Seasonal variations in atmospheric SOx and NOy species in the adirondacks

This paper reports the results of over 2 years of measurements of several of the species comprising atmospheric SO_x (=SO₂+SO₄²⁻) and NO_y (=NO+NO₂ + PAN + HNO₃+NO₃⁻+ organicnitrates + HONO + 2N₂O₅ …) at Whiteface Mountain, New York. Continuous real-time measurements of SO₂ and total gaseous NO_y provided data for about 50% and 65% of the period, respectively, and 122 filter pack samples were obtained for HNO₃, SO₂ and aerosol SO₄²⁻, NO₃⁻, H⁺ and NH₄⁺. Concentrations of SO₂ and NO_y were greatest in winter, whereas concentrations of the reaction products SO₄²⁻ and HNO₃were greatest in summer. The seasonal variation in SO₄²⁻ was considerably more pronounced than that of HNO₃and the high concentrations of SO₄²⁻ aerosol present in summer were also relatively more acidic than SO₄²⁻ aerosol in other seasons. As a result, SO₄²⁻ aerosol was the predominant acidic species present in summer, HNO₃was predominant in other seasons. Aerosol NO₃⁻ concentrations were low in all seasons and appeared unrelated to simultaneous NO_y and HNO₃concentrations. These data are consistent with seasonal variations in photochemical oxidation rates and with existing data on seasonal variations in precipitation composition. The results of this study suggest that emission reductions targeted at the summer season might be a cost-effective way to reduce deposition of S species, but would not be similarly cost-effective in reducing deposition of N species. kwAcid deposition, seasonal variation, sulfate, nitrate, nitric acid, sulfur dioxide, oxides of nitrogen, hydrogen peroxide, ozone, air pollution, Adirondack Mountains     

湖北省大气颗粒物浓度时空变化特征

了解大气颗粒物浓度的时空变化格局对于大气污染防治、预警预报等具有重要理论和实践意义。根据2015年1月至2015年12月湖北省13个主要城市53个监测站点每小时发布的PM10和PM2.5浓度数据,研究了湖北省大气颗粒物浓度时空变化特征。结果表明,PM10和PM2.5浓度在空间上均呈现出鄂西部最低、中部最高、东部居中、南北向的均质性;时间上各城市均呈现颗粒物浓度随着月份变化先降低后升高,1月份最高,8月份最低,且呈现夏季浓度<秋季浓度<春季浓度<冬季浓度的变化规律。分析表明,湖北省大气颗粒物浓度时空变化特征与降水量、气温等气象因子呈现出显著负相关关系,与风速关系不显著;与其来源中建筑施工面积、机动车保有量、货运量和客运量、人均GDP和人均第二产值关系紧密。     

Determination of atmospheric nitrate particulate size distribution and dry deposition velocity for three distinct areas

In this study, both atmospheric particulates and dry deposited particulates were collected at a highway intersection, coastal location and suburban area in Taichung, Taiwan for the characterization of nitrate containing particulates (NCPs) in size distribution and dynamic properties. Collected particulates were placed in contact with nitron (C20H16N4) to form distinctive products of NCPs, which were examined by a SEM. For total atmospheric particulates, the sum of NCP and non-nitrate containing particulate (NNCP), the average shape factor values are 1.69, 1.49, and 1.36 for the highway intersection, coastal area and suburban area, respectively. The calculated shape factors show no significant differences with sizes. Dry deposition fluxes and atmospheric concentrations at various size ranges were estimated. The mass distributed in fine particle range (相似文献   

Seasonal atmospheric deposition variations of polychlorinated biphenyls (PCBs) and comparison of some deposition sampling techniques

Introduction  

Ambient air and bulk deposition samples were collected between June 2008 and June 2009. Eighty-three polychlorinated biphenyl (PCB) congeners were targeted in the samples.     

Seasonal variation of atmospheric ammonia and particulate ammonium concentrations in the urban atmosphere of yokohama over a 5-year period

Measurements of ammonia and particulate ammonium were made in the daytime (1200–1500) at a urban site in Yokohama during the 5-year period, 1982–1986. Diurnal NH₃ concentrations showed a distinct seasonal trend with a maximum in summer. The diurnal monthly average concentrations were above 10 ppb during the late spring and summer months, while the concentrations during the winter months were between 1 and 5 ppb. The seasonal variation was found to be very similar to that of the average air temperature and showed a periodic pattern over 1 year. A good correlation was observed between diurnal NH₃ concentrations and average air temperatures during the 5-year period. The annual mean concentrations were in the range of 6.6–7.6 ppb with only a minor deviation. The diurnal monthly average concentrations of particulate NH₄⁺ were between 1 and 4 μg m⁻³ and no significant seasonal variations were seen. As a short-term study, simultaneous measurements of NH₃, HNO₃ and particulate NO₃⁻ were made. The diurnal mean concentrations of NH₃ and HNO₃ were 7.6 and 0.8 ppb, respectively. The concentration of particulate NO₃⁻ ranged from 0.3 to 6μg⁻³. Both HNO₃ and particulate NO₃⁻ concentrations were relatively low and constant. Thus, NH₃ and HNO₃ levels did not agree with the concentrations predicted from the NH₄NO₃ equilibrium constant.     

Annual evolution and generation mechanisms of particulate nitrate in Madrid

During the course of one year (March 2004–March 2005), PM_2.5 particulate nitrate concentrations were semi-continuously measured every 10 min at a Madrid suburban site using the Rupprecht and Patashnick Series 8400N Ambient Particulate Nitrate Monitor (8400N). Gaseous pollutants (NO, NO₂, O₃, HCHO, HNO₂) were simultaneously measured with a DOAS spectrometer (OPSIS AR-500) and complementary meteorological information was obtained by a permanent tower. The particulate nitrate concentrations ranged from the instrumental detection limit of around 0.2 μg m⁻³, up to a maximum of about 25 μg m⁻³. The minimum monthly average was reached during August (0.32 μg m⁻³) and the maximum during November (3.0 μg m⁻³). Due to the semi-volatile nature of ammonium nitrate, peaks were hardly present during summer air pollution episodes. A typical pattern during days with low dispersive conditions was characterized by a steep rise of particulate nitrate in the morning, reaching maximum values between 9 and 14 UTC, followed by a decrease during the evening. On some occasions a light increase was observed at nighttime. During spring episodes, brief diurnal nitrate peaks were recorded, while during the autumn and winter episodes, later and broader nitrate peaks were registered. Analysis of particulate nitrate and related gaseous species indicated the photo-chemical origin of the morning maxima, delayed with respect to NO and closely associated with secondary NO₂ maximum values. The reverse evolution of nitrate and nitrous acid was observed after sunrise, suggesting a major contribution from HNO₂ photolysis to OH formation at this time of the day, which would rapidly produce nitrate in both gaseous and particulate phase. Some nocturnal nitrate maxima appeared under high humidity conditions, and a discussion about their origin involving different possible mechanisms is presented, i.e. the possibility that these nocturnal maximum values could be related to the heterogeneous formation of nitrous and nitric acid by the hydrolysis of NO₂ on wet aerosols.     

Determination of levoglucosan in atmospheric fine particulate matter

A microanalytical method suitable for the quantitative determination of the sugar anhydride levoglucosan in low-volume samples of atmospheric fine particulate matter (PM) has been developed and validated. The method incorporates two sugar anhydrides as quality control standards. The recovery standard sedoheptulosan (2,7-anhydro-beta-D-altro-heptulopyranose) in 20 microL solvent is added onto samples of the atmospheric fine PM and aged for 1 hr before ultrasonic extraction with ethylacetate/ triethylamine. The extract is reduced in volume, an internal standard is added (1,5-anhydro-D-mannitol), and a portion of the extract is derivatized with 10% by volume N-trimethylsilylimidazole. The derivatized extract is analyzed by gas chromatography/mass spectrometry (GC/MS). The recovery of levoglucosan using this procedure was 69 +/- 6% from five filters amended with 2 microg levoglucosan, and the reproducibility of the assay is 9%. The limit of detection is approximately 0.1 microg/mL, which is equivalent to approximately 3.5 ng/m3 for a 10 L/min sampler or approximately 8.7 ng/m3 for a 4 L/min personal sampler (assuming 24-hr integrated samples). We demonstrated that levoglucosan concentrations in collocated samples (expressed as ng/m3) were identical irrespective of whether samples were collected by PM with aerodynamic diameter < or = 2.5 microm or PM with aerodynamic diameter < or = 10 microm impactors. It was also demonstrated that X-ray fluorescence analysis of samples of atmospheric PM, before levoglucosan determinations, did not alter the levels of levoglucosan.     

Artifact particulate sulfate and nitrate formation on filter media

Laboratory and atmospheric sampling studies were performed to evaluate glass fiber, quartz and Teflon filters for their abilities to form artifact particulate sulfate and nitrate with SO₂and HNO₃, respectively. The glass fiber filters were the types employed by the U.S. EPA as well as many State and local agencies for hi-vol particle sampling in the period 1977–1982.In 24-h laboratory trials, the sulfate artifact with the glass fiber filters ranged from 32 to 59μgcm⁻² (8–15μg m⁻³ at simulated hi-vol sampling rates). With the exception of Whatman QMA, the ‘quartz’ and Teflon filters collected very low levels of SO₂. At nitric acid dosages representative of those in atmospheric sampling, the glass fiber filters retained > 94% of the HNO₃; the ‘quartz’ filters, 33 to > 99%; and Teflon filters, <2 % of the HNO₃,. Because of competing acidic species in ambient air, these represent upper limits to the values to be expected in atmospheric sampling. Over the dosage range evaluated, artifact particulate sulfate and nitrate formation on ‘quartz’ and Teflon filters were highly correlated to each other from one filter to another, with a 4:1 molar ratio of nitrate: sulfate.The sulfate artifact in atmospheric sampling with Pallflex ‘quartz’ filters was consistent with laboratory findings while the nitrate artifact was much lower than predicted.     

Atmospheric particulate nitrate sampling errors due to reactions with particulate and gaseous strong acids

The significance of particulate nitrate loss from inert filters due to reactions with particulate and gaseous strong acids was assessed. Laboratory as well as atmospheric results from California's South Coast Air Basin support such loss by reaction of ammonium nitrate with paniculate H₂SO₄. Nitrate loss by reaction with gaseous HCl, not previously reported, was found to be significant in laboratory trials.     

Physical properties of atmospheric particulate sulfur compounds

Integral properties of the total aerosol—which are usually measured first—tend to be related to certain limited size ranges only and do not represent the aerosol in its entire particle size range. The connection between integral and differential properties will be discussed, as well as the consequences with respect to the presentation of total sulfur mass and the sulfur size distribution. The question of the mixture state will be discussed and data given for the internal and external mixture ratio of ammonium sulfate as the most abundant sulfur compound in aerosols. Finally, a discussion is given of the particle sizes which must be produced to maintain the observed aerosol size distribution by any nucleation processes converting sulfuric gases into particles.     

Seasonal variations and source apportionment of atmospheric PM2.5-bound polycyclic aromatic hydrocarbons in a mixed multi-function area of Hangzhou,China

Environmental Science and Pollution Research - To reveal the seasonal variations and sources of PM2.5-bound polycyclic aromatic hydrocarbons (PAHs) during haze and non-haze episodes, daily PM2.5...     

Mass-size distributions of particulate sulfate, nitrate, and ammonium in a particulate matter nonattainment region in southern Taiwan

Concentrations and distributions of three major water-soluble ion species (sulfate, nitrate, and ammonium) contained in ambient particles were measured at three sampling sites in the Kao-ping ambient air quality basin, Taiwan. Ambient particulate matter (PM) samples were collected in a Micro-orifice Uniform Deposit Impactor from February to July 2003 and were analyzed for water-soluble ion species with an ion chromatograph. The PM1/ PM2.5 and PM1/PM10 concentration ratios at the emission source site were 0.73 and 0.53 and were higher than those (0.68 and 0.48) at the background site because there are more combustion sources (i.e., industrial boilers and traffic) around the emission source site. Mass-size distributions of PM NO3- were found in both the fine and coarse modes. SO4(2-)and NH4+ were found in the fine particle mode (PM2.5), with significant fractions of submicron particles (PM1). The source site had higher PM1/PM10(79, 42, and 90%) and PM1/PM2.5 concentration ratios (90, 58, and 93%) for the three major inorganic secondary aerosol components (SO4(2-), NO3-, and NH4+) than the receptor site (65, 27, and 65% for PM1/PM10, 69, 51, and 70% for PM1/PM2.5. Results obtained in this study indicate that the PM1 (submicron aerosol particles) fraction plays an important role in the ambient atmosphere at both emission source and receptor sites. Further studies regarding the origin and formation of ambient secondary aerosols are planned.     

Simultaneous nitric acid,particulate nitrate and acidity measurements in ambient air

A laboratory and field study was conducted to evaluate measurement methods for atmospheric nitric acid and to elucidate the formation of artifact particulate nitrate on filter media. Nitric acid collection with nylon and NaCl-impregnated filters was compared employing Teflon pre-filters to remove atmospheric particulate matter. The two collection procedures provided > 97% collection of nitric acid at the levels expected under ambient conditions. At higher levels, the efficiency of the nylon filters decreased. Nylon filters supplied by Millipore and Ghia Corporations were shown to be equally effective. Clean Teflon pre-filters permitted passage of > 98% of the HNO₃ to the collection filters. However, atmospheric particulate matter on the pre-filters retained HNO₃. Ammonium nitrate on otherwise clean pre-filters caused positive error in HNO₃ measurement (and a corresponding loss of particulate nitrate) when clean air was passed through the sample. Dissociation to NH₃ and HNO₃ is a likely source of these errors. A lower limit of 22 (ppb)² is obtained for the NH₄NO₃ dissociation constant at 21°C.Atmospheric sampling was done in Pittsburg, California. On average, results with the two HNO₃ collection procedures agreed within 3% for levels in the range 0.3–1.5 ppb. Levels of HNO₃ and NH₃ were below those needed for saturation with respect to NH₄NO₃ formation. A glass fiber filter was shown to serve as a total inorganic nitrate sampler, collecting both particulate nitrate and HNO₃.     

Seasonal patterns of airborne particulate concentrations in New York City

Total suspended particulate (TSP) measurements of the New York City atmosphere have in the past failed to exhibit meaningful seasonal patterns, despite the fact that there are known seasonal differences in the strengths of sources contributing to the TSP. It has been found that when the TSP measurements are normalized for the effects of wind speed and the height of the atmosphere mixing layer, pronounced seasonal differences are seen. Based on analysis of two years of data, it is seen that emissions are increased during the winter months, presumably by combustion of oil for space heating. This source evidently contributes an average of 40 per cent of the total suspended particulates during the winter and ca. 20–30 per cent of the annual average total suspended particulate.     

Sources of atmospheric carbonaceous particulate matter in Pittsburgh,Pennsylvania

The organic carbon (OC)/elemental carbon (EC) tracer method is applied to the Pittsburgh, PA, area to estimate the contribution of secondary organic aerosol (SOA) to the monthly average concentration of organic particulate matter (PM) during 1995. An emissions inventory is constructed for the primary emissions of OC and EC in the area of interest. The ratio of primary emissions of OC to those of EC ranges between 2.4 in the winter months and 1.0 in the summer months. A mass balance model and ambient measurements were used to assess the accuracy of the emissions inventory. It is estimated to be accurate to within 50%. The results from this analysis show a strong monthly dependence of the SOA contribution to the total organic PM concentration, varying from near zero during winter months to as much as 50% of the total OC concentration in the summer.     

Seasonal variations in the chemical composition of particulate matter: a case study in the Po Valley. Part I: macro-components and mass closure

The seasonal variability in the mass concentration and chemical composition of atmospheric particulate matter (PM₁₀ and PM_2.5) was studied during a 2-year field study carried out between 2010 and 2012. The site of the study was the area of Ferrara (Po Valley, Northern Italy), which is characterized by frequent episodes of very stable atmospheric conditions in winter. Chemical analyses carried out during the study allowed the determination of the main components of atmospheric PM (macro-elements, ions, elemental carbon, organic matter) and a satisfactory mass closure was obtained. Accordingly, chemical components could be grouped into the main macro-sources of PM: soil, sea spray, inorganic compounds from secondary reactions, vehicular emission, organics from domestic heating, organics from secondary formation, and other sources. The more significant seasonal variations were observed for secondary inorganic species in the fine fraction of PM; these species were very sensitive to air mass age and thus to the frequency of stable atmospheric conditions. During the winter ammonium nitrate, the single species with the highest concentration, reached concentrations as high as 30 μg/m³. The intensity of natural sources was fairly constant during the year; increases in natural aerosols were linked to medium and long-range transport episodes. The ratio of winter to summer concentrations was roughly 2 for combustion product, close to 3 for secondary inorganic species, and between 2 and 3 for organics. The winter increase of organics was due to poorer atmospheric dispersion and to the addition of the emission from domestic heating. A similar winter to summer ratio (around 3) was observed for the fine fraction of PM.