Hydrogeologic setting and potential for denitrification in ground water, coastal plain of southern Maryland

Water-Resources Investigations Report 2000-4051

Prepared in cooperation with the Maryland Department of the Environment and the Maryland Department of Natural Resources
and ORCID iD



The types and distribution of Coastal Plain sediments in the Patuxent River Basin may contribute to relatively low concentrations of nitrate (typically less than 1 milligram per liter) in stream base flow because of the chemical reduction of dissolved nitrate (denitrification) in ground water. Water chemistry data from synoptic stream base-flow surveys in the Patuxent River Basin show higher dissolved nitrate concentrations in the Piedmont than in the Coastal Plain section of the watershed. Stream base flow reflects closely the chemistry of ground water discharging from the surficial (unconfined) aquifer to the stream. Because land use in the sampled subbasins is virtually the same in each section, differences in the physical and geochemical characteristics of the surficial aquifer may explain the observed differences in water chemistry. One possible cause of lower nitrate concentrations in the Coastal Plain is denitrification within marine sediments that contain chemically reduced compounds. During denitrification, the oxygen atoms on the nitrate (N03-) molecule are transferred to a reduced compound and N gas is produced. Organic carbon and ferrous iron (Fe2+), derived from the dissolution of minerals such as pyrite (FeS2) and glauconite (an iron aluminosilicate clay), can act as reducing substrates; these reduced chemical species are common in the marine and estuarine deposits in Southern Maryland. The spatial distribution of geologic units and their lithology (sediment type) has been used to create a map of the potential for denitrification of ground water in the surficial aquifer of the Coastal Plain in Southern Maryland.

Study Area

Additional publication details

Publication type:
Publication Subtype:
USGS Numbered Series
Hydrogeologic setting and potential for denitrification in ground water, coastal plain of southern Maryland
Series title:
Water-Resources Investigations Report
Series number:
Year Published:
U.S. Geological Society
Publisher location:
Reston, VA
Contributing office(s):
Maryland, Delaware, and the District of Columbia Water Science Center
iv, 19 p.
United States
Online Only (Y/N):