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Acid Deposition Monitoring Data

Preparation of Data Summaries

When the analytical laboratory receives an acid deposition sample, the weekly check sheet is copied and sent to the site supervisor for review. The check sheet contains the site operator field observations and information relating to time and precipitation events (cycles of hyetometer cover) since last site visit, sample condition, operator comments.

This review is to determine if the sample is contaminated and, therefore, should not be used in the calculation of average concentrations and deposition rates. Conditions such as finding the wet-side bucket uncovered during a non-precipitation event or deterioration of the polyethylene cover on the hyetometer cover gaskets, are sufficient reasons to consider invalidation of the sample. In other instances, the engineer must use engineering judgement to decide if the sample is contaminated and invalid. This judgement is based on information from the check sheets, operator comments, and additional knowledge concerning the site, its equipment and operation.

After review, individual sample results are entered into a computer where all of the data is sorted and the necessary calculations are performed. Prior to beginning the report generation procedures, the database is reviewed again by the engineering staff. Programs have been prepared to create a combined results database and to select results from the correct calendar year. The information is converted into a spreadsheet format.

Equation for calculating weighted averages:

Equation for calculating weighted averages from precipitation and concentration

Averages of pH, conductivity, anion concentration, and cation concentration are calculated on a precipitation weighted basis. Individual sample results are used to calculate quarterly and annual averages. Precipitation totals are assigned to the quarter in which the sample was collected. pH values are converted to hydrogen ion concentrations before averaging and then reconverted to pH.

Once the concentrations of anions and cations are determined, the depositions can be calculated using the following formula:

Rainfall in x 2.54 cm/in=rainfall cm

Rainfall cm. x 10,000 cm2/m2=volume cm3/m2

rem - volume of rainwater that would fall over a square meter

Volume cm3 /1000 cm3/liter=volume in liters

Concentration PPM=mg/l

Concentration mg/l x volume in liters=deposition mg/m2

I hectare=10,000 m2

(deposition mg/m2) x (10,000 m2/h) x (10-6kg/mg)

deposition mg/m2 x 10-2=deposition kg/h









Total deposition amounts (mg/m2) are then calculated for each quarter and the whole year. Where the total measured precipitation was not analyzed for ionic concentration, the deposition values are scaled up to account for the unanalyzed rainfall. The concentration of the unanalyzed precipitation is assumed to equal to the average concentration of the analyzed precipitation. The following rules also apply.

QUARTER. At least 75% of the precipitation in a quarter must have been analyzed for the deposition to be scaled up. If not, no deposition total is reported for the quarter.

ANNUAL. At least 75% of the total annual precipitation must have been analyzed; and at least 50% of the precipitation in each quarter must have been analyzed. If both of the criteria are met, an annual deposition rate is calculated.

The precipitation amounts are generally obtained from tipping bucket rain gauges collocated at the hyetometer. The data are either recorded on-site, or telemetered to our central computer. In instances of incomplete precipitation data, data from National Weather Service (NWS) observers are substituted. The NWS site which best represents the precipitation condition at the hyetometer sites is used. We extend our thanks to the Forecasting Section, Bureau of Impact Assessment and Meteorology, for their assistance in selecting these sites and the use of their data files.

More about Acid Deposition Monitoring Data :

  • 2007 Acid Deposition Executive Summary - New York State's Acid Rain Monitoring Network collects and analyzes precipitation parameters (pH, Sulfate, Nitrate, Calcium, Magnesium, etc) to assess the effectiveness of sulfur control policy and other strategies aimed at reducing the effects of acid rain
  • Air Monitoring Site Trends (1987-2007) - Air Monitoring Site Acid Deposition Trends by monitoring stations from 1987 to 2007