首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
From December to April, the Arctic air mass is polluted by man-made mid-latitudinal emissions from fossil fuel combustion, smelting and industrial processes. In the rest of the year, pollution levels are much lower. This is the outcome of less efficient pollutant removal processes and better south (S) to north (N) transport during winter. In winter, the Arctic air mass covers much of Eurasia and N. America. Meteorological flow fields and the distribution of anthropogenic SO2 emissions in the northern hemisphere favor northern Eurasia as the main source of visibility reducing haze. Observations of SO42− concentrations in the atmosphere throughout the Arctic yield, depending on location and year, a January–April mean of 1.5–3.9 μg m−3 in the Norwegian Arctic to 1.2–2.2 μg m−3 in the N. American Arctic. An estimate of the mean vertical profile of fine particle aerosol mass during March and April shows that, on average, pollution is concentrated in the lower 5 km of the atmosphere. Not only are anthropogenic particles present in the Arctic atmosphere but also gases such as SO2, perfluorocarbons and pesticides. The acidic nature and seasonal variation of Arctic pollution is reflected in precipitation, the snowpack and glacier snow in the Arctic. A pH of 4.9–5.2 in winter and ~ 5.6 in summer is expected in the absence of calcareous wind blown soil. Glacial records indicate that Arctic air pollution has undergone a marked increase since the mid 1950s paralleling a marked increase in SO2 and NOx emissions in Europe. Effects of Arctic pollution include a reduction in visibility and perturbation of the solar radiation budget in April–June. Potential effects are the acidification and toxification of sensitive ecosystems.  相似文献   

2.
Numerical precipitation scavenging models are used to investigate the relationship between the inflow concentrations of sulfur species to precipitation systems and the resulting sulfur wet deposition. Simulations have been made for summer and winter seasons using concentration ranges of SO2, aerosol SO42−, H2O2 and O3 appropriate for the eastern U.S. summer simulations use one-dimensional timedependent convective cloud and scavenging models; winter simulations use two-dimensional steady-state warm-frontal models. Sulfur scavenging mechanisms include nucleation scavenging of aerosol, aqueous reactions of H2O2, O3 and HCHO with S(IV), and nonreactive S(IV) scavenging. Over the wide range of conditions that have been examined, the relation between sulfur inflow and sulfur wet deposition varies from nearly linear to strongly nonlinear. The degree of nonlinearity is most affected by aerosol SO42− levels and relative levels of SO2 vs H2O2. Higher aerosol SO42− levels (as found in summer) produce a more linear relation. The greatest nonlinearity occurs when SO2 exceeds H2O2. Winter simulations show more nonlinearity than summer simulations.  相似文献   

3.
Scavenging ratios for sulfate on the south-central Greenland Ice Sheet at Dye 3 have been computed for 1982–1984. The ratios are based on measured concentrations in snow and estimated concentrations in air. The snow data have been obtained from snowpit samples which were dated by comparing δ18O values with meteorological records. The airborne concentrations have been estimated from data collected at coastal Greenland sites. Scavenging ratios resulting from this process are found to be in the range ~ 100–200 in winter and ~ 200–400 in summer. The greater summer values are attributed to increased riming, resulting in scavenging of sulfate as condensation nuclei and possible oxidation of SO2 in cloudwater droplets. Using the airborne and snowpit concentrations with assumed dry deposition velocities of 0.02–0.05 cms, it is estimated that dry deposition is responsible for roughly 10–30% of the total sulfate deposition on a year-round basis at Dye 3. During portions of the Arctic winter, however, when the snow is unrimed and when there is less precipitation, dry deposition may be dominant.  相似文献   

4.
Precipitation samples over the Arabian Sea collected during Arabian Sea Monsoon Experiment (ARMEX) in 2002–2003 were examined for major water soluble components and acidity of aerosols during the period of winter and summer monsoon seasons. The pH of rain water was alkaline during summer monsoon and acidic during winter monsoon. Summer monsoon precipitation showed dominance of sea-salt components (∼90%) and significant amounts of non-sea salt (nss) Ca2+ and SO42−. Winter monsoon precipitation samples showed higher concentration of NO3 and NH4+ compared to that of summer monsoon, indicating more influence of anthropogenic sources. The rain water data is interpreted in terms of long-range transport and background pollution. In summer monsoon, air masses passing over the north African and Gulf continents which may be carrying nss components are advected towards the observational location. Also, prevailing strong southwesterly winds at surface level produced sea-salt aerosols which led to high sea-salt contribution in precipitation. While in winter monsoon, it was observed that, air masses coming from Asian region towards observational location carry more pollutants like NO3and nss SO42− that acidify the precipitation.  相似文献   

5.
Time-resolved measurements of SO2, sulfate, particulate carbon and trace metal (Pb, As, K, Mn, Fe and V) concentrations were performed simultaneously at four locations in Ljubljana, Yugoslavia, during February and April of 1985. During the winter three different SO42− formation regimes are identified: A—morning period coinciding with maximum emissions and high humidity resulting in maximum SO42− concentrations, with the sulfate formation during this period attributed to fast heterogeneous, aqueous oxidation of local SO2 involving combustion products; B—late evening period with low humidity and high emissions when most SO42− is primary; C—the remainder of the day when SO42− appears to be of a regional origin and formed by a combination of heterogeneous and homogeneous processes. During the non-heating season, the SO42− appears to be of regional origin.  相似文献   

6.
This study has investigated the influence of synoptic weather patterns and long-range transport episodes on the concentrations of several compounds related to different aerosol sources (EC, OC, SO42?, Ca2+, Na+, K+, 210Pb, levoglucosan and dicarboxylic acids) registered in PM10 or PM2.5 aerosol samples collected at three remote background sites in central Europe. Air mass back-trajectories arriving at these sites have been analysed by statistical methods. Firstly, air mass back-trajectories have been grouped into clusters. Each cluster corresponds to specific meteorological scenarios, which were extracted and discussed. Finally, redistributed concentration fields have been computed to identify the main potential source regions of the different key aerosol components. A marked seasonal pattern is observed in the occurrence of the different clusters, with fast westerly and northerly Atlantic flows during winter and weak circulation flows in summer. Spring and fall were characterised by advection of moderate flows from northeastern and eastern Europe. Significant inter-cluster differences were observed for concentrations of receptor aerosol components, with the highest concentrations of EC, OC, SO42?, K+ and 210Pb associated with local and mesoscale aerosol sources located over central Europe related to enhanced photochemical processes. Emissions produced by fossil fuel and biomass burning processes from the Baltic countries, Byelorussia, western regions of Russia and Kazakhstan in spring and fall also contribute to elevated levels of EC, OC, SO42?, K+ and 210Pb. In the summer period long-range transport episodes of mineral dust from North-African deserts were also frequently detected, which caused elevated concentrations of coarse Ca2+ at sites. The baseline aerosol concentrations in central Europe at the high altitude background sites were registered in winter, with the exception of coarse Na+. While the relatively high concentrations of Na+ can be explained by sea salt advected from the Atlantic, the low levels of other aerosol components are caused by efficient aerosol scavenging associated to advections of Atlantic air masses, as well as lower emissions of these species over the Atlantic compared to those over the European continent and very limited vertical air mass exchange over the continent.  相似文献   

7.
The aerosol samples were collected from a high elevation mountain site, Nainital, in India (1958 m asl) during September 2006 to June 2007 and were analyzed for water-soluble inorganic species, total carbon, nitrogen, and their isotopic composition (δ13C and δ15N, respectively). The chemical and isotopic composition of aerosols revealed significant anthropogenic influence over this remote free-troposphere site. The amount of total carbon and nitrogen and their isotopic composition suggest a considerable contribution of biomass burning to the aerosols during winter. On the other hand, fossil fuel combustion sources are found to be dominant during summer. The carbon aerosol in winter is characterized by greater isotope ratios (av. ?24.0?‰), mostly originated from biomass burning of C4 plants. On the contrary, the aerosols in summer showed smaller δ13C values (?26.0?‰), indicating that they are originated from vascular plants (mostly of C3 plants). The secondary ions (i.e., SO4 2?, NH4 +, and NO3 ?) were abundant due to the atmospheric reactions during long-range transport in both seasons. The water-soluble organic and inorganic compositions revealed that they are aged in winter but comparatively fresh in summer. This study validates that the pollutants generated from far distant sources could reach high altitudes over the Himalayan region under favorable meteorological conditions.  相似文献   

8.
A Micro-Orifice Uniform Deposition Impactor (MOUDI) and a Nano-MOUDI were employed to determine the size-segregated mass distributions of ambient particulate matter (PM) and water-soluble ionic species for particulate constituents. In addition, gas precursors, including HCl, HONO, HNO3, SO2, and NH3 gases, were analyzed by an annular denuder system. PM size mass distribution, mass concentration, and ionic species concentration were measured during the day and at night during episode and non-episode periods in winter and summer. Average total suspended particle (TSP) concentrations during episode days in winter were as high as 153?±?33 μg/m3, and PM mass concentrations in summer were as low as one-third of that in winter. Generally, PM concentration at night was higher than that in the daytime in southern Taiwan during the sampling periods. In winter during the episode periods, the size-segregated mass distribution of PM mass concentration was mostly in the 0.32–3.2-μm range, and the PM concentration increased significantly in the range of 0.32–3.2 μm at night. Ammonium, nitrate, and sulfate were the dominant water-soluble ionic species in PM, contributing 34–48 % of TSP mass. High concentrations of ammonia (12.9–49 μg/m3) and SO2 (2.6–27 μg/m3) were observed in the gas precursors. The conversion ratio was high in the PM size range of 0.18–3.2 μm both during the day and at night in winter, and the conversion ratio of episode days was 20 % higher than that of non-episode days. The conversion factor was high for both nitrogen and sulfur species at nighttime, especially on episode days.  相似文献   

9.
The objective of this study was to determine the concentrations of inorganic ions present in particulate matter smaller than 10 µm (PM10), released into the environment by industrial, domestic and mobile sources in Duzce. To assess spatial variations, samples were collected from two sampling sites that had urban and suburban characteristics. Further, the process was carried out in two seasons to understand the seasonal variations. An ion chromatography device was used for analyzing the inorganic ion content in the collected samples. The highest levels of inorganic ion concentrations were measured at the urban sampling site during the winter campaign. Furthermore, the highest ion concentrations were measured for SO42? ion at both sampling sites and during both seasons, while the lowest concentrations were measured for Br?. Moreover, there were significant relationships between meteorological parameters and ion concentrations. A comparison of the cation and anion equivalence values using seasonal CE/AE (cation equivalence/anion equivalence) ratios showed that the aerosol matter had alkaline characteristics during both seasons. The mean value for the CE/AE ratios was 1.58 in winter and 2.06 in summer at the urban sampling site and 1.36 in winter and 1.52 in summer at the suburban sampling site. The interrelationships among the ions were determined by Pearson correlation analysis. Based on the correlation analyses, the ions emitted from common sources and those exposed to similar atmospheric conditions displayed strong correlations with each other.  相似文献   

10.
This paper reports the results of over 2 years of measurements of several of the species comprising atmospheric SOx (=SO2+SO42−) and NOy (=NO+NO2 + PAN + HNO3+NO3+ organicnitrates + HONO + 2N2O5 …) at Whiteface Mountain, New York. Continuous real-time measurements of SO2 and total gaseous NOy 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 NOy 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 NOy 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  相似文献   

11.
With the aim of understanding the origin of acid rains in South China, we analyzed rainwaters collected from Guangzhou, China, between March 2005 and February 2006. The pH of rainwater collected during the monitoring period varied from 4.22 to 5.87; acid rain represented about 94% of total precipitation during this period. The rainwater was characterized by high concentrations of SO42−, NO3, Ca2+, and NH4+. SO42− and NO3, the main precursors of acid rain, were related to the combustion of coal and fertilizer use/traffic emissions, respectively. Ca2+ and NH4+ act as neutralizers of acid, accounting for the decoupling between high SO42− concentrations and relatively high pH in the Guangzhou precipitation. The acid rain in Guangzhou is most pronounced during spring and summer. A comparison with acid precipitation in other Chinese cities reveals a decreasing neutralization capacity from north to south, probably related to the role and origin of alkaline bases in precipitation.  相似文献   

12.
The photochemical oxidation and dispersion of reduced sulfur compounds (RSCs: H2S, CH3SH, DMS, CS2, and DMDS) emitted from anthropogenic (A) and natural (N) sources were evaluated based on a numerical modeling approach. The anthropogenic emission concentrations of RSCs were measured from several sampling sites at the Donghae landfill (D-LF) (i.e., source type A) in South Korea during a series of field campaigns (May through December 2004). The emissions of natural RSCs in a coastal study area near the D-LF (i.e., source type N) were estimated from sea surface DMS concentrations and transfer velocity during the same study period. These emission data were then used as input to the CALPUFF dispersion model, revised with 34 chemical reactions for RSCs. A significant fraction of sulfur dioxide (SO2) was produced photochemically during the summer (about 34% of total SO2 concentrations) followed by fall (21%), spring (15%), and winter (5%). Photochemical production of SO2 was dominated by H2S (about 55% of total contributions) and DMS (24%). The largest impact of RSCs from source type A on SO2 concentrations occurred around the D-LF during summer. The total SO2 concentrations produced from source type N around the D-LF during the summer (a mean SO2 concentration of 7.4 ppbv) were significantly higher than those (≤0.3 ppbv) during the other seasons. This may be because of the high RSC and SO2 emissions and their photochemistry along with the wind convergence.  相似文献   

13.
We found a significant geographic gradient (longitudinal and latitudinal) in the sulfate (SO42?) concentrations measured at multiple sites over the East Asian Pacific Rim region. Furthermore, the observed gradient was well reproduced by a regional chemical transport model. The observed and modeled SO42? concentrations were higher at the sites closer to the Asian continent. The concentrations of SO42? from China as calculated by the model also showed the fundamental features of the longitudinal/latitudinal gradient. The proportional contribution of Chinese SO42? to the total in Japan throughout the year was above 50–70% in the control case, using data for Chinese sulfur dioxide (SO2) emission from the Regional Emission Inventory in Asia (40–60% in the low Chinese emissions case, using Chinese SO2 emissions data from the State Environmental Protection Administration of China), with a winter maximum of approximately 65–80%, although the actual concentrations of SO42? from China were highest in summer. The multiple-site measurements and the model analysis strongly suggest that the SO42? concentrations in Japan were influenced by the outflow from the Asian continent, and this influence was greatest in the areas closer to the Asian continent. In contrast, we found no longitudinal/latitudinal gradient in SO2 concentrations; instead SO2 concentrations were significantly correlated with local SO2 emissions. Our results show that large amounts of particulate sulfate are transported over long distances from the East Asian Pacific Rim region, and consequently the SO42? concentrations in Japan are controlled by the transboundary outflow from the Asian continent.  相似文献   

14.
A one-box chemical-meteorological model had been formulated to make preliminary estimates of sulphate aerosol formation and direct radiative forcing over India. Anthropogenic SO2 emissions from India, from industrial fuel use and biomass burning, were estimated at 2.0 Tg S yr-1 for 1990 in the range of previous estimates of 1.54 and 2.55 Tg S yr -1 for 1987. Meteorological parameters for 1990 from 18 Indian Meteorological Department stations were used to estimate spatial average sulphate burdens through formation from SO2 reactions in gas and aqueous phase and removal by dry and wet deposition. The hydrogen peroxide reaction was found dominating for undepleted oxidant-rich conditions. Monthly mean sulphate burdens ranged from 2–10 mg m-2 with a seasonal variation of winter–spring highs and summer lows in agreement with previous GCM studies. The sulphate burdens are dominated by sulphate removal rates by wet deposition, which are high in the monsoon period from June–November. Monthly mean direct radiative forcing from sulphate aerosols is high (−3.5 and −2.3 W m-2) in December and January, is moderate (−1.3 to −1.5 W m-2) during February to April and November and low (−0.4 to −0.6 W m-2) during May to October also in general agreement with previous GCM estimates. This model, in reasonable agreement with detailed GCM results, gives us a simple tool to make preliminary estimates of sulphate burdens and direct radiative forcing.  相似文献   

15.
Besides well-known episodic Kosa during spring, high concentrations of Ca2+ in aerosols were observed early in summer as well as in the semi-continuous data of the aerosols at the summit of Mt. Fuji. We further analysed the data to study the chemical characteristics of the high calcium event during early summer. The back trajectory analyses of the event indicated that Ca was transported from arid and semi-arid regions (e.g. the Taklamakan desert) through the westerly-dominated troposphere higher than the height of the summit of Fuji. The amount of SO42? was always equivalent to that of NH4+ unlike the case of the normal Kosa period where SO42? is in excess with respect to NH4+. This shows the ‘after’ mixing of unreacted CaCO3 of Kosa origin with (NH4)2SO4, which was only realized by the downward injection of Kosa particles from higher altitudes to the air masses of different origin. In the case of normal Kosa, the air bearing Kosa particles passed through the polluted area to absorb unneutralized acids (‘on-the-way’ mixing), whereas in the case of the Kosa-like phenomena in summer, the acids from the polluted area have been neutralized by NH4+ and become inactive before mixing with CaCO3 (“after” mixing). We have simplified the chemistry of aerosols using their three major components, Ca2+, SO42? and NH4+, and introduced a new triangle diagram with the three assumed end-members of CaCO3, CaSO4 and (NH4)2SO4 to quantify the contribution of the ‘after’ mixing to the aerosols (AMI; ‘after’ mixing index). Based on the back trajectories of some high AMI cases, CaCO3 in Kosa particles was transported through the middle troposphere (5000–7000 m) and descended to meet another air mass where SO42? had been already neutralized by NH3.  相似文献   

16.
We use GEOS-Chem chemical transport model simulations of sulfate–ammonium aerosol data from the NASA ARCTAS and NOAA ARCPAC aircraft campaigns in the North American Arctic in April 2008, together with longer-term data from surface sites, to better understand aerosol sources in the Arctic in winter–spring and the implications for aerosol acidity. Arctic pollution is dominated by transport from mid-latitudes, and we test the relevant ammonia and sulfur dioxide emission inventories in the model by comparison with wet deposition flux data over the source continents. We find that a complicated mix of natural and anthropogenic sources with different vertical signatures is responsible for sulfate concentrations in the Arctic. East Asian pollution influence is weak in winter but becomes important in spring through transport in the free troposphere. European influence is important at all altitudes but never dominant. West Asia (non-Arctic Russia and Kazakhstan) is the largest contributor to Arctic sulfate in surface air in winter, reflecting a southward extension of the Arctic front over that region. Ammonium in Arctic spring mostly originates from anthropogenic sources in East Asia and Europe, with added contribution from boreal fires, resulting in a more neutralized aerosol in the free troposphere than at the surface. The ARCTAS and ARCPAC data indicate a median aerosol neutralization fraction [NH4+]/(2[SO42?] + [NO3?]) of 0.5 mol mol?1 below 2 km and 0.7 mol mol?1 above. We find that East Asian and European aerosol transported to the Arctic is mostly neutralized, whereas West Asian and North American aerosol is highly acidic. Growth of sulfur emissions in West Asia may be responsible for the observed increase in aerosol acidity at Barrow over the past decade. As global sulfur emissions decline over the next decades, increasing aerosol neutralization in the Arctic is expected, potentially accelerating Arctic warming through indirect radiative forcing and feedbacks.  相似文献   

17.
ABSTRACT

We conducted a multi-pollutant exposure study in Baltimore, MD, in which 15 non-smoking older adult subjects (>64 years old) wore a multi-pollutant sampler for 12 days during the summer of 1998 and the winter of 1999. The sampler measured simultaneous 24-hr integrated personal exposures to PM25, PM10, SO4 2-, O3, NO2, SO2, and exhaust-related VOCs.

Results of this study showed that longitudinal associations between ambient PM2.5 concentrations and corresponding personal exposures tended to be high in the summer (median Spearman's r = 0.74) and low in the winter (median Spearman's r = 0.25). Indoor ventilation was an important determinant of personal PM2.5 exposures and resulting personal-ambient associations. Associations between personal PM25 exposures and corresponding ambient concentrations were strongest for well-ventilated indoor environments and decreased with ventilation. This decrease was attributed to the increasing influence of indoor PM2 5 sources. Evidence for this was provided by SO4 2-measurements, which can be thought of as a tracer for ambient PM25. For SO4 2-, personal-ambient associations were strong even in poorly ventilated indoor environments, suggesting that personal exposures to PM2.5 of ambient origin are strongly associated with corresponding ambient concentrations. The results also indicated that the contribution of indoor PM2.5 sources to personal PM2.5 exposures was lowest when individuals spent the majority of their time in well-ventilated indoor environments.

Results also indicate that the potential for confounding by PM2.5 co-pollutants is limited, despite significant correlations among ambient pollutant concentrations. In contrast to ambient concentrations, PM2.5 exposures were not significantly correlated with personal exposures to PM2.5-10, PM2.5 of non-ambient origin, O3, NO2, and SO2. Since a confounder must be associated with the exposure of interest, these results provide evidence that the effects observed in the PM2.5 epidemiologic studies are unlikely to be due to confounding by the PM2.5 co-pollutants measured in this study.  相似文献   

18.
Abstract

A research site for atmospheric chemistry and air pollution measurements was established at Pinnacle State Park in Addison, NY, in 1995. This paper presents an overview of the site characteristics and measurement program, as well as monthly average concentrations for many of the trace gas and aerosol pollutants over the full measurement period. Monthly averaged ozone concentrations range from values as low as 15 parts per billion (ppb) during cold-season months, to values approaching 50 ppb during some spring and summer months. Sulfur dioxide (SO2), oxides of nitrogen (NOx), and reactive odd nitrogen (NOy) all show distinct seasonal variation, with summertime monthly averages as low as 1–3 ppb, and wintertime monthly averages from 6–12 ppb. The variation in carbon monoxide (CO) is much smaller, with minimums of approximately 150 ppb and maximums only rarely exceeding 250 ppb. Data for three hydrocarbon species propane, benzene, and isoprene—are presented. Propane and benzene show higher monthly averaged concentrations in the winter and lower values in the summer, with values ranging over a factor of 4–5. Isoprene, on the other hand has much higher values during the summer season, sometimes a factor of 10 or more greater than concentrations measured in the winter. Monthly averaged plots for fine particulate matter (PM2.5) beginning in 1999 show a robust summer maximum and winter minimum, and roughly a factor of two difference between the two. An empirical measure of ozone production using the correlation of hour-averaged ozone and NOy data illustrates relatively robust ozone production during some, but not all, summertime months over the time period. Also, an analysis of the frequency distribution of the hours of maximum ozone concentration shows a strong mid-afternoon peak, as expected, but also a prominent secondary maximum centered around midnight. The secondary peak is interpreted as ozone transported from ozone-producing areas to the west, including Buffalo, Cleveland, Pittsburgh, and the Ohio Valley. Finally, SO2 concentrations as a function of wind direction clearly indicate maximum impacts when the winds are out of the south (Pittsburgh and Philadelphia), with a secondary peak when the winds are from the north-northeast, consistent with the locations of major SO2 emission sources in the region.  相似文献   

19.
In this study, we present ∼1 yr (October 1998–September 1999) of 12-hour mean ammonia (NH3), ammonium (NH4+), hydrochloric acid (HCl), chloride (Cl), nitrate (NO3), nitric acid (HNO3), nitrous acid (HONO), sulfate (SO42−), and sulfur dioxide (SO2) concentrations measured at an agricultural site in North Carolina's Coastal Plain region. Mean gas concentrations were 0.46, 1.21, 0.54, 5.55, and 4.15 μg m−3 for HCl, HNO3, HONO, NH3, and SO2, respectively. Mean aerosol concentrations were 1.44, 1.23, 0.08, and 3.37 μg m−3 for NH4+, NO3, Cl, and SO42−, respectively. Ammonia, NH4+, HNO3, and SO42− exhibit higher concentrations during the summer, while higher SO2 concentrations occur during winter. A meteorology-based multivariate regression model using temperature, wind speed, and wind direction explains 76% of the variation in 12-hour mean NH3 concentrations (n=601). Ammonia concentration increases exponentially with temperature, which explains the majority of variation (54%) in 12-hour mean NH3 concentrations. Dependence of NH3 concentration on wind direction suggests a local source influence. Ammonia accounts for >70% of NHx (NHx=NH3+NH4+) during all seasons. Ammonium nitrate and sulfate aerosol formation does not appear to be NH3 limited. Sulfate is primarily associated ammonium sulfate, rather than bisulfate, except during the winter when the ratio of NO3–NH4+ is ∼0.66. The annual average NO3–NH4+ ratio is ∼0.25.  相似文献   

20.
The annular denuder system (ADS) was used to characterize seasonal variations of acidic air pollutants in Seoul, South Korea. Fifty- four 24 h samples were collected over four seasons from October 1996 to September 1997. The annual mean concentrations of HNO3, HNO2, SO2 and NH3 in the gas phase were 1.09, 4.51, 17.3 and 4.34 μg m-3, respectively. The annual mean concentrations of PM2.5(dp≤2.5 μm in aerodynamic diameter, 50% cutoff), SO2-4, NO-3 and NH+4 in the particulate phase were 56.9, 8.70, 5.97 and 4.19 μg m-3, respectively. All chemical species monitored from this study showed statistical seasonal variations. Nitric acid (HNO3) and ammonia (NH3) exhibited substantially higher concentrations during the summer, while nitrous acid (HNO2) and sulfur dioxide(SO2) were higher during the winter. Concentrations of PM2.5, SO2-4, NO-3 and NH+4 in the particulate phase were higher during the winter months. SO2-4, NO-3 and NH+4 accounted for 26–38% of PM2.5. High correlations were found among PM2.5, SO2-4, NO-3 and NH+4. The mean H+ concentration measured only in the fall was 5.19 nmole m-3.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号