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1.
Mingqiang Huang Weijun Zhang Liqing Hao Zhenya Wang Wenwu Zhao Xuejun Gu Xiaoyong Guo Xianyun Liu Bo Long Li Fang 《Journal of Atmospheric Chemistry》2007,58(3):237-252
Five aromatic hydrocarbons – benzene, toluene, ethylbenzene, p-xylene and 1,2,4-trimethylbenzene – were selected to investigate the laser desorption/ionization mass spectra of secondary
organic aerosols (SOA) resulting from OH-initiated photooxidation of aromatic compounds. The experiments were conducted by
irradiating aromatic hydrocarbon/CH3ONO/NO
X
mixtures in a home-made smog chamber. The aerosol time-of-flight mass spectrometer (ATOFMS) was used to measure the aerodynamic
size and chemical composition of individual secondary organic aerosol particles in real-time. Experimental results showed
that aerosol created by aromatics photooxidation is predominantly in the form of fine particles, which have diameters less
than 2.5 μm (i.e. PM2.5), and different aromatic hydrocarbons SOA mass spectra have eight same positive laser desorption/ionization
mass spectra peaks: m/z = 18, 29, 43, 44, 46, 57, 67, 77. These mass spectra peaks may come from the fragment ions of the
SOA products: oxo-carboxylic acids, aldehydes and ketones, nitrogenated organic compounds, furanoid and aromatic compounds.
The possible reaction mechanisms leading to these products were also discussed. 相似文献
2.
Trudi A. Semeniuk Matthew E. Wise Scot T. Martin Lynn M. Russell Peter R. Buseck 《Journal of Atmospheric Chemistry》2007,56(3):259-273
We used both a conventional transmission electron microscope and an environmental transmission electron microscope (ETEM)
to determine morphology, composition, and water uptake of 80 individual aerosol particles collected from the young smoke of
flaming and smoldering fires during SAFARI-2000, a comprehensive air quality campaign in southern Africa. Six representative
carbonaceous particle types are described, including soot, tar balls, and heterogeneously internally mixed particles containing
C with S-, K-, Mg- or Na-rich inorganic phases. The hygroscopic behavior of these particles over the range 0–100% relative
humidity (RH) was studied in detail. Soot and tar balls did not take up water, whereas the mixed organic–inorganic particles
took up water between 55 and 100% RH, the exact value depending on the composition of their water-soluble phases. The inorganic
phase appeared to determine the hygroscopic properties of all mixed organic–inorganic particles. Thus, incorporation of inorganic
plant material or reactions with inorganic atmospheric components can dramatically alter the hygroscopic properties of carbonaceous
particles in smoke plumes. The fraction of these mixed organic–inorganic particles plausibly increases with time, which will
modulate the effects of smoke on radiative budgets. 相似文献
3.
Three-hour and daily mean measurements of the module of an average speed and wind gusts were analyzed over 2001–2006 in the
Chernobyl NPP region using wavelet analysis and the method of the Herst normalized range. Diurnal and seasonal fluctuations
are revealed, the periodicity of 8, 16, and 60 days is not well-pronounced. The derived Herst high-value coefficients (∼0.7–0.8)
against the background of well-pronounced seasonal and other fluctuations of an average wind speed are indicative of the fact
that its temporal variability is far from being random. The analysis is performed to predict the concentration of radioactive
aerosols released from the Ukrytie object (the damaged unit 4 of the ChNPP), whose changes correlate with the wind speed. 相似文献
4.
Leesun Kim Ian E. Galbally Nichola Porter Ian A Weeks Sarah J Lawson 《Journal of Atmospheric Chemistry》2011,68(3):265-279
Emissions of biogenic volatile organic compounds (BVOCs) from mechanical wounding of leaves and branches of plants can contribute
to the atmospheric burden of volatile organic compounds (VOCs) in both (a) urban airsheds (from urban garden maintenance)
and (b) the global atmosphere (from large scale forest harvesting). These emissions of BVOCs are poorly understood and quantified,
and their role in urban and global emissions inventories neglected. This paper presents measurements of the magnitude, duration
and composition of emissions of BVOCs, carbon dioxide (CO2) and methane (CH4) from freshly cut leaf mulch and wood chips derived from a common eucalypt tree, Eucalyptus sideroxylon (red ironbark), found in southeastern Australian forests and gardens. The emissions of BVOCs from freshly cut and shredded
leaves and wood of E. sideroxylon were found to be 2.3 ± 0.6 and 0.05 ± 0.04 mg g-1 DM (Dry Mass) from leaf mulch and wood chips respectively and to last typically for 1 day following cutting. Three sampling
techniques were used for VOC speciation and the 12 most abundant BVOCs released from the mulch materials were identified.
The specific BVOCs emitted in order of decreasing abundance from leaf mulch are: (a) stored plant oils, 1,8-cineole, α–pinene
and o-cymene which make up the major part of the emissions, (b) a minor contribution from chemicals associated with environmental
stress and wound defence, (Z)–3–hexenyl acetate, (E)-2-hexenal and (Z)-3-hexen-1-ol, and (c) a second minor contribution from
metabolic products, acetaldehyde and acetone. The observed integrated emissions of BVOCs from leaves following mulching are
equivalent to more than half and perhaps all of the likely stored plant oils in the leaves. For the two comparable studies
available, one of a plant with stored oils (this study) and one of a plant without stored plant oils, the emissions of leaf
wound defence BVOCs are in the same range for both plants. In the plant with stored plant oils, the plant oil emissions are
about a factor of 11 larger in emission rate than the plant wound defence BVOCs. A compilation of available leaf wounding
BVOC emission studies indicates that for plants with stored plant oils, plant oil emissions dominate, whereas with other plants,
leaf wound defence BVOCs dominate the emissions. 相似文献
5.
Feasibility is investigated of multi-wavelength lidar exploration of size distribution patterns (SDP) and complex refractive indices (CRI) of aerosols in different layers of a stratified atmosphere, and an improved observational scheme is worked out for the optical parameters (extinction coefficients, angular scattering coef-ficients and their ratios) of the substance in layers homogeneous horizontally in optical depth obtained by a bi-static lidar system. Variations are examined of these parameters versus CRI (whose real part is 1.33- l.63 and imaginary 0.00-0.1) and working wavelengths (0.3472, 0.53, 0.6943 and 1.06 μm) in such SDP as Junge-3, 4 and 5. The Deirmendjian Haze M and L. A method is thereupon developed for retrieval of aerosols’ SDP and CRI from these parameters and tested by suitable numerical experiments. 相似文献
6.
利用已有的硫酸盐和烟尘气溶胶折射指数资料,精确计算了这两种气溶胶从太阳短波到红外谱段的辐射特性。然后,在LLNL化学输送模式(CTM)模拟的硫酸盐和烟尘气溶胶资料及改进的气溶胶参数化基础上,在国内首次用GCM估算了这两种气溶胶引起的全球辐射强迫。结果表明:(1)西欧是全球最大的硫酸盐辐射强迫中心,最大值出现在夏季,达-5.0W/m2;(2)烟尘强迫的最大中心出现在夏季的南美和非洲中南部,为4.0W/m2;(3)南半球大陆人为气溶胶的强迫不容忽视;(4)某些地区人为气溶胶的强迫在量值上可与CO2等温室气体引起的强迫相比拟。 相似文献
7.
Aditi Kulshrestha Deewan Singh Bisht Jamson Masih David Massey Suresh Tiwari Ajay Taneja 《Journal of Atmospheric Chemistry》2009,62(2):121-138
This paper deals with the atmospheric concentrations of PM5 and PM2.5 particulate matter and its water soluble constituents along with the size distribution of ions and spatial variation at three
different residential environments in a semiarid region in India. Samples were collected from the indoors and outdoors of
urban, rural and roadside sites of Agra during October 2007–March 2008. The mean concentrations of PM2.5 indoors and outdoors were 178 μgm−3 and 195 μgm−3 while the mean concentrations of PM5 indoors and outdoors were 231.8 μgm−3 and 265.2 μgm−3 respectively. Out of the total aerosol mass, water soluble constituents contributed an average of 80% (33% anions, 50% cations)
in PM5 and 70% (29% anions, 43% cations) in PM2.5. The indoor–outdoor ratio of water soluble components suggested additional aerosol indoor sources at rural and roadside sites.
Indoor–outdoor correlations were also determined which show poor relationships among concentrations of aerosol ions at all
three sites. Univariate Pearson correlation coefficients among water soluble aerosols were determined to evaluate the relationship
between aerosol ions in indoor and outdoor air. 相似文献
8.
The dynamics of terrestrial ecosystems depends on interactions between carbon, nutrient and hydrological cycles. Terrestrial ecosystems retain carbon in live biomass (aboveground and belowground), decomposing organic matter, and soil. Carbon is exchanged naturally between these systems and the atmosphere through photosynthesis, respiration, decomposition, and combustion. Human activities change carbon stock in these pools and exchanges between them and the atmosphere through land-use, land-use change, and forestry.In the present study we estimated the wood (stem) biomass, growing stock (GS) and carbon stock of Indian forests for 1984 and 1994. The forest area, wood biomass, GS, and carbon stock were 63.86 Mha, 4327.99 Mm3, 2398.19 Mt and 1085.06 Mt respectively in 1984 and with the reduction in forest area, 63.34 Mha, in 1994, wood biomass (2395.12 Mt) and carbon stock (1083.69 Mt) also reduced subsequently. The Conifers, of temperate region, stocked maximum carbon in their woods, 28.88 to 65.21 t C ha−1, followed by Mangrove forests, 28.24 t C ha−1, Dipterocarp forests, 28.00 t C ha−1, and Shorea robusta forests, 24.07 t C ha−1. Boswellia serrata, with 0.22 Mha forest area, stocked only 3.91 t C ha−1. To have an idea of rate of carbon loss the negative changes (loss of forest area) in forest area occurred during 1984–1994 (10yrs) and 1991–1994 (4yrs) were also estimated. In India, land-use changes and fuelwood requirements are the main cause of negative change. Total 24.75 Mt C was lost during 1984–1994 and 21.35 Mt C during 1991–94 at a rate of 2.48 Mt C yr−1 and 5.35 Mt C yr−1 respectively. While in other parts of India negative change is due to multiple reasons like fuelwood, extraction of non-wood forest products (NWFPs), illicit felling etc., but in the northeastern region of the country shifting cultivation is the only reason for deforestation. Decrease in forest area due to shifting cultivation accounts for 23.0% of the total deforestation in India, with an annual loss of 0.93 Mt C yr−1. 相似文献
9.
Water-Soluble dicarboxylic acids, ketoacids and dicarbonyls in the atmospheric aerosols over the southern ocean and western pacific ocean 总被引:2,自引:0,他引:2
Water-soluble dicarboxylic acids (DCAs), ketoacids, and α-dicarbonyls in the marine aerosol samples collected over the Southern
Ocean and western Pacific Ocean were determined. Oxalic acid was the most abundant species, followed by malonic acid and then
succinic acid. It is suggested that aerosol concentrations of the organics over the Southern Ocean in this work represent
their global background levels. Over the Southern Ocean, total concentrations of DCAs ranged from 2.9 to 7.2 ng m−3 (average: 4.5 ng m−3), ketoacids from 0.14 to 0.40 ng m−3 (av.: 0.28 ng m−3), and dicarbonyls from 0.06 to 0.29 ng m−3 (av.: 0.11 ng m−3). Over the western Pacific, total concentrations of DCAs ranged from 1.7 to 170 ng m−3 (av.: 60 ng m−3), ketoacids from 0.08 to 5.3 ng m−3 (av.: 1.8 ng m−3), and dicarbonyls from 0.03 to 4.6 ng m−3 (av.: 0.95 ng m−3). DCAs over the western Pacific have constituted a large fraction of organic aerosols with a mean DCAs-C/TC (total carbon)
of 7.0% (range: 0.59–14%). Such a high value was in contrast to the low DCAs-C/TC (av.: 1.8%; range: 0.89–4.0%) for the Southern
Ocean aerosols. Based on the relative abundances and latitudinal distributions of these organics, we propose that long-range
atmospheric transport is more important over the western Pacific Ocean, in contrast, in situ photochemical production is more significant over the Southern Ocean although absolute concentrations of the organics are
much lower. 相似文献
10.
Y. N. Samsonov 《Journal of Atmospheric Chemistry》2007,56(2):127-147
A chemical substance being in a high-disperse state (fine aerosol particles and very thin films) in the environment reveals
specific chemical and physicochemical features which differ from the processes in a relatively coarse disperse object and,
even more, in ordinary liquid and solid “test-tube” assays. The kinetics and the mechanism of the direct and sensitized photochemical
destruction of pesticide compound fipronil C12H4Cl2F6N4OS have been experimented as applied to the aerosol particles ≈0.12–1.3 μm in diameter and thin films ≈0.02–0.6 μm thick on
the glass plates. A non-photochemical (“dark”) reaction of fipronil molecules with the OH radicals which spontaneously proceeds
in the ambient air was also observed. Quantitative estimations based on experimental results show that the fipronil pollutant,
observed in the atmosphere in the form of levitated aerosols, can convert chemically in the above reaction with the OH radicals
for a very short time (from several minutes for a particle 2 μm in diameter to 12–24 h for a particle of 20–30 μm). The fipronil
residues presented on foliage either in the form of 1–20 μm films or as a group of deposited 2–30 μm aerosols react under
sunlight by two photochemical pathways (photooxidation and photodecay). The lifetime of these residues in the ambient conditions
is expected to be 11–25 days. Besides, adding a small amount of the Shirvanol 2 sensitizer to the fipronil formulation, one
can increase the overall decomposition rate to 8–12 days. 相似文献
11.
I. P. Parshutkina E. V. Sosnikova N. P. Grishina E. A. Stulov N. O. Plaude N. A. Monakhova 《Russian Meteorology and Hydrology》2011,36(6):355-361
Daily measurements of atmospheric aerosol characteristics were carried out in Dolgoprudny (Moscow region) in June–August 2010.
The particle concentrations at 11 size gradations within the range of 0.01–10 μm and the concentrations of cloud condensation
nuclei active at water vapor supersaturation of 0.2–1% were determined. It is shown that the long anticyclonic conditions
and the burning of forests and peat bogs resulted in the increase in total aerosol concentration in surface air by more than
1.5 times and in concentrations of particles with the diameter of 0.1–1 μm and > 1 μm by 5 and 10 times, respectively. The
fire smoke mainly consisted of the particles with the size of 0.1–3 μm. The particles with the size of more than 5 μm were
not observed. The recurrent visibility decrease up to hundreds of meters was caused by the increase in the concentration of
particles with the diameter of more than 0.32μm in the air. During the smoke blanketing, the concentration of active condensation
nuclei in aerosol increased almost by 20 times that created an opportunity for watering of aerosol particles and formation
of the acid smog. 相似文献
12.
The chemistry of heavy haze over Urumqi,Central Asia 总被引:1,自引:0,他引:1
Juan Li Guoshun Zhuang Kan Huang Yanfen Lin Qiongzhen Wang Yuhong Guo Jinghua Guo Shulong Yu Caixia Cui Joshua S. Fu 《Journal of Atmospheric Chemistry》2008,61(1):57-72
A sampling campaign of aerosols over Urumqi from 2001–2007 and soil samples in the surrounding areas were carried out to investigate
the severe air pollution in Urumqi, a typical inland city, located in the center of Asia. Urumqi is one of the heavy polluted
cities in the world, as the days of haze spanned over one third of the year and accounted for 60–80% of the heating period
for the past 6 years. High concentration of fine aerosols, frequent occurrence, and rapid formation of heavy haze were the
three main characteristics. With comparison of the pollution elements, As, Cd, and S, and the ratio of Ca/Al in aerosols and
soils in those sites located on the south of Jungger Basin as tracers, it was found that As, Cd, and S highly enriched in
the aerosols over urban Urumqi were not only from the re-suspended road dust but also from the soil transported from south
of the Jungger Basin. Different from the most cities in China, the high concentration of sulfate in Urumqi was partially from
the primary soil dust transported from the surrounding areas. The mixing of the local anthropogenic aerosols with the soil
transported from outside the city was the main source of the high sulfate concentration. Ammonium salts were higher than the
summed equivalents of SO42−, NO3−, and Cl− in Urumqi and much higher than that in other Chinese cities. The total water soluble ions and the total ammonium salts were
as high as 57.8% and 51.0% in PM2.5. The high concentration of soluble salts with high hygroscopicity, especially ammonium and sulfate salts, were the main factors
contributing to the heavy haze over Urumqi. 相似文献
13.
非球形气溶胶粒子散射特性及其等效Mie散射误差分析 总被引:3,自引:2,他引:1
为分析形状对气溶胶粒子散射特性的影响,采用T矩阵法计算了0.633μm波段(自然光)不同种类、形状的气溶胶单粒子与体散射的散射相函数,并讨论了气溶胶粒子形状畸变与等效Mie散射误差的变化规律。结果表明:粒子形状畸变对气溶胶粒子散射能量空间分布影响较大。对于单粒子,各散射角上的等效Mie散射误差并不随粒子形状畸变程度单调变化。从相对误差量级上看,形状畸变对180°散射的影响强于0°,对35°的散射影响相对较弱。对于两种非球形粒子等效方法,等表面积法优于等体积法。不同类型的非球形气溶胶粒子体散射存在显著差异,沙尘性与海洋性的等效Mie散射误差明显大于煤烟性与可溶性粒子;对于同一种气溶胶,形状的改变对侧向与后向散射影响显著,对前向散射影响不大。 相似文献
14.
Analyzed are the anomalies of monthly mean values of surface pressure over Eurasia in winter seasons of 1901–2010. It is noted
that the centers of large monthly positive pressure anomalies (16–24 hPa) are usually located within the 60°–70°N latitude
zone. The Siberian high is well developed but the pressure anomalies in its center amount to 3–8 hPa only. The large monthly
pressure anomalies at the isobaric surface of 500 hPa in the first natural synoptic area are mainly accompanied by the E-type of circulation (according to G.Ya. Vangengeim). The number of days with the western (W) type of circulation is extremely small and is practically absent when the anomalies in the center exceed 20 hPa (blocking
process). The time periods of increase (decrease) in the annual number of days with W-circulation are well agreed with the periods of the Earth rotation acceleration (deceleration). The positive pressure anomalies
were four or five times more frequent in the periods of the Earth angular velocity decrease: in 1933–1972 and after 2004. 相似文献
15.
Summary This study investigated the impact of atmospheric aerosols on surface ultraviolet (UV) irradiance at Gwangju, Korea (35°13′N,
126°50′E). Data analyzed included surface UV irradiance measured by UV radiometers from June 1998 to April 2001 and the aerosol
optical depth (AOD) in the visible range determined from a rotating shadow-band radiometer (RSR). The radiation amplification
factor (RAF) of ozone for UV-B (280–315 nm) at Gwangju was 1.32–1.62. Values of the RAF of aerosols (RAFAOD) for UV-A and UV-B were 0.18–0.20 and 0.22–0.26, respectively.
Authors’ addresses: Jeong Eun Kim, Advanced Environmental Monitoring Research Center (ADEMRC), Gwangju Institute of Science
and Technology (GIST) and Korea Meteorological Administration (KMA); Seong Yoon Ryu, Advanced Environmental Monitoring Research
Center (ADEMRC), Gwangju Institute of Science and Technology (GIST) and Division of Metrology, Korea Research Institute of
Standards and Science (KRISS); Young Joon Kim, Advanced Environmental Monitoring Research Center (ADEMRC) Gwangju Institute
of Science and Technology (GIST), 1 Oryong-dong, Buk-gu, Gwangju 500-712, Republic of Korea. 相似文献
16.
Continuous Measurement of Number Concentrations and
Elemental Composition of Aerosol Particles
for a Dust Storm Event in Beijing 总被引:1,自引:0,他引:1
A continuous measurement of number size distributions and chemical composition of aerosol particles was conducted in Beijing in a dust storm event during 21-26 March 2001. The number concentration of coarse particles ( 〉2μm) increased more significantly than fine particles ( 〈2μm) during the dust storm due to dust weather, while the anthropogenic aerosols collected during the non-dust-storm period tended to be associated with fine particles. Elemental compositions were analyzed by using proton-induced X-ray emission (PIXE). The results show that 20 elements in the dust storm were much higher than in the non-dust-storm period. The calculated soil dust concentration during the dust storm was, on average, 251.8μg m^-3, while it was only 52.1μg m^-3 on non-dust-storm days. The enrichment factors for Mg, A1, P, K, Ca, Ti, Mn, Fe, C1, Cu, Pb, and Zn show small variations between the dust storm and the non-dust-storm period, while those for Ca, Ni and Cr in the dust storm were much lower than those in the non-dust-storm period due to significant local emission sources. A high concentration and enrichment factor for S were observed during the dust storm, which implies that the dust particles were contaminated by aerosol particles from anthropogenic emissions during the long-range transport. A statistical analysis shows that the elemental composition of particles collected during the dust storm in Beijing were better correlated with those of desert soil colleted from desert regions in Inner Mongolia. Air mass back-trajectory analysis further confirmed that this dust storm event could be identified as streaks of dust plumes originating from Inner Mongolia. 相似文献
17.
Bertrand Bessagnet Laurent Menut Gabriele Curci Alma Hodzic Bruno Guillaume Catherine Liousse Sophie Moukhtar Betty Pun Christian Seigneur Michaël Schulz 《Journal of Atmospheric Chemistry》2008,61(3):175-202
In this study, an improved and complete secondary organic aerosols (SOA) chemistry scheme was implemented in the CHIMERE model.
The implementation of isoprene chemistry for SOA significantly improves agreement between long series of simulated and observed
particulate matter concentrations. While simulated organic carbon concentrations are clearly improved at elevated sites by
adding the SOA scheme, time correlation are impaired at low level sites in Portugal, Italy and Slovakia. At several sites
a clear underestimation by the CHIMERE model is noticed in wintertime possibly due to missing wood burning emissions as shown
in previous modeling studies. In Europe, the CHIMERE model gives yearly average SOA concentrations ranging from 0.5 μg
m
− 3 in the Northern Europe to 4 μg
m
− 3 over forested regions in Spain, France, Germany and Italy. In addition, our work suggests that during the highest fire emission
periods, fires can be the dominant source of primary organic carbon over the Mediterranean Basin, but the SOA contribution
from fire emissions is low. Isoprene chemistry has a strong impact on SOA formation when using current available kinetic schemes. 相似文献
18.
Observed and projected climate change in Taiwan 总被引:1,自引:0,他引:1
Summary
This study examined the secular climate change characteristics in Taiwan over the past 100 years and the relationship with
the global climate change. Estimates for the likelihood of future climate changes in Taiwan were made based on the projection
from the IPCC climate models.
In the past 100 years, Taiwan experienced an island-wide warming trend (1.0–1.4 °C/100 years). Both the annual and daily temperature
ranges have also increased. The warming in Taiwan is closely connected to a large-scale circulation and SAT fluctuations,
such as the “cool ocean warm land” phenomenon. The water vapor pressure has increased significantly and could have resulted
in a larger temperature increase in summer. The probability for the occurrence of high temperatures has increased and the
result suggests that both the mean and variance in the SAT in Taiwan have changed significantly since the beginning of the
20th century. Although, as a whole, the precipitation in Taiwan has shown a tendency to increase in northern Taiwan and to
decrease in southern Taiwan in the past 100 years, it exhibits a more complicated spatial pattern. The changes occur mainly
in either the dry or rainy season and result in an enhanced seasonal cycle. The changes in temperature and precipitation are
consistent with the weakening of the East Asian monsoon.
Under consideration of both the warming effect from greenhouse gases and the cooling effect from aerosols, all projections
from climate models indicated a warmer climate near Taiwan in the future. The projected increase in the area-mean temperature
near Taiwan ranged from 0.9–2.7 °C relative to the 1961–1990 averaged temperature, when the CO2 concentration increased to 1.9 times the 1961–1990 level. These simulated temperature increases were statistically significant
and can be attributed to the radiative forcing associated with the increased concentration of greenhouse gases and aerosols.
The projected changes in precipitation were within the range of natural variability for all five models. There is no evidence
supporting the possibility of precipitation changes near Taiwan based on the simulations from five IPCC climate models.
Received February 5, 2001 Revised July 30, 2001 相似文献
19.
Aerosol and rain samples were collected between 48°N and 55°S during the KH-08-2 and MR08-06 cruises conducted over the North
and South Pacific Ocean in 2008 and 2009, to estimate dry and wet deposition fluxes of atmospheric inorganic nitrogen (N).
Inorganic N in aerosols was composed of ~68% NH4+ and ~32% NO3– (median values for all data), with ~81% and ~45% of each species being present on fine mode aerosol, respectively. Concentrations
of NH4+ and NO3− in rainwater ranged from 1.7–55 μmol L−1 and 0.16–18 μmol L−1, respectively, accounting for ~87% by NH4+ and ~13% by NO3− of total inorganic N (median values for all data). A significant correlation (r = 0.74, p < 0.05, n = 10) between NH4+ and methanesulfonic acid (MSA) was found in rainwater samples collected over the South Pacific, whereas no significant correlations
were found between NH4+ and MSA in rainwater collected over the subarctic (r = 0.42, p > 0.1, n = 6) and subtropical (r = 0.33, p > 0.5, n = 6) western North Pacific, suggesting that emissions of ammonia (NH3) by marine biological activity from the ocean could become a significant source of NH4+ over the South Pacific. While NO3− was the dominant inorganic N species in dry deposition, inorganic N supplied to surface waters by wet deposition was predominantly
by NH4+ (42–99% of the wet deposition fluxes for total inorganic N). We estimated mean total (dry + wet) deposition fluxes of atmospheric
total inorganic N in the Pacific Ocean to be 32–64 μmol m−2 d−1, with 66–99% of this by wet deposition, indicating that wet deposition plays a more important role in the supply of atmospheric
inorganic N than dry deposition. 相似文献
20.
P. D. Safai S. Kewat G. Pandithurai P. S. Praveen K. Ali S. Tiwari P. S. P. Rao K. B. Budhawant S. K. Saha P. C. S. Devara 《Journal of Atmospheric Chemistry》2008,61(2):101-118
Simultaneous measurements on physical, chemical and optical properties of aerosols over a tropical semi-arid location, Agra
in north India, were undertaken during December 2004. The average concentration of total suspended particulates (TSP) increased
by about 1.4 times during intense foggy/hazy days. Concentrations of SO4
2−, NO3
−, NH4
+ and Black Carbon (BC) aerosols increased by 4, 2, 3.5 and 1.7 times, respectively during that period. Aerosols were acidic
during intense foggy/hazy days but the fog water showed alkaline nature, mainly due to the neutralizing capacity of NH4 aerosols. Trajectory analyses showed that air masses were predominantly from NW direction, which might be responsible for
transport of BC from distant and surrounding local sources. Diurnal variation of BC on all days showed a morning and an evening
peak that were related to domestic cooking and vehicular emissions, apart from boundary layer changes. OPAC (Optical properties
of aerosols and clouds) model was used to compute the optical properties of aerosols. Both OPAC-derived and observed aerosol
optical depth (AOD) values showed spectral variation with high loadings in the short wavelengths (<1 μm). AOD value at 0.5 μm
wavelength was significantly high during intense foggy/hazy days (1.22) than during clear sky or less foggy/hazy days (0.63).
OPAC-derived Single scattering albedo (SSA) was 0.84 during the observational period, indicating significant contribution
of absorbing aerosols. However, the BC mass fraction to TSP increased by only 1% during intense foggy/hazy days and thereby
did not show any impact on SSA during that period. A large increase was observed in the shortwave (SW) atmospheric (ATM) forcing
during intense foggy/hazy days (+75.8 W/m2) than that during clear sky or less foggy/hazy days (+38 W/m2), mainly due to increase in absorbing aerosols. Whereas SW forcing at surface (SUF) increased from −40 W/m2 during clear sky or less foggy/hazy days to −76 W/m2 during intense foggy/hazy days, mainly due to the scattering aerosols like SO4
2-. 相似文献