonyls and BTEX (benzene, toluene, ethyl benzene, xylenes) were measured for the first time in ambient air of Kolkata, India at three sites from March to June 2006 and their photochemical reactivity was evaluated. Day and nighttime samples were collected on weekly basis. Formaldehyde was the most abundant carbonyl (mean concentration ranging between 14.07 microg m(-3) to 26.12 microg m(-3) over the three sites) followed by acetaldehyde (7.60-18.67 microg m(-3)) and acetone (4.43-10.34 microg m(-3)). Among the high molecular weight aldehydes, nonanal showed the highest concentration. Among the mono-aromatic VOCs, mean concentration of toluene (27.65-103.31 microg m(-3)) was maximum, closely followed by benzene (24.97-79.18 microg m(-3)). Mean formaldehyde to acetaldehyde (1.4) and acetaldehyde to propanal ratios (5.0) were typical of urban air. Based on their photochemical reactivity towards OH. radical, the concentrations of the VOCs were scaled to formaldehyde equivalent, which showed that the high molecular weight carbonyls and xylenes contribute significantly to the total OH-reactive mass of the VOCs. Due to the toxic effect of the VOCs studied, an assessment for both cancer risk and non-cancer hazard due to exposure to the population were calculated. Integrated life time cancer risk (ILTCR) due to four carcinogens (benzene, ethyl benzene, formaldehyde and acetaldehyde) and non-cancer hazard index for the VOCs at their prevailing level were estimated to be 1.42E-04 and 5.6 respectively.     

Feasibility of detection and quantification of gas-phase carbonyls in indoor environments using PFBHA derivatization and solid-phase microextraction (SPME)

Solid-phase microextraction (SPME) was evaluated for the detection and quantification of the gas-phase carbonyls: citronellal, glyoxal, methylglyoxal, and beta-ionone. Prepared air samples containing the carbonyl compounds were collected at a flow rate of 2.8 L min(-1) in an impinger containing a 25% reagent water/75% methanol collection liquid. The aqueous samples were then derivatized with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA), extracted with a PDMS/DVB coated SPME fiber, and analyzed by GC-MS. Detection limits with a sample air volume of 76 L were calculated to be 0.03 ppbv, 0.34 ppbv, 0.12 ppbv, and 0.28 ppbv for citronellal, glyoxal, methylglyoxal, and beta-ionone, respectively.     

Emission of volatile organic compounds from religious and ritual activities in India

Worshipping activity is a customary practice related with many religions and cultures in various Asian countries, including India. Smoke from incense burning in religious and ritual places produces a large number of health-damaging and carcinogenic air pollutants include volatile organic compounds (VOCs) such as formaldehyde, benzene, 1,3 butadiene, styrene, etc. This study evaluates real-world VOCs emission conditions in contrast to other studies that examined emissions from specific types of incense or biomass material. Sampling was conducted at four different religious places in Raipur City, District Raipur, Chhattisgarh, India: (1) Hindu temples, (2) Muslim graveyards (holy shrines), (3) Buddhist temples, and (4) marriage ceremony. Concentrations of selected VOCs, respirable particulate matter (aerodynamic diameter, <5 μm), carbon dioxide, and carbon monoxide were sampled from the smoke plumes. Benzene has shown highest emission factor (EF) among selected volatile organic compounds in all places. All the selected religious and ritual venues have shown different pattern of VOC EFs compared to laboratory-based controlled chamber studies.     

The determination of ambient formaldehyde using a dual coil system and an assessment of dominant factors that influence its abundance in Korea

An enhanced dual coil 2,4-dinitrophenylhydrazine (DNPH) derivatization method (dual coil/DNPH) allowed the quantitative determination of formaldehyde (HCHO) in ambient air. In this method, traceable HCHO was collected using a coil sampler connected in series and lacking a long sampling tube. It was then analyzed using liquid chromatography followed by UV detection of the DNPH derivatives. The method is based on the reaction of formaldehyde with DNPH to produce 2,4-dinitrophenylhydrazone. The detection limits (3σ) were 0.10–0.40 ppbv with a precision ranging from 0.84 to 4.09% RSD. The results of dual coil/DNPH and conventional DNPH cartridge methods were generally well correlated: HCHO (dual coil/DNPH) = 0.97 (±0.13) vs. HCHO (DNPH Cartridge) + 0.33 (±0.33), r = 0.82. The dual coil/DNPH method was used to measure gaseous HCHO in the atmosphere of Metropolitan Seoul during the summer 2000 and 2001, and in Gwangju during the fall of 2001 and 2002. The daytime mean concentration of HCHO was 4.52 (±5.69) and 3.21 (±1.27) ppbv in Metropolitan Seoul for 10–12 August 2000 and 29–31 May 2001, respectively, and 1.73 (±0.98), 3.04 (±2.25), 2.70 (±1.70), and 2.01 (±2.28) ppbv in Gwangju City during 22–27 September 2001, 17–24 October 2001, 9–13 October 2002, and 28 October to 2 November 2002, respectively. The HCHO in Seoul from 10–12 August 2000 was mainly the result of photochemical processes, while direct emissions from vehicles and long-range transport of air from China contributed during 29–31 May 2001. During 22–27 September 2001, 17–24 October 2001, and 9–13 October 2002 in Gwangju, the HCHO came primarily from photochemical processes, although some air affected by biomass burning admixed in the late afternoon. The increase in the HCHO concentration on 20 October 2001 and from 28 October to 2 November 2002 was attributed mainly to direct emissions from biomass burning in farmland near the measurement site.     

长沙市大气中醛酮类化合物浓度变化特征

参照美国环保署EPA-TO11标准方法,于2014年7—10月监测了长沙市大气中醛酮类化合物的质量浓度。主要监测到的醛酮类化合物为甲醛、乙醛、丙酮、丙醛、甲基丙烯醛,夏季质量浓度最高的是甲醛(13.86 mg/m³),其次是乙醛(7.28 mg/m³)、丙酮(7.14 mg/m³),秋季质量浓度最高的是甲醛(10.31 mg/m³),其次是丙酮(8.37 mg/m³)、乙醛(5.78 mg/m³)。夏季醛酮类化合物的总量高于秋季,甲醛、乙醛、丙酮的质量浓度最大值基本出现在13:00—15:00。C1/C2(甲醛/乙醛)、C2/C3(乙醛/丙醛)的平均值分别为2.02、10.19。分析了醛酮类化合物之间的相关性以及它们可能的来源。丙醛和甲醛、乙醛的相关性较好,三者有共同的人为来源。夏季大气中除丙酮外,其他醛酮类化合物的相关性均较好。夏季甲基丙烯醛和甲醛、乙醛、丙酮有相同的自然来源。综合分析可知,长沙大气中醛酮类化合物质量浓度受自然因素和人为因素的双重影响。     

Measurements of benzene and formaldehyde in a medium sized urban environment. Indoor/outdoor health risk implications on special population groups

In the present study, the results of a measurement campaign aiming to assess cancer risk among two special groups of population: policemen and laboratory technicians exposed to the toxic substances, benzene and formaldehyde are presented. The exposure is compared to general population risk. The results show that policemen working outdoor (traffic regulation, patrol on foot or in vehicles, etc.) are exposed at a significantly higher benzene concentration (3-5 times) than the general population, while the exposure to carbonyls is in general lower. The laboratory technicians appear to be highly exposed to formaldehyde while no significant variation of benzene exposure in comparison to the general population is recorded. The assessment revealed that laboratory technicians and policemen run a 20% and 1% higher cancer risk respectively compared to the general population. Indoor working place air quality is more significant in assessing cancer risk in these two categories of professionals, due to the higher Inhalation Unit Risk (IUR) of formaldehyde compared to benzene. Since the origin of the danger to laboratory technicians is clear (use of chemicals necessary for the experiments), in policemen the presence of carbonyls in indoor air concentrations due to smoking or used materials constitute a danger equal to the exposure to traffic originated air pollutants.     

Atmospheric BTEX concentrations in the vicinity of the crude oil refinery of the Baltic region

Among chemical industries, petroleum refineries have been identified as large emitters of a wide variety of pollutants. Benzene, toluene, ethylbenzene, and xylene (BTEX) form an important group of aromatic volatile organic compounds (VOCs) because of their role in the troposphere chemistry and the risk posed to human health. A very large crude oil refinery of the Baltic States (200,000 bbl/day) is situated in the northern, rural part of Lithuania, 10 km from the town of Ma?eikiai (Lithuania). The objectives of this study were: (1) to determine of atmospheric levels of BTEX in the region rural and urban parts at the vicinity of the crude oil refinery; and (2) to investigate the effect of meteorological parameters (wind speed, wind direction, temperature, pressure, humidity) on the concentrations measured. The averaged concentration of benzene varied from 2.12 ppbv in the rural areas to 2.75 ppbv in the urban areas where the traffic was determined to be a dominant source of BTEX emissions. Our study showed that concentration of benzene, as strictly regulated air pollutant by EU Directive 2008/50/EC, did not exceed the limit of 5 ppbv in the region in the vicinity of the crude oil refinery during the investigated period. No significant change in air quality in the vicinity of the oil refinery was discovered, however, an impact of the industry on the background air quality was detected. The T/B ratio (0.50-0.81) that was much lower than 2.0, identified other sources of pollution than traffic.     

Optimizing a dansylhydrazine (DNSH) based method for measuring airborne acrolein and other unsaturated carbonyls

The Passive Aldehydes and Ketones Sampler (PAKS) method has been developed to measure airborne carbonyls (aldehydes and ketones) by derivatizing the carbonyls with dansylhydrazine (DNSH) on a solid sorbent. The method collection efficiencies are approximately 100% for most saturated carbonyls, but are significantly lower for unsaturated carbonyls. In this study, we examined the mechanisms of DNSH reactions with unsaturated carbonyls, focusing on acrolein. With a better understanding of these mechanisms, we modified the sampling substrate conditions and HPLC analysis conditions of the original PAKS method, resulting in substantially improved collection efficiencies for acrolein and crotonaldehyde. Evaluated under a variety of conditions (temperature, humidity, presence of ozone), the modified PAKS method had a collection efficiency of 99%+/- 5% for acrolein (N= 36) and 96%+/- 20% for crotonaldehyde (N= 6). The acrolein-DNSH derivative was stable within 9.6% of the initial amount, after 14 days of storage at 4 degrees C, on the collection medium; and stable within 2.8% of the initial amount, after 16 days of storage at room temperature, in extract.     

2 ,4-二硝基苯肼固相吸附/高效液相色谱法测定车内空气中醛酮类物质

建立了2，4-二硝基苯肼固相吸附／高效液相色谱同时测定车内空气中4种醛酮类物质的方法，研究了固相吸附采样和前处理方法，优化了试验条件。4种醛酮类物质在一定质量范围内工作曲线线性良好，甲醛、乙醛、丙烯醛、丙酮的检出限分别为0．075μg／m^3、0．207μg／m^3、0．715μg／m^3、0．159μg／m^3（按采样体积12L计），实际样品测定的RSD为7.5％-9．7％。     

Levels, sources, and health risks of carbonyls in residential indoor air in Hangzhou, China

Concentrations of formaldehyde, acetaldehyde, acetone, propionaldehyde, i-pentanal, and butyraldehyde in residential indoor air in Hangzhou were determined. The mean concentration of the total carbonyl compounds in summer was 222.6 μg/m³, higher than that in winter (68.5 μg/m³). The concentration of a specific carbonyl in indoor air was higher than the outdoor air measurement, indicating the release of carbonyls from the indoor sources. Formaldehyde and acetone were the most abundant carbonyls detected in summer and winter, respectively. Multiple regression analysis indicated that carbonyl concentrations in residential indoor air depended on the age of decoration and furniture, as well as their concentrations in outdoor air. In addition, a primary estimation showed that the health risks of carbonyls in summer were higher than those in winter.     

Indoor air quality assessment in child care and medical facilities in Korea

In order to characterize the status of indoor air pollution in some important facilities, a list of key criteria pollutants [particulate matter (PM(10)), carbon dioxide (CO(2)), carbon monoxide (CO), formaldehyde (HCHO), and bioaerosol] was measured from a total of 91 randomly selected sites in 18 different cities, Korea (February 2006 to December 2009). The target facilities include 43 child care facilities, 38 medical facilities, 6 elementary schools, and 4 postnatal care centers. The results showed that some air pollutants (e.g., CO and HCHO) did not exceed the recommended guideline [e.g., the Korean indoor air standard (KIAS) values of 10 ppm and 100 ppb, respectively]. However, concentration of PM(10), CO(2), and bioaerosol occasionally exceeded their respective guidelines (e.g., seven, three, and two cases). Discrete seasonalities were observed from indoor pollutants because of varying ventilation practice (e.g., summer time dominance of PM(10), HCHO, and bioaerosol or winter dominance of CO(2) and CO). However, as the concentrations of the indoor pollutants were scarcely above the recommended guideline level, more diversified approaches are desirable to diagnose the status of indoor pollution and to provide a realistic strategy for the improvement of IAQ.     

Analyzing SO 2 concentrations and wind directions during a short monitoring campaign at a site far from the industrial pole of La Plata, Argentina

This article presents and discusses SO2 air quality concentrations (ppbv) together with wind velocities and directions measurements carried out between September 1st and December 21st 2005 at a site located 8.5 km away from the Industrial Pole of La Plata area. As the city and its surroundings have no official monitoring network, the current work enlarges the air quality information available from the zone and sets some initial considerations to the future siting of monitoring stations. The statistical analysis of the data was performed using techniques of tests for outliers and trends, dissimilarity measures and robust regression. In relation to SO2 concentrations, low values were found during this short campaign considering daily averages (with a maximum of 8.5 ppbv) and hourly averages (with a maximum of 25.9 ppbv); World Health Organization guidelines were never surpassed. Nevertheless, a strong dependence between wind directions carrying air pollutants from the Industrial Pole and hourly concentration peaks were found. Due to low monthly SO2 concentrations and because a decreasing time trend was found, the authors propose, as an example, the implementation of an alternative discontinuous method to the continuous analyzer used in the current campaign. Our results state that sampling every 7 days at 13:00-13:59 hours (local time) would be enough to get representative values of the air quality. As a general remark it is possible to highlight that longer and systematic studies should be encouraged to confirm the seasonal wind pattern and to evaluate the air quality.     

Characteristics and sources of non-methane hydrocarbons and halocarbons in wintertime urban atmosphere of Shanghai, China

The characteristics and sources of major hydrocarbons and halocarbons in the wintertime ambient air of urban center of Shanghai, a mega city of China, were investigated. Propane, toluene, ethyl acetate, and benzene were the most abundant hydrocarbons. The majority of species showed significant variability in mixing ratios with occasional episodic increases. The more common use of liquefied petroleum gas fuel for taxis and light motorcycles was believed to lead to high levels of ambient propane over the urban center of Shanghai. Correlating with toluene, dichloromethane, and 1,2-dichloroethane (1,2-DCE), abundant chloromethane (up to a daily mean of 1.61?±?0.99 ppbv and a maximum of 5.34 ppbv) was mainly associated with industrial emissions, although biomass burnings exist widely in east China. The Chinese New Year (CNY) holiday period with no industrial activity over China provides a platform for the study of industrial emissions over the urban atmosphere of Shanghai. The normal weekly cycles were characterized by higher and more variable mixing ratios during weekdays which dropped during weekends. Enhanced mixing ratios were observed in the fortnight before the CNY holidays due to increased industrial emissions as a result of overtime production to make up for the holiday losses. During the CNY holidays, lower level and less variable mixing ratios were observed. A benzene/toluene (B/T) ratio of 0.6?±?0.4 (mean?±?std.) for the morning rush hour samples was identified to be the characteristic ratio of vehicular emissions. However, a B/T ratio of 0.4?±?0.2 from vehicles and other sources was derived for the ambient air.     

Indoor air in schools and lung function of Austrian school children

The Children's Environment and Health Action Plan for Europe (CEHAPE) of WHO focuses (inter alia) on improving indoor environments where children spend most of their time. At present, only little is known about air pollution in schools and its effect on the lung function of school children. Our project was set up as an Austrian contribution to CEHAPE. In a cross-sectional approach, differences in indoor pollution in nine elementary all-day schools were assessed and 34 of these pollutants were analyzed for a relationship with respiratory health determined by spirometry using a linear regression model. Overall 596 children (aged 6-10 years) were eligible for the study. Spirometry was performed in 433 children. Socio-economic status, area of living (urban/rural), and smoking at home were included in the model as potential confounders with school-related average concentration of air pollutants as the variable of primary interest. A negative association with flow volumes (MEF(75)) was found for formaldehyde in air samples, benzylbutylphthalate and the sum of polybrominated diphenylethers in school dust. FVC and FEV(1) were negatively associated with ethylbenzene and xylenes in air samples and tris(1,3-dichlor-2-propyl)-phosphate on particulates. Although, in general, the quality of school indoor air was not worse than that reported for homes, effects on the respiratory health of children cannot be excluded. A multi-faceted strategy to improve the school environment is needed.     

Seasonal variation, risk assessment and source estimation of PM 10 and PM10-bound PAHs in the ambient air of Chiang Mai and Lamphun, Thailand

Daily PM10 concentrations were measured at four sampling stations located in Chiang Mai and Lamphun provinces, Thailand. The sampling scheme was conducted during June 2005 to June 2006; every 3 days for 24 h in each sampling period. The result revealed that all stations shared the same pattern, in which the PM10 (particulate matters with diameter of less than 10 microm) concentration increased at the beginning of dry season (December) and reached its peak in March before decreasing by the end of April. The maximum PM10 concentration for each sampling station was in the range of 140-182 microg/m(3) which was 1.1-1.5 times higher than the Thai ambient air quality standard of 120 microg/m(3). This distinctly high concentration of PM10 in the dry season (Dec. 05-Mar. 06) was recognized as a unique seasonal pattern for the northern part of Thailand. PM10 concentration had a medium level of negative correlation (r = -0.696 to -0.635) with the visibility data. Comparing the maximum PM10 concentration detected at each sampling station to the permitted PM10 level of the national air quality standard, the warning visibility values for the PM10 pollution-watch system were determined as 10 km for Chiang Mai Province and 5 km for Lamphun Province. From the analysis of PM10 constituents, no component exceeded the national air quality standard. The total concentrations of PM10-bond polycyclic aromatic hydrocarbons (PAHs) are calculated in terms of total toxicity equivalent concentrations (TTECs) using the toxicity equivalent factors (TEFs) method. TTECs in Chiang Mai and Lamphun ambient air was found at a level comparable to those observed in Nagasaki, Bangkok and Rome and at a lower level than those reported at Copenhagen. The annual number of lung cancer cases for Chiang Mai and Lamphun Provinces was estimated at two cases/year which was lower than the number of cases in Bangkok (27 cases/year). The principal component analysis/absolute principal component scores (PCA/APCS) model and multiple regression analysis were applied to the PM10 and its constituents data. The results pointed to the vegetative burning as the largest PM10 contributor in Chiang Mai and Lamphun ambient air. Vegetative burning, natural gas burning & coke ovens, and secondary particle accounted for 46-82%, 12-49%, and 3-19% of the PM10 concentrations, respectively. However, natural gas burning & coke ovens as well as vehicle exhaust also deserved careful attention due to their large contributions to PAHs concentration. In the wet season and transition periods, 42-60% of the total PAHs concentrations originated from vehicle exhaust while 16-37% and 14-38% of them were apportioned to natural gas burning & coke ovens and vegetative burning, respectively. In the dry period, natural gas burning & coke ovens, vehicle exhaust, and vegetative burning accounted for 47-59%, 20-25%, and 19-28% of total PAHs concentrations. The close agreement between the measured and predicted concentrations data (R(2) > 0.8) assured enough capability of PCA/APCS receptor model to be used for the PM10 and PAHs source apportionment.     

Seasonal Variation of Toxic Benzene Emissions in Petroleum Refinery

Petroleum refineries are largest chemical industries that are responsible for the emission of several pollutants into the atmosphere. Benzene is among the most important air pollutants that are emitted by petroleum refineries, since they are involved in almost every refinery process. Volatile organic compounds (VOCs) are a major group of air pollutants, which play a critical role in atmospheric chemistry. These contribute to toxic oxidants, which are harmful to ecosystem, human health and atmosphere. The variability of pollutants is an important factor in determining human exposure to these chemicals. The ambient air concentrations of benzene were measured in several sites around the Digboi petroleum refinery, near the city of Gowahati in northeast India, during winter and summer 2004. The seasonal and spatial variations of the ambient air concentrations of this benzene were investigated and analyzed. An estimation of the contribution of the refinery to the measured atmospheric levels of benzene was also performed. The ambient air mixing ratios of benzene in a large area outside the refinery was generally low, in ppbv range, much lower than the ambient air quality standards. This article presents the temporal and spatial variation of air pollution in and around petroleum refinery and showed that no health risk due to benzene is present in the areas adjacent to the refinery.     

Seasonal variations of monocarbonyl and dicarbonyl in urban and sub-urban sites of Xi’an,China

Seventeen airborne carbonyls including monocarbonyls and dicarbonyls were determined in urban and sub-urban sites of Xi’an, China in three seasons in 2010. In winter, acetone was the most abundant carbonyl in the urban site due to usage of organic solvents in constructions and laboratories and its slower atmospheric removal mechanisms by photolysis and reaction with hydroxyl radical than those of formaldehyde and acetaldehyde. In the sub-urban site, acetaldehyde was the most abundant carbonyl, followed by formaldehyde and acetone. During summer, however, formaldehyde was the most dominant carbonyl in both sites. The photooxidations of a wide range of volatile organic compounds (VOCs) yielded much more formaldehyde than other carbonyls under high solar radiation and temperature. In the urban site, the average concentrations of dicarbonyls (i.e., glyoxal and methyglyoxal) in spring and summer were higher than that in winter. Transformation of aromatic VOCs emitted from fuel evaporation leads to the formation of 1,2-dicarbonyls. A reverse trend was observed in sub-urban sites, as explained by the relatively low abundances and accumulations of VOC precursors in the rural atmosphere during warm seasons. Moreover, cumulative cancer risk based on measured outdoor carbonyls (formaldehyde and acetaldehyde) in Xi’an Jiaotong University and Heihe was estimated (8.82?×?10^?5 and 4.96?×?10^?5, respectively). This study provides a clear map on the abundances of carbonyls and their source interpretation in the largest and the most economic city in Northwestern China.     

Diode laser system for measurement of gaseous ammonia in ambient air

The use of a second harmonic diode laser system for monitoring gaseous ammonia in tropospheric air is discussed. Using a 96 m White cell operated at 13 torr pressure in flow mode, a minimum detectable concentration lower than 1 ppbv was obtained.The NH₃ mixing ratio was determined by simultaneous spectroscopic analysis of an atmospheric CO₂ line used as a built-in calibration standard.     

Relationship between CH₄ and N₂O flux from soil and their ambient mixing ratio in a riparian rice-based agroecosystem of tropical region

Temporal variations of the ambient mixing ratio of greenhouse gas (CH(4) and N(2)O) in a riparian rice-based agro-ecosystem of tropical region were studied during 2005-2006 in coastal Odisha. The endeavour was made with the hypothesis that the ambient mixing ratio of CH(4) and N(2)O depends on the changes in the flux of CH(4) and N(2)O from the rice fields in the riparian rice ecosystems. A higher ambient mixing ratio of CH(4) was recorded during the tillering to grain filling stages of the rice crop, during both dry and wet seasons. The higher ambient mixing ratio of CH(4) during the wet season may attribute to the higher CH(4) emission from the rice field. The average mixing ratio of CH(4) was recorded as 1.84 ± 0.05 ppmv and 1.85 ± 0.06 ppmv during 2005 and 2006, respectively. The ambient CH(4) mixing ratio was recorded negatively correlated with the average ambient temperature. The N(2)O mixing ratio ranged from 261.57 to 399.44 ppbv with an average of 330.57 ppbv during 2005. However, the average mixing ratio of N(2)O was recorded as 318.83 ± 20.00 ppbv during 2006. The N(2)O mixing ratio was recorded to be negatively correlated with rainfall and average ambient temperature. Significant negative correlation (r = -0.209) of N(2)O with sunshine hours may attribute to the photochemical break down of N(2)O. The temporal variation of N(2)O flux from the rice field does not affect the ambient mixing ratio of N(2)O in the same way as in the case of the ambient mixing ratio of CH(4). However, the higher mixing ratio of N(2)O during the fallow period of the post monsoon period may attribute to the N(2)O flux from soil. Results indicate that intensively cultivated coastal ecosystems can be a major source of ambient greenhouse gas.