title: Controls on groundwater nitrogen contributions from on-site wastewater systems in coastal North Carolina.
abstract: The goal of this study was to evaluate the influence of soil type and separation distance to water table on dissolved inorganic nitrogen concentrations in groundwater adjacent to on-site wastewater systems. Groundwater nitrogen species (NO3--N and NH4+-N) and groundwater levels adjacent to 16 on-site systems in three different soil groups (group I- sand, group II- coarse loams and group III -sandy clay loams) were monitored for 15 months (January 2007-March 2008) in coastal North Carolina. On-site systems in soil group I had the highest concentrations of dissolved inorganic nitrogen (median of 18.9 mg/L) in groundwater, and most frequently (mean 61%) exceeded 10 mg/L, followed by systems in soil group II (11.0 mg/L, 50%) and soil group III (2.6 mg/L, 9%), respectively. Groundwater NH4+-N concentrations near on-site systems in soil groups I and II that maintained a 60+cm separation to the seasonal high water table were 4 mg/L lower in relation to systems that had <60 cm separation, but median NO3--N concentrations were 6.5 mg/L higher. On-site systems in group I and II soils are prone to groundwater nitrogen loading with separation distance often controlling the nitrogen speciation in groundwater near on-site systems.
authors.affiliation: Environmental Health Sciences Program, East Carolina University, 3408 Carol Belk Bldg, Greenville, NC 27858-4353, USA. cph0918@ecu.edu
authors.forename: C P
authors.initials: CP
authors.lastname: Humphrey
authors.forename: M A
authors.initials: MA
authors.lastname: O'Driscoll
authors.forename: M A
authors.initials: MA
authors.lastname: Zarate
mesh_terms: D004784:Environmental Monitoring; D005618:Fresh Water / Q000737:chemistry*; D009584:Nitrogen / Q000032:analysis*; D009657:North Carolina; D012987:Soil / Q000032:analysis; D012989:Soil Pollutants / Q000032:analysis*; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis*; D018508:Water Purification / Q000379:methods*; D014881:Water Supply / Q000592:standards
chemical_list: D012987:Soil; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical; D009584:Nitrogen