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1.
Aerodynamically designed surrogate surfaces were used to determine the relative importance of gaseous (SO2, HNO3, NH3) and particulate species (SO4 2?, NO3 ?, NH4 +, Ca2+) in the dry deposition flux. For 11 sampling periods, we measured the deposition fluxes, ambient gaseous concentrations, size distributions of atmospheric aerosols and some meteorological parameters in Uji. The dry deposition of the gas to a nearly perfect sink was calculated by subtracting the greased surface flux from the total deposition flux to both the greased and reagent impregnated (or water) surface. It was found that the gas phase deposition contributed significantly more (60–93%) than the particulate phase to overall deposition of sulfur and nitrogen compounds. The dry deposition velocities of the species were also calculated using the deposition fluxes and the measured ambient concentrations. Comparisons were made between the measured and modeled particulate deposition flux.  相似文献   

2.
Atmospheric gases and particulates were collected using four-stage filter-pack in Chunchon from January through December in 1999. Particulate SO4 2? and NO3 ?, and gaseous HNO3, SO2 and NH3 were analyzed. Annual average concentration of SO4 2?(S), NO3 ?(S), HNO3 (g), SO2(g) and NH3(g) were 5.75µg/m3, 4.98µg/m3, 0.33ppb, 1.52ppb and 7.25ppb, respectively. Annual dry deposition fluxes were estimated using the measured concentration and dry deposition velocity published by other research group. Annual dry deposition of S was 287kg · (km)?2·y?1, which accounted for about 30% of total S deposition. For N deposition, dry deposition is predominant; about 70% of total N deposition was through dry process mostly as forms of NH3 and HNO3.  相似文献   

3.
The field measurement of dry deposition still represents a difficult task. In our approach, a 1 to 2 cm thick layer of water in a petri dish with a diameter of 22 cm, serves as a surrogate surface. The atmospheric constituents taken up by the water can be analyzed chemically by the same procedure as for the wet deposition samples. In contrast to solid surrogate surfaces, water exhibits the following advantageous properties: low and constant surface resistance, high sticking coefficient for aerosols, and predictable Sorption behavior for gases. Consequently, the deposition rates measured to the wet surface are generally higher, by up to a factor of 4 for NH4 +, Cl?, NO3 ? and SO4 2?, than those to a dry surface, but still smaller than the concurrent wet deposition rates. We observed the following average dry deposition rates in μmol m?2 d?1∶ NH4 + 48.3, Ca2+ 40.7, Na+ 15.8, Mg2+ 8.4, K+ 4.2, H-Aci 36.4; SO4 2? 57.2, Cl? 39.2, NO3 ? 34.5, HSO3 ? 5.7, formate 4.0; acid soluble metals: Fe 2.8, Zn 0.60, Cu 0.11, Pb 0.073, Cd 0.0022. The soluble fraction of Zn, Cd, Cu, Pb and Fe in the dry deposition varied with the pH of the water phase corresponding to the adsorption tendency of these metals to oxide surfaces. The sampling method also allows tracing of regionally and locally emitted atmospheric pollutants. In our study the local pollution sources included road salting, construction work and a refuse incinerator. Finally, chemical reactions occurring in the atmosphere, such as the conversion of Cl? to HCl by HNO3 or the oxidation of SO2, can be identified by evaluating the data. The method proposed is relevant to measure reproducibly the dry deposition of a variety of compounds to water bodies and moist vegetation.  相似文献   

4.
Dry deposition velocity estimates of SO, HNO3 and SO4 2? were computed for six locations in eastern North America using two different inferential models; a Big-Leaf model utilized by the U. S. National Dry Deposition Network (NDDN) and, a land-use based model (LUM) that has been used in the past to estimate the relative importance of dry versus wet deposition over selected Canadian regions. There were consistent differences between models that were related to the surface type, chemical species and time of year. Mean monthly dry deposition velocities based upon the 1990–91 time period were compared at two locations. The seasonal cycles in deposition velocity were similar between models, but there were considerable differences in the amplitude of the cycles. The LUM predicted about a 400% increase in S042- deposition velocity from the winter to the summer months, while there was a 50 to 100% increase in the NDDN model estimates, depending upon location. According to the LUM, HN03 deposition to crop land increased by about a factor of 6 from winter to summer, while the big leaf model predicted a 50% increase. Overall, there was better agreement for SO2. Averaged over 12 months, the differences in deposition velocity between models were smaller and generally within the range of uncertainty associated with inferential models. For all six sites, the mean percent difference between models in deposition velocity for SO2, HNO3 and SO4 2? were 13, 35 and 79, respectively. These differences highlight the effect of using different methods for estimating dry deposition and the importance of applying the same model when examining regional patterns in dry/total deposition rates.  相似文献   

5.
Inputs of wet and dry deposition were monitored at the Huntington Forest in the Adirondack Mountains of New York for two years in the open and beneath the canopy of a northern hardwood forest. In the open, ion flux estimates were similar using wet-only weekly (NADP protocol) and event collections, but bulk collections were higher for all ions except H+, which was much lower. These differences were due to the contribution of dry deposition and possible biotic alterations in bulk collectors. Dry deposition was estimated using air concentrations and ion-specific depositional velocities modeled with meteorological data, and contributed substantially to the input of all ions [H+ (45%), Na+ (24%), K+ (22%), NH4 + (12%), Ca2+ (58%), Mg2+(43%), NO3 ? (55%), Cl? (27%) and SO4 ?2 (26%)]. Dry input of base cations was dominated by coarse particles, whereas gaseous inputs were more important for S and NO3 ?. Atmospheric concentrations of SO2 and inputs of SO4 2? and H+ were lower at this site than sites closer to point sources of S gas emission. The importance of estimating atmospheric inputs was examined using examples of elemental budgets. For example, different estimates of the contribution of dry deposition of SO4 2? (9–21 meq m?2 y?1) resulted in conclusions ranging from no net retention to a net loss of this element. Such differences have important implications in assessing the current and future role of atmospheric inputs in affecting elemental cycling.  相似文献   

6.
Many ecosystems in Switzerland suffer from eutrophication due to increased atmospheric nitrogen (N) input. In order to get an overview of the problem, critical loads for nutrient N were mapped with a resolution of 1×1 km applying two methods recommended by the UN/ECE: the steady state mass balance method for productive forests, and the empirical method for semi-natural vegetation, such as natural forests, (sub-)alpine or species-rich grassland and raised bogs. The national forest inventory and a detailed atlas of vegetation types were used to identify the areas sensitive to N input. The total N input was calculated as the sum of NO3 ?, NH4 +, NH3, NO2 and HNO3 wet and dry deposition. Wet deposition was determined on the basis of a precipitation map and concentration measurements. Dry deposition was calculated with inferential methods including land-use specific deposition velocities. The concentration fields for NH3 and NO2 were obtained from emission inventories combined with dispersion models. Reduced N compounds account for 63% of total deposition in Switzerland. As indicated by exceeded critical loads, the highest risk for harmful effects of N deposition (decrease of ecosystem stability, species shift and losses) is expected on forests and raised bogs in the lowlands, where local emissions are intense. At high altitudes and in dry inner-alpine valleys, deposition rates are significantly lower.  相似文献   

7.
One-year field measurements were conducted in a Japanese cedar (Cryptomeria japonica) forest, located in Gunma Prefecture, Japan. On the basis of the meteorological and atmospheric concentration data, the dry deposition of SO2, HNO3, NO2 and HCl was estimated using the inferential method. The annual dry deposition of H+ was estimated at 721 eq ha?1yr?1, which was 40% larger than the measured annual wet deposition of H+ (514 eq ha?1yr?1). Therefore, dry deposition is an important pathway for the atmospheric input of H+ to the forest in the study site. The contribution of each gas to the dry deposition of H+ was as follows: SO2, 25%; HNO3, 32%; NO2, 10%; and HCl, 33%. The extremely high contribution of HCl appeared to be caused by the high emission intensity of HCl due to waste incineration in the site region. The differences between estimated deposition and throughfall and stemflow measurements indicated that about 80% of the total deposition of H+ was taken up by the canopy.  相似文献   

8.
In this paper estimates of dry and wet deposition of acidifying substances in the Netherlands are presented. The deposition was estimated from measured concentrations in the atmosphere and in precipitation or if these were not available, from modelled concentrations. The method was applied for the Netherlands on a 5×5 km scale. The most important components are sulphur oxides and ammonia and their reaction products. It was estimated that the annual average deposition of SO x in the Netherlands decreased from 1570 to 670 mol ha?1 a?1 between 1980 and 1989. In 1989, the annual average NO y deposition was estimated to be 1220 mol ha?1 a?1 in 1980 and 1160 mol ha?1 a?1 in 1989. The annual average NH x deposition in the Netherlands was estimated to be 2330 and 2190 mol ha?1 a?1 in 1980 and 1989 respectively. HCI deposition was about 100 mol ha?1 a?1 in all years. Dry deposition contributes most to the total deposition for each component. The spatial distribution of the total deposition shows a gradient over the Netherlands with highest values in the South and lowest in the North of the country. Meteorological conditions are also of influence on the deposition fluxes for all components. During 1988 and 1989 meteorological conditions favoured low deposition. The estimated uncertainty in the average fluxes of SO x , NO y , and NH x for the Netherlands is 15, 25, and 30% respectively. The wet deposition fluxes can be estimated more accurately than the dry deposition.  相似文献   

9.
The distribution of acidic andalkaline constituents (SO4 2-,NO3 -, Cl-, NH4 +, Na+,K+, Ca2+) between the fine and coarseparticle range has been examined in an urban locationin Thessaloniki, N. Greece over an 8-month period. The chemistry of wet and dry deposition collected overthe same period was also examined. Statisticalassociations between species within each environmentalphase were investigated using correlation analysis.Use of principal component analysis was made toinvestigate compositional similarities betweenaerosol, deposited dust and rain. It was found thatSO4 followed by NO3, NH4 and Caprevailed in fine aerosol. Sulphates and Ca were alsothe prevailing ions in the coarse particle fraction.Wet deposition was found to be the dominant depositionmechanism for all species. The high dry depositionrates observed for Ca and SO4 suggest that mostof the dry deposited sulphate is in the form ofCaSO4. Scavenging ratios of ionic speciesassociated with coarse aerosol were higher than thecorresponding ratios for fine particles. Principalcomponent analysis suggested that variations in ioniccomposition of fine aerosol could be interpretedprimarily by gas-to-particle neutralization reactionsinvolving atmospheric ammonia. In contrast, theinteraction between SO2 and HNO3 with Cacompounds seems to be the most likely factor that canexplain variations in wet and dry deposition ioniccontents.  相似文献   

10.
Abstract

The efficient use of N for crop production is important because N is normally the most expensive fertilizer input. Past research has suggested that Ca++ can be used to stimulate NH4+ absorption by plants. The importance of plant growth stage in relation to this phenomenon has not been examined previously. The objectives of this study were to examine Ca++ ‐ stimulated NH4 + absorption and to examine the effect of Ca++ concentration on N content and growth in plant tops, bulbs and roots at different growth stages. Ammonium absorption experiments were conducted in the greenhouse in 4‐L pots containing 3.5 kg of calcareous Gila sandy loam (Typic Torrifluvents) (CEC <1 cMol kg?1). Plants (Radish, Raphanus sativas L., and onion, Allium cepa L.) were grown with a uniform nutrient solution (1/2 strength nutrient solution, all N as NO3) to the desired growth stage at which time the soil was leached with deionized water. Afterwards, the soils were fertilized with 1/2 strength nutrient solutions (5 mol m?3 NH4) with Ca++: NH4 + molar ratios of 0, 0.25, 0.50, 1.00, and 2.00 for a period of 30 h. As Ca++ concentration increased, NH4 + absorption and plant growth increases were greatest with young seedlings. In the intermediate and mature growth stages, Ca++ stimulated 15NH4 + absorption was less rapid than in the earlier growth stages but frequently exhibited a different response (i.e., altered metabolite translocation) to the added Ca++ ‐ concentration. However, at the intermediate and mature growth stages significantly increased N contents and plant growth also were noted in most cases. The Ca++ ‐ increased N content in leaves and bulbs of the older plants had much less 15N suggesting that the newly absorbed 15NH4 + was being deposited in the roots replacing older N forms that were then translocated to the bulbs or leaves. Thus, increasing Ca++ appeared to have anadditional function of increasing the mobility of metabolites (dry matter) from the roots. Since more above‐ground plant products were produced with the same amount of N, plant N use efficiency was increased.  相似文献   

11.
In order to estimate dry deposition, deposition velocity calculation and concentration measurement were carried out in Niigata, Japan. Deposition velocities of SO2 and HNO3 for some surfaces such as coniferous forest, deciduous forest, agricultural land, and water were calculated taking into account diurnal variations of meteorological elements using routine meteorological data. Deposition velocities of fine and coarse aerosols were also estimated respectively. Concentrations of SO2, HNO3, sulfate and nitrate in fine and coarse aerosols respectively were measured from July to December in 1998 using filter pack and denuder methods. The results indicate that HNO3 dry deposition for the high aerodynamic roughness surfaces such as forests is quite large. It is suggested that sulfate and nitrate aerosols depositions as well as the gases depositions should be taken into account to estimate dry deposition of sulfur and nitrogen compounds. It is also indicated that dry depositions of sulfur and nitrogen compounds are unable to ignore compared with their wet depositions.  相似文献   

12.
A preliminary analysis of O3, SO2, SO inf4 sup2? , and total NO inf3 sup? deposition to the red spruce forest on the summit of Whitetop Mountain, Virginia, illustrates uncertainties in analysis methodologies, establishes the relative importance of three deposition pathways, and suggests areas for further research. Results are presented here for an analysis of the dry, wet (precipitation), and cloud water deposition pathways for the four chemical species during a 26-day period in April and May 1986. Dry and cloud water depositions are estimated using available models along with air and cloud water chemistry measurements made at the summit. For water soluble species, depositions by precipitation and cloud interception are found to be comparable in magnitude, while dry deposition appears to be about an order of magnitude less. High levels of atmospheric O3 lead to a large estimate of 03 deposition (on a mass flux basis) when compared to the estimated deposition of gaseous SO2. This is in spite of the fact that computed SO2 dry deposition velocities exceed those for O3. Model uncertainties are large for both dry deposition velocity and cloud water flux computations, and some bias in computations probably exists because of the application of the models to a complex terrain situation. Field evaluation of the cloud water deposition model is of greatest priority because of the apparent relative importance of that deposition pathway.  相似文献   

13.
We estimated the total inorganic fluxes of nitrogen (N), sulfur (S), chloride (Cl?, sodium (Na+, calcium (Ca2+, magnesium (Mg2+, potassium (K+ and hydronium (H+. The resistance deposition algorithm that is programmed as part of the CALMET/CALPUFF modeling system was used to generate spatially-distributed deposition velocities, which were then combined with measurements of urban and rural concentrations of gas and particle species to obtain dry deposition rates. Wet deposition rates for each species were determined from rainfall concentrations and amounts available from the National Acid Deposition Program (NADP) monitoring network databases. The estimated total inorganic nitrogen deposition to the Tampa Bay watershed (excluding Tampa Bay) was 17 kg-N ha?1 yr?1 or 9,700 metric tons yr?1, and the ratio of dry to wet deposition rates was ～2.3 for inorganic nitrogen. The largest contributors to the total N flux were ammonia (NH3 and nitrogen oxides (NO x at 4.6 kg-N ha?1 yr?1 and 5.1 kg-N ha?1 yr?1, respectively. Averaged wet deposition rates were 2.3 and 2.7 kg-N ha?1 yr?1 for NH4 + and NO3 ?, respectively.  相似文献   

14.
In a laboratory study, KCI- a neutral salt - equivalent to 300kg K/ha and 272 kg CI/ha was applied to the surface of undisturbed columns of a forest soil (Terra Fusca Rendzina) under steady state unsaturated flow conditions (1.0 cm/day). The effluent of the five soil columns was collected daily, and pH, cation- and anion concentrations were measured. Most of the applied K ions were retained in the top 10cm of the soil and moved in decreasing amounts further down the column. Among the cations studied Ca++, Mg++, and Na+ were lost from the system, K+, NH4, Fe+++, Mn++, H+, and Al+++ were retained. Nitrate and sulfate concentrations in the leachates showed a temporary decrease when CI passed through the columns. This decrease was accompanied with a decrease in pH. CI?, NO3?, and SO4? exhibited leaching losses. Besides these anions, HCO3? played an important role.  相似文献   

15.
In order to obtain information on dry deposition of SO2 onto loess in China, the effects of water vapor and NO2 on SO2 deposition-oxidation processes were investigated in laboratory measurements. The deposition velocities of SO2 onto loess particles were 2.34–7.33 cm s?1, were high in comparison with the other studies. Deposition of SO2 onto the particles was decreased with exposed time and amounts of SO2, but was influenced by adsorption of water vapor onto the particles. On the other hand, oxidation of SO2 physically8 adsorbed was promoted by the coexistence of water vapor and NO2. So, it was indicated that it was possible for water vapor and NO2 in the atmosphere to play an important role in dry deposition for the deposition-oxidation interaction between SO2 and loess particles.  相似文献   

16.
From data on 30 headwater lakes in north-central Ontario we found that, during the spring snow melt of 1981, all lakes underwent serious declines in alkalinity. Generally, SO4 2?, alkalinity, Ca+ and Mg2+ concentrations were reduced by runoff and rain then recovered to intermediate levels after the major inputs declined. As expected, a range in responses was evident with lower alkalinity systems showing the greatest changes. The observed changes, however, were consistent with acid loading having depleted alkalinity. In calculating an input-output budget for each lake, we found that changes in Cl?, Na+, and K+ were consistent with atmospheric inputs being the major source as the difference between the expected input and the actual contribution from rain and snow had a mean near zero. There appears to be a significant, ? 45%, watershed source of sulphate that we hypothesize is from dry deposition occurring prior to snowfall and is eluted with the melting process. With refinements to a mass balance approach explaining the watershed source of SO4 2? and Al, we feel it is possible to predict springtime lake changes given a few chemical and simple morphometric variables.  相似文献   

17.
Weathering of piled material in the field is a popular method to treat spent mushroom substrate (SMS) before reuse. During the weathering process, rainfall and snowmelt pass through SMS piles and a large amount of solutes is released in the leachate. To investigate solute release patterns, the field weathering process was simulated under controlled conditions in the laboratory. Fresh SMS was packed in an acrylic column (20 cm i.d.) to 150 cm height and leached intermittently with a cumulative total of 230 cm of deionized water over 180 days. Leachate was collected and analyzed for dissolved organic carbon (DOC), dissolved organic nitrogen (DON), electrical conductivity (EC), and inorganic salts. Solute release patterns were described using first order models, and total released solutes were calculated. The SMS leachate had DOC, DON and EC values ranging from 450 to 15,500 mg L?1, 50 to 1,700 mg L?1, and 3 to 50 dS m?1, respectively. The major inorganic cations were K+, Na+, Ca2+, Mg2+ and NH4+, and anions were Cl? and SO42?. Release of DOC, DON, and bivalent cations Ca2+ and Mg2+ were described by a first order Exponential Rise to Maximum model, while releases of monovalent ions Cl?, K+, Na+ and NH4+ were described as a first order Sigmoidal Logistic process, and SO42? release was best modeled by a Sigmoidal Chapman equation. Following six months and 230 cm applied water, 3.1 kg of DOC, 0.58 kg of dissolved N, and 8.6 kg of inorganic salts were leached per cubic meter of bulk SMS (220 kg oven dry mass). Weathering of SMS involves a significant removal of nutrients from the composted material, which can contribute to pollution of soil and groundwater.  相似文献   

18.
Data collected during 1986 at seven widely separated sites in the eastern United States were used to estimate weekly averages of deposition velocities for SO2, O3, HNO3, and SO inf4 sup2? with both a modified version of the RADM dry deposition module and a site-specific inferential technique developed by the Atmospheric Turbulence and Diffusion Division of the National Oceanic and Atmospheric Administration's Air Resources Laboratory. The results show some systematic differences between the two techniques, even when the module uses distributions of landuse types that match as closely as possible the observed vegetation coverages used in the inferential technique. When one ignores the systematic differences that easily could be removed by minor changes in the algorithms for computing resistances to deposition, weekly averages of the deposition velocities calculated with the two methods are within approximately ±30% of each other for SO2 and O3. Overall, the relative differences in the deposition velocities for HNO3 and SO inf4 sup2? are about ±30 and ±50%, respectively. Use of the module with landuse types extrapolated to areas as large as RADM grid cells (approximately 80 km square) around the measurement stations produces weekly averages within ±20% of the site-specific estimates for SO2, O3, and SO inf4 sup2? and approximately ±30% for HNO3 if one avoids landuse types such as urban and water areas that are both nonrepresentative and have very different characteristics from the measurement sites. These estimates are not complete measures of the true uncertainty associated with the two techniques because they do not account for such effects as differences in the siting of instrumentation for collecting input data and the inability of the computational algorithms to include the many surface nonuniformities that typically exist in the areas surrounding measurement sites.  相似文献   

19.
As part of a study of the substance budgets of lakes in south-central Ontario, a network of precipitation collectors (8 bulk, 7 wet only) was operated to measure the deposition of nutrients and major ions. Results are reported for total P, total Kjeldahl N, NO 3 ? ?N, NH 4 + ?N, total N, Fe, H+, Ca++, Mg++, Na+, K+, SO 4 = and CL? for a two year period (August 1976–July 1978). On an equivalent basis the dominant anion in both bulk and wet precipitation was SO 4 = , with H+ the dominant cation. Precipitation in the study area is more acidic than that analyzed at any other location on the Canadian Shield to date. Concentrations of ions varied by 1 to 3 orders of magnitude between individual precipitation events and annual deposition varied by as much as 2-fold in the two years of study. Annual wet deposition contributed >60% of bulk deposition for all substances except total P. Seasonal trends in deposition with summer maxima were noted for most ions. For Harp Lake, a small Precambrian Lake with a lake area of 12.6% of its total drainage area, precipitation input directly to the lake surface was an important source of nutrients and major ions. This was especially the case for P, N and H+ because these substances were retained by the terrestrial drainage basin.  相似文献   

20.
A comprehensive acid-deposition measuring station has been set up at the General Motors Technical Center site in Warren, Michigan. A second station is also being operated at a rural site near Lapeer, Michigan, which is approximately 54 km north of the Warren site. This report presents the results of this study for the June-September 1981 period. The rain composition was similar at both sites with the pH averaging 4.1 and the SO4 =/NO3 ? equivalence ratio averaging 2.1:1. This similarity suggests that local sources, i.e., relatively high emissions near the Warren site, and low emissions near the Lapeer site, have little effect on rain composition. The SO4 =/NO3 ? ratio for individual rain events in Warren reflected the SO2/NOx emission ratio in the area from which the event had come. Thus, the highest SO4 =/NO3 ? ratios were observed for rains that arrived from the southeast and the lowest ratios for rains from the southwest. No rain events arrived from a northwesterly direction during this sampling period. Measurements were carried out at both sites to estimate the relative contribution of dry deposition. The ambient particulate was acidic about half the time and basic half the time. The acidity in the particulate was due to acid SO4 = and the basicity was due to soil-related materials. Gaseous HNO3 averaged 2.0 μg m?3while the basic gas, NH3, averaged 0.83 μg m?3. Based on these measurements, it was estimated that dry deposition of particles and HNO3 contributed less than 10% of the total deposition of acidity during this study period.  相似文献   

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