ABSTRACT
The primary objective of this study was to quantify the effects of residential fertilizer use on groundwater quality, which have not been well defined by field-scale investigations. Concentrations of constituents associated with fertilizer use were monitored in shallow groundwater in residential areas in Orange and Seminole Counties of Central Florida. The study area is within the Wekiva River basin, a river that is primarily spring fed. Sampling locations were selected to represent land in residential use for more than 5 yr and to avoid septic systems and areas recently used for citrus production. Twenty-six wells were installed in the surficial aquifer, screened within approximately 3 m of the water table, which was encountered between 0.3 and 11.5 m below land surface. Of these wells, 24 were in residential areas, scattered over an area of about 2600 ha, and two were in nearby undeveloped areas. Samples were collected four times between October 2008 and July 2009. Concentrations of nitrate plus nitrite nitrogen (NO-N) averaged 2.0 ± 0.2 mg L in the residential areas and were significantly higher ( < 0.01) than observed in undeveloped areas (0.3 ± 0.1 mg L). Groundwater was also analyzed for stable isotopes of nitrogen and oxygen and has been analyzed for bacteria (by others), which corroborated that these wells were not affected by human or animal waste. Levels of NO-N in the residential areas are primarily attributed to residential fertilizer use, considering the control for and exclusion of other plausible sources.
