Average Dry Deposition Velocity Research Articles

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.

Measured fluxes of sulphur, chlorine and some anthropogenic metals to the Swedish west coast

Abstract Deposition measurements were performed during one month in autumn 1992 in a rural place on the west coast of Sweden. Airborne particle concentrations and deposition fluxes were measured simultaneously. Aerosol sampling was made with a dichotomous virtual impactor which size segregated the particles into fine ( By correlation analysis of the airborne elemental concentrations in fine and coarse particles it was possible to identify sources of the encountered aerosol. The K Cl, Ca Cl and Br Cl ratios in coarse particles were very close to those in sea water, suggesting a predominantly marine source of coarse particle Cl, K, Ca, and Br. The highest correlations were obtained for coarse particle Br vs Cl (0.99) and for coarse particle K vs Ca (0.98). The Br, Pb ratio in fine particles, approaching the “ethyl ratio” in fresh car exhaust, indicated that traffic was the dominant source of the fine particle Br and Pb. The positive correlations between most of the metals in fine particles indicated long distance transport from industrial source regions in Europe. The measured dry and wet deposition fluxes are reported for S, Cl, V, Mn, Fe, Ni, Cu, Zn and Pb, and estimates of annual total deposition at the measurement site are given and compared with reference data. The general feature is that fluxes are smaller in the northeast part of the North Sea compared to the southern part. Average dry deposition velocities obtained in the present study are compared with reference data and also with the elemental coarse fine particle ratios. These ratios give a rough estimate of what deposition rate to expect. The fine particle elements having coarse fine ratios less than one (V, Ni, Zn, Pb and S) have lower dry deposition velocities than coarse particle elements (Mn, Fe, Cu, Cl).

The Elspeetsche Veld experiment on surface exchange of trace gases: Summary of results

A three-year experiment for the determination of deposition fluxes on heathland was conducted at the Elspeetsche Veld involving several research groups. Micro-meteorological measurements of SO 2, NH 3 and NO 2 were made using different techniques. Furthermore, throughfall and bulk precipitation fluxes of SO 4 2−, NH 4 + and NO 3 − were also measured. From these measurements, deposition parameters were derived to yield a generalized description of the surface exchange of these trace gases, including possible interactions. For SO 2, generally low surface resistances were found; the annual average dry deposition velocity ranged from 0.8 to 1.0 cm s −1. The annual flux of SO 2 was estimated as 250 mol ha −1 yr −1. For NH 3 also, low R c values were observed, yielding annual average V d of 0.8 cm s −1. The annual flux of NH 3 was estimated as 850 mol ha −1 yr −1. Under the environmental conditions prevailing in the Netherlands, co-deposition between SO 2 and NH 3 was estimated to be irrelevant. Surface wetness was found to be the dominating factor influencing dry deposition of the two gases. R c values for NO 2 stomatal behaviour, V d for this gas ranged from 0.1 to 0.4 cm s −1. Fluxes measured with the throughfall method are compared with fluxes derived using micro-meteorological methods. The yearly average net throughfall flux for SO 4 and the dry deposition flux (SO 2 and SO 4 particles) amounted 500 and 350 mol ha −1 yr −1, respectively. For NH 4 this was 1180 and 930 mol ha −1 yr −1, respectively. The correlation between the two on a monthly basis is significant ( r=0.50 for SO 4 and r=0.52 for NH 4, n = 12, p<0.05).

Monitoring the dry deposition of SO2 in the Netherlands: Results for grassland and heather vegetation

Abstract An automated system based on the micrometeorological gradient technique has been developed to measure the dry deposition of SO 2 on a routine basis. Measurements were made at two locations in the Netherlands. From these results dry deposition fluxes, dry deposition velocities and surface resistances for a heathland and for an agricultural grassland site were estimated using a selected set of data and a calculation procedure based on micrometeorological considerations. An extensive analysis was made to determine uncertainties in the resulting deposition parameters. From this analysis it has been concluded that the uncertainty in these parameters is almost completely determined by the random errors in measured concentrations. The meteorological surface exchange parameters can be estimated sufficiently accurately ( −1 were calculated for wet and dry conditions, respectively. At the heathland site, a similar distinct difference between R c values for wet and dry conditions was found. These values are 20(±21) and 70(±90) s m −1 , respectively. The yearly average dry deposition flux for SO 2 at the grassland site amounts to 585(±330) mol ha −1 yr −1 , while at the heathland site the yearly average flux was 300(±270) mol ha −1 yr −1 . The yearly average dry deposition velocity at 4 m height was 1.2(±0.3) cm s −1 at the grassland site and 0.8(±0.4) cm s −1 at the heathland site.

Eddy Correlation Measurements of the Dry Deposition of Particles in Wintertime

Abstract Eddy correlation measurements of the vertical fluxes of particles, momentum, heat and water vapor, were conducted over a partially snow covered field in central Pennsylvania during December 1985. The PMS ASASP-300 and CSASP-100-HV optical counters were used as sensors to measure particle-number fluxes. Overall, average dry deposition velocities for 28 half-hour runs were found to be 0.034 ± 0.014 and 0.021 ± 0.005 cm s−1 for particles in two size ranges, 0.15–30 and 0.5–1.0 μm, respectively. The average deposition velocity was close to results from prior wind-tunnel and theoretical investigations. These results were also comparable with those reported by other authors over grass. Relatively large sampling rates reduced the effects of counting noise on deposition measurements of 0.5–;1.0 μm particles. Small correlation coefficients between vertical velocity and the particle concentration were found even after corrections for the effects of counting noise. The normalized average surface deposition ...

Atmospheric transport and deposition of trace elements onto the Greenland Ice Sheet

Airborne particles of diameter > 0.4 μm reaching Dye 3, Greenland during April–May 1983 were highly variable in size and concentration from day to day. Five-day backward air mass trajectories suggest the importance of long-range transport from more northerly latitudes on days with high concentrations; particle sizes were larger on these days. Lower concentrations and smaller particle sizes were associated with transport from the south. It is inferred that Dye 3 may receive material emitted from Eurasian sources and transported over the Pole, similar to inferences for more northern Arctic sites. Elemental analysis of individual particles showed an abundance of crustal material, with many particles also containing sulfur. Bulk chemical analyses of airborne particles and fresh snow, collected during three snowstorms where ice nucleation dominated, provided data which were used to estimate mass-basis scavenging ratios. Average scavenging ratios were in the range ~1000–2000 for the crustal elements Al, Fe, K, Mg, Mn, and Na. Similar values were observed for Cd, Cu and NO 3 −. The corresponding ratios for Pb and SO 4 2− averaged less than 200. These ratios were used with precipitation rate data to estimate wet deposition velocities in the order of ~2 cm s −1 for the first nine species, and ~0.2 cm s −1 for Pb and SO 4 2−. Comparing fresh and older surface snow concentrations gave an average dry deposition velocity of roughly 0.2 cm s −1 for the crustal elements, with the small fraction of large particles (~5–10 μm) dominating deposition; much smaller values were associated with the remaining species. When used with other data in the literature, the results of this study suggest that total deposition velocities of Pb and SO 4 2− may be as small as 0.05 cm s −1 in relatively dry regions of the Arctic.

An evaluation of the geographical variation of the characteristic sulfur wet fallout scale

Measured data of sulfur in air and in precipitation from 13 stations scattered over mainly southern Sweden are used, together with a detailed sulfur source inventory for Sweden and a simple model, to determine the average scale of the wet fallout of sulfur. The model discriminates between sources outside the average precipitation area that affects a receptor point and sources within that area. The latter type of sources are specified in great detail with respect to strength and location, while the former type of sources are treated collectively. The model explicitly accounts for the horizontal convergence of flow in precipitation areas. The result of the analysis is that the characteristic scale of the wet fallout, expressed in terms of the parameter κ, defined as the quotient between deposition per area and time and vertically integrated concentration per area unit varies significantly over Sweden : for most of the country values of κ in the range 10 −4−2.10 −4 s −1 are found (corresponding to 2 3 fallout within a distance of 50–100 km from the source), while for a strip on the west coast, not more than 100km wide, k ≤ 2.10 −5 s −1 . This result is in agreement with results from local studies. Based on these parameter values and with an average dry deposition velocity ν g = 8.10 −3 ms −1 an overall sulfur budget for Sweden is derived, showing that ca. 70% of the deposition over Sweden is due to sources outside the country itself.