Deposition Of SO2 Research Articles

Dry deposition of airborne sulfate and nitrate to soybeans

Dry deposition contributes a substantial part of the total deposition of acidic pollutants and acid precursors to agricultural systems. However, because of the relative intractability of measurement of dry deposition fluxes, little work has been done to directly quantify dry inputs of pollutants to crops. In this research, foliar surface sampling (‘leaf-washing’) methods were developed and shown to be a practical and fairly precise means of monitoring the accumulation of dry-deposited SO 4 2− and NO 3 − on plant surfaces. Leaching of these ions from plant tissues was shown to be negligible; however, uptake by plants (e.g. stomatal gas exchange of SO 2 or HNO 3 and/or assimilation of surface accumulations of materials) is not accounted for by the sampling method. The significance of dry deposition to modification of the chemical microenvironment of leaf surfaces appears to be a factor of 3 to 20 or more greater than that of wet deposition alone. This is due to the cyclic reactivation of accumulated materials by dew and light rains, which may dissolve and mobilize, but not remove, the pollutant surface deposit. Therefore, while dry deposition of SO 2 and SO 4 2− containing particles may contribute only part of the total mass of sulfur inputs to crop systems, the exposure of plant surface tissue to pollutants can be dominated by the dry-deposited material. The alteration of leaf surface chemistry may contribute to possible stress-producing mechanisms such as reduction of cuticular integrity, cellular injury and death, enhanced leaching of primary and secondary metabolites, and changes in pathogen infection efficiency.

Dry deposition of O 3, SO 2, and HNO 3 to different vegetation in the same exposure environment

Agricultural meteorological modeling techniques are used to investigate the relative and absolute dry deposition fluxes of SO 2 (as sulfur), HNO 3 (as nitrogen) and O 3 to large fields of maize, soybeans, and alfalfa exposed in conditions as measured in northern Illinois, central Pennsylvania, and eastern Tennessee. For HNO 3, the differences in seasonal deposition rates among the three types of plant species are small. Within the same environment, the soybean canopy has the potential to receive substantially more gaseous dry deposition of SO 2 and O 3 than the maize and alfalfa (which are about the same), as a result of lower stomatal resistance and consequently higher deposition velocities. Deposition differences among the sites are small except for the case of SO 2, for which deposition rates estimated for northern Illinois are nearly double those at the other locations. The high SO 2 deposition at the northern Illinois location is a consequence of the higher air concentrations observed there.

Episodes of high SO 2 concentration in The Netherlands

In episodes of high daily mean SO 2 concentrations in the atmosphere there is a very extensive concentration field over The Netherlands caused by influx from both the Ruhr area and Central Europe. The meteorological conditions for such episodes range from very stable to stable with a boundary layer height between 100 and 450 m, wind speed at 200 m between 0 and 18 m s −1 and at 20 m between 0 and 9 m s −1. The last figures indicate that transport, as well as transport combined with stagnation, causes the high concentrations. The episodes nearly all occur in December, January and February, with easterly winds. In two thirds of the cases a local snow cover is present. This cover is more extensive in the east, so probably in all cases there is reduced dry deposition of SO 2. The turbulence is very low with hardly any vertical dispersion at higher altitudes, except around noon. In consequence of the wind direction variations over a day and the wind direction shear, the daily horizontal dispersion is normal or larger than normal. Therefore the contribution of a local high point source in The Netherlands to the ground level concentration will be small during air pollution episodes in winter.

Acid dew and the role of chemistry in the dry deposition of reactive gases to wetted surfaces

Using the resistance model for mass transfer, a formulation is derived for the dry deposition rate of a reactive, soluble gas depositing on a wetted, vegetative surface. The deposition velocity is expressed in terms of a dynamical resistance, which is a function of the physical state of the atmosphere, and a surface resistance, which is a function of the chemical and physical properties of the surface. This formulation is then used in a model to simulate the generation of acidic dew from the dry deposition of HNO3 and SO2, as well as the SIV oxidants, H2O2 and O3. Dewdrop pHs of about 4 are calculated by the end of the night, however these pHs can rapidly fall to potentially toxic levels soon after sunrise as the dewdrops evaporate. The deposition velocities to the dew for highly soluble species such as HNO3 and H2O2 are found to be entirely determined by the dynamical resistance; for the conditions adopted here a value of 0.4 cm s−1 is calculated for these species. However, much smaller deposition velocities are predicted for SO2 and O3 because of their lower solubilities and hence larger surface resistances. In the case of SO2, a nocturnally averaged deposition velocity of only about 0.03 cm s−1 is calculated for the standard model. Because the chemical lifetime of SO2 in the dew is influenced by the atmospheric levels of H2O2, O3, and SO2, the SO2 deposition velocity is found to be a strong function of these species' atmospheric abundances. These results imply that the deposition velocities of species such as SO2 to wetted surfaces may be influenced by the chemical as well as the physical state of the atmosphere; the assumption typically adopted that dry deposition velocities are independent of the species' atmospheric abundance may not always be appropriate.

The sensitivity of modeled SO2 fluxes and profiles to stomatal and boundary layer resistances

A higher-order closure model for canopy/surface exchange is presented and applied to an oak-hickory forest to model SO2 deposition for typical summertime conditions. The model is then used as a tool to investigate the sensitivity of modeled fluxes (the deposition velocity) and concentration profiles to the parameters used to compute the leaf boundary layer and stomatal resistances. Both the deposition velocity and concentration profiles show little sensitivity to variations in the leaf boundary-layer resistance (r b) since it generally comprises only a small fraction of the total resistance to diffusion from the air to the sub-stomatal cavity. The deposition velocity (V d ) is more sensitive to variations in the minimum stomatal resistance (r s ,min) and light response coefficient (β) than r b .It was found that 50% variations in β give a maximum difference of 0.2 cm s−1 in V d while 30% variations in r s , min produce a maximum difference of near 0.3 cm s−1.

A theoretical assessment of pollutant deposition to individual land types during a regional-scale acid deposition episode

A mesoscale model of pollutant transport, transformation and deposition was used to perform a detailed analysis of acidic deposition to the states of New York and Ohio during a 3-day springtime deposition episode. This model can be used to assess the roles of wet and dry deposition to individual land types in the removal of pollutants from the atmosphere. Over two-thirds (67 %, Ohio; 78 %, New York) of the acidic deposition during this rainy period fell as wet deposition, primarily in the form of H 2SO 4. Dry deposition of SO 2 accounted for 70–75 % of the total dry acidic deposition in both areas, and most of the remaining dry deposition occurred as HNO 3. Over both deposition areas, particulate sulfate deposition accounted for <1 % of the total acid deposition. Due to the highly surface-specific nature of the dry deposition process, individual land types displayed unique patterns of pollutant uptake. Water surfaces absorbed primarily SO 2, while rougher forested areas absorbed a larger proportion of HNO 3 vapor. Urban areas, with their associated material surfaces, were found to absorb significantly less acid in the dry form, and during dry periods most of this deposition may occur as HNO 3 vapor, although considerable uncertainty exists regarding the treatment of rainfall-wetted surfaces. These model results suggest that dry pollutant fluxes to individual surface types will show significant variability from any ‘averaged’ flux estimates over larger areas encompassing numerous land types.

Acidification of Nova Scotia Lakes

Although water chemistry of precipitation and lakes in Nova Scotia is dominated by C1 from sea salt, correction for marine influence reveals that the dominant anion in acidified lakes is SO4. Atmospheric deposition of non-marine SO4 (SO4) and NO3- for the period 1977–1980 at 4 stations in southwest Nova Scotia averaged 47 meq SO4* m−2 yr−1 and 21 meq NI3-m−2 yr−1 compared with 38 and 13 meq, respectively, for the average of 3 stations in the northeastern third of the province. Precipitation pH increased from 4.5 to 4.8 along the same axis. Almost 50% of the SO4 deposition occurred when storms came from the southwest, indicating low pressure tracks which pass south of major Canadian sources of S.

A comparison of estimated and measured SO2 deposition velocities

A nested-network program for obtaining data on the dry deposition of SO2 and SO4− has been initiated at a small array of locations (6 in 1985, presently 13) across North America. The procedures involved rely on the availability of models for deriving dry deposition rates from observations of air concentrations and of meteorological and surface properties known to influence the deposition velocity. At a subset of locations (i.e., 3), the results obtained by this indirect method are tested by comparison against more direct methods. One of the first comparison experiments of this series was conducted at Oak Ridge in July 1985 when the fluxes determined by inferential methods were compared to those measured by eddy correlation. The results obtained suggest that initial computer routines, developed to estimate deposition velocity for SOz on a routine basis, overestimate the deposition velocity by about 20% to a mixed-species deciduous forest. The difference is possibly due to the omission of water stress as a contributing factor in the initial computer routines, but might also be associated with chemical processes at the substomatal level.

A Comparative Study on the Effects of H2S and SO2Fumigation on the Growth and Accumulation of Sulphate and Sulphydryl Compounds inTrifolium pratenseL.,Glycine maxMerr. andPhaseolus vulgarisL.

Maas, F. M., De Kok, L. J., Peters, J. L. and Kuiper, P. J. C. 1987. A comparative study on the effects of H2S and SO2 fumigation on the growth and accumulation of sulphate and sulphydryl compounds in Trifolium pratense L., Glycine max Merr. and Phaseolus vulgaris L.—J. exp. Bot. 38: 1459-1469. The effects of 0—25 mm3 dm⊟3 H2S and SO2 on growth and sulphur content of shoots of Trifolium pratense, Glycine max and Phaseolus vulgaris were studied. After 2 weeks of fumigation the yield of T. pralense was reduced by 32% by H2S, but not affected by SO2. Yield of G. max was not affected by H2S, but reduced by 20% by SO2, whereas that of P. vulgaris was increased by 11% by H2S and not affected by SO2. Increases in sulphydryl content were already observed after 24 h of exposure to H2S and SO2 in all plants. The increase was greatest in T. pratense and smallest in P. vulgaris and, except for T. pratense, always greater in the H2S-exposed than the SO2-exposed plants. One day of exposure resulted in an increase in sulphate content only in the SO2-fumigated plants, with the highest accumulation in T. pratense and the lowest in P. vulgaris. After 2 weeks an increase in sulphate content was also observed in the H2S-exposed plants. This increase was also highest in T. pratense and lowest in P. vulgaris. Transpiration rate was not affected by a 24 h exposure to H2S or SO2 and was highest in T. pratense, intermediate in G. max and lowest in P. vulgaris. The order of theoretical rates of deposition of H2S and SO2 correlated with the observed increases in sulphydryl content during the first 24 h of exposure in both H2S and SO2-fumigated plants and with the increase in sulphate content in the SO2-exposed plants. The increases in sulphydryl content were only ≤ 8% of the theoretical H2S and SO2-deposition fluxes, whereas sulphate accumulation accounted for at least 57% of the theoretical SO2-deposition flux.

The geographical distribution and temporal variations of acidic deposition in Eastern North America

Data from two national precipitation chemistry monitoring networks, and several regional air and precipitation chemistry networks are used to describe some broad-scale features of acidic deposition in eastern North America. In northeastern North America, the coefficient of variation is shown to increase from 10–16% for annual averages to nearly 100% for daily values. There is a strong annual cycle in H+ SO 4 = and NH 4 + deposition and some of the other ions although these cycles are not all in phase. The wet NO 3 - deposition contributes relatively more than SO4 to the acidity of snow as compared to rain. Wet deposition is highly “episodic” with about 50% to 70% of the total annual deposition of SO 4 = and NO 3 - accumulating in the highest 20% of the days. Estimates made in various ways indicate that, over eastern North America as a whole, dry deposition is approximately equal to wet for both SO4 and NO3. Dry may exceed wet in the high emissions zone but drops to about 20% of the total deposition in more remote areas. Deposition via fog or low cloud impaction is an important input to high elevation forests, but more data are required to quantify the magnitude and regional extent of this.

Regional chemical characteristics of lakes in North America: Part I ? Eastern Canada

Data defining the major ion chemistry of lakes located in eastern Canada have been compiled for the purpose of evaluating the current status of surface water quality in relation to acidic deposition. A companion paper for lakes in the eastern United States (i.e. Part II, Linthurst et al., 1986) has been prepared also. Data sources in Canada included the National Inventory Survey, the Ontario Lake Sensitivity data set, and the National Aquatic Data base which provided an overall data base of approximately 5700 lakes. Only recently collected data (largely 1980 or later) were used in the analysis. Frequency distribution statistics were obtained for pH, acid neutralizing capacity (ANC), SO4 and organic anion (A−) concentrations. Acidic and low ANC waters in eastern Canada occur in a pattern explained by a combination of biogeochemical factors and atmospheric deposition. Nova Scotia contained the highest proportion of acidic and ultralow ANC lakes of any region surveyed in eastern North America; since this region receives approximately 20 kg.ha−1.yr−1 wet SO4 deposition, the proposed target loading may be too high to protect the highly sensitive waters of Maritime Canada. Compared to the rest of eastern Canada, lakes in Ontario have relatively high ANCs due to the influence of CaCO3 contained in the glacial till of the area. Variation in the SO4 concentration of lakes approximately follows expected gradients in wet SO4 deposition. Naturally occurring organic acids do not play a dominating role in the acidification of eastern Canadian lakes.

Weathering rates of gneiss and depletion of exchangeable cations in soils under environmental acidification

Budgets of Na, K, Mg, Ca, Al and Si in two forested basins in central Europe indicate that the weathering rate of gneiss and the depletion of exchangeable calcium and magnesium are increased due to acidification caused by high deposition of SO 2 . The production of the pool of exchangeable cations is slower than its depletion. There is a coincidence of a very short time necessary to deplete the topsoil of the exchangeable Ca 2+ and Mg 2+ and the die-back of spruce. These conclusions are derived from a new mass-balance approach that enables a separation of hydrolysis of primary minerals, depletion of exchangeable ions and production of the exchangeable pool of cations in soils from data on elemental budgets in small hydrological basins.

Sources and Sinks of Ions in a Soft Water, Acidic Lake in Florida

Fluxes and storage of water and major ions were measured for McCloud Lake, a small, acidic soft water lake in north central Florida that receives 90% of its water input from direct precipitation. Wet precipitation had a volume‐weighted pH of 4.5 and accounted for a H+ flux of 420 eq/ha yr; deposition of SO2, NO2, and HNO3 contributed an additional 150–300 eq H+/ha yr. Although precipitation passing through the sandy soils and littoral sediment was neutralized by mineral weathering, sulfate reduction or adsorption, and nitrate immobilization, ground water was only 10% of the total water input to the lake and neutralized only about 30% of precipitation H+ input. Compared to atmospheric deposition, lake water shows little enrichment of cations but is depleted in SO42−, NO3− and NH4+, while &gt;80% of precipitation H+ is neutralized. The major H+ neutralization processes within the lake are sulfate reduction (26–34 meq SO42−/m2 yr) and NO3− immobilization (17–20 meq NO3−/m2 yr), while NH4+ immobilization is a small internal source of H + . Sinks and sources of cations could not reliably be calculated because of uncertainties in groundwater inputs. Internal H+‐consuming processes are important in lakes with no surface inlets or outlets and which receive most of their water from direct precipitation. For these lakes, the rate and extent of acidification is largely determined by a balance between H+ inputs and H+ consumption by internal processes.

Atmospheric ammonium sulphate deposition and its role in the acidification and nitrogen enrichment of poorly buffered aquatic systems

The atmospheric transport of NH3, emitted from breeding farms and strongly manured cropland, causes a severe loading of neighboring non-agricultural environments. Particularly the wet deposition of ammonium sulphate is enhanced, while the pH of rainwater is only slightly acidic. Due to the variation of gaseous air pollutants over the Netherlands large differences are noticed in the relative contribution of each acidifying component in rainwater. In areas with high atmospheric NH3 concentrations, ammonium sulphate contributes the major part to the potential acidifying influence of wet deposition. Preliminary experiments show a causal relation between ammonium sulphate and water acidification, ammonium enrichment and the expansion of ammonium tolerant shore macrophytes. For the Dutch situation it is clear that, particularly in areas with enhanced atmospheric NH3 concentrations, the deposition of NH3 and SO2 derived compounds has provided the major contribution to acidification and N-enrichment of hydrologically isolated, poorly buffered pools. In all countries, particularly in areas with high NH3 emission, it will be useful to pay more attention to the environmental impact of airborne ammonium sulphate deposition.

Recovery of previously acidified lakes near Coniston, Canada following reductions in atmospheric sulphur and metal emissions

The purpose of the present study was to assess the rate of recovery of acidified lakes located near the town of Coniston following an abrupt reduction in atmospheric SO2 and metal emissions at the Coniston smelter which closed in 1972. The water chemistry of several lakes was studied over a period of 16 yr (1968–1984). In one extremely acidic lake close to the smelter, the pH increased from 4.05 in 1972 to 5.8 in 1984. Conductivity, as well as concentrations of SO4, Cu, Ni, Co, Mn, and Zn decreased by 60% to 90% in the lake water during the same period. In another initially less acidic lake nearby, the increase in pH was less dramatic, while the decrease in conductivity, SO4, and some metals was similar to that of the more acidic lake. Local SO4 deposition decreased approximately 75 % while Cu and Ni deposition decreased by 90% following closure of the Coniston smelter.

Laboratory investigations of the impact of dry deposition of SO 2 and wet deposition of acidic species on the atmospheric corrosion of galvanized steel

A series of short-term laboratory experiments were conducted in which galvanized steel samples were exposed to sub-ppm levels of SO 2. Dew was produced periodically on the test panels, and, at the end of some experiments, panels were sprayed with solutions of various pH levels. Both dew and rain rinse samples were analyzed for SO 3 2−, SO 4 2− and Zn. The laboratory results suggest that as a first approximation the damage to galvanized steel induced by the dry deposition of SO 2 can be calculated by equating the dry SO 2 flux to the Zn corrosion flux. SO 2 will deposit onto a fresh dry surface until an amount similar to that of a monolayer has formed. Under wet conditions, the dry deposition flux is controlled by the gas-phase resistance of the atmosphere. Wet deposition of ammonium bisulphate induces corrosion which depends not only on the pH of the incident rain, but also on the exposure history of the samples.

SO 2, sulfate and HNO 3 deposition velocities computed using regional landuse and meteorological data

Deposition velocity fields were generated for SO 2, sulfate and HNO 3 over eastern United States and southeastern Canada by combining detailed landuse data with meteorological information predicted using a mesoscale meteorology model. When there is significant variation in land type within an averaging area, it was found that subgrid scale meteorological variations can significantly influence area-averaged deposition velocities. The assumption that uu is constant over the averaging area can realistically address the subgrid variations in wind speed and friction velocity. For a 3-day springtime simulation, domain-averaged mid-day SO 2, sulfate and HNO 3 deposition velocities at a height of approximately 40 m were found to be 0.8 cm s −1, 0.2 cm s −1, and 2.5 cm s −1, respectively. At night, the deposition velocities were approximately 50%, 45% and 70% of the corresponding daytime values for SO 2, sulfate and HNO 3. Using a simple parameterization to account for rainfall-wetted surfaces increased domain-averaged SO 2 deposition velocities by up to a factor of two, indicating that precipitation can significantly enhance dry deposition of SO 2.

Effect of meteorologic and atmospheric health factors on acute diseases of the respiratory tract in children--as exemplified by the Biel region

In the region of the small town of Biel, cases of various acute respiratory illnesses among children were recorded and correlated with measured parameters of meteorology and air pollution (sulfur dioxide, dust) during a period of one and a half years. An increase of cases was noted during the fall and winter months, by low temperatures, high humidity and meteorological conditions with northerly synoptic winds. Also the correlation of the cases to SO2 deposition values revealed a significant connection that may possibly be simulated by identical seasonal changes. No significant connection could be found between concentrations of SO2 respectively dust values and frequency of illness.

Acid precipitation and soil solution chemistry within a maple-birch forest in Canada

Ion concentrations in water collected within a hardwood forest at Turkey Lakes Watershed, Ont. (Lat. 47° 03′N, Long. 84° 15′W) were examined in relation to those in precipitation at the watershed and at other places in eastern Canada. The mean annual concentration of Ca 2+, Mg 2+, K +, Na +, H +, NH 4 +, NO 3 −, SO 4 2−, Cl − and HCO 3 − in precipitation, throughfall, forest floor percolate and mineral soil solution were evaluated, and the annual flux of H +, NO 3 −, SO 4 2− and base cations was calculated. The annual input of cations by bulk precipitation was only a small proportion (17%) of the flux collected below the forest floor. The deposition of SO 4 2− and NO 3 − in bulk precipitation accounted for 85 and 45%, respectively, of the forest floor fluxes of these ions. The annual flux of H + in throughfall was less than that in precipitation. Calcium and Mg 2+ concentrations in soil solution were highly correlated ( P = 0.05) with NO 3 − during the dormant season and Ca 2+ was highly correlated with SO 4 2− during the growing season. Both SO 4 2− and NO 3 − were largely unreactive with minerals in the Turkey Lakes soil and therefore play a dominant role in cation movement through the soil.

Acid deposition near a sour gas plant in southwestern Alberta

Atmospheric fallout in the vicinity of a sour gas plant in southwestern Alberta was collected on an event basis with bulk precipitation collectors during June, July and August of 1972, 1973 and 1982. Samples were collected at 9 sites within 20 km of the plant. Total atmospheric sulfation measurements defined a higher exposure area located downwind of the plant, but the precipitation measurements did not. Bulk deposition of H+ ion in the study area was an average 10.77 mmol H+ m−2 3 mol−1 in 1972 and 0.014 and 0.049 in 1973 and 1982, respectively. 1972 samples were also significantly more acidic (average pH of 4.3 vs 5.7 in 1973 and 5.3 in 1982). Deposition of SO4= averaged 2.1 kg S ha−1 3 mol−1 in 1972 and 0.96 and 0.72 in 1973 and 1982. The higher deposition of both S and H+ in 1972 is mainly a result of more precipitation. There was no significant correlation between H+ and SO4= species in the samples. There was no significant relationship between plant S emissions and deposition rates, or plant S emissions and average total atmospheric sulfation measurements.