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1.
The chemical composition of cloudwater in the Sierra Nevada is dominated by NO3, SO42−, and NH4+. Cloudwater pH is determined largely by the balance between the concentrations of these three species, although inputs of formic and acetic acid also are believed to be important, particularly when anthropogenic inputs are small. Cloudwater samples collected in Sequoia National Park (SNP) exhibited pH values ranging from 3.9 to 6.5; Yosemite National Park (YNP) cloudwater samples had pH values ranging from 3.8 to 5.2. Samples collected at YNP were more acidic than those collected at SNP. The difference in pH between the two regions appears to be due to relatively small differences in inputs of NO3, SO42−, and NH4+. In the absence of inputs of NH3, cloudwater pH values in the Sierra may fall below 3.Over 250 h of cloud interception were observed during a 12 month period at a cloud monitoring site at 1856 m elevaton in SNP. Estimates of cloudwater deposition of NO3, SO42−, and NH4+ indicate that cloud interception contributes significantly to regional acid deposition for closed forest canopies. Cloud interception may be the dominant deposition mechanism for isolated conifers and ridgetop canopies, where wind speeds are higher and cloudy air parcels can impact directly on foliar surfaces.  相似文献   

2.
The precipitation chemistry of Greater Manchester, a Metropolitan County in the northwest of England, has been examined for small scale spatial variability using a network of 18 bulk precipitation collectors. Significant spatial variability was found for concentrations of non-marine SO42−, NO3, NH4+, Ca2+ and H+ ions. The statistical associations between the data were investigated using correlation, partial correlation and principal components analyses. It was found that zero-order correlation coefficients were inadequate for the interpretation of the data and that the computation of first, and higher order partial correlation coefficients was necessary in order to explain the interrelationships between the data and their spatial variability. The statistical associations between the data suggest relationships between Ca2+ and non-marine SO42−, and NO3+ in precipitation which are discussed in terms of their possible precursor species. Potential source effects were examined in conjunction with atmospheric removal processes. The dry deposition of SO4 particles, rather than the dry deposition of SO2, may explain the spatial variability of non-marine SO42−. The erosion of CaSO4 formed from the reaction of SO2 with CaCO3 on urban surfaces with subsequent resuspension is thought to be the basis of the relationship between Ca2+ and non-marine SO42− concentrations in precipitation. The wet and dry deposition of CaCO3 particles from local sources may be partially responsible for the spatial variability of H+, and dry deposition and scavenging of NH3, in conjunction with the predominant wind direction may explain the spatial variability of NO3 and NH4+ ions. Ammonia is thought to originate from sources both outside the study area and within it.  相似文献   

3.
Chemical composition of precipitation in Albany, NY from July 1986 to December 1988 has been studied. Mean volume-weighted concentrations (μeqℓ−1) were: acidity, 104.0; alkalinity, −63.7; SO42−, 52.8; NO3, 29.8; Cl, 5.6; F, 0.50; NH4+, 19.3; Ca2+, 6.5; Mg2+, 2.8; Na+, 3.5; and K+, 1.4. Mean pH was 4.2 . Seasonal patterns were pronounced for most species. Concentrations of H+, SO42−, NO3, NH4+ and Ca2+ peaked in the summer and spring. Deposition was related to rainfall amount by a power law relationship in which the exponent of the equation was ∮.6. Wet SO42− deposition was 2.35 keq ha−1 over a 30-month period. The SO42− and NO3 deposition rates observed at Albany indicate that transport from midwestern sources have a major influence at this site. On the average, free H+ ion concentrations determined from pH measurements accounted for 51% of the measured total acidity. There were unknown species, most likely organic acids, that could contribute to the acidity. Correlation and regression analyses indicated that major anions, SO42− and NO3, were closely associated with H+ and NH4+ ions. Factor analysis revealed four common factors which are related to fossil-fuel combustion, sea spray, cement factory and biomass burning.  相似文献   

4.
Wet precipitation was collected in Thessaloniki, Greece, during the period March 1989–December 1990 by using an automatic wet-only precipitation sampler.Rainwater samples were analysed for major cations (H+, NH4+, Na+, K+, Ca2+, Mg2+) and anions (Cl, NO3, SO42−), in addition to acidity and conductivity measurements. The majority of rain had a neutral or alkaline character as a result of neutralization, primarily caused by calcareous soil dust and secondarily by atmospheric ammonia. In all rain, SO42− concentration exceeded NO3 concentration. The contribution of maritime sources to the total SO42− concentration was very low (<2%).The chemical composition of precipitation was analysed in conjunction with meteorological variables (season of the year, precipitation type, airflow patterns) to evaluate temporal variations and chemical source influence. Rain caused by weak, localized flows showed the highest acidity and the minimum influence of neutralization processes.  相似文献   

5.
Fog, aerosol, and gas samples were collected during the winter of 1986 at Riverside, California. The dominant components of the aerosol were NH4+, NO3, and SO42−. Gaseous NH3 was frequently present at levels equal to or exceeding the aerosol NH4+. Maximum level were 3800, 3100, 690 and 4540 neq m−3 for NH4+, NO32− and NH3(g), respectively. The fogwater collected at Riverside had very high concentrations, particularly of the major aerosol components. Maximum concentrations were 26,000 29,000 and 6200 μM for NH4+, NO3 and SO42−, respectively. pH values in fogwater ranged from 2.3 to 5.7. Formate and acetate concentrations as high as 1500 and 580 μM, respectively, were measured. The maximum CH2O concentration was 380 μM. Glyoxal and methylglyoxal were found in all the samples; their maximum concentrations were 280 and 120 μM, respectively. Comparison of fogwater and aerosol concentrations indicates that scavenging of precursor aerosol by fog droplets under the conditions at Riverside is less than 100% efficient.The chemistry at Riverside is controlled by the balance between HNO3 production from NOx emitted throughout the Los Angeles basin and NH3 emitted from dairy cattle feedlots just west of Riverside. The balance is controlled by local mixing. Acid fogs result at Riverside when drainage flows from the surrounding mountains isolate the site from the NH3 source. Continued formation of HNO3(g) in this air mass eventually depletes the residual NH3(g). A simple box model that includes deposition, fog scavenging, and dilution is used to assess the effect of curtailing the dairy cattle feedlot operations. The calculations suggest that the resulting reduction of NH3 levels would decrease the total NO3 in the atmosphere, but nearly all remaining NO3 would exist as HNO3. Fogwater in the basin would be uniformly acidic.  相似文献   

6.
Precipitation samples at an urban Chicago site and a nearby suburban site were compared in order to examine the influence of emissions within a large urban area on local precipitation chemistry. Precipitation samples were collected from June 1981 to May 1982, initially for events and subsequently weekly, and precipitation-weighted concentrations (PWCs) of the major chemical constituents were calculated from concurrent urban-suburban pairs of samples, stratified according to the estimated mixed-layer wind quadrant. Overall, PWCs at the urban site were higher than those at the suburban site for Ca2+, Mg2+, NH4+, NO3 and Cl; approximately equal for Na+ and SO42−; and lower for H+. For precipitation in southwesterly flow, in which the suburban site was upwind of the urban site and most urban emissions, PWCs of all species except Na+ were higher at the urban site. For the few precipitation cases in northeasterly flow, however, differences between sites did not have a pattern consistent with a reversal in the upwind-downwind relationship.  相似文献   

7.
Daily measurements the atmospheric cocnentrations of HNO3, NO3-, NO2, SO2, SO42−, NH4+, and several trace metals were made at the University of Michigan Biological Station over a 124-day period during the 1984–1985 winter. The composition of the daily precipitation was also determined. The relative contributions of scavenged NO3 and HNO3 to the precipitation was estimated by assuming that the NO3 scavenging ratio was the same as that of trace metals with a similar particle size. Similarly, the SO42− and SO2 contributions were based on the scavenging ratios of NH4+ and trace metals. On this basis, it was determined that the event median NO3 and HNO3 scavenging ratios were 500 and 3500, respectively. HNO3 scavenging accounted for 83% of the total scavenged NO3. Scavenging of SO42− accounted for all the snow SO42− in 67% of the events. In the remaining events, some SO2 was scavenged, with a median scavenging ratio of 219. Overall, 67% of the snowfall acidity appeared to be due to HNO3 scavenging. Backward air-mass trajectories that were calculated for each event were used to determine the general source regions of the acidic species. Snow associated with air masses from the south and west accounted for 81 and 75% of the deposited NO3 and SO42−, respectively.  相似文献   

8.
Wet precipitation-only samplers were used to collect wet deposition at two sites in the Athens basin, Greece for the period March 1986–February 1987.Concentrations of major cations (H+, NH+4, Na+, K+, Ca2+ and Mg2+) and major anions (Cl, NO3 and SO2−4) were determined for the first time in rainwater samples in Greece. Bicarbonate concentrations were calculated. The relative importance of natural and anthropogenic sources were estimated by a chemical balance. The majority of rain collected has a neutral or alkaline character. Acidity was due to the presence of H2SO4 and HNO3. The statistical analysis of the correlation between the concentration of chemical species confirm the influence of natural and anthropogenic sources. In all samples, SO2−4 concentrations exceed NO3 concentrations despite the dominance of low S oil burning in the region. The wet flux of S was calculatd to be 0.34 gm−2a−1.  相似文献   

9.
Monthly mean chemical composition of aerosol with diameter less than 8 μm was identified in Sapporo in 1982. The mass of aerosol was made up of nine components: elemental C, organics, SO42−, NO3, NH4+, Cl, Na+, soil particles and water. The concentrations of carbonaceous particles (elemental C and organics) was relatively high (12.7–16.0μ m−3) in autumn and winter (October–February) due to emission from domestic heating and comprised 36–41% of total aerosol mass. Higher concentration of soil particles was observed in spring (March–May) (9.7–13.1 μg m−3) and comprised 22–29% of total aerosol mass due to suspension by strong wind. On the other hand, the concentration of excess SO42− (non-sea salt SO42−), which ranged from 2.6–5.2 μg m−3, did not change remarkably with season, and the fraction of excess sulfate increased to 21% in summer (July–August) probably due to photochemical transformation from SO2. Nitrate concentration was far less than that of SO42− throughout the year in Sapporo.  相似文献   

10.
Rainwater samples in S. Paulo city were collected on an event basis from October 1983 to October 1985 covering two dry and two rainy periods. Bulk samples only were obtained. At the same site and period, fine, coarse and inhalable particles were also collected. Na+, Ca2+, K+, Mg2+, NO3, SO42− and NH4+ contents were determined in rainwater samples, while Na, Ca, K, Cl and S concentrations were measured in aerosol samples. Rainwater is slightly acid (mean pH = 5.0), and contains high concentrations of Ca2+, NO3, SO42− and NH4+. Dry and wet fluxes and washout ratios were determined for some elements. Results obtained suggest that the atmospheric composition in this city is strongly influenced by anthropogenic sources.  相似文献   

11.
Measurements of inorganic aerosol and gas phase species are presented for three sites in central California during a 4 day period in April 1988. The measurement sites were located along an east-west transect at Visalia, Ash Mountain, and Lower Kaweah, with elevations of 90, 550 and 1900 m, respectively. Aerosol compositions were nearly neutral at all locations, however large concentrations of NH3 at Visalia contributed significant excess alkalinity to the air mass sampled there. Concentrations of all major species were observed to decrease with elevation during most of the sampling periods. Concentrations at the upper two sites exhibited diurnal fluctuations, with peaks in the late afternoon, consistent with the transport of pollutants from San Joaquin Valley sources by daytime upslope winds. Concentrations of most of these species reached a maximum at the elevated sites on 28 April, as a weak cold front approached, reducing the atmospheric stability over the valley floor. Concentrations at Visalia on this day were somewhat lower than those observed earlier in the week.Clouds intercepting the mountain slopes on 28 April were sampled at two locations. The coudwater pH at both sites was observed to fall throughout the event, dropping as low as 4.34. Precursor concentrations of aerosol NO3, SO42- and NH4+, and gas phase HNO3 and NH3, were sufficient to account for the observed cloudwater loadings of NO3, SO42- and NH4+. In-cloud measurements made near the cloud base indicated a considerable S(IV) oxidation potential in the form of H2O2, but only low S(IV) concentrations. Cloudwater concentrations of formic acid were approximately three times acetic acid concentrations. Carbonyl concentrations were dominated by formaldehyde and glyoxal.  相似文献   

12.
The use of filter packs and a cascade impactor during a series of research cruises in the southern area of the North Sea has yielded detailed spatial distribution patterns of aerosol concentrations, Cl, NO3, SO42−1 and NH4+ and gaseous concentrations, HCl, HNO3 and NH3. The overall distribution of the atmospheric concentrations closely parallels published modelled results for metallic species. The chemical transformations of these aerosols and gases are investigated together with their interactions with the seasalt aerosol. Aerosol chloride loss is greatest in the more polluted areas, whilst concentrations products of NH3 with HNO3 and HCl appear insufficient to sustain the existence of NH4NO3 and NH4Cl. Nitrate is associated predominantly with larger particles and appears to be present substantially as a surface coating on marine aerosol. The total dry deposition input for nitrogen species is calculated for the southern sector with extrapolation to the whole of the North Sea, using particle size weighted deposition velocities of 0.63 and 0.21 cm s−1 for NO3−1 and NH4+, respectively, and literature-derived values for the gaseous constituents. Finally the use of air-mass back trajectories illustrates the role of source regions in influencing the chemical composition of the North Sea atmosphere.  相似文献   

13.
Urban sampling sites have been specifically excluded from recent large networks for measuring chemical composition of precipitation. Because information on precipitation composition in urban areas is needed for a variety of current applications, it is useful to summarize present knowledge. Most of the available information is based on samples of bulk precipitation, collected by continuously open collectors. This method is now widely acknowledged to be of limited value because of its poor sampling characteristics for dry deposition. For many ions, particularly those residing on large airborne particles, urban bulk sampling yielded considerably higher concentrations than found in samples collected in ‘wet-only’ samplers. Spatial variability of ionic concentrations in urban areas is expressed in terms of the sample standard deviation of site precipitation-weighted means, as a percentage of the overall urban mean. Median values of the most major ions were near 30%; half of the available measurements were between 20 and 47%. Differences between urban and nearby rural concentrations of ions in precipitation were often reported. Those ions with some tendency to occur in higher concentrations in cities included Na+, Mg2+, Ca2+, NO3, SO42− and Cl. These differences should be viewed with caution, however, because they were usually based on one or two, possibly unrepresentative, rural sampling sites. Seasonal variations of urban [H+] were different in Europe and the U.S. Highest concentrations occurred in winter in Europe, but in summer in the U.S. There is a pressing need for additional urban precipitation chemistry monitoring and research.  相似文献   

14.
Scavenging of sulfates and nitrates—two most common ions leading the cloudwater acidity—was investigated during field studies atop a site in Mt. Mitchell (35°44′05″N, 82°17′15″W) State Park where the highest peak (2038 m MSL) of the eastern U.S. is located. Experiments were conducted during the growing seasons (15 May–30 September) of 1986 and 1987 using an instrumented meteorological tower (16.5 m tall) and a passive cloudwater collector. A cloud episode that occurred on 12 October 1987, was also comprehensively investigated. Clouds were frequently observed in which the Fraser fir and red spruce stands stayed immersed 28% and 41% of the time during the 1986 and 1987 seasons, respectively. Rate of cloudwater deposition on the forest canopy was determined using an inferential cloud deposition model. It was found by analysing nine short duration (lasting 8 h or less) and 16 long duration cloud events that the ionic concentration (SO42− and NO3) is inversely proportional to the rate (Ic) of cloudwater deposition (in mm h−1) and can be expressed by the following relationship: [SO42−] = aIcb or [NO3] = aIcb. Theoretical arguments leading to these relationships are presented. The b values for predicting NO32− concentration are found in the range of 0.14–1.24 (mean = 0.48) for short duration and 0.062–0.63 (mean = 0.27) for long duration cloud events, respectively. The corresponding b values for predicting NO3 concentrations are 0.19–1.16 (mean = 0.49) and 0.072–0.59 (mean = 0.27), respectively. When the b parameter was between 0.2 and 0.6, the correlation coefficients between measured and predicted ionic concentrations were found to exceed 0.7. The parameter a is shown to represent the maximum ionic flux for a given cloud event. The ratio of the a parameter for SO42− to NO3 varied between 1.75 and 6.95, indicating that the SO42− contributes to the total ionic concentration substantially more than the NO3 leading to the conclusion that the cloudwater acidity is primarily due to the presence of sulfuric acid which has been demonstrated to cause foliar injury and growth retardation in red spruce trees. The above parameterization is similar to the one that is frequently used to relate ionic concentration in precipitation to the rainfall rate. In order to understand physico-chemical processes leading to the proposed parameterization schemes, meteorological and chemical variables are comprehensively analysed for one short duration and two long duration cloud events. The concentrations of principal ions (SO42−, NO3, H+ and NH4+) during the short duration cloud events were found to be much higher than those during the long duration ones, especially at colder temperatures. Such short cloud events have a potential of causing foliar narcosis in red spruce stands because of unusually acidic cloudwater to which these stands stay exposed intermittently during each growing season.  相似文献   

15.
As part of the second Arctic Gas and Aerosol Sampling Program (AGASP-II), Arctic aerosol samples were collected by the NOAA WP-3D aircraft in spring 1986. The samples were analyzed in bulk and individual-particle form, using ion chromatography (IC) and electron microscopy (EM), respectively. Information on the chemical composition of the aerosol as determined by various techniques is presented, as well as morphology, concentration, and size distribution data obtained from individual particle analyses. For most flights, a stratospheric sample and a haze profile samople were collected. Haze samples exhibited greater particle concentrations than stratospheric samples, the highest concentrations in haze reaching ∼103 cm−3 (non-volatile particles > 0.05 μm diam). Sulfur was consistently observed to be a major element in both large and small particles in haze samples. Crustal elements such as Si, Al, K, Ca and Fe were often present in significant concentrations together with S. Particles that did not emit X-rays, possibly organic or sooty C, were observed in significant concentrations in both tropospheric and stratospheric samples. Chemical spot tests confirmed that SO42− was the major S-containing species and that NO3 was not nearly as prevalent as SO42− in the Arctic aerosol particles. The mass concentrations of major anions (Cl, SO42− and NO3) and cations (Na+, K+, NH4+, Ca2+ and Mg2+) in the bulk aerosols were determined using IC. The ratios between ion concentrations, e.g. Ca2+/Na+, SO42−/Na+ and Cl/Na+, may serve as indicators of aerosol origins and mixing status of various air masses. Aerosols collected on six flights demonstrated variability of particle characteristics in relation to sources and transport of Arctic haze.  相似文献   

16.
Measurements of wet deposited NH4+, SO42−, NO3 and Cl, as well as airborne concentrations of these species and gaseous HNO3, HCl and NH3, have been made at a site in eastern England. Scavenging ratios based solely upon aerosol-associated species and upon aerosol plus gaseous airborne species are presented and compared with literature values. It appears that HCl and HNO3 have only a rather minor influence upon wet deposition at our site. Gaseous NH3 influences ground-level air chemistry appreciably, but scavenging ratios for NH4+ are low, even when based upon aerosol NH4+ concentrations alone, presumably due to altitudinal gradients in this species. The problems inherent in interpretation of scavenging ratios are discussed. Deposition of nitrogen in various chemical forms is estimated from rainwater and air composition. If a transport-limited deposition velocity is assumed for ammonia gas, dry deposition of this species accounts for around 40% of total nitrogen deposition to the ground.  相似文献   

17.
Current knowledge regarding deposition of atmospheric pollutants to mountain ecosystem is reviewed focusing on the mountains of eastern North America. Despite a general paucity of published data on the subject, some generalization emerge. Wet deposition (i.e. precipitation input) of SO42−, NO3, H+ and Pb tends to increase with elevation, primarily because of the orographic increase in precipitation amount. Cloud water deposition of these substances can be very significant for mountain forests, but is highly variable spatially because of its strong dependence on wind speed, cloud characteristics, and vegetation canopy structure, which are all heterogeneously distributed. Dry deposition has not been quantified sufficiently to draw empirical generalizations, but the processes involved are discussed with regard to expected elevational trends. Based on the few studies in which total annual deposition (wet, dry, plus cloud water inputs for an entire year) has been measured, it appears that some high-elevation sites in the Appalachian Mountains receive substantially more SO42−, NO3+ deposition than do typical low-elevation sites. The amount of elevational increase depends largely on the amount of cloud water deposition at the mountain site. Data from two clusters of sites in the northern Appalachians indicate that total deposition of SO42−, NO3, and H+ to mountaintop sites is typically 3–7 times greater than deposition to nearby lowland sites. Similarly, some studies of Pb accumulation in organic soil horizons suggest a two- to four-fold increase from lowlands to mountaintops. Deposition in mountain areas can be highly variable over short distances because of the patchiness of meteorological conditions and vegetation canopy characteristics, and also because exposed trees and forest edges can receive deposition loads much higher than the landscape average. Night-time and early-morning O3 concentrations are greater at high-elevation than at low-elevation sites. Daytime O3 levels are equal or slightly higher at high-elevation sites. Additional studies are suggested which would allow better characterization of pollutant exposure along elevational gradients.  相似文献   

18.
The wet, dry and cloud water deposition of acidic substances on the forest canopy are considered as major mechanisms for pollutant induced forest decline at high elevations. Direct cloud capture plays a predominant role of intercepting acidic substances in above cloud-base forests. We conducted a field study at Mt. Mitchell, North Carolina (35°44′05″N, 82°17′15″W; 2038 m MSL)—the highest peak in the eastern U.S.—during May–September 1986 and 1987 in order to analyze the chemistry of clouds in which the red spruce and Fraser fir stands stay immersed. It was found that Mt. Mitchell was exposed to cloud episodes 71% of summer days, the cloud immersion time being 28% for 1986 (a record drought summer in southeastern U.S.) and 41% for 1987. Sulfate, NO3, NH4+ and H+ ions were found to be the major constituents of the cloud water, which was collected atop a 16.5 m tall meteorological tower situated among 6–7 m tall Fraser fir trees. The initiation of precipitation in clouds invariably diluted the cloud water acidity. The cloud water pH during short episodes (8 h duration or less), which resulted from the orographic lifting mechanisms, was substantially lower than that during long episodes, which were associated with meso-scale and synoptic-scale disturbances. Sulfate accounted for 65% acidity in cloud water, on the average, and contributed 2–3 times more than the NO3. Inferential micrometeorological models were used to determine deposition of SO42− and NO3 on the forest canopy and the hydrological input due to direct cloud capture mechanism. The cloud water deposition ranged between 32 and 55 cm a−1 in contrast to the bulk precipitation which was about 130 cm a−1 as measured by an on-site NADP (National Atmospheric Deposition Program) collector. For S compounds, wet, dry and cloud water deposition accounted for 19%, 11% and 70%, respectively for 1986, and 16%, 8% and 76%, respectively for 1987. For N compounds, dry deposition contributed 35% and 23% for 1986 and 1987, respectively, whereas, cloud water deposition contributed 50% and 65% for 1986 and 1987, respectively. Our estimates are compared with the reported literature values for the other sites.  相似文献   

19.
An iterative least-squares method with a receptor model was applied to the analytical data of the precipitation samples collected at 23 points in the suburban area of Tokyo, and the number and composition of the source materials were determined. Thirty-nine monthly bulk precipitation samples were collected in the spring and summer of 1987 from the hilly and mountainous area of Tokyo and analyzed for Na+, K+, NH4+, Mg2+, Ca2+, F, Cl, Br, NO3 and SO42− by atomic absorption spectrometry and ion chromatography. The pH of the samples was also measured. A multivariate ion balance approach (Tsurumi, 1982, Anal. Chim. Acta138, 177–182) showed that the solutes in the precipitation were derived from just three major sources; sea salt, acid substance (a mixture of 53% HNO3, 39% H2SO4 and 8% HCl in equivalent) and CaSO4. The contributions of each source to the precipitation were calculated for every sampling site. Variations of the contributions with the distance from the coast were also discussed.  相似文献   

20.
Because the composition of precipitation reflects the composition of the atmosphere, polar ice cores provide a useful way of investigating past and present atmospheres. We have measured concentrations of major ions in nine sections of a central Greenland ice core and we found that concentrations of both SO42− and NO3 have increased dramatically over the last 250 years, up to three to four times the 18th century levels. Large changes have also occurred in the average concentrations of several other chemical species, such as NH4+, excess Cl, and Ca2+. We used a principal-component analysis to characterize variations of the season of maximum deposition rate of HNO3 and H2SO4 to the snow. We found that source fluctuations of H2SO4 are faithfully recorded in the Greenland snow and appear to switch their preferential time of deposition in the snow from summer to winter early in the 20th century. On the other hand, HNO3 is deposited preferentially during summer throughout the core, emphasizing the role of photochemistry in understanding nitrogen cycling in the Arctic. Anthropogenic inputs have clearly modified the behavior of several chemical compounds in the atmosphere.  相似文献   

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