Using Multiple Chemical Indicators to Assess Sources of Nitrate and Age of Groundwater in a Karstic Spring Basin

Abstract

Research Article| April 01, 2005 Using Multiple Chemical Indicators to Assess Sources of Nitrate and Age of Groundwater in a Karstic Spring Basin Brian Katz; Brian Katz 1U.S. Geological Survey, 2010 Levy Ave., Tallahassee, FL 32310 Search for other works by this author on: GSW Google Scholar Rick Copeland; Rick Copeland 2Florida Geological Survey, 903 W. Tennessee St., Tallahassee, FL 32304 Search for other works by this author on: GSW Google Scholar Tom Greenhalgh; Tom Greenhalgh 2Florida Geological Survey, 903 W. Tennessee St., Tallahassee, FL 32304 Search for other works by this author on: GSW Google Scholar Ron Ceryak; Ron Ceryak 3Suwannee River Water Management District, 9225 CR49, Live Oak, FL 32060 Search for other works by this author on: GSW Google Scholar Warren Zwanka Warren Zwanka 3Suwannee River Water Management District, 9225 CR49, Live Oak, FL 32060 Search for other works by this author on: GSW Google Scholar Environmental & Engineering Geoscience (2005) 11 (4): 333–346. https://doi.org/10.2113/11.4.333 Article history first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Brian Katz, Rick Copeland, Tom Greenhalgh, Ron Ceryak, Warren Zwanka; Using Multiple Chemical Indicators to Assess Sources of Nitrate and Age of Groundwater in a Karstic Spring Basin. Environmental & Engineering Geoscience 2005;; 11 (4): 333–346. doi: https://doi.org/10.2113/11.4.333 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEnvironmental & Engineering Geoscience Search Advanced Search Abstract Human health and ecological concerns have arisen due to a steady increase in nitrate-N concentrations during the past 40 years in Fannin Springs (0.3–4.7 mg/L), a regional discharge point with an average flow of >2.8 m3/second (>100 ft3/second) for water from the karstic Upper Floridan aquifer (UFA). Multiple chemical indicators (major dissolved species, 15N and 18O of nitrate, dissolved gases, 78 pesticides and degradates, and 67 organic compounds typically found in domestic and industrial wastewater) and transient tracers (3H/3He, chlorofluorocarbons [CFCs], sulfur hexafluoride [SF6]) were analyzed in water samples from nine wells along three transects and in spring water to assess groundwater age and potential contaminant sources. Land use is predominantly agricultural (52 percent) and forest (31 percent) in the 320 km2 (124 mi2) spring basin, which was delineated from a potentiometric-surface map of the UFA using high-resolution water-level data. Nitrate-N concentrations were highly variable in the oxic UFA and ranged from <0.02 to 4.7 mg/L. δ15N-NO3 values (3.4–9.9 per mil) indicated that nitrate contamination originated from inorganic sources (synthetic fertilizer) and organic sources (manure spreading or waste disposal). Higher nitrate concentrations and the younger age of spring water relative to water from upgradient wells indicate better communication with N sources at the surface. Apparent ages of groundwater correlated positively with well depth (P < 0.05) and were younger in water from wells nearer to the spring (<8 years) compared with other wells (10–50 years). Most transient tracer concentrations were consistent with binary mixing curves representing mixtures of water recharged during the past 10 years and older water (recharged before 1940). Young water mixing fractions ranged from 0.07 to 0.90. Trace levels of herbicides found in groundwater and spring water were indicative of applications for vegetative control in agricultural and other land-use types. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.