Abstract

Occurrence of Nitrate in the Mississippi River Valley Alluvial Aquifer at a Site in Bolivar County, Mississippi

Author(s): Welch, H. ;  Coupe, R.;  Green, C.

Annually in the United States, about 12 million tons of nitrogen are applied as commercial fertilizer causing contamination of surface and groundwater resources. In the Mississippi Delta, large amounts of agricultural chemicals are applied to crops on an annual basis, but are rarely detected in groundwater. Previous studies have indicated that the shallow alluvial aquifer in the Delta is unaffected by anthropogenic activities at the surface because of an overlying impervious clay layer. However, model simulations have indicated that the alluvial aquifer is recharged by a small percentage (5%) of rainfall. In 2005, the U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program began a study in the Bogue Phalia basin to assess how environmental factors and agricultural practices affect the source and transport of agricultural chemicals. Two wells located in a cotton field (surveyed as very fine sandy loam and silty clay) in Bolivar County, Mississippi were sampled for inorganic compounds, nutrients, and field parameters from June 2006 to November 2008. Nitrate was detected at concentrations ranging from 7.2 to 13 mg/L in a shallow well screened near the water table from 27 to 32 feet, but was not detected in a deeper well screened from 70 to 120 feet located approximately one-quarter mile from the shallow well. In June 2008, depth interval sampling was conducted in test holes drilled adjacent to the shallow well to better define the occurrence of nitrate at five depths ranging from 32.5 to 60 feet–between the depths of the shallow and deep wells. Nitrate concentrations decreased with depth in the water column, and there were no detections below a depth of 36 feet. Data indicate that some nitrate is being transported through the unsaturated zone into the alluvial aquifer, but it is being converted fairly quickly into ammonia and nitrogen gas under strong, reducing conditions in the aquifer. The data imply that the aquifer may not be as invulnerable to anthropogenic activities as previously thought.







 

Technical Presentations

  • Delta Water Quality
  • Delta Water and Agriculture
  • Wetlands
  • Water Quality
  • Sediments
  • Non-Point
  • Management and Sustainability
  • Wood Treatment
  • Modeling
  • Soil and Water Treatment

Workshops

Responsible Site Design: Implementing Innovative Stormwater Management Strategies

The primary goal of the workshop is to create a dynamic learning experience that examines the role of stormwater management in the built environment. The workshop will focus on integrating ecologically sound water management approaches into site design. After the workshop, attendees will be familiar with the following concepts and technical issues:

  • Knowledge of the stormwater treatment chain
  • Knowledge of the impact of land use codes on stormwater management
  • Application of a design process that mitigates the effects of stormwater on-site
  • Knowledge of the relationship between land use codes and design for innovative stormwater management

Information

For information contact:
Jessie Schmidt
MWRRI
Box 9680
Mississippi State, MS 39762
662-325-3295
jschmidt@cfr.msstate.edu