Trend analysis of weekly acid rain data, 1978-83

Water-Resources Investigations Report 85-4211

and ORCID iD



There are 19 stations in the National Atmospheric Deposition Program which operated over the period 1978-83 and were subsequently incorporated into the National Trends Network in 1983. The precipitation chemistry data for these stations for this period were analyzed for trend, spatial correlation, seasonality, and relationship to precipitation volume. The intent of the analysis was to provide insights on the sources of variation in precipitation chemistry and to attempt to ascertain what statistical procedures may be most useful for ongoing analysis of the National Trends Network data. The Seasonal Kendall test was used for detection of trends in raw concentrations of dissolved constituents, pH and specific conductance, and residuals of these parameters from regression analysis. Forty-one percent of the trends detected in the raw concentrations were downtrends, 4 percent were uptrends, and 55 percent showed no trends at a = 0.2. At a more restrictive significance level of a = 0.05, 24 percent of the trends detected were downtrends, 2 percent were uptrends, and 74 percent showed no trends. The two constituents of greatest interest in terms of human generated emissions and environmental effects, sulfate and nitrate, showed only downtrends, and sulfate showed the largest decreases in concentration per year of all the ions tested.

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Publication type:
Publication Subtype:
USGS Numbered Series
Trend analysis of weekly acid rain data, 1978-83
Series title:
Water-Resources Investigations Report
Series number:
Year Published:
U.S. Geological Survey
Publisher location:
Austin, TX
Contributing office(s):
Texas Water Science Center
iv, 64 p.
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