Evaluating Nitrate Management in the Volusia Blue Springshed

Abstract

This investigation evaluated five hypothetical scenarios relating nitrate sources in the recharge of the Volusia Blue Spring to eutrophication in the St. Johns River. In the Volusia Blue recharge area of Florida, decades of nitrate loadings have impacted the quality of springwater discharged from the confined Floridan aquifer. Simulators and field observations were used to develop and define a procedure for the first time by which local and Florida state agencies can better manage nitrate pollution. The simulations were based on population growth projections and nitrogen loads from treated wastewater discharges, septic tanks, and fertilized areas. A one-tailed t-test comparing observed with simulated nitrate values in spring discharge indicates that there is insufficient evidence of discrepancies between observed and simulated results. Results from the simulation of five nitrate management scenarios were used to estimate probable construction costs that were compared with mg L−1 of nitrate removed. Constructed wetlands and targeted septic tank removal were the two most cost-effective nitrate management approaches. However, septic tank removal resulted in the greatest benefit with a 36% nitrate decrease in a 39-year projection of springwater quality.