Wet sulfate and nitrate deposition patterns in eastern North America (original) (raw)
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Wet and dry deposition of sulphates and nitrates in Eastern Canada: 1979?1982
Water, Air, and Soil Pollution, 1986
Daily air and precipitation chemistry observations at six rural locations in eastern Canada were analyzed to obtain wet and dry deposition. Dry deposition was calculated from air concentrations using deposition velocities originating from a recent literature review and synthesis exercise involving land use types. Total annual deposition ranges for S0~ from lO to 86 mmol m-2 and for NO~ excluding N02 contributions to dry deposition from 13 to 62 mmol m-2. Dry deposition accounts for an estimated 22 and 21% of the total SO~ and N0~ deposition, respectively. For N0~, this fraction increases to 30% if N02 concentration to dry deposition is included. There is a marked seasonal variation in total SO~ deposition but not in that of NO~. Both wet and dry deposition are episodic. 20% of daily events deliver between 47 and 70% of the deposition. i.
Tellus B, 1984
Observations are presented of the mean annual concentration and deposition of H +, SO,, NO; and NH: ions in precipitation in North America during 1980, the first year that a reasonably compatible merger of U S and Canadian federal network data was possible. The maximum concentration and wet deposition of Ht, SO; and NO, occurred in-and south of-the great lakes region near maximum anthropogenic emissions of sulphur and nitrogen oxides. The NH: maximum, however, was located in the north central US where American livestock feedlots are concentrated. Peak H* concentrations were 6&80 pmole I-'. In the region of maximum emissions, 1980 observations of H i , SO; and NO; wet deposition are within 25% of the 5-year mean for 1977-198 I. The respective fraction of anthropogenic sulphur and nitrogen oxides released in eastern North America that are wet deposited in the same area is 24 6 and 25 k 6%. On a smaller scale, in the high sulphur and nitrogen oxide emissions area of the northeastern US. the deposition was 13 and 18% of emissions, respectively. Trends in emissions as well as in SO; and NO; concentrations in precipitation support the conclusion that a real increase in acidity of precipitation of 30-37 pmol I-' has occurred in the southeastern US since 1955156
Observed and modeled trend of sulfate and nitrate in precipitation in eastern North America
Atmospheric Environment (1967), 1989
The trend of annual average sulfate and nitrate ion concentrations in precipitation at 17 stations in eastern North America over 7 years 1979-1985 is estimated and compared with a modeled trend. The observed concentrations fluctuate from year-to-year about a mean value with a standard deviation of 12.7% on average. The average slope of a linear regression line at the 17 stations is-2.8%a-' for sulfate and-0.4% a-' for nitrate. The modeled trend at these stations, which assumes constant meteorology but a year-to-year varying emission inventory, is-2.4% a-l for sulfate and-0.9% a-l for nitrate.
A method for evaluation of acidic sulfate and nitrate in precipitation
Water, Air, and Soil Pollution, 1989
A simple method is presented and used to estimate the portions of SO 2 -and NO3-that contribute to the strong acidity in weekly precipitation samples collected at three NADP sites in the eastern United States. The method assumes that, in general, the difference between SO ] -and NH 2 represents acidic sulfate and the difference between NO3-and soil-derived materials (the sum of Ca 2 +, Mg 2 +, and K รท ) represents acidic nitrate. Acidic sulfate and nitrate are considered to be the predominant source of H + (determined from laboratory pH) in the weekly precipitation samples. Most of the acidity for all three sites was attributed to acidic sulfate. The highest fraction of acidic SO 2-to H + wet deposition values was for the east-central Tennessee site (0.95) and the northeastern Illinois site (0.90), and the lowest fraction occurred at the central Pennsylvania site (0.75). The Tennessee site had the greatest acidic fraction of sulfate (0.84) and the Pennsylvania site had the greatest acidic fraction of nitrate (0.59).
The Incursion of Acid Deposition into Western North America
Environmental Conservation, 1983
Acidification processes in western North America will probably increase in scope and visibility over the foreseeable future. Localized acidification seems more probable for the next few decades than does a generalized acidified deposition over the western States. At least part of current acid deposition downwind of urban areas is associated with automobile emissions. However, increases in coal combustion for power generation might be expected to increase sulphur dioxide concentrations, along with several related acidifying agents. Interactions of air pollutants with orographic precipitation and snowmelt may bring some areas to public attention much earlier than others, depending upon site-specific matters of climate, topography, soils, water-bodies, and biota. Lakes and streams on windward slopes facing large urban or industrial sources of sulphur and nitrogen oxides may be most seriously at risk.
Ten-year trends in sulphate, nitrate and hydrogen deposition in central Ontario
Atmospheric Environment (1967), 1988
The decrease in emissions of SO2 in eastern North America in the past decade was strongly correlated with a decrease in bulk deposition rates and concentrations of SO, 2-and H + in precipitation in central Ontario. Nitrate emissions, deposition and concentration have not changed significantly over the same period.
Tellus B, 1988
The relative importance of dry and wet deposition of sulphate and nitrate over southeastern Canada is examined using daily air and precipitation chemistry observations made at 6 rural stations of the Air and Precipitation Monitoring Network (APN) during the period 1979 to 1982. Dry deposition was calculated from these air concentrations using deposition velocity information on land-use types, on atmospheric wind speed and stability and on dry deposition rates from over 80 published studies. Despite the large uncertainty in dry deposition estimates which is associated with the complexity of the process, valuable conclusions emerge. I t is estimated that total annual deposition varies between 10 to 86 mmole m-' and 13 to 62 mmole m-? for SO: and NO,, respectively. To eastern Canada 22'16 and 30y0 of the total SO; and NO; deposition is dry deposited. respectively. Depending on location. the contribution of SO, to the dry deposition of sulphur ranges from 37O, to 78';. It tends to decrease with increasing distance from major sources. In eastern Canada, the best estimate of the fraction of the total dry deposition of nitrogen contributed by NOz and HNO, is in the range 504, to 60"; and 31 O 0 to 45",, respectively, depending on location. The uncertainty in the NOI estimate is large. approaching a factor of 3.5. Even if PAN dry deposition velocities are equal to that of NO? (they are expected to be lower). the contribution of PAN to total nitrate deposition is negligibly small. Both dry and wet deposition are episodic in nature. I t is estimated that the top-20", deposition events yield 47'" to 70", of the total deposition.