Deposition Velocity Of SO Research Articles

Observation of SO 2 dry deposition velocity at a high elevation flux tower over an evergreen broadleaf forest in Central Taiwan

A 60-m flux tower was built on a 2100 m mountain for the measurement of the air pollutant concentration and the evaluation of dry deposition velocity in Central Taiwan. The tower was constructed in an evergreen broadleaf forest, which is the dominant species of forest in the world. Multiple-level SO 2 concentrations and meteorological variables at the site were measured from February to April 2008. The results showed that the mean dry deposition velocities of SO 2 were 0.61 cm s −1 during daytime and 0.27 cm s −1 during nighttime. From the comparison of the monthly data, a tendency was observed that the dry deposition velocity increases with LAI and solar radiation. Furthermore, it was observed that the deposition velocity was larger over wet canopy than over dry canopy, and that higher deposition velocities in the wet season were mainly caused by non-stomatal uptake of wet canopy. Over wet canopy, the mean dry deposition velocities of SO 2 were estimated to be 0.83 cm s −1 during daytime and 0.47 cm s −1 during nighttime; and 0.44 cm s −1 during daytime and 0.19 cm s −1 during nighttime over dry canopy. There is good agreement between the results of this study and those in other studies and the predictions of Zhang et al. (2003a). The medians (geometric means) of derived r c during daytime are 233 (266) m s −1 over dry canopy and 147 (146) m s −1 over wet canopy. It was found that solar radiation is the critical important meteorological variable determining stomatal resistance during daytime. For non-stomatal resistance, clear dependencies were observed on the friction velocity and relative humidity.

Millennium-long damage to building materials in London

Damage functions from a range of sources are used to estimate deterioration of carbonate stone, iron and copper, in addition to the rate of blackening of stone surfaces in London across the period 1100–2100 CE. Meteorological and pollution input is available for only a relatively short part of this span, so non-instrumental weather records and modelled pollution are utilised for historic values, while future climate is adapted from the HadCM3A2 model output and pollution assessed from likely regulatory trends. The results from the different damage functions compare reasonably well showing comparable changes in damage rates with time. A potential square-root dependence of change in deposition velocity of SO 2 to limestone suggests a possible overestimate of damage when pollution is high. Deterioration is especially intense from the 1700s. It is difficult to be certain whether the corrosion of copper accelerated as early as this or it developed in the 20th century. Nevertheless all the functions predict a decline in copper corrosion from the end of the 20th century. A blackening function was developed to relate elemental carbon concentration and the colour of deposited particulate matter to blackening rate, which suggests that soiling was particularly rapid in the late 19th century. The increase and subsequent decrease in damage to building materials is interpreted in terms of a Kuznets curve. The centuries where pollution controlled damage to durable building material seems to be over. Weathering, in a changing climate may have the greatest impact in the future.

Dry deposition velocity of sulfur dioxide over rice paddy in the tropical region

The SO 2 deposition velocity over a canopy of irrigated rice paddy in a tropical area was evaluated using the Bowen ratio and Fick's equations. The experimental facilities were set up in Chachoengsao province in the central region of Thailand and data was collected for a period of one year. The results showed that the deposition velocity of SO 2 varies with the time of day, and it was highest around noon time and lowest at night. Furthermore, the value for the seasonal average of V d was the highest in winter and the lowest in the rainy season. The obtained seasonal average values of V d were 0.67, 1.25, and 1.51 cm/s in the winter, summer, and rainy seasons, respectively.

Atmospheric sulfur deposition and the sulfur nutrition of crops at an agricultural site in Jiangxi province of China

During the period From November 1998 to October 1999, the air sulfur dioxide (SO 2 ) and sulfate (SO 2− 4 ) concentrations were measured and rain water was collected on farmland at Yingtan, a typical red soil area in the Jiangxi province of China. Based on hourly meteorological data and surface resistance data from the literature, the dry deposition velocities of SO 2 and SO 2− 4 were computed using a three-layer resistance analogy model, and sulfur dry deposition was calculated. The wet deposition was obtained from precipitation amount and sulfur concentrations in rainwater. The average dry deposition velocities of SO 2 and SO 2− 4 on farmland were found to be 0.38 ± 0.16 cm s −1 (monthly average 0.16–0.55 cm s −1 ) and 0.20 ± 0.12 cm s −1 (monthly average 0.15–0.27 cm s −1 ), respectively. The annual total sulfur deposition for the study region is about 103 kg S ha −1 , of which 83% is dry deposition. The uncertainties due to measurement and the dry deposition model are less than 30%. It is also found that atmospheric deposition plays a key role in sulfur circulation within the agrecosystem, accounting for more than 90% of the total sulfur input to farmland DOI: 10.1046/j.1435-6935.2003.00076.x

Description and evaluation of a model of deposition velocities for routine estimates of dry deposition over North America. Part II: review of past measurements and model results

Numerical sensitivity tests and four months of complete model runs have been conducted for the Routine Deposition Model (RDM). The influence of individual model inputs on dry deposition velocity as a function of land-use category (LUC) and pollutant (SO 2, O 3, SO 2− 4 and HNO 3) were examined over a realistic range of values for solar radiation, stability and wind speed. Spatial and temporal variations in RDM deposition velocity ( V d) during June – September 1996 time period generated using meteorological input from a mesoscale model run at 35 km resolution over north-eastern North America were also examined. Comparison of RDM V d values to a variety of measurements of dry deposition velocities of SO 2, O 3, SO 2− 4 and NHO 3 that have been reported in the literature demonstrated that RDM produces realistic results. Over northeastern NA RDM monthly averaged dry deposition velocities for SO 2 vary from 0.2 to 3.0 cm s −1 with the highest deposition velocities over water surfaces. For O 3, the monthly averaged dry deposition velocities are from 0.05 to 1.0 cm s −1 with the lowest values over water surfaces and the highest over forested areas. For HNO 3, the monthly averaged dry deposition velocities have the range of 0.5 to 6 cm s −1, with the highest values for forested areas. For SO 2− 4, they range from 0.05–1.5 cm s −1, with the lowest values over water and the highest over forest. The monthly averaged dry deposition velocities for SO 2 and O 3 are higher in the growing season compared to the fall, but this behaviour is not apparent for HNO 3 and sulphate. In the daytime, the hourly averaged dry deposition velocities for SO 2, O 3, SO 2− 4 and HNO 3 are higher than that in the nighttime over most of the vegetated area. The diurnal variation is most evident for surfaces with large values for leaf area index (LAI), such as forests. Based on the results presented in this paper, it is concluded that RDM V d values can be combined with measured air concentrations over hourly, daily or weekly periods to determine dry deposition amounts and with wet deposition measurements to provide seasonal estimates of total deposition and estimates of the relative importance of dry deposition.

Description and evaluation of a model of deposition velocities for routine estimates of air pollutant dry deposition over North America.: Part I: model development

This paper describes the development of a detailed dry deposition model for routine computation of dry deposition velocities of SO 2, O 3, HNO 3 and fine particle SO 4 2− across much of North America. Four different dry deposition/surface exchange sub-models have been combined with the current Canadian weather forecast model (Global Environmental Multiscale model) with a 3 h time resolution and a horizontal spatial resolution of 35 km. The present model uses the US Geological Survey North American Land Cover Characteristics data to obtain fourteen different land use and five seasonal categories. The four sub-models used are a multi-layer model for gaseous species over taller canopy land-use types, a big-leaf model for gaseous species over lower canopies (including bare soil and water) and for HNO 3 under all surface types and, two different models for SO 4 2−, one for tall canopies and the other for short canopies. All necessary parameters for each sub-model, chemical species, land-use and seasonal categories have been selected from available data libraries or from the values reported in the literature. The purpose for developing this model (referred to as the Routine Deposition Model (RDM)), when coupled with air concentration data, is to provide estimates of seasonal dry deposition, which can be combined with wet deposition to produce total deposition estimates. Model theory is discussed in this paper and model sensitivity tests and results will be presented in a companion paper.

Chemistry of dimethyl sulfide in the equatorial Pacific atmosphere

A field study of the chemistry of dimethyl sulfide (DMS) was conducted on the island of Kiritimati (Christmas Island) during July and August, 1994. This island is located at 2°N, 157°W approximately 2000 km south of Hawaii. We obtained a very repeatable diurnal variation for both DMS and sulfur dioxide (SO2) during two 5‐day and one 2‐day experiments. Near sunrise DMS was about 200 pptv. It decreased to about 120 pptv by late afternoon. During the daytime SO2 increased from about 20 pptv to about 75 pptv. At night DMS increased and SO2 decreased almost linearly. About 62% of the DMS was converted to SO2. DMS was emitted from the ocean at an average flux of 3.7 × 1013 molecules m−2 s−1. The average dry deposition velocity of SO2 was 6.8 mm sec−1. Most of the SO2 appeared to be lost to the ocean although a comparable but not significantly larger flux to aerosol cannot be ruled out. Dimethyl sulfoxide was in the range 10 to 50 pptv with a mean of about 25 pptv. Dimethyl sulfone was in the range 0 to 15 pptv with a mean of about 3 pptv. There was no diurnal trend in either species. A much smaller fraction of the DMS was converted to dimethyl sulfone than dimethyl sulfoxide.

Dry deposition to pine of sulphur dioxide and ozone at low concentration

Deposition velocities of SO 2 and O 3 were measured with an enclosure technique onto a stand of pine in central Sweden, mainly in autumn at low SO 2 concentrations (3–5 ppbv). The deposition velocities for both gases were substantially larger than corresponding stomatal conductances, estimated from simultaneous measurements of water transpiration. The additional deposition is explained as an external deposition which was found to vary over the day with a maximum at noon and almost no deposition at night. Estimated for a dry canopy of pine (leaf area index = 3 m 2 m −2), the 24 h average external deposition velocity of SO 2, was 3.3 mm s −1 while the stomatal conductance for the same gas was only 1.3 mm s −1. A few additional measurements made during summer indicate that the external deposition can be even larger than what was obtained during October. If so, current estimates of SO 2 deposition to dry canopies of conifers based on the stomatal resistance approach need to be revised upwards.

Laboratory measurements of sulfur dioxide deposition velocity on marble and dolomite stone surfaces

The deposition velocity of SO 2 on marble and dolomite stone surfaces in a humid atmosphere was measured as a function of time in the laboratory using continuous monitoring techniques. The deposition velocity of SO 2 on marble varied between 0.02 and 0.23 cm s −1, and was generally observed to decrease with time. The deposition velocity of SO 2 on dolomite varied between 0.02 and 0.10 cm s −1, and gradually increased over the first 2000 ppm-h of exposure. For both types of stones, the deposition velocity increased significantly when condensed moisture was observed on the stone surface. Chemical analysis of the stone samples indicated that the SO 2 deposited reacted with the stone materials to form gypsum (CaSO 4·2H 2O) on the marble surfaces and gypsum and epsomite (MgSO 4·7H 2O) on the dolomite surfaces.

Atmospheric sulphur deposition to forest stands: Throughfall estimates compared to estimates from inference

Wet and dry deposition of sulphur was estimated for 30 forest stands in the Netherlands using a throughfall method and an inferential method. Dry deposition estimates of the throughfall method were significantly higher compared to estimates from inference. The major sources of uncertainty of the throughfall dry deposition estimates were associated with non-representative throughfall sampling, wet deposition estimates, canopy exchange processes, deposition of neutral salts, dry deposition directly onto the throughfall collectors, and with the omission of stemflow fluxes and dry deposition directly to the undergrowth vegetation and forest floor. These uncertainties were found to act both ways to approximately the same extent and were not able to explain the observed gap between the two dry deposition estimates. For the inferential method, major sources of uncertainty in the dry deposition estimates arose in calculation of the dry deposition velocity of SO 2 and the omission of occult deposition of SO 4 2−. In this study, uncertainties associated with the spatial averaging of air concentrations of SO 2 and SO 4 aerosol and the calculation of the deposition velocity of SO 4 aerosol were found to be relatively small. Modifying the R c parametrization of SO 2, based on recent dry deposition measurements made over heather in the Netherlands, resulted in fairly good agreement between both dry deposition estimates. Occult deposition of SO 4 2− was found to contribute significantly to the total sulphur deposition to the forest stands. Both the modified R c parametrization and the incorporation of occult deposition led to systematically higher sulphur deposition estimates by the inferential method compared to originally inferred deposition. This implies that in the Netherlands, sulphur deposition to forest ecosystems might have been underestimated heretofore.

Mass balances of sulphur and nitrogen oxides over Great Britain

From aircraft measurements in air entering and leaving Great Britain conclusions about the cycles of nitrogen and sulphur oxides on a regional scale are drawn. Using a tracer it is possible to follow the dispersion of plumes over distances of hundreds of km. For sulphur oxides, in the absence of precipitation, overall removal is shown not to be very efficient with 70 % of the emitted SO 2 still airborne over the coast. Estimates are made of the deposition velocity of SO 2 and its rate of oxidation to sulphate. For nitrogen oxides the removal mechanisms in dry conditions appear to be of similar magnitude, though individual loss mechanisms are less certain. The importance of background levels in air entering the country is assessed. The roles of other airborne materials, such as O 3 and ammonium (of which observations were made) are related to the S and NO x cycles in the atmosphere. It is argued that they and their degree of mixing with polluted air may have a strong influence on removal in rain.

Dry deposition of SO 2 and NO x in winter

The deposition velocity of SO 2, NO and NO 2 to a coniferous forest in winter is estimated to be less than 0.03 cm s −1. Deposition velocity to a snow cover depends on the temperature.