--> Abstract: Effects of Agriculture Chemicals on Natural Geochemistry of Shallow Groundwater, Delmarva Peninsula, Delaware, Maryland, and Virginia, by P. A. Hamilton and J. M. Denver; #90995 (1993).
[First Hit]

Datapages, Inc.Print this page

HAMILTON, PIXIE A., U.S. Geological Survey, Richmond, VA, and JUDITH M. DENVER, U.S. Geological Survey, Dover, DE

ABSTRACT: Effects of Agriculture Chemicals on Natural Geochemistry of Shallow Groundwater, Delmarva Peninsula, Delaware, Maryland, and Previous HitVirginiaNext Hit

Agriculture practices affect water chemistry in the water-table aquifer throughout the Delmarva Peninsula. The Delmarva Peninsula, located in the Atlantic coastal plain physiographic province, includes most of Delaware and the entire eastern shore of Maryland and Previous HitVirginiaNext Hit. Land area is 6050 sq mi, of which about 48% is agricultural. Groundwater in the water-table aquifer is susceptible to nonpoint sources of contamination because of (1) the prevalent use of inorganic fertilizers, manure, and lime, (2) the shallow depths to the water table (generally less than 20 ft), and (3) the high permeability of the soil.

Groundwater unaffected by agriculture practices generally is characterized by low specific conductance (median value of 63 microsiemens/cm at 25 degrees C) because the aquifer is composed mainly of insoluble quartz sand with minor amounts of feldspar and clay minerals. Most of the major dissolved constituents are derived from rainfall and weathering of feldspars. Regional geochemical patterns are evident and relate to lithology and groundwater-flow patterns. Calcium bicarbonate- and sodium bicarbonate-type waters are common in the interior of the peninsula,

sodium chloride type-water is common in coastal and tidal areas, and calcium sulfate chloride-type water is common in areas underlain by estuarine deposits along the margins of the peninsula and in forested wetlands.

Groundwater affected by agricultural practices generally is a calcium magnesium nitrate type, with a median specific conductance of 183 micro S/cm at 25 degrees C. Calcium and magnesium are from agricultural lime and the nitrate is from fertilizer and poultry manure. Agriculture affects groundwater composition throughout the peninsula, except in areas of poorly drained and relatively impermeable clay-silt sediments that characterized by high exchange capacities and limited zones of oxidation.

AAPG Search and Discovery Article #90995©1993 AAPG Eastern Section Meeting, Williamsburg, Previous HitVirginiaTop, September 19-21, 1993.