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1.
Kentaro Hayashi Nobuhisa Koga Yosuke Yanai 《Atmospheric environment (Oxford, England : 1994)》2009,43(35):5702-5707
The present study aimed to investigate the NH3 volatilization loss from field-applied compost and chemical fertilizer and evaluate the atmosphere–land exchange of NH3 and particulate NH4+ (pNH4) at an upland field with volcanic ash soil (Andosol) in Hokkaido, northern Japan. Two-step basal fertilization was conducted on the bare soil surface. First, a moderately fermented compost of cattle manure was applied by surface incorporation (mixing depth, 0–15 cm) at a rate of 117 kg N ha−1 as total nitrogen (T-N) corresponding to 9.9 kg N ha−1 as ammoniacal nitrogen (NH4–N). Twelve days later, a chemical fertilizer containing 10% (w/w) of NH4–N as a mixture of ammonium sulfate and ammonium phosphates was applied by row placement (cover depth, 3 cm) at a rate of 100 kg N ha−1 as NH4–N. The study period was divided into the first-half, beginning after the compost application (CCM period), and the second-half, beginning after the chemical fertilizer application (CF period). The mean air concentrations of NH3 and pNH4 (1.5 m height) were 7.6 and 3.0 μg N m−3, respectively, in the CCM period; the values were 3.7 and 3.9 μg N m−3, respectively, in the CF period. The composition ratios of NH3 to the sum of NH3 and pNH4 (1.5 m height) were 72% and 49% in the CCM and CF periods, respectively. The NH3 volatilization loss from the compost was 0.8% of the applied T-N (or 9.3% of the applied NH4–N) and that from the chemical fertilizer was near zero. Excluding the period immediately after the compost application, the upland field acted as a net sink for NH3 and pNH4. 相似文献
2.
Allen AG Machado CM Cardoso AA 《Environmental pollution (Barking, Essex : 1987)》2011,159(5):1190-1197
Increased reactive nitrogen (Nr) deposition due to expansion of agro-industry was investigated considering emission sources, atmospheric transport and chemical reactions. Measurements of the main inorganic nitrogen species (NO2, NH3, HNO3, and aerosol nitrate and ammonium) were made over a period of one year at six sites distributed across an area of ∼130,000 km2 in southeast Brazil. Oxidized species were estimated to account for ∼90% of dry deposited Nr, due to the region’s large emissions of nitrogen oxides from biomass burning and road transport. NO2-N was important closer to urban areas, however overall HNO3-N represented the largest component of dry deposited Nr. A simple mathematical modeling procedure was developed to enable estimates of total Nr dry deposition to be made from knowledge of NO2 concentrations. The technique, whose accuracy here ranged from <1% to 29%, provides a useful new tool for the mapping of reactive nitrogen deposition. 相似文献
3.
Assessment of traffic-related air pollution in the urban streets before and during the 2008 Beijing Olympic Games traffic control period 总被引:8,自引:0,他引:8
In order to investigate the air quality and the abatement of traffic-related pollution during the 2008 Olympic Games, we select 12 avenues in the urban area of Beijing to calculate the concentrations of PM10, CO, NO2 and O3 before and during the Olympic traffic controlling days, with the OSPM model.Through comparing the modeled results with the measurement results on a representative street, the OSPM model is validated as sufficient to predict the average concentrations of these pollutants at street level, and also reflects their daily variations well, i.e. CO presents the similar double peaks as the traffic flow, PM10 concentration is influenced by other sources. Meanwhile, the model predicts O3 to stay less during the daytime and ascend in the night, just opposite to NO2, which reveals the impact of photochemical reactions. In addition, the predicted concentrations on the windward side often exceed the leeward side, indicating the impact of the special street shape, as well as the wind.The comparison between the predicted street concentrations before and during the Olympic traffic control period shows that the overall on-road air quality was improved effectively, due to the 32.3% traffic flow reduction. The concentrations of PM10, CO and NO2 have reduced from 142.6 μg m−3, 3.02 mg m−3 and 118.7 μg m−3 to 102.0 μg m−3, 2.43 mg m−3 and 104.1 μg m−3. However, the different pollutants show diverse changes after the traffic control. PM10 decreases most, and the reduction effect focusing on the first half-day even clears the morning peak, whereas CO and NO2 have even reductions to minify the daily fluctuations on the whole. Opposite to the other pollutants, ozone shows an increase of concentration. The average reduction rate of PM10, CO, NO2 and O3 are respectively 28%, 19.3%, 12.3% and −25.2%. Furthermore, the streets in east, west, south and north areas present different air quality improvements, probably induced by the varied background pollution in different regions around Beijing, along with the impact of wind force. This finding suggests the pollution control in the surrounding regions, not only in the urban area. 相似文献
4.
I-Fang Mao Chih-Hung Lin Chun-Ji Lin Yi-Ju Chen Fung-Chang Sung Mei-Lien Chen 《Atmospheric environment (Oxford, England : 1994)》2009,43(35):5622-5629
Metropolitan Taipei, which is located in the subtropical area, is characterized by high population and automobile densities. For convenience, most primary schools are located near major roads. This study explores the exposure of acid aerosols for schoolchildren in areas in Taipei with different traffic densities. Acid aerosols were collected by using a honeycomb denuder filter pack sampling system (HDS). Experimental results indicated that the air pollutants were significantly correlated with traffic densities. The ambient air NO2, SO2, HNO3, NO3−, SO42−, and aerosol acidity concentrations were 31.3 ppb, 4.7 ppb, 1.3 ppb, 1.9 μg m−3, 18.5 μg m−3, and 49.5 nmol m−3 in high traffic density areas, and 6.1 ppb, 1.8 ppb, 0.9 ppb, 0.7 μg m−3, 8.8 μg m−3 and 14.7 nmol m−3 in low traffic density areas. The exposure levels of acid aerosols for schoolchildren would be higher than the measurements because the sampling height was 5 m above the ground. The SO2 levels were low (0.13–8.03 ppb) in the metropolitan Taipei. However, the SO42− concentrations were relatively high, and might be attributed to natural emissions of sulfur-rich geothermal sources. The seasonal variations of acid aerosol concentrations were also observed. The high levels of acidic particles in spring time may be attributed to the Asian dust storm and low height of the mixture layer. We conclude that automobile contributed not only the primary pollutants but also the secondary acid aerosols through the photochemical reaction. Schoolchildren were exposed to twice the acid aerosol concentrations in high traffic density areas compared to those in low traffic density areas. The incidence of allergic rhinitis of schoolchildren in the high traffic density areas was the highest in spring time. Accompanied by high temperature variation and high levels of air pollution in spring, the health risk of schoolchildren had been observed. 相似文献
5.
A series of experiments using bulk precipitation collectors of the type used in the UK precipitation chemistry network measured the amounts of NH4+, SO42− and other ions that could be washed from funnels (diameter 15 cm) exposed to a wide range of NH3 and SO2 concentrations over periods from hours to days. In dry conditions, the average deposition flux of NH3 was between 50 and 120 nmol NH4+ funnel−1 d−1 (0.1–0.3 kg N ha−1 yr−1), and was independent of the concentration of NH3. Dry deposition of NH3 to wet funnels at small NH3 concentrations was almost 5 times that to dry funnels under the same conditions (average 240 nmol funnel−1 d−1; 0.7 kg ha−1 yr−1), and increased with increasing NH3 concentrations. The amount of NH4+ ions remaining on the funnel surface was inversely proportional to the vapour pressure deficit during the experiment. This result was interpreted as a dependence on the duration of surface wetness, with greater deposition of NH4+ when evaporation rates of surface water were small.The amount of SO2 deposited on funnel surfaces was closely related to the amount of NH3 deposited, in both wet and dry conditions, but was not strongly correlated with the SO2 concentration. At low NH3 and SO2 concentrations the average deposition to dry funnels was 70 nmol SO42− funnel−1 d−1 (0.5 kg ha−1 yr−1), and to wet funnels was approximately 2.5 times larger. The results are interpreted in terms of the balance between the rate of evaporation of surface water, and the rate of oxidation of SO2, which leads to the ‘fixing’ of NH4+ ions on the surface as involatile salts.It is predicted that dry deposition of NH3 to funnel surfaces across the UK Secondary Network could account for as much as one-half of the measured bulk wet deposition at sites where wet deposition of NH4–N is small. The amount of dry deposition depends on how long and how often funnel surfaces are wetted by rain or dew, and on the air concentrations of NH3. These predictions are based on funnels being wetted only once per day. More frequent wetting would increase the contribution from dry deposition, and the consequent overestimate of wet deposition of NH4–N across the UK by using data obtained from bulk collectors. To some extent this overestimate may be offset by microbial degradation and loss of NH4–N in weekly bulk precipitation samples during collection and storage. 相似文献
6.
Nitric oxide and nitrous oxide emission from Hungarian forest soils; linked with atmospheric N-deposition 总被引:1,自引:0,他引:1
Lszl Horvth Ern Führer Kate Lajtha 《Atmospheric environment (Oxford, England : 1994)》2006,40(40):7786-7795
Studies of forest nitrogen (N) budgets generally measure inputs from the atmosphere in wet and dry deposition and outputs via hydrologic export. Although denitrification has been shown to be important in many wetland ecosystems, emission of N oxides from forest soils is an important, and often overlooked, component of an ecosystem N budget. During 1 year (2002–03), emissions of nitric oxide (NO) and nitrous oxide (N2O) were measured from Sessile oak and Norway spruce forest soils in northeast Hungary. Accumulation in small static chambers followed by gas chromatography-mass spectrometry detection was used for the estimation of N2O emission flux. Because there are rapid chemical reactions of NO and ozone, small dynamic chambers were used for in situ NO flux measurements. Average soil emissions of NO were 1.2 and 2.1 μg N m−2 h−1, and for N2O were 15 and 20 μg N m−2 h−1, for spruce and oak soils, respectively. Due to the relatively high soil water content, and low C/N ratio in soil, denitrification processes dominate, resulting in an order of magnitude greater N2O emission rate compared to NO. The previously determined N balance between the atmosphere and the forest ecosystem was re-calculated using these soil emission figures. The total (dry+wet) atmospheric N-deposition to the soil was 1.42 and 1.59 g N m−2 yr−1 for spruce and oak, respectively, while the soil emissions are 0.14 and 0.20 g N m−2 yr−1. Thus, about 10–13% of N compounds deposited to the soil, mostly as and , were transformed in the soil and emitted back to the atmosphere, mostly as greenhouse gas (N2O). 相似文献
7.
V. Mugica E. Ortiz L. Molina A. De Vizcaya-Ruiz A. Nebot R. Quintana J. Aguilar E. Alcntara 《Atmospheric environment (Oxford, England : 1994)》2009,43(32):5068-5074
PM2.5 and PM10 were collected during 24-h sampling intervals from March 1st to 31st, 2006 during the MILAGRO campaign carried out in Mexico City's northern region, in order to determine their chemical composition, oxidative activity and the estimation of the source contributions during the sampling period by means of the chemical mass balance (CMB) receptor model. PM2.5 concentrations ranged from 32 to 70 μg m−3 while that of PM10 did so from 51 to 132 μg m−3. The most abundant chemical species for both PM fractions were: OC, EC, SO42−, NO3−, NH4+, Si, Fe and Ca. The majority of the PM mass was comprised of carbon, up to about 52% and 30% of the PM2.5 and PM10, respectively. PM2.5 constituted more than 50% of PM10. The redox activity, assessed by the dithiothreitol (DTT) assay, was greater for PM2.5 than for PM10, and did not display significant differences during the sampling period. The PM2.5 source reconciliation showed that in average, vehicle exhaust emissions were its most important source in an urban site with a 42% contribution, followed by re-suspended dust with 26%, secondary inorganic aerosols with 11%, and industrial emissions and food cooking with 10% each. These results had a good agreement with the Emission Inventory. In average, the greater mass concentration occurred during O3S that corresponds to a wind shift initially with transport to the South but moving back to the North. Taken together these results show that PM chemical composition, oxidative potential, and source contribution is influenced by the meteorological conditions. 相似文献
8.
Juan M. González Benítez J. Neil Cape Mathew R. Heal 《Atmospheric environment (Oxford, England : 1994)》2010,44(12):1506-1514
Simultaneous daily measurements of water-soluble organic nitrogen (WSON), ammonium and nitrate were made between July and November 2008 at a rural location in south-east Scotland, using a ‘Cofer’ nebulizing sampler for the gas phase and collection on an open-face PTFE membrane for the particle phase. Average concentrations of NH3 were 82 ± 17 nmol N m?3 (error is s.d. of triplicate samples), while oxidised N concentrations in the gas phase (from trapping NO2 and HNO3) were smaller, at 2.6 ± 2.2 nmol N m?3, and gas-phase WSON concentrations were 18 ± 11 nmol N m?3. The estimated collection efficiency of the nebulizing samplers for the gas phase was 88 (±8) % for NH3, 37 (±16) % for NO2 and 57 (±7) % for WSON; reported average concentrations have not been corrected for sampling efficiency. Concentrations in the particle phase were smaller, except for nitrate, at 21 ± 9, 10 ± 6 and 8 ± 9 nmol N m?3, respectively. The absence of correlation in either phase between WSON and either (NH3 + NH4+) or NO3? concentrations suggests atmospheric WSON has diverse sources. During wet days, concentrations of gas and particle-phase inorganic N were lower than on dry days, whereas the converse was true for WSON. These data represent the first reports of simultaneous measurements of gas and particle phase water-soluble nitrogen compounds in rural air on a daily basis, and show that WSON occurs in both phases, contributing 20–25% of the total water-soluble nitrogen in air, in good agreement with earlier data on the contribution of WSON to total dissolved N in rainfall in the UK. 相似文献
9.
Alan E. Fryar Stephen A. Macko William F. Mullican III Katherine D. Romanak Philip C. Bennett 《Journal of contaminant hydrology》2000,40(4)
In arid and semi-arid environments, artificial recharge or reuse of wastewater may be desirable for water conservation, but NO3− contamination of underlying aquifers can result. On the semi-arid Southern High Plains (USA), industrial wastewater, sewage, and feedlot runoff have been retained in dozens of playas, depressions that focus recharge to the regionally important High Plains (Ogallala) aquifer. Analyses of ground water, playa-basin core extracts, and soil gas in an 860-km2 area of Texas suggest that reduction during recharge limits NO3− loading to ground water. Tritium and Cl− concentrations in ground water corroborate prior findings of focused recharge through playas and ditches. Typical δ15N values in ground water (>12.5‰) and correlations between δ15N and ln CNO−3–N suggest denitrification, but O2 concentrations ≥3.24 mg l−1 indicate that NO3− reduction in ground water is unlikely. The presence of denitrifying and NO3−-respiring bacteria in cores, typical soil–gas δ15N values <0‰, and decreases in NO3−–N/Cl− and SO42−/Cl− ratios with depth in cores suggest that reduction occurs in the upper vadose zone beneath playas. Reduction may occur beneath flooded playas or within anaerobic microsites beneath dry playas. However, NO3−–N concentrations in ground water can still exceed drinking-water standards, as observed in the vicinity of one playa that received wastewater. Therefore, continued ground-water monitoring in the vicinity of other such basins is warranted. 相似文献
10.
Groundwater nitrification is a poorly characterized process affecting the speciation and transport of nitrogen. Cores from two sites in a plume of contamination were examined using culture-based and molecular techniques targeting nitrification processes. The first site, located beneath a sewage effluent infiltration bed, received treated effluent containing O2 (> 300 µM) and NH4+ (51–800 µM). The second site was 2.5 km down-gradient near the leading edge of the ammonium zone within the contaminant plume and featured vertical gradients of O2, NH4+, and NO3− (0–300, 0–500, and 100–200 µM with depth, respectively). Ammonia- and nitrite-oxidizers enumerated by the culture-based MPN method were low in abundance at both sites (1.8 to 350 g− 1 and 33 to 35,000 g− 1, respectively). Potential nitrifying activity measured in core material in the laboratory was also very low, requiring several weeks for products to accumulate. Molecular analysis of aquifer DNA (nested PCR followed by cloning and 16S rDNA sequencing) detected primarily sequences associated with the Nitrosospira genus throughout the cores at the down-gradient site and a smaller proportion from the Nitrosomonas genus in the deeper anoxic, NH4+ zone at the down-gradient site. Only a single Nitrosospira sequence was detected beneath the infiltration bed. Furthermore, the majority of Nitrosospira-associated sequences represent an unrecognized cluster. We conclude that an uncharacterized group associated with Nitrosospira dominate at the geochemically stable, down-gradient site, but found little evidence for Betaproteobacteria nitrifiers beneath the infiltration beds where geochemical conditions were more variable. 相似文献
11.
The role of nitrogen (N) in acidification of soil and water has become relatively more important as the deposition of sulphur has decreased. Starting in 1991, we have conducted a whole-catchment experiment with N addition at Gårdsjön, Sweden, to investigate the risk of N saturation. We have added 41 kg N ha−1 yr−1 as NH4NO3 to the ambient 9 kg N ha−1 yr−1 in fortnightly doses by means of sprinkling system. The fraction of input N lost to runoff has increased from 0% to 10%. Increased concentrations of NO3 in runoff partially offset the decreasing concentrations of SO4 and slowed ecosystem recovery from acid deposition. From 1990-2002, about 5% of the total N input went to runoff, 44% to biomass, and the remaining 51% to soil. The soil N pool increased by 5%. N deposition enhanced carbon (C) sequestration at a mean C/N ratio of 42-59 g g−1. 相似文献
12.
Chemical characteristics of precipitation at metropolitan Newark in the US East Coast 总被引:5,自引:0,他引:5
To investigate the chemical characteristics of precipitation in the polluted coastal atmosphere, a total of 46 event-based precipitation samples were collected using a wet-only automatic precipitation collector from September 2006 to October 2007 at metropolitan Newark, New Jersey in the US East Coast. Samples were analyzed by ion chromatography for the concentrations of major inorganic ions (Cl−, NO3−, SO42−, F−, NH4+, Ca2+, Mg2+, Na+, K+) and organic acid species (CH3COO−, HCOO−, CH2(COO)22−, C2O42−). Selected trace metals (Sb, Pb, Al, V, Fe, Cr, Co, Ni, Cu, Zn, Cd) in samples were determined by ICPMS. Mass concentration results show that SO42− was the most dominant anion accounting for 51% of the total anions, controlling the acidity of the precipitation. NH4+ accounted for 48.6% of the total cations, dominating the precipitation neutralization. CH3COO− and HCOO− were the two dominant water-soluble organic acid species, accounting for 42% and 40% of the total organic acids analyzed, respectively. Al, Zn and Fe were the three major trace metals in precipitation, accounting for 34%, 27%, and 25% of the total mass of metals analyzed. The pH values in precipitation ranged from 4.4 to 4.9, indicating an acidic nature. Enrichment Factor (EF) Analysis showed that Na+, Cl−, Mg2+ and K+ in the precipitation were primarily of marine origin, while most of the Fe, Co and Al were from crust sources. Pb, V, Cr, Ni were moderately enriched with EFs ranging 43–410, while Zn, Sb, Cu, Cd and F− were highly enriched with EFs > 700, indicating significant anthropogenic influences. Factor analysis suggests 6 major sources contributing to the observed composition of precipitation at this location: (1) nitrogen-enriched soil, (2) secondary pollution processes, (3) marine sources, (4) incinerations, (5) oil combustions, and (6) malonate–vanadium enriched sources. To further explore the source–precipitation event relationships and seasonality, cluster analysis was performed for all precipitation events. Results show that about half of the precipitation events were characterized by mixed sources. Significant influences of nitrogen-enriched soil and marine sources were associated with precipitation events in spring and autumn, while secondary pollution processes, incineration and oil combustion contributed greatly in summer. 相似文献
13.
Cecilia Arsene Romeo Iulian Olariu Nikolaos Mihalopoulos 《Atmospheric environment (Oxford, England : 1994)》2007,41(40):9452-9467
Chemical composition of rainwater was studied in the northeastern Romania, Iasi region, and the concentrations of major inorganic and organic ions were measured in samples collected between April 2003 and December 2006. The pH of the rainwater is 5.92 (volume weighted mean average, VWM) suggesting a sufficient load of alkaline components neutralizing its acidity. On average, 97% of the acidity in the collected samples is neutralized by CaCO3 and NH3. Clear seasonal variations were observed for some of the identified ions (e.g., SO42−, NO3−, Ca2+, NH4+). The data obtained during this work revealed that both concentrations and fluxes of anthropogenic source-related ions (e.g., SO42−, NO3− and NH4+) are among the highest reported for European sites. It is shown that meteorology and long-range transport processes may concur to their high levels. 相似文献
14.
Dry deposition of ammonia,nitric acid,ammonium, and nitrate to alpine tundra at Niwot Ridge,Colorado
《Atmospheric environment (Oxford, England : 1994)》2001,35(6):1105-1109
Micrometeorological measurements and ambient air samples, analyzed for concentrations of NH3, HNO3, NH4+, and NO3−, were collected at an alpine tundra site on Niwot Ridge, Colorado. The measured concentrations were extremely low and ranged between 5 and 70 ng N m−3. Dry deposition fluxes of these atmospheric species were calculated using the micrometeorological gradient method. The calculated mean flux for NH3 indicates a net deposition to the surface and indicates that NH3 contributed significantly to the total N deposition to the tundra during the August–September measurement period. Our pre-measurement estimate of the compensation point for NH3 in air above the tundra was 100–200 ng N m−3; thus, a net emission of NH3 was expected given the low ambient concentrations of NH3 observed. Based on our results, however, the NH3 compensation point at this alpine tundra site appears to have been at or below about 20 ng N m−3. Large deposition velocities (>2 cm s−1) were determined for nitrate and ammonium and may result from reactions with surface-derived aerosols. 相似文献
15.
C. Wagner G. Schuster J.N. Crowley 《Atmospheric environment (Oxford, England : 1994)》2009,43(32):5001-5008
The interaction of N2O5 with dispersed samples of Arizona Test Dust (ATD), Calcite (CaCO3) and quartz (SiO2) was investigated at varying relative humidity using an aerosol flow reactor. Reactive uptake coefficients, γ, obtained at close to zero relative humidity were (4.8 ± 0.7) × 10−3 for CaCO3, (8.6 ± 0.6) × 10−3 for Quartz and (9.8 ± 1.0) × 10−3 for ATD. In the case of calcite, evidence was obtained for an enhanced rate of uptake at relative humidities above ≈ 50%. The results are compared to literature values obtained using bulk substrates and to previous aerosol uptake data on Saharan dust. 相似文献
16.
Hydrochemistry of urban groundwater, Seoul, Korea: the impact of subway tunnels on groundwater quality 总被引:1,自引:0,他引:1
Chae GT Yun ST Choi BY Yu SY Jo HY Mayer B Kim YJ Lee JY 《Journal of contaminant hydrology》2008,101(1-4):42-52
Hydrogeologic and hydrochemical data for subway tunnel seepage waters in Seoul (Republic of Korea) were examined to understand the effect of underground tunnels on the degradation of urban groundwater. A very large quantity of groundwater (up to 63 million m3 year− 1) is discharged into subway tunnels with a total length of 287 km, resulting in a significant drop of the local groundwater table and the abandonment of groundwater wells. For the tunnel seepage water samples (n = 72) collected from 43 subway stations, at least one parameter among pathogenic microbes (total coliform, heterotrophic bacteria), dissolved Mn and Fe, NH4+, NO3−, turbidity, and color exceeded the Korean Drinking Water Standards. Locally, tunnel seepage water was enriched in dissolved Mn (avg. 0.70 mg L− 1, max. 5.58 mg L− 1), in addition to dissolved Fe, NH4+, and pathogenic microbes, likely due to significant inflow of sewage water from broken or leaking sewer pipes.Geochemical modeling of redox reactions was conducted to simulate the characteristic hydrochemistry of subway tunnel seepage. The results show that variations in the reducing conditions occur in urban groundwater, dependent upon the amount of organic matter-rich municipal sewage contaminating the aquifer. The organic matter facilitates the reduction and dissolution of Mn- and Fe-bearing solids in aquifers and/or tunnel construction materials, resulting in the successive increase of dissolved Mn and Fe. The present study clearly demonstrates that locally significant deterioration of urban groundwater is caused by a series of interlinked hydrogeologic and hydrochemical changes induced by underground tunnels. 相似文献
17.
Ju X Lu X Gao Z Chen X Su F Kogge M Römheld V Christie P Zhang F 《Environmental pollution (Barking, Essex : 1987)》2011,159(4):1007-1016
An automated system for continuous measurement of N2O fluxes on an hourly basis was employed to study N2O emissions in an intensively managed low carbon calcareous soil under sub-humid temperate monsoon conditions. N2O emissions occurred mainly within two weeks of application of NH4+-based fertilizer and total N2O emissions in wheat (average 0.35 or 0.21 kg N ha−1 season−1) and maize (average 1.47 or 0.49 kg N ha−1 season−1) under conventional and optimum N fertilization (300 and 50-122 kg N ha−1, respectively) were lower than previously reported from low frequency measurements. Results from closed static chamber showed that N2O was produced mainly from nitrification of NH4+-based fertilizer, with little denitrification occurring due to limited readily oxidizable carbon and low soil moisture despite consistently high soil nitrate-N concentrations. Significant reductions in N2O emissions can be achieved by optimizing fertilizer N rates, using nitrification inhibitors, or changing from NH4+- to NO3ˉ-based fertilizers. 相似文献
18.
Kiyoshi Matsumoto Hideki Minami Yukiko Uyama Mitsuo Uematsu 《Atmospheric environment (Oxford, England : 1994)》2009,43(28):4259-4265
In order to discuss the dry deposition fluxes of atmospheric fixed nitrogen species, observations of aerosol chemistry including nitrate (NO3?) and ammonium (NH4+) were conducted at two islands, Rishiri Island and Sado Island, over the Sea of Japan. Although the atmospheric concentrations of particulate NH4+–N showed higher values than those of particulate NO3?–N at both sites, the dry deposition fluxes of the particulate NO3?–N were estimated to be higher than those of the particulate NH4+–N. This was caused by the difference of particle sizes between the particulate NO3? and NH4+; NH4+ was almost totally contained in fine particles (d < 2.5 μm) with smaller deposition velocity, whereas NO3? was mainly contained in coarse particles (d > 2.5 μm) with greater deposition velocity. Fine mode NO3? was strongly associated with fine mode sea-salt and mineral particles, of which higher concentrations shifted the size of particulate NO3? toward the fine mode range. This size shift would decrease the dry deposition flux of the fixed nitrogen species on coastal waters and accelerate atmospheric transport of them to the remote oceanic areas. 相似文献
19.
Steen Solvang Jensen Tim Larson K.C. Deepti Joel D. Kaufman 《Atmospheric environment (Oxford, England : 1994)》2009,43(30):4544-4556
We evaluated the Danish AirGIS air quality and exposure model system using air quality measurement data from New York City in the Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air). Measurements were used from three US EPA Air Quality System (AQS) monitoring stations and a comprehensive MESA Air measurement campaign including about 150 different locations and about 650 samples of about 2 week measurements of NOx, NO2 and PM2.5. AirGIS is a deterministic exposure model system based on the dispersion models Operational Street Pollution Model (OSPM) and the Urban Background Model (UBM). The UBM model reproduced the annual levels within 1–26% depending on station and pollutant at the three urban background EPA monitor stations, and generally reproduced well the seasonal and diurnal variation. The full model with OSPM and UBM reproduced the MESA Air measurements with a correlation coefficient of r2 = 0.51 for NOx, r2 = 0.28 for NO2 and r2 = 0.73 for PM2.5. 相似文献
20.
Ricardo Cisneros Andrzej Bytnerowicz 《Environmental pollution (Barking, Essex : 1987)》2010,158(10):3261-3271
Two-week average concentrations of ozone (O3), nitric acid vapor (HNO3) and ammonia (NH3) were measured with passive samplers during the 2002 summer season across the central Sierra Nevada Mountains, California, along the San Joaquin River drainage. Elevated concentrations of the pollutants were determined with seasonal means for individual sites ranging between 62 and 88 ppb for O3, 1.0-3.8 μg m−3 for HNO3, and 2.6-5.2 μg m−3 for NH3. Calculated O3 exposure indices were very high, reaching SUM00-191 ppm h, SUM60-151 ppm h, and W126-124 ppm h. Calculated nitrogen (N) dry deposition ranged from 1.4 to 15 kg N ha−1 for maximum values, and 0.4-8 kg N ha−1 for minimum values; potentially exceeding Critical Loads (CL) for nutritional N. The U.S., California, and European 8 h O3 human health standards were exceeded during 104, 108, and 114 days respectively, indicating high risk to humans from ambient O3. 相似文献