Dry Deposition Of Sulphur Dioxide Research Articles

Impact of shipping emissions on air pollution and pollutant deposition over the Barents Sea

Arctic warming leading to reduced summertime sea-ice is likely to lead to increased local shipping especially along the Northeast Passage near the northern coasts of Norway and Russia, which are shorter than the traditional southerly routes. Here, the regional chemistry-transport model WRF-Chem is used to examine the effects of shipping emissions on levels of air pollutants and deposition fluxes over the Barents Sea both for present-day and future conditions, based on a high growth scenario. Present-day shipping emissions are found to have already substantial effects on ozone concentrations, but limited effects on sulphate and nitrate aerosols. Predicted future changes in ozone are also important, particularly in regions with low nitrogen oxide concentrations, and results are sensitive to the way in which diversion shipping is distributed due to non-linear effects on photochemical ozone production. Whilst modest future increases in sulphate and nitrate aerosols are predicted, large enhancements in dry deposition of sulphur dioxide and wet deposition of nitrogen compounds to the Barents Sea are predicted. Such levels of future nitrogen deposition would represent a significant atmospheric source of oceanic nitrogen affecting sensitive marine ecosystems.

Assessing Meteorological Variable and Process Relationships to Modeled PM2.5 Ammonium Nitrate and Ammonium Sulfate in the Central United States

Abstract Many counties are required to submit an emissions control plan to the U.S. Environmental Protection Agency to reduce concentrations of particulate matter of less than 2.5 μm in diameter (PM2.5), which are dominated by ammonium sulfate and ammonium nitrate in the central United States. These control scenarios are simulated with photochemical models, which use emissions and meteorological variables to simulate PM2.5 formation, transport, and deposition. A monitor study was established in the central United States to measure simultaneously the PM2.5 sulfate ion, nitrate ion, ammonium ion, and chemical precursor species sulfur dioxide, nitric acid, and ammonia during 2004. These data, combined with nearby meteorological observations, provide an opportunity to assess whether meteorological variables or deposition processes may introduce systematic biases in PM2.5 ammonium sulfate and ammonium nitrate predictions. Skill in estimating total wet deposition is assessed by comparing model output with National Atmospheric Deposition Program monitors in the region. Meteorological variables that are important for mass transport (wind vector) and thermodynamic chemistry (temperature and relative humidity) compare well to observations. A model sensitivity, in which the temperatures in the inorganic chemistry module are adjusted to compensate for an underprediction bias, shows a minimal model response in predicted PM2.5 ammonium nitrate. The dry deposition of sulfur dioxide seems to have a systematic impact on ambient estimates of sulfur dioxide in the photochemical model. An attempt to correlate bias and error in meteorological variables to bias and error in PM2.5 species showed the most relationship between relative humidity and temperature and ammonium nitraite. Wet deposition of total sulfate, nitrate, and ammonium tend to be underpredicted in the winter months.

Laboratory measurement of the dry deposition of sulfur dioxide onto northern Chinese soil samples

We investigated soil surface resistance R c to dry deposition of sulfur dioxide (SO 2) onto different types of soils in laboratory experiments, using samples collected from the arid loess plateau and deserts of northern China. We evaluated the factors that affect R c, which depends on the physical and chemical interaction between a trace constituent and the deposition surface. We observed that the values of R c for SO 2 decreased with increase of soil weight and increased with SO 2 concentration, although surface coverage had little effect on R c. The SO 2 uptake rate by all the northern Chinese soil samples seemed to be, on the whole, dependent on relative humidity (RH). In all of the northern Chinese soil samples, R c was in the range 0.028–0.65 s mm −1, and was exponentially related to the effective surface area of each soil sample, regardless of RH. Wet chemical analysis of sulfur deposited onto the soil samples showed that oxidation ratio of sulfur(IV) to sulfur(VI) was related to RH, which might be related to complex interactions among the amount of water on the soil sample, the pH, and the metallic ions in the liquid phase.

Laboratory and field measurements of dry deposition of sulfur dioxide onto Chinese loess surfaces.

Laboratory and field measurements were conducted to examine dry deposition of SO2 onto Chinese loess surfaces using native soil sampled in the loess plateau, China. The field tests were employed in Beijing and Lanzhou, China, by directly measuring the dry deposition of SO2 on soil, which uses soil put on a collector as an SO2 passive sampling medium. In the laboratory, a high rate of uptake to SO2 deposition for Chinese soil surfaces due to the highly alkalinity was found. The uptake of SO2 deposition was dependent on the pH soil and relative humidity. Furthermore, we evaluated some factors that affect the measurement precision: response of SO2 uptake, repeatability, recovery factor, and variability associated with the weight and the surface coverage on the collectors. As a result, it was shown that the measurement precision was primarily related to the ratio of the SO2 deposition amount relative to the sulfur content of the original soil. This result was consistent with the field observations. The laboratory and field results indicated an excellent agreement on the SO2 uptake inherent in the results from the soil surfaces in different regions.

Temporal changes and fluxes of sulphur and calcium in wet and dry deposition, internal circulation as well as in run-off and soil in a forest at Gårdsjön, Sweden

Sulphur dioxide in air as well as dry deposition of sulphur dioxide to a forest has decreased by a factor of 20 during the last two decades. It was earlier found that the internal circulation of calcium in Norway spruce follows the dry deposition of sulphur dioxide. The sulphur and calcium fluxes from 1992 were calculated from wet deposition, throughfall and a surrogate surface. Earlier fluxes from 1981 to 1991 were calculated using assumptions of the dry deposition of non-marine sulphate and calcium. The new estimates confirm the earlier studies that the internal circulation of calcium in a coniferous forest is directly related to the dry deposition of sulphur dioxide to the canopies and that the internal circulation of calcium decreases at the same rate as the deposition of sulphur decreased during the last two decades. The deposition fluxes were also compared to run-off and uptake of calcium in the forest as well as on modelled weathering rates from severely acidified forested catchments near the coast and inland and the soil pool. A reconstruction of changes in the soil pool of calcium over the last 100 years indicate that the soil pool has decreased by ca. 70% in catchments with complete harvest of the forest and ca. 40% if branches and needles are left on the ground. In a natural forest without acid deposition the soil pool of calcium would have increased by 6%. Estimates for the 21st century show that harvesting of stems + branches and needles may almost empty the soil pool of calcium in the next 100 years. Increased nitrogen deposition has increased forest growth, which indirectly increased uptake of calcium by the trees and indirectly caused a further decrease of the soil pool of calcium.

Regional estimation of pollutant gas dry deposition in the UK: model description, sensitivity analyses and outputs

A “big-leaf” resistance analogy model for dry deposition of sulphur dioxide, nitrogen dioxide, ammonia and nitric acid is described with a stomatal compensation point included to allow bi-directional exchange of ammonia. The model derivation is constrained by measurement data and it is parameterized for UK conditions. Monthly average dry deposition estimates are provided at the 5 km×5 km spatial scale. The model uses data available nationally at the appropriate spatial and temporal scales, such as gas concentration, land use, wind speed, temperature, rainfall and vapour pressure. A method is presented to overcome the lack of suitable solar radiation data. The effect of uncertainty in model inputs and in model parameterization is explored using sensitivity analyses. SO 2 deposition is sensitive to variation in gas concentration, wind speed and wet surface uptake parameters. NO 2 deposition is sensitive to parameters and inputs regulating stomatal behaviour, including solar radiation and temperature, as well as to gas concentration. The use of monthly or annual average NO 2 concentrations may underestimate deposition substantially in some areas. HNO 3 dry deposition is sensitive to wind speed and concentration. NH 3 dry deposition to moorland and forest land uses, where the majority of deposition occurs, is sensitive to concentration, wind speed and choice of canopy resistance parameters. For arable and grassland areas, with both deposition and emission of NH 3, the model is sensitive to all the model inputs and parameter choices. A full uncertainty analysis requires further work on the reliability of input variables and model parameter choices but these results quantitatively focus on the important areas of the model for each gas. Estimated dry deposition to the UK (excluding Northern Ireland) of SO 2 is 135 Gg S yr −1 for 1996, for NH 3 is 97 Gg N yr −1, for NO 2 is 26 Gg N yr −1 and the preliminary estimate for HNO 3 is 42 Gg N yr −1. For sulphur and reduced nitrogen, estimated dry deposition accounts for 40% of total deposition, including wet and cloud droplet deposition. NO 2 dry deposition only accounts for 15% of total oxidised nitrogen deposition, but another 25% may come from the dry deposition of HNO 3, giving a similar 40% overall by dry deposition. The sensitivity of the model to parameter values and the comparisons of modelled output with measurements show that parameter choices may be valid only at the scale of European countries rather than the whole continent.

Enhancement of the dry deposition of sulphur dioxide to a forest in the presence of ammonia

A section of Scots pine ( Pinus sylvestris) forest in central Scotland was fumigated with NH 3 between March and October 1993 from a point source 5 m above the forest canopy. Measured throughfall composition, sampled weekly, showed enhanced deposition of both NH + 4 and SO 2- 4 ions below the fumigated area, relative to the adjacent control area. Comparison of the additional amounts of SO 2- 4 measured in throughfall in the fumigated area relative to the control area with possible causal factors showed (i) a positive correlation between the average additional SO 2- 4–S flux in a sampling period and the average % time that the surface was wet, and (ii) a positive correlation between the average deposition velocity for the additional SO 2- 4–S relative to SO 2 and the average rate of NH 3 release during a sampling period. The results imply that the surface resistance to the dry deposition of SO 2 is small relative to the atmospheric resistance during periods of NH 3 fumigation, and that the deposition velocity for SO 2 is therefore dependent on ambient NH 3 concentrations. In regions where NH 3 and SO 2 concentrations are similar, a knowledge of ambient NH 3 concentrations is therefore a requirement for the development of accurate models of the dry deposition of SO 2 to vegetation, and the estimation of Critical Loads for S deposition.

Mapping of critical loads and levels for pollution damage to building materials in the United Kingdom

The United Kingdom National Materials Exposure Programme was initiated in 1986 to study the effects of acid deposition on building materials. The output data in the form of empirical dose-response equations (described elsewhere) have been incorporated into a geographical information system (GIS). In addition, data for the stock at risk of building materials has also been used. The dose-response relations indicate a dominance of dry deposition of sulphur dioxide in the decay process. Critical level/load maps have been determined for a number of materials. General pollution and meteorological data sets are also included in the mapping process. Maps give ‘exceedence squares’ on a 20 km square grid basis, indicating the unprotected areas or those still at risk for a given scenario for SO2 reduction in the context of the UNECE protocol for sulphur. In order to derive maps of areas sensitive to pollutants in the future a model, HARM 7.2, is used for the prediction of distribution of emissions of pollutants in the UK. A series of maps has now been produced for different materials at 70% and 80% scenarios for the reduction of SO2. Studies of the sensitivity of the exceedence maps to the accuracy or variation of the components in the dose-response equations have been undertaken. Results from the mapping programme and the sensitivity analysis are presented together with discussion of the concept of critical loads of materials.

Throughfall deposition of ammonium and sulphate during ammonia fumigation of a scots pine forest

The estimation of the dry deposition of sulphur dioxide to forests is confounded by the possibility of codeposition of SO 2 with NH 3 on leaf surfaces. A sector of Scots pine forest was selectively fumigated with NH 3 to give average concentrations up to 15 ppbV (nL L -1 ) above ambient, in order to test the hypothesis that increased air concentrations of NH 3 would enhance the dry deposition of SO 2 , and the consequent amounts of SO 4 2- measured in throughfall below the forest canopy. Ammonia gas, generated by evaporation of concentrated aqueous solution, was released above the canopy in proportion to wind speed when the wind direction was between south and west. Concentrations of NH 3 at canopy height were measured using passive diffusion tubes; throughfall was preserved with thymol and measured weekly. Meteorological data and SO 2 concentrations were recorded continuously, to permit the estimation of dry deposition input. Deposition of NH 4 + in throughfall over 8 months was increased by up to 40 meq m -2 relative to 'control' sites upwind of the NH3 release point, with largest values closest to the release point. Deposition of SO 4 2- in throughfall was also enhanced in the fumigated area, by up to 20 meq m -2 , even though average ambient SO 2 concentrations were 2.3 ppbV. The results are discussed in terms of the factors controlling SO 2 deposition on forest surfaces, the development of appropriate deposition models, and their relevance to using throughfall as an estimate of total S deposition.

The United Kingdom national materials exposure programme

In 1986, the National Materials Exposure Programme was set up within the United Kingdom to investigate the effects of acid deposition on buildings and building materials. Thirty sites were chosen, which represented a range of geographical and pollution climates. Each site met a minimum meteorological and pollution monitoring regime (including SO2, NO2). After four years, other sites were included (with less frequent data collection) and some sites removed. At each site, samples of 3 types of stone, mild steel, painted steel, Cu, Al and galvanised steel were exposed, with some of the stone sheltered from direct precipitation. Samples were removed periodically for analysis and dose-response relations derived for different materials. The empirical relationships derived are in the form of: decay rate=a [SO+] + b [H2] + c [rainfall] + d These dose response relations have been used to develop critical load maps for materials for the United Kingdom. Eight years of data have been collected, some for the UNECE task force programme. Laboratory tests using an Atmospheric Flow Chamber were also undertaken. Since the beginning of the programme addition materials have been exposed on some sites including mortars. A further set of eight sites has been used to assess the effects of ozone on a range of organic materials (for example polyvinyl chloride, polycarbonate, sealants). The paper presents up-to-date findings for the programme and confirms the dominance of dry deposition of sulphur dioxide as the main decay process for sensitive materials in areas of significant pollution.

Dry deposition of sulphur dioxide and ammonia on wet surfaces and the surface oxidation kinetics of bisulphite

The dry deposition of (SO 2) g in air on a thin water layer was measured in a small wind tunnel at wind velocities from 0.5 to 6.0 m s −1 and water-layer thicknesses of 4–4600 μm. A reasonable estimate could be made of the concentrations in the gas and in the liquid phase, based on chemical analysis of the water layer and on Fick's first law. The interface is regarded as a reactive surface for gases, and the reactions with that can be described with uptake- and release-rate constants. For NH 3 and SO 2 these constants are strongly dependent on pH; NH 3 was used as a pH regulator. We concluded from the experiments with different water-layer thicknesses that during dry deposition, oxidation of HSO 3 − occurs at the surface of the water. The greater part of the S(IV) oxidation does not take place in the bulk of the liquid and the results cannot be explained with the oxidation of the SO 3 2− ion. The kinetic equation for the surface oxidation was found to be [ S( IV)] 1Vt −1=k ox[ HSO 3 −] 10 2 3 [O x] gO n mols −1 with n = 2 3 for ozone and unknown for oxygen. The apparent rate constants (m 4mol −1s −1) for oxygen (with arbitrarily n = 2 3 ) and ozone oxidation between 5 and 20°C are for oxygen: k O2=3.3×10 21 exp( 6820 T ) for ozone: k O3=7.7×10 7 exp( 1750 T ) The oxidation of S(IV) with both O2 and O3 can be described with the reaction of an activated HSO 3 − or HS 2O 5 − surface complex. The reaction-rate constants are independent of pH and water-layer thickness. The positive apparent activation energy points to a more complicated mechanism than is represented. With ozone, the reaction is of second order. The represented results can possibly be of importance for the modelling of the dispersion of air pollution. The results point to an influence of the drop size (available reactive surface) on the S(IV) oxidation rate.

The effect of humidity on the dry deposition of sulfur dioxide onto calcareous stones

An atmospheric flow chamber ( AFC ) has been used to simulate a polluted atmosphere with controlled levels of sulfur dioxide (SO 2 ) and relative humidity ( RH ). Calcareous stones were placed in the afc for 30 days and subjected to a range of SO 2 and rh conditions. Half the samples were subjected to simulated rain whilst the rest were kept dry. The degree of reaction was determined by measuring total sulfate formed which was then used to formulate damage functions. A square-root relationship was obtained between SO 2 and sulfate formed on a wet surface, which was unaffected by humidity. Deposition onto a dry surface was an order of magnitude lower than that onto a wet surface and appeared to be dependent on humidity. To model sulfate formation successfully the time of wetness has to be measured or calculated from the frequency and duration of rain events. Using a substitute such as a critical humidity value for a given length of time is not a valid approach.

Effects of acidic deposition on the erosion of carbonate stone — experimental results from the U.S. National Acid Precipitation Assessment Program (NAPAP)

One of the goals of NAPAP-sponsored research on the effects of acidic deposition on carbonate stone has been to quantify the incremental effects of wet and dry deposition of hydrogen ion, sulfur dioxide and nitrogen oxides on stone erosion. Test briquettes and slabs of freshly quarried Indiana limestone and Vermont marble have been exposed to ambient environmental conditions in a long-term exposure program. Physical measurements of the recession of test stones exposed to ambient conditions at an angle of 30° to horizontal at the five NAPAP materials exposure sites range from ∼ 15 to ∼ 30 μm yr −1 for marble, and from ∼ 25 to ∼ 45 μm yr −1 for limestone, and are approximately double the recession estimates based on the observed calcium content of run-off solutions from test slabs. The difference between the physical and chemical recession measurements is attributed to the loss of mineral grains from the stone surfaces that are not measured in the run-off experiments. The erosion due to grain loss does not appear to be influenced by rainfall acidity, however, preliminary evidence suggests that grain loss may be influenced by dry deposition of sulfur dioxide between rainfall events. Chemical analyses of the run-off solutions and associated rainfall blanks suggest that ∼ 30% of erosion by dissolution can be attributed to the wet deposition of hydrogen ion and the dry deposition of sulfur dioxide and nitric acid between rain events. The remaining ∼ 70% of erosion by dissolution is accounted for by the solubility of carbonate stone in rain that is in equilibrium with atmospheric carbon dioxide (“clean rain”). These results are for marble and limestone slabs exposed at an angle of 30° from horizontal. The relative contribution of sulfur dioxide to chemical erosion is significantly enhanced for stone slabs having an inclination of 60° or 85°. The dry deposition of alkaline particulate material has a mitigating effect at the two urban field exposure sites at Washington, DC, and Steubenville, OH.

Relation between estimated dry deposition and throughfall in a coniferous forest exposed to controlled levels of SO 2 and NO 2

Throughfall was collected in a Scots pine forest exposed to about 14 μg m −3 of both SO 2 and NO 2, and in a control forest with 1 μg m −3 SO 2 and < 1 μg m −3 NO 2. Precipitation was collected in a nearby open field. Collection was performed on an event basis during the whole vegetation period. Exposure was made by an open-air release system during the vegetation period, except during rain and at night. Additional sulfate deposition in the exposed forest (compared to control forest) was nearly equal to dry deposition of sulfur dioxide, as estimated with a stomatal conductance model adapted for the particular forest. It is thus concluded that essentially all of the dry deposited sulfur dioxide is eventually extracted and appears in throughfall—including the fraction that has been deposited through stomata. Attempts to relate net throughfall deposition to dry deposition of sulfate in the control forest were inconclusive, since a minor (10%) uncertainty in the water balance had a major influence on calculated deposition velocity for particulate sulfate. Nitrate throughfall deposition is about half of the open field wet deposition, both for the exposed and control forest. Thus, a long-term exposure with about 14 μg m −3 NO 2 decreased nitrate throughfall deposition.

A Numerical Modeling Technique for Estimating Sulfur Dioxide Dry Deposition Due to Local Source Emissions

This paper describes a methodology for estimating the effect of local source emissions on dry deposition of sulfur dioxide in regions of complex terrain. Airflow in complex terrain is simulated by a time-dependent dynamical model for the meteorological fields. The results of the dynamical model are used to drive a semi-stochastic Lagrangian dispersion model in order to evaluate concentrations resulting from local source emissions. The Lagrangian dispersion model is coupled with a dry deposition treatment which includes the effects of both surface properties and micrometeoroiogical factors on deposition. A sample application is discussed for a source in the Shenandoah Valley. The largest concentrations and deposition rates were obtained shortly after sunrise, during the transition from the nocturnal to the daytime flow regime. These results suggest that dry deposition may be episodic.

Dry deposition of sulfur dioxide or nitric acid to oak, elm and pine leaves

To improve our knowledge of atmospheric inputs to forests, experiments were performed in the field to measure the dry deposition of SO 2 and HNO 3 to oak, elm, and pine leaves. A thee branch was enclosed in a Teflon chamber, through which SO 2 or HNO 3 flowed. The dry deposition characteristics of SO 2 and HNO 3 were very different. The SO 2 deposition occurred primarily through stomatal openings for the oak and pine leaves, and equal stomatal and cuticular deposition was observed for the elm leaves. The deposited SO 2 could not be removed from the branch by extracting in water or by revolatilization. In contrast, over 90% of HNO 3 dry deposition occurred to the cuticle. Most of the deposited HNO 3 could be extracted from the leaves. Revolatilization of HNO 3 was negligible from an active branch, but increased from a dormant or detached branch. A deposition velocity was derived from the ratio of the flux of the gas to the leaves and the gas concentration in the chamber. Deposition velocities ranged from 0·02 to 0·11 cm s −1 for SO 2 and from 0·2 to 1·2 cm s −1 for HNO 3 to individual leaf surfaces.

The dry deposition of sulfur dioxide on a loblolly pine plantation

The dry deposition of sulfur dioxide on a loblolly pine plantation

The dry deposition of sulfur dioxide on a loblolly pine plantation

A concentration gradient/resistance model approach was used to determine the flux density, deposition velocity, and transport resistances for sulfur dioxide (SO 2 ) between the atmosphere and a loblolly pine ( Pirms taeda L.) plantation. Measurements were made on 54 clear to partly sunny days during the period from June 1982 to May 1983. For this stand and these days, the average daylight flux density was 0.052 μg m −2s −1 and the deposition velocity for SO 2 was 0.72±0.65 cms −1. The average transport resistance for SO 2 includes the aerodynamic resistance ( r a ), canopy resistance ( r c ), and internal resistance corrected for solubility ( r ir ). The values for these resistances were 15 ±4, 127 ±94 and 14+-39 s m −1, respectively.

Deposition-plant-soil interactions

Rainwater reaching the ground as throughfall beneath vegetation usually shows an increase in pH, except in areas where sulphur dioxide deposition can be presumed to be high. Stemflow, however, is almost always reduced in pH. The changed acidity in throughfall results from hydrogen-ion exchange for base cations at leaf surfaces, with evidence that potassium, calcium and magnesium are all involved. Amounts of base cations gained are much greater than the losses of hydrogen ions from bulk precipitation. Either other processes are involved, or the extra base cations exchange for acidity resulting from dry deposition of sulphur dioxide. Further interpretation is confounded by the lack of general agreement as to the relative contributions of dry deposition and of crown leaching to the sulphate gained by throughfall. Usually plants are able to replace leached cations, even when treated with very low pH rain. However, there are suggestions from Germany that exceptional rates of leaching of magnesium from tree foliage may be leading to growth decline and death. For such extreme losses to occur cell membranes must first be dam aged, with gaseous pollutants, such as ozone and sulphur dioxide, and frost both being implicated. Because the base cations gained at leaf surfaces had previously been exchanged for hydrogen ions at the root-soil interface, exchange in the crowns is merely an extension of the soil exchange process and can be regarded as an acid stress upon the soil.

Uptake of SO2 in shoots of Scots pine: field measurements of net flux of sulphur in relation to stomatal conductance

Abstract. Net fluxes of gaseous sulphur compounds, water vapour and carbon dioxide to current‐ and one‐year‐old shoots of Scots pine were simultaneously measured in the field. The shoots were fumigated in temperature‐controlled assimilation chambers with sulphur dioxide at concentrations ranging from 40 to 250 μg m−3 (15–95 ppb). The hypothesis that stomatal opening regulates the uptake of sulphur dioxide was tested. The following conclusions were reached concerning the dry deposition of sulphur dioxide to a dry coniferous shoot.There was a marked diurnal variation in the uptake rate of sulphur dioxide. The net deposition velocity of sulphur was about three times higher during the day than during the night during July‐October. Stomatal opening was not the primary factor controlling the dry deposition rate of sulphur dioxide. The net dry deposition rate was significantly smaller than the calculated rate based on stomatal conductances for water vapour.Part of this deviation could be explained by re‐emission of reduced sulphur compound(s) from the needles. The re‐emission of sulphur was a light‐dependent process and might be of great significance for the sulphur balance calculations.A variable deposition velocity should be used in atmospheric transport models to account for the diurnal and seasonal variation in the surface resistance of a dry canopy.