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2007 Acid Deposition Executive Summary

New York State Acid Rain

Issued May 2009


New York State's Acid Rain Monitoring Network collects and analyzes precipitation parameters (including pH, Sulfate, Nitrate, Calcium and Magnesium) to assess the effectiveness of sulfur control policy and other strategies aimed at reducing the effects of acid rain. As of 2007, our monitoring network consisted of 20 sites located throughout the state in both rural and urban areas. Monitoring results are available for the years 1987 to 2007.

The Clean Air Act Amendments of 1990 contained important provisions to control acid deposition by reducing the amounts of SO2 and NOx emitted to the air. About 2000 of the highest SO2 and NOx emitting power plants were designated as Phase I and Phase II facilities. Nationally, reductions of SO2 from these plants were expected to be 3.5 million tons (mmtons) by 1995 and 10 million tons by the year 2010. The 1995 reduction goals for SO2 were achieved. There has also been a 42% reduction in NOx for the Phase 1 power plants since 1996. The power plants affected by 1990 CAAA, many of which are upwind of New York State, are considered to be the worst polluters and, had emissions in tons as follows:

EPA Graph showing acid rain emissions by year
Source: USEPA Quick Facts & Trends

The above chart shows both SO2 and NOx declining even though heat input was increasing for the nation's Titles IV and V power plants. The SO2 decline in emissions also resulted in a decline in acid deposition sulfates. NOx emissions have not declined as rapidly as SO2. Starting in 2000, additional utility units were affected by more stringent SO2 and NOx limits. For example, since 1995 the amount of NOx emitted has been reduced by 0.4 or 0.86 lbs/mmBtu, depending on the boiler type.

Continuing acid deposition monitoring will determine whether projected emission reductions will yield a corresponding decline in acid deposition.

Monitoring Network

The New York State Acid Deposition Monitoring Network was designed in 1985 in response to the mandate of the "State Acid Deposition Control Act" (SADCA). Twenty sites are presently monitoring acid deposition. The objectives of the network are:

  • Provide consistent, quality assured, long-term acid deposition data.
  • Measure acid deposition in sensitive receptor areas.
  • Measure acid deposition in urban and upwind areas.
  • Use these data to perform geographic and temporal analyses of acid deposition, its precursors, and its effects.
  • Track acid deposition precursor emissions reduction effectiveness.

The network is composed of three classes of monitoring sites, which differ by the amount and kind of instrumentation used. They are designated as "Type 3," "Type 2," and "Type 1."

Type 3 sites have two types of instrumentation. The first is a tipping bucket rain/snow gauge or a Belfort High Capacity gauge to measure the amount of precipitation. The output signal is connected to either a recorder or a telemetry unit. The second device is a "Viking Hyetometer" which is a bucket type collector designed to collect samples under wet or dry conditions. Wet deposition samples are gathered in the lined buckets when precipitation is occurring. In addition to the devices operated at Type 3 sites, Type 2 sites incorporate continuous monitoring instrumentation to measure the ambient concentration of selected components. These instruments are connected via telemetry to a central computer. Type 1 sites have instrumentation used at Type 2 sites and equipment to measure wind speed and direction, and calculate horizontal sigma (wind direction variability).

Table I contains a summary of the sites in the 2007 Acid Rain Monitoring Network. Following the table is a map of New York State showing the approximate location of each of the sites.

Table I - 2007 Atmospheric Deposition Monitoring Network
Site Name County Official
3720-01 Altmar Oswego 10/24/89 no no no
5565-03 Belleayre Mt. Ulster 01/01/87 yes yes, low level no
1401-18 Buffalo Erie 01/01/87 yes yes yes
2655-01 Camp Georgetown Madison 01/01/87 2 yes no
3353-09 East Syracuse Onondaga 03/05/91 1 yes no
2950-10 Eisenhower Park Nassau 01/01/87 1 yes yes
0701-05 Elmira Chemung 03/31/87 1 yes no
4153-04 Grafton Lakes Rensselaer 11/27/01 1 yes, low level no
0101-33 Loudonville Albany 07/02/87 1 yes no
3951-01 Mt. Ninham Putnam 01/01/87 1 yes, low level no
3102-25 Niagara Falls Niagara 01/01/87 1 yes no
2167-03 Nicks Lk. Campground Herkimer 02/03/87 1 yes, low level no
7094-06 NY Bot. Garden Richmond 04/11/01 1 yes yes
1655-01 Paul Smith's College Franklin 04/20/04 1 yes, low level no
2050-01 Piseco Lake Hamilton 08/09/88 2 yes, low level no
2701-22 Rochester Monroe 01/01/87 2 yes no
4458-05 Wanakena Ranger Sta. St.Lawrence 01/01/87 no no no
0675-01 Westfield Chautauqua 01/01/87 yes yes, low level no
5902-04 White Plains Westchester 01/01/87 yes no no
1567-04 Whiteface Mt. Essex 10/03/89 yes yes, low level no

A map of the 2007 Network follows.

NYS map shows acid depostition monitoring sites

Concentration and Deposition

Laboratory analysis provides the concentration of each of the data parameters in parts per million equivalent to milligrams per liter (mg/l). Concentration multiplied by the volume of precipitation per square meter equals deposition (mg/m2) which is then converted to kilograms per hectare (kg/ha).

The eight parameters selected for display are Hydrogen Ion Concentration as pH (H+), Sulfate Ion (SO4- -) Concentration, SO4- - Deposition, Nitrate Ion (NO3-) Concentration, NO3- Deposition, Ammonium Ion (NH4+) Concentration, NH4+ Deposition and Total Precipitation.

Trend graphs and tables for the eight selected parameters are provided for 1987-2007 for each of the monitoring sites in the Appendix. There are occasionally blanks in the concentration and deposition trend plots indicating that the rainfall deposition analysis criteria were not satisfied. That is, for various reasons the lab was unable to analyze at least 75% of the annual and 50% of the quarterly precipitation.

Data Trends

pH measurements for each site, with pink dot representing the average:
1987-2007 pH data, weighted by precipitation

Sulfate measurements for each site, with pink dot representing the average:
1987-2007 Sulfate (SO4) data, weighted by precipitation

Nitrate measurements for each site, with pink dot representing the average:
1987-2007 Nitrate (NO3) data, weighted by precipitation


Acid Rain data collected through 2007 and displayed both in the individual site trend charts (Appendix) and the Sulfate Data and Nitrate Data summary graphs above are continuing a "slightly" decreasing trend for both SO4 concentration and deposition. The concentration and deposition downward trend is not as evident for NO3- and NH4+. pH is a log value and any improvement would result in higher pH values. The pH Data graph above and trend charts in the Appendix show slight pH improvements. The trends in acid deposition data (Appendix) are similar to the emissions trends.

SO2 and NOx emissions reductions required by the 1990 CAAA have made progress in reducing acid rain emissions. However, in 2004 New York adopted even more aggressive regulations. Under the Acid Deposition Reduction Program (ADRP, 6 NYCRR Parts 237 and 238), fossil fuel-fired electric generators in New York State will be required to reduce NOx and SO2 emissions. Affected sources must reduce SO2 emissions to 50 percent below the levels allowed by Phase 2 of the federal acid rain program. The SO2 reductions will be implemented in two phases which start on January 1, 2005 and January 1, 2008. Beginning on October 1, 2004, affected sources must reduce NOx emissions during the non-ozone season (October - April) to a level that corresponds with the NOx reductions that will be achieved starting on May 1, 2003, through the implementation of 6 NYCRR Part 204, NOx Budget Trading Program, for the ozone season (May - September).

Only by the continued collection and analysis of acid deposition samples will it be possible to verify that improvements are occurring due to the reductions of SO2 and NOx legislated in the 1990 CAAA and ADRP.

Should you have comments or questions, you can contact us at:

New York State Department of Environmental Conservation Division of Air Resources
Bureau of Air Quality Surveillance
625 Broadway 3rd Floor
Albany, NY 12233-3256
Telephone 518-402-8508
Fax 518-402-8507
e-mail: DARWeb@gw.dec.state.ny.us


Trend Charts and Tables

The following tables and charts use Ionic Parts Per Million (ippm) weighted by precipitation for concentration which are equivalent to Milligrams Per Liter (mg/l) weighted by precipitation: