Observed and modeled trend of sulfate and nitrate in precipitation in eastern North America (original) (raw)
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Wet sulfate and nitrate deposition patterns in eastern North America
Atmospheric Environment (1967), 1988
A&met-Four year (1982-1985) averaged acid deposition (sulfate and nitrate ion) data obtained at 77 stations of the Acid Deposition System in Eastern North America (ENA) are analyzed for seasonal and spatial variations. Average sulfate concentrations over most of ENA range from 1.5-3 mg E'-'. Highest sulfate depositions (> 35 kg ha-' y-') occur over west Pennsylvania, the Virginias, east Michigan, and southern Ontario between Lakes Huron and Erie. Sulfate isopleths generally stretch along a SW-NE axis. In the northeast quadrant of ENA, 65-70% of the annual sulfate depositions occur in the April-September half year; some regions in southern Canada experience as much as 75% in that period. Average nitrate concentrations range from 1-2 mgl-' throughout much of ENA. Peak nitrate depositions (>20 kg ha-' y-l) fall between Lakes Michigan and Ontario; 15 kg ha-'yei or more coyer most of the Midwest, New York, New England and south Ontario. Nitrate depositions are more evenfy distributed throughout the year, with 5565% occurring in the April-September half year. The average annual molar ratio of SOi-to NO; varies from 0.8-1.5 over ENA. The ratio is highest at south-central mceptom and lower at northern latitudes. Implications of these findings on strategies to'mitigate acid deposition are discussed.
Water, Air, & Soil Pollution: Focus, 2007
Data from the National Atmospheric Deposition Program/National Trends Network (NADP/ NTN) indicate significant changes have occurred in precipitation chemistry and the chemical climate in the United States (US). A Seasonal Kendall Trend (SKT) analysis shows statistically significant increases in precipitation ammonium concentrations at 64% of 159 continental US NADP/NTN sites evaluated from Winter 1985 to Fall 2004 (Dec. 1984-Nov. 2004). Sulfate decreases were widespread, with an SKT analysis indicating statistically significant decreases at 89% of sites evaluated. Ratios of chemical equivalent concentrations of ammonium to sulfate in precipitation have risen to the extent that ammonium now exceeds sulfate over more than half of the continental U.S. on a precipitation-weightedmean annual basis. These trends in the concentrations of ammonium, sulfate, and other species have been accompanied by significant decreases in the frequency of acidic precipitation (pH<5.0) in the last decade.
The longest continuous precipitation monitoring operation in Florida has occurred at a site located on the University of Central Florida (UCF) campus located near Orlando from 1977 to the present. One site at the Kennedy Space Center and four other sites in Florida and three sites in Georgia have operated continuously since 1984 or earlier. Major ion concentrations including acidity vary considerably among sites and the UCF site exhibits higher acidity and nitrate concentrations than any other site. In general concentrations decrease as site location is moved from north to south except where site proximity to the ocean is a dominant factor. Nitrate has trended higher during the sixteen year period and acidity at UCF trended lower early in the sixteen year period but has trended toward higher concentrations when recent data are evaluated. When NOx and SO2 emissions from eastern and southeastern states and precipitation composition data for the period 1978-1988 are evaluated, there is no strong indication of relationships between emission and concentration or emission and deposition.
2006
Analysis of weather patterns on a synoptic or regional scale is the common direction of study in air pollution meteorology with few studies analyzing weather conditions proximal to collection sites. A study that focuses on local weather conditions may lead to better understanding and more accurate forecasting of rain water chemistry than synoptic or regional scale studies. The objective of this project is to determine the relationship between local weather patterns and rain water chemistry in Wilmington, NC. Daily and hourly meteorological data (average temperature, relative humidity, wind speed and direction, and maximum and minimum temperatures) were collected for the 48 hour period prior to each rain event. In addition, the nitrate and sulfate concentrations were obtained from the Marine and Atmospheric Chemistry Research Laboratory (MACRL) at UNCW. Data analysis of local weather conditions 48 hours prior to 24 storm events, including review of descriptive statistics, graphical a...
Journal of Geophysical Research, 2004
1] Concentrations of K, Sc, Mn, Fe, Zn, As, Se, Sb, Hg, and Pb were determined in quarterly composites of daily aerosol samples collected at Mayville, and 530 km downwind at Whiteface Mountain (1.5 km altitude), New York, for $20 years. SO 4 concentrations [SO 4 ] were determined in individual daily samples. Continuous hourly SO 2 data are also available for much of the period. [SO 4 ] at Mayville were twice that at Whiteface Mountain, and total S (S as SO 2 + SO 4 ) burden was fourfold higher at Mayville. From 1979 through 2002, [SO 4 ] decreased by 59% at Whiteface Mountain, and at Mayville the decrease was 30% from 1984 to 2002. From 1979 to 2002, SO 2 emissions in eight states upwind of and contiguous with New York State (Ohio, Pennsylvania, Indiana, Illinois, Wisconsin, Kentucky, West Virginia, and Ontario, Canada) decreased by 49%. A linear relationship was observed between atmospheric [SO 4 ] and [total S] burden at the two sites with the cumulative SO 2 emissions. These observations suggest that any further reductions in SO 2 emissions would result in a proportional decrease in [SO 4 ] and [total S] across New York State and possibly across the northeastern United States. The data at Whiteface Mountain suggest that beginning in 1997, the decrease in [SO 4 ] and [total S], relative to SO 2 emissions, may be faster than the earlier period. Like [SO 4 ] and [total S], the trace element concentrations were twofold to fivefold higher at Mayville than at Whiteface Mountain. The concentrations at both sites showed an unmistakable decrease over time. The largest decreases were observed for Hg (16%/year at Whiteface Mountain and 10%/year at Mayville) and Pb (14%/year at Whiteface Mountain and 10%/year at Mayville). The remaining elements (except Sb), including the crustal elements K, Mn, Sc, and Fe, showed a decreases of 3-5%/year. Trends for Sb at Whiteface Mountain and for Mn at Mayville could not be accurately discerned, apparently due to some nearby emissions. Apparently, the reductions in the emissions of SO 2 and particulate matter have also resulted in the decrease of atmospheric burden of trace elements and an improvement in air quality.
A 10-year spatial and temporal trend of sulfate across the United States
Journal of Geophysical Research, 2002
1] Legislative and regulatory mandates have resulted in reduced sulfur dioxide (SO 2 ) emissions in both the eastern and western United States with anticipation that concurrent levels of ambient SO 2 , SO 4 2À , and rainwater acidity would decrease. This paper examines spatial and temporal trends in ambient SO 4 2À concentration from 1988 to 1999, SO 2 emissions from 1990 to 1999, and the relationship between these two variables. The SO 4 2À concentration data came from combining data from the Interagency Monitoring of Protected Visual Environments (IMPROVE) and the Clean Air Status and Trends Network (CASTNet). Over 70 sites spread across the continental United States are considered in this analysis. From a spatial perspective, the 90th percentile summer sulfate concentrations are highest along the Ohio River Valley and in central Tennessee where the emission density of SO 2 is greatest. These concentrations are a factor of 2 greater than the Northeast, northern Michigan, and coastal areas of the Southeast and about a factor of 15 greater than the central western United States. In the East, the largest SO 4 2À decreases in the 80th percentile concentrations occurred north of the Ohio River Valley, while most monitoring sites south of Kentucky and Virginia showed increasing and decreasing trends that were not statistically significant. Big Bend National Park, Texas, Cranberry, North Carolina, and Lassen Volcanic National Park, California, are the only areas that show a statistically significant increase in SO 4 2À mass concentrations. The 1990-1999 annual 80th percentile SO 4 2À time series were compared to the annual SO 2 emissions over four broad United States regions. Each region had a unique time series pattern with the SO 4 2À concentrations and SO 2 emissions closely tracking each other over the 10-year period. Both the SO 4 2À and SO 2 emissions decreased in the Northeast (28%) and the West (15%), while there was little change in the Southeast and a 15% increase over Texas, New Mexico, and Colorado.
Short-term trends in sulfate deposition at selected bulk precipitation stations in New York
Atmospheric Environment (1967)
Trends in rainfall-adjusted sulfate concentration were assessed for 5-yr subrecords of the 14.5-17 yr of monthly bulk-deposition data from five stations in New York by using the seasonal Kendall test. For the 5-yr subrecord from 19'78 to 1982, the trends for the bulk deposition were similar to those for weekly wet-only deposition for adjacent stations of the National Atmospheric Deposition Program (NADP).
Atmospheric Environment, 2010
This paper compares spatial and seasonal variations and temporal trends in modeled and measured concentrations of sulfur and nitrogen compounds in wet and dry deposition over an 18-year period (1988e2005) over a portion of the northeastern United States. Substantial emissions reduction programs occurred over this time period, including Title IV of the Clean Air Act Amendments of 1990 which primarily resulted in large decreases in sulfur dioxide (SO 2 ) emissions by 1995, and nitrogen oxide (NO x ) trading programs which resulted in large decreases in warm season NO x emissions by 2004. Additionally, NO x emissions from mobile sources declined more gradually over this period. The results presented here illustrate the use of both operational and dynamic model evaluation and suggest that the modeling system largely captures the seasonal and long-term changes in sulfur compounds. The modeling system generally captures the long-term trends in nitrogen compounds, but does not reproduce the average seasonal variation or spatial patterns in nitrate.